Update copyright statement

.gitignore

@@ -1,6 +1,5 @@
 # ---> Codex
 .codex
-AGENTS.md
 
 # ---> Go
 # If you prefer the allow list template instead of the deny list, see community template:

.woodpecker/release.yml

@@ -28,10 +28,6 @@ steps:
 
         build_binary linux amd64 ""
         build_binary linux arm64 ""
-        build_binary darwin amd64 ""
-        build_binary darwin arm64 ""
-        build_binary windows amd64 ".exe"
-        build_binary windows arm64 ".exe"
 
   - name: publish-release
     image: woodpeckerci/plugin-release

AGENTS.md

@@ -0,0 +1,4 @@
+Please carefully review the relevant documents in `docs/policy` before making any changes to this repository.
+ - `development.md` defines the contributor workflow for this application.
+ - `architecture.md` provides the canonical high-level architecture policy for this repository, and should be reviewed before writing or changing any code.
+ - `documentation.md` provides the canonical documentation policy for this repository, and should be reviewed before writing or changing any documentation.

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2026 eric. 
+Copyright (c) 2026 Eric Rakestraw. 
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 

README.md

@@ -1,8 +1,12 @@
 # scriptorium
 
-Scriptorium is a config-driven prompt execution engine.
+Scriptorium is a narrow prompt-execution application for rendering prompt
+requests, running them against OpenAI-compatible chat-completions endpoints, and
+serving the same run workflow over HTTP.
 
-It separates prompt definitions (what to generate) from execution profiles (how to call an OpenAI-compatible model endpoint), then runs or renders a prepared request from named input artifacts.
+It keeps prompt definitions, execution profiles, schemas, and input artifacts as
+separate files so prompts can be reviewed and reused without baking model
+runtime settings into application code.
 
 ## Quickstart
 
@@ -23,14 +27,19 @@ This command renders the prepared prompt and effective runtime settings without
 
 - [CLI reference](docs/cli.md)
 - [Configuration reference](docs/config.md)
+- [HTTP API reference](docs/api.md)
 - [Operations guide](docs/operations.md)
 - [Troubleshooting](docs/troubleshooting.md)
-- [HTTP API integration](docs/integrations/http-api.md)
+- [Consumer integration overview](docs/consumers/api.md)
+- [Go library package](docs/consumers/pkg-scriptorium.md)
+- [Subprocess integration](docs/integrations/subprocess.md)
 - [OpenAI-compatible chat integration](docs/integrations/openai-compatible-chat.md)
-- [Narratio subprocess integration](docs/integrations/narratio.md)
 - [Architecture policy](docs/policy/architecture.md)
 
 ## Examples
 
+- `examples/config.yml`
+- `examples/config.full.yml`
 - `examples/render-markdown-summary.sh`
 - `examples/http-run.json`
+- `examples/go-library/prepare`

convert.go

@@ -0,0 +1,406 @@
+package scriptorium
+
+import (
+	"reflect"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+)
+
+func toDomainRunRequest(req RunRequest) (domain.RunRequest, error) {
+	execution, err := toDomainExecutionTargetOverride(req.Execution)
+	if err != nil {
+		return domain.RunRequest{}, err
+	}
+	return domain.RunRequest{
+		PromptID:      req.PromptID,
+		PromptVersion: req.PromptVersion,
+		ProfileID:     req.ProfileID,
+		APIKey:        req.APIKey,
+		Inputs:        toDomainArtifactRefMap(req.Inputs),
+		Vars:          copyStringMap(req.Vars),
+		Execution:     execution,
+		Validation:    toDomainOutputContractPtr(req.Validation),
+		Metadata:      copyStringMap(req.Metadata),
+	}, nil
+}
+
+func fromDomainPreparedRun(prepared *domain.PreparedRun) *PreparedRun {
+	if prepared == nil {
+		return nil
+	}
+	return &PreparedRun{
+		PromptID:             prepared.PromptID,
+		PromptVersion:        prepared.PromptVersion,
+		PromptHash:           prepared.PromptHash,
+		SelectedProfileID:    prepared.SelectedProfileID,
+		EffectiveModelParams: fromDomainExecutionTarget(prepared.EffectiveModelParams),
+		OutputContract:       fromDomainOutputContract(prepared.OutputContract),
+		StructuredOutput:     fromDomainStructuredOutputSpec(prepared.StructuredOutput),
+		InputHashes:          copyStringMap(prepared.InputHashes),
+		SessionID:            prepared.SessionID,
+		RenderedPromptHash:   prepared.RenderedPromptHash,
+		Messages:             fromDomainRenderedMessages(prepared.Messages),
+		StartTime:            prepared.StartTime,
+		EndTime:              prepared.EndTime,
+		DurationMS:           prepared.DurationMS,
+	}
+}
+
+func fromDomainRunResult(result *domain.RunResult) *RunResult {
+	if result == nil {
+		return nil
+	}
+	return &RunResult{
+		RunID:                result.RunID,
+		Artifact:             fromDomainArtifact(result.Artifact),
+		RawOutput:            result.RawOutput,
+		Validation:           fromDomainValidationResult(result.Validation),
+		PromptID:             result.PromptID,
+		PromptVersion:        result.PromptVersion,
+		PromptHash:           result.PromptHash,
+		RenderedPromptHash:   result.RenderedPromptHash,
+		SelectedProfileID:    result.SelectedProfileID,
+		ModelName:            result.ModelName,
+		Endpoint:             result.Endpoint,
+		EffectiveModelParams: fromDomainExecutionTarget(result.EffectiveModelParams),
+		InputHashes:          copyStringMap(result.InputHashes),
+		Usage:                fromDomainTokenUsage(result.Usage),
+		StartTime:            result.StartTime,
+		EndTime:              result.EndTime,
+		Duration:             result.Duration,
+	}
+}
+
+func fromDomainGenerateRequest(req domain.GenerateRequest) GenerateRequest {
+	return GenerateRequest{
+		Prompt:           fromDomainRenderedPrompt(req.Prompt),
+		Target:           fromDomainExecutionTarget(req.Target),
+		TargetPresence:   fromDomainExecutionTargetPresence(req.TargetPresence),
+		StructuredOutput: fromDomainStructuredOutputSpec(req.StructuredOutput),
+		APIKey:           req.Target.APIKey,
+	}
+}
+
+func toDomainGenerateResponse(resp *GenerateResponse) *domain.GenerateResponse {
+	if resp == nil {
+		return nil
+	}
+	return &domain.GenerateResponse{
+		Content: resp.Content,
+		Usage:   toDomainTokenUsage(resp.Usage),
+	}
+}
+
+func fromDomainRenderedPrompt(prompt domain.RenderedPrompt) RenderedPrompt {
+	return RenderedPrompt{
+		SessionID: prompt.SessionID,
+		Messages:  fromDomainRenderedMessages(prompt.Messages),
+	}
+}
+
+func toDomainArtifactRefMap(src map[string]ArtifactRef) map[string]domain.ArtifactRef {
+	if src == nil {
+		return nil
+	}
+	out := make(map[string]domain.ArtifactRef, len(src))
+	for k, v := range src {
+		out[k] = toDomainArtifactRef(v)
+	}
+	return out
+}
+
+func toDomainArtifactRef(ref ArtifactRef) domain.ArtifactRef {
+	return domain.ArtifactRef{
+		Type: domain.ArtifactRefType(ref.Type),
+		URI:  ref.URI,
+		Body: ref.Body,
+	}
+}
+
+func fromDomainArtifact(artifact domain.Artifact) Artifact {
+	return Artifact{
+		Name:        artifact.Name,
+		ContentType: artifact.ContentType,
+		Body:        copyBytes(artifact.Body),
+		URI:         artifact.URI,
+		Size:        artifact.Size,
+		Hash:        artifact.Hash,
+	}
+}
+
+func toDomainExecutionTargetOverride(override *ExecutionTargetOverride) (*domain.ExecutionTargetOverride, error) {
+	if override == nil {
+		return nil, nil
+	}
+	extraParams, err := copyPublicJSONMap(override.ExtraParams)
+	if err != nil {
+		return nil, err
+	}
+	return &domain.ExecutionTargetOverride{
+		Endpoint:        override.Endpoint,
+		Model:           override.Model,
+		Temperature:     copyFloat64Ptr(override.Temperature),
+		MaxTokens:       copyIntPtr(override.MaxTokens),
+		TopP:            copyFloat64Ptr(override.TopP),
+		TimeoutSeconds:  copyIntPtr(override.TimeoutSeconds),
+		ServiceTier:     override.ServiceTier,
+		ReasoningEffort: override.ReasoningEffort,
+		APIKeyEnv:       override.APIKeyEnv,
+		ExtraParams:     extraParams,
+	}, nil
+}
+
+func fromDomainExecutionTarget(target domain.ExecutionTarget) ExecutionTarget {
+	return ExecutionTarget{
+		Endpoint:        target.Endpoint,
+		Model:           target.Model,
+		Temperature:     target.Temperature,
+		MaxTokens:       target.MaxTokens,
+		TopP:            target.TopP,
+		TimeoutSeconds:  target.TimeoutSeconds,
+		ServiceTier:     target.ServiceTier,
+		ReasoningEffort: target.ReasoningEffort,
+		APIKeyEnv:       target.APIKeyEnv,
+		ExtraParams:     copyAnyMap(target.ExtraParams),
+	}
+}
+
+func fromDomainExecutionTargetPresence(presence domain.ExecutionTargetPresence) ExecutionTargetPresence {
+	return ExecutionTargetPresence{
+		Temperature:    presence.Temperature,
+		MaxTokens:      presence.MaxTokens,
+		TopP:           presence.TopP,
+		TimeoutSeconds: presence.TimeoutSeconds,
+	}
+}
+
+func toDomainOutputContractPtr(contract *OutputContract) *domain.OutputContract {
+	if contract == nil {
+		return nil
+	}
+	out := toDomainOutputContract(*contract)
+	return &out
+}
+
+func toDomainOutputContract(contract OutputContract) domain.OutputContract {
+	return domain.OutputContract{
+		Format:         domain.OutputFormat(contract.Format),
+		ValidationMode: domain.ValidationMode(contract.ValidationMode),
+		SchemaPath:     contract.SchemaPath,
+		RepairAttempts: contract.RepairAttempts,
+	}
+}
+
+func fromDomainOutputContract(contract domain.OutputContract) OutputContract {
+	return OutputContract{
+		Format:         OutputFormat(contract.Format),
+		ValidationMode: ValidationMode(contract.ValidationMode),
+		SchemaPath:     contract.SchemaPath,
+		RepairAttempts: contract.RepairAttempts,
+	}
+}
+
+func fromDomainValidationResult(result domain.ValidationResult) ValidationResult {
+	return ValidationResult{
+		Status:         ValidationStatus(result.Status),
+		Mode:           ValidationMode(result.Mode),
+		Errors:         copyStringSlice(result.Errors),
+		SchemaPath:     result.SchemaPath,
+		RepairAttempts: result.RepairAttempts,
+		IsValid:        result.IsValid,
+	}
+}
+
+func fromDomainTokenUsage(usage domain.TokenUsage) TokenUsage {
+	return TokenUsage{
+		PromptTokens:     usage.PromptTokens,
+		CompletionTokens: usage.CompletionTokens,
+		TotalTokens:      usage.TotalTokens,
+		CachedTokens:     usage.CachedTokens,
+		CacheWriteTokens: usage.CacheWriteTokens,
+	}
+}
+
+func toDomainTokenUsage(usage TokenUsage) domain.TokenUsage {
+	return domain.TokenUsage{
+		PromptTokens:     usage.PromptTokens,
+		CompletionTokens: usage.CompletionTokens,
+		TotalTokens:      usage.TotalTokens,
+		CachedTokens:     usage.CachedTokens,
+		CacheWriteTokens: usage.CacheWriteTokens,
+	}
+}
+
+func fromDomainRenderedMessages(messages []domain.RenderedMessage) []RenderedMessage {
+	if messages == nil {
+		return nil
+	}
+	out := make([]RenderedMessage, len(messages))
+	for i, msg := range messages {
+		out[i] = RenderedMessage{
+			Role:         msg.Role,
+			Content:      msg.Content,
+			CacheControl: fromDomainCacheControl(msg.CacheControl),
+		}
+	}
+	return out
+}
+
+func fromDomainCacheControl(cacheControl *domain.CacheControl) *CacheControl {
+	if cacheControl == nil {
+		return nil
+	}
+	return &CacheControl{
+		Type: CacheControlType(cacheControl.Type),
+		TTL:  cacheControl.TTL,
+	}
+}
+
+func fromDomainStructuredOutputSpec(spec *domain.StructuredOutputSpec) *StructuredOutputSpec {
+	if spec == nil {
+		return nil
+	}
+	out := &StructuredOutputSpec{
+		Type: StructuredOutputType(spec.Type),
+	}
+	if spec.JSONSchema != nil {
+		out.JSONSchema = &StructuredOutputJSONSpec{
+			Name:   spec.JSONSchema.Name,
+			Strict: spec.JSONSchema.Strict,
+			Schema: copyAny(spec.JSONSchema.Schema),
+		}
+	}
+	return out
+}
+
+func copyStringMap(src map[string]string) map[string]string {
+	if src == nil {
+		return nil
+	}
+	out := make(map[string]string, len(src))
+	for k, v := range src {
+		out[k] = v
+	}
+	return out
+}
+
+func copyAnyMap(src map[string]any) map[string]any {
+	if src == nil {
+		return nil
+	}
+	out := make(map[string]any, len(src))
+	for k, v := range src {
+		out[k] = copyAny(v)
+	}
+	return out
+}
+
+func copyAny(value any) any {
+	if value == nil {
+		return nil
+	}
+	switch v := value.(type) {
+	case map[string]any:
+		return copyAnyMap(v)
+	case []any:
+		out := make([]any, len(v))
+		for i, item := range v {
+			out[i] = copyAny(item)
+		}
+		return out
+	case []string:
+		return copyStringSlice(v)
+	case []byte:
+		return copyBytes(v)
+	default:
+		return copyReflectValue(reflect.ValueOf(value)).Interface()
+	}
+}
+
+func copyReflectValue(value reflect.Value) reflect.Value {
+	if !value.IsValid() {
+		return value
+	}
+
+	switch value.Kind() {
+	case reflect.Interface:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		copied := copyReflectValue(value.Elem())
+		if copied.IsValid() && copied.Type().AssignableTo(value.Type()) {
+			return copied
+		}
+		out := reflect.New(value.Type()).Elem()
+		out.Set(copied)
+		return out
+	case reflect.Pointer:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.New(value.Type().Elem())
+		out.Elem().Set(copyReflectValue(value.Elem()))
+		return out
+	case reflect.Map:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.MakeMapWithSize(value.Type(), value.Len())
+		iter := value.MapRange()
+		for iter.Next() {
+			out.SetMapIndex(copyReflectValue(iter.Key()), copyReflectValue(iter.Value()))
+		}
+		return out
+	case reflect.Slice:
+		if value.IsNil() {
+			return reflect.Zero(value.Type())
+		}
+		out := reflect.MakeSlice(value.Type(), value.Len(), value.Cap())
+		for i := 0; i < value.Len(); i++ {
+			out.Index(i).Set(copyReflectValue(value.Index(i)))
+		}
+		return out
+	case reflect.Array:
+		out := reflect.New(value.Type()).Elem()
+		for i := 0; i < value.Len(); i++ {
+			out.Index(i).Set(copyReflectValue(value.Index(i)))
+		}
+		return out
+	default:
+		return value
+	}
+}
+
+func copyStringSlice(src []string) []string {
+	if src == nil {
+		return nil
+	}
+	out := make([]string, len(src))
+	copy(out, src)
+	return out
+}
+
+func copyBytes(src []byte) []byte {
+	if src == nil {
+		return nil
+	}
+	out := make([]byte, len(src))
+	copy(out, src)
+	return out
+}
+
+func copyFloat64Ptr(src *float64) *float64 {
+	if src == nil {
+		return nil
+	}
+	v := *src
+	return &v
+}
+
+func copyIntPtr(src *int) *int {
+	if src == nil {
+		return nil
+	}
+	v := *src
+	return &v
+}

docs/api.md

@@ -0,0 +1,297 @@
+# HTTP API Reference
+
+This is the canonical public HTTP contract for Scriptorium.
+
+Implemented route:
+
+- `POST /v1/runs`
+
+For CLI behavior, see [CLI reference](cli.md). For config and prompt/profile
+file formats, see [Configuration reference](config.md).
+
+The maintained request-shape example is `examples/http-run.json`. It requires a
+running `serve` process with an artifact root that can read the referenced
+files, plus a reachable model endpoint for full execution.
+
+## Base URL And Deployment
+
+`scriptorium serve` listens on `server.addr` or `serve --addr`. The default is
+`:8080`.
+
+The route path is always:
+
+```text
+/v1/runs
+```
+
+The HTTP adapter has no built-in authentication or authorization. Deploy it
+behind trusted network and authentication controls.
+
+## Media Types
+
+- Request body: JSON object.
+- Response body: JSON object.
+- Response `Content-Type`: `application/json`.
+
+Requests are decoded as JSON regardless of the request `Content-Type` header.
+There are no shared query parameters.
+
+## Request Limits
+
+HTTP limits are configured through `server.*` config fields or `serve` flags:
+
+- `server.max_request_bytes`: encoded JSON request body limit, including inline input bodies.
+- `server.max_artifact_bytes`: file artifact limit for HTTP `file` input references.
+- `server.max_response_bytes`: encoded JSON response limit, including artifact body and optional raw output.
+
+Each limit defaults to `16777216` bytes. `0` disables that limit.
+
+## `POST /v1/runs`
+
+Runs one prompt request and returns the generated artifact, validation result,
+and metadata.
+
+### Request Body
+
+```json
+{
+  "prompt_id": "generic.markdown_summary",
+  "profile_id": "local-fast",
+  "prompt_version": "1.0.0",
+  "inputs": {
+    "transcript": {
+      "type": "file",
+      "uri": "./examples/fixtures/transcript.md"
+    },
+    "glossary": {
+      "type": "inline",
+      "body": "party:\n  - Rin"
+    }
+  },
+  "vars": {
+    "session_date": "2026-05-04"
+  },
+  "model": {
+    "endpoint": "http://localhost:8000/v1",
+    "model": "gpt-4o-mini",
+    "temperature": 0,
+    "max_tokens": 800,
+    "top_p": 1,
+    "timeout_seconds": 120,
+    "service_tier": "priority",
+    "reasoning_effort": "medium",
+    "api_key_env": "SCRIPTORIUM_API_KEY",
+    "extra_params": {
+      "provider_option": "enabled"
+    }
+  },
+  "include_raw_output": false
+}
+```
+
+Request fields:
+
+| Field | Required | Description |
+| --- | --- | --- |
+| `prompt_id` | yes | Prompt ID. Must not be blank. |
+| `prompt_version` | no | Prompt version filter. |
+| `profile_id` | no | Execution profile ID. If omitted, the prompt must define `default_profile`. |
+| `inputs` | yes | Object mapping prompt input names to input references. Must contain at least one entry. |
+| `vars` | no | Object mapping template variable names to string values. |
+| `model` | no | Runtime model override object. |
+| `include_raw_output` | no | When `true`, include `raw_model_output` in the response. |
+
+Input reference fields:
+
+| Field | Required | Description |
+| --- | --- | --- |
+| `type` | yes | `file` or `inline`. |
+| `uri` | for `file` | File URI/path. |
+| `body` | for `inline` | Inline artifact body. |
+
+HTTP `file` references require `server.artifact_root` or `serve
+--artifact-root`. Relative file URIs resolve against that root. Absolute file
+URIs are accepted only when lexically inside the root. Relative traversal and
+absolute paths outside the root return `400 artifact_not_allowed`.
+
+The containment check is lexical and does not resolve symlinks. Symlinks inside
+the artifact root are followed by the operating system, including symlinks that
+point outside the root. Keep the artifact root narrow and not writable by
+untrusted users.
+
+Model override fields:
+
+| Field | Description |
+| --- | --- |
+| `endpoint` | Runtime endpoint override. |
+| `model` | Runtime model override. |
+| `temperature` | Number in range `0..2`. Explicit `0` is an override. |
+| `max_tokens` | Integer greater than or equal to `0`. Explicit `0` is an override. |
+| `top_p` | Number in range `0..1`. Explicit `0` is an override. |
+| `timeout_seconds` | Integer greater than or equal to `0`. Explicit `0` disables the outbound client timeout. |
+| `service_tier` | Provider-specific request tier. |
+| `reasoning_effort` | Provider-specific reasoning setting. |
+| `api_key_env` | Name of an environment variable containing the API key. |
+| `extra_params` | JSON-compatible provider-specific top-level request fields. |
+
+Raw API-key values are not accepted in HTTP payloads. A field such as
+`api_key` is rejected as unknown JSON.
+
+`extra_params` keys must not be empty and must not collide with reserved
+outbound fields: `model`, `session_id`, `messages`, `temperature`,
+`max_tokens`, `top_p`, `service_tier`, `reasoning_effort`, or
+`response_format`.
+
+### Strict JSON Rules
+
+Request decoding is strict:
+
+- malformed JSON returns `400 invalid_json`
+- unknown request fields return `400 invalid_json`
+- unknown `inputs` item fields return `400 invalid_json`
+- unknown `model` fields return `400 invalid_json`
+- trailing JSON tokens after the request object return `400 invalid_json`
+- request bodies above the configured limit return `413 request_too_large`
+
+### Success Response
+
+Status: `200 OK`
+
+```json
+{
+  "artifact": {
+    "name": "output",
+    "content_type": "text/markdown",
+    "body": "Generated content",
+    "size": 17,
+    "hash": "..."
+  },
+  "validation": {
+    "status": "passed",
+    "mode": "basic",
+    "repair_attempts": 0,
+    "is_valid": true
+  },
+  "metadata": {
+    "run_id": "...",
+    "prompt_id": "generic.markdown_summary",
+    "prompt_version": "1.0.0",
+    "prompt_hash": "...",
+    "rendered_prompt_hash": "...",
+    "selected_profile_id": "local-fast",
+    "model_name": "gpt-4o-mini",
+    "endpoint": "http://localhost:8000/v1",
+    "model_params": {
+      "endpoint": "http://localhost:8000/v1",
+      "model": "gpt-4o-mini",
+      "temperature": 0.2,
+      "max_tokens": 500,
+      "top_p": 1,
+      "timeout_seconds": 90
+    },
+    "input_hashes": {
+      "transcript": "..."
+    },
+    "usage": {
+      "prompt_tokens": 11,
+      "completion_tokens": 22,
+      "total_tokens": 33,
+      "cached_tokens": 0,
+      "cache_write_tokens": 0
+    },
+    "start_time": "2026-05-04T12:00:00Z",
+    "end_time": "2026-05-04T12:00:01Z",
+    "duration_ms": 1000,
+    "validation_mode": "basic",
+    "validation_status": "passed",
+    "repair_attempts_used": 0
+  }
+}
+```
+
+Response fields:
+
+- `artifact`: generated output artifact.
+- `validation`: validation result for the generated artifact.
+- `metadata`: run and effective runtime metadata.
+- `raw_model_output`: omitted unless `include_raw_output` is `true`.
+
+`artifact.uri` is omitted when empty. `validation.errors` and
+`validation.schema_path` are omitted when empty. `model_params.service_tier`,
+`model_params.reasoning_effort`, `model_params.api_key_env`, and
+`model_params.extra_params` are omitted when empty.
+
+`metadata.usage.cached_tokens` and `metadata.usage.cache_write_tokens` are
+always present as numbers. They are `0` when the provider omits compatible cache
+usage fields or reports no cache activity.
+
+### Validation Failure Response
+
+Generated-content validation failures still return `200 OK`.
+
+```json
+{
+  "validation": {
+    "status": "failed",
+    "mode": "json",
+    "errors": ["invalid JSON: ..."],
+    "repair_attempts": 0,
+    "is_valid": false
+  }
+}
+```
+
+The response still includes `artifact` and `metadata`.
+
+## Error Responses
+
+Error body shape:
+
+```json
+{
+  "error": {
+    "code": "invalid_request",
+    "message": "prompt_id is required"
+  }
+}
+```
+
+Current status/code mapping:
+
+| Status | Code | Meaning |
+| --- | --- | --- |
+| `400` | `invalid_json` | Malformed JSON, unknown JSON field, or trailing JSON token. |
+| `400` | `invalid_request` | Missing/invalid request fields or invalid runtime overrides. |
+| `400` | `profile_required` | No `profile_id` and prompt has no `default_profile`. |
+| `400` | `prompt_load_failed` | Prompt definition YAML/contract failed to load. |
+| `400` | `profile_load_failed` | Profile YAML/contract failed to load, including raw `api_key`. |
+| `400` | `artifact_not_allowed` | HTTP file refs are disabled or requested path is outside artifact root. |
+| `400` | `artifact_read_failed` | Input artifact could not be read or input ref was unsupported/invalid. |
+| `400` | `prompt_render_failed` | Prompt template rendering failed. |
+| `400` | `api_key_env_missing` | Selected `api_key_env` variable is unset or empty. |
+| `404` | `not_found` | Route path is unknown. |
+| `404` | `prompt_not_found` | Prompt ID/version was not found. |
+| `404` | `profile_not_found` | Profile ID was not found. |
+| `405` | `method_not_allowed` | Method is not `POST` on `/v1/runs`. |
+| `413` | `request_too_large` | Encoded JSON request body exceeds configured request limit. |
+| `413` | `artifact_too_large` | HTTP file input artifact exceeds configured artifact limit. |
+| `413` | `response_too_large` | Encoded JSON response exceeds configured response limit. |
+| `500` | `validation_runtime_failed` | Validator runtime/schema loading failed. |
+| `500` | `internal_error` | Unclassified server error. |
+| `502` | `llm_failed` | Outbound model request failed. |
+
+HTTP error messages are intentionally concise and do not include sensitive
+internal causes.
+
+## Retry And Idempotency
+
+Scriptorium does not provide idempotency keys, pagination, caching headers, or
+rate limiting.
+
+Clients may retry transport failures or `5xx` responses when their surrounding
+workflow can tolerate another model call. A retry can generate different output
+and incur another provider request.
+
+## Example File
+
+- `examples/http-run.json`

docs/cli.md

@@ -10,110 +10,195 @@ go run ./cmd/scriptorium render \
   --input glossary=./examples/fixtures/glossary.yml
 ```
 
-`render` prepares and formats the prompt without calling an LLM.
+`render` prepares the prompt, loads input artifacts, resolves the execution
+profile, and prints the prepared request without calling an LLM.
 
 ## Command Overview
 
-- `scriptorium run`: prepare prompt, call the configured LLM, write generated output, print a run summary.
+- `scriptorium run`: prepare a prompt, call the configured LLM, write generated output, and print a run summary.
-- `scriptorium render`: prepare prompt only; write prepared-run output as `text` or `json`.
+- `scriptorium render`: prepare a prompt only; write prepared-run output as `text` or `json`.
-- `scriptorium serve`: start the HTTP server.
+- `scriptorium serve`: start the HTTP server for `POST /v1/runs`.
 
-Integration references:
+Canonical related references:
 
-- [HTTP contract](integrations/http-api.md)
+- [Configuration reference](config.md)
-- [Narratio subprocess contract](integrations/narratio.md)
+- [HTTP API reference](api.md)
+- [Subprocess integration](integrations/subprocess.md)
 
-## Common Argument Rules
+## Common Rules
 
 - `--config` is supported by `run`, `render`, and `serve`.
-- `run` and `render` require:
-  - `--prompt`
-  - at least one `--input`
-  - an effective `prompt_dir` and `profile_dir` (from flags or config)
-- `serve` requires an effective `prompt_dir` and `profile_dir` (from flags or config).
 - Positional arguments are rejected.
+- `run` and `render` require `--prompt`, at least one `--input`, and an effective `prompt_dir`.
+- `serve` requires an effective `prompt_dir`.
+- `profile_dir` is optional. Without it, only built-in profiles are available.
+- If `profile_dir` is set, custom profiles override built-in profiles with the same ID.
+- Prompt cache control, `session_id`, structured output, and provider-specific profile fields are configured in YAML, not with CLI flags.
+
+Config precedence is:
+
+1. built-in defaults
+2. config file values
+3. CLI flags
 
 ## Flag Reference
 
 ### `scriptorium run`
 
-- `--config <path>`: app config file path.
+```bash
+scriptorium run [flags]
+```
+
+Required through flags or config:
+
 - `--prompt-dir <dir>`: prompt definition directory.
-- `--profile-dir <dir>`: profile definition directory.
+
+Required as flags:
+
+- `--prompt <id>`: prompt ID to execute.
+- `--input name=path`: input file mapping. Repeat or use comma-separated mappings.
+
+Optional flags:
+
+- `--config <path>`: application config file.
+- `--profile-dir <dir>`: custom profile definition directory.
 - `--schema-dir <dir>`: schema base directory for `json_schema` validation.
-- `--prompt <id>`: prompt ID to execute. Required.
+- `--profile <id>`: execution profile override. If omitted, the prompt `default_profile` is used.
-- `--prompt-id <id>`: deprecated alias for `--prompt`.
+- `--var name=value`: template variable mapping. Repeat or use comma-separated mappings.
-- `--profile <id>`: explicit profile override.
+- `--out <path>`: write generated artifact body to a file instead of stdout.
-- `--profile-id <id>`: deprecated alias for `--profile`.
-- `--input name=path`: input mapping (repeatable, comma-separated accepted).
-- `--var name=value`: template variable mapping (repeatable, comma-separated accepted).
-- `--out <path>`: write artifact body to file instead of stdout.
 - `--llm-base-url <url>`: runtime endpoint override.
 - `--model <name>`: runtime model override.
-- `--api-key-env <name>`: runtime API key environment-variable name override.
+- `--api-key-env <name>`: runtime API-key environment variable name override.
 - `--temperature <float>`: runtime temperature override.
 - `--max-tokens <int>`: runtime max tokens override.
 - `--top-p <float>`: runtime top-p override.
-- `--timeout <duration>`: runtime timeout override (Go duration syntax, for example `30s`, `2m`).
+- `--timeout <duration>`: runtime timeout override using Go duration syntax, such as `30s` or `2m`.
+
+Deprecated aliases:
+
+- `--prompt-id <id>`: alias for `--prompt`.
+- `--profile-id <id>`: alias for `--profile`.
+
+Runtime override notes:
+
+- Omitted numeric override flags preserve the selected profile/default value.
+- Explicit zero values override the selected profile/default value.
+- `--timeout 0s` disables the outbound HTTP client timeout for that request.
+- There is no raw API-key flag; use `--api-key-env`.
 
 ### `scriptorium render`
 
-- Supports the same flags as `run`, except:
+```bash
-  - no `--schema-dir` flag.
+scriptorium render [flags]
-- Adds:
+```
-  - `--format text|json`: prepared-run output format.
+
+Required through flags or config:
+
+- `--prompt-dir <dir>`: prompt definition directory.
+
+Required as flags:
+
+- `--prompt <id>`: prompt ID to render.
+- `--input name=path`: input file mapping. Repeat or use comma-separated mappings.
+
+Optional flags:
+
+- `--config <path>`: application config file.
+- `--prompt-dir <dir>`: prompt definition directory.
+- `--profile-dir <dir>`: custom profile definition directory.
+- `--profile <id>`: execution profile override.
+- `--var name=value`: template variable mapping. Repeat or use comma-separated mappings.
+- `--out <path>`: write prepared-run output to a file instead of stdout.
+- `--llm-base-url <url>`: runtime endpoint override for the prepared request.
+- `--model <name>`: runtime model override for the prepared request.
+- `--api-key-env <name>`: runtime API-key environment variable name override.
+- `--temperature <float>`: runtime temperature override.
+- `--max-tokens <int>`: runtime max tokens override.
+- `--top-p <float>`: runtime top-p override.
+- `--timeout <duration>`: runtime timeout override using Go duration syntax.
+- `--format text|json`: prepared-run output format. Defaults to config `defaults.render_format`, then `text`.
+
+Deprecated aliases:
+
+- `--prompt-id <id>`: alias for `--prompt`.
+- `--profile-id <id>`: alias for `--profile`.
 
 Notes:
-- `render` still resolves profile and runtime settings.
+
-- `render` still validates that `api_key_env` exists if the selected profile or overrides require it.
+- `render` resolves profiles, loads schemas for `json_schema` prompts, and validates `api_key_env`.
+- `render` does not accept `--schema-dir`; use config `schema_dir` for render-time schema lookup.
+- `render` does not call the LLM.
 
 ### `scriptorium serve`
 
-- `--config <path>`: app config file path.
+```bash
+scriptorium serve [flags]
+```
+
+Required through flags or config:
+
+- `--prompt-dir <dir>`: prompt definition directory.
+
+Optional flags:
+
+- `--config <path>`: application config file.
 - `--addr <listen-address>`: HTTP listen address.
 - `--prompt-dir <dir>`: prompt definition directory.
-- `--profile-dir <dir>`: profile definition directory.
+- `--profile-dir <dir>`: custom profile definition directory.
 - `--schema-dir <dir>`: schema base directory for `json_schema` validation.
+- `--artifact-root <dir>`: base directory for HTTP `file` input references.
+- `--max-request-bytes <n>`: maximum HTTP request body bytes; `0` disables the limit.
+- `--max-artifact-bytes <n>`: maximum HTTP file artifact bytes; `0` disables the limit.
+- `--max-response-bytes <n>`: maximum encoded HTTP response body bytes; `0` disables the limit.
 
 Notes:
+
 - `serve` does not accept runtime model override flags such as `--model` or `--llm-base-url`.
+- HTTP request fields and error codes are documented in the [HTTP API reference](api.md).
+- HTTP `file` input references are rejected unless an artifact root is configured.
+- HTTP size-limit flags affect only `serve`.
 
 ## Input And Variable Syntax
 
 - `--input name=path` maps prompt input names to local file paths.
-- `--var name=value` maps template variable names to values.
+- `--var name=value` maps prompt template variables to string values.
 - Both flags can be repeated.
-- Both flags also support comma-separated batches, for example:
+- Both flags also accept comma-separated mappings, such as `--input transcript=./t.md,glossary=./g.yml`.
-  - `--input transcript=./t.md,glossary=./g.yml`
+- Values may contain `=` after the first separator, such as `--var note=a=b=c`.
-  - `--var session_id=42,session_date=2026-05-04`
+- Empty names and empty values are rejected.
+
+CLI `run` and `render` convert every `--input` mapping to a `file` artifact
+reference. HTTP also supports `inline` input references; see [HTTP API
+reference](api.md).
 
 ## Output Behavior
 
 `run`:
+
 - Writes generated artifact content to stdout by default.
 - Writes generated artifact content to `--out` when provided.
-- Prints run summary metadata to stderr on success.
+- Prints a success summary to stderr.
 - Prints errors to stderr on failure.
 
 `render`:
+
 - Writes prepared-run output to stdout by default.
 - Writes prepared-run output to `--out` when provided.
-- Does not print a success summary line.
+- Does not print a success summary.
 
 `serve`:
+
 - Logs startup and server errors to stderr.
 
 ## Exit Codes
 
 - `0`: success.
-- `1`: runtime/parse/config/load/render/generation/output-write error.
+- `1`: parse, config, load, render, generation, output-write, or runtime error.
-- `2`: `run` completed, output was generated, but validation status is `failed`.
+- `2`: `run` completed and wrote output, but validation status is `failed`.
-
-When `run` exits `2`, output may already be written to stdout or `--out`.
 
 ## Common Workflows
 
-Render prompt inputs and template variables as JSON:
+Render prompt inputs and variables as JSON:
 
 ```bash
 go run ./cmd/scriptorium render \
@@ -125,7 +210,7 @@ go run ./cmd/scriptorium render \
   --format json
 ```
 
-Run a prompt with profile override and file output:
+Run a prompt with an explicit profile and file output:
 
 ```bash
 go run ./cmd/scriptorium run \
@@ -137,12 +222,12 @@ go run ./cmd/scriptorium run \
   --out ./summary.md
 ```
 
-Start the HTTP server with explicit config:
+Start the HTTP server with example config:
 
 ```bash
 go run ./cmd/scriptorium serve --config ./examples/config.yml
 ```
 
-Copyable example script:
+Copyable maintained script:
 
 - `examples/render-markdown-summary.sh`

docs/config.md

@@ -2,31 +2,32 @@
 
 ## Config Discovery And Precedence
 
-Application settings are loaded in this order:
+Application settings are resolved in this order:
 
-1. Built-in defaults
+1. built-in defaults
 2. `config.yml` values
 3. CLI overrides
 
-When `--config` is not provided, Scriptorium searches for config files in this order:
+When `--config` is omitted, Scriptorium searches:
 
 1. `/usr/local/etc/scriptorium/config.yml`
 2. `/etc/scriptorium/config.yml`
 
-If neither file exists, Scriptorium continues with built-in defaults.
+If neither file exists, Scriptorium uses built-in defaults. When
+`--config <path>` is provided, that file must exist and decode successfully.
 
-When `--config <path>` is provided, that file is required.
+## Minimal Working Config
-
-## Minimal App Config
 
 ```yaml
 prompt_dir: ./examples/prompts
-profile_dir: ./examples/profiles
 ```
 
-This is enough to use `run` and `render` when prompt/profile files are valid.
+This is enough for `run` and `render` when selected prompts use built-in
+profiles. Set `profile_dir` when prompts or requests use custom profiles.
 
-## Production-Oriented App Config
+The maintained repository example is `examples/config.yml`.
+
+## Production-Oriented Config
 
 ```yaml
 prompt_dir: /opt/scriptorium/prompts
@@ -35,37 +36,57 @@ schema_dir: /opt/scriptorium/schemas
 
 server:
   addr: 127.0.0.1:8080
+  artifact_root: /var/lib/scriptorium/artifacts
+  max_request_bytes: 16777216
+  max_artifact_bytes: 16777216
+  max_response_bytes: 16777216
 
 defaults:
   render_format: text
 ```
 
-## App Config File (`config.yml`)
+The maintained full example is `examples/config.full.yml`.
+
+## App Config Reference
 
 Top-level fields:
 
-- `prompt_dir` (optional): default prompt definition directory.
+| Field | Default | Description |
-- `profile_dir` (optional): default profile definition directory.
+| --- | --- | --- |
-- `schema_dir` (optional): base directory for schema files used by `json_schema` validation.
+| `prompt_dir` | unset | Directory containing prompt definition YAML files. Required effectively by `run`, `render`, and `serve`. |
-- `server.addr` (optional): default listen address for `serve`.
+| `profile_dir` | unset | Directory containing custom profile YAML files. Built-in profiles remain available when unset. |
-- `defaults.render_format` (optional): default `render` output format (`text` or `json`).
+| `schema_dir` | `.` | Base directory for relative JSON Schema paths. |
+| `server` | `{}` | HTTP service settings used by `serve`. |
+| `defaults` | `{}` | Adapter defaults. |
 
-Built-in defaults:
+`server` fields:
 
-- `schema_dir`: `.`
+| Field | Default | Description |
-- `server.addr`: `:8080`
+| --- | --- | --- |
-- `defaults.render_format`: `text`
+| `server.addr` | `:8080` | Listen address for `serve`. |
+| `server.artifact_root` | unset | Base directory for HTTP `file` input references. Without it, HTTP file refs are rejected. |
+| `server.max_request_bytes` | `16777216` | Maximum encoded HTTP request body bytes. `0` disables the limit. |
+| `server.max_artifact_bytes` | `16777216` | Maximum HTTP file artifact bytes. `0` disables the limit. |
+| `server.max_response_bytes` | `16777216` | Maximum encoded HTTP response bytes. `0` disables the limit. |
 
-Validation behavior:
+`defaults` fields:
 
-- Config decoding is strict; unknown YAML fields are rejected.
+| Field | Default | Description |
-- Raw API key fields are not supported in `config.yml`.
+| --- | --- | --- |
+| `defaults.render_format` | `text` | Default `render` output format: `text` or `json`. |
+
+Config rules:
+
+- YAML decoding is strict; unknown fields are rejected.
+- HTTP size limits must be greater than or equal to `0`.
+- Empty string config values are ignored.
+- Raw API key fields are not supported in app config.
 
 ## Prompt Definition Files
 
-Prompt definitions are YAML files anywhere under `prompt_dir`, including nested subdirectories.
+Prompt definitions are YAML files anywhere under `prompt_dir`. Nested
-
+directories are organizational; callers select prompts by YAML `id`, not file
-Subdirectories are organizational only. Callers still select prompts by the YAML `id`, not by file path. For example, `prompts/dnd/recap.yaml` may still declare `id: dnd.recap`, and callers use `--prompt dnd.recap`.
+path.
 
 Example:
 
@@ -98,53 +119,76 @@ output:
   repair_attempts: 0
 ```
 
-Field reference:
+Prompt fields:
 
-- `id` (required): prompt identifier.
+| Field | Required | Description |
-- `version` (required): prompt version.
+| --- | --- | --- |
-- `default_profile` (optional): profile ID used when request does not provide `profile_id`.
+| `id` | yes | Prompt identifier used by `--prompt` and HTTP `prompt_id`. |
-- `description` (optional): prompt description.
+| `version` | yes | Prompt version. |
-- `inputs` (optional list): expected named inputs.
+| `default_profile` | no | Profile ID used when a request does not provide a profile. |
-- `messages` (required list): prompt message templates.
+| `description` | no | Human-readable description. |
-- `output` (required object): output contract.
+| `session_id` | no | Go-template string rendered from request vars and forwarded as provider `session_id` when non-empty. |
+| `inputs` | no | Named input declarations. |
+| `messages` | yes | Chat message templates. |
+| `output` | yes | Output format and validation contract. |
 
 `inputs[]` fields:
 
 - `name` (required)
-- `required` (optional, boolean)
+- `required` (optional boolean)
 - `content_type` (optional metadata)
 - `description` (optional)
 
 `messages[]` fields:
 
 - `role` (required)
-- `content` or `content_file` (exactly one is required)
+- exactly one of `content` or `content_file`
+- `cache_control` (optional)
 
 Message rules:
 
+- `content_file` resolves relative to the prompt YAML file location.
 - Repeated roles are allowed.
-- `content_file` is resolved relative to the prompt YAML file location.
+- Prompt YAML decoding is strict.
-- Nested prompt files keep the same relative `content_file` behavior; `./recap.user.md` next to `dnd/recap.yaml` resolves from `dnd/`.
+- Duplicate input names are invalid.
-- Prompt decoding is strict; unknown YAML fields are rejected.
+- Duplicate prompt IDs are invalid for a requested ID/version.
-- Duplicate prompt IDs are invalid. If multiple files declare the requested prompt ID, Scriptorium fails instead of choosing one.
+
+`messages[].cache_control` fields:
+
+| Field | Required | Supported values |
+| --- | --- | --- |
+| `type` | yes | `ephemeral` |
+| `ttl` | no | `1h` |
+
+`session_id` behavior:
+
+- Rendered with the same variable context as message templates.
+- Trimmed and omitted when empty.
+- Rejected when longer than 256 Unicode code points.
+- CLI callers pass variables with `--var`; HTTP callers use `vars`.
 
 `output` fields:
 
-- `format` (required): `text`, `markdown`, or `json`.
+| Field | Required | Supported values |
-- `validation_mode` (required): `none`, `basic`, `json`, or `json_schema`.
+| --- | --- | --- |
-- `schema_path` (required when `validation_mode: json_schema`).
+| `format` | yes | `text`, `markdown`, `json` |
-- `repair_attempts` (required): integer `>= 0`.
+| `validation_mode` | yes | `none`, `basic`, `json`, `json_schema` |
+| `schema_path` | only for `json_schema` | Relative to `schema_dir` unless absolute. |
+| `repair_attempts` | yes | Integer greater than or equal to `0`. |
 
-Repair behavior boundary:
+Repair boundary:
 
 - `repair_attempts` is part of the prompt contract.
-- CLI and HTTP currently construct the runner without a repairer, so normal `run`/`serve` execution does not perform output repair attempts.
+- The current CLI and HTTP wiring constructs the runner without a repairer, so normal `run` and `serve` execution does not perform repair attempts.
 
 ## Profile Definition Files
 
-Execution profiles are YAML files anywhere under `profile_dir`, including nested subdirectories.
+Execution profiles are YAML files anywhere under `profile_dir`. Nested
+directories are organizational; callers select profiles by YAML `id`, not file
+path.
 
-Subdirectories are organizational only. Callers still select profiles by the YAML `id`, not by file path. For example, `profiles/local/local-quality.yaml` may still declare `id: local-quality`, and callers use `--profile local-quality`.
+Scriptorium also ships built-in profiles. Custom profiles override built-ins
+with the same ID.
 
 Example:
 
@@ -158,74 +202,123 @@ top_p: 1.0
 timeout_seconds: 90
 api_key_env: SCRIPTORIUM_API_KEY
 service_tier: priority
+reasoning_effort: medium
+extra_params:
+  provider_route: primary
 ```
 
-Field reference:
+Profile fields:
 
-- `id` (required)
+| Field | Required | Description |
-- `endpoint` (required)
+| --- | --- | --- |
-- `model` (required)
+| `id` | yes | Profile identifier. |
-- `temperature` (optional): range `0..2`
+| `endpoint` | yes | OpenAI-compatible base URL including `/v1`. |
-- `max_tokens` (optional): `>= 0`
+| `model` | yes | Provider model name. |
-- `top_p` (optional): range `0..1`
+| `temperature` | no | Range `0..2`. |
-- `timeout_seconds` (optional): `>= 0`
+| `max_tokens` | no | Integer greater than or equal to `0`. |
-- `service_tier` (optional): provider-specific request tier such as OpenRouter `flex` or `priority`
+| `top_p` | no | Range `0..1`. |
-- `reasoning_effort` (optional)
+| `timeout_seconds` | no | Integer greater than or equal to `0`. |
-- `api_key_env` (optional)
+| `service_tier` | no | Provider-specific request tier. |
-- `extra_params` (optional map of strings)
+| `reasoning_effort` | no | Provider-specific reasoning setting. |
+| `api_key_env` | no | Environment variable name containing the API key. |
+| `extra_params` | no | JSON-compatible provider-specific top-level request fields. |
+
+Execution defaults before profile/request overrides:
+
+| Field | Default |
+| --- | --- |
+| `temperature` | `0.0` |
+| `max_tokens` | `0` |
+| `top_p` | `1.0` |
+| `timeout_seconds` | `600` |
 
 Profile rules:
 
-- Profile decoding is strict; unknown YAML fields are rejected.
+- Profile YAML decoding is strict.
+- Duplicate custom profile IDs are invalid.
+- Matching custom and built-in IDs are valid override behavior.
 - Raw `api_key` is rejected; use `api_key_env`.
-- If `api_key_env` is set, that environment variable must be set when preparing/running.
+- If `api_key_env` is set, the named environment variable must be set before `run`, `render`, or HTTP execution can prepare the request.
-- Duplicate profile IDs are invalid. If multiple files declare the requested profile ID, Scriptorium fails instead of choosing one.
+- Profile numeric fields merge by non-zero value. Request overrides are presence-aware, so explicit zero values are supported through CLI flags or HTTP model overrides.
+- `extra_params` keys must not be empty and must not collide with reserved outbound fields: `model`, `session_id`, `messages`, `temperature`, `max_tokens`, `top_p`, `service_tier`, `reasoning_effort`, or `response_format`.
 
-Current outbound request behavior:
+Built-in profile catalog:
 
-- The OpenAI-compatible client currently serializes: `model`, `messages`, `temperature`, `max_tokens`, `top_p`, `service_tier`, and optional `response_format` for `json_schema` prompts.
+| Provider | ID | Model | API key env |
-- `reasoning_effort` and `extra_params` are parsed and carried in effective settings, but are not currently serialized into outbound chat-completions requests.
+| --- | --- | --- | --- |
+| aion-labs | `aion-2` | `aion-labs/aion-2.0` | `OPENROUTER_API_KEY` |
+| anthropic | `claude-fable-latest` | `~anthropic/claude-fable-latest` | `OPENROUTER_API_KEY` |
+| anthropic | `claude-haiku-latest` | `~anthropic/claude-haiku-latest` | `OPENROUTER_API_KEY` |
+| anthropic | `claude-opus-latest` | `~anthropic/claude-opus-latest` | `OPENROUTER_API_KEY` |
+| anthropic | `claude-sonnet-latest` | `~anthropic/claude-sonnet-latest` | `OPENROUTER_API_KEY` |
+| deepseek | `deepseek-3-2` | `deepseek/deepseek-v3.2` | `OPENROUTER_API_KEY` |
+| deepseek | `deepseek-4-pro` | `deepseek/deepseek-v4-pro` | `OPENROUTER_API_KEY` |
+| google | `gemini-2-flash` | `google/gemini-2.5-flash` | `OPENROUTER_API_KEY` |
+| google | `gemini-2-flash-lite` | `google/gemini-2.5-flash-lite` | `OPENROUTER_API_KEY` |
+| google | `gemini-2-pro` | `google/gemini-2.5-pro` | `OPENROUTER_API_KEY` |
+| google | `gemini-3-flash-lite` | `google/gemini-3.1-flash-lite` | `OPENROUTER_API_KEY` |
+| google | `gemini-flash-latest` | `~google/gemini-flash-latest` | `OPENROUTER_API_KEY` |
+| google | `gemini-pro-latest` | `~google/gemini-pro-latest` | `OPENROUTER_API_KEY` |
+| google | `gemma-4-31b` | `google/gemma-4-31b-it:exacto` | `OPENROUTER_API_KEY` |
+| minimax | `minimax-m2` | `minimax/minimax-m2.5` | `OPENROUTER_API_KEY` |
+| minimax | `minimax-m3` | `minimax/minimax-m3` | `OPENROUTER_API_KEY` |
+| mistral | `mistral-large-2512` | `mistralai/mistral-large-2512` | `OPENROUTER_API_KEY` |
+| mistral | `mistral-medium-3-5` | `mistralai/mistral-medium-3-5` | `OPENROUTER_API_KEY` |
+| mistral | `mistral-small-3` | `mistralai/mistral-small-3.2-24b-instruct` | `OPENROUTER_API_KEY` |
+| mistral | `mistral-small-4` | `mistralai/mistral-small-2603` | `OPENROUTER_API_KEY` |
+| nvidia | `nemotron-3-ultra` | `nvidia/nemotron-3-ultra-550b-a55b` | `OPENROUTER_API_KEY` |
+| openai | `gpt-5-mini` | `openai/gpt-5.4-mini` | `OPENROUTER_API_KEY` |
+| openai | `gpt-5-nano` | `openai/gpt-5.4-nano` | `OPENROUTER_API_KEY` |
 
 ## Schema Behavior
 
-Schemas are JSON files, typically in `schema_dir`.
+Schemas are JSON files, typically under `schema_dir`.
 
 Rules:
 
 - `output.validation_mode: json_schema` requires `output.schema_path`.
-- Relative `schema_path` values resolve from `schema_dir`, including explicit nested paths such as `dnd/structured_events.schema.json`.
+- Relative `schema_path` values resolve from `schema_dir`.
 - Absolute `schema_path` values are used directly.
-- Scriptorium does not recursively search schemas by basename; nested schemas must be referenced by their relative path.
+- Nested schemas must be referenced by relative path; schemas are not searched recursively by basename.
-- Missing or invalid schema documents cause runtime validation errors.
+- Missing or invalid schema documents are runtime validation errors.
-- Invalid generated JSON causes validation status `failed` (not a runtime error).
+- Invalid generated JSON produces validation status `failed`, not a runtime error.
 
-Supported artifact reference types for request inputs are `file` and `inline`.
+## Artifact References
+
+Supported request input artifact reference types are:
+
+- `file`
+- `inline`
+
+CLI `run` and `render` create `file` references from `--input name=path`.
+
+HTTP `file` references require `server.artifact_root` or `serve
+--artifact-root`. Relative file URIs resolve under that root. Absolute paths
+and relative traversal outside the root are rejected by lexical checks. Symlinks
+inside the root are followed by the operating system, including symlinks that
+point outside the root.
+
+HTTP `inline` references do not require an artifact root.
 
 ## Secrets Handling
 
 - Keep secret values in environment variables.
-- Store only environment-variable names in profile `api_key_env`.
+- Store only environment-variable names in `api_key_env`.
-- Do not put raw API keys in config, prompts, profiles, CLI flags, or HTTP request bodies.
+- Do not put raw API keys in config, prompts, profiles, CLI arguments, examples, or HTTP request bodies.
 
 ## Maintained Examples
 
-- App config: `examples/config.yml`
+- Minimal app config: `examples/config.yml`
+- Full app config: `examples/config.full.yml`
 - Prompt examples: `examples/prompts/`
-- Profile examples: `examples/profiles/`
+- Custom profile examples: `examples/profiles/`
 - Schema examples: `examples/schemas/`
 - Input fixtures: `examples/fixtures/`
-- Render example script: `examples/render-markdown-summary.sh`
+- Render script: `examples/render-markdown-summary.sh`
-- HTTP request example: `examples/http-run.json`
+- HTTP request-shape example: `examples/http-run.json`
-
-Example organizational layout:
-
-```text
-examples/prompts/dnd/recap.yaml
-examples/profiles/local/local-quality.yaml
-examples/schemas/dnd/structured_events.schema.json
-```
 
 ## Integration References
 
-- [Inbound HTTP contract](integrations/http-api.md)
+- [CLI reference](cli.md)
+- [HTTP API reference](api.md)
 - [Outbound OpenAI-compatible contract](integrations/openai-compatible-chat.md)

docs/consumers/api.md

@@ -0,0 +1,122 @@
+# Consumer Integration Overview
+
+This guide is for applications that call Scriptorium from another codebase.
+
+Scriptorium exposes three integration surfaces:
+
+| Surface | Use when |
+| --- | --- |
+| Go package | The consumer is Go, needs typed requests/results, or wants injected LLM clients for tests. |
+| CLI subprocess | The consumer wants process isolation or is not written in Go. |
+| HTTP API | The consumer needs a service boundary or remote access to `POST /v1/runs`. |
+
+Canonical references:
+
+- Go package: [Package scriptorium](pkg-scriptorium.md)
+- CLI subprocess: [Subprocess integration](../integrations/subprocess.md)
+- HTTP: [HTTP API reference](../api.md)
+- File formats: [Configuration reference](../config.md)
+
+## Required Deployment Inputs
+
+Every integration needs operators to provide:
+
+- prompt definitions;
+- profile definitions or built-in profile IDs;
+- schema files when prompts use `json_schema`;
+- input artifacts or inline input bodies;
+- API-key environment variables or direct per-request keys where supported.
+
+Raw API keys do not belong in config, prompt files, profile YAML, CLI
+arguments, or HTTP request bodies.
+
+## Recommended Workflow
+
+Use the Go package when:
+
+- the consumer is a Go application;
+- the application needs `context.Context` cancellation;
+- repeated calls should avoid subprocess startup;
+- tests need a fake LLM client;
+- direct per-request `RunRequest.APIKey` is required.
+
+Use the CLI subprocess when:
+
+- the consumer is not Go;
+- process isolation is useful;
+- stdout/stderr separation and exit codes are enough;
+- the consumer already manages local files and environment variables.
+
+Use HTTP when:
+
+- Scriptorium should run as a service;
+- multiple clients need a shared prompt/profile deployment;
+- clients can reach a trusted, protected HTTP boundary.
+
+## Minimal Go Example
+
+```go
+engine, err := scriptorium.NewEngine(scriptorium.Config{
+	PromptDir:  "./examples/prompts",
+	ProfileDir: "./examples/profiles",
+	SchemaDir:  "./examples/schemas",
+})
+if err != nil {
+	return err
+}
+
+prepared, err := engine.Prepare(ctx, scriptorium.RunRequest{
+	PromptID: "generic.markdown_summary",
+	Inputs: map[string]scriptorium.ArtifactRef{
+		"transcript": scriptorium.File("./examples/fixtures/transcript.md"),
+		"glossary":   scriptorium.File("./examples/fixtures/glossary.yml"),
+	},
+})
+if err != nil {
+	return err
+}
+_ = prepared.Messages
+```
+
+Run the maintained package example:
+
+```bash
+go run ./examples/go-library/prepare
+```
+
+## Subprocess Workflow
+
+Invoke `scriptorium render` for preflight and `scriptorium run` for generation.
+Capture stdout and stderr separately. Treat exit code `2` from `run` as a
+completed generation with failed validation.
+
+See [Subprocess integration](../integrations/subprocess.md) for the stable
+invocation contract.
+
+## HTTP Workflow
+
+Run `scriptorium serve` behind trusted controls and send JSON requests to
+`POST /v1/runs`.
+
+Do not duplicate endpoint schemas in consumers. Use the [HTTP API
+reference](../api.md) as the authoritative contract.
+
+## Consumer Responsibilities
+
+Consumers are responsible for:
+
+- selecting prompt/profile IDs as deployment configuration;
+- supplying all required inputs and vars;
+- protecting generated artifacts and rendered prompts as sensitive data;
+- deciding whether to keep output when validation fails;
+- implementing retries only when another model call is acceptable.
+
+Scriptorium does not persist run state. Retrying a failed or timed-out request
+can produce different output and can incur another provider request.
+
+## Status Behavior
+
+- Go package methods return typed results or errors that support `errors.Is`.
+- CLI `run` exits `2` when generation succeeds but validation fails.
+- HTTP returns `200 OK` for generated-content validation failures and exposes the failed status in the response body.
+- Runtime validation failures are errors.

docs/consumers/pkg-scriptorium.md

@@ -0,0 +1,284 @@
+# Package scriptorium
+
+Import path:
+
+```go
+import "gitea.maximumdirect.net/eric/scriptorium"
+```
+
+The root package is the public Go facade for Scriptorium's prompt prepare/run
+workflow. It exposes typed requests, results, source options, injected LLM
+clients, and stable public errors while keeping `internal/*` packages private.
+
+## Intended Use Cases
+
+Use the package when a Go application needs:
+
+- in-process prompt preparation or execution;
+- typed request/result structs;
+- direct `context.Context` cancellation;
+- injected/fake LLM clients for tests;
+- direct per-request `RunRequest.APIKey`.
+
+Use [Subprocess integration](../integrations/subprocess.md) or the [HTTP API](../api.md)
+when a process or service boundary is preferred.
+
+## Construct An Engine
+
+```go
+engine, err := scriptorium.NewEngine(scriptorium.Config{
+	PromptDir:  "./examples/prompts",
+	ProfileDir: "./examples/profiles",
+	SchemaDir:  "./examples/schemas",
+})
+if err != nil {
+	return err
+}
+```
+
+`Config` fields:
+
+| Field | Description |
+| --- | --- |
+| `PromptDir` | Prompt definition directory. Required unless `WithPromptFS` or `WithPromptFile` is used. |
+| `ProfileDir` | Optional custom profile directory overlaid above built-in profiles. |
+| `SchemaDir` | Schema directory. Defaults to `.` when empty. |
+| `Timeout` | Default timeout for the built-in OpenAI-compatible client. |
+| `HTTPClient` | Optional HTTP client for the built-in OpenAI-compatible client. |
+
+`NewEngine` accepts `nil` options and ignores them. Invalid construction wraps
+`ErrInvalidConfig`.
+
+## Source Options
+
+Directory fields are the compatibility path. Explicit source options override
+the matching directory field.
+
+Prompt sources:
+
+- `WithPromptFS(fsys, root)`
+- `WithPromptFile(path)`
+
+Profile sources:
+
+- `WithProfileFS(fsys, root)`
+- `WithProfileFile(path)`
+- `WithProfiles(profiles...)`
+
+Schema sources:
+
+- `WithSchemaFS(fsys, root)`
+- `WithSchemaFile(path)`
+
+LLM source:
+
+- `WithLLMClient(client)`
+
+Source behavior:
+
+- Prompt and profile YAML use the same strict rules as directory loading.
+- Prompt `content_file` values resolve relative to the prompt file.
+- `fs.FS` roots are containment boundaries for prompt content files and schema paths.
+- File options expose the selected file by its base name.
+- Profile source precedence is in-memory profiles, then explicit profile file/FS/directory source, then built-ins.
+- `WithLLMClient(nil)` returns `ErrInvalidConfig`.
+
+## In-Memory Profiles
+
+Use `WithProfiles` when the application already has typed model settings:
+
+```go
+profile := scriptorium.OpenAICompatibleProfile(scriptorium.OpenAICompatibleProfileConfig{
+	ID:             "app.default",
+	Endpoint:       "https://openrouter.ai/api/v1",
+	Model:          "mistralai/mistral-small-3.2-24b-instruct",
+	APIKeyRequired: true,
+})
+
+engine, err := scriptorium.NewEngine(cfg, scriptorium.WithProfiles(profile))
+```
+
+`Profile` and `OpenAICompatibleProfileConfig` include:
+
+- `ID`
+- `Endpoint`
+- `Model`
+- `Temperature`
+- `MaxTokens`
+- `TopP`
+- `TimeoutSeconds`
+- `ServiceTier`
+- `ReasoningEffort`
+- `APIKeyRequired`
+- `ExtraParams`
+
+`WithProfiles` rejects duplicate IDs in one call. In-memory profiles do not
+store raw keys. When `APIKeyRequired` is true, pass the secret on each request
+with `RunRequest.APIKey`.
+
+`ExtraParams` must be JSON-compatible: strings, booleans, finite numbers,
+objects with string keys, arrays/slices, and nil. Unsupported values, non-string
+map keys, non-finite floats, and cycles return `ErrInvalidConfig` for profiles
+or `ErrInvalidRequest` for request overrides.
+
+## Prepare Workflow
+
+`Prepare` resolves prompt/profile/input/schema state and renders messages
+without calling an LLM.
+
+```go
+prepared, err := engine.Prepare(ctx, scriptorium.RunRequest{
+	PromptID: "generic.markdown_summary",
+	Inputs: map[string]scriptorium.ArtifactRef{
+		"transcript": scriptorium.File("./examples/fixtures/transcript.md"),
+		"glossary":   scriptorium.File("./examples/fixtures/glossary.yml"),
+	},
+})
+if err != nil {
+	return err
+}
+_ = prepared.EffectiveModelParams
+```
+
+`PreparedRun` includes prompt ID/version/hash, selected profile, effective
+model params, output contract, structured-output metadata, input hashes,
+rendered prompt hash, rendered messages, and timing fields. It does not include
+raw API-key values, model output, validation results, or internal target
+presence metadata.
+
+## Run Workflow
+
+`Run` calls `Prepare`, invokes the configured LLM client, builds the output
+artifact, and validates the output.
+
+```go
+result, err := engine.Run(ctx, scriptorium.RunRequest{
+	PromptID: "generic.markdown_summary",
+	APIKey:   apiKey,
+	Inputs: map[string]scriptorium.ArtifactRef{
+		"transcript": scriptorium.File("./examples/fixtures/transcript.md"),
+		"glossary":   scriptorium.File("./examples/fixtures/glossary.yml"),
+	},
+})
+if err != nil {
+	return err
+}
+_ = result.Artifact
+```
+
+`RunResult` includes run ID, output artifact, raw output, validation result,
+prompt/profile/model metadata, effective model params, input hashes, usage, and
+timing fields.
+
+Generated-content validation failures return a successful `RunResult` with
+`Validation.Status == ValidationFailed`. Runtime/schema validation errors
+return an error that matches `ErrValidation`.
+
+## Inputs
+
+Input helpers:
+
+- `File(path)`: file-backed artifact reference.
+- `Inline(body)`: inline artifact body.
+- `InlineWithURI(uri, body)`: inline artifact body with URI metadata.
+
+Input map keys must match the prompt's expected input names.
+
+## Injected LLM Clients
+
+Use `WithLLMClient` for tests or custom model integrations:
+
+```go
+type fakeLLM struct{}
+
+func (fakeLLM) Generate(ctx context.Context, req scriptorium.GenerateRequest) (*scriptorium.GenerateResponse, error) {
+	return &scriptorium.GenerateResponse{
+		Content: "generated text",
+		Usage:   scriptorium.TokenUsage{TotalTokens: 12},
+	}, nil
+}
+
+engine, err := scriptorium.NewEngine(cfg, scriptorium.WithLLMClient(fakeLLM{}))
+```
+
+Injected clients receive:
+
+- rendered prompt;
+- effective execution target;
+- numeric target presence metadata;
+- structured-output spec when applicable;
+- direct request API key when provided.
+
+Custom clients should not log raw prompts or API keys by default.
+
+## Overrides And API Keys
+
+`RunRequest` fields:
+
+| Field | Description |
+| --- | --- |
+| `PromptID` | Prompt ID. |
+| `PromptVersion` | Optional prompt version filter. |
+| `ProfileID` | Optional profile override. |
+| `APIKey` | Direct per-request API key. |
+| `Inputs` | Input artifact references. |
+| `Vars` | Template variables. |
+| `Execution` | Per-request model overrides. |
+| `Validation` | Per-request output contract override. |
+| `Metadata` | Request metadata reserved for callers. |
+
+`RunRequest.Execution` uses pointer fields for numeric values so explicit zero
+overrides are preserved:
+
+```go
+zero := 0
+req.Execution = &scriptorium.ExecutionTargetOverride{
+	MaxTokens: &zero,
+}
+```
+
+Direct `RunRequest.APIKey` takes precedence over profile `api_key_env` for the
+default OpenAI-compatible client. It is request-scoped, uses `json:"-"`, and is
+not included in `PreparedRun` or `RunResult` JSON. Normal Go string formatting
+of `RunRequest` and `GenerateRequest` reports only whether a direct key is set.
+
+Raw API keys do not belong in profile YAML, in-memory profiles, or app config.
+Avoid reflection-based debug dumps of request structs because exported fields
+remain visible to tools that bypass `String` and `GoString`.
+
+## Errors
+
+Public methods wrap context while preserving stable sentinel checks with
+`errors.Is`:
+
+- `ErrInvalidConfig`
+- `ErrInvalidRequest`
+- `ErrPromptNotFound`
+- `ErrProfileNotFound`
+- `ErrPromptLoad`
+- `ErrProfileLoad`
+- `ErrArtifactLoad`
+- `ErrPromptRender`
+- `ErrLLMGenerate`
+- `ErrValidation`
+
+Example:
+
+```go
+if errors.Is(err, scriptorium.ErrPromptNotFound) {
+	return err
+}
+```
+
+## Examples
+
+Run the maintained prepare-only example from the repository root:
+
+```bash
+go run ./examples/go-library/prepare
+```
+
+See also:
+
+- [Configuration reference](../config.md)
+- [Consumer integration overview](api.md)

docs/integrations/http-api.md

@@ -1,192 +0,0 @@
-# HTTP API Integration
-
-## Scope
-
-This document defines the implemented inbound HTTP contract for Scriptorium.
-
-Current scope is only:
-
-- `POST /v1/runs`
-
-For CLI behavior, see the [CLI reference](../cli.md).
-
-## Endpoint
-
-- Method: `POST`
-- Path: `/v1/runs`
-- Content type: JSON request/response
-
-Route behavior:
-
-- unknown path: `404 not_found`
-- unsupported method on `/v1/runs`: `405 method_not_allowed`
-
-Copyable request example file:
-
-- `examples/http-run.json`
-
-## Request Body
-
-```json
-{
-  "prompt_id": "generic.structured_events",
-  "profile_id": "local-quality",
-  "prompt_version": "1.0.0",
-  "inputs": {
-    "transcript": {"type": "file", "uri": "./examples/fixtures/transcript.md"},
-    "glossary": {"type": "inline", "body": "party:\n  - Rin"}
-  },
-  "vars": {
-    "session_date": "2026-05-04"
-  },
-  "model": {
-    "endpoint": "http://localhost:8000/v1",
-    "model": "gpt-4o-mini",
-    "temperature": 0.0,
-    "max_tokens": 800,
-    "top_p": 1.0,
-    "timeout_seconds": 120,
-    "service_tier": "priority",
-    "reasoning_effort": "medium",
-    "api_key_env": "SCRIPTORIUM_API_KEY",
-    "extra_params": {
-      "route": "primary"
-    }
-  },
-  "include_raw_output": false
-}
-```
-
-Required fields:
-
-- `prompt_id`
-- `inputs` (must contain at least one named input)
-
-Input reference types currently supported by runtime artifact loading:
-
-- `file`
-- `inline`
-
-## Strict JSON Rules
-
-Request decoding uses strict JSON field checks:
-
-- unknown request fields are rejected with `400 invalid_json`
-- unknown `model` fields are rejected with `400 invalid_json`
-- raw API-key payload fields such as `api_key` are rejected as unknown fields
-
-## Success Response
-
-Status: `200 OK`
-
-Response shape:
-
-```json
-{
-  "artifact": {
-    "name": "output",
-    "content_type": "application/json",
-    "body": "{\"summary\":\"...\"}",
-    "uri": "",
-    "size": 123,
-    "hash": "..."
-  },
-  "validation": {
-    "status": "passed",
-    "mode": "json_schema",
-    "errors": [],
-    "schema_path": "structured_events.schema.json",
-    "repair_attempts": 0,
-    "is_valid": true
-  },
-  "metadata": {
-    "run_id": "...",
-    "prompt_id": "generic.structured_events",
-    "prompt_version": "1.0.0",
-    "prompt_hash": "...",
-    "rendered_prompt_hash": "...",
-    "selected_profile_id": "local-quality",
-    "model_name": "gpt-4o-mini",
-    "endpoint": "http://localhost:8000/v1",
-    "model_params": {
-      "endpoint": "http://localhost:8000/v1",
-      "model": "gpt-4o-mini",
-      "temperature": 0,
-      "max_tokens": 800,
-      "top_p": 1,
-      "timeout_seconds": 120,
-      "service_tier": "priority",
-      "reasoning_effort": "medium",
-      "api_key_env": "SCRIPTORIUM_API_KEY",
-      "extra_params": {
-        "route": "primary"
-      }
-    },
-    "input_hashes": {
-      "transcript": "..."
-    },
-    "usage": {
-      "prompt_tokens": 11,
-      "completion_tokens": 22,
-      "total_tokens": 33
-    },
-    "start_time": "2026-05-04T12:00:00Z",
-    "end_time": "2026-05-04T12:00:01Z",
-    "duration_ms": 1000,
-    "validation_mode": "json_schema",
-    "validation_status": "passed",
-    "repair_attempts_used": 0
-  }
-}
-```
-
-`raw_model_output` is omitted by default.
-
-To include it, send:
-
-- `"include_raw_output": true`
-
-## Validation Failure Behavior
-
-Validation content failures do not map to HTTP error status.
-
-Behavior:
-
-- status remains `200 OK`
-- `validation.status` is `failed`
-- validation errors are returned in `validation.errors`
-
-## Error Responses
-
-Error body shape:
-
-```json
-{
-  "error": {
-    "code": "invalid_request",
-    "message": "prompt_id is required"
-  }
-}
-```
-
-Current error mapping (non-exhaustive):
-
-- `400 invalid_json`: malformed JSON or unknown JSON fields
-- `400 invalid_request`: missing/invalid request fields
-- `400 profile_required`: no explicit `profile_id` and prompt has no `default_profile`
-- `400 prompt_load_failed`: prompt definition invalid/unloadable
-- `400 profile_load_failed`: profile invalid/unloadable
-- `400 artifact_read_failed`: input artifact loading failed
-- `400 prompt_render_failed`: template render failed
-- `400 api_key_env_missing`: named API-key environment variable is missing
-- `404 prompt_not_found`
-- `404 profile_not_found`
-- `502 llm_failed`: outbound model request failed
-- `500 validation_runtime_failed`: validator runtime/schema-load failure
-- `500 internal_error`
-
-## Security And Deployment Note
-
-The HTTP adapter has no built-in authentication or authorization.
-
-Deploy behind trusted controls (for example authenticated gateway/reverse proxy and network boundaries).

docs/integrations/narratio.md

@@ -1,114 +0,0 @@
-# Narratio Subprocess Integration
-
-## Purpose
-
-This document defines the supported subprocess contract for Narratio invoking Scriptorium through the public CLI.
-
-This is a CLI contract, not an internal Go package integration.
-
-## Supported Commands
-
-Narratio should invoke:
-
-- `scriptorium run`
-- `scriptorium render`
-
-Use `run` for generation.
-
-Use `render` for preflight/debug output without LLM execution.
-
-## Recommended Invocation Shapes
-
-Run:
-
-```bash
-scriptorium run \
-  --prompt <prompt_id> \
-  --input transcript=<path> \
-  --out <artifact_path>
-```
-
-Render:
-
-```bash
-scriptorium render \
-  --prompt <prompt_id> \
-  --input transcript=<path> \
-  --format json
-```
-
-Narratio may add:
-
-- `--config <path>`
-- `--profile <profile_id>`
-- repeatable `--input name=path`
-- repeatable `--var name=value`
-- runtime overrides when explicitly needed (`--model`, `--llm-base-url`, `--timeout`, etc.)
-
-## Config And Directory Behavior
-
-Narratio can rely on resolved app config or pass explicit paths.
-
-- default config search order:
-  1. `/usr/local/etc/scriptorium/config.yml`
-  2. `/etc/scriptorium/config.yml`
-- explicit `--config` requires file existence and valid syntax
-- CLI flags override config values
-
-## Profile Selection
-
-Profile selection follows runner behavior:
-
-1. explicit `--profile`
-2. prompt `default_profile`
-3. error if neither is available
-
-Narratio should treat prompt/profile IDs as deployment configuration, not hardcoded logic.
-
-## Input And Variable Contract
-
-- Inputs use repeated `--input name=path`.
-- Input names must match prompt definition input names.
-- Variables use repeated `--var name=value` for small metadata values.
-- Prefer file inputs for large content.
-
-## Environment Contract
-
-- Pass through required API-key environment variables referenced by `api_key_env`.
-- Never pass raw API keys via CLI arguments.
-- Keep subprocess environment scoped to required variables.
-
-## Output And Error Handling
-
-`run`:
-
-- stdout: artifact body unless `--out` is used
-- `--out`: writes artifact to file
-- stderr: success summary and errors
-
-`render`:
-
-- stdout: prepared-run output unless `--out` is used
-- stderr: errors
-
-Narratio should capture stdout and stderr separately.
-
-## Exit Status Contract
-
-- `0`: success
-- `1`: parse/config/load/render/generation/IO/runtime error
-- `2`: run completed but validation failed
-
-A `run` exit code `2` can still produce output (stdout or `--out`).
-
-## Security Notes
-
-- Treat generated artifacts and stderr logs as potentially sensitive.
-- Avoid logging full rendered prompts by default in production contexts.
-- Use controlled output paths and access controls for persisted artifacts.
-
-## Canonical References
-
-- CLI behavior: [CLI reference](../cli.md)
-- Config behavior: [Configuration reference](../config.md)
-- Operations and failure handling: [Operations guide](../operations.md), [Troubleshooting](../troubleshooting.md)

docs/integrations/openai-compatible-chat.md

@@ -26,15 +26,85 @@ Example:
 Serialized JSON fields:
 
 - `model` (required after fallback resolution)
-- `messages` (role/content pairs from rendered prompt)
+- `session_id` (only when the rendered prompt includes a non-empty session ID)
-- `temperature` (only when non-zero)
+- `messages` (rendered prompt messages)
-- `max_tokens` (only when non-zero)
+- `temperature` (when non-zero, or when explicitly overridden to zero)
-- `top_p` (only when non-zero)
+- `max_tokens` (when non-zero, or when explicitly overridden to zero)
+- `top_p` (when non-zero, or when explicitly overridden to zero)
 - `service_tier` (only when non-empty)
+- `reasoning_effort` (only when non-empty)
 - `response_format` (only when structured output is provided)
+- profile/request `extra_params` as additional provider-specific top-level fields
 
 `service_tier` is provider-specific. OpenRouter currently documents request values such as `flex` and `priority`; Scriptorium forwards any non-empty configured value and lets the backend validate support.
 
+`reasoning_effort` is provider-specific. Scriptorium forwards any non-empty configured value as top-level `reasoning_effort` and lets the backend validate support.
+
+`extra_params` are flattened into the outbound JSON object. They are not wrapped in an `extra_params` object:
+
+```json
+{
+  "model": "gpt-4o-mini",
+  "messages": [
+    {
+      "role": "user",
+      "content": "rendered text"
+    }
+  ],
+  "provider_route": "primary",
+  "provider_options": {
+    "retry_budget": 2
+  }
+}
+```
+
+`extra_params` values must be JSON-compatible. Supported value shapes include strings, numbers, booleans, objects, and arrays.
+
+Reserved `extra_params` keys are rejected before the HTTP request is made:
+
+- `model`
+- `session_id`
+- `messages`
+- `temperature`
+- `max_tokens`
+- `top_p`
+- `service_tier`
+- `reasoning_effort`
+- `response_format`
+
+Empty `extra_params` keys and values that cannot be encoded as JSON are also rejected before the HTTP request is made.
+
+`session_id` is rendered from prompt YAML using request variables and serialized as a top-level JSON request field. Scriptorium does not send an `x-session-id` header. Empty rendered session IDs are omitted, and values longer than 256 characters are rejected before the HTTP request.
+
+Messages without prompt cache control serialize with string `content`:
+
+```json
+{
+  "role": "system",
+  "content": "rendered text"
+}
+```
+
+Messages with prompt cache control serialize as a single text content-block array:
+
+```json
+{
+  "role": "system",
+  "content": [
+    {
+      "type": "text",
+      "text": "rendered text",
+      "cache_control": {
+        "type": "ephemeral",
+        "ttl": "1h"
+      }
+    }
+  ]
+}
+```
+
+When cache-control `ttl` is unset in the prompt definition, `ttl` is omitted from the outbound payload.
+
 Structured output is currently `json_schema` only, serialized as:
 
 ```json
@@ -52,7 +122,12 @@ Structured output is currently `json_schema` only, serialized as:
 
 ## Authentication Header
 
-If `Target.APIKeyEnv` is set:
+If `Target.APIKey` is set:
+
+- set `Authorization: Bearer <value>`
+- do not read `Target.APIKeyEnv`
+
+If `Target.APIKey` is empty and `Target.APIKeyEnv` is set:
 
 - resolve environment variable value at request time
 - set `Authorization: Bearer <value>`
@@ -61,7 +136,7 @@ If the environment variable is unset/empty:
 
 - request fails before HTTP call (`ErrInvalidRequest`)
 
-If `Target.APIKeyEnv` is empty:
+If both `Target.APIKey` and `Target.APIKeyEnv` are empty:
 
 - no `Authorization` header is sent
 
@@ -72,6 +147,7 @@ Base timeout comes from client configuration.
 Per-request override:
 
 - if `Target.TimeoutSeconds > 0`, use that value for request timeout
+- if `Target.TimeoutSeconds == 0` and the value came from an explicit request override, disable the HTTP client timeout
 - if `Target.TimeoutSeconds < 0`, request is rejected (`ErrInvalidRequest`)
 
 ## Response Expectations
@@ -82,6 +158,13 @@ Expected successful response shape (subset used):
 - `usage.prompt_tokens`
 - `usage.completion_tokens`
 - `usage.total_tokens`
+- `usage.prompt_tokens_details.cached_tokens` (optional)
+- `usage.cache_write_tokens` (optional)
+
+Absent cache usage fields are treated as zero. Parsed cache usage is exposed through run results and adapter response surfaces as:
+
+- `cached_tokens`
+- `cache_write_tokens`
 
 Malformed response conditions include:
 
@@ -94,15 +177,12 @@ Malformed responses return `ErrMalformedResponse`.
 ## Error Handling
 
 - network/request-construction failures: `ErrRequestFailed`
-- non-2xx HTTP status: `ErrUnexpectedStatus` (includes status code and trimmed response body snippet)
+- non-2xx HTTP status: `ErrUnexpectedStatus` (includes status code; provider response bodies are not included)
 - malformed response shape/content: `ErrMalformedResponse`
 
 ## Unsupported Or Non-Serialized Fields
 
-The following fields may exist in profile/effective settings but are not currently serialized into outbound chat-completions payloads:
+The client does not serialize top-level `cache_control`.
-
-- `reasoning_effort`
-- `extra_params`
 
 No built-in retries, tool-calls, or multi-request payload modes are implemented in this client.
 

docs/integrations/subprocess.md

@@ -0,0 +1,130 @@
+# Subprocess Integration
+
+This document defines the supported subprocess contract for downstream
+applications invoking Scriptorium through the public CLI.
+
+This is a CLI contract. Go callers that want an in-process typed API should use
+the [package guide](../consumers/pkg-scriptorium.md).
+
+## Supported Commands
+
+Downstream applications should invoke:
+
+- `scriptorium render` for preflight/debug output without LLM execution.
+- `scriptorium run` for generation.
+
+`scriptorium serve` is an HTTP service command, not the recommended subprocess
+contract for per-request execution.
+
+## Recommended Invocation Shapes
+
+Render:
+
+```bash
+scriptorium render \
+  --config <config_path> \
+  --prompt <prompt_id> \
+  --input transcript=<path> \
+  --format json
+```
+
+Run:
+
+```bash
+scriptorium run \
+  --config <config_path> \
+  --prompt <prompt_id> \
+  --input transcript=<path> \
+  --out <artifact_path>
+```
+
+Callers may add:
+
+- `--profile <profile_id>`
+- repeatable `--input name=path`
+- repeatable `--var name=value`
+- runtime overrides when explicitly needed, such as `--model`, `--llm-base-url`, `--api-key-env`, and `--timeout`
+
+Do not pass raw API keys as command arguments.
+
+## Config And Directory Behavior
+
+Callers can rely on resolved app config or pass explicit paths.
+
+Default config search order:
+
+1. `/usr/local/etc/scriptorium/config.yml`
+2. `/etc/scriptorium/config.yml`
+
+Rules:
+
+- Explicit `--config` requires file existence and valid syntax.
+- CLI flags override config values.
+- `run` and `render` require an effective `prompt_dir`.
+- `profile_dir` is optional because built-in profiles are available.
+
+## Profile Selection
+
+Profile selection follows runner behavior:
+
+1. explicit `--profile`
+2. prompt `default_profile`
+3. error if neither is available
+
+Treat prompt and profile IDs as deployment configuration, not hardcoded business
+logic.
+
+## Input And Variable Contract
+
+- Inputs use repeated `--input name=path`.
+- Input names must match prompt definition input names.
+- Variables use repeated `--var name=value`.
+- Both flags also accept comma-separated mappings.
+- Prefer file inputs for large content.
+
+CLI inputs are file references. HTTP-only `inline` references are documented in
+the [HTTP API reference](../api.md).
+
+## Environment Contract
+
+- Pass through required API-key environment variables referenced by `api_key_env`.
+- Keep subprocess environments scoped to required variables.
+- Use `--api-key-env` only to name an environment variable.
+- Never pass raw API keys via argv.
+
+## Stdout And Stderr
+
+`run`:
+
+- stdout: generated artifact body unless `--out` is used.
+- stderr: success summary and errors.
+
+`render`:
+
+- stdout: prepared-run output unless `--out` is used.
+- stderr: errors.
+
+Capture stdout and stderr separately. Do not parse stderr as a stable data
+format beyond exit status handling.
+
+## Exit Status Contract
+
+- `0`: success.
+- `1`: parse, config, load, render, generation, IO, or runtime error.
+- `2`: `run` completed and output was written, but validation failed.
+
+A `run` exit code `2` can still produce output on stdout or at `--out`.
+Consumers must decide whether to keep or discard that output.
+
+## Security Notes
+
+- Treat generated artifacts, rendered prompts, stdout, and stderr as potentially sensitive.
+- Use controlled output paths and access controls for persisted artifacts.
+- Avoid logging full rendered prompts or generated artifacts by default.
+
+## Canonical References
+
+- CLI behavior: [CLI reference](../cli.md)
+- Config and file formats: [Configuration reference](../config.md)
+- Operations: [Operations guide](../operations.md)
+- Troubleshooting: [Troubleshooting](../troubleshooting.md)

docs/internal/adapters.md

@@ -1,114 +1,81 @@
-# Adapter And Repository Internals
+# Adapter Internals
 
 ## Purpose
 
-This document describes implemented adapter/repository boundaries and their current behavior.
+Adapters translate external interfaces into domain requests and translate domain results back out. They wire dependencies, apply app config, and own IO concerns, but they do not make runner decisions.
+
+Source-loading behavior belongs in `docs/internal/sources.md`. User-facing CLI, HTTP, and package contracts belong in `docs/cli.md`, `docs/api.md`, and `docs/consumers/pkg-scriptorium.md`.
 
 ## Adapter Map
 
-- `internal/adapter/cli`: CLI command parsing, app wiring, stdout/stderr handling, exit codes.
+- `cmd/scriptorium`: process entrypoint.
-- `internal/adapter/http`: HTTP request/response mapping for `POST /v1/runs`.
+- `internal/adapter/cli`: command parsing, config handoff, runner construction, stdout/stderr, exit codes.
-- `internal/promptdef`: filesystem prompt-definition repository.
+- `internal/adapter/http`: `POST /v1/runs` request/response mapping and HTTP error/status mapping.
-- `internal/profile`: filesystem execution-profile repository.
+- root package `scriptorium`: public Go facade over internal runner types and dependencies.
-- `internal/artifact`: input artifact reader.
+
-- `internal/prompt`: Go-template renderer.
+Supporting implementation packages used during adapter wiring:
-- `internal/llm`: OpenAI-compatible LLM client implementation.
+
-- `internal/validate`: output validator.
+- `internal/config`
-- `internal/format`: prepared-run formatters for `render` output.
+- `internal/defaults`
+- `internal/format`
+- `internal/llm`
+- `internal/prompt`
 
 ## Inputs And Outputs
 
 CLI adapter:
 
-- Input: process args, filesystem config/assets, environment.
+- Input: process args, optional config file, filesystem sources, environment variables.
-- Output: exit code, stdout artifact/prepared output, stderr summaries/errors.
+- Output: process exit code, stdout artifact/prepared output, stderr summaries and errors.
 
 HTTP adapter:
 
-- Input: JSON request body (`runRequestDTO`).
+- Input: HTTP request method/path/headers/body for `POST /v1/runs`.
-- Output: JSON success/error body with mapped status codes.
+- Output: JSON success or error body with mapped status code.
 
-Filesystem repositories:
+Public Go facade:
 
-- Input: prompt/profile YAML files under configured directories.
+- Input: typed `scriptorium.Config`, `Option`, and `RunRequest` values.
-- Output: normalized domain definitions/profiles or typed errors.
+- Output: typed `PreparedRun` and `RunResult` values plus public sentinel errors.
-
-Artifact reader:
-
-- Input: `domain.ArtifactRef`.
-- Output: loaded `domain.Artifact`.
-
-LLM adapter:
-
-- Input: `domain.GenerateRequest`.
-- Output: `domain.GenerateResponse`.
-
-Validator:
-
-- Input: artifact body + output contract.
-- Output: validation result or runtime validation error.
 
 ## Boundaries
 
-- Adapters convert external representations to domain requests and back.
+- Adapters convert external shapes to `domain.RunRequest` and back.
-- Use-case decisions remain in `internal/usecase`.
+- Runner orchestration remains in `internal/usecase`.
-- External dependency details stay scoped to adapter packages.
+- Prompt/profile/schema/artifact source rules remain in repository, validator, and artifact packages.
+- LLM provider request serialization remains in `internal/llm`.
+- Public package types are facade types; internal domain types do not leak across the package boundary.
 
 ## Config Fields Used
 
-Primary app settings consumed by adapters:
+Adapter app settings:
 
 - `prompt_dir`
 - `profile_dir`
 - `schema_dir`
 - `server.addr`
+- `server.artifact_root`
+- `server.max_request_bytes`
+- `server.max_artifact_bytes`
+- `server.max_response_bytes`
 - `defaults.render_format`
 
-Execution profile/request settings used through runner:
+Execution request/profile settings passed through the runner:
 
-- `endpoint`, `model`, `temperature`, `max_tokens`, `top_p`, `timeout_seconds`, `service_tier`, `api_key_env`, `reasoning_effort`, `extra_params`
+- `endpoint`
+- `model`
+- `temperature`
+- `max_tokens`
+- `top_p`
+- `timeout_seconds`
+- `service_tier`
+- `api_key_env`
+- `reasoning_effort`
+- `extra_params`
 
-## External Dependencies
+CLI and HTTP preserve numeric override presence so omitted values and explicit zero values remain distinct.
 
-- YAML decoding: `gopkg.in/yaml.v3` (strict known-fields mode in config/prompt/profile loaders).
+## CLI Adapter
-- JSON Schema validation: `github.com/santhosh-tekuri/jsonschema/v6`.
-- HTTP client/server: Go standard library.
-
-## Failure Behavior
-
-Strict decoding and input checks:
-
-- config/prompt/profile loaders reject unknown YAML fields.
-- prompt/profile repositories scan nested subdirectories recursively.
-- prompt/profile lookup uses YAML `id` values; subdirectory paths are organizational only.
-- duplicate prompt/profile IDs are invalid and fail instead of using first-match behavior.
-- HTTP DTO decoder rejects unknown JSON fields.
-- raw API key payload fields are rejected by strict decoding in profile/http paths.
-
-Artifact refs:
-
-- Supported reference types: `inline`, `file`.
-- Unsupported types return `ErrUnsupportedRefType`.
-
-LLM adapter:
-
-- endpoint appends `/chat/completions`.
-- non-2xx responses map to request failure errors.
-- malformed responses (including missing/empty first choice content) are errors.
-
-Validator:
-
-- `basic`, `json`, `json_schema` content failures return `ValidationFailed` results.
-- schema load/compile/path failures are runtime errors.
-- schema lookup uses explicit `schema_path` values relative to `schema_dir`; it does not recursively search by basename.
-
-HTTP error mapping:
-
-- maps domain/use-case errors to stable HTTP code + error code/message.
-- distinguishes missing profile selection and missing `api_key_env` variable using stable use-case sentinel errors.
-- avoids returning internal wrapped-cause details in response payload.
-
-## CLI Adapter Semantics
 
 Implemented commands:
 
@@ -116,29 +83,73 @@ Implemented commands:
 - `render`
 - `serve`
 
-Behavior highlights:
+Behavior:
 
-- `run` exit `2` indicates validation failed after generation.
+- `run` constructs a runner with direct filesystem artifact reading and calls `Runner.Run`.
-- `render` does not call the LLM.
+- `render` constructs a runner and calls `Runner.Prepare`; it does not call the LLM.
-- `serve` exposes HTTP handler only; no built-in auth.
+- `serve` constructs a restricted artifact reader and HTTP handler, then starts an unauthenticated HTTP server.
-- `render` supports `--format text|json`; `render` does not expose `--schema-dir`.
+- `run` exits `2` when generation succeeds but validation fails.
-- deprecated aliases `--prompt-id` and `--profile-id` are still accepted.
+- parse, runtime, and output-write errors exit `1`.
+- deprecated `--prompt-id` and `--profile-id` aliases are accepted.
 
-## Tests To Inspect Before Changing
+## HTTP Adapter
+
+Behavior:
+
+- Accepts only `POST /v1/runs`.
+- Decodes JSON strictly and rejects unknown fields and trailing JSON tokens.
+- Rejects empty `prompt_id` and empty `inputs` before calling the runner.
+- Does not accept raw API key values in the request body.
+- Returns validation failures as `200` responses with failed validation details.
+- Maps request-body, artifact, and encoded-response size failures to `413`.
+- Maps domain and repository errors to stable error codes without returning wrapped internal cause text.
+
+The HTTP adapter has no built-in authentication or authorization. Deployment controls must be provided outside the process.
+
+## Public Go Facade
+
+Behavior:
+
+- `NewEngine` wires the same default runner components as CLI/HTTP unless options override them.
+- Prompt, profile, and schema sources may come from directories, single files, or `fs.FS` roots.
+- `WithProfiles` adds in-memory profiles ahead of file-backed and built-in profiles.
+- `WithLLMClient` injects custom model behavior.
+- `RunRequest.APIKey` is request-scoped and direct; it is used only for generation and is stripped from public results.
+- internal errors are mapped to public sentinels in `errors.go`.
+
+## Failure Behavior
+
+Adapters should:
+
+- keep external error payloads concise and stable.
+- avoid leaking raw secret values.
+- use sentinels and typed errors for mapping.
+- preserve strict external input decoding.
+- keep validation content failures distinct from runtime errors.
+
+CLI writes human-readable summaries to stderr. HTTP writes JSON error envelopes. The public Go facade returns typed errors.
+
+## State And Manifests
+
+Adapters do not add durable run state.
+
+- No adapter writes run manifests.
+- No adapter implements checkpoint, skip, or resume behavior.
+- CLI output files are caller-selected artifacts, not internal state.
+
+## Tests To Inspect
 
 - `internal/adapter/cli/run_test.go`
 - `internal/adapter/http/handler_test.go`
-- `internal/promptdef/repository_test.go`
+- `engine_test.go`
-- `internal/profile/repository_test.go`
-- `internal/artifact/reader_test.go`
-- `internal/prompt/renderer_test.go`
-- `internal/llm/openai_compatible_client_test.go`
-- `internal/validate/standard_validator_test.go`
 - `internal/format/prepared_run_test.go`
+- `internal/llm/openai_compatible_client_test.go`
 
 ## Architectural Invariants
 
-- Adapter packages do not own runner decision logic.
+- Adapter packages stay thin and translation-focused.
-- External request/response strictness is part of contract stability.
+- App config is resolved before dependency construction.
-- Prepared-render output never includes resolved API key values.
+- External input strictness is part of contract stability.
-- Outbound OpenAI-compatible request includes only currently serialized fields (`model`, `messages`, optional `temperature`, `max_tokens`, `top_p`, optional `service_tier`, optional `response_format`).
+- CLI and HTTP construct runners without a repairer.
+- HTTP endpoint details remain canonical in `docs/api.md`.
+- Public Go package details remain canonical in `docs/consumers/pkg-scriptorium.md`.

docs/internal/runner.md

@@ -2,29 +2,32 @@
 
 ## Purpose
 
-`internal/usecase.Runner` is the core use case orchestrator for prompt preparation and execution.
+`internal/usecase.Runner` is the core prompt-execution orchestrator. It prepares prompt requests, calls the configured LLM client for `Run`, validates generated output, and returns domain results.
 
-It owns request validation, prompt/profile resolution, runtime-parameter merge, artifact loading, prompt rendering, structured-output setup, LLM invocation, output validation, and result metadata.
+Transport parsing, DTOs, CLI output, HTTP status mapping, and public package type conversion belong outside the runner.
 
 ## Inputs And Outputs
 
-Primary input type:
+Primary inputs:
 
 - `domain.RunRequest`
+- repositories/readers/renderers/validators injected at construction
+- `context.Context` for cancellation
 
-Primary output types:
+Primary outputs:
 
 - `domain.PreparedRun` from `Prepare`
 - `domain.RunResult` from `Run`
+- wrapped sentinel errors for adapter mapping
 
 LLM boundary types:
 
 - `domain.GenerateRequest`
 - `domain.GenerateResponse`
 
-## Boundaries
+## Dependencies
 
-`Runner` coordinates the following interfaces:
+`Runner` depends on package interfaces instead of concrete adapter types:
 
 - `promptdef.Repository`
 - `profile.Repository`
@@ -34,122 +37,110 @@ LLM boundary types:
 - `validate.Validator`
 - optional `usecase.OutputRepairer`
 
-Transport concerns (CLI flags, HTTP DTO parsing, status-code mapping) stay outside runner.
+The CLI, HTTP adapter, and public Go package construct these dependencies and pass them in.
 
-## Config Fields Used
+## Config Fields
 
-`Runner` does not read app config files directly.
+`Runner` does not read app config files. Effective behavior is determined by injected dependencies and the `domain.RunRequest`.
 
-It receives fully constructed repositories/readers/validators from adapters. Effective behavior depends on adapter wiring, including:
+Adapter wiring commonly reflects these app config fields:
 
-- prompt/profile directories
+- `prompt_dir`
-- schema base directory
+- `profile_dir`
-- selected profile/runtime overrides in request
+- `schema_dir`
+- `server.artifact_root`
+- HTTP request/artifact/response size limits
 
-## External Adapters Used
+Runtime model settings are resolved from the selected profile plus request overrides.
-
-`Runner` works with adapter implementations via interfaces. Current wiring from CLI/HTTP uses:
-
-- filesystem prompt/profile repositories
-- composite artifact reader
-- Go-template prompt renderer
-- OpenAI-compatible LLM client
-- standard validator
-
-## State And Resume Behavior
-
-`Runner` is stateless across requests.
-
-- No durable run-state storage.
-- No built-in resume/skip checkpoints.
-- Each `Run`/`Prepare` executes from request inputs and current repositories.
-
-## Failure Behavior
-
-Primary runner error classes:
-
-- `ErrInvalidRequest`: invalid run request envelope.
-- `ErrProfileRequired`: specific invalid-request reason when neither request `profile_id` nor prompt `default_profile` is available.
-- `ErrAPIKeyEnvMissing`: specific invalid-request reason when `api_key_env` is set but the named environment variable is unset/empty.
-- `ErrProfileLoad`: prompt/profile repository load failures.
-- `ErrArtifactLoad`: artifact read failures.
-- `ErrPromptRender`: template render failures.
-- `ErrLLMGenerate`: outbound model request failures.
-- `ErrValidation`: validation runtime failures (including structured-output schema load/compile failures).
-
-Reason sentinel behavior:
-
-- `ErrProfileRequired` and `ErrAPIKeyEnvMissing` are wrapped with `ErrInvalidRequest`.
-- Adapters can use `errors.Is` for stable reason mapping without matching runner prose.
-
-Validation content failures are not run errors:
-
-- `Run` can succeed with `Validation.Status == failed`.
-- CLI maps this to exit code `2`.
-- HTTP returns `200` with failed validation details.
 
 ## Prepare Flow
 
-`Prepare` performs:
+`Prepare`:
 
-1. validate request basics (prompt ID present).
+1. requires a non-empty prompt ID.
-2. load prompt definition by ID/version.
+2. loads the prompt definition and computes its hash.
-3. select profile ID:
+3. selects the profile from request `profile_id`, then prompt `default_profile`.
-   - explicit request profile ID
+4. loads the selected execution profile.
-   - prompt `default_profile`
+5. merges built-in execution defaults, profile values, and request overrides.
-   - otherwise return an invalid request with `ErrProfileRequired`
+6. applies request-scoped direct API key values for public Go callers.
-4. load execution profile.
+7. validates endpoint, model, and credential requirements.
-5. merge effective runtime target:
+8. resolves the output contract and JSON Schema document when required.
-   - built-in execution defaults
+9. reads input artifacts.
-   - selected profile values
+10. renders prompt messages and hashes the rendered prompt.
-   - request overrides
+11. returns a prepared run without calling the LLM.
-6. verify required `api_key_env` environment variable:
-   - missing/empty env value returns an invalid request with `ErrAPIKeyEnvMissing`
-   - only the environment-variable name is retained; secret value is never returned
-7. resolve output contract and structured-output schema payload when `json_schema` mode is active.
-8. read input artifacts.
-9. render prompt messages.
-10. compute prompt/input/render hashes and return `PreparedRun`.
 
-`Prepare` does not call the LLM.
+Numeric request overrides are presence-aware: omitted values preserve the current effective value, while explicit zero values are real overrides.
 
 ## Run Flow
 
-`Run` performs:
+`Run`:
 
-1. generate run ID.
+1. creates a run ID and start timestamp.
-2. call `Prepare`.
+2. calls `Prepare`.
-3. call LLM with prepared messages/effective target/structured-output spec.
+3. calls the injected LLM client with rendered messages, effective target, target presence, and structured-output settings.
-4. build output artifact content type from output format.
+4. builds the output artifact.
-5. validate output.
+5. validates the output.
-6. optionally attempt bounded repair when repairer is injected and contract allows it.
+6. optionally attempts bounded repair when a repairer is injected and the contract permits repair.
-7. return `RunResult` with artifact, raw output, validation, hashes, profile/model metadata, usage, and timestamps.
+7. returns the run result with artifact, raw output, validation, hashes, selected profile/model metadata, usage, and timing.
 
-## Repair Hook Boundary
+`Run` must reuse `Prepare`; prepare logic should not be duplicated elsewhere.
 
-Repair attempts occur only when all are true:
+## Validation And Repair
 
-- repairer is injected
+Validation content failures are returned as successful run results with `Validation.Status == failed`. They are not runtime errors.
-- `repair_attempts > 0`
+
+Validation runtime failures, such as schema load or compile errors, return `ErrValidation`.
+
+Repair attempts occur only when all conditions are true:
+
+- a repairer is injected
+- `repair_attempts` is greater than zero
 - validation status is `failed`
 - validation mode is `json` or `json_schema`
 
-Current production wiring boundary:
+CLI and HTTP wiring call `usecase.NewRunner(...)`, which does not inject a repairer. Normal CLI and HTTP execution therefore does not repair invalid output.
 
-- CLI and HTTP adapters call `usecase.NewRunner(...)` (no repairer argument).
+## Failure Behavior
-- Therefore normal CLI/HTTP execution does not perform repair attempts today.
 
-## Tests To Inspect Before Changing
+Stable runner sentinels include:
+
+- `ErrInvalidRequest`
+- `ErrProfileRequired`
+- `ErrAPIKeyEnvMissing`
+- `ErrAPIKeyRequired`
+- `ErrPromptLoad`
+- `ErrProfileLoad`
+- `ErrArtifactLoad`
+- `ErrPromptRender`
+- `ErrLLMGenerate`
+- `ErrValidation`
+
+Adapters should use `errors.Is` against sentinels and lower-level repository errors instead of matching message text.
+
+Secret values must not appear in prepared output, run results, logs, HTTP responses, or serialized public package results. The effective API-key environment-variable name may appear.
+
+## State And Manifests
+
+The runner is stateless across requests.
+
+- No durable run store.
+- No manifest files.
+- No checkpoint, skip, or resume behavior.
+- Recovery is a new request after correcting inputs, config, or environment.
+
+## Tests To Inspect
 
 - `internal/usecase/runner_test.go`
 - `internal/usecase/integration_test.go`
+- `engine_test.go`
 - `internal/adapter/cli/run_test.go`
 - `internal/adapter/http/handler_test.go`
 
 ## Architectural Invariants
 
-- `Run` reuses `Prepare`; prepare logic is not duplicated.
+- Use-case decisions stay in `internal/usecase`.
-- Effective API-key environment-variable name may appear; resolved secret value must not.
+- `Run` reuses `Prepare`.
-- Structured-output schema document must load before LLM call for `json_schema` mode.
+- Prompt/profile/artifact/schema loading remains behind injected boundaries.
+- Validation content failures are result state; validation runtime failures are errors.
 - Repair loops are bounded by `repair_attempts` and repairer presence.
-- Runner stays transport-agnostic.
+- Resolved secret values are never serialized or emitted.

docs/internal/sources.md

@@ -0,0 +1,157 @@
+# Source Internals
+
+## Purpose
+
+This document covers implemented prompt, profile, schema, artifact, and catalog source behavior. It is for developers changing loaders or source wiring.
+
+Full user-facing YAML and config reference material belongs in `docs/config.md`.
+
+## Prompt Definition Sources
+
+`internal/promptdef` provides directory-backed and `fs.FS` repositories.
+
+Behavior:
+
+- recursively scans `.yaml` and `.yml` files.
+- decodes YAML with known-fields checking.
+- looks up prompts by YAML `id`, not by path.
+- optionally filters by prompt `version`.
+- rejects duplicate matching prompt IDs.
+- requires `id`, `version`, and at least one message.
+- requires each message to set exactly one of `content` or `content_file`.
+- resolves filesystem `content_file` values relative to the prompt YAML file.
+- resolves `fs.FS` `content_file` values inside the configured source root.
+- permits prompt subdirectories only as organization; they are not part of prompt identity.
+
+For `fs.FS` roots, absolute paths and relative traversal outside the source root are rejected by catalog path helpers.
+
+## Profile Sources
+
+`internal/profile` provides directory-backed, `fs.FS`, and overlay repositories. `internal/profile/builtin` embeds built-in profile YAML assets and exposes them through the same repository interface.
+
+Behavior:
+
+- recursively scans `.yaml` and `.yml` files.
+- decodes YAML with known-fields checking.
+- looks up profiles by YAML `id`, not by path.
+- rejects duplicate IDs inside the same source.
+- rejects raw `api_key` fields in YAML; file-backed profiles must use `api_key_env`.
+- validates required `endpoint` and `model` values.
+- validates numeric profile ranges.
+
+Overlay behavior:
+
+- custom profiles are primary.
+- built-in profiles are fallback.
+- fallback occurs only after a primary `ErrProfileNotFound`.
+- primary validation, YAML, duplicate, and raw-key errors are returned directly.
+- duplicate IDs across custom and built-in sources are allowed because the custom profile overrides the built-in one.
+
+The public Go facade can add in-memory profiles ahead of file-backed and built-in profiles.
+
+## Schema Sources
+
+`internal/validate` provides:
+
+- `StandardValidator` for filesystem paths.
+- `FSValidator` for `fs.FS` roots and single-file public schema sources.
+
+Behavior:
+
+- `json_schema` validation requires a non-empty `schema_path`.
+- filesystem schema paths resolve relative to `schema_dir` unless absolute.
+- directory-backed schema lookup uses the explicit `schema_path`; it does not search recursively by basename.
+- `fs.FS` schema paths must remain inside the configured source root.
+- single-file schema sources match by the configured file base name.
+- schema documents are loaded before the LLM call for structured output.
+- JSON parse failures are validation content failures.
+- schema access, decode, registration, and compile failures are runtime validation errors.
+
+## Artifact Sources
+
+`internal/artifact` supports two input artifact reference types:
+
+- `inline`
+- `file`
+
+Inline behavior:
+
+- requires a non-empty body.
+- produces text/plain artifacts.
+- hashes the body bytes.
+
+Direct file behavior:
+
+- used by CLI `run`, CLI `render`, and the public Go facade.
+- requires a non-empty URI.
+- reads from the process filesystem without HTTP artifact-root restrictions.
+- infers content type from file extension, defaulting to text/plain.
+
+Restricted file behavior:
+
+- used by HTTP `serve`.
+- allows inline artifacts even when no artifact root is configured.
+- denies file artifacts when no artifact root is configured.
+- resolves relative file URIs against `server.artifact_root`.
+- accepts absolute file URIs only when they pass containment checks.
+- applies `server.max_artifact_bytes` when configured.
+
+Restricted containment is lexical. It cleans paths and checks the relative path against the configured root; it does not resolve symlinks. Symlinks inside the root are followed by the operating system, including symlinks that target files outside the root.
+
+## Catalog Helpers
+
+`internal/filecatalog` centralizes shared source helpers:
+
+- recursive YAML discovery for filesystem and `fs.FS` roots.
+- deterministic sorting.
+- `.yaml` and `.yml` filtering.
+- display paths for diagnostics.
+- YAML file stems.
+- `fs.FS` root cleaning and containment checks.
+
+Repository code should use these helpers instead of reimplementing path traversal and containment rules.
+
+## Failure Behavior
+
+Common source failures:
+
+- missing prompt/profile/schema/artifact files.
+- invalid YAML or JSON.
+- unknown YAML fields.
+- duplicate prompt or profile IDs.
+- prompt/profile validation errors.
+- raw API key fields in profile YAML.
+- unsupported artifact reference type.
+- missing inline body or file URI.
+- artifact outside HTTP root.
+- artifact exceeding HTTP size limit.
+- schema load or compile failure.
+
+Prompt/profile repository lookup errors are mapped by adapters separately from runtime runner errors. Validation content failures remain result state; source and schema runtime failures return errors.
+
+## State And Manifests
+
+Source packages do not persist run state.
+
+- No manifests are read or written.
+- No source package implements skip or resume behavior.
+- Source reads reflect the current filesystem or `fs.FS` state for each request.
+
+## Tests To Inspect
+
+- `internal/promptdef/repository_test.go`
+- `internal/profile/repository_test.go`
+- `internal/profile/builtin/repository_test.go`
+- `internal/artifact/reader_test.go`
+- `internal/validate/standard_validator_test.go`
+- `internal/usecase/integration_test.go`
+- `engine_test.go`
+
+## Architectural Invariants
+
+- Prompt/profile identity comes from YAML `id`.
+- External YAML decoding remains strict.
+- File-backed profile YAML never accepts raw API key values.
+- Built-in profiles are fallback, not a replacement for custom source validation.
+- HTTP file artifacts remain rooted by lexical containment.
+- Schema runtime failures remain errors, while JSON/schema content mismatches remain validation results.

docs/operations.md

@@ -2,124 +2,163 @@
 
 ## Scope
 
-This document covers day-to-day operation of the CLI and HTTP service for currently implemented behavior.
+This guide covers operating the implemented CLI commands and HTTP service. It
-
+does not replace the [CLI reference](cli.md), [Configuration reference](config.md),
-For command syntax, see [CLI reference](cli.md). For file formats and defaults, see [Configuration reference](config.md).
+or [HTTP API reference](api.md).
 
 ## Operational Model
 
-Scriptorium executes one request at a time per CLI invocation or HTTP request.
+Scriptorium executes one prompt request per CLI invocation or HTTP request.
 
 Important boundaries:
 
 - No durable run state is stored.
-- No built-in resume, checkpoint, archive, or backup workflow exists.
+- No manifest, archive, checkpoint, or built-in backup workflow is written.
-- Recovery is rerun-based: fix inputs/config, then rerun.
+- No built-in resume behavior exists.
+- Recovery is rerun-based: correct inputs, config, or environment, then run again.
 
-## Filesystem Layout And Config
+## Filesystem Layout
 
-Scriptorium depends on:
+Operational deployments usually provide:
 
-- prompt definition files (`prompt_dir`)
+- `prompt_dir`: prompt definition YAML files and adjacent `content_file` templates.
-- execution profile files (`profile_dir`)
+- `profile_dir`: optional custom profile YAML files.
-- optional JSON schemas (`schema_dir`)
+- `schema_dir`: optional JSON Schema files.
+- `server.artifact_root`: optional HTTP file-input root for `serve`.
 
-Config discovery order when `--config` is omitted:
+Keep these directories readable by the Scriptorium process. Keep
-
+`server.artifact_root` narrow and not writable by untrusted users.
-1. `/usr/local/etc/scriptorium/config.yml`
-2. `/etc/scriptorium/config.yml`
-
-If neither exists, built-in defaults are used. If `--config <path>` is provided, that file must exist and parse successfully.
-
-Built-in defaults relevant to operations:
-
-- `schema_dir: .`
-- `server.addr: :8080`
-- `defaults.render_format: text`
 
 ## Normal CLI Workflow
 
-Use `render` first when you need to verify prompt resolution and runtime settings without calling a model.
+Use `render` before `run` when changing prompt/profile/input wiring:
 
-Use `run` for generation.
+```bash
+go run ./cmd/scriptorium render \
+  --config ./examples/config.yml \
+  --prompt generic.markdown_summary \
+  --input transcript=./examples/fixtures/transcript.md \
+  --input glossary=./examples/fixtures/glossary.yml \
+  --format json
+```
 
-Typical sequence:
+Use `run` for generation after preflight:
 
-1. Confirm prompt/profile directories resolve through config or flags.
+```bash
-2. Confirm required input files exist and map to prompt input names.
+go run ./cmd/scriptorium run \
-3. Confirm required API-key environment variables are set.
+  --config ./examples/config.yml \
-4. Confirm the selected profile's model endpoint is reachable from the process environment.
+  --prompt generic.markdown_summary \
-5. Run `render` for preflight when changing prompt/profile/input wiring.
+  --input transcript=./examples/fixtures/transcript.md \
-6. Run `run` for actual generation.
+  --input glossary=./examples/fixtures/glossary.yml \
+  --out ./summary.md
+```
 
-## Secrets Handling
+Before production runs, confirm:
 
-Raw API keys are not accepted in config files, profile files as `api_key`, CLI flags, or HTTP request bodies.
+- the effective config path is the intended one;
-
+- prompt/profile/schema directories are readable;
-Operational pattern:
+- input file paths exist and match prompt input names;
-
+- required API-key environment variables are set;
-- Set environment variables that hold secret values.
+- the selected model endpoint is reachable from the process environment.
-- Set profile `api_key_env` (or runtime override `api_key_env`) to the environment variable name.
-- Keep process environments scoped to only required variables.
 
 ## HTTP Service Operation
 
-Start service with:
+Start the service with:
 
 ```bash
 go run ./cmd/scriptorium serve --config ./examples/config.yml
 ```
 
-Current inbound API behavior:
+The implemented HTTP route is `POST /v1/runs`; request and response fields are
+defined in the [HTTP API reference](api.md).
 
-- Route: `POST /v1/runs`
+The maintained HTTP request-shape example is `examples/http-run.json`.
-- JSON request parsing rejects unknown fields.
-- Validation content failures still return `200 OK` with `validation.status: "failed"`.
 
-Security caveat:
+HTTP service notes:
+
+- Unknown JSON fields are rejected.
+- `inline` input references work without an artifact root.
+- `file` input references require `server.artifact_root` or `serve --artifact-root`.
+- Request bodies, HTTP file input artifacts, and encoded JSON responses are size-limited.
+- Validation content failures return `200 OK` with `validation.status: "failed"`.
+
+Security boundary:
 
 - `serve` has no built-in authentication or authorization.
-- Deploy only behind trusted controls (private network boundary, authenticated reverse proxy, API gateway, or equivalent).
+- Put it behind trusted controls such as a private network, authenticated reverse proxy, or API gateway.
+- Do not expose an artifact root containing unrelated sensitive files.
+- Symlinks inside the artifact root are followed by the operating system.
+
+## Secrets Handling
+
+Raw API keys are not accepted in app config, profiles, CLI flags, or HTTP
+request bodies.
+
+Use this pattern:
+
+1. Set an environment variable containing the secret value.
+2. Store only the variable name in profile `api_key_env` or request override `api_key_env`.
+3. Scope the process environment to the minimum required variables.
 
 ## Output, Logs, And Exit Codes
 
-`run` command:
+`run`:
 
-- Generated artifact body goes to stdout by default.
+- stdout: generated artifact body unless `--out` is used.
-- `--out` writes generated artifact to a file.
+- stderr: summary on success, errors on failure.
-- Summary metadata line is written to stderr on success.
+- exit `2`: generation completed and output was written, but validation failed.
-- Exit code `2` means generation completed but validation failed.
 
-`render` command:
+`render`:
 
-- Prepared-run output goes to stdout by default.
+- stdout: prepared-run output unless `--out` is used.
-- `--out` writes prepared-run output to a file.
+- stderr: errors.
-- Exit code is `0` on success and `1` on failure.
+- exit `0` on success, `1` on failure.
 
-`serve` command:
+`serve`:
 
-- Startup and server errors are written to stderr.
+- stderr: startup and server errors.
+- HTTP response body: JSON success or error envelope.
 
-## Validation Behavior In Operations
+## Validation Behavior
 
-Validation modes (`none`, `basic`, `json`, `json_schema`) are defined by prompt output contract.
+Prompt `output.validation_mode` controls validation:
 
-Operational interpretation:
+- `none`: skipped.
+- `basic`: output body must not be empty.
+- `json`: output body must parse as JSON.
+- `json_schema`: output body must parse as JSON and satisfy the configured schema.
 
-- Validation runtime errors are hard failures (`run` exit `1`; HTTP error response).
+Runtime/schema failures are hard failures (`run` exit `1`, HTTP error).
-- Validation content failures are soft failures (`run` exit `2`; HTTP `200` with failed status).
+Generated-content validation failures are soft failures (`run` exit `2`, HTTP
+`200 OK` with failed validation status).
 
-A failed validation run can still produce output. Decide whether to keep or discard that output in your surrounding workflow.
+## Size Limits
 
-## Safe Recovery Steps
+Defaults are documented in [Configuration reference](config.md). Operationally:
 
-For failed runs or requests:
+- Keep default HTTP limits unless larger payloads are measured and expected.
+- Prefer `inline` HTTP inputs for small payloads.
+- Prefer `file` HTTP inputs for larger local artifacts under a controlled artifact root.
+- Increase `server.max_response_bytes` when generated artifacts or requested raw output are expected to be large.
+- Use `0` only when another trusted layer enforces size limits.
 
-1. Capture stderr output or HTTP error code/message.
+## Maintained Examples
-2. Confirm config path and directory settings.
+
-3. Verify prompt/profile IDs and input mappings.
+- `examples/config.yml`
-4. Verify API-key environment-variable presence when required.
+- `examples/config.full.yml`
-5. Reproduce with `render --format json` when prompt/profile/input resolution is uncertain.
+- `examples/render-markdown-summary.sh`
+- `examples/http-run.json`
+
+## Safe Recovery
+
+For failed CLI commands or HTTP requests:
+
+1. Capture stderr or the HTTP error `code` and `message`.
+2. Confirm config path and effective directory settings.
+3. Verify prompt ID, profile ID, schema path, and input mappings.
+4. Verify required API-key environment variables.
+5. Reproduce with `render --format json` when pre-LLM resolution is uncertain.
 6. Rerun after correction.
 
-Because Scriptorium does not persist run state, rerun is the canonical recovery path.
+Because Scriptorium does not persist run state, rerun is the supported recovery
+path.

docs/policy/architecture.md

@@ -11,6 +11,7 @@ Scriptorium is a narrow prompt-execution application with three entry paths:
 - CLI `run`
 - CLI `render`
 - HTTP `POST /v1/runs` through `serve`
+- public Go package `gitea.maximumdirect.net/eric/scriptorium`
 
 Domain behavior is centralized in `internal/usecase` and `internal/domain`.
 
@@ -26,6 +27,7 @@ Domain behavior is centralized in `internal/usecase` and `internal/domain`.
 
 Current package map:
 
+- root package `scriptorium`: public Go facade over engine construction, source options, request/result types, and error mapping.
 - `cmd/scriptorium`: process entrypoint.
 - `internal/adapter/cli`: command parsing, app wiring for CLI commands, output behavior.
 - `internal/adapter/http`: HTTP DTO mapping and error/status mapping.
@@ -34,7 +36,9 @@ Current package map:
 - `internal/domain`: core request/result and contract types.
 - `internal/usecase`: `Runner` prepare/run orchestration and repair-hook boundary.
 - `internal/promptdef`: filesystem prompt-definition repository.
-- `internal/profile`: filesystem execution-profile repository.
+- `internal/profile`: filesystem, `fs.FS`, and overlay execution-profile repositories.
+- `internal/profile/builtin`: embedded built-in execution profiles.
+- `internal/filecatalog`: shared YAML discovery and `fs.FS` source helpers.
 - `internal/artifact`: artifact reference readers.
 - `internal/prompt`: template renderer.
 - `internal/llm`: provider-neutral LLM client interface and OpenAI-compatible implementation.
@@ -45,6 +49,7 @@ Detailed component behavior is documented in:
 
 - `docs/internal/runner.md`
 - `docs/internal/adapters.md`
+- `docs/internal/sources.md`
 
 ## Configuration And Precedence
 
@@ -69,9 +74,10 @@ Scriptorium has no durable run-state store.
 
 Current external contracts:
 
-- inbound HTTP contract: `POST /v1/runs`
+- inbound HTTP contract: `POST /v1/runs`, documented canonically in `docs/api.md`
 - outbound model contract: OpenAI-compatible chat completions subset
 - subprocess contract for integrators: CLI `run`/`render`
+- public Go package contract: `docs/consumers/pkg-scriptorium.md`
 
 Integration docs belong under `docs/integrations/`.
 

docs/policy/development.md

@@ -4,6 +4,7 @@ This document defines contributor workflow for Scriptorium.
 
 ## Repository Layout
 
+- root package `scriptorium`: public Go facade, options, types, and error mapping.
 - `cmd/scriptorium`: application entrypoint.
 - `internal/domain`: core contracts.
 - `internal/usecase`: runner orchestration.
@@ -13,6 +14,8 @@ This document defines contributor workflow for Scriptorium.
 - `internal/defaults`: default constants.
 - `internal/promptdef`: prompt-definition repository.
 - `internal/profile`: execution-profile repository.
+- `internal/profile/builtin`: embedded built-in execution profiles.
+- `internal/filecatalog`: shared source discovery and path helpers.
 - `internal/artifact`: artifact readers.
 - `internal/prompt`: prompt rendering.
 - `internal/llm`: LLM client interface and OpenAI-compatible implementation.
@@ -38,7 +41,9 @@ go test ./...
 Targeted test runs commonly used during changes:
 
 ```bash
+go test .
 go test ./internal/adapter/cli ./internal/adapter/http ./internal/usecase
+go test ./internal/...
 ```
 
 ## Coding Conventions
@@ -82,7 +87,8 @@ go test ./internal/adapter/cli ./internal/adapter/http ./internal/usecase
 3. Keep business decisions in `internal/usecase`.
 4. Add focused adapter tests for mapping, parse, and error behavior.
 5. Document the new/changed boundary in `docs/internal/adapters.md`.
-6. If external contract changes, update `docs/integrations/` in the same change.
+6. If source-loading behavior changes, update `docs/internal/sources.md`.
+7. If an external contract changes, update the canonical public or integration doc in the same change.
 
 ## How To Update Prompt/Profile/Schema Assets
 
@@ -99,5 +105,6 @@ When behavior changes:
 2. Keep non-roadmap docs limited to implemented behavior.
 3. Update links after file moves/renames.
 4. Re-run relevant tests and smoke commands.
+5. For internal boundary docs, check references with `rg "docs/internal|internal/sources" docs/policy docs/internal`.
 
 Docs work is complete only when code/tests/examples/docs agree.

docs/policy/documentation.md

@@ -2,12 +2,13 @@
 
 ## Purpose
 
-Project documentation must help four audiences:
+Project documentation must help five audiences:
 
 1. users who need to run the application;
 2. administrators/operators who need to configure and operate it;
 3. developers who need to understand and change it safely;
-4. LLM coding agents that need clear scope, boundaries, and invariants.
+4. LLM coding agents that need clear scope, boundaries, and invariants;
+5. developers and LLM coding agents integrating this project from another codebase.
 
 Docs should be accurate, concise, task-oriented, and organized by audience. Prefer links to canonical docs over repetition.
 
@@ -42,11 +43,14 @@ Canonical homes:
 
 - project purpose and quickstart: `README.md`
 - development principles: `docs/policy/architecture.md`
+- public HTTP API reference: `docs/api.md`
 - configuration reference: `docs/config.md`
 - CLI reference: `docs/cli.md`
 - operations and recovery: `docs/operations.md`
 - troubleshooting: `docs/troubleshooting.md`
+- public API/package consumer guidance: `docs/consumers/`
 - implemented internals: `docs/internal/`
+- external protocol, service, and file-format contracts: `docs/integrations/`
 - future work: `docs/roadmap/`
 - contributor workflow: `docs/policy/development.md`
 - copyable examples: `examples/`
@@ -106,7 +110,7 @@ Recommended:
 - `examples/`
 - `docs/policy/development.md`
 
-### Modular, staged, service-oriented, or orchestration application
+### Modular, service-oriented, or orchestration application
 
 Required:
 - `docs/cli.md`, if CLI-based
@@ -119,6 +123,31 @@ Recommended:
 - `docs/troubleshooting.md`
 - validated examples under `examples/`
 
+### Public HTTP API service
+
+Required:
+- `docs/api.md`
+- `docs/cli.md`, if CLI-based
+- `docs/config.md`, if config-driven
+- `docs/operations.md`
+- `docs/internal/`
+- `docs/policy/development.md`
+
+Recommended:
+- `docs/troubleshooting.md`
+- `docs/consumers/`, for task-oriented client integration guides
+- `docs/integrations/`, for upstream/downstream service contracts
+- validated examples under `examples/`
+
+### Project with public packages or consumer APIs
+
+Required:
+- `docs/consumers/api.md`
+- one `docs/consumers/pkg-<name>.md` file per public package, if public packages exist
+
+Recommended:
+- copyable consumer examples under `examples/`, if practical
+
 ## Required Documents
 
 ### README.md
@@ -159,7 +188,35 @@ It should include:
 - architectural invariants;
 - explicit non-goals, if useful.
 
-For small projects, this file may be brief. It may simply state that the project is intentionally narrow, monolithic, and dependency-light.
+Notably, this file should prescribe a core development *policy* that should remain unchanged as the application evolves. It is not a place for details (e.g., CLI flags) that could change over time.
+
+The contents of `architecture.md` should be trim and concise. LLMs may be directed to review it routinely via AGENTS.md, CLAUDE.md, or similar.
+
+### docs/api.md
+
+**Audience:** external HTTP API consumers, developers, LLM coding agents integrating by HTTP
+
+Required for projects whose primary public interface is HTTP.
+
+`docs/api.md` is the canonical public HTTP API contract. It should be normative for external consumers and should not be duplicated by README, operations docs, consumer guides, or integration docs.
+
+It should include:
+
+1. base URL conventions;
+2. authentication and authorization behavior, if implemented;
+3. response envelope;
+4. supported media types and content negotiation behavior;
+5. shared query parameters;
+6. endpoint reference grouped by route family;
+7. request parameters and validation rules;
+8. response fields, units, nullability, and optionality;
+9. error response shape and status codes;
+10. pagination, caching, rate-limit, idempotency, and retry behavior, if implemented;
+11. compact request and response examples.
+
+It must document only implemented endpoints and behavior. Planned endpoints, proposed fields, future filters, and experimental response shapes belong only under `docs/roadmap/`.
+
+For HTTP API projects, `docs/consumers/` may provide task-oriented client integration guides, but those guides should link to `docs/api.md` for the authoritative endpoint contract.
 
 ### docs/policy/development.md
 
@@ -175,7 +232,7 @@ It should include:
 - dependency policy;
 - how to add config fields;
 - how to add CLI flags;
-- how to add stages/modules/adapters, if applicable;
+- how to add modules or adapters, if applicable;
 - how to update examples;
 - documentation update expectations.
 
@@ -216,7 +273,7 @@ Explain when commands are useful, not just their syntax.
 
 **Audience:** administrators, operators
 
-Required for applications that maintain state, support resume behavior, run multiple stages, write durable artifacts, use remote storage, or require recovery procedures.
+Required for applications that maintain state, support resume behavior, run multi-step workflows, write durable artifacts, use remote storage, or require recovery procedures.
 
 It should cover:
 
@@ -244,11 +301,40 @@ Each entry should include:
 - safe fix;
 - relevant links.
 
+### docs/consumers/
+
+**Audience:** developers and LLM coding agents integrating this project from another codebase
+
+Required for projects with public packages, SDKs, client APIs, plugin APIs, or other application-facing integration surfaces.
+
+This directory describes how an external codebase should consume the project's public API. It should be task-oriented and copyable where useful. It is not the place for internal implementation details or operator procedures.
+
+For projects whose public API is HTTP, `docs/consumers/` is not required, and it should not duplicate the endpoint reference in `docs/api.md`. If present, it may provide practical integration workflows, client-specific examples, or migration notes that link back to `docs/api.md`.
+
+`docs/consumers/api.md` should provide the consumer-facing overview and primary implementation workflow. It should include:
+
+1. intended consumer audience and use cases;
+2. required inputs supplied by operators or deployment configuration;
+3. recommended public package or API workflow;
+4. minimal copyable example;
+5. consumer responsibilities and boundaries;
+6. retry, idempotency, or status behavior, if applicable;
+7. links to package-specific docs and canonical integration contracts.
+
+Package-specific docs should be named `pkg-<name>.md` and should include:
+
+1. import path;
+2. intended use cases;
+3. primary types and functions needed by consumers;
+4. minimal examples;
+5. validation, error, retry, and boundary behavior;
+6. links to canonical file-format or wire-protocol contracts.
+
 ### docs/internal/
 
 **Audience:** developers, LLM coding agents
 
-Required for modular, staged, service-oriented, or orchestration projects.
+Required for modular, service-oriented, or orchestration projects.
 
 This directory describes implemented internal components. It is not the roadmap.
 
@@ -289,7 +375,9 @@ Roadmap docs should not be confused with current behavior.
 
 Required for projects that depend on external CLIs, APIs, services, protocols, or file formats where the integration contract is important to maintain.
 
-This directory contains concise, versioned reference notes for external integration contracts. It should document only the parts of the external system that this project actually uses.
+This directory contains concise, versioned reference notes for external integration contracts. It should document only the parts of the external system that this project actually uses or exposes.
+
+For public HTTP API services, `docs/integrations/` should document upstream, downstream, storage, protocol, or runtime contracts that the service depends on or bridges. It should not become a second copy of the public HTTP endpoint reference; that belongs in `docs/api.md`.
 
 Use one file per integration where useful.
 
@@ -346,8 +434,10 @@ Before merging documentation changes, verify:
 
 - README is concise and orientation-focused.
 - `docs/policy/architecture.md` describes development principles.
+- `docs/api.md` is the canonical HTTP contract for HTTP API services.
 - Future work appears only under `docs/roadmap/`.
 - User-facing docs avoid unnecessary internals.
+- Consumer-facing docs explain public APIs without duplicating HTTP endpoint or integration contracts.
 - Developer-facing docs preserve boundaries and invariants.
 - Config examples match the schema.
 - CLI examples match real commands and flags.

docs/troubleshooting.md

@@ -1,19 +1,25 @@
 # Troubleshooting
 
-This guide lists recurring implemented failure modes and safe fixes.
+This guide lists common implemented failure modes and safe fixes.
 
-For command syntax, see [CLI reference](cli.md). For configuration and file formats, see [Configuration reference](config.md). For operational behavior, see [Operations guide](operations.md).
+Canonical references:
 
-## Missing Or Invalid Config File
+- [CLI reference](cli.md)
+- [Configuration reference](config.md)
+- [HTTP API reference](api.md)
+- [Operations guide](operations.md)
+
+## Missing Or Invalid Config
 
 Symptom:
 
-- CLI errors such as `application config error: config file not found` or `invalid config YAML`.
+- CLI error includes `application config error`, `config file not found`, `invalid config YAML`, or `invalid config`.
 
 Likely cause:
 
 - `--config` points to a missing file.
-- Config YAML has syntax errors or unknown fields.
+- YAML syntax is invalid.
+- Config contains unknown fields or negative HTTP size limits.
 
 Diagnostic step:
 
@@ -23,40 +29,34 @@ go run ./cmd/scriptorium render --config /path/to/config.yml --prompt generic.ma
 
 Safe fix:
 
-- Correct file path.
+- Correct the config path.
-- Remove unknown fields.
 - Fix YAML syntax.
-- Keep secrets out of config.
+- Remove unknown fields.
+- Keep raw secrets out of config.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [CLI reference](cli.md)
 
-- [Configuration reference](config.md)
+## Missing Prompt Directory
-- [CLI reference](cli.md)
-
-## Missing Prompt/Profile Directory Settings
 
 Symptom:
 
-- CLI parse errors saying prompt directory or profile directory is required.
+- CLI parse error says the prompt directory is required.
 
 Likely cause:
 
-- Neither CLI flags nor config provide effective `prompt_dir` / `profile_dir`.
+- Neither config nor CLI flags provide an effective `prompt_dir`.
 
 Diagnostic step:
 
-- Run the failing command with explicit `--prompt-dir` and `--profile-dir` once to verify.
+- Re-run once with explicit `--prompt-dir`.
 
 Safe fix:
 
-- Set `prompt_dir` and `profile_dir` in config, or always pass both flags.
+- Set `prompt_dir` in config or pass `--prompt-dir`.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [CLI reference](cli.md)
 
-- [Configuration reference](config.md)
+## Unknown Flags
-- [CLI reference](cli.md)
-
-## Unknown Or Unsupported Flags
 
 Symptom:
 
@@ -64,33 +64,33 @@ Symptom:
 
 Likely cause:
 
-- Typo or command mismatch (for example, `serve` with runtime model override flags).
+- Typo.
+- Flag is valid for another command.
+- `serve` was given runtime model override flags.
 
 Diagnostic step:
 
-- Compare command against the command-specific flag list.
+- Compare the command with the command-specific flag list.
 
 Safe fix:
 
 - Remove unsupported flags.
-- Use `run`/`render` for runtime model overrides.
+- Use `run` or `render` for runtime model overrides.
 
-Relevant links:
+Relevant links: [CLI reference](cli.md)
 
-- [CLI reference](cli.md)
+## Prompt Load Failures
-
-## Prompt Definition Load Failures
 
 Symptom:
 
-- CLI run/render error from prompt loading.
+- CLI run/render fails during prompt loading.
-- HTTP `404 prompt_not_found` or `400 prompt_load_failed`.
+- HTTP returns `404 prompt_not_found` or `400 prompt_load_failed`.
 
 Likely cause:
 
-- Prompt ID not found.
+- Prompt ID/version does not exist.
-- Invalid prompt YAML.
+- Prompt YAML is invalid or has unknown fields.
-- Invalid prompt contract (for example bad validation mode, message content/content_file rule violation, missing schema path for `json_schema`).
+- Prompt contract is invalid, such as missing messages, invalid output mode, bad `content_file`, or missing `schema_path` for `json_schema`.
 
 Diagnostic step:
 
@@ -100,28 +100,25 @@ go run ./cmd/scriptorium render --config ./examples/config.yml --prompt <prompt-
 
 Safe fix:
 
-- Correct prompt ID.
+- Correct prompt ID/version.
-- Fix prompt YAML and contract fields.
+- Fix prompt YAML and referenced `content_file` paths.
-- Ensure referenced `content_file` paths exist.
+- Fix output contract fields.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [CLI reference](cli.md)
 
-- [Configuration reference](config.md)
+## Profile Load Failures
-- [CLI reference](cli.md)
-
-## Profile Definition Load Failures
 
 Symptom:
 
-- CLI run/render error from profile loading.
+- CLI run/render fails during profile loading.
-- HTTP `404 profile_not_found` or `400 profile_load_failed`.
+- HTTP returns `404 profile_not_found`, `400 profile_load_failed`, or `400 profile_required`.
 
 Likely cause:
 
-- Profile ID missing/not found.
+- Profile ID does not exist.
-- Invalid profile YAML.
+- Request omitted profile and prompt has no `default_profile`.
-- Invalid profile values.
+- Profile YAML is invalid or has unknown fields.
-- Raw `api_key` field present (rejected).
+- Profile contains raw `api_key`.
 
 Diagnostic step:
 
@@ -131,78 +128,52 @@ go run ./cmd/scriptorium render --config ./examples/config.yml --prompt generic.
 
 Safe fix:
 
-- Correct profile ID.
+- Correct profile ID or prompt `default_profile`.
 - Fix profile YAML and value ranges.
-- Replace `api_key` with `api_key_env`.
+- Replace raw `api_key` with `api_key_env`.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [CLI reference](cli.md)
 
-- [Configuration reference](config.md)
+## Input Artifact Failures
-- [CLI reference](cli.md)
-
-## Input Artifact Read Failures
 
 Symptom:
 
-- CLI run/render error reading input artifacts.
+- CLI run/render fails while reading inputs.
-- HTTP `400 artifact_read_failed`.
+- HTTP returns `400 artifact_read_failed`, `400 artifact_not_allowed`, or `413 artifact_too_large`.
 
 Likely cause:
 
-- File path in input mapping does not exist or is unreadable.
+- Input file path is missing or unreadable.
-- Unsupported artifact reference type in HTTP request.
+- HTTP input type is unsupported or missing required fields.
+- HTTP file refs are disabled because no artifact root is configured.
+- HTTP file path is lexically outside the artifact root.
+- HTTP file input exceeds `server.max_artifact_bytes`.
 
 Diagnostic step:
 
-- Verify every mapped file path exists and is readable by the process.
+- Verify each input path exists and is readable by the process.
-- For HTTP, verify each input uses supported `type` values.
+- For HTTP, verify input refs use `file` or `inline`.
+- For HTTP file refs, verify the artifact root and compare file size to `server.max_artifact_bytes`.
 
 Safe fix:
 
-- Correct file paths and permissions.
+- Correct paths and permissions.
-- Use supported input types (`file`, `inline`).
+- Configure a narrow artifact root for HTTP file refs.
+- Use relative paths under the artifact root or switch to `inline`.
+- Increase `server.max_artifact_bytes` only for expected larger inputs.
 
-Relevant links:
+Relevant links: [HTTP API reference](api.md), [Configuration reference](config.md)
-
-- [CLI reference](cli.md)
-- [Configuration reference](config.md)
-
-## Prompt Template Render Failures
-
-Symptom:
-
-- CLI run/render error from prompt rendering.
-- HTTP `400 prompt_render_failed`.
-
-Likely cause:
-
-- Template references missing input names.
-- Template syntax or data reference issues.
-
-Diagnostic step:
-
-- Run `render --format json` with the same prompt, inputs, vars, and profile selection.
-
-Safe fix:
-
-- Align template `{{input "name"}}` references with actual input mappings.
-- Fix template syntax and variable names.
-
-Relevant links:
-
-- [CLI reference](cli.md)
-- [Configuration reference](config.md)
 
 ## Missing API-Key Environment Variable
 
 Symptom:
 
-- CLI run/render invalid request error about missing API-key environment variable.
+- CLI render/run fails with an API-key environment error.
-- HTTP `400 api_key_env_missing`.
+- HTTP returns `400 api_key_env_missing`.
 
 Likely cause:
 
-- Selected profile or override sets `api_key_env`, but that environment variable is unset/empty.
+- Selected profile or runtime override sets `api_key_env`, but the environment variable is unset or empty.
 
 Diagnostic step:
 
@@ -212,52 +183,68 @@ printenv SCRIPTORIUM_API_KEY
 
 Safe fix:
 
-- Set the required environment variable before invoking CLI/service.
+- Set the required environment variable before starting the CLI command or HTTP service.
-- Or use a profile that does not require API key auth for the target endpoint.
+- Or use a profile that does not require provider API-key auth.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [Operations guide](operations.md)
 
-- [Configuration reference](config.md)
+## Prompt Template Render Failures
-- [Operations guide](operations.md)
+
+Symptom:
+
+- CLI render/run fails during prompt rendering.
+- HTTP returns `400 prompt_render_failed`.
+
+Likely cause:
+
+- Template references an input that was not supplied.
+- Template syntax or variable reference is invalid.
+
+Diagnostic step:
+
+- Run `render --format json` with the same prompt, inputs, vars, and profile.
+
+Safe fix:
+
+- Align `{{input "name"}}` references with request input names.
+- Fix template syntax and variable names.
+
+Relevant links: [Configuration reference](config.md), [CLI reference](cli.md)
 
 ## LLM Request Failures
 
 Symptom:
 
-- CLI `run` fails with LLM generation errors.
+- CLI `run` fails during generation.
 - HTTP returns `502 llm_failed`.
 
 Likely cause:
 
-- Endpoint unreachable.
+- Endpoint is unreachable.
-- Non-2xx response from provider.
+- Provider returns non-2xx.
-- Timeout.
+- Request times out.
-- Malformed provider response.
+- Provider response is malformed.
 
 Diagnostic step:
 
-- Confirm endpoint URL and model in selected profile/overrides.
+- Run `render` first to confirm pre-LLM preparation works.
-- Retry with `render` first to confirm pre-LLM preparation works.
+- Check selected endpoint/model in prepared output.
-- Check provider/network logs for non-2xx responses and timeouts.
+- Check network/provider logs for timeout or non-2xx details.
 
 Safe fix:
 
-- Correct endpoint/model settings.
+- Correct endpoint/model/profile settings.
-- Adjust timeout if needed.
+- Adjust timeout when appropriate.
-- Resolve provider-side or network issues.
+- Resolve provider or network issue.
 
-Relevant links:
+Relevant links: [Operations guide](operations.md), [Configuration reference](config.md)
 
-- [CLI reference](cli.md)
+## Validation Failed
-- [Configuration reference](config.md)
-- [Operations guide](operations.md)
-
-## Validation Status Failed (`run` Exit 2 Or HTTP 200 With Failed Status)
 
 Symptom:
 
-- CLI exits with code `2`.
+- CLI `run` exits `2`.
-- HTTP returns `200`, but `validation.status` is `failed`.
+- HTTP returns `200 OK` with `validation.status` set to `failed`.
 
 Likely cause:
 
@@ -265,18 +252,15 @@ Likely cause:
 
 Diagnostic step:
 
-- Inspect validation mode and validation errors in CLI summary/HTTP response.
+- Inspect validation errors in CLI stderr or the HTTP response.
 
 Safe fix:
 
-- Refine prompt constraints.
+- Refine prompt instructions.
-- Tighten schema or adjust model/profile settings.
+- Adjust schema or model/profile settings.
 - Rerun after correction.
 
-Relevant links:
+Relevant links: [Operations guide](operations.md), [HTTP API reference](api.md)
-
-- [Configuration reference](config.md)
-- [Operations guide](operations.md)
 
 ## Validation Runtime Failure
 
@@ -287,48 +271,91 @@ Symptom:
 
 Likely cause:
 
-- `json_schema` schema file missing/inaccessible.
+- `json_schema` schema file is missing or unreadable.
-- Invalid schema JSON document.
+- Schema JSON is invalid.
 
 Diagnostic step:
 
-- Verify `schema_dir` and `output.schema_path` resolution.
+- Verify `schema_dir` and prompt `output.schema_path`.
-- Check schema file readability and valid JSON syntax.
+- Check schema file readability and JSON syntax.
 
 Safe fix:
 
-- Correct schema path.
+- Correct schema path or permissions.
-- Fix schema JSON content.
+- Fix schema JSON.
 - Rerun.
 
-Relevant links:
+Relevant links: [Configuration reference](config.md), [Operations guide](operations.md)
 
-- [Configuration reference](config.md)
+## HTTP JSON Or Request Contract Errors
-- [Operations guide](operations.md)
-
-## HTTP Request Parsing/Contract Errors
 
 Symptom:
 
-- HTTP `400 invalid_json` or `400 invalid_request`.
+- HTTP returns `400 invalid_json` or `400 invalid_request`.
 
 Likely cause:
 
-- Malformed JSON body.
+- JSON body is malformed.
-- Unknown JSON fields.
+- Request has unknown fields or trailing JSON tokens.
-- Missing required `prompt_id` or `inputs`.
+- Required `prompt_id` or `inputs` is missing.
+- Runtime override values are out of range.
+- `extra_params` collides with reserved outbound fields.
 
 Diagnostic step:
 
-- Revalidate request JSON.
+- Revalidate request JSON and compare fields with the API reference.
-- Confirm required request fields are present.
 
 Safe fix:
 
-- Send valid JSON with only supported fields.
+- Send one JSON object with only supported fields.
-- Ensure `prompt_id` and at least one input mapping are included.
+- Include `prompt_id` and at least one input.
+- Use valid model override ranges.
+- Remove reserved `extra_params` keys.
 
-Relevant links:
+Relevant links: [HTTP API reference](api.md)
 
-- [Operations guide](operations.md)
+## HTTP Size Limit Errors
-- [CLI reference](cli.md)
+
+Symptom:
+
+- HTTP returns `413 request_too_large`, `413 artifact_too_large`, or `413 response_too_large`.
+
+Likely cause:
+
+- JSON request body exceeds `server.max_request_bytes`.
+- HTTP file input exceeds `server.max_artifact_bytes`.
+- Encoded JSON response exceeds `server.max_response_bytes`.
+
+Diagnostic step:
+
+- Compare request, file input, and expected response sizes with configured limits.
+
+Safe fix:
+
+- Use smaller inline inputs or switch to file inputs under the artifact root.
+- Reduce generated output size.
+- Omit `include_raw_output`.
+- Increase limits only when the deployment expects larger payloads.
+
+Relevant links: [HTTP API reference](api.md), [Operations guide](operations.md)
+
+## HTTP Route Or Method Errors
+
+Symptom:
+
+- HTTP returns `404 not_found` or `405 method_not_allowed`.
+
+Likely cause:
+
+- Path is not `/v1/runs`.
+- Method on `/v1/runs` is not `POST`.
+
+Diagnostic step:
+
+- Check the request URL and method.
+
+Safe fix:
+
+- Send `POST /v1/runs`.
+
+Relevant links: [HTTP API reference](api.md)

engine.go

@@ -0,0 +1,318 @@
+package scriptorium
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	artifactadapter "gitea.maximumdirect.net/eric/scriptorium/internal/artifact"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile/builtin"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/prompt"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/usecase"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/validate"
+)
+
+// ErrInvalidConfig indicates invalid public engine configuration.
+var ErrInvalidConfig = errors.New("invalid engine configuration")
+
+var (
+	ErrInvalidRequest  = errors.New("invalid run request")
+	ErrPromptNotFound  = errors.New("prompt not found")
+	ErrProfileNotFound = errors.New("profile not found")
+	ErrPromptLoad      = errors.New("failed to load prompt definition")
+	ErrProfileLoad     = errors.New("failed to load execution profile")
+	ErrArtifactLoad    = errors.New("failed to load artifact")
+	ErrPromptRender    = errors.New("failed to render prompt")
+	ErrLLMGenerate     = errors.New("failed to generate output")
+	ErrValidation      = errors.New("failed to validate output")
+)
+
+// Engine prepares and runs Scriptorium prompt requests.
+type Engine struct {
+	runner *usecase.Runner
+}
+
+// Config configures a public Scriptorium engine.
+type Config struct {
+	PromptDir  string
+	ProfileDir string
+	SchemaDir  string
+	Timeout    time.Duration
+	HTTPClient *http.Client
+}
+
+// Option customizes engine construction.
+type Option interface {
+	apply(*engineOptions) error
+}
+
+type optionFunc func(*engineOptions) error
+
+func (f optionFunc) apply(options *engineOptions) error {
+	return f(options)
+}
+
+type engineOptions struct {
+	llmClient       llm.Client
+	promptDefs      promptdef.Repository
+	profiles        profile.Repository
+	memoryProfiles  profile.Repository
+	validator       validate.Validator
+	promptSource    bool
+	profileSource   bool
+	memorySource    bool
+	validatorSource bool
+}
+
+// WithLLMClient injects a custom LLM client for execution.
+func WithLLMClient(client LLMClient) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if client == nil {
+			return ErrInvalidConfig
+		}
+		options.llmClient = publicLLMClientAdapter{client: client}
+		return nil
+	})
+}
+
+// WithPromptFS loads prompt definitions from fsys under root.
+//
+// The source uses the same strict prompt YAML rules as configured prompt
+// directories, and prompt content_file paths resolve within this source.
+func WithPromptFS(fsys fs.FS, root string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if fsys == nil {
+			return ErrInvalidConfig
+		}
+		if strings.TrimSpace(root) == "" {
+			return ErrInvalidConfig
+		}
+		options.promptDefs = promptdef.NewFSRepository(fsys, root)
+		options.promptSource = true
+		return nil
+	})
+}
+
+// WithPromptFile loads prompt definitions from the single prompt file at path.
+//
+// Relative prompt content_file paths resolve from the file's directory.
+func WithPromptFile(path string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		fsys, root, err := fileSource(path)
+		if err != nil {
+			return err
+		}
+		options.promptDefs = promptdef.NewFSRepository(fsys, root)
+		options.promptSource = true
+		return nil
+	})
+}
+
+// WithProfileFS loads execution profiles from fsys under root.
+//
+// Profiles from this source overlay built-in profiles. Profile YAML must use
+// api_key_env for environment-based credentials; raw API keys are rejected.
+func WithProfileFS(fsys fs.FS, root string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if fsys == nil {
+			return ErrInvalidConfig
+		}
+		if strings.TrimSpace(root) == "" {
+			return ErrInvalidConfig
+		}
+		options.profiles = profile.NewFSRepository(fsys, root)
+		options.profileSource = true
+		return nil
+	})
+}
+
+// WithProfileFile loads execution profiles from the single profile file at path.
+//
+// The profile overlays built-in profiles. Profile YAML must use api_key_env for
+// environment-based credentials; raw API keys are rejected.
+func WithProfileFile(path string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		fsys, root, err := fileSource(path)
+		if err != nil {
+			return err
+		}
+		options.profiles = profile.NewFSRepository(fsys, root)
+		options.profileSource = true
+		return nil
+	})
+}
+
+// WithProfiles configures in-memory profiles that take precedence over
+// configured profile files and built-in profiles.
+func WithProfiles(profiles ...Profile) Option {
+	return optionFunc(func(options *engineOptions) error {
+		repo, err := newMemoryProfileRepository(profiles)
+		if err != nil {
+			return err
+		}
+		options.memoryProfiles = repo
+		options.memorySource = true
+		return nil
+	})
+}
+
+// WithSchemaFS loads JSON Schema documents from fsys under root.
+//
+// Prompt schema_path values resolve within this source when schema validation
+// or structured output is requested.
+func WithSchemaFS(fsys fs.FS, root string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if fsys == nil {
+			return ErrInvalidConfig
+		}
+		if strings.TrimSpace(root) == "" {
+			return ErrInvalidConfig
+		}
+		options.validator = validate.NewFSValidator(fsys, root)
+		options.validatorSource = true
+		return nil
+	})
+}
+
+// WithSchemaFile loads JSON Schema documents from the single schema file at path.
+//
+// Prompt schema_path values refer to the file's base name.
+func WithSchemaFile(path string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		fsys, root, err := fileSource(path)
+		if err != nil {
+			return err
+		}
+		options.validator = validate.NewFSValidator(fsys, root)
+		options.validatorSource = true
+		return nil
+	})
+}
+
+// NewEngine constructs an Engine using the same default internal components as
+// the CLI and HTTP adapters.
+func NewEngine(cfg Config, opts ...Option) (*Engine, error) {
+	var options engineOptions
+	for _, opt := range opts {
+		if opt == nil {
+			continue
+		}
+		if err := opt.apply(&options); err != nil {
+			return nil, fmt.Errorf("%w: %v", ErrInvalidConfig, err)
+		}
+	}
+
+	promptDefs := options.promptDefs
+	if !options.promptSource {
+		if strings.TrimSpace(cfg.PromptDir) == "" {
+			return nil, fmt.Errorf("%w: prompt directory is required", ErrInvalidConfig)
+		}
+		promptDefs = promptdef.NewFilesystemRepository(cfg.PromptDir)
+	}
+
+	profiles := builtin.NewRepositoryWithDirectory(cfg.ProfileDir)
+	if options.profileSource {
+		profiles = builtin.NewRepositoryWithPrimary(options.profiles)
+	}
+	if options.memorySource {
+		profiles = profile.NewOverlayRepository(options.memoryProfiles, profiles)
+	}
+
+	validator := options.validator
+	if !options.validatorSource {
+		schemaDir := cfg.SchemaDir
+		if strings.TrimSpace(schemaDir) == "" {
+			schemaDir = defaults.SchemaDirDefault
+		}
+		validator = validate.NewStandardValidator(schemaDir)
+	}
+
+	llmClient := options.llmClient
+	if llmClient == nil {
+		var err error
+		llmClient, err = llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{
+			Timeout:    cfg.Timeout,
+			HTTPClient: cfg.HTTPClient,
+		})
+		if err != nil {
+			return nil, fmt.Errorf("%w: %v", ErrInvalidConfig, err)
+		}
+	}
+
+	return &Engine{
+		runner: usecase.NewRunner(
+			promptDefs,
+			profiles,
+			artifactadapter.NewCompositeReader(),
+			prompt.NewGoRenderer(),
+			llmClient,
+			validator,
+		),
+	}, nil
+}
+
+func fileSource(name string) (fs.FS, string, error) {
+	cleanName := strings.TrimSpace(name)
+	if cleanName == "" {
+		return nil, "", ErrInvalidConfig
+	}
+	dir := filepath.Dir(cleanName)
+	base := filepath.Base(cleanName)
+	if base == "." || base == string(filepath.Separator) || strings.TrimSpace(base) == "" {
+		return nil, "", ErrInvalidConfig
+	}
+	info, err := os.Stat(cleanName)
+	if err != nil {
+		return nil, "", fmt.Errorf("%w: failed to access source file %q: %v", ErrInvalidConfig, cleanName, err)
+	}
+	if info.IsDir() {
+		return nil, "", fmt.Errorf("%w: source path %q must be a file", ErrInvalidConfig, cleanName)
+	}
+	return os.DirFS(dir), filepath.ToSlash(base), nil
+}
+
+// Prepare resolves a prompt request without calling an LLM.
+func (e *Engine) Prepare(ctx context.Context, req RunRequest) (*PreparedRun, error) {
+	if e == nil || e.runner == nil {
+		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
+	}
+
+	domainReq, err := toDomainRunRequest(req)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
+	}
+
+	prepared, err := e.runner.Prepare(ctx, domainReq)
+	if err != nil {
+		return nil, mapPublicError(err)
+	}
+	return fromDomainPreparedRun(prepared), nil
+}
+
+// Run executes a prompt request and returns the generated artifact and metadata.
+func (e *Engine) Run(ctx context.Context, req RunRequest) (*RunResult, error) {
+	if e == nil || e.runner == nil {
+		return nil, fmt.Errorf("%w: engine is nil", ErrInvalidConfig)
+	}
+
+	domainReq, err := toDomainRunRequest(req)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
+	}
+
+	result, err := e.runner.Run(ctx, domainReq)
+	if err != nil {
+		return nil, mapPublicError(err)
+	}
+	return fromDomainRunResult(result), nil
+}

errors.go

@@ -0,0 +1,79 @@
+package scriptorium
+
+import (
+	"errors"
+	"fmt"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/usecase"
+)
+
+func mapPublicError(err error) error {
+	if err == nil {
+		return nil
+	}
+	if hasPublicError(err) {
+		return err
+	}
+	publicErr := publicErrorFor(err)
+	if publicErr == nil {
+		return err
+	}
+	return fmt.Errorf("%w: %w", publicErr, err)
+}
+
+func hasPublicError(err error) bool {
+	for _, publicErr := range []error{
+		ErrInvalidConfig,
+		ErrInvalidRequest,
+		ErrPromptNotFound,
+		ErrProfileNotFound,
+		ErrPromptLoad,
+		ErrProfileLoad,
+		ErrArtifactLoad,
+		ErrPromptRender,
+		ErrLLMGenerate,
+		ErrValidation,
+	} {
+		if errors.Is(err, publicErr) {
+			return true
+		}
+	}
+	return false
+}
+
+func publicErrorFor(err error) error {
+	switch {
+	case errors.Is(err, promptdef.ErrPromptDefinitionNotFound):
+		return ErrPromptNotFound
+	case errors.Is(err, profile.ErrProfileNotFound):
+		return ErrProfileNotFound
+	case errors.Is(err, usecase.ErrPromptLoad):
+		return ErrPromptLoad
+	case errors.Is(err, usecase.ErrProfileLoad):
+		return ErrProfileLoad
+	case errors.Is(err, promptdef.ErrInvalidYAML), errors.Is(err, promptdef.ErrInvalidPromptDefinition):
+		return ErrPromptLoad
+	case isProfileLoadCause(err):
+		return ErrProfileLoad
+	case errors.Is(err, usecase.ErrArtifactLoad):
+		return ErrArtifactLoad
+	case errors.Is(err, usecase.ErrPromptRender):
+		return ErrPromptRender
+	case errors.Is(err, usecase.ErrLLMGenerate):
+		return ErrLLMGenerate
+	case errors.Is(err, usecase.ErrValidation):
+		return ErrValidation
+	case errors.Is(err, usecase.ErrInvalidRequest):
+		return ErrInvalidRequest
+	default:
+		return nil
+	}
+}
+
+func isProfileLoadCause(err error) bool {
+	return errors.Is(err, profile.ErrInvalidYAML) ||
+		errors.Is(err, profile.ErrInvalidProfile) ||
+		errors.Is(err, profile.ErrRawAPIKeyNotAllowed)
+}

examples/config.full.yml

@@ -0,0 +1,13 @@
+prompt_dir: ./examples/prompts
+profile_dir: ./examples/profiles
+schema_dir: ./examples/schemas
+
+server:
+  addr: 127.0.0.1:8080
+  artifact_root: .
+  max_request_bytes: 16777216
+  max_artifact_bytes: 16777216
+  max_response_bytes: 16777216
+
+defaults:
+  render_format: text

examples/config.yml

@@ -4,6 +4,7 @@ schema_dir: ./examples/schemas
 
 server:
   addr: :8080
+  artifact_root: .
 
 defaults:
   render_format: text

examples/go-library/prepare/main.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"log"
+	"os"
+
+	"gitea.maximumdirect.net/eric/scriptorium"
+)
+
+func main() {
+	engine, err := scriptorium.NewEngine(scriptorium.Config{
+		PromptDir:  "./examples/prompts",
+		ProfileDir: "./examples/profiles",
+		SchemaDir:  "./examples/schemas",
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	prepared, err := engine.Prepare(context.Background(), scriptorium.RunRequest{
+		PromptID: "generic.markdown_summary",
+		Inputs: map[string]scriptorium.ArtifactRef{
+			"transcript": scriptorium.File("./examples/fixtures/transcript.md"),
+			"glossary":   scriptorium.File("./examples/fixtures/glossary.yml"),
+		},
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	summary := struct {
+		PromptID          string            `json:"prompt_id"`
+		SelectedProfileID string            `json:"selected_profile_id"`
+		Model             string            `json:"model"`
+		MessageCount      int               `json:"message_count"`
+		InputHashes       map[string]string `json:"input_hashes"`
+	}{
+		PromptID:          prepared.PromptID,
+		SelectedProfileID: prepared.SelectedProfileID,
+		Model:             prepared.EffectiveModelParams.Model,
+		MessageCount:      len(prepared.Messages),
+		InputHashes:       prepared.InputHashes,
+	}
+
+	if err := json.NewEncoder(os.Stdout).Encode(summary); err != nil {
+		log.Fatal(err)
+	}
+}

formatting.go

@@ -0,0 +1,51 @@
+package scriptorium
+
+import "fmt"
+
+// String returns a concise request summary without exposing direct API keys.
+func (r RunRequest) String() string {
+	return r.redactedString()
+}
+
+// GoString returns a concise request summary without exposing direct API keys.
+func (r RunRequest) GoString() string {
+	return r.redactedString()
+}
+
+func (r RunRequest) redactedString() string {
+	return fmt.Sprintf(
+		"scriptorium.RunRequest{PromptID:%q PromptVersion:%q ProfileID:%q APIKeySet:%t Inputs:%d Vars:%d ExecutionSet:%t ValidationSet:%t Metadata:%d}",
+		r.PromptID,
+		r.PromptVersion,
+		r.ProfileID,
+		r.APIKey != "",
+		len(r.Inputs),
+		len(r.Vars),
+		r.Execution != nil,
+		r.Validation != nil,
+		len(r.Metadata),
+	)
+}
+
+// String returns a concise request summary without exposing direct API keys or
+// rendered prompt content.
+func (r GenerateRequest) String() string {
+	return r.redactedString()
+}
+
+// GoString returns a concise request summary without exposing direct API keys or
+// rendered prompt content.
+func (r GenerateRequest) GoString() string {
+	return r.redactedString()
+}
+
+func (r GenerateRequest) redactedString() string {
+	return fmt.Sprintf(
+		"scriptorium.GenerateRequest{Messages:%d Model:%q APIKeySet:%t StructuredOutputSet:%t ExtraParams:%d}",
+		len(r.Prompt.Messages),
+		r.Target.Model,
+		r.APIKey != "",
+		r.StructuredOutput != nil,
+		len(r.Target.ExtraParams),
+	)
+}

internal/adapter/cli/run.go

@@ -19,7 +19,7 @@ import (
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 	renderformat "gitea.maximumdirect.net/eric/scriptorium/internal/format"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
-	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile/builtin"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/prompt"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/usecase"
@@ -34,7 +34,6 @@ const (
 
 const (
 	errPromptDirRequired = "prompt directory is required; provide --prompt-dir or config.yml prompt_dir"
-	errProfileDirRequired = "profile directory is required; provide --profile-dir or config.yml profile_dir"
 )
 
 type runConfig struct {
@@ -79,6 +78,10 @@ type serveConfig struct {
 	promptDir        string
 	profileDir       string
 	schemaDir        string
+	artifactRoot     string
+	maxRequestBytes  int64
+	maxArtifactBytes int64
+	maxResponseBytes int64
 }
 
 type commonCommandSettings struct {
@@ -86,6 +89,10 @@ type commonCommandSettings struct {
 	profileDir          string
 	schemaDir           string
 	serverAddr          string
+	artifactRoot        string
+	maxRequestBytes     int64
+	maxArtifactBytes    int64
+	maxResponseBytes    int64
 	defaultRenderFormat renderformat.PreparedRunOutputFormat
 }
 
@@ -203,9 +210,18 @@ func serveCommand(args []string, stderr io.Writer) int {
 		return ExitRuntimeError
 	}
 
-	runner := newRunner(cfg.promptDir, cfg.profileDir, cfg.schemaDir, llmClient)
+	artifactReader, err := artifactadapter.NewRestrictedCompositeReaderWithLimit(cfg.artifactRoot, cfg.maxArtifactBytes)
+	if err != nil {
+		fmt.Fprintf(stderr, "artifact root error: %v\n", err)
+		return ExitRuntimeError
+	}
 
-	h := httpadapter.NewHandler(runner)
+	runner := newRunnerWithArtifactReader(cfg.promptDir, cfg.profileDir, cfg.schemaDir, llmClient, artifactReader)
+
+	h := httpadapter.NewHandlerWithOptions(runner, httpadapter.HandlerOptions{
+		MaxRequestBytes:  cfg.maxRequestBytes,
+		MaxResponseBytes: cfg.maxResponseBytes,
+	})
 	srv := &http.Server{
 		Addr:              cfg.addr,
 		Handler:           h,
@@ -282,6 +298,10 @@ func parseServeArgs(args []string) (*serveConfig, error) {
 	fs.StringVar(&cfg.promptDir, "prompt-dir", "", "directory containing prompt definition YAML files")
 	fs.StringVar(&cfg.profileDir, "profile-dir", "", "directory containing execution profile YAML files")
 	fs.StringVar(&cfg.schemaDir, "schema-dir", "", "base directory for validation schemas")
+	fs.StringVar(&cfg.artifactRoot, "artifact-root", "", "base directory for HTTP file input artifacts")
+	fs.Int64Var(&cfg.maxRequestBytes, "max-request-bytes", 0, "maximum HTTP request body bytes; 0 disables the limit")
+	fs.Int64Var(&cfg.maxArtifactBytes, "max-artifact-bytes", 0, "maximum HTTP file artifact bytes; 0 disables the limit")
+	fs.Int64Var(&cfg.maxResponseBytes, "max-response-bytes", 0, "maximum HTTP response body bytes; 0 disables the limit")
 
 	if err := fs.Parse(args); err != nil {
 		return nil, err
@@ -295,6 +315,10 @@ func parseServeArgs(args []string) (*serveConfig, error) {
 		ProfileDir:       cfg.profileDirIfSet(fs),
 		SchemaDir:        cfg.schemaDirIfSet(fs),
 		ServerAddr:       cfg.addrIfSet(fs),
+		ArtifactRoot:     cfg.artifactRootIfSet(fs),
+		MaxRequestBytes:  cfg.maxRequestBytesIfSet(fs),
+		MaxArtifactBytes: cfg.maxArtifactBytesIfSet(fs),
+		MaxResponseBytes: cfg.maxResponseBytesIfSet(fs),
 	})
 	if err != nil {
 		return nil, err
@@ -304,14 +328,23 @@ func parseServeArgs(args []string) (*serveConfig, error) {
 	cfg.profileDir = settings.profileDir
 	cfg.schemaDir = settings.schemaDir
 	cfg.addr = settings.serverAddr
+	cfg.artifactRoot = settings.artifactRoot
+	cfg.maxRequestBytes = settings.maxRequestBytes
+	cfg.maxArtifactBytes = settings.maxArtifactBytes
+	cfg.maxResponseBytes = settings.maxResponseBytes
 
-	if err := validateRequiredLibraryDirs(cfg.promptDir, cfg.profileDir); err != nil {
+	if err := validateRequiredLibraryDirs(cfg.promptDir); err != nil {
 		return nil, err
 	}
 
 	cfg.promptDir = filepath.Clean(cfg.promptDir)
+	if strings.TrimSpace(cfg.profileDir) != "" {
 		cfg.profileDir = filepath.Clean(cfg.profileDir)
+	}
 	cfg.schemaDir = filepath.Clean(cfg.schemaDir)
+	if strings.TrimSpace(cfg.artifactRoot) != "" {
+		cfg.artifactRoot = filepath.Clean(cfg.artifactRoot)
+	}
 	return cfg, nil
 }
 
@@ -353,7 +386,7 @@ func finalizeExecutionRequestConfig(fs *flag.FlagSet, cfg *runConfig) error {
 	cfg.schemaDir = settings.schemaDir
 	cfg.defaultRenderFormat = settings.defaultRenderFormat
 
-	if err := validateRequiredLibraryDirs(cfg.promptDir, cfg.profileDir); err != nil {
+	if err := validateRequiredLibraryDirs(cfg.promptDir); err != nil {
 		return err
 	}
 	if strings.TrimSpace(cfg.promptID) == "" {
@@ -363,7 +396,9 @@ func finalizeExecutionRequestConfig(fs *flag.FlagSet, cfg *runConfig) error {
 		return errors.New("at least one --input is required")
 	}
 	cfg.promptDir = filepath.Clean(cfg.promptDir)
+	if strings.TrimSpace(cfg.profileDir) != "" {
 		cfg.profileDir = filepath.Clean(cfg.profileDir)
+	}
 	if cfg.outputPath != "" {
 		cfg.outputPath = filepath.Clean(cfg.outputPath)
 	}
@@ -426,6 +461,34 @@ func (c *serveConfig) addrIfSet(fs *flag.FlagSet) string {
 	return ""
 }
 
+func (c *serveConfig) artifactRootIfSet(fs *flag.FlagSet) string {
+	if flagWasSet(fs, "artifact-root") {
+		return c.artifactRoot
+	}
+	return ""
+}
+
+func (c *serveConfig) maxRequestBytesIfSet(fs *flag.FlagSet) *int64 {
+	if flagWasSet(fs, "max-request-bytes") {
+		return &c.maxRequestBytes
+	}
+	return nil
+}
+
+func (c *serveConfig) maxArtifactBytesIfSet(fs *flag.FlagSet) *int64 {
+	if flagWasSet(fs, "max-artifact-bytes") {
+		return &c.maxArtifactBytes
+	}
+	return nil
+}
+
+func (c *serveConfig) maxResponseBytesIfSet(fs *flag.FlagSet) *int64 {
+	if flagWasSet(fs, "max-response-bytes") {
+		return &c.maxResponseBytes
+	}
+	return nil
+}
+
 func registerConfigPathFlag(fs *flag.FlagSet, target *string) {
 	fs.StringVar(
 		target,
@@ -463,25 +526,33 @@ func resolveCommonSettings(fs *flag.FlagSet, configPath string, overrides appcon
 		profileDir:          settings.ProfileDir,
 		schemaDir:           settings.SchemaDir,
 		serverAddr:          settings.ServerAddr,
+		artifactRoot:        settings.ArtifactRoot,
+		maxRequestBytes:     settings.MaxRequestBytes,
+		maxArtifactBytes:    settings.MaxArtifactBytes,
+		maxResponseBytes:    settings.MaxResponseBytes,
 		defaultRenderFormat: settings.DefaultRenderFormat,
 	}, nil
 }
 
-func validateRequiredLibraryDirs(promptDir, profileDir string) error {
+func validateRequiredLibraryDirs(promptDir string) error {
 	if strings.TrimSpace(promptDir) == "" {
 		return errors.New(errPromptDirRequired)
 	}
-	if strings.TrimSpace(profileDir) == "" {
-		return errors.New(errProfileDirRequired)
-	}
 	return nil
 }
 
 func newRunner(promptDir, profileDir, schemaDir string, llmClient llm.Client) *usecase.Runner {
+	return newRunnerWithArtifactReader(promptDir, profileDir, schemaDir, llmClient, artifactadapter.NewCompositeReader())
+}
+
+func newRunnerWithArtifactReader(promptDir, profileDir, schemaDir string, llmClient llm.Client, artifactReader artifactadapter.Reader) *usecase.Runner {
+	if artifactReader == nil {
+		artifactReader = artifactadapter.NewCompositeReader()
+	}
 	return usecase.NewRunner(
 		promptdef.NewFilesystemRepository(promptDir),
-		profile.NewFilesystemRepository(profileDir),
+		builtin.NewRepositoryWithDirectory(profileDir),
-		artifactadapter.NewCompositeReader(),
+		artifactReader,
 		prompt.NewGoRenderer(),
 		llmClient,
 		validate.NewStandardValidator(schemaDir),
@@ -513,18 +584,25 @@ func buildRunRequestFromConfig(cfg *runConfig) (domain.RunRequest, error) {
 		inputs[name] = domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: path}
 	}
 
-	var modelOverride *domain.ExecutionTarget
+	var modelOverride *domain.ExecutionTargetOverride
 	if cfg.llmBaseURLSet || cfg.modelSet || cfg.temperatureSet || cfg.maxTokensSet || cfg.topPSet || cfg.apiKeyEnvSet || cfg.timeoutSet {
-		modelOverride = &domain.ExecutionTarget{
+		modelOverride = &domain.ExecutionTargetOverride{
 			Endpoint:  cfg.llmBaseURL,
 			Model:     cfg.model,
-			Temperature: cfg.temperature,
-			MaxTokens:   cfg.maxTokens,
-			TopP:        cfg.topP,
 			APIKeyEnv: cfg.apiKeyEnv,
 		}
+		if cfg.temperatureSet {
+			modelOverride.Temperature = &cfg.temperature
+		}
+		if cfg.maxTokensSet {
+			modelOverride.MaxTokens = &cfg.maxTokens
+		}
+		if cfg.topPSet {
+			modelOverride.TopP = &cfg.topP
+		}
 		if cfg.timeoutSet {
-			modelOverride.TimeoutSeconds = int(cfg.timeout.Seconds())
+			timeoutSeconds := int(cfg.timeout.Seconds())
+			modelOverride.TimeoutSeconds = &timeoutSeconds
 		}
 	}
 
@@ -606,7 +684,7 @@ func printSummary(stderr io.Writer, res *domain.RunResult) {
 	if res == nil {
 		return
 	}
-	fmt.Fprintf(stderr, "prompt=%s@%s selected_profile=%s model=%s validation=%s mode=%s validation_errors=%d prompt_hash=%s inputs=%d usage=%d/%d/%d\n",
+	fmt.Fprintf(stderr, "prompt=%s@%s selected_profile=%s model=%s validation=%s mode=%s validation_errors=%d prompt_hash=%s inputs=%d usage=%d/%d/%d",
 		res.PromptID,
 		res.PromptVersion,
 		res.SelectedProfileID,
@@ -620,11 +698,15 @@ func printSummary(stderr io.Writer, res *domain.RunResult) {
 		res.Usage.CompletionTokens,
 		res.Usage.TotalTokens,
 	)
+	if res.Usage.CachedTokens != 0 || res.Usage.CacheWriteTokens != 0 {
+		fmt.Fprintf(stderr, " cached_tokens=%d cache_write_tokens=%d", res.Usage.CachedTokens, res.Usage.CacheWriteTokens)
+	}
+	fmt.Fprintln(stderr)
 }
 
 func printUsage(w io.Writer) {
 	fmt.Fprintln(w, "usage: scriptorium <run|render|serve> ...")
 	fmt.Fprintln(w, "  run:   scriptorium run [--config PATH] [--prompt-dir DIR] [--profile-dir DIR] --prompt ID --input name=path [--input ...] [--profile ID] [--llm-base-url URL] [--model NAME] [--api-key-env ENV] [--temperature N] [--max-tokens N] [--top-p N] [--var k=v] [--out path] [--timeout 10m]")
 	fmt.Fprintln(w, "  render: scriptorium render [--config PATH] [--prompt-dir DIR] [--profile-dir DIR] --prompt ID --input name=path [--input ...] [--profile ID] [--llm-base-url URL] [--model NAME] [--api-key-env ENV] [--temperature N] [--max-tokens N] [--top-p N] [--var k=v] [--format text|json] [--out path] [--timeout 10m]")
-	fmt.Fprintf(w, "  serve: scriptorium serve [--config PATH] [--addr %s] [--prompt-dir DIR] [--profile-dir DIR] [--schema-dir DIR]\n", defaults.HTTPAddrDefault)
+	fmt.Fprintf(w, "  serve: scriptorium serve [--config PATH] [--addr %s] [--prompt-dir DIR] [--profile-dir DIR] [--schema-dir DIR] [--artifact-root DIR] [--max-request-bytes N] [--max-artifact-bytes N] [--max-response-bytes N]\n", defaults.HTTPAddrDefault)
 }

internal/adapter/cli/run_test.go

@@ -74,12 +74,12 @@ func TestParseRunArgsRequiredFlags(t *testing.T) {
 		t.Fatalf("expected clear prompt-dir guidance, got %v", err)
 	}
 
-	_, err = parseRunArgs([]string{"--config", configPath, "--prompt-dir", "./prompts", "--prompt", "p", "--input", "a=b"})
+	cfg, err := parseRunArgs([]string{"--config", configPath, "--prompt-dir", "./prompts", "--prompt", "p", "--input", "a=b"})
-	if err == nil {
+	if err != nil {
-		t.Fatal("expected missing --profile-dir error")
+		t.Fatalf("expected missing --profile-dir to be accepted, got %v", err)
 	}
-	if !strings.Contains(err.Error(), "profile directory is required") {
+	if cfg.profileDir != "" {
-		t.Fatalf("expected clear profile-dir guidance, got %v", err)
+		t.Fatalf("expected empty profile dir for built-ins, got %q", cfg.profileDir)
 	}
 
 	_, err = parseRunArgs([]string{"--config", configPath, "--prompt-dir", "./prompts", "--profile-dir", "./profiles", "--input", "a=b"})
@@ -161,17 +161,12 @@ func TestParseServeArgsRequiredFlags(t *testing.T) {
 		t.Fatalf("expected clear prompt-dir guidance, got %v", err)
 	}
 
-	_, err = parseServeArgs([]string{"--config", configPath, "--prompt-dir", "./prompts"})
+	cfg, err := parseServeArgs([]string{"--config", configPath, "--prompt-dir", "./prompts"})
-	if err == nil {
-		t.Fatal("expected missing --profile-dir error")
-	}
-	if !strings.Contains(err.Error(), "profile directory is required") {
-		t.Fatalf("expected clear profile-dir guidance, got %v", err)
-	}
-
-	cfg, err := parseServeArgs([]string{"--config", configPath, "--prompt-dir", "./prompts", "--profile-dir", "./profiles"})
 	if err != nil {
-		t.Fatalf("expected valid serve args, got %v", err)
+		t.Fatalf("expected missing --profile-dir to be accepted, got %v", err)
+	}
+	if cfg.profileDir != "" {
+		t.Fatalf("expected empty profile dir for built-ins, got %q", cfg.profileDir)
 	}
 	if cfg.addr != defaults.HTTPAddrDefault {
 		t.Fatalf("expected default addr %s, got %q", defaults.HTTPAddrDefault, cfg.addr)
@@ -197,6 +192,26 @@ func TestParseServeArgsRejectsRuntimeOverrideFlags(t *testing.T) {
 	}
 }
 
+func TestUsageIncludesServeFileAndSizeLimitFlags(t *testing.T) {
+	var stderr bytes.Buffer
+	code := Run(nil, io.Discard, &stderr)
+	if code != ExitRuntimeError {
+		t.Fatalf("expected usage path to return runtime error, got %d", code)
+	}
+
+	usage := stderr.String()
+	for _, want := range []string{
+		"--artifact-root",
+		"--max-request-bytes",
+		"--max-artifact-bytes",
+		"--max-response-bytes",
+	} {
+		if !strings.Contains(usage, want) {
+			t.Fatalf("expected usage to include %q, got %q", want, usage)
+		}
+	}
+}
+
 func TestParseRunArgsTimeout(t *testing.T) {
 	cfg, err := parseRunArgs([]string{
 		"--prompt-dir", "./prompts",
@@ -440,11 +455,19 @@ profile_dir: ./from-config/profiles
 schema_dir: ./from-config/schemas
 server:
   addr: 127.0.0.1:9000
+  artifact_root: ./from-config/artifacts
+  max_request_bytes: 1024
+  max_artifact_bytes: 2048
+  max_response_bytes: 4096
 `)
 
 	cfg, err := parseServeArgs([]string{
 		"--config", configPath,
 		"--addr", ":7777",
+		"--artifact-root", "./from-cli/artifacts",
+		"--max-request-bytes", "0",
+		"--max-artifact-bytes", "8192",
+		"--max-response-bytes", "16384",
 	})
 	if err != nil {
 		t.Fatalf("expected valid args, got %v", err)
@@ -462,6 +485,18 @@ server:
 	if cfg.addr != ":7777" {
 		t.Fatalf("expected CLI addr override, got %q", cfg.addr)
 	}
+	if cfg.artifactRoot != filepath.Clean("./from-cli/artifacts") {
+		t.Fatalf("expected CLI artifact root override, got %q", cfg.artifactRoot)
+	}
+	if cfg.maxRequestBytes != 0 {
+		t.Fatalf("expected CLI max request bytes override, got %d", cfg.maxRequestBytes)
+	}
+	if cfg.maxArtifactBytes != 8192 {
+		t.Fatalf("expected CLI max artifact bytes override, got %d", cfg.maxArtifactBytes)
+	}
+	if cfg.maxResponseBytes != 16384 {
+		t.Fatalf("expected CLI max response bytes override, got %d", cfg.maxResponseBytes)
+	}
 }
 
 func TestParseServeArgsWithConfigProvidesRequiredDirectoriesAndAddr(t *testing.T) {
@@ -471,6 +506,10 @@ profile_dir: ./from-config/profiles
 schema_dir: ./from-config/schemas
 server:
   addr: 127.0.0.1:9000
+  artifact_root: ./from-config/artifacts
+  max_request_bytes: 1024
+  max_artifact_bytes: 2048
+  max_response_bytes: 4096
 `)
 
 	cfg, err := parseServeArgs([]string{
@@ -492,6 +531,75 @@ server:
 	if cfg.addr != "127.0.0.1:9000" {
 		t.Fatalf("expected addr from config, got %q", cfg.addr)
 	}
+	if cfg.artifactRoot != filepath.Clean("./from-config/artifacts") {
+		t.Fatalf("expected artifact root from config, got %q", cfg.artifactRoot)
+	}
+	if cfg.maxRequestBytes != 1024 {
+		t.Fatalf("expected max request bytes from config, got %d", cfg.maxRequestBytes)
+	}
+	if cfg.maxArtifactBytes != 2048 {
+		t.Fatalf("expected max artifact bytes from config, got %d", cfg.maxArtifactBytes)
+	}
+	if cfg.maxResponseBytes != 4096 {
+		t.Fatalf("expected max response bytes from config, got %d", cfg.maxResponseBytes)
+	}
+}
+
+func TestParseServeArgsRejectsNegativeSizeLimits(t *testing.T) {
+	tests := []struct {
+		name string
+		flag string
+	}{
+		{name: "request", flag: "--max-request-bytes"},
+		{name: "artifact", flag: "--max-artifact-bytes"},
+		{name: "response", flag: "--max-response-bytes"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := parseServeArgs([]string{
+				"--prompt-dir", "./prompts",
+				tc.flag, "-1",
+			})
+			if err == nil {
+				t.Fatal("expected negative size limit error")
+			}
+		})
+	}
+}
+
+func TestRunAndRenderRejectServeSizeLimitFlags(t *testing.T) {
+	for _, tc := range []struct {
+		name  string
+		parse func([]string) error
+	}{
+		{
+			name: "run",
+			parse: func(args []string) error {
+				_, err := parseRunArgs(args)
+				return err
+			},
+		},
+		{
+			name: "render",
+			parse: func(args []string) error {
+				_, err := parseRenderArgs(args)
+				return err
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			err := tc.parse([]string{
+				"--prompt-dir", "./prompts",
+				"--prompt", "p",
+				"--input", "a=b",
+				"--max-request-bytes", "1024",
+			})
+			if err == nil {
+				t.Fatal("expected unsupported flag error")
+			}
+		})
+	}
 }
 
 func TestRunAndRenderBuildEquivalentRuntimeOverrideRequestsForSharedFlags(t *testing.T) {
@@ -565,21 +673,21 @@ profile_dir: ./profiles
 	}
 }
 
-func TestParseRunArgsFailsClearlyWhenNoEffectiveProfileDir(t *testing.T) {
+func TestParseRunArgsAcceptsMissingEffectiveProfileDir(t *testing.T) {
 	configPath := writeAppConfigFile(t, `
 prompt_dir: ./prompts
 `)
 
-	_, err := parseRunArgs([]string{
+	cfg, err := parseRunArgs([]string{
 		"--config", configPath,
 		"--prompt", "p",
 		"--input", "a=b",
 	})
-	if err == nil {
+	if err != nil {
-		t.Fatal("expected missing profile_dir error")
+		t.Fatalf("expected missing profile_dir to be accepted, got %v", err)
 	}
-	if !strings.Contains(err.Error(), "profile directory is required") || !strings.Contains(err.Error(), "config.yml profile_dir") {
+	if cfg.profileDir != "" {
-		t.Fatalf("expected clear profile_dir guidance, got %v", err)
+		t.Fatalf("expected empty profile dir for built-ins, got %q", cfg.profileDir)
 	}
 }
 
@@ -601,21 +709,21 @@ profile_dir: ./profiles
 	}
 }
 
-func TestParseRenderArgsFailsClearlyWhenNoEffectiveProfileDir(t *testing.T) {
+func TestParseRenderArgsAcceptsMissingEffectiveProfileDir(t *testing.T) {
 	configPath := writeAppConfigFile(t, `
 prompt_dir: ./prompts
 `)
 
-	_, err := parseRenderArgs([]string{
+	cfg, err := parseRenderArgs([]string{
 		"--config", configPath,
 		"--prompt", "p",
 		"--input", "a=b",
 	})
-	if err == nil {
+	if err != nil {
-		t.Fatal("expected missing profile_dir error")
+		t.Fatalf("expected missing profile_dir to be accepted, got %v", err)
 	}
-	if !strings.Contains(err.Error(), "profile directory is required") || !strings.Contains(err.Error(), "config.yml profile_dir") {
+	if cfg.profileDir != "" {
-		t.Fatalf("expected clear profile_dir guidance, got %v", err)
+		t.Fatalf("expected empty profile dir for built-ins, got %q", cfg.profileDir)
 	}
 }
 
@@ -747,6 +855,35 @@ func TestRenderCommandDefaultFormatTextIncludesPreparedDetailsAndNoSecrets(t *te
 	}
 }
 
+func TestRenderCommandExplicitZeroTemperatureReachesEffectiveSettings(t *testing.T) {
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
+
+	writePromptFile(t, lib.promptDir, "prompt.render", "local-default")
+	profile := `id: local-default
+endpoint: http://127.0.0.1:1/v1
+model: profile-model
+temperature: 0.7
+`
+	if err := os.WriteFile(filepath.Join(lib.profileDir, "local-default.yaml"), []byte(profile), 0o644); err != nil {
+		t.Fatalf("failed to write profile fixture: %v", err)
+	}
+
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--profile-dir", lib.profileDir,
+		"--prompt", "prompt.render",
+		"--input", "transcript=" + inputPath,
+		"--temperature", "0",
+	})
+	if code != ExitOK {
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
+	}
+	if !strings.Contains(stdout, "\n  temperature: 0\n") {
+		t.Fatalf("expected explicit zero temperature in effective settings, got:\n%s", stdout)
+	}
+}
+
 func TestRenderCommandSucceedsWithPromptAndProfileDirsFromConfig(t *testing.T) {
 	lib := newCLITestLibrary(t)
 	inputPath := lib.writeInputFile(t, "transcript.md", "hello transcript")
@@ -900,6 +1037,29 @@ func TestRenderCommandPromptDefaultProfileWorksThroughCLIPath(t *testing.T) {
 	}
 }
 
+func TestRenderCommandUsesBuiltInProfileWithoutProfileDir(t *testing.T) {
+	t.Setenv("OPENROUTER_API_KEY", "test-key")
+	lib := newCLITestLibrary(t)
+	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
+
+	writePromptFile(t, lib.promptDir, "prompt.builtin", "mistral-small-3")
+
+	code, stdout, stderr := runCLICommand(t, renderCommand, []string{
+		"--prompt-dir", lib.promptDir,
+		"--prompt", "prompt.builtin",
+		"--input", "transcript=" + inputPath,
+	})
+	if code != ExitOK {
+		t.Fatalf("expected ExitOK, got %d stderr=%q", code, stderr)
+	}
+	if !strings.Contains(stdout, "selected_profile_id: mistral-small-3") {
+		t.Fatalf("expected built-in selected profile, got %q", stdout)
+	}
+	if !strings.Contains(stdout, "model: mistralai/mistral-small-3.2-24b-instruct") {
+		t.Fatalf("expected built-in model, got %q", stdout)
+	}
+}
+
 func TestRenderCommandExplicitProfileOverridesPromptDefault(t *testing.T) {
 	lib := newCLITestLibrary(t)
 	inputPath := lib.writeInputFile(t, "transcript.md", "hello")
@@ -1064,6 +1224,38 @@ func TestWriteOutputAndSummaryUseSeparateWriters(t *testing.T) {
 	if !strings.Contains(stderr.String(), "prompt=p@1") {
 		t.Fatalf("expected summary on stderr, got %q", stderr.String())
 	}
+	if strings.Contains(stderr.String(), "cached_tokens=") || strings.Contains(stderr.String(), "cache_write_tokens=") {
+		t.Fatalf("expected zero cache usage to be omitted from summary, got %q", stderr.String())
+	}
+}
+
+func TestPrintSummaryIncludesCacheUsageWhenPresent(t *testing.T) {
+	var stderr bytes.Buffer
+
+	printSummary(&stderr, &domain.RunResult{
+		PromptID:           "p",
+		PromptVersion:      "1",
+		SelectedProfileID:  "exec",
+		ModelName:          "m",
+		Validation:         domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic},
+		RenderedPromptHash: "h",
+		InputHashes:        map[string]string{"in": "x"},
+		Usage: domain.TokenUsage{
+			PromptTokens:     10,
+			CompletionTokens: 5,
+			TotalTokens:      15,
+			CachedTokens:     0,
+			CacheWriteTokens: 3,
+		},
+	})
+
+	summary := stderr.String()
+	if !strings.Contains(summary, "usage=10/5/15") {
+		t.Fatalf("expected base usage summary, got %q", summary)
+	}
+	if !strings.Contains(summary, "cached_tokens=0 cache_write_tokens=3") {
+		t.Fatalf("expected cache usage in summary, got %q", summary)
+	}
 }
 
 type cliTestLibrary struct {

internal/adapter/http/dto.go

@@ -23,14 +23,14 @@ type inputRefDTO struct {
 type modelOverrideRequestDTO struct {
 	Endpoint        string         `json:"endpoint,omitempty"`
 	Model           string         `json:"model,omitempty"`
-	Temperature     float64           `json:"temperature,omitempty"`
+	Temperature     *float64       `json:"temperature,omitempty"`
-	MaxTokens       int               `json:"max_tokens,omitempty"`
+	MaxTokens       *int           `json:"max_tokens,omitempty"`
-	TopP            float64           `json:"top_p,omitempty"`
+	TopP            *float64       `json:"top_p,omitempty"`
-	TimeoutSeconds  int               `json:"timeout_seconds,omitempty"`
+	TimeoutSeconds  *int           `json:"timeout_seconds,omitempty"`
 	ServiceTier     string         `json:"service_tier,omitempty"`
 	ReasoningEffort string         `json:"reasoning_effort,omitempty"`
 	APIKeyEnv       string         `json:"api_key_env,omitempty"`
-	ExtraParams     map[string]string `json:"extra_params,omitempty"`
+	ExtraParams     map[string]any `json:"extra_params,omitempty"`
 }
 
 type runResponseDTO struct {
@@ -79,13 +79,15 @@ type modelParamsDTO struct {
 	ServiceTier     string         `json:"service_tier,omitempty"`
 	ReasoningEffort string         `json:"reasoning_effort,omitempty"`
 	APIKeyEnv       string         `json:"api_key_env,omitempty"`
-	ExtraParams     map[string]string `json:"extra_params,omitempty"`
+	ExtraParams     map[string]any `json:"extra_params,omitempty"`
 }
 
 type tokenUsageDTO struct {
 	PromptTokens     int `json:"prompt_tokens"`
 	CompletionTokens int `json:"completion_tokens"`
 	TotalTokens      int `json:"total_tokens"`
+	CachedTokens     int `json:"cached_tokens"`
+	CacheWriteTokens int `json:"cache_write_tokens"`
 }
 
 type validationDTO struct {

internal/adapter/http/handler.go

@@ -4,9 +4,12 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"io"
 	"net/http"
 	"strings"
 
+	"gitea.maximumdirect.net/eric/scriptorium/internal/artifact"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
@@ -19,10 +22,23 @@ type Runner interface {
 
 type Handler struct {
 	runner  Runner
+	options HandlerOptions
+}
+
+type HandlerOptions struct {
+	MaxRequestBytes  int64
+	MaxResponseBytes int64
 }
 
 func NewHandler(runner Runner) *Handler {
-	return &Handler{runner: runner}
+	return NewHandlerWithOptions(runner, HandlerOptions{
+		MaxRequestBytes:  defaults.HTTPMaxRequestBytesDefault,
+		MaxResponseBytes: defaults.HTTPMaxResponseBytesDefault,
+	})
+}
+
+func NewHandlerWithOptions(runner Runner, options HandlerOptions) *Handler {
+	return &Handler{runner: runner, options: options}
 }
 
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -36,9 +52,26 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	}
 
 	var req runRequestDTO
-	dec := json.NewDecoder(r.Body)
+	body := r.Body
+	if h.options.MaxRequestBytes > 0 {
+		body = http.MaxBytesReader(w, r.Body, h.options.MaxRequestBytes)
+	}
+	dec := json.NewDecoder(body)
 	dec.DisallowUnknownFields()
 	if err := dec.Decode(&req); err != nil {
+		if isRequestTooLarge(err) {
+			writeError(w, http.StatusRequestEntityTooLarge, "request_too_large", "request body is too large")
+			return
+		}
+		writeError(w, http.StatusBadRequest, "invalid_json", "invalid JSON request body")
+		return
+	}
+	var trailing any
+	if err := dec.Decode(&trailing); err != io.EOF {
+		if isRequestTooLarge(err) {
+			writeError(w, http.StatusRequestEntityTooLarge, "request_too_large", "request body is too large")
+			return
+		}
 		writeError(w, http.StatusBadRequest, "invalid_json", "invalid JSON request body")
 		return
 	}
@@ -61,9 +94,9 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 
-	var model *domain.ExecutionTarget
+	var model *domain.ExecutionTargetOverride
 	if req.Model != nil {
-		model = executionTargetFromModelOverrideDTO(req.Model)
+		model = executionTargetOverrideFromModelOverrideDTO(req.Model)
 	}
 
 	res, err := h.runner.Run(r.Context(), domain.RunRequest{
@@ -105,6 +138,8 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 				PromptTokens:     res.Usage.PromptTokens,
 				CompletionTokens: res.Usage.CompletionTokens,
 				TotalTokens:      res.Usage.TotalTokens,
+				CachedTokens:     res.Usage.CachedTokens,
+				CacheWriteTokens: res.Usage.CacheWriteTokens,
 			},
 			StartTime:          res.StartTime,
 			EndTime:            res.EndTime,
@@ -118,14 +153,14 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		raw := res.RawOutput
 		resp.RawModelOutput = &raw
 	}
-	writeJSON(w, http.StatusOK, resp)
+	writeLimitedJSON(w, http.StatusOK, resp, h.options.MaxResponseBytes)
 }
 
-func executionTargetFromModelOverrideDTO(dto *modelOverrideRequestDTO) *domain.ExecutionTarget {
+func executionTargetOverrideFromModelOverrideDTO(dto *modelOverrideRequestDTO) *domain.ExecutionTargetOverride {
 	if dto == nil {
 		return nil
 	}
-	return &domain.ExecutionTarget{
+	return &domain.ExecutionTargetOverride{
 		Endpoint:        dto.Endpoint,
 		Model:           dto.Model,
 		Temperature:     dto.Temperature,
@@ -173,7 +208,7 @@ func mapRunError(err error) (int, string, string) {
 		return http.StatusNotFound, "profile_not_found", "execution profile not found"
 	case errors.Is(err, promptdef.ErrInvalidYAML), errors.Is(err, promptdef.ErrInvalidPromptDefinition):
 		return http.StatusBadRequest, "prompt_load_failed", "failed to load prompt definition"
-	case errors.Is(err, profile.ErrInvalidYAML), errors.Is(err, profile.ErrInvalidProfile):
+	case errors.Is(err, profile.ErrInvalidYAML), errors.Is(err, profile.ErrInvalidProfile), errors.Is(err, profile.ErrRawAPIKeyNotAllowed):
 		return http.StatusBadRequest, "profile_load_failed", "failed to load execution profile"
 	case errors.Is(err, usecase.ErrProfileRequired):
 		return http.StatusBadRequest, "profile_required", "profile_id is required when prompt default_profile is not set"
@@ -181,8 +216,14 @@ func mapRunError(err error) (int, string, string) {
 		return http.StatusBadRequest, "api_key_env_missing", "api_key_env is set but the environment variable is missing"
 	case errors.Is(err, usecase.ErrInvalidRequest):
 		return http.StatusBadRequest, "invalid_request", "invalid run request"
-	case errors.Is(err, usecase.ErrProfileLoad):
+	case errors.Is(err, usecase.ErrPromptLoad):
 		return http.StatusBadRequest, "prompt_load_failed", "failed to load prompt definition"
+	case errors.Is(err, usecase.ErrProfileLoad):
+		return http.StatusBadRequest, "profile_load_failed", "failed to load execution profile"
+	case errors.Is(err, artifact.ErrFileNotAllowed), errors.Is(err, artifact.ErrFileOutsideRoot):
+		return http.StatusBadRequest, "artifact_not_allowed", "file input artifact is not allowed"
+	case errors.Is(err, artifact.ErrFileTooLarge):
+		return http.StatusRequestEntityTooLarge, "artifact_too_large", "file input artifact is too large"
 	case errors.Is(err, usecase.ErrArtifactLoad):
 		return http.StatusBadRequest, "artifact_read_failed", "failed to read input artifact"
 	case errors.Is(err, usecase.ErrPromptRender):
@@ -197,9 +238,23 @@ func mapRunError(err error) (int, string, string) {
 }
 
 func writeJSON(w http.ResponseWriter, status int, v any) {
+	writeLimitedJSON(w, status, v, 0)
+}
+
+func writeLimitedJSON(w http.ResponseWriter, status int, v any, maxBytes int64) {
+	data, err := json.Marshal(v)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, "internal_error", "internal server error")
+		return
+	}
+	data = append(data, '\n')
+	if maxBytes > 0 && int64(len(data)) > maxBytes {
+		writeError(w, http.StatusRequestEntityTooLarge, "response_too_large", "response body is too large")
+		return
+	}
 	w.Header().Set("Content-Type", "application/json")
 	w.WriteHeader(status)
-	_ = json.NewEncoder(w).Encode(v)
+	_, _ = w.Write(data)
 }
 
 func writeError(w http.ResponseWriter, status int, code, message string) {
@@ -210,3 +265,8 @@ func writeError(w http.ResponseWriter, status int, code, message string) {
 		},
 	})
 }
+
+func isRequestTooLarge(err error) bool {
+	var maxBytesErr *http.MaxBytesError
+	return errors.As(err, &maxBytesErr)
+}

internal/adapter/http/handler_test.go

@@ -7,12 +7,16 @@ import (
 	"fmt"
 	"net/http"
 	"net/http/httptest"
+	"os"
+	"path/filepath"
 	"reflect"
 	"strings"
 	"testing"
 	"time"
 
+	"gitea.maximumdirect.net/eric/scriptorium/internal/artifact"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/usecase"
@@ -32,6 +36,40 @@ func (f *fakeRunner) Run(ctx context.Context, req domain.RunRequest) (*domain.Ru
 	return f.result, nil
 }
 
+type handlerPromptRepo struct {
+	def *domain.PromptDefinition
+}
+
+func (r handlerPromptRepo) GetPromptDefinition(ctx context.Context, id string, version string) (*domain.PromptDefinition, error) {
+	return r.def, nil
+}
+
+type handlerProfileRepo struct {
+	profile *domain.ExecutionProfile
+}
+
+func (r handlerProfileRepo) GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error) {
+	return r.profile, nil
+}
+
+type handlerArtifactReader struct{}
+
+func (handlerArtifactReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	return &domain.Artifact{Name: "input", Body: []byte("input"), Hash: "hash"}, nil
+}
+
+type handlerRenderer struct{}
+
+func (handlerRenderer) Render(ctx context.Context, definition *domain.PromptDefinition, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error) {
+	return &domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}}, nil
+}
+
+type handlerLLMClient struct{}
+
+func (handlerLLMClient) Generate(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error) {
+	return &domain.GenerateResponse{Content: "ok"}, nil
+}
+
 func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 	start := time.Now().UTC()
 	end := start.Add(2 * time.Second)
@@ -66,7 +104,13 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 			APIKeyEnv:      envName,
 		},
 		InputHashes: map[string]string{"transcript": "h1"},
-		Usage:       domain.TokenUsage{PromptTokens: 1, CompletionTokens: 2, TotalTokens: 3},
+		Usage: domain.TokenUsage{
+			PromptTokens:     1,
+			CompletionTokens: 2,
+			TotalTokens:      3,
+			CachedTokens:     4,
+			CacheWriteTokens: 5,
+		},
 		StartTime: start,
 		EndTime:   end,
 		Duration:  2 * time.Second,
@@ -111,6 +155,13 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 	if metadata["model_name"] != "m1" || metadata["endpoint"] != "http://llm/v1" {
 		t.Fatalf("unexpected model metadata: name=%#v endpoint=%#v", metadata["model_name"], metadata["endpoint"])
 	}
+	usage := metadata["usage"].(map[string]any)
+	if usage["prompt_tokens"] != float64(1) || usage["completion_tokens"] != float64(2) || usage["total_tokens"] != float64(3) {
+		t.Fatalf("unexpected base usage metadata: %#v", usage)
+	}
+	if usage["cached_tokens"] != float64(4) || usage["cache_write_tokens"] != float64(5) {
+		t.Fatalf("unexpected cache usage metadata: %#v", usage)
+	}
 	modelParams := metadata["model_params"].(map[string]any)
 	if modelParams["api_key_env"] != envName {
 		t.Fatalf("expected model_params.api_key_env=%q, got %#v", envName, modelParams["api_key_env"])
@@ -134,7 +185,7 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 	if r.last.Execution == nil || r.last.Execution.Model != "gpt-x" {
 		t.Fatalf("expected model override, got %#v", r.last.Execution)
 	}
-	if r.last.Execution.TimeoutSeconds != 120 {
+	if r.last.Execution.TimeoutSeconds == nil || *r.last.Execution.TimeoutSeconds != 120 {
 		t.Fatalf("expected timeout_seconds override 120, got %#v", r.last.Execution)
 	}
 	if r.last.Execution.ServiceTier != "flex" {
@@ -142,6 +193,105 @@ func TestHandlerPostRunsSuccessWithExplicitProfileID(t *testing.T) {
 	}
 }
 
+func TestHandlerInlineRefsWorkWithoutArtifactRoot(t *testing.T) {
+	h := newArtifactRootHandler(t, "")
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"inline","body":"inline body"}}
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+}
+
+func TestHandlerFileRefsWithoutArtifactRootAreRejected(t *testing.T) {
+	h := newArtifactRootHandler(t, "")
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"file","uri":"input.txt"}}
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusBadRequest, "artifact_not_allowed")
+}
+
+func TestHandlerFileRefsUnderArtifactRootWork(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "input.txt"), []byte("allowed"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	h := newArtifactRootHandler(t, root)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"file","uri":"input.txt"}}
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+}
+
+func TestHandlerFileRefsAboveArtifactLimitAreRejected(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "large.txt"), []byte("123456"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	h := newArtifactRootHandlerWithLimit(t, root, 5)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"file","uri":"large.txt"}}
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusRequestEntityTooLarge, "artifact_too_large")
+}
+
+func TestHandlerFileRefsOutsideArtifactRootAreRejected(t *testing.T) {
+	root := t.TempDir()
+	outside := t.TempDir()
+	if err := os.WriteFile(filepath.Join(outside, "secret.txt"), []byte("denied"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	h := newArtifactRootHandler(t, root)
+
+	tests := []struct {
+		name string
+		uri  string
+	}{
+		{name: "relative traversal", uri: filepath.Join("..", filepath.Base(outside), "secret.txt")},
+		{name: "absolute outside root", uri: filepath.Join(outside, "secret.txt")},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			body := fmt.Sprintf(`{
+				"prompt_id":"p",
+				"inputs":{"x":{"type":"file","uri":%q}}
+			}`, tc.uri)
+			req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(body))
+			w := httptest.NewRecorder()
+
+			h.ServeHTTP(w, req)
+
+			assertHTTPErrorCode(t, w, http.StatusBadRequest, "artifact_not_allowed")
+		})
+	}
+}
+
 func TestHandlerPostRunsSuccessUsingPromptDefaultProfile(t *testing.T) {
 	r := &fakeRunner{result: &domain.RunResult{
 		Artifact:             domain.Artifact{Body: []byte("ok")},
@@ -171,6 +321,10 @@ func TestHandlerPostRunsSuccessUsingPromptDefaultProfile(t *testing.T) {
 	if metadata["selected_profile_id"] != "prompt-default" {
 		t.Fatalf("expected selected_profile_id from result, got %#v", metadata["selected_profile_id"])
 	}
+	usage := metadata["usage"].(map[string]any)
+	if usage["cached_tokens"] != float64(0) || usage["cache_write_tokens"] != float64(0) {
+		t.Fatalf("expected zero cache usage fields to be included, got %#v", usage)
+	}
 }
 
 func TestHandlerModelOverrideMapsAllSupportedExecutionFields(t *testing.T) {
@@ -211,20 +365,136 @@ func TestHandlerModelOverrideMapsAllSupportedExecutionFields(t *testing.T) {
 	got := r.last.Execution
 	if got.Endpoint != "http://override/v1" ||
 		got.Model != "override-model" ||
-		got.Temperature != 0.6 ||
-		got.MaxTokens != 250 ||
-		got.TopP != 0.85 ||
-		got.TimeoutSeconds != 33 ||
 		got.ServiceTier != "flex" ||
 		got.ReasoningEffort != "medium" ||
 		got.APIKeyEnv != "SCRIPTORIUM_API_KEY" {
 		t.Fatalf("unexpected mapped execution target: %+v", got)
 	}
-	if !reflect.DeepEqual(got.ExtraParams, map[string]string{"provider_option": "on"}) {
+	if got.Temperature == nil || *got.Temperature != 0.6 {
+		t.Fatalf("unexpected mapped temperature: %#v", got.Temperature)
+	}
+	if got.MaxTokens == nil || *got.MaxTokens != 250 {
+		t.Fatalf("unexpected mapped max_tokens: %#v", got.MaxTokens)
+	}
+	if got.TopP == nil || *got.TopP != 0.85 {
+		t.Fatalf("unexpected mapped top_p: %#v", got.TopP)
+	}
+	if got.TimeoutSeconds == nil || *got.TimeoutSeconds != 33 {
+		t.Fatalf("unexpected mapped timeout_seconds: %#v", got.TimeoutSeconds)
+	}
+	if !reflect.DeepEqual(got.ExtraParams, map[string]any{"provider_option": "on"}) {
 		t.Fatalf("unexpected mapped extra_params: %#v", got.ExtraParams)
 	}
 }
 
+func TestHandlerModelOverrideAcceptsJSONCompatibleExtraParams(t *testing.T) {
+	r := &fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte("ok")},
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1"},
+	}}
+	h := NewHandler(r)
+
+	reqBody := `{
+		"prompt_id": "prompt-1",
+		"inputs": {"transcript": {"type": "file", "uri": "./t.md"}},
+		"model": {
+			"extra_params": {
+				"string_value": "enabled",
+				"number_value": 42,
+				"boolean_value": true,
+				"object_value": {"nested": "value", "count": 2},
+				"array_value": ["first", 3, false]
+			}
+		}
+	}`
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(reqBody))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+	if r.last.Execution == nil {
+		t.Fatal("expected execution override in run request")
+	}
+	want := map[string]any{
+		"string_value":  "enabled",
+		"number_value":  float64(42),
+		"boolean_value": true,
+		"object_value":  map[string]any{"nested": "value", "count": float64(2)},
+		"array_value":   []any{"first", float64(3), false},
+	}
+	if !reflect.DeepEqual(r.last.Execution.ExtraParams, want) {
+		t.Fatalf("unexpected mapped extra_params:\ngot=%#v\nwant=%#v", r.last.Execution.ExtraParams, want)
+	}
+}
+
+func TestHandlerModelOverrideExplicitZeroTemperatureMapsAsPresent(t *testing.T) {
+	r := &fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte("ok")},
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1", Temperature: 0},
+	}}
+	h := NewHandler(r)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id": "prompt-1",
+		"inputs": {"transcript": {"type": "file", "uri": "./t.md"}},
+		"model": {"temperature": 0}
+	}`))
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+	if r.last.Execution == nil || r.last.Execution.Temperature == nil {
+		t.Fatalf("expected temperature override to be present, got %#v", r.last.Execution)
+	}
+	if *r.last.Execution.Temperature != 0 {
+		t.Fatalf("expected zero temperature override, got %v", *r.last.Execution.Temperature)
+	}
+}
+
+func TestHandlerModelOverrideOmittedTemperatureMapsAsAbsent(t *testing.T) {
+	r := &fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte("ok")},
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1", Temperature: 0.7},
+	}}
+	h := NewHandler(r)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id": "prompt-1",
+		"inputs": {"transcript": {"type": "file", "uri": "./t.md"}},
+		"model": {"model": "override-model"}
+	}`))
+	w := httptest.NewRecorder()
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusOK {
+		t.Fatalf("expected 200, got %d body=%s", w.Code, w.Body.String())
+	}
+	if r.last.Execution == nil {
+		t.Fatal("expected model override")
+	}
+	if r.last.Execution.Temperature != nil {
+		t.Fatalf("expected omitted temperature to remain absent, got %#v", r.last.Execution.Temperature)
+	}
+
+	var resp map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("invalid JSON response: %v", err)
+	}
+	metadata := resp["metadata"].(map[string]any)
+	params := metadata["model_params"].(map[string]any)
+	if params["temperature"] != 0.7 {
+		t.Fatalf("expected effective profile/default temperature in response, got %#v", params["temperature"])
+	}
+}
+
 func TestHandlerResponseMetadataModelParamsIncludesAllSupportedFields(t *testing.T) {
 	r := &fakeRunner{result: &domain.RunResult{
 		Artifact: domain.Artifact{
@@ -245,8 +515,10 @@ func TestHandlerResponseMetadataModelParamsIncludesAllSupportedFields(t *testing
 			ServiceTier:     "priority",
 			ReasoningEffort: "high",
 			APIKeyEnv:       "SCRIPTORIUM_API_KEY",
-			ExtraParams: map[string]string{
+			ExtraParams: map[string]any{
 				"provider_option": "on",
+				"number_value":    42,
+				"object_value":    map[string]any{"nested": "value"},
 			},
 		},
 	}}
@@ -301,6 +573,13 @@ func TestHandlerResponseMetadataModelParamsIncludesAllSupportedFields(t *testing
 	if extraParams["provider_option"] != "on" {
 		t.Fatalf("unexpected extra_params.provider_option: %#v", extraParams["provider_option"])
 	}
+	if extraParams["number_value"] != float64(42) {
+		t.Fatalf("unexpected extra_params.number_value: %#v", extraParams["number_value"])
+	}
+	objectValue, ok := extraParams["object_value"].(map[string]any)
+	if !ok || objectValue["nested"] != "value" {
+		t.Fatalf("unexpected extra_params.object_value: %#v", extraParams["object_value"])
+	}
 }
 
 func TestHandlerInvalidJSON(t *testing.T) {
@@ -315,6 +594,69 @@ func TestHandlerInvalidJSON(t *testing.T) {
 	}
 }
 
+func TestHandlerRejectsTrailingJSON(t *testing.T) {
+	h := NewHandler(&fakeRunner{})
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{"prompt_id":"p","inputs":{"x":{"type":"file","uri":"a"}}} {}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusBadRequest, "invalid_json")
+}
+
+func TestHandlerRequestTooLarge(t *testing.T) {
+	h := NewHandlerWithOptions(&fakeRunner{}, HandlerOptions{MaxRequestBytes: 12})
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{"prompt_id":"p","inputs":{"x":{"type":"file","uri":"a"}}}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusRequestEntityTooLarge, "request_too_large")
+}
+
+func TestHandlerMalformedJSONBelowLimitStillBadRequest(t *testing.T) {
+	h := NewHandlerWithOptions(&fakeRunner{}, HandlerOptions{MaxRequestBytes: 1024})
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString("{"))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusBadRequest, "invalid_json")
+}
+
+func TestHandlerResponseTooLarge(t *testing.T) {
+	h := NewHandlerWithOptions(&fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte(strings.Repeat("x", 128))},
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1"},
+	}}, HandlerOptions{MaxRequestBytes: 1024, MaxResponseBytes: 64})
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{"prompt_id":"p","inputs":{"x":{"type":"file","uri":"a"}}}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusRequestEntityTooLarge, "response_too_large")
+}
+
+func TestHandlerRawOutputDoesNotBypassResponseLimit(t *testing.T) {
+	h := NewHandlerWithOptions(&fakeRunner{result: &domain.RunResult{
+		Artifact:             domain.Artifact{Body: []byte("ok")},
+		RawOutput:            strings.Repeat("raw", 80),
+		Validation:           domain.ValidationResult{Status: domain.ValidationPassed, Mode: domain.ValidationBasic, IsValid: true},
+		EffectiveModelParams: domain.ExecutionTarget{Endpoint: "http://llm/v1", Model: "m1"},
+	}}, HandlerOptions{MaxRequestBytes: 1024, MaxResponseBytes: 128})
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"file","uri":"a"}},
+		"include_raw_output":true
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	assertHTTPErrorCode(t, w, http.StatusRequestEntityTooLarge, "response_too_large")
+}
+
 func TestHandlerMissingPromptID(t *testing.T) {
 	h := NewHandler(&fakeRunner{})
 	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{"inputs":{"x":{"type":"file","uri":"a"}}}`))
@@ -335,6 +677,54 @@ func TestHandlerMissingPromptID(t *testing.T) {
 	}
 }
 
+func TestHandlerReservedExtraParamsThroughRunnerMapsToInvalidRequest(t *testing.T) {
+	llmClient, err := llm.NewOpenAICompatibleClient(llm.OpenAICompatibleConfig{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	runner := usecase.NewRunner(
+		handlerPromptRepo{def: &domain.PromptDefinition{
+			ID:             "p",
+			Version:        "1",
+			DefaultProfile: "exec",
+			Templates:      []domain.PromptMessageTemplate{{Role: "user", Content: "hi"}},
+			OutputFormat:   domain.FormatText,
+			Validation:     domain.OutputContract{Format: domain.FormatText, ValidationMode: domain.ValidationNone},
+		}},
+		handlerProfileRepo{profile: &domain.ExecutionProfile{
+			ID:       "exec",
+			Endpoint: "http://example.invalid/v1",
+			Model:    "model",
+		}},
+		handlerArtifactReader{},
+		handlerRenderer{},
+		llmClient,
+		nil,
+	)
+	h := NewHandler(runner)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/runs", bytes.NewBufferString(`{
+		"prompt_id":"p",
+		"inputs":{"x":{"type":"file","uri":"a"}},
+		"model":{"extra_params":{"model":"collision"}}
+	}`))
+	w := httptest.NewRecorder()
+
+	h.ServeHTTP(w, req)
+
+	if w.Code != http.StatusBadRequest {
+		t.Fatalf("expected 400, got %d body=%s", w.Code, w.Body.String())
+	}
+	var resp map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("invalid JSON response: %v", err)
+	}
+	errBody := resp["error"].(map[string]any)
+	if errBody["code"] != "invalid_request" {
+		t.Fatalf("expected invalid_request code, got %#v", errBody["code"])
+	}
+}
+
 func TestHandlerUsecaseErrorMapping(t *testing.T) {
 	tests := []struct {
 		name       string
@@ -344,11 +734,13 @@ func TestHandlerUsecaseErrorMapping(t *testing.T) {
 		message    string
 		avoidCause string
 	}{
-		{name: "prompt not found", err: wrap(usecase.ErrProfileLoad, promptdef.ErrPromptDefinitionNotFound), status: http.StatusNotFound, code: "prompt_not_found", message: "prompt definition not found"},
+		{name: "prompt not found", err: wrap(usecase.ErrPromptLoad, promptdef.ErrPromptDefinitionNotFound), status: http.StatusNotFound, code: "prompt_not_found", message: "prompt definition not found"},
-		{name: "prompt load invalid", err: wrap(usecase.ErrProfileLoad, promptdef.ErrInvalidPromptDefinition), status: http.StatusBadRequest, code: "prompt_load_failed", message: "failed to load prompt definition"},
+		{name: "prompt load invalid", err: wrap(usecase.ErrPromptLoad, promptdef.ErrInvalidPromptDefinition), status: http.StatusBadRequest, code: "prompt_load_failed", message: "failed to load prompt definition"},
+		{name: "prompt load generic", err: wrap(usecase.ErrPromptLoad, fmt.Errorf("read failed")), status: http.StatusBadRequest, code: "prompt_load_failed", message: "failed to load prompt definition", avoidCause: "read failed"},
 		{name: "missing profile/default", err: wrap(usecase.ErrInvalidRequest, usecase.ErrProfileRequired), status: http.StatusBadRequest, code: "profile_required", message: "profile_id is required when prompt default_profile is not set"},
 		{name: "profile not found", err: wrap(usecase.ErrProfileLoad, profile.ErrProfileNotFound), status: http.StatusNotFound, code: "profile_not_found", message: "execution profile not found"},
 		{name: "profile invalid", err: wrap(usecase.ErrProfileLoad, profile.ErrInvalidProfile), status: http.StatusBadRequest, code: "profile_load_failed", message: "failed to load execution profile"},
+		{name: "profile load generic", err: wrap(usecase.ErrProfileLoad, fmt.Errorf("read failed")), status: http.StatusBadRequest, code: "profile_load_failed", message: "failed to load execution profile", avoidCause: "read failed"},
 		{name: "api key env missing", err: wrap(usecase.ErrInvalidRequest, usecase.ErrAPIKeyEnvMissing), status: http.StatusBadRequest, code: "api_key_env_missing", message: "api_key_env is set but the environment variable is missing"},
 		{name: "artifact", err: wrap(usecase.ErrArtifactLoad, fmt.Errorf("read failed")), status: http.StatusBadRequest, code: "artifact_read_failed", message: "failed to read input artifact", avoidCause: "read failed"},
 		{name: "prompt render", err: wrap(usecase.ErrPromptRender, fmt.Errorf("render failed")), status: http.StatusBadRequest, code: "prompt_render_failed", message: "failed to render prompt", avoidCause: "render failed"},
@@ -455,3 +847,54 @@ func TestHandlerValidationFailureStillSuccessAndRawOutputOptIn(t *testing.T) {
 func wrap(stage error, cause error) error {
 	return fmt.Errorf("%w: %w", stage, cause)
 }
+
+func newArtifactRootHandler(t *testing.T, root string) *Handler {
+	t.Helper()
+
+	return newArtifactRootHandlerWithLimit(t, root, 0)
+}
+
+func newArtifactRootHandlerWithLimit(t *testing.T, root string, maxArtifactBytes int64) *Handler {
+	t.Helper()
+
+	reader, err := artifact.NewRestrictedCompositeReaderWithLimit(root, maxArtifactBytes)
+	if err != nil {
+		t.Fatalf("expected restricted artifact reader: %v", err)
+	}
+	runner := usecase.NewRunner(
+		handlerPromptRepo{def: &domain.PromptDefinition{
+			ID:             "p",
+			Version:        "1",
+			DefaultProfile: "exec",
+			Templates:      []domain.PromptMessageTemplate{{Role: "user", Content: "hi"}},
+			OutputFormat:   domain.FormatText,
+			Validation:     domain.OutputContract{Format: domain.FormatText, ValidationMode: domain.ValidationNone},
+		}},
+		handlerProfileRepo{profile: &domain.ExecutionProfile{
+			ID:       "exec",
+			Endpoint: "http://example.invalid/v1",
+			Model:    "model",
+		}},
+		reader,
+		handlerRenderer{},
+		handlerLLMClient{},
+		nil,
+	)
+	return NewHandler(runner)
+}
+
+func assertHTTPErrorCode(t *testing.T, w *httptest.ResponseRecorder, status int, code string) {
+	t.Helper()
+
+	if w.Code != status {
+		t.Fatalf("expected %d, got %d body=%s", status, w.Code, w.Body.String())
+	}
+	var resp map[string]any
+	if err := json.Unmarshal(w.Body.Bytes(), &resp); err != nil {
+		t.Fatalf("invalid JSON response: %v", err)
+	}
+	errBody := resp["error"].(map[string]any)
+	if errBody["code"] != code {
+		t.Fatalf("expected code %q, got %#v", code, errBody["code"])
+	}
+}

internal/artifact/reader.go

@@ -7,15 +7,20 @@ import (
 	"fmt"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"io"
 	"mime"
 	"os"
 	"path/filepath"
+	"strings"
 )
 
 var (
 	ErrUnsupportedRefType = errors.New("unsupported artifact reference type")
 	ErrMissingInlineBody  = errors.New("missing body for inline artifact")
 	ErrMissingFilePath    = errors.New("missing file path for file artifact")
+	ErrFileNotAllowed     = errors.New("file artifact references are not allowed")
+	ErrFileOutsideRoot    = errors.New("file artifact path is outside artifact root")
+	ErrFileTooLarge       = errors.New("file artifact exceeds size limit")
 )
 
 // Reader resolves artifact references into actual artifacts.
@@ -26,7 +31,7 @@ type Reader interface {
 // CompositeReader routes artifact resolution based on the reference type.
 type CompositeReader struct {
 	inlineReader *inlineReader
-	fileReader   *fileReader
+	fileReader   Reader
 }
 
 func NewCompositeReader() Reader {
@@ -36,6 +41,21 @@ func NewCompositeReader() Reader {
 	}
 }
 
+func NewRestrictedCompositeReader(root string) (Reader, error) {
+	return NewRestrictedCompositeReaderWithLimit(root, 0)
+}
+
+func NewRestrictedCompositeReaderWithLimit(root string, maxBytes int64) (Reader, error) {
+	fileReader, err := newRestrictedFileReader(root, maxBytes)
+	if err != nil {
+		return nil, err
+	}
+	return &CompositeReader{
+		inlineReader: &inlineReader{},
+		fileReader:   fileReader,
+	}, nil
+}
+
 func (c *CompositeReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
 	select {
 	case <-ctx.Done():
@@ -89,21 +109,133 @@ func (r *fileReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.
 		return nil, ErrMissingFilePath
 	}
 
-	data, err := os.ReadFile(ref.URI)
+	return readFileArtifact(ref.URI)
-	if err != nil {
-		return nil, fmt.Errorf("failed to read file %s: %w", ref.URI, err)
 }
 
-	contentType := mime.TypeByExtension(filepath.Ext(ref.URI))
+type deniedFileReader struct{}
+
+func (r deniedFileReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if ref.URI == "" {
+		return nil, ErrMissingFilePath
+	}
+	return nil, ErrFileNotAllowed
+}
+
+type restrictedFileReader struct {
+	root     string
+	maxBytes int64
+}
+
+func newRestrictedFileReader(root string, maxBytes int64) (Reader, error) {
+	if maxBytes < 0 {
+		return nil, fmt.Errorf("artifact size limit must be greater than or equal to 0")
+	}
+	cleanRoot := strings.TrimSpace(root)
+	if cleanRoot == "" {
+		return deniedFileReader{}, nil
+	}
+	absRoot, err := filepath.Abs(filepath.Clean(cleanRoot))
+	if err != nil {
+		return nil, fmt.Errorf("resolve artifact root: %w", err)
+	}
+	return &restrictedFileReader{root: absRoot, maxBytes: maxBytes}, nil
+}
+
+func (r *restrictedFileReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if ref.URI == "" {
+		return nil, ErrMissingFilePath
+	}
+
+	path, err := r.resolveLexicalPath(ref.URI)
+	if err != nil {
+		return nil, err
+	}
+	return readFileArtifactWithLimit(path, r.maxBytes)
+}
+
+// resolveLexicalPath checks cleaned path containment without resolving symlinks.
+func (r *restrictedFileReader) resolveLexicalPath(rawPath string) (string, error) {
+	cleanPath := filepath.Clean(strings.TrimSpace(rawPath))
+	var candidate string
+	if filepath.IsAbs(cleanPath) {
+		candidate = cleanPath
+	} else {
+		candidate = filepath.Join(r.root, cleanPath)
+	}
+
+	absCandidate, err := filepath.Abs(candidate)
+	if err != nil {
+		return "", fmt.Errorf("resolve artifact path: %w", err)
+	}
+	absCandidate = filepath.Clean(absCandidate)
+
+	rel, err := filepath.Rel(r.root, absCandidate)
+	if err != nil {
+		return "", fmt.Errorf("compare artifact path to root: %w", err)
+	}
+	if rel == ".." || strings.HasPrefix(rel, ".."+string(filepath.Separator)) || filepath.IsAbs(rel) {
+		return "", ErrFileOutsideRoot
+	}
+	return absCandidate, nil
+}
+
+func readFileArtifact(path string) (*domain.Artifact, error) {
+	return readFileArtifactWithLimit(path, 0)
+}
+
+func readFileArtifactWithLimit(path string, maxBytes int64) (*domain.Artifact, error) {
+	if maxBytes < 0 {
+		return nil, fmt.Errorf("file size limit must be greater than or equal to 0")
+	}
+
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+	defer file.Close()
+
+	info, err := file.Stat()
+	if err != nil {
+		return nil, fmt.Errorf("failed to stat file %s: %w", path, err)
+	}
+	if maxBytes > 0 && info.Size() > maxBytes {
+		return nil, ErrFileTooLarge
+	}
+
+	var reader io.Reader = file
+	if maxBytes > 0 {
+		reader = io.LimitReader(file, maxBytes+1)
+	}
+	data, err := io.ReadAll(reader)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+	if maxBytes > 0 && int64(len(data)) > maxBytes {
+		return nil, ErrFileTooLarge
+	}
+
+	contentType := mime.TypeByExtension(filepath.Ext(path))
 	if contentType == "" {
 		contentType = defaults.ContentTypeTextPlain
 	}
 
 	return &domain.Artifact{
-		Name:        filepath.Base(ref.URI),
+		Name:        filepath.Base(path),
 		ContentType: contentType,
 		Body:        data,
-		URI:         ref.URI,
+		URI:         path,
 		Size:        int64(len(data)),
 		Hash:        fmt.Sprintf("%x", sha256.Sum256(data)),
 	}, nil

internal/artifact/reader_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"os"
+	"path/filepath"
 	"testing"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
@@ -56,6 +57,157 @@ func TestCompositeReader_Read(t *testing.T) {
 	})
 }
 
+func TestRestrictedCompositeReader(t *testing.T) {
+	ctx := context.Background()
+	root := t.TempDir()
+	outside := t.TempDir()
+
+	if err := os.WriteFile(filepath.Join(root, "input.txt"), []byte("allowed"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Mkdir(filepath.Join(root, "nested"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(outside, "secret.txt"), []byte("denied"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	reader, err := NewRestrictedCompositeReader(root)
+	if err != nil {
+		t.Fatalf("expected restricted reader construction, got %v", err)
+	}
+
+	t.Run("accepts relative contained path", func(t *testing.T) {
+		art, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "nested/../input.txt"})
+		if err != nil {
+			t.Fatalf("expected contained relative path to succeed, got %v", err)
+		}
+		if string(art.Body) != "allowed" {
+			t.Fatalf("unexpected artifact body: %q", string(art.Body))
+		}
+	})
+
+	t.Run("accepts absolute contained path", func(t *testing.T) {
+		art, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: filepath.Join(root, "input.txt")})
+		if err != nil {
+			t.Fatalf("expected contained absolute path to succeed, got %v", err)
+		}
+		if art.Name != "input.txt" {
+			t.Fatalf("unexpected artifact name: %q", art.Name)
+		}
+	})
+
+	t.Run("rejects relative traversal outside root", func(t *testing.T) {
+		_, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: filepath.Join("..", filepath.Base(outside), "secret.txt")})
+		if !errors.Is(err, ErrFileOutsideRoot) {
+			t.Fatalf("expected ErrFileOutsideRoot, got %v", err)
+		}
+	})
+
+	t.Run("rejects absolute path outside root", func(t *testing.T) {
+		_, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: filepath.Join(outside, "secret.txt")})
+		if !errors.Is(err, ErrFileOutsideRoot) {
+			t.Fatalf("expected ErrFileOutsideRoot, got %v", err)
+		}
+	})
+}
+
+func TestRestrictedCompositeReaderFollowsSymlinkInsideRoot(t *testing.T) {
+	ctx := context.Background()
+	root := t.TempDir()
+	outside := t.TempDir()
+
+	target := filepath.Join(outside, "linked.txt")
+	if err := os.WriteFile(target, []byte("linked outside root"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	link := filepath.Join(root, "linked.txt")
+	if err := os.Symlink(target, link); err != nil {
+		t.Skipf("symlink creation unavailable: %v", err)
+	}
+
+	reader, err := NewRestrictedCompositeReader(root)
+	if err != nil {
+		t.Fatalf("expected restricted reader construction, got %v", err)
+	}
+
+	art, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "linked.txt"})
+	if err != nil {
+		t.Fatalf("expected symlink inside root to be followed, got %v", err)
+	}
+	if string(art.Body) != "linked outside root" {
+		t.Fatalf("unexpected artifact body: %q", string(art.Body))
+	}
+}
+
+func TestRestrictedCompositeReaderWithoutRootDeniesFileRefs(t *testing.T) {
+	reader, err := NewRestrictedCompositeReader("")
+	if err != nil {
+		t.Fatalf("expected restricted reader construction, got %v", err)
+	}
+
+	art, err := reader.Read(context.Background(), domain.ArtifactRef{Type: domain.ArtifactRefInline, Body: "inline"})
+	if err != nil {
+		t.Fatalf("expected inline ref to work without artifact root, got %v", err)
+	}
+	if string(art.Body) != "inline" {
+		t.Fatalf("unexpected inline body: %q", string(art.Body))
+	}
+
+	_, err = reader.Read(context.Background(), domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "input.txt"})
+	if !errors.Is(err, ErrFileNotAllowed) {
+		t.Fatalf("expected ErrFileNotAllowed, got %v", err)
+	}
+}
+
+func TestRestrictedCompositeReaderFileSizeLimit(t *testing.T) {
+	ctx := context.Background()
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "exact.txt"), []byte("12345"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(root, "large.txt"), []byte("123456"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	reader, err := NewRestrictedCompositeReaderWithLimit(root, 5)
+	if err != nil {
+		t.Fatalf("expected restricted reader construction, got %v", err)
+	}
+
+	art, err := reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "exact.txt"})
+	if err != nil {
+		t.Fatalf("expected file at limit to succeed, got %v", err)
+	}
+	if string(art.Body) != "12345" {
+		t.Fatalf("unexpected artifact body: %q", string(art.Body))
+	}
+
+	_, err = reader.Read(ctx, domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "large.txt"})
+	if !errors.Is(err, ErrFileTooLarge) {
+		t.Fatalf("expected ErrFileTooLarge, got %v", err)
+	}
+}
+
+func TestRestrictedCompositeReaderFileSizeLimitZeroDisablesLimit(t *testing.T) {
+	root := t.TempDir()
+	if err := os.WriteFile(filepath.Join(root, "large.txt"), []byte("123456"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+
+	reader, err := NewRestrictedCompositeReaderWithLimit(root, 0)
+	if err != nil {
+		t.Fatalf("expected restricted reader construction, got %v", err)
+	}
+	art, err := reader.Read(context.Background(), domain.ArtifactRef{Type: domain.ArtifactRefFile, URI: "large.txt"})
+	if err != nil {
+		t.Fatalf("expected unlimited reader to succeed, got %v", err)
+	}
+	if string(art.Body) != "123456" {
+		t.Fatalf("unexpected artifact body: %q", string(art.Body))
+	}
+}
+
 func TestFileReader_Read(t *testing.T) {
 	content := []byte("test file content")
 	tmpFile, err := os.CreateTemp("", "artifact_test_*.txt")

internal/config/config.go

@@ -41,6 +41,10 @@ type Config struct {
 
 type ServerConfig struct {
 	Addr             string `yaml:"addr"`
+	ArtifactRoot     string `yaml:"artifact_root"`
+	MaxRequestBytes  *int64 `yaml:"max_request_bytes"`
+	MaxArtifactBytes *int64 `yaml:"max_artifact_bytes"`
+	MaxResponseBytes *int64 `yaml:"max_response_bytes"`
 }
 
 type DefaultsConfig struct {
@@ -53,6 +57,10 @@ type AppSettings struct {
 	ProfileDir          string
 	SchemaDir           string
 	ServerAddr          string
+	ArtifactRoot        string
+	MaxRequestBytes     int64
+	MaxArtifactBytes    int64
+	MaxResponseBytes    int64
 	DefaultRenderFormat renderformat.PreparedRunOutputFormat
 }
 
@@ -62,6 +70,10 @@ type CLIOverrides struct {
 	ProfileDir       string
 	SchemaDir        string
 	ServerAddr       string
+	ArtifactRoot     string
+	MaxRequestBytes  *int64
+	MaxArtifactBytes *int64
+	MaxResponseBytes *int64
 	RenderFormat     string
 }
 
@@ -70,6 +82,9 @@ func BuiltInDefaults() AppSettings {
 	return AppSettings{
 		SchemaDir:           defaults.SchemaDirDefault,
 		ServerAddr:          defaults.HTTPAddrDefault,
+		MaxRequestBytes:     defaults.HTTPMaxRequestBytesDefault,
+		MaxArtifactBytes:    defaults.HTTPMaxArtifactBytesDefault,
+		MaxResponseBytes:    defaults.HTTPMaxResponseBytesDefault,
 		DefaultRenderFormat: renderformat.DefaultPreparedRunOutputFormat,
 	}
 }
@@ -142,6 +157,27 @@ func ApplyCLIOverrides(base AppSettings, overrides CLIOverrides) (AppSettings, e
 	if v := strings.TrimSpace(overrides.ServerAddr); v != "" {
 		out.ServerAddr = v
 	}
+	if v := strings.TrimSpace(overrides.ArtifactRoot); v != "" {
+		out.ArtifactRoot = filepath.Clean(v)
+	}
+	if overrides.MaxRequestBytes != nil {
+		if *overrides.MaxRequestBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_request_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxRequestBytes = *overrides.MaxRequestBytes
+	}
+	if overrides.MaxArtifactBytes != nil {
+		if *overrides.MaxArtifactBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_artifact_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxArtifactBytes = *overrides.MaxArtifactBytes
+	}
+	if overrides.MaxResponseBytes != nil {
+		if *overrides.MaxResponseBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_response_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxResponseBytes = *overrides.MaxResponseBytes
+	}
 	if rawFormat := strings.TrimSpace(overrides.RenderFormat); rawFormat != "" {
 		parsed, err := renderformat.ParsePreparedRunOutputFormat(rawFormat)
 		if err != nil {
@@ -181,6 +217,27 @@ func applyConfig(base AppSettings, cfg Config) (AppSettings, error) {
 	if v := strings.TrimSpace(cfg.Server.Addr); v != "" {
 		out.ServerAddr = v
 	}
+	if v := strings.TrimSpace(cfg.Server.ArtifactRoot); v != "" {
+		out.ArtifactRoot = filepath.Clean(v)
+	}
+	if cfg.Server.MaxRequestBytes != nil {
+		if *cfg.Server.MaxRequestBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_request_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxRequestBytes = *cfg.Server.MaxRequestBytes
+	}
+	if cfg.Server.MaxArtifactBytes != nil {
+		if *cfg.Server.MaxArtifactBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_artifact_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxArtifactBytes = *cfg.Server.MaxArtifactBytes
+	}
+	if cfg.Server.MaxResponseBytes != nil {
+		if *cfg.Server.MaxResponseBytes < 0 {
+			return AppSettings{}, fmt.Errorf("%w: server.max_response_bytes must be greater than or equal to 0", ErrInvalidConfig)
+		}
+		out.MaxResponseBytes = *cfg.Server.MaxResponseBytes
+	}
 	if rawFormat := strings.TrimSpace(cfg.Defaults.RenderFormat); rawFormat != "" {
 		parsed, err := renderformat.ParsePreparedRunOutputFormat(rawFormat)
 		if err != nil {

internal/config/config_test.go

@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	renderformat "gitea.maximumdirect.net/eric/scriptorium/internal/format"
 )
 
@@ -24,6 +25,20 @@ func TestLoadConfigMissingImplicitPathUsesBuiltInDefaults(t *testing.T) {
 	}
 }
 
+func TestBuiltInDefaultsIncludeHTTPSizeLimits(t *testing.T) {
+	got := BuiltInDefaults()
+
+	if got.MaxRequestBytes != defaults.HTTPMaxRequestBytesDefault {
+		t.Fatalf("unexpected max request bytes: %d", got.MaxRequestBytes)
+	}
+	if got.MaxArtifactBytes != defaults.HTTPMaxArtifactBytesDefault {
+		t.Fatalf("unexpected max artifact bytes: %d", got.MaxArtifactBytes)
+	}
+	if got.MaxResponseBytes != defaults.HTTPMaxResponseBytesDefault {
+		t.Fatalf("unexpected max response bytes: %d", got.MaxResponseBytes)
+	}
+}
+
 func TestLoadConfigMissingExplicitPathReturnsError(t *testing.T) {
 	tmp := t.TempDir()
 	missing := filepath.Join(tmp, "missing.yml")
@@ -92,6 +107,10 @@ profile_dir: ./profiles
 schema_dir: ./schemas
 server:
   addr: 127.0.0.1:9090
+  artifact_root: ./artifacts
+  max_request_bytes: 1024
+  max_artifact_bytes: 2048
+  max_response_bytes: 4096
 defaults:
   render_format: json
 `)
@@ -113,11 +132,61 @@ defaults:
 	if got.ServerAddr != "127.0.0.1:9090" {
 		t.Fatalf("unexpected server.addr: %q", got.ServerAddr)
 	}
+	if got.ArtifactRoot != filepath.Clean("./artifacts") {
+		t.Fatalf("unexpected server.artifact_root: %q", got.ArtifactRoot)
+	}
+	if got.MaxRequestBytes != 1024 {
+		t.Fatalf("unexpected server.max_request_bytes: %d", got.MaxRequestBytes)
+	}
+	if got.MaxArtifactBytes != 2048 {
+		t.Fatalf("unexpected server.max_artifact_bytes: %d", got.MaxArtifactBytes)
+	}
+	if got.MaxResponseBytes != 4096 {
+		t.Fatalf("unexpected server.max_response_bytes: %d", got.MaxResponseBytes)
+	}
 	if got.DefaultRenderFormat != renderformat.PreparedRunFormatJSON {
 		t.Fatalf("unexpected defaults.render_format: %q", got.DefaultRenderFormat)
 	}
 }
 
+func TestLoadConfigAcceptsZeroHTTPSizeLimits(t *testing.T) {
+	path := writeConfigFile(t, "config.yml", `
+server:
+  max_request_bytes: 0
+  max_artifact_bytes: 0
+  max_response_bytes: 0
+`)
+
+	got, err := LoadConfig(path, true)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if got.MaxRequestBytes != 0 || got.MaxArtifactBytes != 0 || got.MaxResponseBytes != 0 {
+		t.Fatalf("expected zero limits to be preserved, got request=%d artifact=%d response=%d", got.MaxRequestBytes, got.MaxArtifactBytes, got.MaxResponseBytes)
+	}
+}
+
+func TestLoadConfigRejectsNegativeHTTPSizeLimits(t *testing.T) {
+	tests := []struct {
+		name string
+		body string
+	}{
+		{name: "request", body: "server:\n  max_request_bytes: -1\n"},
+		{name: "artifact", body: "server:\n  max_artifact_bytes: -1\n"},
+		{name: "response", body: "server:\n  max_response_bytes: -1\n"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			path := writeConfigFile(t, "config.yml", tc.body)
+			_, err := LoadConfig(path, true)
+			if !errors.Is(err, ErrInvalidConfig) {
+				t.Fatalf("expected ErrInvalidConfig, got %v", err)
+			}
+		})
+	}
+}
+
 func TestLoadConfigEmptyFileResolvesToBuiltInDefaults(t *testing.T) {
 	path := writeConfigFile(t, "config.yml", "")
 
@@ -185,14 +254,25 @@ func TestApplyCLIOverridesAppliesPrecedence(t *testing.T) {
 		ProfileDir:          "/from/config/profiles",
 		SchemaDir:           "/from/config/schemas",
 		ServerAddr:          ":1234",
+		ArtifactRoot:        "/from/config/artifacts",
+		MaxRequestBytes:     111,
+		MaxArtifactBytes:    222,
+		MaxResponseBytes:    333,
 		DefaultRenderFormat: renderformat.PreparedRunFormatJSON,
 	}
+	maxRequestBytes := int64(0)
+	maxArtifactBytes := int64(444)
+	maxResponseBytes := int64(555)
 
 	got, err := ApplyCLIOverrides(base, CLIOverrides{
 		PromptDir:        "./prompts-cli",
 		ProfileDir:       "./profiles-cli",
 		SchemaDir:        "./schemas-cli",
 		ServerAddr:       ":8081",
+		ArtifactRoot:     "./artifacts-cli",
+		MaxRequestBytes:  &maxRequestBytes,
+		MaxArtifactBytes: &maxArtifactBytes,
+		MaxResponseBytes: &maxResponseBytes,
 		RenderFormat:     "text",
 	})
 	if err != nil {
@@ -211,11 +291,45 @@ func TestApplyCLIOverridesAppliesPrecedence(t *testing.T) {
 	if got.ServerAddr != ":8081" {
 		t.Fatalf("unexpected server addr: %q", got.ServerAddr)
 	}
+	if got.ArtifactRoot != filepath.Clean("./artifacts-cli") {
+		t.Fatalf("unexpected artifact root: %q", got.ArtifactRoot)
+	}
+	if got.MaxRequestBytes != 0 {
+		t.Fatalf("unexpected max request bytes: %d", got.MaxRequestBytes)
+	}
+	if got.MaxArtifactBytes != 444 {
+		t.Fatalf("unexpected max artifact bytes: %d", got.MaxArtifactBytes)
+	}
+	if got.MaxResponseBytes != 555 {
+		t.Fatalf("unexpected max response bytes: %d", got.MaxResponseBytes)
+	}
 	if got.DefaultRenderFormat != renderformat.PreparedRunFormatText {
 		t.Fatalf("unexpected render format: %q", got.DefaultRenderFormat)
 	}
 }
 
+func TestApplyCLIOverridesRejectsNegativeHTTPSizeLimits(t *testing.T) {
+	negative := int64(-1)
+
+	tests := []struct {
+		name      string
+		overrides CLIOverrides
+	}{
+		{name: "request", overrides: CLIOverrides{MaxRequestBytes: &negative}},
+		{name: "artifact", overrides: CLIOverrides{MaxArtifactBytes: &negative}},
+		{name: "response", overrides: CLIOverrides{MaxResponseBytes: &negative}},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := ApplyCLIOverrides(BuiltInDefaults(), tc.overrides)
+			if !errors.Is(err, ErrInvalidConfig) {
+				t.Fatalf("expected ErrInvalidConfig, got %v", err)
+			}
+		})
+	}
+}
+
 func TestApplyCLIOverridesInvalidRenderFormatReturnsError(t *testing.T) {
 	_, err := ApplyCLIOverrides(BuiltInDefaults(), CLIOverrides{RenderFormat: "yaml"})
 	if err == nil {

internal/defaults/defaults.go

@@ -14,6 +14,9 @@ const (
 	ContentTypeTextMarkdown     = "text/markdown"
 	ContentTypeApplicationJSON  = "application/json"
 	OpenAIChatCompletionsPath   = "/chat/completions"
+	HTTPMaxRequestBytesDefault  = 16 * 1024 * 1024
+	HTTPMaxArtifactBytesDefault = 16 * 1024 * 1024
+	HTTPMaxResponseBytesDefault = 16 * 1024 * 1024
 
 	ExecutionDefaultTemperature    = 0.0
 	ExecutionDefaultMaxTokens      = 0

internal/domain/domain.go

@@ -40,14 +40,33 @@ const (
 	ValidationSkipped ValidationStatus = "skipped"
 )
 
+// CacheControlType defines provider cache behavior for prompt content.
+type CacheControlType string
+
+const (
+	CacheControlEphemeral CacheControlType = "ephemeral"
+)
+
+const (
+	// SessionIDMaxLength is OpenRouter's documented maximum session_id length.
+	SessionIDMaxLength = 256
+)
+
+// CacheControl describes provider cache metadata attached to prompt content.
+type CacheControl struct {
+	Type CacheControlType `yaml:"type" json:"type"`
+	TTL  string           `yaml:"ttl,omitempty" json:"ttl,omitempty"`
+}
+
 // RunRequest represents a request to generate a single artifact.
 type RunRequest struct {
 	PromptID      string
 	PromptVersion string
 	ProfileID     string
+	APIKey        string `json:"-" yaml:"-"`
 	Inputs        map[string]ArtifactRef
 	Vars          map[string]string
-	Execution     *ExecutionTarget
+	Execution     *ExecutionTargetOverride
 	Validation    *OutputContract
 	Metadata      map[string]string
 }
@@ -71,7 +90,6 @@ type RunResult struct {
 	StartTime            time.Time
 	EndTime              time.Time
 	Duration             time.Duration
-	Error                error
 }
 
 // PreparedRun contains pre-LLM execution state from the prepare/render phase.
@@ -82,9 +100,11 @@ type PreparedRun struct {
 	PromptHash           string                  `json:"prompt_hash,omitempty"`
 	SelectedProfileID    string                  `json:"selected_profile_id"`
 	EffectiveModelParams ExecutionTarget         `json:"effective_model_params"`
+	TargetPresence       ExecutionTargetPresence `json:"-"`
 	OutputContract       OutputContract          `json:"output_contract"`
 	StructuredOutput     *StructuredOutputSpec   `json:"structured_output,omitempty"`
 	InputHashes          map[string]string       `json:"input_hashes,omitempty"`
+	SessionID            string                  `json:"session_id,omitempty"`
 	RenderedPromptHash   string                  `json:"rendered_prompt_hash"`
 	Messages             []RenderedMessage       `json:"messages"`
 	StartTime            time.Time               `json:"start_time,omitempty"`
@@ -115,6 +135,7 @@ type PromptDefinition struct {
 	Version        string                  `yaml:"version"`
 	DefaultProfile string                  `yaml:"default_profile"`
 	Description    string                  `yaml:"description"`
+	SessionID      string                  `yaml:"session_id" json:"session_id,omitempty"`
 	Inputs         []PromptInput           `yaml:"inputs"`
 	Templates      []PromptMessageTemplate `yaml:"templates"`
 	OutputFormat   OutputFormat            `yaml:"output_format"`
@@ -134,6 +155,7 @@ type PromptMessageTemplate struct {
 	Role         string        `yaml:"role"`
 	Content      string        `yaml:"content"`
 	ContentFile  string        `yaml:"content_file"`
+	CacheControl *CacheControl `yaml:"cache_control,omitempty" json:"cache_control,omitempty"`
 }
 
 // ExecutionProfile describes how and where to execute a model.
@@ -148,7 +170,31 @@ type ExecutionProfile struct {
 	ServiceTier     string         `yaml:"service_tier"`
 	ReasoningEffort string         `yaml:"reasoning_effort"`
 	APIKeyEnv       string         `yaml:"api_key_env"`
-	ExtraParams     map[string]string `yaml:"extra_params"`
+	APIKeyRequired  bool           `yaml:"-" json:"-"`
+	ExtraParams     map[string]any `yaml:"extra_params"`
+}
+
+// ExecutionTargetOverride represents per-request runtime setting overrides.
+type ExecutionTargetOverride struct {
+	Endpoint        string         `json:"endpoint,omitempty"`
+	Model           string         `json:"model,omitempty"`
+	Temperature     *float64       `json:"temperature,omitempty"`
+	MaxTokens       *int           `json:"max_tokens,omitempty"`
+	TopP            *float64       `json:"top_p,omitempty"`
+	TimeoutSeconds  *int           `json:"timeout_seconds,omitempty"`
+	ServiceTier     string         `json:"service_tier,omitempty"`
+	ReasoningEffort string         `json:"reasoning_effort,omitempty"`
+	APIKeyEnv       string         `json:"api_key_env,omitempty"`
+	ExtraParams     map[string]any `json:"extra_params,omitempty"`
+}
+
+// ExecutionTargetPresence tracks which effective runtime fields came from an
+// explicit request override even when the resolved value is a zero value.
+type ExecutionTargetPresence struct {
+	Temperature    bool
+	MaxTokens      bool
+	TopP           bool
+	TimeoutSeconds bool
 }
 
 // ExecutionTarget represents effective model runtime settings for a run.
@@ -162,7 +208,9 @@ type ExecutionTarget struct {
 	ServiceTier     string         `yaml:"service_tier" json:"service_tier"`
 	ReasoningEffort string         `yaml:"reasoning_effort" json:"reasoning_effort"`
 	APIKeyEnv       string         `yaml:"api_key_env" json:"api_key_env"`
-	ExtraParams     map[string]string `yaml:"extra_params" json:"extra_params"`
+	APIKey          string         `yaml:"-" json:"-"`
+	APIKeyRequired  bool           `yaml:"-" json:"-"`
+	ExtraParams     map[string]any `yaml:"extra_params" json:"extra_params"`
 }
 
 // OutputContract defines the requirements for the output artifact.
@@ -175,6 +223,7 @@ type OutputContract struct {
 
 // RenderedPrompt represents the prompt after template application.
 type RenderedPrompt struct {
+	SessionID string            `json:"session_id,omitempty"`
 	Messages  []RenderedMessage `json:"messages"`
 }
 
@@ -182,12 +231,14 @@ type RenderedPrompt struct {
 type RenderedMessage struct {
 	Role         string        `json:"role"`
 	Content      string        `json:"content"`
+	CacheControl *CacheControl `json:"cache_control,omitempty"`
 }
 
 // GenerateRequest is the internal request passed to the LLM client.
 type GenerateRequest struct {
 	Prompt           RenderedPrompt
 	Target           ExecutionTarget
+	TargetPresence   ExecutionTargetPresence
 	StructuredOutput *StructuredOutputSpec
 }
 
@@ -222,6 +273,8 @@ type TokenUsage struct {
 	PromptTokens     int
 	CompletionTokens int
 	TotalTokens      int
+	CachedTokens     int
+	CacheWriteTokens int
 }
 
 // ValidationResult represents the outcome of an output validation.
@@ -233,23 +286,3 @@ type ValidationResult struct {
 	RepairAttempts int
 	IsValid        bool
 }
-
-// RunMetadata contains auditing information for a run.
-type RunMetadata struct {
-	RunID              string
-	PromptID           string
-	PromptVersion      string
-	PromptHash         string
-	RenderedPromptHash string
-	SelectedProfileID  string
-	InputHashes        map[string]string
-	ModelEndpoint      string
-	ModelName          string
-	Params             ExecutionTarget
-	Timestamp          time.Time
-	Duration           time.Duration
-	Usage              TokenUsage
-	ValidationMode     ValidationMode
-	ValidationStatus   ValidationStatus
-	RepairAttempts     int
-}

internal/domain/prepared_run_test.go

@@ -20,6 +20,7 @@ func TestPreparedRunJSONDoesNotIncludeSecretValues(t *testing.T) {
 			Endpoint:  "http://llm/v1",
 			Model:     "gpt-test",
 			APIKeyEnv: envName,
+			APIKey:    secret,
 		},
 		InputHashes:        map[string]string{"transcript": "hash-1"},
 		RenderedPromptHash: "rendered-hash",
@@ -53,3 +54,88 @@ func TestPreparedRunJSONDoesNotIncludeSecretValues(t *testing.T) {
 		}
 	}
 }
+
+func TestPreparedRunJSONIncludesMessageCacheControlOnlyWhenPresent(t *testing.T) {
+	prepared := PreparedRun{
+		PromptID:          "prompt.id",
+		SelectedProfileID: "local-fast",
+		EffectiveModelParams: ExecutionTarget{
+			Endpoint: "http://llm/v1",
+			Model:    "gpt-test",
+		},
+		RenderedPromptHash: "rendered-hash",
+		Messages: []RenderedMessage{
+			{
+				Role:    "system",
+				Content: "You are helpful.",
+				CacheControl: &CacheControl{
+					Type: CacheControlEphemeral,
+					TTL:  "1h",
+				},
+			},
+			{Role: "user", Content: "Summarize this."},
+		},
+	}
+
+	b, err := json.Marshal(prepared)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+
+	var decoded struct {
+		Messages []map[string]any `json:"messages"`
+	}
+	if err := json.Unmarshal(b, &decoded); err != nil {
+		t.Fatalf("unmarshal failed: %v", err)
+	}
+	if len(decoded.Messages) != 2 {
+		t.Fatalf("expected 2 messages, got %d", len(decoded.Messages))
+	}
+
+	cacheControl, ok := decoded.Messages[0]["cache_control"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected cache_control on first message, got %#v", decoded.Messages[0])
+	}
+	if cacheControl["type"] != string(CacheControlEphemeral) || cacheControl["ttl"] != "1h" {
+		t.Fatalf("unexpected cache_control payload: %#v", cacheControl)
+	}
+	if _, ok := decoded.Messages[1]["cache_control"]; ok {
+		t.Fatalf("expected second message to omit cache_control, got %#v", decoded.Messages[1])
+	}
+}
+
+func TestPreparedRunJSONIncludesSessionIDOnlyWhenPresent(t *testing.T) {
+	prepared := PreparedRun{
+		PromptID:          "prompt.id",
+		SelectedProfileID: "local-fast",
+		EffectiveModelParams: ExecutionTarget{
+			Endpoint: "http://llm/v1",
+			Model:    "gpt-test",
+		},
+		SessionID:          "session-123",
+		RenderedPromptHash: "rendered-hash",
+		Messages:           []RenderedMessage{{Role: "user", Content: "Summarize this."}},
+	}
+
+	b, err := json.Marshal(prepared)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+
+	var decoded map[string]any
+	if err := json.Unmarshal(b, &decoded); err != nil {
+		t.Fatalf("unmarshal failed: %v", err)
+	}
+	if decoded["session_id"] != "session-123" {
+		t.Fatalf("expected session_id in prepared run JSON, got %#v", decoded["session_id"])
+	}
+
+	prepared.SessionID = ""
+	b, err = json.Marshal(prepared)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+	if strings.Contains(string(b), "session_id") {
+		t.Fatalf("expected empty session_id to be omitted, got %s", b)
+	}
+}

internal/filecatalog/catalog.go

@@ -2,7 +2,10 @@ package filecatalog
 
 import (
 	"context"
+	"fmt"
+	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -23,7 +26,7 @@ func FindYAMLFiles(ctx context.Context, root string) ([]string, error) {
 		if d.IsDir() {
 			return nil
 		}
-		if !isYAMLFile(d.Name()) {
+		if !IsYAMLFile(d.Name()) {
 			return nil
 		}
 		files = append(files, path)
@@ -33,15 +36,100 @@ func FindYAMLFiles(ctx context.Context, root string) ([]string, error) {
 	return files, err
 }
 
-// RelativePath computes a clean relative path from root to path.
+// FindFSYAMLFiles returns sorted paths for .yaml and .yml files under root in fsys.
-func RelativePath(root string, path string) string {
+func FindFSYAMLFiles(ctx context.Context, fsys fs.FS, root string) ([]string, error) {
-	rel, err := filepath.Rel(root, path)
+	cleanRoot := CleanFSRoot(root)
+	var files []string
+	err := fs.WalkDir(fsys, cleanRoot, func(name string, d fs.DirEntry, err error) error {
 		if err != nil {
-		return filepath.Clean(path)
+			return err
+		}
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+		if d.IsDir() {
+			return nil
+		}
+		if !IsYAMLFile(d.Name()) {
+			return nil
+		}
+		files = append(files, name)
+		return nil
+	})
+	sort.Strings(files)
+	return files, err
+}
+
+// RelativePath computes a clean relative path from root to path.
+func RelativePath(root string, filePath string) string {
+	rel, err := filepath.Rel(root, filePath)
+	if err != nil {
+		return filepath.Clean(filePath)
 	}
 	return filepath.Clean(rel)
 }
 
+// CleanFSRoot normalizes a root path for use with fs.FS.
+func CleanFSRoot(root string) string {
+	root = strings.TrimSpace(root)
+	if root == "" || root == "." {
+		return "."
+	}
+	return path.Clean(root)
+}
+
+// DisplayPath returns name relative to root for messages about fs.FS paths.
+func DisplayPath(root string, name string) string {
+	cleanRoot := CleanFSRoot(root)
+	cleanName := path.Clean(name)
+	if cleanRoot == "." {
+		return cleanName
+	}
+	prefix := strings.TrimSuffix(cleanRoot, "/") + "/"
+	if strings.HasPrefix(cleanName, prefix) {
+		return strings.TrimPrefix(cleanName, prefix)
+	}
+	return cleanName
+}
+
+// ResolveFSPath resolves userPath from baseDir and keeps it inside root.
+func ResolveFSPath(root string, baseDir string, userPath string) (string, string, error) {
+	cleanRoot := CleanFSRoot(root)
+	cleanBase := path.Clean(strings.TrimSpace(baseDir))
+	if cleanBase == "" {
+		cleanBase = cleanRoot
+	}
+	if !containsFSPath(cleanRoot, cleanBase) {
+		return "", "", fmt.Errorf("base path %q is outside source root %q", cleanBase, cleanRoot)
+	}
+
+	cleanUserPath := strings.TrimSpace(userPath)
+	if cleanUserPath == "" {
+		return "", "", fmt.Errorf("path is required")
+	}
+	cleanUserPath = path.Clean(cleanUserPath)
+	if path.IsAbs(cleanUserPath) {
+		return "", "", fmt.Errorf("path %q must be relative", userPath)
+	}
+
+	resolved := path.Clean(path.Join(cleanBase, cleanUserPath))
+	if !containsFSPath(cleanRoot, resolved) {
+		return "", "", fmt.Errorf("path %q escapes source root %q", userPath, cleanRoot)
+	}
+	return resolved, DisplayPath(cleanRoot, resolved), nil
+}
+
+func containsFSPath(root string, name string) bool {
+	root = CleanFSRoot(root)
+	name = path.Clean(name)
+	if root == "." {
+		return name == "." || (name != ".." && !strings.HasPrefix(name, "../"))
+	}
+	return name == root || strings.HasPrefix(name, strings.TrimSuffix(root, "/")+"/")
+}
+
 // Stem strips .yaml or .yml from a file name.
 func Stem(name string) string {
 	name = strings.TrimSuffix(name, ".yaml")
@@ -49,6 +137,6 @@ func Stem(name string) string {
 	return name
 }
 
-func isYAMLFile(name string) bool {
+func IsYAMLFile(name string) bool {
 	return strings.HasSuffix(name, ".yaml") || strings.HasSuffix(name, ".yml")
 }

internal/filecatalog/catalog_test.go

@@ -6,7 +6,9 @@ import (
 	"os"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"testing"
+	"testing/fstest"
 )
 
 func TestFindYAMLFilesNestedSortedAndFiltered(t *testing.T) {
@@ -43,6 +45,42 @@ func TestFindYAMLFilesHonorsContextCancellation(t *testing.T) {
 	}
 }
 
+func TestFindFSYAMLFilesNestedSortedAndFiltered(t *testing.T) {
+	fsys := fstest.MapFS{
+		"prompts/z/prompt.yml":      &fstest.MapFile{Data: []byte("id: z")},
+		"prompts/a/profile.yaml":    &fstest.MapFile{Data: []byte("id: a")},
+		"prompts/a/ignore.txt":      &fstest.MapFile{Data: []byte("not yaml")},
+		"prompts/b/ignore.yaml.bak": &fstest.MapFile{Data: []byte("not yaml")},
+		"other/ignored.yaml":        &fstest.MapFile{Data: []byte("id: ignored")},
+	}
+
+	got, err := FindFSYAMLFiles(context.Background(), fsys, " prompts ")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	want := []string{
+		"prompts/a/profile.yaml",
+		"prompts/z/prompt.yml",
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("expected sorted YAML files %v, got %v", want, got)
+	}
+}
+
+func TestFindFSYAMLFilesHonorsContextCancellation(t *testing.T) {
+	fsys := fstest.MapFS{
+		"one.yaml": &fstest.MapFile{Data: []byte("id: one")},
+	}
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	_, err := FindFSYAMLFiles(ctx, fsys, ".")
+	if !errors.Is(err, context.Canceled) {
+		t.Fatalf("expected context.Canceled, got %v", err)
+	}
+}
+
 func TestRelativePathNested(t *testing.T) {
 	root := t.TempDir()
 	path := filepath.Join(root, "nested", "profiles", "local.yaml")
@@ -53,6 +91,133 @@ func TestRelativePathNested(t *testing.T) {
 	}
 }
 
+func TestCleanFSRoot(t *testing.T) {
+	tests := []struct {
+		name string
+		root string
+		want string
+	}{
+		{name: "empty", root: "", want: "."},
+		{name: "dot", root: ".", want: "."},
+		{name: "trimmed", root: " prompts/../profiles ", want: "profiles"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := CleanFSRoot(tc.root); got != tc.want {
+				t.Fatalf("expected %q, got %q", tc.want, got)
+			}
+		})
+	}
+}
+
+func TestDisplayPath(t *testing.T) {
+	tests := []struct {
+		name string
+		root string
+		path string
+		want string
+	}{
+		{name: "root dot", root: ".", path: "profiles/local.yaml", want: "profiles/local.yaml"},
+		{name: "nested root", root: "profiles", path: "profiles/local.yaml", want: "local.yaml"},
+		{name: "outside root", root: "profiles", path: "other/local.yaml", want: "other/local.yaml"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := DisplayPath(tc.root, tc.path); got != tc.want {
+				t.Fatalf("expected %q, got %q", tc.want, got)
+			}
+		})
+	}
+}
+
+func TestResolveFSPath(t *testing.T) {
+	tests := []struct {
+		name        string
+		root        string
+		baseDir     string
+		userPath    string
+		wantPath    string
+		wantDisplay string
+		wantErr     string
+	}{
+		{
+			name:        "sibling inside root",
+			root:        "prompts",
+			baseDir:     "prompts/nested",
+			userPath:    "./messages/user.tmpl",
+			wantPath:    "prompts/nested/messages/user.tmpl",
+			wantDisplay: "nested/messages/user.tmpl",
+		},
+		{
+			name:        "parent inside root",
+			root:        "prompts",
+			baseDir:     "prompts/nested",
+			userPath:    "../shared/user.tmpl",
+			wantPath:    "prompts/shared/user.tmpl",
+			wantDisplay: "shared/user.tmpl",
+		},
+		{
+			name:     "escape rejected",
+			root:     "prompts",
+			baseDir:  "prompts/nested",
+			userPath: "../../outside.tmpl",
+			wantErr:  "escapes source root",
+		},
+		{
+			name:     "absolute path rejected",
+			root:     "prompts",
+			baseDir:  "prompts/nested",
+			userPath: "/outside.tmpl",
+			wantErr:  "must be relative",
+		},
+		{
+			name:     "empty path rejected",
+			root:     "prompts",
+			baseDir:  "prompts/nested",
+			userPath: " ",
+			wantErr:  "path is required",
+		},
+		{
+			name:        "dot root allows normal relative path",
+			root:        ".",
+			baseDir:     ".",
+			userPath:    "schemas/events.schema.json",
+			wantPath:    "schemas/events.schema.json",
+			wantDisplay: "schemas/events.schema.json",
+		},
+		{
+			name:     "dot root rejects parent escape",
+			root:     ".",
+			baseDir:  ".",
+			userPath: "../outside.tmpl",
+			wantErr:  "escapes source root",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			gotPath, gotDisplay, err := ResolveFSPath(tc.root, tc.baseDir, tc.userPath)
+			if tc.wantErr != "" {
+				if err == nil {
+					t.Fatalf("expected error containing %q", tc.wantErr)
+				}
+				if !strings.Contains(err.Error(), tc.wantErr) {
+					t.Fatalf("expected error to contain %q, got %v", tc.wantErr, err)
+				}
+				return
+			}
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+			if gotPath != tc.wantPath || gotDisplay != tc.wantDisplay {
+				t.Fatalf("expected path/display %q/%q, got %q/%q", tc.wantPath, tc.wantDisplay, gotPath, gotDisplay)
+			}
+		})
+	}
+}
+
 func TestStemStripsYAMLExtensions(t *testing.T) {
 	tests := []struct {
 		name string
@@ -73,6 +238,27 @@ func TestStemStripsYAMLExtensions(t *testing.T) {
 	}
 }
 
+func TestIsYAMLFile(t *testing.T) {
+	tests := []struct {
+		name string
+		in   string
+		want bool
+	}{
+		{name: "yaml", in: "prompt.yaml", want: true},
+		{name: "yml", in: "profile.yml", want: true},
+		{name: "backup", in: "profile.yaml.bak", want: false},
+		{name: "uppercase", in: "profile.YAML", want: false},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := IsYAMLFile(tc.in); got != tc.want {
+				t.Fatalf("expected %v, got %v", tc.want, got)
+			}
+		})
+	}
+}
+
 func mustWriteFile(t *testing.T, path string, content string) {
 	t.Helper()
 	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {

internal/format/prepared_run.go

@@ -96,6 +96,9 @@ func (textPreparedRunFormatter) Format(prepared *domain.PreparedRun) ([]byte, er
 	if prepared.PromptHash != "" {
 		fmt.Fprintf(&b, "prompt_hash: %s\n", prepared.PromptHash)
 	}
+	if prepared.SessionID != "" {
+		fmt.Fprintf(&b, "session_id: %s\n", prepared.SessionID)
+	}
 	fmt.Fprintf(&b, "rendered_prompt_hash: %s\n", prepared.RenderedPromptHash)
 
 	target := prepared.EffectiveModelParams
@@ -123,7 +126,11 @@ func (textPreparedRunFormatter) Format(prepared *domain.PreparedRun) ([]byte, er
 		}
 		sort.Strings(keys)
 		for _, k := range keys {
-			fmt.Fprintf(&b, "    %s: %s\n", k, target.ExtraParams[k])
+			renderedValue, err := formatExtraParamTextValue(target.ExtraParams[k])
+			if err != nil {
+				return nil, fmt.Errorf("failed to format extra_params.%s: %w", k, err)
+			}
+			fmt.Fprintf(&b, "    %s: %s\n", k, renderedValue)
 		}
 	}
 
@@ -151,6 +158,13 @@ func (textPreparedRunFormatter) Format(prepared *domain.PreparedRun) ([]byte, er
 		messages := byRole[role]
 		for i, msg := range messages {
 			fmt.Fprintf(&b, "    - message: %d\n", i+1)
+			if msg.CacheControl != nil {
+				fmt.Fprintf(&b, "      cache_control: %s", msg.CacheControl.Type)
+				if msg.CacheControl.TTL != "" {
+					fmt.Fprintf(&b, " ttl=%s", msg.CacheControl.TTL)
+				}
+				fmt.Fprintln(&b)
+			}
 			fmt.Fprintln(&b, "      content: |")
 			content := msg.Content
 			if content == "" {
@@ -165,3 +179,15 @@ func (textPreparedRunFormatter) Format(prepared *domain.PreparedRun) ([]byte, er
 
 	return b.Bytes(), nil
 }
+
+func formatExtraParamTextValue(value any) (string, error) {
+	if s, ok := value.(string); ok {
+		return s, nil
+	}
+
+	b, err := json.Marshal(value)
+	if err != nil {
+		return "", err
+	}
+	return string(b), nil
+}

internal/format/prepared_run_test.go

@@ -49,6 +49,36 @@ func TestTextFormatterIncludesPreparedRunDetails(t *testing.T) {
 	}
 }
 
+func TestTextFormatterRendersExtraParamsDeterministically(t *testing.T) {
+	prepared := samplePreparedRun()
+	prepared.EffectiveModelParams.ExtraParams = map[string]any{
+		"z_string": "enabled",
+		"b_number": 42,
+		"a_object": map[string]any{
+			"nested": "value",
+			"count":  2,
+		},
+		"c_array": []any{"first", 3, false},
+	}
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatText)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	s := string(out)
+
+	want := strings.Join([]string{
+		"  extra_params:",
+		"    a_object: {\"count\":2,\"nested\":\"value\"}",
+		"    b_number: 42",
+		"    c_array: [\"first\",3,false]",
+		"    z_string: enabled",
+	}, "\n")
+	if !strings.Contains(s, want) {
+		t.Fatalf("expected deterministic extra_params block %q, got:\n%s", want, s)
+	}
+}
+
 func TestTextFormatterDoesNotIncludeResolvedAPIKeyValue(t *testing.T) {
 	const secret = "super-secret-api-key"
 	t.Setenv("SCRIPTORIUM_API_KEY", secret)
@@ -62,8 +92,94 @@ func TestTextFormatterDoesNotIncludeResolvedAPIKeyValue(t *testing.T) {
 	}
 }
 
+func TestTextFormatterDoesNotIncludeDirectAPIKeyValue(t *testing.T) {
+	const directKey = "direct-format-key"
+	prepared := samplePreparedRun()
+	prepared.EffectiveModelParams.APIKey = directKey
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatText)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if strings.Contains(string(out), directKey) {
+		t.Fatalf("text output should not include direct api key value: %s", out)
+	}
+}
+
+func TestTextFormatterIncludesMessageCacheControlBeforeContent(t *testing.T) {
+	prepared := samplePreparedRun()
+	prepared.Messages = []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "System guidance.",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+				TTL:  "1h",
+			},
+		},
+		{Role: "user", Content: "Summarize the transcript."},
+	}
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatText)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	s := string(out)
+	if !strings.Contains(s, "  system:\n    - message: 1\n      cache_control: ephemeral ttl=1h\n      content: |") {
+		t.Fatalf("expected system message cache control before content, got:\n%s", s)
+	}
+	if strings.Count(s, "cache_control:") != 1 {
+		t.Fatalf("expected exactly one cache_control line, got:\n%s", s)
+	}
+}
+
+func TestTextFormatterIncludesSessionIDWhenPresent(t *testing.T) {
+	prepared := samplePreparedRun()
+	prepared.SessionID = "session-123"
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatText)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if !strings.Contains(string(out), "session_id: session-123\n") {
+		t.Fatalf("expected session_id in text output, got:\n%s", out)
+	}
+}
+
+func TestTextFormatterOmitsEmptyCacheControlTTL(t *testing.T) {
+	prepared := samplePreparedRun()
+	prepared.Messages = []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "System guidance.",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+			},
+		},
+	}
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatText)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	s := string(out)
+	if !strings.Contains(s, "      cache_control: ephemeral\n") {
+		t.Fatalf("expected cache_control line without ttl, got:\n%s", s)
+	}
+	if strings.Contains(s, "ttl=") {
+		t.Fatalf("expected empty ttl to be omitted, got:\n%s", s)
+	}
+}
+
 func TestJSONFormatterEmitsValidJSONAndIncludesPreparedRunFields(t *testing.T) {
 	prepared := samplePreparedRun()
+	prepared.SessionID = "session-123"
+	prepared.EffectiveModelParams.ExtraParams = map[string]any{
+		"number": 42,
+		"nested": map[string]any{
+			"enabled": true,
+		},
+	}
 
 	out, err := FormatPreparedRun(prepared, PreparedRunFormatJSON)
 	if err != nil {
@@ -87,9 +203,24 @@ func TestJSONFormatterEmitsValidJSONAndIncludesPreparedRunFields(t *testing.T) {
 	if decoded["rendered_prompt_hash"] != "rendered-hash" {
 		t.Fatalf("expected rendered_prompt_hash in json output, got %#v", decoded["rendered_prompt_hash"])
 	}
-	if _, ok := decoded["effective_model_params"]; !ok {
+	if decoded["session_id"] != "session-123" {
+		t.Fatalf("expected session_id in json output, got %#v", decoded["session_id"])
+	}
+	modelParams, ok := decoded["effective_model_params"].(map[string]any)
+	if !ok {
 		t.Fatalf("expected effective_model_params in json output, got %#v", decoded)
 	}
+	extraParams, ok := modelParams["extra_params"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected extra_params in json output, got %#v", modelParams["extra_params"])
+	}
+	if extraParams["number"] != float64(42) {
+		t.Fatalf("unexpected numeric extra param in json output: %#v", extraParams["number"])
+	}
+	nested, ok := extraParams["nested"].(map[string]any)
+	if !ok || nested["enabled"] != true {
+		t.Fatalf("unexpected nested extra param in json output: %#v", extraParams["nested"])
+	}
 	if _, ok := decoded["input_hashes"]; !ok {
 		t.Fatalf("expected input_hashes in json output, got %#v", decoded)
 	}
@@ -98,6 +229,47 @@ func TestJSONFormatterEmitsValidJSONAndIncludesPreparedRunFields(t *testing.T) {
 	}
 }
 
+func TestJSONFormatterIncludesMessageCacheControlOnlyWhenPresent(t *testing.T) {
+	prepared := samplePreparedRun()
+	prepared.Messages = []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "System guidance.",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+				TTL:  "1h",
+			},
+		},
+		{Role: "user", Content: "Summarize the transcript."},
+	}
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatJSON)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	var decoded struct {
+		Messages []map[string]any `json:"messages"`
+	}
+	if err := json.Unmarshal(out, &decoded); err != nil {
+		t.Fatalf("expected valid json output, got %v", err)
+	}
+	if len(decoded.Messages) != 2 {
+		t.Fatalf("expected 2 messages, got %d", len(decoded.Messages))
+	}
+
+	cacheControl, ok := decoded.Messages[0]["cache_control"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected first message cache_control, got %#v", decoded.Messages[0])
+	}
+	if cacheControl["type"] != string(domain.CacheControlEphemeral) || cacheControl["ttl"] != "1h" {
+		t.Fatalf("unexpected cache_control payload: %#v", cacheControl)
+	}
+	if _, ok := decoded.Messages[1]["cache_control"]; ok {
+		t.Fatalf("expected second message to omit cache_control, got %#v", decoded.Messages[1])
+	}
+}
+
 func TestJSONFormatterDoesNotIncludeResolvedAPIKeyValue(t *testing.T) {
 	const secret = "super-secret-api-key"
 	t.Setenv("SCRIPTORIUM_API_KEY", secret)
@@ -111,6 +283,20 @@ func TestJSONFormatterDoesNotIncludeResolvedAPIKeyValue(t *testing.T) {
 	}
 }
 
+func TestJSONFormatterDoesNotIncludeDirectAPIKeyValue(t *testing.T) {
+	const directKey = "direct-format-key"
+	prepared := samplePreparedRun()
+	prepared.EffectiveModelParams.APIKey = directKey
+
+	out, err := FormatPreparedRun(prepared, PreparedRunFormatJSON)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if strings.Contains(string(out), directKey) {
+		t.Fatalf("json output should not include direct api key value: %s", out)
+	}
+}
+
 func TestParsePreparedRunOutputFormatRecognizesSupportedNames(t *testing.T) {
 	tests := []struct {
 		name  string

internal/llm/openai_compatible_client.go

@@ -12,6 +12,7 @@ import (
 	"os"
 	"strings"
 	"time"
+	"unicode/utf8"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
@@ -54,10 +55,11 @@ func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) (*OpenAICompatibleCli
 
 	var client *http.Client
 	if cfg.HTTPClient != nil {
-		client = cfg.HTTPClient
+		cloned := *cfg.HTTPClient
-		if client.Timeout == 0 {
+		if cloned.Timeout == 0 {
-			client.Timeout = timeout
+			cloned.Timeout = timeout
 		}
+		client = &cloned
 	} else {
 		client = &http.Client{Timeout: timeout}
 	}
@@ -89,7 +91,12 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
 	}
 
-	payload, err := json.Marshal(wireReq)
+	wirePayload, err := openAIChatRequestPayload(wireReq)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
+	}
+
+	payload, err := json.Marshal(wirePayload)
 	if err != nil {
 		return nil, fmt.Errorf("%w: failed to encode request: %v", ErrRequestFailed, err)
 	}
@@ -99,7 +106,9 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 		return nil, fmt.Errorf("%w: failed to create request: %v", ErrRequestFailed, err)
 	}
 	httpReq.Header.Set("Content-Type", "application/json")
-	if envName := strings.TrimSpace(req.Target.APIKeyEnv); envName != "" {
+	if apiKey := strings.TrimSpace(req.Target.APIKey); apiKey != "" {
+		httpReq.Header.Set("Authorization", "Bearer "+apiKey)
+	} else if envName := strings.TrimSpace(req.Target.APIKeyEnv); envName != "" {
 		apiKey := strings.TrimSpace(os.Getenv(envName))
 		if apiKey == "" {
 			return nil, fmt.Errorf("%w: api key environment variable %q is not set", ErrInvalidRequest, envName)
@@ -110,6 +119,8 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 	effectiveTimeout := c.timeout
 	if req.Target.TimeoutSeconds > 0 {
 		effectiveTimeout = time.Duration(req.Target.TimeoutSeconds) * time.Second
+	} else if req.TargetPresence.TimeoutSeconds {
+		effectiveTimeout = 0
 	}
 
 	httpClient := c.httpClient
@@ -128,8 +139,8 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 	defer httpResp.Body.Close()
 
 	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
-		body, _ := io.ReadAll(io.LimitReader(httpResp.Body, 4096))
+		_, _ = io.Copy(io.Discard, io.LimitReader(httpResp.Body, 4096))
-		return nil, fmt.Errorf("%w: status=%d body=%q", ErrUnexpectedStatus, httpResp.StatusCode, strings.TrimSpace(string(body)))
+		return nil, fmt.Errorf("%w: status=%d", ErrUnexpectedStatus, httpResp.StatusCode)
 	}
 
 	var wireResp openAIChatResponse
@@ -151,6 +162,8 @@ func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.Genera
 			PromptTokens:     wireResp.Usage.PromptTokens,
 			CompletionTokens: wireResp.Usage.CompletionTokens,
 			TotalTokens:      wireResp.Usage.TotalTokens,
+			CachedTokens:     wireResp.Usage.PromptTokensDetails.CachedTokens,
+			CacheWriteTokens: wireResp.Usage.CacheWriteTokens,
 		},
 	}, nil
 }
@@ -167,27 +180,36 @@ func openAIChatRequestFromGenerateRequest(req domain.GenerateRequest, defaultMod
 	wireReq := openAIChatRequest{
 		Model: model,
 	}
-
+	if sessionID := strings.TrimSpace(req.Prompt.SessionID); sessionID != "" {
-	wireReq.Messages = make([]openAIChatMessage, 0, len(req.Prompt.Messages))
+		if n := utf8.RuneCountInString(sessionID); n > domain.SessionIDMaxLength {
-	for _, msg := range req.Prompt.Messages {
+			return openAIChatRequest{}, fmt.Errorf("session_id length %d exceeds maximum %d", n, domain.SessionIDMaxLength)
-		wireReq.Messages = append(wireReq.Messages, openAIChatMessage{
+		}
-			Role:    msg.Role,
+		wireReq.SessionID = sessionID
-			Content: msg.Content,
-		})
 	}
 
-	if req.Target.Temperature != 0 {
+	wireReq.Messages = make([]openAIChatRequestMessage, 0, len(req.Prompt.Messages))
+	for _, msg := range req.Prompt.Messages {
+		wireReq.Messages = append(wireReq.Messages, openAIChatRequestMessageFromRenderedMessage(msg))
+	}
+
+	if req.Target.Temperature != 0 || req.TargetPresence.Temperature {
 		wireReq.Temperature = &req.Target.Temperature
 	}
-	if req.Target.MaxTokens != 0 {
+	if req.Target.MaxTokens != 0 || req.TargetPresence.MaxTokens {
 		wireReq.MaxTokens = &req.Target.MaxTokens
 	}
-	if req.Target.TopP != 0 {
+	if req.Target.TopP != 0 || req.TargetPresence.TopP {
 		wireReq.TopP = &req.Target.TopP
 	}
 	if strings.TrimSpace(req.Target.ServiceTier) != "" {
 		wireReq.ServiceTier = req.Target.ServiceTier
 	}
+	if strings.TrimSpace(req.Target.ReasoningEffort) != "" {
+		wireReq.ReasoningEffort = req.Target.ReasoningEffort
+	}
+	if len(req.Target.ExtraParams) > 0 {
+		wireReq.ExtraParams = req.Target.ExtraParams
+	}
 	if req.StructuredOutput != nil {
 		responseFormat, err := toOpenAIResponseFormat(req.StructuredOutput)
 		if err != nil {
@@ -201,27 +223,105 @@ func openAIChatRequestFromGenerateRequest(req domain.GenerateRequest, defaultMod
 
 type openAIChatRequest struct {
 	Model           string                     `json:"model"`
-	Messages       []openAIChatMessage   `json:"messages"`
+	SessionID       string                     `json:"session_id,omitempty"`
+	Messages        []openAIChatRequestMessage `json:"messages"`
 	Temperature     *float64                   `json:"temperature,omitempty"`
 	MaxTokens       *int                       `json:"max_tokens,omitempty"`
 	TopP            *float64                   `json:"top_p,omitempty"`
 	ServiceTier     string                     `json:"service_tier,omitempty"`
+	ReasoningEffort string                     `json:"reasoning_effort,omitempty"`
 	ResponseFormat  *openAIResponseFormat      `json:"response_format,omitempty"`
+	ExtraParams     map[string]any             `json:"-"`
 }
 
-type openAIChatMessage struct {
+func openAIChatRequestPayload(req openAIChatRequest) (map[string]any, error) {
+	out := map[string]any{
+		"model":    req.Model,
+		"messages": req.Messages,
+	}
+	if req.SessionID != "" {
+		out["session_id"] = req.SessionID
+	}
+	if req.Temperature != nil {
+		out["temperature"] = *req.Temperature
+	}
+	if req.MaxTokens != nil {
+		out["max_tokens"] = *req.MaxTokens
+	}
+	if req.TopP != nil {
+		out["top_p"] = *req.TopP
+	}
+	if req.ServiceTier != "" {
+		out["service_tier"] = req.ServiceTier
+	}
+	if req.ReasoningEffort != "" {
+		out["reasoning_effort"] = req.ReasoningEffort
+	}
+	if req.ResponseFormat != nil {
+		out["response_format"] = req.ResponseFormat
+	}
+
+	for key, value := range req.ExtraParams {
+		if key == "" {
+			return nil, errors.New("extra_params key must not be empty")
+		}
+		if _, reserved := reservedOpenAIChatRequestFields[key]; reserved {
+			return nil, fmt.Errorf("extra_params key %q collides with reserved request field", key)
+		}
+		if _, err := json.Marshal(value); err != nil {
+			return nil, fmt.Errorf("extra_params.%s must be JSON-serializable: %w", key, err)
+		}
+		out[key] = value
+	}
+
+	return out, nil
+}
+
+var reservedOpenAIChatRequestFields = map[string]struct{}{
+	"model":            {},
+	"session_id":       {},
+	"messages":         {},
+	"temperature":      {},
+	"max_tokens":       {},
+	"top_p":            {},
+	"service_tier":     {},
+	"reasoning_effort": {},
+	"response_format":  {},
+}
+
+type openAIChatRequestMessage struct {
+	Role    string `json:"role"`
+	Content any    `json:"content"`
+}
+
+type openAIChatTextContentBlock struct {
+	Type         string              `json:"type"`
+	Text         string              `json:"text"`
+	CacheControl *openAICacheControl `json:"cache_control,omitempty"`
+}
+
+type openAICacheControl struct {
+	Type string `json:"type"`
+	TTL  string `json:"ttl,omitempty"`
+}
+
+type openAIChatResponseMessage struct {
 	Role    string `json:"role"`
 	Content string `json:"content"`
 }
 
 type openAIChatResponse struct {
 	Choices []struct {
-		Message openAIChatMessage `json:"message"`
+		Message openAIChatResponseMessage `json:"message"`
 	} `json:"choices"`
 	Usage struct {
 		PromptTokens        int `json:"prompt_tokens"`
 		CompletionTokens    int `json:"completion_tokens"`
 		TotalTokens         int `json:"total_tokens"`
+		PromptTokensDetails struct {
+			CachedTokens int `json:"cached_tokens"`
+		} `json:"prompt_tokens_details"`
+		CacheWriteTokens int `json:"cache_write_tokens"`
 	} `json:"usage"`
 }
 
@@ -236,6 +336,28 @@ type openAIJSONSchemaEnvelope struct {
 	Schema any    `json:"schema"`
 }
 
+func openAIChatRequestMessageFromRenderedMessage(msg domain.RenderedMessage) openAIChatRequestMessage {
+	wireMsg := openAIChatRequestMessage{
+		Role:    msg.Role,
+		Content: msg.Content,
+	}
+	if msg.CacheControl == nil {
+		return wireMsg
+	}
+
+	wireMsg.Content = []openAIChatTextContentBlock{
+		{
+			Type: "text",
+			Text: msg.Content,
+			CacheControl: &openAICacheControl{
+				Type: string(msg.CacheControl.Type),
+				TTL:  msg.CacheControl.TTL,
+			},
+		},
+	}
+	return wireMsg
+}
+
 func toOpenAIResponseFormat(spec *domain.StructuredOutputSpec) (*openAIResponseFormat, error) {
 	if spec == nil {
 		return nil, nil

internal/llm/openai_compatible_client_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"math"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -13,6 +14,64 @@ import (
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 )
 
+func TestNewOpenAICompatibleClientDoesNotMutateSuppliedZeroTimeoutClient(t *testing.T) {
+	transport := http.DefaultTransport
+	supplied := &http.Client{Transport: transport}
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		HTTPClient: supplied,
+	})
+	if err != nil {
+		t.Fatalf("unexpected constructor error: %v", err)
+	}
+
+	if supplied.Timeout != 0 {
+		t.Fatalf("expected supplied client timeout to remain zero, got %v", supplied.Timeout)
+	}
+	if client.httpClient == supplied {
+		t.Fatal("expected constructed client to use a cloned HTTP client")
+	}
+	if client.httpClient.Timeout != client.timeout {
+		t.Fatalf("expected cloned client timeout %v, got %v", client.timeout, client.httpClient.Timeout)
+	}
+	if client.httpClient.Timeout <= 0 {
+		t.Fatalf("expected constructed client to use a positive default timeout, got %v", client.httpClient.Timeout)
+	}
+	if client.httpClient.Transport != transport {
+		t.Fatal("expected cloned client to preserve the supplied transport")
+	}
+}
+
+func TestNewOpenAICompatibleClientDoesNotMutateSuppliedNonzeroTimeoutClient(t *testing.T) {
+	transport := http.DefaultTransport
+	suppliedTimeout := 37 * time.Second
+	supplied := &http.Client{
+		Timeout:   suppliedTimeout,
+		Transport: transport,
+	}
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		Timeout:    2 * time.Second,
+		HTTPClient: supplied,
+	})
+	if err != nil {
+		t.Fatalf("unexpected constructor error: %v", err)
+	}
+
+	if supplied.Timeout != suppliedTimeout {
+		t.Fatalf("expected supplied client timeout to remain %v, got %v", suppliedTimeout, supplied.Timeout)
+	}
+	if client.httpClient == supplied {
+		t.Fatal("expected constructed client to use a cloned HTTP client")
+	}
+	if client.httpClient.Timeout != suppliedTimeout {
+		t.Fatalf("expected cloned client timeout %v, got %v", suppliedTimeout, client.httpClient.Timeout)
+	}
+	if client.httpClient.Transport != transport {
+		t.Fatal("expected cloned client to preserve the supplied transport")
+	}
+}
+
 func TestOpenAICompatibleClientGenerateSuccess(t *testing.T) {
 	type observedRequest struct {
 		Authorization string
@@ -89,6 +148,9 @@ func TestOpenAICompatibleClientGenerateSuccess(t *testing.T) {
 	if resp.Usage.PromptTokens != 11 || resp.Usage.CompletionTokens != 22 || resp.Usage.TotalTokens != 33 {
 		t.Fatalf("unexpected usage: %+v", resp.Usage)
 	}
+	if resp.Usage.CachedTokens != 0 || resp.Usage.CacheWriteTokens != 0 {
+		t.Fatalf("expected absent cache usage fields to remain zero, got %+v", resp.Usage)
+	}
 
 	if obs.Authorization != "Bearer secret-key" {
 		t.Fatalf("unexpected Authorization header: %q", obs.Authorization)
@@ -144,6 +206,277 @@ func TestOpenAICompatibleClientGenerateSuccess(t *testing.T) {
 	}
 }
 
+func TestOpenAICompatibleClientDirectAPIKeyPreferredOverEnv(t *testing.T) {
+	const directKey = "direct-llm-key"
+	t.Setenv("SCRIPTORIUM_TEST_API_KEY", "env-key")
+
+	var gotAuth string
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotAuth = r.Header.Get("Authorization")
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{
+			Model:     "model",
+			APIKeyEnv: "SCRIPTORIUM_TEST_API_KEY",
+			APIKey:    directKey,
+		},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if gotAuth != "Bearer "+directKey {
+		t.Fatalf("unexpected Authorization header: %q", gotAuth)
+	}
+}
+
+func TestOpenAICompatibleClientSerializesCacheControlledMessageAsContentBlock(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+			{
+				Role:    "system",
+				Content: "Stable instructions.",
+				CacheControl: &domain.CacheControl{
+					Type: domain.CacheControlEphemeral,
+					TTL:  "1h",
+				},
+			},
+			{Role: "user", Content: "Dynamic request."},
+		}},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	for _, forbidden := range []string{"cache_control", "extra_params"} {
+		if _, exists := observedBody[forbidden]; exists {
+			t.Fatalf("expected top-level %s to be omitted, got %#v", forbidden, observedBody[forbidden])
+		}
+	}
+
+	msgs, ok := observedBody["messages"].([]any)
+	if !ok || len(msgs) != 2 {
+		t.Fatalf("unexpected messages payload: %#v", observedBody["messages"])
+	}
+	msg0 := msgs[0].(map[string]any)
+	if msg0["role"] != "system" {
+		t.Fatalf("unexpected first message role: %#v", msg0["role"])
+	}
+	contentBlocks, ok := msg0["content"].([]any)
+	if !ok || len(contentBlocks) != 1 {
+		t.Fatalf("expected first message content block array, got %#v", msg0["content"])
+	}
+	block := contentBlocks[0].(map[string]any)
+	if block["type"] != "text" || block["text"] != "Stable instructions." {
+		t.Fatalf("unexpected text content block: %#v", block)
+	}
+	cacheControl, ok := block["cache_control"].(map[string]any)
+	if !ok {
+		t.Fatalf("expected cache_control on content block, got %#v", block)
+	}
+	if cacheControl["type"] != string(domain.CacheControlEphemeral) || cacheControl["ttl"] != "1h" {
+		t.Fatalf("unexpected cache_control payload: %#v", cacheControl)
+	}
+
+	msg1 := msgs[1].(map[string]any)
+	if msg1["role"] != "user" || msg1["content"] != "Dynamic request." {
+		t.Fatalf("expected uncached message to keep string content, got %#v", msg1)
+	}
+}
+
+func TestOpenAICompatibleClientOmitsEmptyCacheControlTTL(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+			{
+				Role:    "system",
+				Content: "Stable instructions.",
+				CacheControl: &domain.CacheControl{
+					Type: domain.CacheControlEphemeral,
+				},
+			},
+		}},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	msgs := observedBody["messages"].([]any)
+	msg0 := msgs[0].(map[string]any)
+	contentBlocks := msg0["content"].([]any)
+	block := contentBlocks[0].(map[string]any)
+	cacheControl := block["cache_control"].(map[string]any)
+	if cacheControl["type"] != string(domain.CacheControlEphemeral) {
+		t.Fatalf("unexpected cache_control type: %#v", cacheControl)
+	}
+	if _, exists := cacheControl["ttl"]; exists {
+		t.Fatalf("expected empty ttl to be omitted, got %#v", cacheControl)
+	}
+}
+
+func TestOpenAICompatibleClientSerializesSessionID(t *testing.T) {
+	var observedBody map[string]any
+	var observedSessionHeader string
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		observedSessionHeader = r.Header.Get("x-session-id")
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{
+			SessionID: " session-123 ",
+			Messages:  []domain.RenderedMessage{{Role: "user", Content: "hi"}},
+		},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if observedBody["session_id"] != "session-123" {
+		t.Fatalf("expected top-level session_id, got %#v", observedBody["session_id"])
+	}
+	if observedSessionHeader != "" {
+		t.Fatalf("did not expect x-session-id header, got %q", observedSessionHeader)
+	}
+}
+
+func TestOpenAICompatibleClientOmitsEmptySessionID(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{
+			SessionID: "   ",
+			Messages:  []domain.RenderedMessage{{Role: "user", Content: "hi"}},
+		},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if _, exists := observedBody["session_id"]; exists {
+		t.Fatalf("expected empty session_id to be omitted, got %#v", observedBody["session_id"])
+	}
+}
+
+func TestOpenAICompatibleClientRejectsTooLongSessionID(t *testing.T) {
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		BaseURL: "http://example.com/v1",
+		Model:   "model",
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{
+			SessionID: strings.Repeat("x", domain.SessionIDMaxLength+1),
+			Messages:  []domain.RenderedMessage{{Role: "user", Content: "hi"}},
+		},
+	})
+	if err == nil {
+		t.Fatal("expected invalid request error")
+	}
+	if !errors.Is(err, ErrInvalidRequest) {
+		t.Fatalf("expected ErrInvalidRequest, got %v", err)
+	}
+}
+
+func TestOpenAICompatibleClientParsesCacheUsage(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		_, _ = w.Write([]byte(`{
+  "choices": [{"message": {"role": "assistant", "content": "ok"}}],
+  "usage": {
+    "prompt_tokens": 100,
+    "completion_tokens": 20,
+    "total_tokens": 120,
+    "prompt_tokens_details": {"cached_tokens": 80},
+    "cache_write_tokens": 60
+  }
+}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1", Model: "model"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	resp, err := client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if resp.Usage.PromptTokens != 100 || resp.Usage.CompletionTokens != 20 || resp.Usage.TotalTokens != 120 {
+		t.Fatalf("unexpected base usage fields: %+v", resp.Usage)
+	}
+	if resp.Usage.CachedTokens != 80 || resp.Usage.CacheWriteTokens != 60 {
+		t.Fatalf("unexpected cache usage fields: %+v", resp.Usage)
+	}
+}
+
 func TestOpenAICompatibleClientOmitsResponseFormatWhenNoStructuredOutput(t *testing.T) {
 	var observedBody map[string]any
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
@@ -175,7 +508,7 @@ func TestOpenAICompatibleClientOmitsResponseFormatWhenNoStructuredOutput(t *test
 	}
 }
 
-func TestOpenAICompatibleClientOmitsReasoningEffortAndExtraParams(t *testing.T) {
+func TestOpenAICompatibleClientSerializesReasoningEffortAndExtraParams(t *testing.T) {
 	var observedBody map[string]any
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		defer r.Body.Close()
@@ -196,19 +529,257 @@ func TestOpenAICompatibleClientOmitsReasoningEffortAndExtraParams(t *testing.T)
 		Target: domain.ExecutionTarget{
 			Model:           "model",
 			ReasoningEffort: "high",
-			ExtraParams: map[string]string{
+			ExtraParams: map[string]any{
-				"provider_option": "on",
+				"string_value":  "on",
+				"number_value":  42,
+				"boolean_value": true,
+				"object_value":  map[string]any{"nested": "value", "count": 2},
+				"array_value":   []any{"first", 3, false},
 			},
 		},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
 	}
+	if observedBody["reasoning_effort"] != "high" {
+		t.Fatalf("expected reasoning_effort high, got %#v", observedBody["reasoning_effort"])
+	}
+	if observedBody["string_value"] != "on" {
+		t.Fatalf("unexpected string extra param: %#v", observedBody["string_value"])
+	}
+	if observedBody["number_value"] != float64(42) {
+		t.Fatalf("unexpected number extra param: %#v", observedBody["number_value"])
+	}
+	if observedBody["boolean_value"] != true {
+		t.Fatalf("unexpected boolean extra param: %#v", observedBody["boolean_value"])
+	}
+	objectValue, ok := observedBody["object_value"].(map[string]any)
+	if !ok || objectValue["nested"] != "value" || objectValue["count"] != float64(2) {
+		t.Fatalf("unexpected object extra param: %#v", observedBody["object_value"])
+	}
+	if _, exists := observedBody["extra_params"]; exists {
+		t.Fatalf("expected extra_params wrapper omitted, got %#v", observedBody["extra_params"])
+	}
+	arrayValue, ok := observedBody["array_value"].([]any)
+	if !ok || len(arrayValue) != 3 || arrayValue[0] != "first" || arrayValue[1] != float64(3) || arrayValue[2] != false {
+		t.Fatalf("unexpected array extra param: %#v", observedBody["array_value"])
+	}
+}
+
+func TestOpenAICompatibleClientOmitsReasoningEffortWhenUnset(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
 	if _, exists := observedBody["reasoning_effort"]; exists {
 		t.Fatalf("expected reasoning_effort omitted, got %#v", observedBody["reasoning_effort"])
 	}
 	if _, exists := observedBody["extra_params"]; exists {
-		t.Fatalf("expected extra_params omitted, got %#v", observedBody["extra_params"])
+		t.Fatalf("expected extra_params wrapper omitted, got %#v", observedBody["extra_params"])
+	}
+}
+
+func TestOpenAICompatibleClientSerializesExplicitZeroNumericOverrides(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Model: "model"},
+		TargetPresence: domain.ExecutionTargetPresence{
+			Temperature: true,
+			MaxTokens:   true,
+			TopP:        true,
+		},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if observedBody["temperature"] != float64(0) {
+		t.Fatalf("expected explicit zero temperature, got %#v", observedBody["temperature"])
+	}
+	if observedBody["max_tokens"] != float64(0) {
+		t.Fatalf("expected explicit zero max_tokens, got %#v", observedBody["max_tokens"])
+	}
+	if observedBody["top_p"] != float64(0) {
+		t.Fatalf("expected explicit zero top_p, got %#v", observedBody["top_p"])
+	}
+}
+
+func TestOpenAICompatibleClientOmitsImplicitZeroNumericFields(t *testing.T) {
+	var observedBody map[string]any
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+		if err := json.NewDecoder(r.Body).Decode(&observedBody); err != nil {
+			t.Fatalf("failed to decode request body: %v", err)
+		}
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Model: "model"},
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	for _, field := range []string{"temperature", "max_tokens", "top_p"} {
+		if _, exists := observedBody[field]; exists {
+			t.Fatalf("expected implicit zero field %q to be omitted, got body %#v", field, observedBody)
+		}
+	}
+}
+
+func TestOpenAICompatibleClientExplicitZeroTimeoutDisablesClientTimeout(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(20 * time.Millisecond)
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		BaseURL: ts.URL + "/v1",
+		Timeout: time.Nanosecond,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt:         domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target:         domain.ExecutionTarget{Model: "model", TimeoutSeconds: 0},
+		TargetPresence: domain.ExecutionTargetPresence{TimeoutSeconds: true},
+	})
+	if err != nil {
+		t.Fatalf("expected explicit zero timeout to disable client timeout, got %v", err)
+	}
+}
+
+func TestOpenAICompatibleClientOmittedTimeoutUsesClientTimeout(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		time.Sleep(20 * time.Millisecond)
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+	}))
+	defer ts.Close()
+
+	client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{
+		BaseURL: ts.URL + "/v1",
+		Timeout: time.Nanosecond,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	_, err = client.Generate(context.Background(), domain.GenerateRequest{
+		Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+		Target: domain.ExecutionTarget{Model: "model", TimeoutSeconds: 0},
+	})
+	if err == nil {
+		t.Fatal("expected omitted timeout to use client timeout")
+	}
+	if !errors.Is(err, ErrRequestFailed) {
+		t.Fatalf("expected ErrRequestFailed, got %v", err)
+	}
+}
+
+func TestOpenAICompatibleClientRejectsInvalidExtraParamsBeforeProviderCall(t *testing.T) {
+	tests := []struct {
+		name        string
+		extraParams map[string]any
+		want        string
+	}{
+		{name: "empty key", extraParams: map[string]any{"": "empty"}, want: "key must not be empty"},
+		{name: "unserializable value", extraParams: map[string]any{"bad": math.Inf(1)}, want: "JSON-serializable"},
+	}
+	for _, key := range []string{
+		"model",
+		"session_id",
+		"messages",
+		"temperature",
+		"max_tokens",
+		"top_p",
+		"service_tier",
+		"reasoning_effort",
+		"response_format",
+	} {
+		tests = append(tests, struct {
+			name        string
+			extraParams map[string]any
+			want        string
+		}{
+			name:        "reserved key " + key,
+			extraParams: map[string]any{key: "collision"},
+			want:        "reserved request field",
+		})
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			called := false
+			ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				called = true
+				_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"ok"}}]}`))
+			}))
+			defer ts.Close()
+
+			client, err := NewOpenAICompatibleClient(OpenAICompatibleConfig{BaseURL: ts.URL + "/v1"})
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			_, err = client.Generate(context.Background(), domain.GenerateRequest{
+				Prompt: domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "user", Content: "hi"}}},
+				Target: domain.ExecutionTarget{Model: "model", ExtraParams: tc.extraParams},
+			})
+			if err == nil {
+				t.Fatal("expected invalid request error")
+			}
+			if !errors.Is(err, ErrInvalidRequest) {
+				t.Fatalf("expected ErrInvalidRequest, got %v", err)
+			}
+			if !strings.Contains(err.Error(), tc.want) {
+				t.Fatalf("expected error to contain %q, got %v", tc.want, err)
+			}
+			if called {
+				t.Fatal("provider should not be called for invalid extra_params")
+			}
+		})
 	}
 }
 
@@ -332,9 +903,10 @@ func TestOpenAICompatibleClientEndpointOverride(t *testing.T) {
 }
 
 func TestOpenAICompatibleClientNon2xxError(t *testing.T) {
+	const sensitiveBody = `provider-secret-fragment request_payload_details`
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusBadRequest)
-		_, _ = w.Write([]byte(`{"error":"bad request payload"}`))
+		_, _ = w.Write([]byte(`{"error":"` + sensitiveBody + `"}`))
 	}))
 	defer ts.Close()
 
@@ -352,8 +924,11 @@ func TestOpenAICompatibleClientNon2xxError(t *testing.T) {
 	if !errors.Is(err, ErrUnexpectedStatus) {
 		t.Fatalf("expected ErrUnexpectedStatus, got %v", err)
 	}
-	if !strings.Contains(err.Error(), "400") || !strings.Contains(err.Error(), "bad request payload") {
+	if !strings.Contains(err.Error(), "status=400") {
-		t.Fatalf("expected status/body details, got %v", err)
+		t.Fatalf("expected status detail, got %v", err)
+	}
+	if strings.Contains(err.Error(), sensitiveBody) {
+		t.Fatalf("expected provider response body to be redacted, got %v", err)
 	}
 }
 

internal/profile/builtin/assets/aion-labs/aion-2.yml

@@ -0,0 +1,9 @@
+id: aion-2
+endpoint: https://openrouter.ai/api/v1
+model: aion-labs/aion-2.0
+temperature: 0.72
+reasoning_effort: high
+top_p: 0.95
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/anthropic/claude-fable-latest.yml

@@ -0,0 +1,7 @@
+id: claude-fable-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~anthropic/claude-fable-latest"
+reasoning_effort: high
+timeout_seconds: 600
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/anthropic/claude-haiku-latest.yml

@@ -0,0 +1,7 @@
+id: claude-haiku-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~anthropic/claude-haiku-latest"
+reasoning_effort: medium
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/anthropic/claude-opus-latest.yml

@@ -0,0 +1,7 @@
+id: claude-opus-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~anthropic/claude-opus-latest"
+reasoning_effort: high
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/anthropic/claude-sonnet-latest.yml

@@ -0,0 +1,7 @@
+id: claude-sonnet-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~anthropic/claude-sonnet-latest"
+reasoning_effort: high
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/deepseek/deepseek-3-2.yml

@@ -0,0 +1,7 @@
+id: deepseek-3-2
+endpoint: https://openrouter.ai/api/v1
+model: deepseek/deepseek-v3.2
+reasoning_effort: high
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/deepseek/deepseek-4-pro.yml

@@ -0,0 +1,7 @@
+id: deepseek-4-pro
+endpoint: https://openrouter.ai/api/v1
+model: deepseek/deepseek-v4-pro
+reasoning_effort: high
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-2-flash-lite.yml

@@ -0,0 +1,9 @@
+id: gemini-2-flash-lite
+endpoint: https://openrouter.ai/api/v1
+model: "google/gemini-2.5-flash-lite"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-2-flash.yml

@@ -0,0 +1,9 @@
+id: gemini-2-flash
+endpoint: https://openrouter.ai/api/v1
+model: "google/gemini-2.5-flash"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-2-pro.yml

@@ -0,0 +1,9 @@
+id: gemini-2-pro
+endpoint: https://openrouter.ai/api/v1
+model: "google/gemini-2.5-pro"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-3-flash-lite.yml

@@ -0,0 +1,9 @@
+id: gemini-3-flash-lite
+endpoint: https://openrouter.ai/api/v1
+model: "google/gemini-3.1-flash-lite"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-flash-latest.yml

@@ -0,0 +1,9 @@
+id: gemini-flash-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~google/gemini-flash-latest"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemini-pro-latest.yml

@@ -0,0 +1,9 @@
+id: gemini-pro-latest
+endpoint: https://openrouter.ai/api/v1
+model: "~google/gemini-pro-latest"
+#temperature: 0.15
+reasoning_effort: high
+#top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/google/gemma-4-31b.yml

@@ -0,0 +1,9 @@
+id: gemma-4-31b
+endpoint: https://openrouter.ai/api/v1
+model: google/gemma-4-31b-it:exacto
+temperature: 0.15
+reasoning_effort: high
+top_p: 0.98
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/minimax/minimax-m2.yml

@@ -0,0 +1,9 @@
+id: minimax-m2
+endpoint: https://openrouter.ai/api/v1
+model: minimax/minimax-m2.5
+temperature: 0.5
+reasoning_effort: high
+top_p: 0.95
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/minimax/minimax-m3.yml

@@ -0,0 +1,9 @@
+id: minimax-m3
+endpoint: https://openrouter.ai/api/v1
+model: minimax/minimax-m3
+#temperature: 0.5
+reasoning_effort: high
+#top_p: 0.95
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/mistral/mistral-large-2512.yml

@@ -0,0 +1,7 @@
+id: mistral-large-2512
+endpoint: https://openrouter.ai/api/v1
+model: mistralai/mistral-large-2512
+temperature: 0.15
+top_p: 0.98
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY

internal/profile/builtin/assets/mistral/mistral-medium-3-5.yml

@@ -0,0 +1,8 @@
+id: mistral-medium-3-5
+endpoint: https://openrouter.ai/api/v1
+model: mistralai/mistral-medium-3-5
+temperature: 0.15
+reasoning_effort: high
+top_p: 0.98
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY

internal/profile/builtin/assets/mistral/mistral-small-3.yml

@@ -0,0 +1,7 @@
+id: mistral-small-3
+endpoint: https://openrouter.ai/api/v1
+model: mistralai/mistral-small-3.2-24b-instruct
+temperature: 0.05
+top_p: 1.0
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY

internal/profile/builtin/assets/mistral/mistral-small-4.yml

@@ -0,0 +1,8 @@
+id: mistral-small-4
+endpoint: https://openrouter.ai/api/v1
+model: mistralai/mistral-small-2603
+temperature: 0.1
+reasoning_effort: high
+top_p: 0.98
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY

internal/profile/builtin/assets/nvidia/nemotron-3-ultra.yml

@@ -0,0 +1,7 @@
+id: nemotron-3-ultra
+endpoint: https://openrouter.ai/api/v1
+model: nvidia/nemotron-3-ultra-550b-a55b
+reasoning_effort: high
+timeout_seconds: 180
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/openai/gpt-5-mini.yml

@@ -0,0 +1,7 @@
+id: gpt-5-mini
+endpoint: https://openrouter.ai/api/v1
+model: "openai/gpt-5.4-mini"
+reasoning_effort: high
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/assets/openai/gpt-5-nano.yml

@@ -0,0 +1,7 @@
+id: gpt-5-nano
+endpoint: https://openrouter.ai/api/v1
+model: "openai/gpt-5.4-nano"
+reasoning_effort: high
+timeout_seconds: 240
+api_key_env: OPENROUTER_API_KEY
+service_tier: flex

internal/profile/builtin/repository.go

@@ -0,0 +1,31 @@
+package builtin
+
+import (
+	"embed"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+)
+
+const assetRoot = "assets"
+
+//go:embed assets/**/*.yml
+var assets embed.FS
+
+func NewRepository() profile.Repository {
+	return profile.NewFSRepository(assets, assetRoot)
+}
+
+func NewRepositoryWithPrimary(primary profile.Repository) profile.Repository {
+	if primary == nil {
+		return NewRepository()
+	}
+	return profile.NewOverlayRepository(primary, NewRepository())
+}
+
+func NewRepositoryWithDirectory(dir string) profile.Repository {
+	if strings.TrimSpace(dir) == "" {
+		return NewRepository()
+	}
+	return NewRepositoryWithPrimary(profile.NewFilesystemRepository(dir))
+}

internal/profile/builtin/repository_test.go

@@ -0,0 +1,127 @@
+package builtin
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+	"gopkg.in/yaml.v3"
+)
+
+func TestBuiltInProfilesValidateThroughRepository(t *testing.T) {
+	repo := NewRepository()
+	ids := loadBuiltInProfileIDs(t)
+	if len(ids) == 0 {
+		t.Fatal("expected built-in profiles")
+	}
+
+	for id := range ids {
+		t.Run(id, func(t *testing.T) {
+			p, err := repo.GetProfile(context.Background(), id)
+			if err != nil {
+				t.Fatalf("expected built-in profile %q to load, got %v", id, err)
+			}
+			if p.ID != id {
+				t.Fatalf("expected profile id %q, got %q", id, p.ID)
+			}
+		})
+	}
+}
+
+func TestBuiltInProfilesDoNotContainDuplicateIDsOrRawAPIKeys(t *testing.T) {
+	loadBuiltInProfileIDs(t)
+}
+
+func loadBuiltInProfileIDs(t *testing.T) map[string]string {
+	t.Helper()
+
+	ids := map[string]string{}
+	err := fs.WalkDir(assets, assetRoot, func(name string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if d.IsDir() || !strings.HasSuffix(name, ".yml") {
+			return nil
+		}
+
+		data, err := assets.ReadFile(name)
+		if err != nil {
+			t.Fatalf("failed to read built-in profile %s: %v", name, err)
+		}
+
+		var raw map[string]any
+		if err := yaml.Unmarshal(data, &raw); err != nil {
+			t.Fatalf("failed to decode built-in profile %s: %v", name, err)
+		}
+		if _, ok := raw["api_key"]; ok {
+			t.Fatalf("built-in profile %s contains raw api_key", name)
+		}
+		id, ok := raw["id"].(string)
+		if !ok || strings.TrimSpace(id) == "" {
+			t.Fatalf("built-in profile %s has missing id", name)
+		}
+		if previous, ok := ids[id]; ok {
+			t.Fatalf("duplicate built-in profile id %q in %s and %s", id, previous, name)
+		}
+		ids[id] = name
+		return nil
+	})
+	if err != nil {
+		t.Fatalf("failed to walk built-in profiles: %v", err)
+	}
+	return ids
+}
+
+func TestRepositoryWithPrimaryUsesPrimaryBeforeBuiltIns(t *testing.T) {
+	repo := NewRepositoryWithPrimary(staticProfileRepo{
+		profiles: map[string]string{"mistral-small-3": "custom-model"},
+	})
+
+	p, err := repo.GetProfile(context.Background(), "mistral-small-3")
+	if err != nil {
+		t.Fatalf("expected profile to load, got %v", err)
+	}
+	if p.Model != "custom-model" {
+		t.Fatalf("expected primary profile to override built-in, got %+v", p)
+	}
+}
+
+func TestRepositoryWithPrimaryFallsBackToBuiltIns(t *testing.T) {
+	repo := NewRepositoryWithPrimary(staticProfileRepo{})
+
+	p, err := repo.GetProfile(context.Background(), "mistral-small-3")
+	if err != nil {
+		t.Fatalf("expected built-in profile to load, got %v", err)
+	}
+	if p.ID != "mistral-small-3" {
+		t.Fatalf("unexpected profile: %+v", p)
+	}
+}
+
+func TestRepositoryWithPrimaryDoesNotFallBackAfterPrimaryError(t *testing.T) {
+	repo := NewRepositoryWithPrimary(staticProfileRepo{err: profile.ErrInvalidProfile})
+
+	_, err := repo.GetProfile(context.Background(), "mistral-small-3")
+	if !errors.Is(err, profile.ErrInvalidProfile) {
+		t.Fatalf("expected primary error, got %v", err)
+	}
+}
+
+type staticProfileRepo struct {
+	profiles map[string]string
+	err      error
+}
+
+func (r staticProfileRepo) GetProfile(_ context.Context, id string) (*domain.ExecutionProfile, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+	if model, ok := r.profiles[id]; ok {
+		return &domain.ExecutionProfile{ID: id, Endpoint: "http://primary/v1", Model: model}, nil
+	}
+	return nil, profile.ErrProfileNotFound
+}

internal/profile/filesystem_repository.go

@@ -5,8 +5,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
-	"path/filepath"
+	"path"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
@@ -30,11 +31,56 @@ func NewFilesystemRepository(dir string) Repository {
 }
 
 func (r *filesystemRepository) GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error) {
+	return loadProfile(ctx, os.DirFS(r.dir), ".", id)
+}
+
+type fsRepository struct {
+	fsys fs.FS
+	root string
+}
+
+func NewFSRepository(fsys fs.FS, root string) Repository {
+	return &fsRepository{fsys: fsys, root: root}
+}
+
+func (r *fsRepository) GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error) {
+	return loadProfile(ctx, r.fsys, r.root, id)
+}
+
+type overlayRepository struct {
+	primary  Repository
+	fallback Repository
+}
+
+func NewOverlayRepository(primary, fallback Repository) Repository {
+	return &overlayRepository{primary: primary, fallback: fallback}
+}
+
+func (r *overlayRepository) GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error) {
+	if r.primary != nil {
+		prof, err := r.primary.GetProfile(ctx, id)
+		if err == nil {
+			return prof, nil
+		}
+		if !errors.Is(err, ErrProfileNotFound) {
+			return nil, err
+		}
+	}
+	if r.fallback == nil {
+		return nil, ErrProfileNotFound
+	}
+	return r.fallback.GetProfile(ctx, id)
+}
+
+func loadProfile(ctx context.Context, fsys fs.FS, root string, id string) (*domain.ExecutionProfile, error) {
 	if strings.TrimSpace(id) == "" {
 		return nil, fmt.Errorf("%w: profile id is required", ErrInvalidProfile)
 	}
+	if fsys == nil {
+		return nil, fmt.Errorf("failed to read profile directory: filesystem is nil")
+	}
 
-	files, err := filecatalog.FindYAMLFiles(ctx, r.dir)
+	files, err := filecatalog.FindFSYAMLFiles(ctx, fsys, root)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read profile directory: %w", err)
 	}
@@ -47,9 +93,9 @@ func (r *filesystemRepository) GetProfile(ctx context.Context, id string) (*doma
 		default:
 		}
 
-		relPath := filecatalog.RelativePath(r.dir, fullPath)
+		relPath := filecatalog.DisplayPath(root, fullPath)
-		fileMatch := filecatalog.Stem(filepath.Base(fullPath)) == id
+		fileMatch := filecatalog.Stem(path.Base(fullPath)) == id
-		data, err := os.ReadFile(fullPath)
+		data, err := fs.ReadFile(fsys, fullPath)
 		if err != nil {
 			return nil, fmt.Errorf("failed to read profile file %s: %w", relPath, err)
 		}

internal/profile/repository_test.go

@@ -2,11 +2,15 @@ package profile
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
+	"testing/fstest"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 )
 
 func TestFilesystemRepository_GetProfile(t *testing.T) {
@@ -85,6 +89,63 @@ temperature: 0.1
 		}
 	})
 
+	t.Run("valid profile with JSON-compatible extra params", func(t *testing.T) {
+		writeProfileTestFile(t, filepath.Join(tmpDir, "json-extra-params.yaml"), `
+id: json-extra-params
+endpoint: http://localhost:8000/v1
+model: nested-model
+extra_params:
+  string_value: enabled
+  number_value: 42
+  boolean_value: true
+  object_value:
+    nested: value
+    count: 2
+  array_value:
+    - first
+    - 3
+    - false
+`)
+
+		p, err := repo.GetProfile(ctx, "json-extra-params")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+
+		var got map[string]any
+		encoded, err := json.Marshal(p.ExtraParams)
+		if err != nil {
+			t.Fatalf("expected extra_params to marshal as JSON, got %v", err)
+		}
+		if err := json.Unmarshal(encoded, &got); err != nil {
+			t.Fatalf("expected extra_params JSON to decode, got %v", err)
+		}
+
+		if got["string_value"] != "enabled" {
+			t.Fatalf("unexpected string extra param: %#v", got["string_value"])
+		}
+		if got["number_value"] != float64(42) {
+			t.Fatalf("unexpected number extra param: %#v", got["number_value"])
+		}
+		if got["boolean_value"] != true {
+			t.Fatalf("unexpected boolean extra param: %#v", got["boolean_value"])
+		}
+		objectValue, ok := got["object_value"].(map[string]any)
+		if !ok {
+			t.Fatalf("expected object extra param, got %#v", got["object_value"])
+		}
+		if objectValue["nested"] != "value" || objectValue["count"] != float64(2) {
+			t.Fatalf("unexpected object extra param: %#v", objectValue)
+		}
+		arrayValue, ok := got["array_value"].([]any)
+		if !ok {
+			t.Fatalf("expected array extra param, got %#v", got["array_value"])
+		}
+		if len(arrayValue) != 3 || arrayValue[0] != "first" || arrayValue[1] != float64(3) || arrayValue[2] != false {
+			t.Fatalf("unexpected array extra param: %#v", arrayValue)
+		}
+	})
+
 	t.Run("duplicate profile IDs fail as ambiguous", func(t *testing.T) {
 		writeProfileTestFile(t, filepath.Join(tmpDir, "duplicate-profile-a.yaml"), `
 id: duplicate-profile
@@ -203,3 +264,216 @@ func writeProfileTestFile(t *testing.T, path string, content string) {
 		t.Fatalf("failed to write profile test file %q: %v", path, err)
 	}
 }
+
+func TestFSRepository(t *testing.T) {
+	ctx := context.Background()
+
+	t.Run("loads valid profiles from nested directories", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"profiles/provider/nested.yaml": profileMapFile(`
+id: nested-profile
+endpoint: http://localhost:8000/v1
+model: nested-model
+temperature: 0.1
+`),
+		}, "profiles")
+
+		p, err := repo.GetProfile(ctx, "nested-profile")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.ID != "nested-profile" || p.Model != "nested-model" {
+			t.Fatalf("unexpected profile: %+v", p)
+		}
+	})
+
+	t.Run("rejects unknown YAML fields", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"profiles/unknown.yaml": profileMapFile(`
+id: unknown-profile
+endpoint: http://localhost:8000/v1
+model: model
+unknown: value
+`),
+		}, "profiles")
+
+		_, err := repo.GetProfile(ctx, "unknown-profile")
+		if !errors.Is(err, ErrInvalidYAML) {
+			t.Fatalf("expected ErrInvalidYAML, got %v", err)
+		}
+	})
+
+	t.Run("rejects raw api_key in selected profile", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"profiles/raw.yaml": profileMapFile(`
+id: raw-profile
+endpoint: http://localhost:8000/v1
+model: model
+api_key: secret
+`),
+		}, "profiles")
+
+		_, err := repo.GetProfile(ctx, "raw-profile")
+		if !errors.Is(err, ErrRawAPIKeyNotAllowed) {
+			t.Fatalf("expected ErrRawAPIKeyNotAllowed, got %v", err)
+		}
+	})
+
+	t.Run("ignores raw api_key in non-selected profiles", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"profiles/raw.yaml": profileMapFile(`
+id: raw-profile
+endpoint: http://localhost:8000/v1
+model: model
+api_key: secret
+`),
+			"profiles/valid.yaml": profileMapFile(`
+id: valid-profile
+endpoint: http://localhost:8000/v1
+model: model
+`),
+		}, "profiles")
+
+		p, err := repo.GetProfile(ctx, "valid-profile")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.ID != "valid-profile" {
+			t.Fatalf("unexpected profile: %+v", p)
+		}
+	})
+
+	t.Run("rejects duplicate IDs within one source", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"profiles/a.yaml": profileMapFile(`
+id: duplicate-profile
+endpoint: http://localhost:8000/v1
+model: first
+`),
+			"profiles/nested/b.yaml": profileMapFile(`
+id: duplicate-profile
+endpoint: http://localhost:8000/v1
+model: second
+`),
+		}, "profiles")
+
+		_, err := repo.GetProfile(ctx, "duplicate-profile")
+		if !errors.Is(err, ErrInvalidProfile) {
+			t.Fatalf("expected ErrInvalidProfile, got %v", err)
+		}
+		for _, want := range []string{"duplicate execution profile id", "a.yaml", "nested/b.yaml"} {
+			if !strings.Contains(err.Error(), want) {
+				t.Fatalf("expected error to contain %q, got %v", want, err)
+			}
+		}
+	})
+}
+
+func TestOverlayRepository(t *testing.T) {
+	ctx := context.Background()
+	primaryProfile := &domain.ExecutionProfile{ID: "shared", Endpoint: "http://primary", Model: "primary"}
+	fallbackProfile := &domain.ExecutionProfile{ID: "shared", Endpoint: "http://fallback", Model: "fallback"}
+
+	t.Run("returns primary matches before fallback matches", func(t *testing.T) {
+		repo := NewOverlayRepository(
+			staticProfileRepo{profiles: map[string]*domain.ExecutionProfile{"shared": primaryProfile}},
+			staticProfileRepo{profiles: map[string]*domain.ExecutionProfile{"shared": fallbackProfile}},
+		)
+
+		p, err := repo.GetProfile(ctx, "shared")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.Model != "primary" {
+			t.Fatalf("expected primary profile, got %+v", p)
+		}
+	})
+
+	t.Run("falls back on primary not found", func(t *testing.T) {
+		repo := NewOverlayRepository(
+			staticProfileRepo{},
+			staticProfileRepo{profiles: map[string]*domain.ExecutionProfile{"shared": fallbackProfile}},
+		)
+
+		p, err := repo.GetProfile(ctx, "shared")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.Model != "fallback" {
+			t.Fatalf("expected fallback profile, got %+v", p)
+		}
+	})
+
+	t.Run("does not fall back after primary load errors", func(t *testing.T) {
+		for _, tc := range []struct {
+			name string
+			err  error
+		}{
+			{name: "invalid yaml", err: ErrInvalidYAML},
+			{name: "invalid profile", err: ErrInvalidProfile},
+			{name: "raw api key", err: ErrRawAPIKeyNotAllowed},
+		} {
+			t.Run(tc.name, func(t *testing.T) {
+				repo := NewOverlayRepository(
+					staticProfileRepo{err: tc.err},
+					staticProfileRepo{profiles: map[string]*domain.ExecutionProfile{"shared": fallbackProfile}},
+				)
+
+				_, err := repo.GetProfile(ctx, "shared")
+				if !errors.Is(err, tc.err) {
+					t.Fatalf("expected %v, got %v", tc.err, err)
+				}
+			})
+		}
+	})
+
+	t.Run("returns not found when both sources miss", func(t *testing.T) {
+		repo := NewOverlayRepository(staticProfileRepo{}, staticProfileRepo{})
+
+		_, err := repo.GetProfile(ctx, "missing")
+		if !errors.Is(err, ErrProfileNotFound) {
+			t.Fatalf("expected ErrProfileNotFound, got %v", err)
+		}
+	})
+
+	t.Run("nil primary uses fallback", func(t *testing.T) {
+		repo := NewOverlayRepository(nil, staticProfileRepo{profiles: map[string]*domain.ExecutionProfile{"shared": fallbackProfile}})
+
+		p, err := repo.GetProfile(ctx, "shared")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.Model != "fallback" {
+			t.Fatalf("expected fallback profile, got %+v", p)
+		}
+	})
+
+	t.Run("nil fallback returns not found after primary miss", func(t *testing.T) {
+		repo := NewOverlayRepository(staticProfileRepo{}, nil)
+
+		_, err := repo.GetProfile(ctx, "missing")
+		if !errors.Is(err, ErrProfileNotFound) {
+			t.Fatalf("expected ErrProfileNotFound, got %v", err)
+		}
+	})
+}
+
+func profileMapFile(content string) *fstest.MapFile {
+	return &fstest.MapFile{Data: []byte(strings.TrimLeft(content, "\n"))}
+}
+
+type staticProfileRepo struct {
+	profiles map[string]*domain.ExecutionProfile
+	err      error
+}
+
+func (r staticProfileRepo) GetProfile(_ context.Context, id string) (*domain.ExecutionProfile, error) {
+	if r.err != nil {
+		return nil, r.err
+	}
+	if p, ok := r.profiles[id]; ok {
+		cp := *p
+		return &cp, nil
+	}
+	return nil, ErrProfileNotFound
+}

internal/prompt/go_renderer.go

@@ -6,7 +6,9 @@ import (
 	"errors"
 	"fmt"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"strings"
 	"text/template"
+	"unicode/utf8"
 )
 
 var (
@@ -50,6 +52,11 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 		},
 	}
 
+	sessionID, err := renderSessionID(definition.SessionID, funcs, vars)
+	if err != nil {
+		return nil, err
+	}
+
 	var renderedMessages []domain.RenderedMessage
 
 	for i, tmplMsg := range definition.Templates {
@@ -77,10 +84,42 @@ func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefini
 		renderedMessages = append(renderedMessages, domain.RenderedMessage{
 			Role:         tmplMsg.Role,
 			Content:      buf.String(),
+			CacheControl: cloneCacheControl(tmplMsg.CacheControl),
 		})
 	}
 
 	return &domain.RenderedPrompt{
+		SessionID: sessionID,
 		Messages:  renderedMessages,
 	}, nil
 }
+
+func renderSessionID(raw string, funcs template.FuncMap, vars map[string]string) (string, error) {
+	if strings.TrimSpace(raw) == "" {
+		return "", nil
+	}
+
+	tmpl, err := template.New("session_id").Funcs(funcs).Option("missingkey=error").Parse(raw)
+	if err != nil {
+		return "", fmt.Errorf("%w: session_id: %v", ErrInvalidTemplate, err)
+	}
+
+	var buf bytes.Buffer
+	if err := tmpl.Execute(&buf, vars); err != nil {
+		return "", fmt.Errorf("%w: session_id: %w", ErrRenderFailure, err)
+	}
+
+	sessionID := strings.TrimSpace(buf.String())
+	if n := utf8.RuneCountInString(sessionID); n > domain.SessionIDMaxLength {
+		return "", fmt.Errorf("%w: session_id length %d exceeds maximum %d", ErrRenderFailure, n, domain.SessionIDMaxLength)
+	}
+	return sessionID, nil
+}
+
+func cloneCacheControl(in *domain.CacheControl) *domain.CacheControl {
+	if in == nil {
+		return nil
+	}
+	out := *in
+	return &out
+}

internal/prompt/renderer_test.go

@@ -3,6 +3,7 @@ package prompt
 import (
 	"context"
 	"errors"
+	"strings"
 	"testing"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
@@ -78,6 +79,66 @@ func TestGoRenderer_Render(t *testing.T) {
 		}
 	})
 
+	t.Run("copying cache control to rendered messages", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{
+					Role:    "system",
+					Content: "You are concise.",
+					CacheControl: &domain.CacheControl{
+						Type: domain.CacheControlEphemeral,
+						TTL:  "1h",
+					},
+				},
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(res.Messages))
+		}
+		if res.Messages[0].CacheControl == nil {
+			t.Fatal("expected rendered cache control")
+		}
+		if res.Messages[0].CacheControl.Type != domain.CacheControlEphemeral {
+			t.Fatalf("unexpected cache control type: %q", res.Messages[0].CacheControl.Type)
+		}
+		if res.Messages[0].CacheControl.TTL != "1h" {
+			t.Fatalf("unexpected cache control ttl: %q", res.Messages[0].CacheControl.TTL)
+		}
+		if res.Messages[1].CacheControl != nil {
+			t.Fatalf("expected no cache control on second message, got %#v", res.Messages[1].CacheControl)
+		}
+	})
+
+	t.Run("rendered cache control does not alias source template", func(t *testing.T) {
+		source := &domain.CacheControl{Type: domain.CacheControlEphemeral, TTL: "1h"}
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "You are concise.", CacheControl: source},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.Messages[0].CacheControl == source {
+			t.Fatal("expected rendered cache control to be cloned")
+		}
+
+		res.Messages[0].CacheControl.TTL = ""
+		if source.TTL != "1h" {
+			t.Fatalf("source cache control was mutated, ttl=%q", source.TTL)
+		}
+	})
+
 	t.Run("accessing vars", func(t *testing.T) {
 		def := &domain.PromptDefinition{
 			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
@@ -95,6 +156,78 @@ func TestGoRenderer_Render(t *testing.T) {
 		}
 	})
 
+	t.Run("rendering session id from vars", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "  {{ .session_id }}  ",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, map[string]string{
+			"tone":       "concise",
+			"session_id": "agent-session-123",
+		})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.SessionID != "agent-session-123" {
+			t.Fatalf("unexpected session id: %q", res.SessionID)
+		}
+	})
+
+	t.Run("empty rendered session id is omitted", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "   ",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.SessionID != "" {
+			t.Fatalf("expected empty session id, got %q", res.SessionID)
+		}
+	})
+
+	t.Run("missing session id var fails rendering", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "{{ .session_id }}",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+	})
+
+	t.Run("too long rendered session id fails rendering", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			SessionID: "{{ .session_id }}",
+			Inputs:    []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "Speak in a {{.tone}} tone."},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, map[string]string{
+			"tone":       "concise",
+			"session_id": strings.Repeat("x", domain.SessionIDMaxLength+1),
+		})
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+	})
+
 	t.Run("inserting required input artifact", func(t *testing.T) {
 		def := &domain.PromptDefinition{
 			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},

internal/promptdef/filesystem_repository.go

@@ -5,7 +5,9 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 
@@ -24,11 +26,17 @@ type filesystemRepository struct {
 	dir string
 }
 
+type fsRepository struct {
+	fsys fs.FS
+	root string
+}
+
 type promptDefinitionFile struct {
 	ID             string                   `yaml:"id"`
 	Version        string                   `yaml:"version"`
 	DefaultProfile *string                  `yaml:"default_profile"`
 	Description    string                   `yaml:"description"`
+	SessionID      string                   `yaml:"session_id"`
 	Inputs         []promptInputFile        `yaml:"inputs"`
 	Messages       []promptMessageFile      `yaml:"messages"`
 	Output         promptOutputContractFile `yaml:"output"`
@@ -45,6 +53,12 @@ type promptMessageFile struct {
 	Role         string            `yaml:"role"`
 	Content      string            `yaml:"content"`
 	ContentFile  string            `yaml:"content_file"`
+	CacheControl *cacheControlFile `yaml:"cache_control"`
+}
+
+type cacheControlFile struct {
+	Type string `yaml:"type"`
+	TTL  string `yaml:"ttl"`
 }
 
 type promptOutputContractFile struct {
@@ -58,6 +72,10 @@ func NewFilesystemRepository(dir string) Repository {
 	return &filesystemRepository{dir: dir}
 }
 
+func NewFSRepository(fsys fs.FS, root string) Repository {
+	return &fsRepository{fsys: fsys, root: root}
+}
+
 func (r *filesystemRepository) GetPromptDefinition(ctx context.Context, id string, version string) (*domain.PromptDefinition, error) {
 	if strings.TrimSpace(id) == "" {
 		return nil, fmt.Errorf("%w: prompt id is required", ErrInvalidPromptDefinition)
@@ -125,6 +143,10 @@ func (r *filesystemRepository) GetPromptDefinition(ctx context.Context, id strin
 	return nil, ErrPromptDefinitionNotFound
 }
 
+func (r *fsRepository) GetPromptDefinition(ctx context.Context, id string, version string) (*domain.PromptDefinition, error) {
+	return loadPromptDefinition(ctx, r.fsys, r.root, id, version)
+}
+
 type promptDefinitionMatch struct {
 	def  *domain.PromptDefinition
 	path string
@@ -159,7 +181,152 @@ func promptDefinitionFileHasID(path string, id string) bool {
 	return strings.TrimSpace(raw.ID) == id
 }
 
+func loadPromptDefinition(ctx context.Context, fsys fs.FS, root string, id string, version string) (*domain.PromptDefinition, error) {
+	if strings.TrimSpace(id) == "" {
+		return nil, fmt.Errorf("%w: prompt id is required", ErrInvalidPromptDefinition)
+	}
+	if fsys == nil {
+		return nil, fmt.Errorf("failed to read prompt definition directory: filesystem is nil")
+	}
+
+	files, err := filecatalog.FindFSYAMLFiles(ctx, fsys, root)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read prompt definition directory: %w", err)
+	}
+	cleanRoot := filecatalog.CleanFSRoot(root)
+	rootInfo, err := fs.Stat(fsys, cleanRoot)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read prompt definition directory: %w", err)
+	}
+
+	var matches []promptDefinitionMatch
+	for _, fullPath := range files {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		relPath := filecatalog.DisplayPath(root, fullPath)
+		fileMatch := filecatalog.Stem(path.Base(fullPath)) == id
+		data, err := fs.ReadFile(fsys, fullPath)
+		if err != nil {
+			if fileMatch {
+				return nil, fmt.Errorf("%w: %s: failed to read prompt definition file: %v", ErrInvalidYAML, relPath, err)
+			}
+			continue
+		}
+
+		raw, err := decodePromptDefinition(data)
+		if err != nil {
+			if fileMatch || promptDefinitionDataHasID(data, id) {
+				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidYAML, relPath, err)
+			}
+			continue
+		}
+
+		def, err := normalizePromptDefinitionFromFS(raw, fsys, root, fullPath, rootInfo.IsDir())
+		if err != nil {
+			if fileMatch || strings.TrimSpace(raw.ID) == id {
+				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidPromptDefinition, relPath, err)
+			}
+			continue
+		}
+
+		if def.ID != id {
+			continue
+		}
+		if version != "" && def.Version != version {
+			continue
+		}
+		matches = append(matches, promptDefinitionMatch{
+			def:  def,
+			path: relPath,
+		})
+	}
+
+	if len(matches) > 1 {
+		paths := make([]string, 0, len(matches))
+		for _, match := range matches {
+			paths = append(paths, match.path)
+		}
+		if version != "" {
+			return nil, fmt.Errorf("%w: duplicate prompt definition id %q version %q found in: %s", ErrInvalidPromptDefinition, id, version, strings.Join(paths, ", "))
+		}
+		return nil, fmt.Errorf("%w: duplicate prompt definition id %q found in: %s", ErrInvalidPromptDefinition, id, strings.Join(paths, ", "))
+	}
+
+	if len(matches) == 1 {
+		return matches[0].def, nil
+	}
+
+	return nil, ErrPromptDefinitionNotFound
+}
+
+func decodePromptDefinition(data []byte) (*promptDefinitionFile, error) {
+	var raw promptDefinitionFile
+	decoder := yaml.NewDecoder(bytes.NewReader(data))
+	decoder.KnownFields(true)
+	if err := decoder.Decode(&raw); err != nil {
+		return nil, err
+	}
+	return &raw, nil
+}
+
+func promptDefinitionDataHasID(data []byte, id string) bool {
+	var raw struct {
+		ID string `yaml:"id"`
+	}
+	if err := yaml.NewDecoder(bytes.NewReader(data)).Decode(&raw); err != nil {
+		return false
+	}
+	return strings.TrimSpace(raw.ID) == id
+}
+
 func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*domain.PromptDefinition, error) {
+	promptDir := filepath.Dir(sourcePath)
+	return normalizePromptDefinitionWithContent(raw, func(contentFile string) (string, string, error) {
+		resolvedPath := strings.TrimSpace(contentFile)
+		if !filepath.IsAbs(resolvedPath) {
+			resolvedPath = filepath.Join(promptDir, resolvedPath)
+		}
+		resolvedPath = filepath.Clean(resolvedPath)
+
+		body, err := os.ReadFile(resolvedPath)
+		if err != nil {
+			return "", "", err
+		}
+		return string(body), resolvedPath, nil
+	})
+}
+
+func normalizePromptDefinitionFromFS(raw *promptDefinitionFile, fsys fs.FS, root string, sourcePath string, rootIsDir bool) (*domain.PromptDefinition, error) {
+	promptDir := path.Dir(sourcePath)
+	return normalizePromptDefinitionWithContent(raw, func(contentFile string) (string, string, error) {
+		var resolvedPath string
+		if rootIsDir {
+			var err error
+			resolvedPath, _, err = filecatalog.ResolveFSPath(root, promptDir, contentFile)
+			if err != nil {
+				return "", "", err
+			}
+		} else {
+			resolvedPath = strings.TrimSpace(contentFile)
+			if !path.IsAbs(resolvedPath) {
+				resolvedPath = path.Join(promptDir, resolvedPath)
+			}
+			resolvedPath = strings.TrimPrefix(path.Clean(resolvedPath), "/")
+		}
+
+		body, err := fs.ReadFile(fsys, resolvedPath)
+		if err != nil {
+			return "", "", err
+		}
+		return string(body), resolvedPath, nil
+	})
+}
+
+func normalizePromptDefinitionWithContent(raw *promptDefinitionFile, readContentFile func(string) (string, string, error)) (*domain.PromptDefinition, error) {
 	if raw == nil {
 		return nil, errors.New("prompt definition is nil")
 	}
@@ -199,7 +366,6 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 	}
 
 	templates := make([]domain.PromptMessageTemplate, 0, len(raw.Messages))
-	promptDir := filepath.Dir(sourcePath)
 	for i, msg := range raw.Messages {
 		role := strings.TrimSpace(msg.Role)
 		if role == "" {
@@ -212,20 +378,19 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 			return nil, fmt.Errorf("message %d (%s) must set exactly one of content or content_file", i, role)
 		}
 
+		cacheControl, err := normalizeCacheControl(msg.CacheControl)
+		if err != nil {
+			return nil, fmt.Errorf("message %d (%s) cache_control: %w", i, role, err)
+		}
+
 		templateContent := msg.Content
 		resolvedContentFile := ""
 		if hasContentFile {
-			resolvedPath := strings.TrimSpace(msg.ContentFile)
+			body, resolvedPath, err := readContentFile(msg.ContentFile)
-			if !filepath.IsAbs(resolvedPath) {
-				resolvedPath = filepath.Join(promptDir, resolvedPath)
-			}
-			resolvedPath = filepath.Clean(resolvedPath)
-
-			body, err := os.ReadFile(resolvedPath)
 			if err != nil {
 				return nil, fmt.Errorf("prompt %q message %d (%s): failed to read content_file %q: %w", id, i, role, msg.ContentFile, err)
 			}
-			templateContent = string(body)
+			templateContent = body
 			resolvedContentFile = resolvedPath
 		}
 
@@ -233,6 +398,7 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 			Role:         role,
 			Content:      templateContent,
 			ContentFile:  resolvedContentFile,
+			CacheControl: cacheControl,
 		})
 	}
 
@@ -262,6 +428,7 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 		Version:        version,
 		DefaultProfile: defaultProfile,
 		Description:    strings.TrimSpace(raw.Description),
+		SessionID:      strings.TrimSpace(raw.SessionID),
 		Inputs:         inputs,
 		Templates:      templates,
 		OutputFormat:   raw.Output.Format,
@@ -274,6 +441,30 @@ func normalizePromptDefinition(raw *promptDefinitionFile, sourcePath string) (*d
 	}, nil
 }
 
+func normalizeCacheControl(raw *cacheControlFile) (*domain.CacheControl, error) {
+	if raw == nil {
+		return nil, nil
+	}
+
+	cacheType := strings.TrimSpace(raw.Type)
+	if cacheType == "" {
+		return nil, errors.New("type is required")
+	}
+	if domain.CacheControlType(cacheType) != domain.CacheControlEphemeral {
+		return nil, fmt.Errorf("unsupported type %q", cacheType)
+	}
+
+	ttl := strings.TrimSpace(raw.TTL)
+	if ttl != "" && ttl != "1h" {
+		return nil, fmt.Errorf("unsupported ttl %q", ttl)
+	}
+
+	return &domain.CacheControl{
+		Type: domain.CacheControlType(cacheType),
+		TTL:  ttl,
+	}, nil
+}
+
 func isValidOutputFormat(f domain.OutputFormat) bool {
 	switch f {
 	case domain.FormatText, domain.FormatMarkdown, domain.FormatJSON:

internal/promptdef/repository_test.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"strings"
 	"testing"
+	"testing/fstest"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 )
@@ -68,6 +69,44 @@ func TestFilesystemRepository_GetPromptDefinition(t *testing.T) {
 		}
 	})
 
+	t.Run("valid cache control with ttl", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "valid-cache-control-ttl", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if len(p.Templates) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(p.Templates))
+		}
+		assertCacheControl(t, p.Templates[0].CacheControl, domain.CacheControlEphemeral, "1h")
+		if p.Templates[1].CacheControl != nil {
+			t.Fatalf("expected second message cache control to be nil, got %#v", p.Templates[1].CacheControl)
+		}
+	})
+
+	t.Run("valid cache control without ttl", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "valid-cache-control-without-ttl", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if len(p.Templates) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(p.Templates))
+		}
+		assertCacheControl(t, p.Templates[0].CacheControl, domain.CacheControlEphemeral, "")
+		if p.Templates[1].CacheControl != nil {
+			t.Fatalf("expected second message cache control to be nil, got %#v", p.Templates[1].CacheControl)
+		}
+	})
+
+	t.Run("valid session id template", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "valid-session-id", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.SessionID != "{{ .session_id }}" {
+			t.Fatalf("expected trimmed session_id template, got %q", p.SessionID)
+		}
+	})
+
 	t.Run("valid nested file-backed prompt resolves content file relative to nested YAML", func(t *testing.T) {
 		nestedDir := filepath.Join(tmpDir, "dnd", "recap")
 		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
@@ -258,6 +297,10 @@ output:
 		{name: "invalid validation mode", id: "invalid_validation_mode", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"invalid validation mode"}},
 		{name: "json_schema without schema_path", id: "json_schema_without_schema_path", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"schema_path"}},
 		{name: "unknown input field", id: "unknown_input_field", targetErr: ErrInvalidYAML, errSubstrs: []string{"field unknown_input_setting not found"}},
+		{name: "empty cache control type", id: "empty_cache_control_type", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"cache_control", "type is required"}},
+		{name: "unsupported cache control type", id: "unsupported_cache_control_type", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"cache_control", "unsupported type"}},
+		{name: "unsupported cache control ttl", id: "unsupported_cache_control_ttl", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"cache_control", "unsupported ttl"}},
+		{name: "unknown cache control field", id: "unknown_cache_control_field", targetErr: ErrInvalidYAML, errSubstrs: []string{"field unexpected not found"}},
 	}
 
 	for _, tc := range cases {
@@ -282,6 +325,173 @@ output:
 	})
 }
 
+func TestFSRepositoryGetPromptDefinition(t *testing.T) {
+	repo := NewFSRepository(fstest.MapFS{
+		"prompts/nested/prompt.yaml": &fstest.MapFile{Data: []byte(`
+id: fs-prompt
+version: "1.0.0"
+inputs:
+  - name: transcript
+    required: true
+messages:
+  - role: user
+    content_file: ./messages/user.tmpl
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)},
+		"prompts/nested/messages/user.tmpl": &fstest.MapFile{Data: []byte(`Summarize {{input "transcript"}}.`)},
+	}, "prompts")
+
+	got, err := repo.GetPromptDefinition(context.Background(), "fs-prompt", "")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if got.ID != "fs-prompt" {
+		t.Fatalf("unexpected prompt id: %q", got.ID)
+	}
+	if len(got.Templates) != 1 || !strings.Contains(got.Templates[0].Content, `{{input "transcript"}}`) {
+		t.Fatalf("expected content_file body to be loaded, got %+v", got.Templates)
+	}
+	if got.Templates[0].ContentFile != "prompts/nested/messages/user.tmpl" {
+		t.Fatalf("unexpected content file path: %q", got.Templates[0].ContentFile)
+	}
+}
+
+func TestFSRepositoryContentFileContainment(t *testing.T) {
+	t.Run("nested prompt can reference file inside root", func(t *testing.T) {
+		repo := NewFSRepository(fstest.MapFS{
+			"prompts/nested/prompt.yaml": &fstest.MapFile{Data: []byte(`
+id: fs-contained-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content_file: ../shared/user.tmpl
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)},
+			"prompts/shared/user.tmpl": &fstest.MapFile{Data: []byte(`Inside root.`)},
+		}, "prompts")
+
+		got, err := repo.GetPromptDefinition(context.Background(), "fs-contained-prompt", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if len(got.Templates) != 1 || got.Templates[0].Content != "Inside root." {
+			t.Fatalf("expected contained content file, got %+v", got.Templates)
+		}
+	})
+
+	tests := []struct {
+		name        string
+		contentFile string
+		wantErr     string
+	}{
+		{name: "parent escape rejected", contentFile: "../outside.tmpl", wantErr: "escapes source root"},
+		{name: "absolute path rejected", contentFile: "/outside.tmpl", wantErr: "must be relative"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			repo := NewFSRepository(fstest.MapFS{
+				"prompts/prompt.yaml": &fstest.MapFile{Data: []byte(`
+id: fs-escaped-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content_file: ` + tc.contentFile + `
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)},
+				"outside.tmpl": &fstest.MapFile{Data: []byte(`Outside root.`)},
+			}, "prompts")
+
+			_, err := repo.GetPromptDefinition(context.Background(), "fs-escaped-prompt", "")
+			if !errors.Is(err, ErrInvalidPromptDefinition) {
+				t.Fatalf("expected ErrInvalidPromptDefinition, got %v", err)
+			}
+			if !strings.Contains(err.Error(), tc.wantErr) {
+				t.Fatalf("expected error to contain %q, got %v", tc.wantErr, err)
+			}
+		})
+	}
+}
+
+func TestFSRepositoryRejectsDuplicatePromptIDs(t *testing.T) {
+	repo := NewFSRepository(fstest.MapFS{
+		"one.yaml": &fstest.MapFile{Data: []byte(`
+id: duplicate-fs-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content: First.
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0
+`)},
+		"nested/two.yaml": &fstest.MapFile{Data: []byte(`
+id: duplicate-fs-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content: Second.
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0
+`)},
+	}, ".")
+
+	_, err := repo.GetPromptDefinition(context.Background(), "duplicate-fs-prompt", "")
+	if !errors.Is(err, ErrInvalidPromptDefinition) {
+		t.Fatalf("expected ErrInvalidPromptDefinition, got %v", err)
+	}
+	if !strings.Contains(err.Error(), "one.yaml") || !strings.Contains(err.Error(), "nested/two.yaml") {
+		t.Fatalf("expected duplicate paths in error, got %v", err)
+	}
+}
+
+func TestFSRepositoryRejectsUnknownYAMLFields(t *testing.T) {
+	repo := NewFSRepository(fstest.MapFS{
+		"not_named_like_id.yaml": &fstest.MapFile{Data: []byte(`
+id: strict-fs-prompt
+version: "1.0.0"
+unknown: true
+messages:
+  - role: user
+    content: Invalid.
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0
+`)},
+	}, ".")
+
+	_, err := repo.GetPromptDefinition(context.Background(), "strict-fs-prompt", "")
+	if !errors.Is(err, ErrInvalidYAML) {
+		t.Fatalf("expected ErrInvalidYAML, got %v", err)
+	}
+}
+
+func assertCacheControl(t *testing.T, got *domain.CacheControl, wantType domain.CacheControlType, wantTTL string) {
+	t.Helper()
+	if got == nil {
+		t.Fatal("expected cache control, got nil")
+	}
+	if got.Type != wantType {
+		t.Fatalf("unexpected cache control type: got %q want %q", got.Type, wantType)
+	}
+	if got.TTL != wantTTL {
+		t.Fatalf("unexpected cache control ttl: got %q want %q", got.TTL, wantTTL)
+	}
+}
+
 func writePromptTestFile(t *testing.T, path string, content string) {
 	t.Helper()
 	if err := os.WriteFile(path, []byte(strings.TrimLeft(content, "\n")), 0o644); err != nil {

internal/promptdef/testdata/empty_cache_control_type.yaml

@@ -0,0 +1,10 @@
+id: empty-cache-control-type
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control: {}
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/unknown_cache_control_field.yaml

@@ -0,0 +1,12 @@
+id: unknown-cache-control-field
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control:
+      type: ephemeral
+      unexpected: true
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/unsupported_cache_control_ttl.yaml

@@ -0,0 +1,12 @@
+id: unsupported-cache-control-ttl
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control:
+      type: ephemeral
+      ttl: 5m
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/unsupported_cache_control_type.yaml

@@ -0,0 +1,11 @@
+id: unsupported-cache-control-type
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control:
+      type: persistent
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/valid_cache_control_ttl.yaml

@@ -0,0 +1,14 @@
+id: valid-cache-control-ttl
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control:
+      type: ephemeral
+      ttl: 1h
+  - role: user
+    content: "Summarize the input."
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/valid_cache_control_without_ttl.yaml

@@ -0,0 +1,13 @@
+id: valid-cache-control-without-ttl
+version: "1.0.0"
+messages:
+  - role: system
+    content: "Use cached instructions."
+    cache_control:
+      type: ephemeral
+  - role: user
+    content: "Summarize the input."
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/valid_session_id.yaml

@@ -0,0 +1,10 @@
+id: valid-session-id
+version: "1.0.0"
+session_id: "  {{ .session_id }}  "
+messages:
+  - role: user
+    content: Hello.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/usecase/runner.go

@@ -27,7 +27,9 @@ var (
 	ErrInvalidRequest   = errors.New("invalid run request")
 	ErrProfileRequired  = errors.New("profile selection is required")
 	ErrAPIKeyEnvMissing = errors.New("api_key_env points to an unset environment variable")
-	ErrProfileLoad      = errors.New("failed to load prompt definition")
+	ErrAPIKeyRequired   = errors.New("api key is required")
+	ErrPromptLoad       = errors.New("failed to load prompt definition")
+	ErrProfileLoad      = errors.New("failed to load execution profile")
 	ErrArtifactLoad     = errors.New("failed to load artifact")
 	ErrPromptRender     = errors.New("failed to render prompt")
 	ErrLLMGenerate      = errors.New("failed to generate output")
@@ -90,11 +92,15 @@ func (r *Runner) Run(ctx context.Context, req domain.RunRequest) (*domain.RunRes
 	}
 
 	genResp, err := r.llm.Generate(ctx, domain.GenerateRequest{
-		Prompt:           domain.RenderedPrompt{Messages: prepared.Messages},
+		Prompt:           domain.RenderedPrompt{SessionID: prepared.SessionID, Messages: prepared.Messages},
 		Target:           prepared.EffectiveModelParams,
+		TargetPresence:   prepared.TargetPresence,
 		StructuredOutput: prepared.StructuredOutput,
 	})
 	if err != nil {
+		if errors.Is(err, llm.ErrInvalidRequest) {
+			return nil, fmt.Errorf("%w: %w", ErrInvalidRequest, err)
+		}
 		return nil, fmt.Errorf("%w: %w", ErrLLMGenerate, err)
 	}
 
@@ -167,11 +173,11 @@ func (r *Runner) Prepare(ctx context.Context, req domain.RunRequest) (*domain.Pr
 
 	def, err := r.promptDefs.GetPromptDefinition(ctx, req.PromptID, req.PromptVersion)
 	if err != nil {
-		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, err)
+		return nil, fmt.Errorf("%w: %w", ErrPromptLoad, err)
 	}
 	promptDefinitionHash, err := hashPromptDefinition(def)
 	if err != nil {
-		return nil, fmt.Errorf("%w: failed to hash prompt definition: %v", ErrProfileLoad, err)
+		return nil, fmt.Errorf("%w: failed to hash prompt definition: %v", ErrPromptLoad, err)
 	}
 
 	selectedProfileID := strings.TrimSpace(req.ProfileID)
@@ -187,14 +193,18 @@ func (r *Runner) Prepare(ctx context.Context, req domain.RunRequest) (*domain.Pr
 		return nil, fmt.Errorf("%w: %w", ErrProfileLoad, err)
 	}
 
-	effectiveModel := resolveExecutionTarget(execProfile, req.Execution)
+	effectiveModel, targetPresence, err := resolveExecutionTarget(execProfile, req.Execution)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w", ErrInvalidRequest, err)
+	}
+	effectiveModel.APIKey = req.APIKey
 	if strings.TrimSpace(effectiveModel.Endpoint) == "" {
 		return nil, fmt.Errorf("%w: execution endpoint is required", ErrInvalidRequest)
 	}
 	if strings.TrimSpace(effectiveModel.Model) == "" {
 		return nil, fmt.Errorf("%w: execution model is required", ErrInvalidRequest)
 	}
-	if err := validateAPIKeyEnv(effectiveModel.APIKeyEnv); err != nil {
+	if err := validateAPIKey(effectiveModel.APIKeyEnv, effectiveModel.APIKey, effectiveModel.APIKeyRequired); err != nil {
 		return nil, fmt.Errorf("%w: %w", ErrInvalidRequest, err)
 	}
 
@@ -230,9 +240,11 @@ func (r *Runner) Prepare(ctx context.Context, req domain.RunRequest) (*domain.Pr
 		PromptHash:           promptDefinitionHash,
 		SelectedProfileID:    selectedProfileID,
 		EffectiveModelParams: effectiveModel,
+		TargetPresence:       targetPresence,
 		OutputContract:       effectiveContract,
 		StructuredOutput:     structuredOutput,
 		InputHashes:          inputHashes,
+		SessionID:            renderedPrompt.SessionID,
 		RenderedPromptHash:   hashRenderedPrompt(*renderedPrompt),
 		Messages:             renderedPrompt.Messages,
 		StartTime:            start,
@@ -353,28 +365,90 @@ func mergeExecutionTarget(base domain.ExecutionTarget, override domain.Execution
 	if strings.TrimSpace(override.APIKeyEnv) != "" {
 		out.APIKeyEnv = override.APIKeyEnv
 	}
-	if len(override.ExtraParams) > 0 {
+	if override.APIKeyRequired {
-		cp := make(map[string]string, len(override.ExtraParams))
+		out.APIKeyRequired = true
-		for k, v := range override.ExtraParams {
-			cp[k] = v
 	}
-		out.ExtraParams = cp
+	if len(override.ExtraParams) > 0 {
+		out.ExtraParams = copyExtraParams(override.ExtraParams)
 	}
 	return out
 }
 
-func resolveExecutionTarget(profileValue *domain.ExecutionProfile, override *domain.ExecutionTarget) domain.ExecutionTarget {
+func mergeExecutionTargetOverride(base domain.ExecutionTarget, override domain.ExecutionTargetOverride) (domain.ExecutionTarget, domain.ExecutionTargetPresence, error) {
+	out := base
+	var presence domain.ExecutionTargetPresence
+	if override.Endpoint != "" {
+		out.Endpoint = override.Endpoint
+	}
+	if override.Model != "" {
+		out.Model = override.Model
+	}
+	if override.Temperature != nil {
+		if *override.Temperature < 0 || *override.Temperature > 2 {
+			return domain.ExecutionTarget{}, domain.ExecutionTargetPresence{}, errors.New("temperature must be between 0 and 2")
+		}
+		out.Temperature = *override.Temperature
+		presence.Temperature = true
+	}
+	if override.MaxTokens != nil {
+		if *override.MaxTokens < 0 {
+			return domain.ExecutionTarget{}, domain.ExecutionTargetPresence{}, errors.New("max_tokens must be greater than or equal to 0")
+		}
+		out.MaxTokens = *override.MaxTokens
+		presence.MaxTokens = true
+	}
+	if override.TopP != nil {
+		if *override.TopP < 0 || *override.TopP > 1 {
+			return domain.ExecutionTarget{}, domain.ExecutionTargetPresence{}, errors.New("top_p must be between 0 and 1")
+		}
+		out.TopP = *override.TopP
+		presence.TopP = true
+	}
+	if override.TimeoutSeconds != nil {
+		if *override.TimeoutSeconds < 0 {
+			return domain.ExecutionTarget{}, domain.ExecutionTargetPresence{}, errors.New("timeout_seconds must be greater than or equal to 0")
+		}
+		out.TimeoutSeconds = *override.TimeoutSeconds
+		presence.TimeoutSeconds = true
+	}
+	if strings.TrimSpace(override.ServiceTier) != "" {
+		out.ServiceTier = override.ServiceTier
+	}
+	if strings.TrimSpace(override.ReasoningEffort) != "" {
+		out.ReasoningEffort = override.ReasoningEffort
+	}
+	if strings.TrimSpace(override.APIKeyEnv) != "" {
+		out.APIKeyEnv = override.APIKeyEnv
+	}
+	if len(override.ExtraParams) > 0 {
+		out.ExtraParams = copyExtraParams(override.ExtraParams)
+	}
+	return out, presence, nil
+}
+
+func resolveExecutionTarget(profileValue *domain.ExecutionProfile, override *domain.ExecutionTargetOverride) (domain.ExecutionTarget, domain.ExecutionTargetPresence, error) {
 	out := defaults.ExecutionTargetDefault()
 	out = mergeExecutionTarget(out, executionProfileToTarget(profileValue))
+	var presence domain.ExecutionTargetPresence
 	if override != nil {
-		out = mergeExecutionTarget(out, *override)
+		var err error
+		out, presence, err = mergeExecutionTargetOverride(out, *override)
+		if err != nil {
+			return domain.ExecutionTarget{}, domain.ExecutionTargetPresence{}, err
 		}
-	return out
+	}
+	return out, presence, nil
 }
 
-func validateAPIKeyEnv(apiKeyEnv string) error {
+func validateAPIKey(apiKeyEnv string, apiKey string, apiKeyRequired bool) error {
+	if strings.TrimSpace(apiKey) != "" {
+		return nil
+	}
 	envName := strings.TrimSpace(apiKeyEnv)
 	if envName == "" {
+		if apiKeyRequired {
+			return ErrAPIKeyRequired
+		}
 		return nil
 	}
 	if strings.TrimSpace(os.Getenv(envName)) == "" {
@@ -387,13 +461,6 @@ func executionProfileToTarget(p *domain.ExecutionProfile) domain.ExecutionTarget
 	if p == nil {
 		return domain.ExecutionTarget{}
 	}
-	cp := map[string]string(nil)
-	if len(p.ExtraParams) > 0 {
-		cp = make(map[string]string, len(p.ExtraParams))
-		for k, v := range p.ExtraParams {
-			cp[k] = v
-		}
-	}
 	return domain.ExecutionTarget{
 		Endpoint:        p.Endpoint,
 		Model:           p.Model,
@@ -404,10 +471,22 @@ func executionProfileToTarget(p *domain.ExecutionProfile) domain.ExecutionTarget
 		ServiceTier:     p.ServiceTier,
 		ReasoningEffort: p.ReasoningEffort,
 		APIKeyEnv:       p.APIKeyEnv,
-		ExtraParams:     cp,
+		APIKeyRequired:  p.APIKeyRequired,
+		ExtraParams:     copyExtraParams(p.ExtraParams),
 	}
 }
 
+func copyExtraParams(src map[string]any) map[string]any {
+	if len(src) == 0 {
+		return nil
+	}
+	cp := make(map[string]any, len(src))
+	for k, v := range src {
+		cp[k] = v
+	}
+	return cp
+}
+
 func resolveOutputContract(def *domain.PromptDefinition, override *domain.OutputContract) domain.OutputContract {
 	contract := def.Validation
 	if contract.Format == "" {
@@ -424,10 +503,23 @@ func resolveOutputContract(def *domain.PromptDefinition, override *domain.Output
 
 func hashRenderedPrompt(p domain.RenderedPrompt) string {
 	var b strings.Builder
+	if p.SessionID != "" {
+		b.WriteString("session_id=")
+		b.WriteString(p.SessionID)
+		b.WriteString("\n---\n")
+	}
 	for _, msg := range p.Messages {
 		b.WriteString(msg.Role)
 		b.WriteByte('\n')
 		b.WriteString(msg.Content)
+		if msg.CacheControl != nil {
+			b.WriteString("\ncache_control.type=")
+			b.WriteString(string(msg.CacheControl.Type))
+			if msg.CacheControl.TTL != "" {
+				b.WriteString("\ncache_control.ttl=")
+				b.WriteString(msg.CacheControl.TTL)
+			}
+		}
 		b.WriteString("\n---\n")
 	}
 	h := sha256.Sum256([]byte(b.String()))

internal/usecase/runner_test.go

@@ -14,6 +14,7 @@ import (
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/defaults"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/llm"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/prompt"
 	"gitea.maximumdirect.net/eric/scriptorium/internal/promptdef"
@@ -160,7 +161,7 @@ func TestRunnerPrepareWithExplicitProfileSelection(t *testing.T) {
 		"a://t": {Body: []byte("transcript"), Hash: hashString("transcript")},
 		"a://g": {Body: []byte("glossary"), Hash: hashString("glossary")},
 	}}
-	renderer := &fakeRenderer{rendered: &domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "system", Content: "sys"}, {Role: "user", Content: "usr"}}}}
+	renderer := &fakeRenderer{rendered: &domain.RenderedPrompt{SessionID: "session-123", Messages: []domain.RenderedMessage{{Role: "system", Content: "sys"}, {Role: "user", Content: "usr"}}}}
 	llmClient := &fakeLLM{forbid: true}
 
 	runner := NewRunner(promptRepo, execRepo, reader, renderer, llmClient, nil)
@@ -172,7 +173,7 @@ func TestRunnerPrepareWithExplicitProfileSelection(t *testing.T) {
 			"transcript": {Type: domain.ArtifactRefFile, URI: "a://t"},
 			"glossary":   {Type: domain.ArtifactRefFile, URI: "a://g"},
 		},
-		Execution: &domain.ExecutionTarget{Endpoint: "http://override/v1", Model: "m", Temperature: 0.3, TimeoutSeconds: 90},
+		Execution: &domain.ExecutionTargetOverride{Endpoint: "http://override/v1", Model: "m", Temperature: float64Ptr(0.3), TimeoutSeconds: intPtr(90)},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -198,6 +199,9 @@ func TestRunnerPrepareWithExplicitProfileSelection(t *testing.T) {
 	if len(prepared.Messages) != 2 {
 		t.Fatalf("expected two messages, got %d", len(prepared.Messages))
 	}
+	if prepared.SessionID != "session-123" {
+		t.Fatalf("expected prepared session id, got %q", prepared.SessionID)
+	}
 	if llmClient.calls != 0 {
 		t.Fatalf("prepare should not call llm, calls=%d", llmClient.calls)
 	}
@@ -249,6 +253,17 @@ func TestRunnerPrepareSelectedProfileDoesNotExistFails(t *testing.T) {
 	}
 }
 
+func TestRunnerPreparePromptLoadFailure(t *testing.T) {
+	runner := NewRunner(&fakePromptRepo{err: errors.New("boom")}, &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}}, defaultArtifactReader(), defaultRenderer(), &fakeLLM{}, nil)
+	_, err := runner.Prepare(context.Background(), domain.RunRequest{PromptID: "p"})
+	if !errors.Is(err, ErrPromptLoad) {
+		t.Fatalf("expected ErrPromptLoad, got %v", err)
+	}
+	if errors.Is(err, ErrProfileLoad) {
+		t.Fatalf("did not expect ErrProfileLoad, got %v", err)
+	}
+}
+
 func TestRunnerPrepareRuntimeOverrideBeatsSelectedProfileValue(t *testing.T) {
 	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
 	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
@@ -269,11 +284,11 @@ func TestRunnerPrepareRuntimeOverrideBeatsSelectedProfileValue(t *testing.T) {
 		PromptID:  "p",
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
-		Execution: &domain.ExecutionTarget{
+		Execution: &domain.ExecutionTargetOverride{
 			Endpoint:       "http://override/v1",
 			Model:          "override-model",
-			Temperature:    0.7,
+			Temperature:    float64Ptr(0.7),
-			TimeoutSeconds: 30,
+			TimeoutSeconds: intPtr(30),
 			ServiceTier:    "flex",
 		},
 	})
@@ -291,6 +306,143 @@ func TestRunnerPrepareRuntimeOverrideBeatsSelectedProfileValue(t *testing.T) {
 	}
 }
 
+func TestRunnerPrepareRequestNumericOverridePresence(t *testing.T) {
+	tests := []struct {
+		name            string
+		override        *domain.ExecutionTargetOverride
+		wantTemperature float64
+		wantMaxTokens   int
+		wantTopP        float64
+		wantTimeoutSecs int
+		wantPresence    domain.ExecutionTargetPresence
+	}{
+		{
+			name:            "omitted preserves profile values",
+			override:        &domain.ExecutionTargetOverride{},
+			wantTemperature: 0.7,
+			wantMaxTokens:   321,
+			wantTopP:        0.8,
+			wantTimeoutSecs: 45,
+		},
+		{
+			name:            "explicit zero temperature",
+			override:        &domain.ExecutionTargetOverride{Temperature: float64Ptr(0)},
+			wantTemperature: 0,
+			wantMaxTokens:   321,
+			wantTopP:        0.8,
+			wantTimeoutSecs: 45,
+			wantPresence:    domain.ExecutionTargetPresence{Temperature: true},
+		},
+		{
+			name:            "explicit zero max tokens",
+			override:        &domain.ExecutionTargetOverride{MaxTokens: intPtr(0)},
+			wantTemperature: 0.7,
+			wantMaxTokens:   0,
+			wantTopP:        0.8,
+			wantTimeoutSecs: 45,
+			wantPresence:    domain.ExecutionTargetPresence{MaxTokens: true},
+		},
+		{
+			name:            "explicit zero top p",
+			override:        &domain.ExecutionTargetOverride{TopP: float64Ptr(0)},
+			wantTemperature: 0.7,
+			wantMaxTokens:   321,
+			wantTopP:        0,
+			wantTimeoutSecs: 45,
+			wantPresence:    domain.ExecutionTargetPresence{TopP: true},
+		},
+		{
+			name:            "explicit zero timeout",
+			override:        &domain.ExecutionTargetOverride{TimeoutSeconds: intPtr(0)},
+			wantTemperature: 0.7,
+			wantMaxTokens:   321,
+			wantTopP:        0.8,
+			wantTimeoutSecs: 0,
+			wantPresence:    domain.ExecutionTargetPresence{TimeoutSeconds: true},
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			runner := NewRunner(
+				&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
+				&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
+					"exec": {
+						ID:             "exec",
+						Endpoint:       "http://profile/v1",
+						Model:          "profile-model",
+						Temperature:    0.7,
+						MaxTokens:      321,
+						TopP:           0.8,
+						TimeoutSeconds: 45,
+					},
+				}},
+				defaultArtifactReader(),
+				defaultRenderer(),
+				&fakeLLM{forbid: true},
+				nil,
+			)
+
+			prepared, err := runner.Prepare(context.Background(), domain.RunRequest{
+				PromptID:  "p",
+				ProfileID: "exec",
+				Inputs:    singleInputRef(),
+				Execution: tc.override,
+			})
+			if err != nil {
+				t.Fatalf("expected no error, got %v", err)
+			}
+			got := prepared.EffectiveModelParams
+			if got.Temperature != tc.wantTemperature ||
+				got.MaxTokens != tc.wantMaxTokens ||
+				got.TopP != tc.wantTopP ||
+				got.TimeoutSeconds != tc.wantTimeoutSecs {
+				t.Fatalf("unexpected effective numeric settings: %+v", got)
+			}
+			if prepared.TargetPresence != tc.wantPresence {
+				t.Fatalf("unexpected target presence: got %+v want %+v", prepared.TargetPresence, tc.wantPresence)
+			}
+		})
+	}
+}
+
+func TestRunnerPrepareInvalidRequestNumericOverridesFail(t *testing.T) {
+	tests := []struct {
+		name     string
+		override *domain.ExecutionTargetOverride
+	}{
+		{name: "temperature below range", override: &domain.ExecutionTargetOverride{Temperature: float64Ptr(-0.1)}},
+		{name: "temperature above range", override: &domain.ExecutionTargetOverride{Temperature: float64Ptr(2.1)}},
+		{name: "max tokens below range", override: &domain.ExecutionTargetOverride{MaxTokens: intPtr(-1)}},
+		{name: "top p below range", override: &domain.ExecutionTargetOverride{TopP: float64Ptr(-0.1)}},
+		{name: "top p above range", override: &domain.ExecutionTargetOverride{TopP: float64Ptr(1.1)}},
+		{name: "timeout below range", override: &domain.ExecutionTargetOverride{TimeoutSeconds: intPtr(-1)}},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			runner := NewRunner(
+				&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
+				&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
+				defaultArtifactReader(),
+				defaultRenderer(),
+				&fakeLLM{forbid: true},
+				nil,
+			)
+
+			_, err := runner.Prepare(context.Background(), domain.RunRequest{
+				PromptID:  "p",
+				ProfileID: "exec",
+				Inputs:    singleInputRef(),
+				Execution: tc.override,
+			})
+			if !errors.Is(err, ErrInvalidRequest) {
+				t.Fatalf("expected ErrInvalidRequest, got %v", err)
+			}
+		})
+	}
+}
+
 func TestRunnerPrepareSelectedProfileBeatsBuiltInDefault(t *testing.T) {
 	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
 	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
@@ -577,6 +729,100 @@ func TestDeriveStructuredSchemaName(t *testing.T) {
 	}
 }
 
+func TestHashRenderedPromptIncludesCacheControlWhenPresent(t *testing.T) {
+	uncached := domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+		{Role: "system", Content: "sys"},
+		{Role: "user", Content: "usr"},
+	}}
+	wantLegacyHash := hashString("system\nsys\n---\nuser\nusr\n---\n")
+	if got := hashRenderedPrompt(uncached); got != wantLegacyHash {
+		t.Fatalf("expected no-cache hash to preserve legacy input, got %q want %q", got, wantLegacyHash)
+	}
+
+	withCache := domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "sys",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+				TTL:  "1h",
+			},
+		},
+		{Role: "user", Content: "usr"},
+	}}
+	alsoWithCache := domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "sys",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+				TTL:  "1h",
+			},
+		},
+		{Role: "user", Content: "usr"},
+	}}
+	withoutTTL := domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+		{
+			Role:    "system",
+			Content: "sys",
+			CacheControl: &domain.CacheControl{
+				Type: domain.CacheControlEphemeral,
+			},
+		},
+		{Role: "user", Content: "usr"},
+	}}
+
+	cachedHash := hashRenderedPrompt(withCache)
+	if cachedHash == hashRenderedPrompt(uncached) {
+		t.Fatal("expected cache control to change rendered prompt hash")
+	}
+	if cachedHash != hashRenderedPrompt(alsoWithCache) {
+		t.Fatal("expected identical cache control metadata to produce stable hash")
+	}
+	if cachedHash == hashRenderedPrompt(withoutTTL) {
+		t.Fatal("expected ttl changes to affect rendered prompt hash")
+	}
+}
+
+func TestHashRenderedPromptIncludesSessionIDWhenPresent(t *testing.T) {
+	withoutSession := domain.RenderedPrompt{Messages: []domain.RenderedMessage{
+		{Role: "system", Content: "sys"},
+		{Role: "user", Content: "usr"},
+	}}
+	withSession := domain.RenderedPrompt{
+		SessionID: "session-123",
+		Messages: []domain.RenderedMessage{
+			{Role: "system", Content: "sys"},
+			{Role: "user", Content: "usr"},
+		},
+	}
+	alsoWithSession := domain.RenderedPrompt{
+		SessionID: "session-123",
+		Messages: []domain.RenderedMessage{
+			{Role: "system", Content: "sys"},
+			{Role: "user", Content: "usr"},
+		},
+	}
+	otherSession := domain.RenderedPrompt{
+		SessionID: "session-456",
+		Messages: []domain.RenderedMessage{
+			{Role: "system", Content: "sys"},
+			{Role: "user", Content: "usr"},
+		},
+	}
+
+	sessionHash := hashRenderedPrompt(withSession)
+	if sessionHash == hashRenderedPrompt(withoutSession) {
+		t.Fatal("expected session_id to change rendered prompt hash")
+	}
+	if sessionHash != hashRenderedPrompt(alsoWithSession) {
+		t.Fatal("expected identical session_id to produce stable hash")
+	}
+	if sessionHash == hashRenderedPrompt(otherSession) {
+		t.Fatal("expected session_id value changes to affect rendered prompt hash")
+	}
+}
+
 func TestRunnerRunSuccessful(t *testing.T) {
 	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatMarkdown, domain.ValidationBasic, 0)}
 	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}}
@@ -584,7 +830,7 @@ func TestRunnerRunSuccessful(t *testing.T) {
 		"a://t": {Body: []byte("transcript"), Hash: hashString("transcript")},
 		"a://g": {Body: []byte("glossary"), Hash: hashString("glossary")},
 	}}
-	renderer := &fakeRenderer{rendered: &domain.RenderedPrompt{Messages: []domain.RenderedMessage{{Role: "system", Content: "sys"}, {Role: "user", Content: "usr"}}}}
+	renderer := &fakeRenderer{rendered: &domain.RenderedPrompt{SessionID: "session-123", Messages: []domain.RenderedMessage{{Role: "system", Content: "sys"}, {Role: "user", Content: "usr"}}}}
 	llmClient := &fakeLLM{resp: &domain.GenerateResponse{Content: "# recap", Usage: domain.TokenUsage{TotalTokens: 7}}}
 
 	runner := NewRunner(promptRepo, execRepo, reader, renderer, llmClient, nil)
@@ -596,7 +842,7 @@ func TestRunnerRunSuccessful(t *testing.T) {
 			"transcript": {Type: domain.ArtifactRefFile, URI: "a://t"},
 			"glossary":   {Type: domain.ArtifactRefFile, URI: "a://g"},
 		},
-		Execution: &domain.ExecutionTarget{Endpoint: "http://override/v1", Model: "m", Temperature: 0.3, TimeoutSeconds: 90},
+		Execution: &domain.ExecutionTargetOverride{Endpoint: "http://override/v1", Model: "m", Temperature: float64Ptr(0.3), TimeoutSeconds: intPtr(90)},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -631,6 +877,48 @@ func TestRunnerRunSuccessful(t *testing.T) {
 	if llmClient.lastReq.Target.TimeoutSeconds != 90 {
 		t.Fatalf("expected timeout propagation, got %d", llmClient.lastReq.Target.TimeoutSeconds)
 	}
+	if !llmClient.lastReq.TargetPresence.Temperature || !llmClient.lastReq.TargetPresence.TimeoutSeconds {
+		t.Fatalf("expected numeric override presence to be sent to llm, got %+v", llmClient.lastReq.TargetPresence)
+	}
+	if llmClient.lastReq.Prompt.SessionID != "session-123" {
+		t.Fatalf("expected session id to be sent to llm, got %q", llmClient.lastReq.Prompt.SessionID)
+	}
+}
+
+func TestRunnerRunPassesExtraParamsToGenerateRequestTarget(t *testing.T) {
+	extraParams := map[string]any{
+		"string_value":  "enabled",
+		"number_value":  42,
+		"boolean_value": true,
+		"object_value":  map[string]any{"nested": "value"},
+		"array_value":   []any{"first", 3, false},
+	}
+	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
+	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
+		"exec": {
+			ID:          "exec",
+			Endpoint:    "http://profile/v1",
+			Model:       "profile-model",
+			ExtraParams: extraParams,
+		},
+	}}
+	llmClient := &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}
+	runner := NewRunner(promptRepo, execRepo, defaultArtifactReader(), defaultRenderer(), llmClient, nil)
+
+	res, err := runner.Run(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		Inputs:    singleInputRef(),
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if !reflect.DeepEqual(res.EffectiveModelParams.ExtraParams, extraParams) {
+		t.Fatalf("expected run result extra_params to match profile values, got %#v", res.EffectiveModelParams.ExtraParams)
+	}
+	if !reflect.DeepEqual(llmClient.lastReq.Target.ExtraParams, extraParams) {
+		t.Fatalf("expected generate request extra_params to match profile values, got %#v", llmClient.lastReq.Target.ExtraParams)
+	}
 }
 
 func TestRunnerRunAndPrepareResolveSameProfileAndEffectiveSettings(t *testing.T) {
@@ -649,7 +937,7 @@ func TestRunnerRunAndPrepareResolveSameProfileAndEffectiveSettings(t *testing.T)
 		Inputs: map[string]domain.ArtifactRef{
 			"transcript": {Type: domain.ArtifactRefFile, URI: "a://t"},
 		},
-		Execution: &domain.ExecutionTarget{Endpoint: "http://override/v1", Model: "m", Temperature: 0.3, TimeoutSeconds: 90},
+		Execution: &domain.ExecutionTargetOverride{Endpoint: "http://override/v1", Model: "m", Temperature: float64Ptr(0.3), TimeoutSeconds: intPtr(90)},
 	}
 
 	prepared, err := runner.Prepare(context.Background(), req)
@@ -777,11 +1065,11 @@ func TestRunnerRunExplicitRuntimeOverrideBeatsSelectedProfileValue(t *testing.T)
 		PromptID:  "p",
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
-		Execution: &domain.ExecutionTarget{
+		Execution: &domain.ExecutionTargetOverride{
 			Endpoint:       "http://override/v1",
 			Model:          "override-model",
-			Temperature:    0.7,
+			Temperature:    float64Ptr(0.7),
-			TimeoutSeconds: 30,
+			TimeoutSeconds: intPtr(30),
 			ServiceTier:    "flex",
 		},
 	})
@@ -902,6 +1190,75 @@ func TestRunnerRunAPIKeyEnvMissingEnvironmentValueFailsClearly(t *testing.T) {
 	}
 }
 
+func TestRunnerRunDirectAPIKeyBypassesMissingEnvAndReachesLLM(t *testing.T) {
+	const directKey = "direct-runner-key"
+	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
+	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
+		"exec": {ID: "exec", Endpoint: "http://profile/v1", Model: "profile-model", APIKeyEnv: "SCRIPTORIUM_MISSING_KEY"},
+	}}
+	llmClient := &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}
+	runner := NewRunner(promptRepo, execRepo, defaultArtifactReader(), defaultRenderer(), llmClient, nil)
+
+	_, err := runner.Run(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		APIKey:    directKey,
+		Inputs:    singleInputRef(),
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if llmClient.lastReq.Target.APIKey != directKey {
+		t.Fatalf("expected direct API key to reach LLM request")
+	}
+	if llmClient.lastReq.Target.APIKeyEnv != "SCRIPTORIUM_MISSING_KEY" {
+		t.Fatalf("expected api_key_env name to remain on target, got %q", llmClient.lastReq.Target.APIKeyEnv)
+	}
+}
+
+func TestRunnerPrepareAPIKeyRequiredFailsWithoutDirectKey(t *testing.T) {
+	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
+	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
+		"exec": {ID: "exec", Endpoint: "http://profile/v1", Model: "profile-model", APIKeyRequired: true},
+	}}
+	runner := NewRunner(promptRepo, execRepo, defaultArtifactReader(), defaultRenderer(), &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}, nil)
+
+	_, err := runner.Prepare(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		Inputs:    singleInputRef(),
+	})
+	if !errors.Is(err, ErrAPIKeyRequired) {
+		t.Fatalf("expected ErrAPIKeyRequired, got %v", err)
+	}
+}
+
+func TestRunnerRunAPIKeyRequiredSucceedsWithDirectKey(t *testing.T) {
+	const directKey = "direct-required-key"
+	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
+	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
+		"exec": {ID: "exec", Endpoint: "http://profile/v1", Model: "profile-model", APIKeyRequired: true},
+	}}
+	llmClient := &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}
+	runner := NewRunner(promptRepo, execRepo, defaultArtifactReader(), defaultRenderer(), llmClient, nil)
+
+	_, err := runner.Run(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		APIKey:    directKey,
+		Inputs:    singleInputRef(),
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if llmClient.lastReq.Target.APIKey != directKey {
+		t.Fatalf("expected direct API key to reach LLM request")
+	}
+	if !llmClient.lastReq.Target.APIKeyRequired {
+		t.Fatalf("expected APIKeyRequired to be carried to target")
+	}
+}
+
 func TestRunnerRunRuntimeAPIKeyEnvOverrideWorks(t *testing.T) {
 	const envName = "SCRIPTORIUM_RUNTIME_API_KEY"
 	t.Setenv(envName, "runtime-secret")
@@ -916,7 +1273,7 @@ func TestRunnerRunRuntimeAPIKeyEnvOverrideWorks(t *testing.T) {
 		PromptID:  "p",
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
-		Execution: &domain.ExecutionTarget{APIKeyEnv: envName},
+		Execution: &domain.ExecutionTargetOverride{APIKeyEnv: envName},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -941,7 +1298,7 @@ func TestRunnerRunRuntimeAPIKeyEnvOverrideBeatsProfile(t *testing.T) {
 		PromptID:  "p",
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
-		Execution: &domain.ExecutionTarget{APIKeyEnv: runtimeEnv},
+		Execution: &domain.ExecutionTargetOverride{APIKeyEnv: runtimeEnv},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -977,8 +1334,11 @@ func TestRunnerRunAPIKeyValueNotPresentInMetadata(t *testing.T) {
 func TestRunnerRunPromptLoadFailure(t *testing.T) {
 	runner := NewRunner(&fakePromptRepo{err: errors.New("boom")}, &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}}, defaultArtifactReader(), defaultRenderer(), &fakeLLM{}, nil)
 	_, err := runner.Run(context.Background(), domain.RunRequest{PromptID: "p"})
-	if !errors.Is(err, ErrProfileLoad) {
+	if !errors.Is(err, ErrPromptLoad) {
-		t.Fatalf("expected ErrProfileLoad, got %v", err)
+		t.Fatalf("expected ErrPromptLoad, got %v", err)
+	}
+	if errors.Is(err, ErrProfileLoad) {
+		t.Fatalf("did not expect ErrProfileLoad, got %v", err)
 	}
 }
 
@@ -1040,6 +1400,28 @@ func TestRunnerRunLLMFailure(t *testing.T) {
 	}
 }
 
+func TestRunnerRunLLMInvalidRequestMapsToUsecaseInvalidRequest(t *testing.T) {
+	runner := NewRunner(
+		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
+		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
+		defaultArtifactReader(),
+		defaultRenderer(),
+		&fakeLLM{err: llm.ErrInvalidRequest},
+		nil,
+	)
+	_, err := runner.Run(context.Background(), domain.RunRequest{
+		PromptID:  "p",
+		ProfileID: "exec",
+		Inputs:    singleInputRef(),
+	})
+	if !errors.Is(err, ErrInvalidRequest) {
+		t.Fatalf("expected ErrInvalidRequest, got %v", err)
+	}
+	if errors.Is(err, ErrLLMGenerate) {
+		t.Fatalf("did not expect ErrLLMGenerate, got %v", err)
+	}
+}
+
 func TestRunnerRunValidationStillWorks(t *testing.T) {
 	validator := &fakeValidator{result: domain.ValidationResult{Status: domain.ValidationFailed, Mode: domain.ValidationBasic, Errors: []string{"bad"}, IsValid: false}}
 	runner := NewRunner(
@@ -1082,7 +1464,7 @@ func TestRunnerRunStructuredRepairRemainsBoundedAndUsesEffectiveModelSettings(t
 		PromptID:  "p",
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
-		Execution: &domain.ExecutionTarget{Endpoint: "http://override/v1", Model: "override-model", TimeoutSeconds: 22},
+		Execution: &domain.ExecutionTargetOverride{Endpoint: "http://override/v1", Model: "override-model", TimeoutSeconds: intPtr(22)},
 	})
 	if err != nil {
 		t.Fatalf("expected no error, got %v", err)
@@ -1169,7 +1551,8 @@ func TestExecutionProfileToTargetPopulatesAllFieldsAndCopiesExtraParams(t *testi
 		ServiceTier:     "priority",
 		ReasoningEffort: "medium",
 		APIKeyEnv:       "SCRIPTORIUM_API_KEY",
-		ExtraParams: map[string]string{
+		APIKeyRequired:  true,
+		ExtraParams: map[string]any{
 			"provider_option": "on",
 		},
 	}
@@ -1183,7 +1566,8 @@ func TestExecutionProfileToTargetPopulatesAllFieldsAndCopiesExtraParams(t *testi
 		target.TimeoutSeconds != src.TimeoutSeconds ||
 		target.ServiceTier != src.ServiceTier ||
 		target.ReasoningEffort != src.ReasoningEffort ||
-		target.APIKeyEnv != src.APIKeyEnv {
+		target.APIKeyEnv != src.APIKeyEnv ||
+		target.APIKeyRequired != src.APIKeyRequired {
 		t.Fatalf("expected all profile fields to populate target, got %+v", target)
 	}
 	if !reflect.DeepEqual(target.ExtraParams, src.ExtraParams) {
@@ -1208,12 +1592,19 @@ func TestResolveExecutionTargetProfileValuesPopulateAllSupportedFields(t *testin
 		ServiceTier:     "priority",
 		ReasoningEffort: "low",
 		APIKeyEnv:       "PROFILE_KEY",
-		ExtraParams: map[string]string{
+		APIKeyRequired:  true,
+		ExtraParams: map[string]any{
 			"profile_option": "enabled",
 		},
 	}
 
-	target := resolveExecutionTarget(profileValue, nil)
+	target, presence, err := resolveExecutionTarget(profileValue, nil)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if presence != (domain.ExecutionTargetPresence{}) {
+		t.Fatalf("expected no request override presence, got %+v", presence)
+	}
 	if target.Endpoint != profileValue.Endpoint ||
 		target.Model != profileValue.Model ||
 		target.Temperature != profileValue.Temperature ||
@@ -1222,7 +1613,8 @@ func TestResolveExecutionTargetProfileValuesPopulateAllSupportedFields(t *testin
 		target.TimeoutSeconds != profileValue.TimeoutSeconds ||
 		target.ServiceTier != profileValue.ServiceTier ||
 		target.ReasoningEffort != profileValue.ReasoningEffort ||
-		target.APIKeyEnv != profileValue.APIKeyEnv {
+		target.APIKeyEnv != profileValue.APIKeyEnv ||
+		target.APIKeyRequired != profileValue.APIKeyRequired {
 		t.Fatalf("expected profile values to populate target, got %+v", target)
 	}
 	if !reflect.DeepEqual(target.ExtraParams, profileValue.ExtraParams) {
@@ -1242,32 +1634,38 @@ func TestResolveExecutionTargetRuntimeOverridesBeatProfileForAllOverrideableFiel
 		ServiceTier:     "priority",
 		ReasoningEffort: "medium",
 		APIKeyEnv:       "PROFILE_KEY",
-		ExtraParams: map[string]string{
+		ExtraParams: map[string]any{
 			"profile_only": "yes",
 		},
 	}
-	override := &domain.ExecutionTarget{
+	override := &domain.ExecutionTargetOverride{
 		Endpoint:        "http://override/v1",
 		Model:           "override-model",
-		Temperature:     0.9,
+		Temperature:     float64Ptr(0.9),
-		MaxTokens:       111,
+		MaxTokens:       intPtr(111),
-		TopP:            0.5,
+		TopP:            float64Ptr(0.5),
-		TimeoutSeconds:  30,
+		TimeoutSeconds:  intPtr(30),
 		ServiceTier:     "flex",
 		ReasoningEffort: "high",
 		APIKeyEnv:       "RUNTIME_KEY",
-		ExtraParams: map[string]string{
+		ExtraParams: map[string]any{
 			"runtime_only": "yes",
 		},
 	}
 
-	target := resolveExecutionTarget(profileValue, override)
+	target, presence, err := resolveExecutionTarget(profileValue, override)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if presence != (domain.ExecutionTargetPresence{Temperature: true, MaxTokens: true, TopP: true, TimeoutSeconds: true}) {
+		t.Fatalf("unexpected override presence: %+v", presence)
+	}
 	if target.Endpoint != override.Endpoint ||
 		target.Model != override.Model ||
-		target.Temperature != override.Temperature ||
+		target.Temperature != *override.Temperature ||
-		target.MaxTokens != override.MaxTokens ||
+		target.MaxTokens != *override.MaxTokens ||
-		target.TopP != override.TopP ||
+		target.TopP != *override.TopP ||
-		target.TimeoutSeconds != override.TimeoutSeconds ||
+		target.TimeoutSeconds != *override.TimeoutSeconds ||
 		target.ServiceTier != override.ServiceTier ||
 		target.ReasoningEffort != override.ReasoningEffort ||
 		target.APIKeyEnv != override.APIKeyEnv {
@@ -1311,12 +1709,12 @@ func TestMergeExecutionTargetEmptyStringOverridesDoNotErase(t *testing.T) {
 
 func TestMergeExecutionTargetEmptyExtraParamsDoesNotErase(t *testing.T) {
 	base := domain.ExecutionTarget{
-		ExtraParams: map[string]string{
+		ExtraParams: map[string]any{
 			"keep": "value",
 		},
 	}
 	override := domain.ExecutionTarget{
-		ExtraParams: map[string]string{},
+		ExtraParams: map[string]any{},
 	}
 
 	merged := mergeExecutionTarget(base, override)
@@ -1392,6 +1790,14 @@ func singleInputRef() map[string]domain.ArtifactRef {
 	return map[string]domain.ArtifactRef{"transcript": {Type: domain.ArtifactRefFile, URI: "a://ok"}}
 }
 
+func float64Ptr(v float64) *float64 {
+	return &v
+}
+
+func intPtr(v int) *int {
+	return &v
+}
+
 func newMinimalRunner(promptRepo *fakePromptRepo, execRepo *fakeExecutionProfileRepo) *Runner {
 	return NewRunner(
 		promptRepo,

internal/validate/standard_validator.go

@@ -5,11 +5,14 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/filecatalog"
 	"github.com/santhosh-tekuri/jsonschema/v6"
 )
 
@@ -18,11 +21,30 @@ type StandardValidator struct {
 	schemaBaseDir string
 }
 
+type FSValidator struct {
+	fsys fs.FS
+	root string
+}
+
 func NewStandardValidator(schemaBaseDir string) Validator {
 	return &StandardValidator{schemaBaseDir: schemaBaseDir}
 }
 
+func NewFSValidator(fsys fs.FS, root string) Validator {
+	return &FSValidator{fsys: fsys, root: root}
+}
+
 func (v *StandardValidator) Validate(ctx context.Context, artifact *domain.Artifact, contract domain.OutputContract) (domain.ValidationResult, error) {
+	return validateArtifact(ctx, artifact, contract, v.validateJSONSchema)
+}
+
+func (v *FSValidator) Validate(ctx context.Context, artifact *domain.Artifact, contract domain.OutputContract) (domain.ValidationResult, error) {
+	return validateArtifact(ctx, artifact, contract, v.validateJSONSchema)
+}
+
+type schemaValidatorFunc func(instance any, schemaPath string) ([]string, error)
+
+func validateArtifact(ctx context.Context, artifact *domain.Artifact, contract domain.OutputContract, validateSchema schemaValidatorFunc) (domain.ValidationResult, error) {
 	select {
 	case <-ctx.Done():
 		return domain.ValidationResult{}, ctx.Err()
@@ -74,21 +96,14 @@ func (v *StandardValidator) Validate(ctx context.Context, artifact *domain.Artif
 			return res, nil
 		}
 
-		schemaPath, err := v.resolveSchemaPath(contract.SchemaPath)
+		validationErrors, err := validateSchema(instance, contract.SchemaPath)
 		if err != nil {
 			return domain.ValidationResult{}, err
 		}
-
+		if len(validationErrors) > 0 {
-		compiler := jsonschema.NewCompiler()
-		schema, err := compiler.Compile(schemaPath)
-		if err != nil {
-			return domain.ValidationResult{}, fmt.Errorf("failed to compile JSON schema %q: %w", schemaPath, err)
-		}
-
-		if err := schema.Validate(instance); err != nil {
 			res.Status = domain.ValidationFailed
 			res.IsValid = false
-			res.Errors = []string{fmt.Sprintf("json schema validation failed: %v", err)}
+			res.Errors = validationErrors
 			return res, nil
 		}
 
@@ -100,6 +115,46 @@ func (v *StandardValidator) Validate(ctx context.Context, artifact *domain.Artif
 	}
 }
 
+func (v *StandardValidator) validateJSONSchema(instance any, schemaPath string) ([]string, error) {
+	resolvedSchemaPath, err := v.resolveSchemaPath(schemaPath)
+	if err != nil {
+		return nil, err
+	}
+
+	compiler := jsonschema.NewCompiler()
+	schema, err := compiler.Compile(resolvedSchemaPath)
+	if err != nil {
+		return nil, fmt.Errorf("failed to compile JSON schema %q: %w", resolvedSchemaPath, err)
+	}
+
+	if err := schema.Validate(instance); err != nil {
+		return []string{fmt.Sprintf("json schema validation failed: %v", err)}, nil
+	}
+	return nil, nil
+}
+
+func (v *FSValidator) validateJSONSchema(instance any, schemaPath string) ([]string, error) {
+	schemaName, schemaDoc, err := v.loadSchemaDocument(schemaPath)
+	if err != nil {
+		return nil, err
+	}
+
+	resourceURL := fsSchemaResourceURL(schemaName)
+	compiler := jsonschema.NewCompiler()
+	if err := compiler.AddResource(resourceURL, schemaDoc); err != nil {
+		return nil, fmt.Errorf("failed to register JSON schema %q: %w", schemaName, err)
+	}
+	schema, err := compiler.Compile(resourceURL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to compile JSON schema %q: %w", schemaName, err)
+	}
+
+	if err := schema.Validate(instance); err != nil {
+		return []string{fmt.Sprintf("json schema validation failed: %v", err)}, nil
+	}
+	return nil, nil
+}
+
 func parseJSON(body []byte) (any, error) {
 	var v any
 	if err := json.Unmarshal(body, &v); err != nil {
@@ -132,6 +187,20 @@ func (v *StandardValidator) LoadSchemaDocument(ctx context.Context, schemaPath s
 	return doc, nil
 }
 
+func (v *FSValidator) LoadSchemaDocument(ctx context.Context, schemaPath string) (any, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	_, doc, err := v.loadSchemaDocument(schemaPath)
+	if err != nil {
+		return nil, err
+	}
+	return doc, nil
+}
+
 func (v *StandardValidator) resolveSchemaPath(schemaPath string) (string, error) {
 	if strings.TrimSpace(schemaPath) == "" {
 		return "", errors.New("schema path is required for json_schema validation")
@@ -149,3 +218,75 @@ func (v *StandardValidator) resolveSchemaPath(schemaPath string) (string, error)
 
 	return resolved, nil
 }
+
+func (v *FSValidator) loadSchemaDocument(schemaPath string) (string, any, error) {
+	resolved, err := v.resolveSchemaPath(schemaPath)
+	if err != nil {
+		return "", nil, err
+	}
+
+	raw, err := fs.ReadFile(v.fsys, resolved)
+	if err != nil {
+		return "", nil, fmt.Errorf("failed to read schema file %q: %w", resolved, err)
+	}
+
+	var doc any
+	if err := json.Unmarshal(raw, &doc); err != nil {
+		return "", nil, fmt.Errorf("failed to decode JSON schema %q: %w", resolved, err)
+	}
+	return resolved, doc, nil
+}
+
+func (v *FSValidator) resolveSchemaPath(schemaPath string) (string, error) {
+	if strings.TrimSpace(schemaPath) == "" {
+		return "", errors.New("schema path is required for json_schema validation")
+	}
+	if v.fsys == nil {
+		return "", errors.New("schema filesystem is nil")
+	}
+
+	cleanRoot := filecatalog.CleanFSRoot(v.root)
+	rootInfo, err := fs.Stat(v.fsys, cleanRoot)
+	if err != nil {
+		return "", fmt.Errorf("failed to access schema source %q: %w", cleanRoot, err)
+	}
+
+	var resolved string
+	if rootInfo.IsDir() {
+		resolvedPath, _, err := filecatalog.ResolveFSPath(cleanRoot, cleanRoot, schemaPath)
+		if err != nil {
+			return "", err
+		}
+		resolved = resolvedPath
+	} else {
+		cleanSchemaPath, err := cleanSchemaFSPath(schemaPath)
+		if err != nil {
+			return "", err
+		}
+		if cleanSchemaPath != path.Base(cleanRoot) {
+			return "", fmt.Errorf("schema path %q does not match schema file %q", cleanSchemaPath, path.Base(cleanRoot))
+		}
+		resolved = cleanRoot
+	}
+
+	if _, err := fs.Stat(v.fsys, resolved); err != nil {
+		return "", fmt.Errorf("failed to access schema file %q: %w", resolved, err)
+	}
+	return resolved, nil
+}
+
+func cleanSchemaFSPath(schemaPath string) (string, error) {
+	cleaned := strings.TrimSpace(schemaPath)
+	if cleaned == "" {
+		return "", errors.New("schema path is required for json_schema validation")
+	}
+	cleaned = path.Clean(cleaned)
+	if path.IsAbs(cleaned) {
+		return "", fmt.Errorf("schema path %q must be relative", schemaPath)
+	}
+	return cleaned, nil
+}
+
+func fsSchemaResourceURL(schemaName string) string {
+	return "scriptorium-schema:///" + strings.TrimPrefix(path.Clean(schemaName), "/")
+}

internal/validate/standard_validator_test.go

@@ -4,7 +4,9 @@ import (
 	"context"
 	"os"
 	"path/filepath"
+	"strings"
 	"testing"
+	"testing/fstest"
 
 	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
 )
@@ -250,3 +252,132 @@ func TestStandardValidatorLoadSchemaDocumentInvalidJSON(t *testing.T) {
 		t.Fatal("expected decode error")
 	}
 }
+
+func TestFSValidatorJSONSchemaSuccess(t *testing.T) {
+	v := NewFSValidator(fstest.MapFS{
+		"schemas/events.schema.json": &fstest.MapFile{Data: []byte(`{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "object",
+  "required": ["events"],
+  "properties": {
+    "events": {"type": "array"}
+  }
+}`)},
+	}, "schemas")
+
+	res, err := v.Validate(context.Background(), &domain.Artifact{Body: []byte(`{"events":[]}`)}, domain.OutputContract{
+		ValidationMode: domain.ValidationJSONSchema,
+		SchemaPath:     "events.schema.json",
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if res.Status != domain.ValidationPassed || !res.IsValid {
+		t.Fatalf("expected passed/valid, got status=%q valid=%v", res.Status, res.IsValid)
+	}
+}
+
+func TestFSValidatorJSONSchemaPathContainment(t *testing.T) {
+	t.Run("nested schema inside root succeeds", func(t *testing.T) {
+		v := NewFSValidator(fstest.MapFS{
+			"schemas/nested/events.schema.json": &fstest.MapFile{Data: []byte(`{
+  "type": "object",
+  "required": ["events"],
+  "properties": {
+    "events": {"type": "array"}
+  }
+}`)},
+		}, "schemas")
+
+		res, err := v.Validate(context.Background(), &domain.Artifact{Body: []byte(`{"events":[]}`)}, domain.OutputContract{
+			ValidationMode: domain.ValidationJSONSchema,
+			SchemaPath:     "nested/events.schema.json",
+		})
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if res.Status != domain.ValidationPassed || !res.IsValid {
+			t.Fatalf("expected passed/valid, got status=%q valid=%v", res.Status, res.IsValid)
+		}
+	})
+
+	tests := []struct {
+		name       string
+		schemaPath string
+		wantErr    string
+	}{
+		{name: "parent escape rejected", schemaPath: "../outside.schema.json", wantErr: "escapes source root"},
+		{name: "absolute path rejected", schemaPath: "/outside.schema.json", wantErr: "must be relative"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			v := NewFSValidator(fstest.MapFS{
+				"schemas/events.schema.json":  &fstest.MapFile{Data: []byte(`{"type":"object"}`)},
+				"outside.schema.json":         &fstest.MapFile{Data: []byte(`{"type":"object"}`)},
+				"schemas/outside.schema.json": &fstest.MapFile{Data: []byte(`{"type":"object"}`)},
+			}, "schemas")
+
+			_, err := v.Validate(context.Background(), &domain.Artifact{Body: []byte(`{"events":[]}`)}, domain.OutputContract{
+				ValidationMode: domain.ValidationJSONSchema,
+				SchemaPath:     tc.schemaPath,
+			})
+			if err == nil {
+				t.Fatal("expected schema path error")
+			}
+			if !strings.Contains(err.Error(), tc.wantErr) {
+				t.Fatalf("expected error to contain %q, got %v", tc.wantErr, err)
+			}
+		})
+	}
+}
+
+func TestFSValidatorSingleSchemaFileUsesBaseName(t *testing.T) {
+	v := NewFSValidator(fstest.MapFS{
+		"events.schema.json": &fstest.MapFile{Data: []byte(`{
+  "type": "object",
+  "required": ["events"],
+  "properties": {
+    "events": {"type": "array"}
+  }
+}`)},
+	}, "events.schema.json")
+
+	res, err := v.Validate(context.Background(), &domain.Artifact{Body: []byte(`{"events":[]}`)}, domain.OutputContract{
+		ValidationMode: domain.ValidationJSONSchema,
+		SchemaPath:     "events.schema.json",
+	})
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	if res.Status != domain.ValidationPassed || !res.IsValid {
+		t.Fatalf("expected passed/valid, got status=%q valid=%v", res.Status, res.IsValid)
+	}
+
+	_, err = v.Validate(context.Background(), &domain.Artifact{Body: []byte(`{"events":[]}`)}, domain.OutputContract{
+		ValidationMode: domain.ValidationJSONSchema,
+		SchemaPath:     "other.schema.json",
+	})
+	if err == nil {
+		t.Fatal("expected schema path mismatch error")
+	}
+}
+
+func TestFSValidatorLoadSchemaDocument(t *testing.T) {
+	v := NewFSValidator(fstest.MapFS{
+		"schemas/schema.json": &fstest.MapFile{Data: []byte(`{"type":"object"}`)},
+	}, "schemas")
+	loader, ok := v.(SchemaDocumentLoader)
+	if !ok {
+		t.Fatal("fs validator must implement SchemaDocumentLoader")
+	}
+
+	doc, err := loader.LoadSchemaDocument(context.Background(), "schema.json")
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+	obj, ok := doc.(map[string]any)
+	if !ok || obj["type"] != "object" {
+		t.Fatalf("unexpected schema document: %#v", doc)
+	}
+}

json_copy.go

@@ -0,0 +1,218 @@
+package scriptorium
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"reflect"
+	"strconv"
+)
+
+const maxSafeJSONInteger = 1<<53 - 1
+
+type jsonVisit struct {
+	typ reflect.Type
+	ptr uintptr
+}
+
+func copyPublicJSONMap(src map[string]any) (map[string]any, error) {
+	if src == nil {
+		return nil, nil
+	}
+	copied, err := copyPublicJSONValue(reflect.ValueOf(src), "extra_params", make(map[jsonVisit]struct{}))
+	if err != nil {
+		return nil, err
+	}
+	out, ok := copied.(map[string]any)
+	if !ok {
+		return nil, fmt.Errorf("extra_params: expected object")
+	}
+	return out, nil
+}
+
+func copyPublicJSONValue(value reflect.Value, path string, seen map[jsonVisit]struct{}) (any, error) {
+	if !value.IsValid() {
+		return nil, nil
+	}
+	if value.Kind() == reflect.Interface {
+		if value.IsNil() {
+			return nil, nil
+		}
+		return copyPublicJSONValue(value.Elem(), path, seen)
+	}
+	if !value.CanInterface() {
+		return nil, fmt.Errorf("%s: value cannot be copied", path)
+	}
+	if number, ok := value.Interface().(json.Number); ok {
+		f, err := strconv.ParseFloat(number.String(), 64)
+		if err != nil || math.IsNaN(f) || math.IsInf(f, 0) {
+			return nil, fmt.Errorf("%s: invalid JSON number", path)
+		}
+		return number, nil
+	}
+
+	switch value.Kind() {
+	case reflect.Bool, reflect.String:
+		return value.Interface(), nil
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		if value.Int() < -maxSafeJSONInteger || value.Int() > maxSafeJSONInteger {
+			return nil, fmt.Errorf("%s: integer is outside the JSON-safe range", path)
+		}
+		return value.Interface(), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		if value.Uint() > maxSafeJSONInteger {
+			return nil, fmt.Errorf("%s: integer is outside the JSON-safe range", path)
+		}
+		return value.Interface(), nil
+	case reflect.Float32, reflect.Float64:
+		f := value.Convert(reflect.TypeOf(float64(0))).Float()
+		if math.IsNaN(f) || math.IsInf(f, 0) {
+			return nil, fmt.Errorf("%s: floating-point value must be finite", path)
+		}
+		return value.Interface(), nil
+	case reflect.Pointer:
+		if value.IsNil() {
+			return nil, nil
+		}
+		visit := jsonVisit{typ: value.Type(), ptr: value.Pointer()}
+		if _, ok := seen[visit]; ok {
+			return nil, fmt.Errorf("%s: cyclic value is not supported", path)
+		}
+		seen[visit] = struct{}{}
+		defer delete(seen, visit)
+		return copyPublicJSONValue(value.Elem(), path, seen)
+	case reflect.Map:
+		return copyPublicJSONMapValue(value, path, seen)
+	case reflect.Slice:
+		if value.IsNil() {
+			return nil, nil
+		}
+		return copyPublicJSONSequenceValue(value, path, seen)
+	case reflect.Array:
+		return copyPublicJSONSequenceValue(value, path, seen)
+	default:
+		return nil, fmt.Errorf("%s: unsupported JSON value type %s", path, value.Type())
+	}
+}
+
+func copyPublicJSONMapValue(value reflect.Value, path string, seen map[jsonVisit]struct{}) (any, error) {
+	if value.IsNil() {
+		return nil, nil
+	}
+	if value.Type().Key().Kind() != reflect.String {
+		return nil, fmt.Errorf("%s: map key type %s is not supported", path, value.Type().Key())
+	}
+
+	visit := jsonVisit{typ: value.Type(), ptr: value.Pointer()}
+	if _, ok := seen[visit]; ok {
+		return nil, fmt.Errorf("%s: cyclic value is not supported", path)
+	}
+	seen[visit] = struct{}{}
+	defer delete(seen, visit)
+
+	type entry struct {
+		key   reflect.Value
+		name  string
+		value any
+	}
+	entries := make([]entry, 0, value.Len())
+	preserveType := true
+	elemType := value.Type().Elem()
+	iter := value.MapRange()
+	for iter.Next() {
+		key := iter.Key()
+		name := key.String()
+		copied, err := copyPublicJSONValue(iter.Value(), path+"."+name, seen)
+		if err != nil {
+			return nil, err
+		}
+		entries = append(entries, entry{key: key, name: name, value: copied})
+		if copied == nil {
+			if !canAssignNil(elemType) {
+				preserveType = false
+			}
+			continue
+		}
+		if !reflect.TypeOf(copied).AssignableTo(elemType) {
+			preserveType = false
+		}
+	}
+
+	if preserveType {
+		out := reflect.MakeMapWithSize(value.Type(), len(entries))
+		for _, entry := range entries {
+			if entry.value == nil {
+				out.SetMapIndex(entry.key, reflect.Zero(elemType))
+				continue
+			}
+			out.SetMapIndex(entry.key, reflect.ValueOf(entry.value))
+		}
+		return out.Interface(), nil
+	}
+
+	out := make(map[string]any, len(entries))
+	for _, entry := range entries {
+		out[entry.name] = entry.value
+	}
+	return out, nil
+}
+
+func copyPublicJSONSequenceValue(value reflect.Value, path string, seen map[jsonVisit]struct{}) (any, error) {
+	var visit jsonVisit
+	if value.Kind() == reflect.Slice {
+		visit = jsonVisit{typ: value.Type(), ptr: value.Pointer()}
+		if _, ok := seen[visit]; ok {
+			return nil, fmt.Errorf("%s: cyclic value is not supported", path)
+		}
+		seen[visit] = struct{}{}
+		defer delete(seen, visit)
+	}
+
+	values := make([]any, value.Len())
+	preserveType := true
+	elemType := value.Type().Elem()
+	for i := 0; i < value.Len(); i++ {
+		copied, err := copyPublicJSONValue(value.Index(i), fmt.Sprintf("%s[%d]", path, i), seen)
+		if err != nil {
+			return nil, err
+		}
+		values[i] = copied
+		if copied == nil {
+			if !canAssignNil(elemType) {
+				preserveType = false
+			}
+			continue
+		}
+		if !reflect.TypeOf(copied).AssignableTo(elemType) {
+			preserveType = false
+		}
+	}
+
+	if preserveType {
+		out := reflect.New(value.Type()).Elem()
+		if value.Kind() == reflect.Slice {
+			out = reflect.MakeSlice(value.Type(), value.Len(), value.Len())
+		}
+		for i, copied := range values {
+			if copied == nil {
+				out.Index(i).Set(reflect.Zero(elemType))
+				continue
+			}
+			out.Index(i).Set(reflect.ValueOf(copied))
+		}
+		return out.Interface(), nil
+	}
+
+	out := make([]any, len(values))
+	copy(out, values)
+	return out, nil
+}
+
+func canAssignNil(typ reflect.Type) bool {
+	switch typ.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Map, reflect.Pointer, reflect.Slice:
+		return true
+	default:
+		return false
+	}
+}

llm_adapter.go

@@ -0,0 +1,23 @@
+package scriptorium
+
+import (
+	"context"
+	"fmt"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+)
+
+type publicLLMClientAdapter struct {
+	client LLMClient
+}
+
+func (a publicLLMClientAdapter) Generate(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error) {
+	resp, err := a.client.Generate(ctx, fromDomainGenerateRequest(req))
+	if err != nil {
+		return nil, err
+	}
+	if resp == nil {
+		return nil, fmt.Errorf("%w: llm client returned nil response", ErrLLMGenerate)
+	}
+	return toDomainGenerateResponse(resp), nil
+}

profiles.go

@@ -0,0 +1,124 @@
+package scriptorium
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/scriptorium/internal/domain"
+	"gitea.maximumdirect.net/eric/scriptorium/internal/profile"
+)
+
+// OpenAICompatibleProfile returns an ordinary in-memory Profile for an
+// OpenAI-compatible chat-completions endpoint.
+//
+// It does not register global state, maintain a model catalog, or resolve
+// credentials. If APIKeyRequired is true, callers satisfy it with
+// RunRequest.APIKey. Raw API keys do not belong in profiles.
+func OpenAICompatibleProfile(cfg OpenAICompatibleProfileConfig) Profile {
+	return Profile{
+		ID:              cfg.ID,
+		Endpoint:        cfg.Endpoint,
+		Model:           cfg.Model,
+		Temperature:     cfg.Temperature,
+		MaxTokens:       cfg.MaxTokens,
+		TopP:            cfg.TopP,
+		TimeoutSeconds:  cfg.TimeoutSeconds,
+		ServiceTier:     cfg.ServiceTier,
+		ReasoningEffort: cfg.ReasoningEffort,
+		APIKeyRequired:  cfg.APIKeyRequired,
+		ExtraParams:     copyShallowAnyMap(cfg.ExtraParams),
+	}
+}
+
+func copyShallowAnyMap(src map[string]any) map[string]any {
+	if src == nil {
+		return nil
+	}
+	out := make(map[string]any, len(src))
+	for k, v := range src {
+		out[k] = v
+	}
+	return out
+}
+
+type memoryProfileRepository struct {
+	profiles map[string]domain.ExecutionProfile
+}
+
+func newMemoryProfileRepository(profiles []Profile) (*memoryProfileRepository, error) {
+	repo := &memoryProfileRepository{profiles: make(map[string]domain.ExecutionProfile, len(profiles))}
+	for _, publicProfile := range profiles {
+		prof, err := toDomainProfile(publicProfile)
+		if err != nil {
+			return nil, err
+		}
+		if _, exists := repo.profiles[prof.ID]; exists {
+			return nil, fmt.Errorf("duplicate profile id %q", prof.ID)
+		}
+		repo.profiles[prof.ID] = prof
+	}
+	return repo, nil
+}
+
+func (r *memoryProfileRepository) GetProfile(_ context.Context, id string) (*domain.ExecutionProfile, error) {
+	if r == nil {
+		return nil, profile.ErrProfileNotFound
+	}
+	prof, ok := r.profiles[id]
+	if !ok {
+		return nil, profile.ErrProfileNotFound
+	}
+	prof.ExtraParams = copyAnyMap(prof.ExtraParams)
+	return &prof, nil
+}
+
+func toDomainProfile(publicProfile Profile) (domain.ExecutionProfile, error) {
+	extraParams, err := copyPublicJSONMap(publicProfile.ExtraParams)
+	if err != nil {
+		return domain.ExecutionProfile{}, err
+	}
+	prof := domain.ExecutionProfile{
+		ID:              strings.TrimSpace(publicProfile.ID),
+		Endpoint:        publicProfile.Endpoint,
+		Model:           publicProfile.Model,
+		Temperature:     publicProfile.Temperature,
+		MaxTokens:       publicProfile.MaxTokens,
+		TopP:            publicProfile.TopP,
+		TimeoutSeconds:  publicProfile.TimeoutSeconds,
+		ServiceTier:     publicProfile.ServiceTier,
+		ReasoningEffort: publicProfile.ReasoningEffort,
+		APIKeyRequired:  publicProfile.APIKeyRequired,
+		ExtraParams:     extraParams,
+	}
+	if err := validatePublicProfile(prof); err != nil {
+		return domain.ExecutionProfile{}, err
+	}
+	return prof, nil
+}
+
+func validatePublicProfile(prof domain.ExecutionProfile) error {
+	if strings.TrimSpace(prof.ID) == "" {
+		return errors.New("id is required")
+	}
+	if strings.TrimSpace(prof.Endpoint) == "" {
+		return errors.New("endpoint is required")
+	}
+	if strings.TrimSpace(prof.Model) == "" {
+		return errors.New("model is required")
+	}
+	if prof.Temperature < 0 || prof.Temperature > 2 {
+		return errors.New("temperature must be between 0 and 2")
+	}
+	if prof.MaxTokens < 0 {
+		return errors.New("max_tokens must be greater than or equal to 0")
+	}
+	if prof.TopP < 0 || prof.TopP > 1 {
+		return errors.New("top_p must be between 0 and 1")
+	}
+	if prof.TimeoutSeconds < 0 {
+		return errors.New("timeout_seconds must be greater than or equal to 0")
+	}
+	return nil
+}

types.go

@@ -0,0 +1,298 @@
+package scriptorium
+
+import (
+	"context"
+	"time"
+)
+
+// ArtifactRefType defines how an artifact is referenced.
+type ArtifactRefType string
+
+const (
+	ArtifactRefInline ArtifactRefType = "inline"
+	ArtifactRefFile   ArtifactRefType = "file"
+)
+
+// OutputFormat defines the desired output format.
+type OutputFormat string
+
+const (
+	FormatText     OutputFormat = "text"
+	FormatMarkdown OutputFormat = "markdown"
+	FormatJSON     OutputFormat = "json"
+)
+
+// ValidationMode defines the output validation strategy.
+type ValidationMode string
+
+const (
+	ValidationNone       ValidationMode = "none"
+	ValidationBasic      ValidationMode = "basic"
+	ValidationJSON       ValidationMode = "json"
+	ValidationJSONSchema ValidationMode = "json_schema"
+)
+
+// ValidationStatus defines the result of a validation check.
+type ValidationStatus string
+
+const (
+	ValidationPassed  ValidationStatus = "passed"
+	ValidationFailed  ValidationStatus = "failed"
+	ValidationSkipped ValidationStatus = "skipped"
+)
+
+// CacheControlType defines provider cache behavior for prompt content.
+type CacheControlType string
+
+const (
+	CacheControlEphemeral CacheControlType = "ephemeral"
+)
+
+// StructuredOutputType identifies provider-level structured output modes.
+type StructuredOutputType string
+
+const (
+	StructuredOutputJSONSchema StructuredOutputType = "json_schema"
+)
+
+// RunRequest represents a request to prepare or run a single prompt.
+type RunRequest struct {
+	PromptID      string
+	PromptVersion string
+	ProfileID     string
+	APIKey        string `json:"-"`
+	Inputs        map[string]ArtifactRef
+	Vars          map[string]string
+	Execution     *ExecutionTargetOverride
+	Validation    *OutputContract
+	Metadata      map[string]string
+}
+
+// PreparedRun contains prepared prompt execution state. It does not include
+// resolved API key values, model output, validation results, or internal target
+// presence metadata.
+type PreparedRun struct {
+	PromptID             string                `json:"prompt_id"`
+	PromptVersion        string                `json:"prompt_version,omitempty"`
+	PromptHash           string                `json:"prompt_hash,omitempty"`
+	SelectedProfileID    string                `json:"selected_profile_id"`
+	EffectiveModelParams ExecutionTarget       `json:"effective_model_params"`
+	OutputContract       OutputContract        `json:"output_contract"`
+	StructuredOutput     *StructuredOutputSpec `json:"structured_output,omitempty"`
+	InputHashes          map[string]string     `json:"input_hashes,omitempty"`
+	SessionID            string                `json:"session_id,omitempty"`
+	RenderedPromptHash   string                `json:"rendered_prompt_hash"`
+	Messages             []RenderedMessage     `json:"messages"`
+	StartTime            time.Time             `json:"start_time,omitempty"`
+	EndTime              time.Time             `json:"end_time,omitempty"`
+	DurationMS           int64                 `json:"duration_ms,omitempty"`
+}
+
+// RunResult contains generated output, validation state, and run metadata.
+type RunResult struct {
+	RunID                string            `json:"run_id"`
+	Artifact             Artifact          `json:"artifact"`
+	RawOutput            string            `json:"raw_output"`
+	Validation           ValidationResult  `json:"validation"`
+	PromptID             string            `json:"prompt_id"`
+	PromptVersion        string            `json:"prompt_version,omitempty"`
+	PromptHash           string            `json:"prompt_hash,omitempty"`
+	RenderedPromptHash   string            `json:"rendered_prompt_hash"`
+	SelectedProfileID    string            `json:"selected_profile_id"`
+	ModelName            string            `json:"model_name"`
+	Endpoint             string            `json:"endpoint"`
+	EffectiveModelParams ExecutionTarget   `json:"effective_model_params"`
+	InputHashes          map[string]string `json:"input_hashes,omitempty"`
+	Usage                TokenUsage        `json:"usage"`
+	StartTime            time.Time         `json:"start_time,omitempty"`
+	EndTime              time.Time         `json:"end_time,omitempty"`
+	Duration             time.Duration     `json:"duration,omitempty"`
+}
+
+// ArtifactRef represents a reference to prompt input content.
+type ArtifactRef struct {
+	Type ArtifactRefType
+	URI  string
+	Body string
+}
+
+// Artifact represents loaded artifact content.
+type Artifact struct {
+	Name        string
+	ContentType string
+	Body        []byte
+	URI         string
+	Size        int64
+	Hash        string
+}
+
+// ExecutionTarget represents effective model runtime settings.
+type ExecutionTarget struct {
+	Endpoint        string         `json:"endpoint"`
+	Model           string         `json:"model"`
+	Temperature     float64        `json:"temperature"`
+	MaxTokens       int            `json:"max_tokens"`
+	TopP            float64        `json:"top_p"`
+	TimeoutSeconds  int            `json:"timeout_seconds"`
+	ServiceTier     string         `json:"service_tier"`
+	ReasoningEffort string         `json:"reasoning_effort"`
+	APIKeyEnv       string         `json:"api_key_env"`
+	ExtraParams     map[string]any `json:"extra_params"`
+}
+
+// ExecutionTargetOverride represents per-request runtime setting overrides.
+type ExecutionTargetOverride struct {
+	Endpoint        string
+	Model           string
+	Temperature     *float64
+	MaxTokens       *int
+	TopP            *float64
+	TimeoutSeconds  *int
+	ServiceTier     string
+	ReasoningEffort string
+	APIKeyEnv       string
+	ExtraParams     map[string]any
+}
+
+// Profile is an in-memory execution profile for library consumers.
+//
+// It is equivalent to a loaded profile file after validation. Raw API keys do
+// not belong in profiles; use APIKeyRequired to require callers to provide
+// RunRequest.APIKey for each request, or use profile YAML api_key_env with file
+// and FS profile sources.
+type Profile struct {
+	ID              string
+	Endpoint        string
+	Model           string
+	Temperature     float64
+	MaxTokens       int
+	TopP            float64
+	TimeoutSeconds  int
+	ServiceTier     string
+	ReasoningEffort string
+	APIKeyRequired  bool
+	ExtraParams     map[string]any
+}
+
+// OpenAICompatibleProfileConfig configures an OpenAI-compatible in-memory
+// profile.
+//
+// It contains ordinary profile fields for OpenAI-compatible chat-completions
+// endpoints. APIKeyRequired is satisfied by RunRequest.APIKey. Raw API keys do
+// not belong in this config.
+type OpenAICompatibleProfileConfig struct {
+	ID              string
+	Endpoint        string
+	Model           string
+	APIKeyRequired  bool
+	Temperature     float64
+	MaxTokens       int
+	TopP            float64
+	TimeoutSeconds  int
+	ServiceTier     string
+	ReasoningEffort string
+	ExtraParams     map[string]any
+}
+
+// ExecutionTargetPresence tracks which numeric runtime settings were explicit
+// request overrides.
+type ExecutionTargetPresence struct {
+	Temperature    bool
+	MaxTokens      bool
+	TopP           bool
+	TimeoutSeconds bool
+}
+
+// OutputContract defines output and validation requirements.
+type OutputContract struct {
+	Format         OutputFormat   `json:"format"`
+	ValidationMode ValidationMode `json:"validation_mode"`
+	SchemaPath     string         `json:"schema_path"`
+	RepairAttempts int            `json:"repair_attempts"`
+}
+
+// ValidationResult represents output validation state.
+type ValidationResult struct {
+	Status         ValidationStatus `json:"status"`
+	Mode           ValidationMode   `json:"mode"`
+	Errors         []string         `json:"errors,omitempty"`
+	SchemaPath     string           `json:"schema_path,omitempty"`
+	RepairAttempts int              `json:"repair_attempts"`
+	IsValid        bool             `json:"is_valid"`
+}
+
+// TokenUsage tracks token consumption.
+type TokenUsage struct {
+	PromptTokens     int `json:"prompt_tokens"`
+	CompletionTokens int `json:"completion_tokens"`
+	TotalTokens      int `json:"total_tokens"`
+	CachedTokens     int `json:"cached_tokens"`
+	CacheWriteTokens int `json:"cache_write_tokens"`
+}
+
+// RenderedPrompt is the fully rendered prompt passed to an LLM client.
+type RenderedPrompt struct {
+	SessionID string            `json:"session_id,omitempty"`
+	Messages  []RenderedMessage `json:"messages"`
+}
+
+// RenderedMessage is a rendered chat message.
+type RenderedMessage struct {
+	Role         string        `json:"role"`
+	Content      string        `json:"content"`
+	CacheControl *CacheControl `json:"cache_control,omitempty"`
+}
+
+// CacheControl describes provider cache metadata attached to prompt content.
+type CacheControl struct {
+	Type CacheControlType `json:"type"`
+	TTL  string           `json:"ttl,omitempty"`
+}
+
+// StructuredOutputSpec describes provider-level structured output.
+type StructuredOutputSpec struct {
+	Type       StructuredOutputType      `json:"type"`
+	JSONSchema *StructuredOutputJSONSpec `json:"json_schema,omitempty"`
+}
+
+// StructuredOutputJSONSpec contains JSON Schema output constraints.
+type StructuredOutputJSONSpec struct {
+	Name   string `json:"name"`
+	Strict bool   `json:"strict"`
+	Schema any    `json:"schema"`
+}
+
+// LLMClient executes rendered prompts for Engine.Run.
+type LLMClient interface {
+	Generate(context.Context, GenerateRequest) (*GenerateResponse, error)
+}
+
+// GenerateRequest is passed to an injected LLM client.
+type GenerateRequest struct {
+	Prompt           RenderedPrompt          `json:"prompt"`
+	Target           ExecutionTarget         `json:"target"`
+	TargetPresence   ExecutionTargetPresence `json:"target_presence"`
+	StructuredOutput *StructuredOutputSpec   `json:"structured_output,omitempty"`
+	APIKey           string                  `json:"-"`
+}
+
+// GenerateResponse is returned by an injected LLM client.
+type GenerateResponse struct {
+	Content string     `json:"content"`
+	Usage   TokenUsage `json:"usage"`
+}
+
+// File returns a file-backed artifact reference.
+func File(path string) ArtifactRef {
+	return ArtifactRef{Type: ArtifactRefFile, URI: path}
+}
+
+// Inline returns an inline artifact reference.
+func Inline(body string) ArtifactRef {
+	return ArtifactRef{Type: ArtifactRefInline, Body: body}
+}
+
+// InlineWithURI returns an inline artifact reference with URI metadata.
+func InlineWithURI(uri string, body string) ArtifactRef {
+	return ArtifactRef{Type: ArtifactRefInline, URI: uri, Body: body}
+}