Add framework documentation and offline example

README.md

@@ -1,18 +1,34 @@
 # Promptkit
 
-Promptkit is the reusable Go prompt-execution framework being separated from
+Promptkit is a reusable Go library for preparing and executing prompt-defined
-Scriptorium. Its module path is:
+LLM workflows. Its module path is:
 
 ```text
 gitea.maximumdirect.net/eric/promptkit
 ```
 
-The repository currently provides the independent Go module and its root public
+The root `promptkit` package provides the supported public engine. Consumers
-package boundary. Framework behavior and consumer APIs have not yet been
+can configure filesystem or in-memory prompt, profile, and schema sources,
-extracted, so there is no installation or usage example at this time.
+prepare requests without generation, run requests with the built-in
+OpenAI-compatible client, or inject their own model client and artifact reader.
+
+## Quickstart
+
+Run the maintained offline preparation example from the repository root:
+
+```sh
+go run ./examples/go-library/prepare
+```
+
+It loads a repository-local prompt, supplies an in-memory profile and inline
+input, and prints deterministic preparation metadata without contacting a
+provider or requiring credentials. Read the
+[example source](examples/go-library/prepare/main.go), the
+[Go package consumer guide](docs/consumers/pkg-promptkit.md), and the
+[framework format reference](docs/formats.md) to build a consumer workflow.
 
 Contributors should start with the [development guide](docs/development.md).
 The [architecture policy](docs/policy/architecture.md) defines the library
-boundary and constraints that future framework work must preserve.
+boundary and constraints that framework work must preserve.
 
 Promptkit is licensed under the [GNU General Public License version 3](LICENSE).

architecture_test.go

@@ -0,0 +1,89 @@
+package promptkit_test
+
+import (
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+const formerModulePath = "gitea.maximumdirect.net/eric/" + "scrip" + "torium"
+
+func TestRepositoryDoesNotImportFormerModule(t *testing.T) {
+	violations, err := findFormerModuleImports(".")
+	if err != nil {
+		t.Fatalf("inspect repository imports: %v", err)
+	}
+	if len(violations) > 0 {
+		t.Fatalf("repository imports the former module:\n%s", strings.Join(violations, "\n"))
+	}
+}
+
+func TestFormerModuleGuardFindsNestedImport(t *testing.T) {
+	root := t.TempDir()
+	nested := filepath.Join(root, "nested", "package")
+	if err := os.MkdirAll(nested, 0o755); err != nil {
+		t.Fatalf("create nested package: %v", err)
+	}
+
+	sourcePath := filepath.Join(nested, "violation.go")
+	source := "package nested\n\nimport _ " + strconv.Quote(formerModulePath+"/internal/domain") + "\n"
+	if err := os.WriteFile(sourcePath, []byte(source), 0o600); err != nil {
+		t.Fatalf("write nested source: %v", err)
+	}
+
+	violations, err := findFormerModuleImports(root)
+	if err != nil {
+		t.Fatalf("inspect nested imports: %v", err)
+	}
+	if len(violations) != 1 {
+		t.Fatalf("violations = %v, want one nested import", violations)
+	}
+	if !strings.Contains(violations[0], "violation.go") ||
+		!strings.Contains(violations[0], formerModulePath+"/internal/domain") {
+		t.Fatalf("violation = %q, want file and import path", violations[0])
+	}
+}
+
+func findFormerModuleImports(root string) ([]string, error) {
+	var violations []string
+	err := filepath.WalkDir(root, func(path string, entry fs.DirEntry, walkErr error) error {
+		if walkErr != nil {
+			return walkErr
+		}
+		if entry.IsDir() {
+			switch entry.Name() {
+			case ".git", "generated", "vendor":
+				return filepath.SkipDir
+			}
+			return nil
+		}
+		if filepath.Ext(path) != ".go" {
+			return nil
+		}
+
+		file, err := parser.ParseFile(token.NewFileSet(), path, nil, parser.ImportsOnly|parser.ParseComments)
+		if err != nil {
+			return err
+		}
+		if ast.IsGenerated(file) {
+			return nil
+		}
+		for _, spec := range file.Imports {
+			importPath, err := strconv.Unquote(spec.Path.Value)
+			if err != nil {
+				return err
+			}
+			if importPath == formerModulePath || strings.HasPrefix(importPath, formerModulePath+"/") {
+				violations = append(violations, path+": "+importPath)
+			}
+		}
+		return nil
+	})
+	return violations, err
+}

artifact_reader.go

@@ -0,0 +1,39 @@
+package promptkit
+
+import (
+	"context"
+	"errors"
+
+	artifactadapter "gitea.maximumdirect.net/eric/promptkit/internal/artifact"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+var errNilArtifactReaderResponse = errors.New("artifact reader returned nil artifact without error")
+
+type publicArtifactReaderAdapter struct {
+	reader ArtifactReader
+}
+
+var _ artifactadapter.Reader = publicArtifactReaderAdapter{}
+
+func (a publicArtifactReaderAdapter) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	artifact, err := a.reader.Read(ctx, ArtifactRef{
+		Type: ArtifactRefType(ref.Type),
+		URI:  ref.URI,
+		Body: ref.Body,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if artifact == nil {
+		return nil, errNilArtifactReaderResponse
+	}
+	return &domain.Artifact{
+		Name:        artifact.Name,
+		ContentType: artifact.ContentType,
+		Body:        copyBytes(artifact.Body),
+		URI:         artifact.URI,
+		Size:        artifact.Size,
+		Hash:        artifact.Hash,
+	}, nil
+}

artifact_reader_internal_test.go

@@ -0,0 +1,36 @@
+package promptkit
+
+import (
+	"context"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestPublicArtifactReaderAdapterCopiesBody(t *testing.T) {
+	reader := internalArtifactReaderFake{
+		artifact: &Artifact{Body: []byte("original")},
+	}
+	adapter := publicArtifactReaderAdapter{reader: &reader}
+
+	artifact, err := adapter.Read(context.Background(), domain.ArtifactRef{
+		Type: domain.ArtifactRefInline,
+		URI:  "memory://input",
+		Body: "input",
+	})
+	if err != nil {
+		t.Fatalf("read artifact: %v", err)
+	}
+	artifact.Body[0] = 'X'
+	if got := string(reader.artifact.Body); got != "original" {
+		t.Fatalf("reader artifact body was mutated: %q", got)
+	}
+}
+
+type internalArtifactReaderFake struct {
+	artifact *Artifact
+}
+
+func (r *internalArtifactReaderFake) Read(context.Context, ArtifactRef) (*Artifact, error) {
+	return r.artifact, nil
+}

convert.go

@@ -0,0 +1,406 @@
+package promptkit
+
+import (
+	"reflect"
+
+	"gitea.maximumdirect.net/eric/promptkit/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
+}

doc.go

@@ -1,2 +1,8 @@
-// Package promptkit defines the public package boundary for the Promptkit Go module.
+// Package promptkit provides an embeddable engine for preparing and executing
+// prompt-defined LLM workflows.
+//
+// Applications construct an Engine with NewEngine, select filesystem or
+// in-memory definition sources with options, and use Prepare or Run to execute
+// requests. Concrete repositories, validators, and outbound clients remain
+// internal implementation details.
 package promptkit

docs/consumers/pkg-promptkit.md

@@ -0,0 +1,151 @@
+# Package `promptkit`
+
+Import path:
+
+```go
+import "gitea.maximumdirect.net/eric/promptkit"
+```
+
+Package `promptkit` is the supported Go contract for in-process prompt
+preparation and execution. The declarations and their GoDoc in the
+[root package](../../doc.go) own the exact API; this guide explains how the
+pieces are used together. The [framework format reference](../formats.md) owns
+prompt, profile, and schema file contracts.
+
+## Engine Construction And Sources
+
+Construct an engine with [`NewEngine`, `Config`, and
+`Option`](../../engine.go). `PromptDir` is required unless a prompt source
+option is supplied. `ProfileDir` optionally overlays built-in profiles, and an
+empty `SchemaDir` uses the current directory. `Timeout` is the transport-wide
+safety cap for the built-in OpenAI-compatible client. An optional `HTTPClient`
+is cloned; its positive timeout takes precedence.
+
+Nil options are ignored. Invalid construction, including a nil injected client
+or artifact reader, returns an error matching `ErrInvalidConfig`.
+
+The [source options](../../engine.go) replace their matching directory source:
+
+- `WithPromptFS` and `WithPromptFile` select prompt definitions;
+- `WithProfileFS` and `WithProfileFile` overlay built-in profiles;
+- `WithProfiles` adds in-memory profiles ahead of file and built-in profiles;
+- `WithSchemaFS` and `WithSchemaFile` select JSON Schema documents;
+- `WithLLMClient` replaces the built-in model client; and
+- `WithArtifactReader` replaces the default reader for every input.
+
+Source selection, path resolution, strict decoding, profile overlays, and
+file-to-request precedence are defined in the
+[framework format reference](../formats.md).
+
+Per-generation timeout values from profiles or requests are independent of
+the transport cap and caller context. An explicit request value of zero
+disables only the per-generation deadline. The
+[outbound integration contract](../integrations/openai-compatible-chat.md#timeout-and-cancellation)
+defines the complete timeout layering.
+
+## Preparation And Execution
+
+[`Engine.Prepare` and `Engine.Run`](../../engine.go) accept the public
+[`RunRequest`](../../types.go). `Prepare` resolves the prompt, profile, input
+artifacts, validation contract, and rendered messages without calling an LLM.
+`Run` performs the same preparation, calls the configured client, and validates
+the generated content. The maintained
+[offline preparation example](../../examples/go-library/prepare/main.go)
+provides a complete runnable workflow using a prompt file, in-memory profile,
+and inline input.
+
+[`PreparedRun` and `RunResult`](../../types.go) expose copied public values.
+Preparation returns effective settings, hashes, rendered messages, selected
+profile, structured-output information, and timing without resolved secrets or
+model output. Execution adds the generated artifact and raw output, validation
+state, model metadata, usage, run ID, and duration.
+
+A generated-content validation failure returns a result with
+`Validation.Status == ValidationFailed`. An inability to perform validation
+returns an error matching `ErrValidation`.
+
+## Requests, Inputs, And Overrides
+
+The [request and value declarations](../../types.go) own the available fields,
+serialized constants, and result shapes. Use `File`, `Inline`, or
+`InlineWithURI` to construct artifact references. The
+[framework format reference](../formats.md) defines declared inputs, template
+references, output contracts, and the relationship between file values and
+request overrides.
+
+`ExecutionTargetOverride` uses pointers for numeric settings so an explicit
+zero remains distinct from no override. `ExtraParams` accepts JSON-compatible
+strings, booleans, finite numbers, string-keyed objects, arrays or slices, and
+nil. Unsupported values, non-string map keys, non-finite numbers, and cycles
+match `ErrInvalidConfig` in profiles or `ErrInvalidRequest` in request
+overrides.
+
+Returned requests, profiles, prepared values, results, artifacts, maps, and
+slices are isolated from internal engine state. Consumers and injected
+extensions should not retain or mutate values owned by another caller.
+
+## Profiles And Credentials
+
+[`OpenAICompatibleProfile`](../../profiles.go) constructs an ordinary
+in-memory profile for an OpenAI-compatible chat-completions endpoint.
+`WithProfiles` rejects duplicate IDs in one call and gives in-memory profiles
+precedence over explicit file sources and built-ins.
+
+Raw API keys do not belong in profiles. File-backed profiles may name an
+environment variable, while an in-memory profile can require a request key.
+A direct `RunRequest.APIKey` is request-scoped and takes precedence over an
+environment lookup for the built-in client. Profile fields, ranges, built-ins,
+precedence, and credential rules are owned by the
+[framework format reference](../formats.md).
+
+API keys are excluded from JSON, prepared values, and results. The public
+`String` and `GoString` methods report only whether a direct key is present.
+Avoid reflection-based dumps of request structs, which can bypass that
+redaction.
+
+## Extension Interfaces
+
+The [`LLMClient`, `GenerateRequest`, and
+`GenerateResponse`](../../types.go) boundary lets a consumer replace model
+generation. Injected clients receive copied rendered messages, effective
+settings, explicit numeric-setting presence, structured-output constraints,
+and the request-scoped key. They return generated content and token usage.
+
+The [`ArtifactReader`](../../types.go) boundary replaces the default inline and
+file reader for every input. Readers provide artifact content and metadata; the
+engine fills an empty artifact name from the input-map key. A reader error
+matches `ErrArtifactLoad` while preserving the original identity for
+`errors.Is`. A nil artifact with a nil error is also an artifact-load failure.
+
+Extensions should honor context cancellation and avoid logging raw prompts,
+artifacts, or credentials.
+
+## Errors
+
+The [public error declarations](../../engine.go) and
+[mapping](../../errors.go) preserve these sentinel checks through `errors.Is`:
+
+- `ErrInvalidConfig`
+- `ErrInvalidRequest`
+- `ErrPromptNotFound`
+- `ErrProfileNotFound`
+- `ErrProfileRequired`
+- `ErrPromptLoad`
+- `ErrProfileLoad`
+- `ErrAPIKeyEnvMissing`
+- `ErrArtifactLoad`
+- `ErrPromptRender`
+- `ErrLLMGenerate`
+- `ErrValidation`
+
+`ErrProfileRequired` and `ErrAPIKeyEnvMissing` also match
+`ErrInvalidRequest`, allowing either broad request handling or a specific
+condition. Wrapped collaborator errors retain their identity where the public
+contract promises it.
+
+## Consumer Boundary
+
+Promptkit is an importable library. It does not own a command, inbound HTTP
+API, process configuration, or deployment policy. Scriptorium is one
+downstream application that maps this root package contract into those
+application concerns.

docs/development.md

@@ -31,11 +31,14 @@ Start with:
 
 | Task | Read before changing |
 | --- | --- |
-| Documentation or examples | The [documentation policy](policy/documentation.md) and the canonical owner of the affected contract. |
+| Root public API | The [architecture policy](policy/architecture.md), [consumer guide](consumers/pkg-promptkit.md), [testing policy](policy/testing.md), and existing GoDoc. |
-| Tests or test fixtures | The [testing policy](policy/testing.md), the owning package, and any focused internal document listed by the component overview. |
+| Prompt, profile, or schema formats | The [framework format reference](formats.md), owning parser or validator package, and [documentation policy](policy/documentation.md). |
-| Root public API, once implemented | The [architecture policy](policy/architecture.md), [root package declaration](../doc.go), [testing policy](policy/testing.md), and existing GoDoc. |
+| Source loading or validation | The [framework format reference](formats.md), [internal source document](internal/sources.md), and owning package tests. |
-| Internal package implementation, once introduced | The [architecture policy](policy/architecture.md), [internal component overview](internal/overview.md), and any focused internal document that the overview lists for that package. |
+| Model-client behavior | The [OpenAI-compatible integration contract](integrations/openai-compatible-chat.md), [internal model-client document](internal/llm.md), and owning package tests. |
-| Integration behavior, once introduced | The [architecture policy](policy/architecture.md), [documentation policy](policy/documentation.md), and the integration's owning contract under `docs/integrations/`. |
+| Internal package implementation | The [architecture policy](policy/architecture.md), [internal component overview](internal/overview.md), and focused internal document listed for that package. |
+| Tests or test fixtures | The [testing policy](policy/testing.md), owning package, and focused internal document listed by the component overview. |
+| Maintained example | The [example](../examples/go-library/prepare/main.go), [consumer guide](consumers/pkg-promptkit.md), [framework format reference](formats.md), and [documentation policy](policy/documentation.md). |
+| Documentation | The [documentation policy](policy/documentation.md) and canonical owner of every affected contract. |
 | Release preparation or publication | The [release procedure](release.md). |
 
 For cross-cutting changes, follow every applicable row. Do not create
@@ -50,8 +53,10 @@ validation from the Promptkit repository root:
 
 ```sh
 go test ./...
+go test -race ./...
 go vet ./...
 go build ./...
+go run ./examples/go-library/prepare
 ```
 
 Check formatting across every tracked Go file:
@@ -75,7 +80,7 @@ behavior checked by the module.
 ## Focused Validation
 
 Use focused checks while iterating, then run the complete validation sequence
-before accepting the change. The root package currently supports:
+before accepting the change. The root package supports:
 
 ```sh
 go test .
@@ -83,17 +88,16 @@ go vet .
 go build .
 ```
 
-Filter tests by name without assuming a future package layout:
+Filter tests by name without assuming a fixed internal package layout:
 
 ```sh
 go test ./... -run 'TestName'
 ```
 
-Replace `TestName` with a useful regular expression. When internal packages are
+Replace `TestName` with a useful regular expression. Target only paths that
-introduced, target only paths that actually exist, such as
+exist, and consult the internal component overview for their owning
-`go test ./path/to/package`, and consult the internal component overview for
+documentation. A filtered or package-specific run does not replace the
-their owning documentation. A filtered or package-specific run does not replace
+complete repository validation.
-the complete repository validation.
 
 ## Coordinated Work With Scriptorium
 

docs/formats.md

@@ -0,0 +1,276 @@
+# Framework Format Reference
+
+## Purpose
+
+This document is the canonical contract for Promptkit prompt-definition,
+profile, and schema files. The [Go package consumer guide](consumers/pkg-promptkit.md)
+explains how to select these sources and invoke the engine. The
+[OpenAI-compatible integration contract](integrations/openai-compatible-chat.md)
+owns the resulting outbound wire behavior.
+
+Prompt and profile sources recursively discover files ending in `.yaml` or
+`.yml`. YAML decoding is strict: unknown fields are errors for the selected
+definition. Definitions are selected by their YAML `id`, not their file name
+or directory.
+
+## Prompt Definitions
+
+A prompt definition describes inputs, Go-template messages, an optional
+default profile, and an output contract.
+
+```yaml
+id: meeting.summary
+version: "1.0.0"
+default_profile: local-summary
+description: Summarize a synthetic meeting note.
+session_id: '{{.session}}'
+inputs:
+  - name: note
+    required: true
+    content_type: text/plain
+    description: Meeting note to summarize.
+messages:
+  - role: system
+    content: Return a concise summary.
+    cache_control:
+      type: ephemeral
+      ttl: 1h
+  - role: user
+    content_file: ./summary.user.md
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+```
+
+| Field | Required | Meaning |
+| --- | --- | --- |
+| `id` | yes | Non-empty prompt identifier used by `RunRequest.PromptID`. |
+| `version` | yes | Non-empty version selected by an optional `RunRequest.PromptVersion`. |
+| `default_profile` | no | Non-empty profile ID used when the request omits `ProfileID`. |
+| `description` | no | Human-readable description. |
+| `session_id` | no | Go template rendered from request variables and input helpers. |
+| `inputs` | no | Declared input metadata. |
+| `messages` | yes | One or more chat-message templates. |
+| `output` | yes | Output format and validation settings. |
+
+When a request omits a version, the selected prompt ID must identify exactly
+one definition. When it supplies a version, the ID and version pair must be
+unique.
+
+### Inputs
+
+Each `inputs` item has these fields:
+
+| Field | Required | Meaning |
+| --- | --- | --- |
+| `name` | yes | Non-empty name used by the request input map and `input` template helper. Names must be unique. |
+| `required` | no | When true, preparation fails if the request omits the input. The default is false. |
+| `content_type` | no | Expected media-type metadata. |
+| `description` | no | Human-readable input description. |
+
+Requests supply inputs as inline or file-backed `ArtifactRef` values. Declared
+required inputs must be present. A template reference also requires the named
+input to exist, whether or not it was declared. Extra request inputs are
+allowed.
+
+### Messages And Templates
+
+Each message has a non-empty `role` and exactly one of:
+
+- `content`, containing an inline Go template; or
+- `content_file`, naming a file whose contents are the Go template.
+
+For directory and `fs.FS` prompt sources, `content_file` resolves relative to
+the prompt file and remains within the source root. `WithPromptFile` also
+resolves it relative to that file.
+
+Request variables are the template data, so a variable named `audience` is
+referenced as `{{.audience}}`. The `{{input "note"}}` helper renders the body
+of a named input. Missing variables and input references are errors.
+
+The optional `session_id` uses the same template data and input helper. Its
+rendered value is trimmed, omitted when empty, and limited to 256 Unicode code
+points.
+
+### Cache Control
+
+`cache_control` is optional and has these fields:
+
+| Field | Required | Values |
+| --- | --- | --- |
+| `type` | yes | `ephemeral` |
+| `ttl` | no | Empty or `1h` |
+
+Promptkit preserves cache-control metadata on the rendered message. The
+outbound integration determines its wire representation.
+
+### Output Contract
+
+| Field | Required | Values or behavior |
+| --- | --- | --- |
+| `format` | yes | `text`, `markdown`, or `json`. |
+| `validation_mode` | yes | `none`, `basic`, `json`, or `json_schema`. |
+| `schema_path` | for `json_schema` | Path to a schema in the configured schema source. |
+| `repair_attempts` | no | Integer zero or greater; omitted means zero. |
+
+The validation modes behave as follows:
+
+- `none` skips content validation;
+- `basic` requires non-empty generated content;
+- `json` requires valid JSON; and
+- `json_schema` requires valid JSON that satisfies the selected schema.
+
+`format` controls output artifact metadata. JSON Schema mode also supplies the
+schema to compatible model clients as structured-output metadata. The public
+engine does not install an output repairer, so its validation is single-pass
+even when a positive `repair_attempts` value is present.
+
+A request-level `OutputContract` replaces the complete prompt output contract.
+It does not merge individual fields. If its format is empty, Promptkit uses
+`text`.
+
+## Profile Definitions
+
+A profile supplies model execution settings:
+
+```yaml
+id: local-summary
+endpoint: http://localhost:8000/v1
+model: example-model
+temperature: 0.2
+max_tokens: 500
+top_p: 0.95
+timeout_seconds: 90
+service_tier: flex
+reasoning_effort: medium
+api_key_env: EXAMPLE_API_KEY
+extra_params:
+  provider_option: enabled
+```
+
+| Field | Required | Meaning |
+| --- | --- | --- |
+| `id` | yes | Non-empty profile identifier. IDs must be unique within one source. |
+| `endpoint` | yes | Non-empty OpenAI-compatible base URL, including an API version path when required. |
+| `model` | yes | Non-empty provider model name. |
+| `temperature` | no | Number from 0 through 2. |
+| `max_tokens` | no | Integer zero or greater. |
+| `top_p` | no | Number from 0 through 1. |
+| `timeout_seconds` | no | Per-generation deadline in whole seconds; integer zero or greater. |
+| `service_tier` | no | Provider-specific request tier. |
+| `reasoning_effort` | no | Provider-specific reasoning setting. |
+| `api_key_env` | no | Name of an environment variable containing the API key. |
+| `extra_params` | no | JSON-compatible provider-specific outbound fields. |
+
+Raw `api_key` is prohibited in profile YAML. Store only an environment
+variable name in `api_key_env`.
+
+`extra_params` accepts null, booleans, finite numbers, strings, arrays, and
+objects with string keys. Keys must be non-empty. With the built-in client,
+they also cannot collide with the standard fields listed in the
+[outbound request contract](integrations/openai-compatible-chat.md#request-body).
+
+### Defaults And Overrides
+
+Execution settings resolve in this order:
+
+1. framework defaults;
+2. the selected profile; and
+3. request `ExecutionTargetOverride` values.
+
+The framework defaults are:
+
+| Setting | Default |
+| --- | --- |
+| `temperature` | `0` |
+| `max_tokens` | `0` |
+| `top_p` | `1` |
+| `timeout_seconds` | `600` |
+
+Numeric zero in a file or in-memory profile means that the profile does not
+replace the framework default. Numeric request overrides use pointers, so an
+explicit zero is preserved. In particular, an explicit request
+`timeout_seconds` of zero disables the per-generation deadline while leaving
+the caller context and transport timeout intact.
+
+Non-empty request strings replace profile strings. A non-empty request
+`ExtraParams` map replaces the profile map rather than merging keys.
+The [outbound integration contract](integrations/openai-compatible-chat.md)
+defines how the effective settings are serialized.
+
+### Source And Profile Precedence
+
+An explicit request profile ID takes precedence over the prompt's
+`default_profile`. If neither is present, preparation fails.
+
+Profile sources resolve matching IDs in this order:
+
+1. in-memory profiles supplied with `WithProfiles`;
+2. a profile file, `fs.FS`, or configured profile directory; and
+3. embedded built-in profiles.
+
+A higher-precedence source falls back only when the profile is absent. An
+invalid matching profile is an error and does not fall back. In-memory
+`Profile` values follow the same ranges as YAML profiles. They use
+`APIKeyRequired` for request-scoped credentials instead of `api_key_env`.
+
+## Built-In Profile Catalog
+
+Built-ins use the OpenRouter-compatible endpoint and
+`OPENROUTER_API_KEY`. A custom or in-memory profile with the same ID takes
+precedence.
+
+| Provider | ID | Model |
+| --- | --- | --- |
+| aion-labs | `aion-2` | `aion-labs/aion-2.0` |
+| anthropic | `claude-fable-latest` | `~anthropic/claude-fable-latest` |
+| anthropic | `claude-haiku-latest` | `~anthropic/claude-haiku-latest` |
+| anthropic | `claude-opus-latest` | `~anthropic/claude-opus-latest` |
+| anthropic | `claude-sonnet-latest` | `~anthropic/claude-sonnet-latest` |
+| deepseek | `deepseek-3-2` | `deepseek/deepseek-v3.2` |
+| deepseek | `deepseek-4-flash` | `deepseek/deepseek-v4-flash` |
+| deepseek | `deepseek-4-pro` | `deepseek/deepseek-v4-pro` |
+| google | `gemini-2-flash` | `google/gemini-2.5-flash` |
+| google | `gemini-2-flash-lite` | `google/gemini-2.5-flash-lite` |
+| google | `gemini-2-pro` | `google/gemini-2.5-pro` |
+| google | `gemini-3-flash-lite` | `google/gemini-3.1-flash-lite` |
+| google | `gemini-flash-latest` | `~google/gemini-flash-latest` |
+| google | `gemini-pro-latest` | `~google/gemini-pro-latest` |
+| google | `gemma-4-31b` | `google/gemma-4-31b-it:exacto` |
+| minimax | `minimax-m2` | `minimax/minimax-m2.5` |
+| minimax | `minimax-m3` | `minimax/minimax-m3` |
+| mistral | `mistral-large-2512` | `mistralai/mistral-large-2512` |
+| mistral | `mistral-medium-3-5` | `mistralai/mistral-medium-3-5` |
+| mistral | `mistral-small-3` | `mistralai/mistral-small-3.2-24b-instruct` |
+| mistral | `mistral-small-4` | `mistralai/mistral-small-2603` |
+| nvidia | `nemotron-3-ultra` | `nvidia/nemotron-3-ultra-550b-a55b` |
+| openai | `gpt-5-mini` | `openai/gpt-5.4-mini` |
+| openai | `gpt-5-nano` | `openai/gpt-5.4-nano` |
+
+## Schemas
+
+Schemas are JSON documents selected by a prompt or request
+`schema_path`. For a directory or `fs.FS` source, paths resolve within the
+configured source root. Referenced nested schemas resolve relative to the
+owning schema document. `WithSchemaFile` exposes one schema, addressed by its
+base name.
+
+An unreadable, invalid, or unresolvable schema produces an operational
+validation error. Generated content that is valid JSON but does not satisfy the
+schema produces a failed validation result.
+
+## Credentials
+
+Credential values belong at the request or environment boundary, never in
+prompt, profile, schema, or example files:
+
+- a file profile names an environment variable with `api_key_env`;
+- an in-memory profile may set `APIKeyRequired`;
+- a request can provide a direct `APIKey` or override `APIKeyEnv`; and
+- a direct request key takes precedence over environment lookup.
+
+Promptkit validates required credential availability during preparation.
+Direct keys are excluded from JSON results and redacted by public string
+formatters. Environment-variable names may appear in prepared metadata, but
+their values do not.

docs/integrations/openai-compatible-chat.md

@@ -0,0 +1,88 @@
+# OpenAI-Compatible Chat Integration
+
+## Purpose
+
+This document defines the outbound HTTP behavior implemented by Promptkit's
+internal OpenAI-compatible model client. The
+[internal model-client document](../internal/llm.md) owns implementation flow,
+errors, and test ownership. The root Promptkit engine uses this client by
+default unless a consumer injects another implementation. The
+[framework format reference](../formats.md) owns the profile and prompt values
+that produce these outbound settings.
+
+## Endpoint And Method
+
+Generation sends an HTTP `POST` with `Content-Type: application/json`.
+A non-empty endpoint from the execution target overrides the client's
+configured base URL. After trailing slashes are removed,
+`/chat/completions` is appended. Generation fails before sending when neither
+source supplies an endpoint.
+
+## Authentication
+
+A non-empty API key supplied directly on the execution target takes
+precedence. Otherwise, when an API-key environment-variable name is supplied,
+the client reads that variable and requires a non-empty value. The selected
+key is sent as `Authorization: Bearer <key>`. No authorization header is sent
+when neither mechanism is configured.
+
+## Request Body
+
+The request body always contains `model` and `messages`. The execution
+target's model takes precedence over the client's configured model, and one
+must be available.
+
+Each ordinary message contains its `role` and string `content`. A
+cache-controlled message instead uses a text content block containing `type`,
+`text`, and `cache_control`; an empty cache-control TTL is omitted.
+
+A non-empty session ID is trimmed, checked against the internal domain limit,
+and sent as top-level `session_id`. It is not sent as a session header.
+
+The client conditionally includes:
+
+- `temperature`, `max_tokens`, and `top_p` when non-zero or explicitly
+  present;
+- non-empty `service_tier` and `reasoning_effort`; and
+- `response_format` for JSON Schema structured output, including its name,
+  strict flag, and schema document.
+
+Extra parameters are merged directly into the top-level body after JSON
+serialization is verified. Empty keys and collisions with these reserved
+fields are rejected before any provider call:
+
+- `model`
+- `session_id`
+- `messages`
+- `temperature`
+- `max_tokens`
+- `top_p`
+- `service_tier`
+- `reasoning_effort`
+- `response_format`
+
+## Response Handling
+
+Any 2xx response is decoded as an OpenAI-compatible chat response. The client
+returns the first choice's non-empty message content and maps prompt,
+completion, total, cached, and cache-write token counts.
+
+Invalid JSON, absent choices, and empty first-choice content are malformed
+responses. For a non-2xx status, the error includes the status code but never
+the provider response body.
+
+## Timeout And Cancellation
+
+Timeouts are layered:
+
+- the caller context remains the outer cancellation boundary;
+- a positive generation timeout adds a request context deadline;
+- zero adds no generation-specific deadline;
+- a negative generation timeout is invalid; and
+- the cloned `http.Client` supplies the whole-request transport cap, retaining
+  a positive supplied-client timeout or applying the configured/default
+  timeout when the supplied value is not positive.
+
+The earliest applicable caller, generation, or transport deadline controls the
+request. Constructing the internal client does not mutate a supplied
+`http.Client`.

docs/internal/llm.md

@@ -0,0 +1,55 @@
+# Internal Model Client
+
+## Purpose
+
+This document describes Promptkit's internal model-client implementation. The
+[architecture policy](../policy/architecture.md) owns the library boundary,
+and the
+[OpenAI-compatible chat integration](../integrations/openai-compatible-chat.md)
+owns the observable outbound HTTP contract. The
+[framework format reference](../formats.md) owns the profile and prompt
+settings consumed by the client.
+
+The concrete client remains under `internal/llm`. The root engine assembles it
+as the default implementation behind Promptkit's public client boundary.
+
+## Components And Flow
+
+`Client` is the provider-neutral generation boundary consumed by later
+orchestration. `OpenAICompatibleClient` is the built-in implementation. It
+uses internal domain values for rendered prompts, execution targets,
+structured output, responses, and token usage.
+
+Construction validates the configured base URL and clones any supplied
+`http.Client` so Promptkit can apply its timeout default without mutating the
+caller's client. Generation then:
+
+1. validates request-level timeout and endpoint requirements;
+2. maps the internal request into the OpenAI-compatible chat payload;
+3. validates and merges extra parameters;
+4. resolves authentication;
+5. performs the outbound request under the applicable deadlines; and
+6. decodes the first response choice and token usage.
+
+The implementation has no retry loop, tool-call support, provider catalog,
+inbound HTTP behavior, or durable session store.
+
+## Failure Categories
+
+The package preserves distinct error identities for invalid client
+configuration, invalid generation requests, request execution failures,
+non-success provider statuses, and malformed successful responses. Provider
+response bodies are not included in non-success errors.
+
+Caller cancellation and deadline failures during the outbound request are
+reported as request execution failures. The runner classifies these identities
+without depending on HTTP status mapping.
+
+## Test Ownership
+
+The
+[OpenAI-compatible client tests](../../internal/llm/openai_compatible_client_test.go)
+own configuration, client cloning, deterministic deadline precedence,
+authentication, request and response mapping, malformed data, error identity,
+cancellation, and response-body suppression. They use local test servers and
+test transports; the default suite makes no live or paid provider requests.

docs/internal/overview.md

@@ -11,14 +11,26 @@ contributor workflow and validation.
 
 | Component | Implemented responsibility | References |
 | --- | --- | --- |
-| Root `promptkit` package | Establishes the public package boundary for the Go module. It does not yet provide migrated framework behavior or exported APIs. | [Package declaration](../../doc.go) |
+| Root `promptkit` package | Provides the supported engine facade, source and injection options, public request and result values, built-in profile construction, extension interfaces, value conversion, redacted formatting, and public error mapping. | [Package GoDoc](../../doc.go), [engine assembly](../../engine.go) |
+| `examples/go-library/prepare` | Demonstrates an offline downstream consumer using a prompt file, in-memory profile, inline input, and `Prepare`. It is not a public library package. | [Example program](../../examples/go-library/prepare/main.go) |
+| `internal/domain` | Defines internal framework values for requests, artifacts, prompt definitions, profiles, execution targets, rendering, generation, and validation. | [Domain declarations](../../internal/domain/domain.go) |
+| `internal/defaults` | Defines application-neutral framework constants and constructs the default execution target. It contains no CLI, server, or inbound HTTP limits. | [Framework defaults](../../internal/defaults/defaults.go) |
+| `internal/filecatalog` | Provides deterministic YAML discovery and path helpers for operating-system filesystems and `fs.FS` sources. | [File catalog](../../internal/filecatalog/catalog.go) |
+| `internal/promptdef` | Loads strictly decoded, validated prompt definitions from filesystem and `fs.FS` sources, including version selection and contained file-backed message content. | [Framework formats](../formats.md), [prompt-definition repository](../../internal/promptdef/filesystem_repository.go) |
+| `internal/profile` | Loads strictly decoded, validated execution profiles from filesystem and `fs.FS` sources and composes repositories with error-preserving fallback. | [Framework formats](../formats.md), [profile repositories](../../internal/profile/filesystem_repository.go) |
+| `internal/profile/builtin` | Embeds the built-in execution profile catalog and combines it with an optional primary repository. | [Built-in catalog](../formats.md#built-in-profile-catalog), [repository](../../internal/profile/builtin/repository.go) |
+| `internal/prompt` | Renders prompt messages from Go templates with artifact, variable, session, and cache-control data. | [Go-template renderer](../../internal/prompt/go_renderer.go) |
+| `internal/artifact` | Resolves ordinary inline and unrestricted caller-selected file references into copied artifacts with metadata and hashes. | [Internal sources and validation](sources.md) |
+| `internal/validate` | Validates basic, JSON, and JSON Schema output using operating-system filesystem or `fs.FS` schema sources. | [Framework formats](../formats.md#schemas), [internal sources and validation](sources.md) |
+| `internal/llm` | Defines the internal generation boundary and implements outbound OpenAI-compatible chat requests, response decoding, authentication, and deadline handling. | [Internal model client](llm.md) |
+| `internal/usecase` | Coordinates preparation and execution across internal sources, rendering, artifact loading, generation, validation, and optional repair. | [Internal runner](runner.md) |
 
-The root `promptkit` package is the sole implemented Go package. No internal
+The root package assembles these internal components without exposing their
-framework packages exist yet.
+representations. Consumers depend only on the root facade.
 
 ## Maintenance
 
-Update this inventory as framework extraction introduces packages or changes
+Update this inventory as implementation adds packages or changes component
-component responsibilities. List only implemented components; proposed package
+responsibilities. List only implemented components; proposed package
 boundaries belong in temporary planning documents until their implementation
 lands.

docs/internal/runner.md

@@ -0,0 +1,85 @@
+# Internal Runner
+
+## Purpose
+
+This document describes Promptkit's implemented internal orchestration. The
+[architecture policy](../policy/architecture.md) owns dependency and consumer
+boundaries. The [source and validation document](sources.md) owns repository,
+artifact, rendering, and validation behavior, while the
+[model-client document](llm.md) owns generation behavior and failure
+categories.
+
+The runner remains under `internal/usecase` and is assembled by the root
+Promptkit engine. Its concrete type is not part of the public API.
+The [framework format reference](../formats.md) owns prompt, profile, schema,
+and override semantics consumed by the runner.
+
+## Collaborators
+
+`Runner` coordinates narrow internal interfaces for prompt definitions,
+profiles, artifacts, rendering, model generation, and validation. Schema
+documents are loaded through the validator's optional schema-loader interface.
+An output repairer can be injected internally, but the ordinary runner
+constructor does not enable one.
+
+Each invocation carries its state in request, prepared-run, and result values.
+The runner has no durable run or session store.
+
+## Preparation Flow
+
+`Prepare` performs the reusable pre-generation workflow:
+
+1. validate the prompt selection and load the prompt definition;
+2. hash the loaded definition;
+3. select the request profile or the prompt's default profile;
+4. resolve application-neutral defaults, profile values, and explicit request
+   overrides in that order;
+5. validate endpoint, model, numeric overrides, and credential requirements;
+6. resolve the output contract and load a structured-output schema when
+   required;
+7. load and hash input artifacts;
+8. render and hash the prompt; and
+9. return the effective settings, source identities, messages, hashes, and
+   preparation timing.
+
+Pointer-based numeric overrides preserve an explicit zero. Invalid negative or
+out-of-range values fail as invalid requests. A direct API key takes
+precedence over environment lookup for execution; secret values remain
+excluded from serialized metadata.
+
+## Run Flow
+
+`Run` calls `Prepare` rather than maintaining a second preparation path. It
+performs one initial generation call, builds the named output artifact, and
+validates that artifact. Invalid generated content remains a validation result;
+an inability to perform validation is an operational error.
+
+When an internal repairer is present, a JSON or JSON Schema content failure can
+trigger bounded repair attempts. Repair receives the effective execution
+target, validation errors, prior output, and structured-output specification.
+This capability remains internal and is not a public option.
+
+A successful result includes the output artifact and raw output, validation
+state, prompt and rendered-prompt hashes, selected profile, effective settings,
+input hashes, token usage, a generated run identifier, and UTC timing.
+
+## Failure Categories
+
+Package errors distinguish invalid requests, required profile selection,
+credential failures, and prompt, profile, artifact, rendering, generation, and
+validation failures. Wrapping preserves the package identities mapped by the
+public facade and retains collaborator identities where they are part of the
+internal contract. Context cancellation propagates through the invoked
+collaborator and is classified by the owning operation.
+
+## Test Ownership And Changes
+
+The [runner tests](../../internal/usecase/runner_test.go) own preparation order,
+selection and override precedence, schema-before-generation behavior, hashing,
+generation and validation outcomes, bounded repair, credentials and redaction,
+error categories, artifact metadata, usage, and timing.
+
+Changes to orchestration should continue to use the existing package
+interfaces, keep request state local to an invocation, and preserve `Run`'s use
+of `Prepare`. Source, renderer, validator, or model-client contract changes
+belong first in their owning package and document.

docs/internal/sources.md

@@ -0,0 +1,66 @@
+# Internal Sources And Validation
+
+## Purpose
+
+This document describes Promptkit's implemented internal source, artifact,
+rendering, and output-validation behavior. The
+[architecture policy](../policy/architecture.md) owns the library boundary and
+dependency rules. None of these internal packages is a supported consumer API,
+and the root engine assembles them behind its public source options and values.
+The [framework format reference](../formats.md) owns the exact file fields,
+validation modes, built-in catalog, and source precedence.
+
+## Prompt Definitions
+
+`internal/promptdef` discovers YAML deterministically, decodes and validates
+definitions, selects an ID and optional version, and resolves file-backed
+message content within the selected operating-system or `fs.FS` source.
+
+Its package tests own prompt selection, strict decoding, definition validation,
+duplicate detection, and source containment:
+[prompt-definition repository tests](../../internal/promptdef/repository_test.go).
+
+## Profiles And Built-Ins
+
+`internal/profile` loads and validates execution profiles from an
+operating-system filesystem or an `fs.FS`. It supports a primary repository
+with fallback only when the primary reports that a profile is absent.
+
+`internal/profile/builtin` embeds the maintained built-in profile catalog and
+can place a caller-selected repository ahead of that catalog. Profile behavior
+is owned by the
+[profile repository tests](../../internal/profile/repository_test.go), while
+catalog completeness, duplicate IDs, and overlay behavior are owned by the
+[built-in repository tests](../../internal/profile/builtin/repository_test.go).
+
+## Ordinary Artifacts
+
+`internal/artifact` resolves inline references and unrestricted,
+caller-selected file paths. It copies content into an artifact, records
+metadata and a content hash, applies a content-type fallback, and honors
+context cancellation.
+
+This ordinary reader does not implement an inbound HTTP security boundary. In
+particular, it does not constrain files to an application root or impose an
+HTTP request-size policy. Scriptorium's restricted HTTP reader remains an
+application concern outside Promptkit. The
+[artifact reader tests](../../internal/artifact/reader_test.go) own the
+implemented reader behavior and failures.
+
+## Rendering
+
+`internal/prompt` renders definition messages as Go templates using named
+artifacts and variables. It carries message roles, session IDs, and cache
+control into the rendered prompt. The
+[renderer tests](../../internal/prompt/renderer_test.go) own rendering behavior.
+
+## Schemas And Output Validation
+
+`internal/validate` provides validators backed by an operating-system
+filesystem or an `fs.FS`. Invalid generated content is returned as a validation
+result; inability to load, register, or compile a schema is an operational
+error.
+
+The [validator tests](../../internal/validate/standard_validator_test.go) own
+basic, JSON, JSON Schema, source resolution, schema loading, compilation, and
+content-failure behavior.

docs/policy/architecture.md

@@ -9,15 +9,55 @@ implemented packages without redefining these rules.
 
 ## System Shape
 
-Promptkit is an importable Go library. It does not provide a runnable command,
+Promptkit is an importable Go library. It does not ship a command, an HTTP
-an HTTP service, or another application process.
+service, or another application process. Repository examples demonstrate
+library use but are not Promptkit applications or release artifacts.
 
-The module root contains package `promptkit`, which is the public facade and the
+The module root contains package `promptkit`, which is the public facade. It
-only implemented Go package in the current repository foundation. It declares
+provides the supported engine, configuration and source options, requests,
-the module's public package boundary but does not yet provide migrated framework
+results, public values, extension interfaces, profiles, and error sentinels.
-behavior or exported APIs. No internal framework packages currently exist.
 
-Future framework extraction must follow this dependency direction:
+The implemented internal components consist of:
+
+- `internal/domain`, which owns framework data values shared by later internal
+  components;
+- `internal/defaults`, which owns application-neutral framework defaults and
+  constructs the default execution target;
+- `internal/filecatalog`, which discovers YAML files and provides source-path
+  helpers for filesystem and `fs.FS` consumers;
+- `internal/promptdef`, which loads and validates prompt definitions from
+  filesystem and `fs.FS` sources;
+- `internal/profile`, which loads, validates, and overlays execution profiles
+  from filesystem and `fs.FS` sources;
+- `internal/profile/builtin`, which embeds the built-in execution profile
+  catalog;
+- `internal/prompt`, which renders prompt messages from Go templates;
+- `internal/artifact`, which resolves ordinary inline and unrestricted
+  caller-selected file references;
+- `internal/validate`, which validates basic, JSON, and JSON Schema output
+  using filesystem and `fs.FS` schema sources;
+- `internal/llm`, which defines the provider-neutral generation boundary and
+  implements outbound OpenAI-compatible chat requests; and
+- `internal/usecase`, which coordinates preparation and execution across the
+  internal framework components.
+
+The `examples/go-library/prepare` package is a maintained downstream consumer
+of the root facade. It does not expose a library package or participate in
+internal assembly.
+
+The root facade assembles the internal repositories, renderer, validator,
+outbound client, and use-case runner while translating public values and
+errors at the library boundary. The defaults and renderer depend on the domain
+model. Prompt-definition and profile repositories use the domain model, file
+catalog, and YAML decoder. The built-in profile repository supplies an
+embedded `fs.FS` to the profile package. Artifact reading uses the domain model
+and application-neutral defaults. Validation uses the domain model, file
+catalog, and JSON Schema implementation. The model client uses the domain
+model, application-neutral defaults, and an injected or standard-library HTTP
+client. The use-case runner depends on the narrow interfaces owned by each
+internal component.
+
+The current implementation follows this dependency direction:
 
 ```text
 downstream consumers, including Scriptorium
@@ -32,14 +72,13 @@ downstream consumers, including Scriptorium
         narrow injected abstractions
 ```
 
-The facade may coordinate internal components. Internal components must depend
+The facade coordinates internal components and adapts the supported public
-on narrow abstractions for behavior supplied from outside the library; they
+extension interfaces to narrow internal abstractions. Internal components must
-must not depend on consumers or on Scriptorium. This diagram constrains future
+not depend on consumers or on Scriptorium.
-work and does not assert that the internal components already exist.
 
 ## Repository And Consumer Boundary
 
-Scriptorium is a downstream application that will consume Promptkit through
+Scriptorium is a downstream application that consumes Promptkit through
 the supported public facade. It is not a Promptkit package and must not become
 an internal dependency.
 
@@ -112,7 +151,6 @@ state.
 
 ## Current-State Maintenance
 
-This policy distinguishes present implementation from constraints on future
+Do not list planned packages as implemented components. When implementation
-framework extraction. Do not list planned packages as implemented components.
+introduces a package, update the internal inventory and the owning contract or
-When extraction introduces a package, update the internal inventory and the
+subsystem document in the same change.
-owning contract or subsystem document in the same change.

docs/policy/documentation.md

@@ -75,13 +75,14 @@ mechanisms, not secret values.
 | Testing policy | `docs/policy/testing.md` | Test philosophy, risk-based sufficiency, test boundaries, doubles, coverage guidance, regression policy, and test maintenance. | Subsystem behavior, exact public contracts, subsystem-specific test inventories, and implementation plans. |
 | Release procedure | `docs/release.md`, when present | Required release validation, version and tag procedure, release ordering, and post-publication checks. | General contributor workflow, public API semantics, and decision history. |
 | Exact exported Go API | Go declarations and GoDoc, as APIs are implemented | Exported names, signatures, types, values, errors, and exact behavioral contracts. | Task-oriented consumer walkthroughs, implementation details, and future API proposals. |
+| Framework file formats | `docs/formats.md` | Prompt-definition and profile YAML fields, schema references, defaults, validation modes, built-in profiles, credentials, and file-to-request precedence. | Exported Go declarations, outbound wire behavior, internal parsing mechanics, and application configuration. |
 | Consumer guidance | `docs/consumers/`, when consumer workflows require dedicated guidance | Task-oriented use of implemented public APIs, minimal examples, and consumer responsibilities. | Exact exported declarations and internal mechanics. |
 | Durable integration contracts | `docs/integrations/`, when integrations exist | External formats and protocols, compatibility behavior, and upstream or downstream responsibilities. | Internal transformations and public Go declarations. |
 | Implemented component inventory | `docs/internal/overview.md` | Current packages and components, their implemented responsibilities, and links to focused internal documents. | Normative architecture, contributor workflow, external contracts, and proposed components. |
 | Internal subsystem behavior | Other files under `docs/internal/`, when a subsystem needs durable detail | Implementation flow, internal collaborators and state transitions, package-local guarantees and failures, and relevant tests. | Global architecture invariants, public API definitions, and future package plans. |
 | Architectural decision history | `docs/adr/`, when repository-local decisions require records | Significant decisions, context, alternatives, rationale, consequences, and supersession history. | Current behavior reference, implementation status, and task sequencing. |
 | Temporary feature roadmaps | `docs/roadmap/`, while planned work needs coordination | Proposed or accepted scope, sequencing, gates, and implementation status. | Implemented behavior reference and durable decision rationale. |
-| Complete copyable artifacts | `examples/`, when maintained examples exist | Valid inputs, Go programs, and other files intended to be copied or run. | Field-by-field reference, exact API declarations, and prose explanation. |
+| Complete copyable artifacts | `examples/` | Valid inputs, Go programs, and other files intended to be copied or run. | Field-by-field reference, exact API declarations, and prose explanation. |
 
 Conditional owners do not require placeholder files or directories. Create a
 consumer, integration, subsystem, ADR, roadmap, or example document only when
@@ -105,6 +106,9 @@ for a task. Internal documents explain how Promptkit implements them. Internal
 documentation may identify a public type or external format as a dependency,
 but must link to its canonical definition rather than restate it.
 
+The [framework format reference](../formats.md) owns exact prompt, profile, and
+schema-file contracts. Integration documents own external wire formats.
+
 ### Security Topics
 
 This policy owns what documentation and examples may contain. Architecture owns

docs/policy/testing.md

@@ -55,6 +55,15 @@ documentation-link, and repository-hygiene checks before accepting changes.
 Introducing hosted CI later would supplement, not silently redefine, this
 documented validation model.
 
+The complete test sequence includes ordinary and race-enabled package tests.
+The maintained offline consumer workflow is also run from the repository root:
+
+```sh
+go test ./...
+go test -race ./...
+go run ./examples/go-library/prepare
+```
+
 Tests in the default suite must be deterministic, offline, and independent of
 real credentials. They must not invoke paid APIs, use live network
 dependencies, or depend on mutable external services. Tests that require live
@@ -77,6 +86,10 @@ Use each test type where it protects a distinct risk:
   relied upon by consumers.
 - Integration tests use real collaborators when correctness depends on their
   interaction, while replacing live or nondeterministic external boundaries.
+- External-package root tests exercise the public facade as a Go consumer,
+  while internal package tests own focused implementation behavior.
+- The maintained offline preparation example protects one representative
+  assembled consumer workflow without contacting a model provider.
 - Fixtures should be minimal, synthetic, versioned with the behavior they
   exercise, and free of credentials or private data.
 - Golden files are appropriate only when the complete output is intentionally
@@ -154,7 +167,8 @@ A test failing is not the same as a test needing to be edited. Many tests may co
 
 Configurable thresholds and defaults must not be duplicated throughout the test suite.
 
-For example, do not encode an internal concurrency limit indirectly:
+The following fragments are illustrative rather than standalone Go programs.
+Do not encode an internal concurrency limit indirectly:
 
 ```go
 // Production policy:

docs/release.md

@@ -47,8 +47,10 @@ Run the same default Go validation required by the
 
 ```sh
 go test ./...
+go test -race ./...
 go vet ./...
 go build ./...
+go run ./examples/go-library/prepare
 ```
 
 Check every tracked Go file and repository whitespace:

engine.go

@@ -0,0 +1,342 @@
+package promptkit
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	artifactadapter "gitea.maximumdirect.net/eric/promptkit/internal/artifact"
+	"gitea.maximumdirect.net/eric/promptkit/internal/defaults"
+	"gitea.maximumdirect.net/eric/promptkit/internal/llm"
+	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
+	"gitea.maximumdirect.net/eric/promptkit/internal/profile/builtin"
+	"gitea.maximumdirect.net/eric/promptkit/internal/prompt"
+	"gitea.maximumdirect.net/eric/promptkit/internal/promptdef"
+	"gitea.maximumdirect.net/eric/promptkit/internal/usecase"
+	"gitea.maximumdirect.net/eric/promptkit/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")
+	ErrProfileRequired  = errors.New("profile selection is required")
+	ErrPromptLoad       = errors.New("failed to load prompt definition")
+	ErrProfileLoad      = errors.New("failed to load execution profile")
+	ErrAPIKeyEnvMissing = errors.New("api_key_env points to an unset environment variable")
+	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 Promptkit prompt requests.
+type Engine struct {
+	runner *usecase.Runner
+}
+
+// Config configures a public Promptkit engine.
+type Config struct {
+	PromptDir  string
+	ProfileDir string
+	SchemaDir  string
+	// Timeout is the transport-wide safety cap for the built-in LLM client
+	// when HTTPClient is absent or has a non-positive timeout.
+	Timeout time.Duration
+	// HTTPClient is cloned for the built-in LLM client. Its positive Timeout
+	// takes precedence over Config.Timeout as the transport-wide safety cap.
+	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
+	artifactReader  artifactadapter.Reader
+	promptDefs      promptdef.Repository
+	profiles        profile.Repository
+	memoryProfiles  profile.Repository
+	validator       validate.Validator
+	promptSource    bool
+	profileSource   bool
+	memorySource    bool
+	validatorSource bool
+	artifactSource  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
+	})
+}
+
+// WithArtifactReader injects a reader for every input artifact reference.
+func WithArtifactReader(reader ArtifactReader) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if reader == nil {
+			return ErrInvalidConfig
+		}
+		options.artifactReader = publicArtifactReaderAdapter{reader: reader}
+		options.artifactSource = true
+		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 from configuration and options.
+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)
+		}
+	}
+
+	artifacts := options.artifactReader
+	if !options.artifactSource {
+		artifacts = artifactadapter.NewCompositeReader()
+	}
+
+	return &Engine{
+		runner: usecase.NewRunner(
+			promptDefs,
+			profiles,
+			artifacts,
+			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 +1,60 @@
+package promptkit
+
+import (
+	"errors"
+	"fmt"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
+	"gitea.maximumdirect.net/eric/promptkit/internal/promptdef"
+	"gitea.maximumdirect.net/eric/promptkit/internal/usecase"
+)
+
+func mapPublicError(err error) error {
+	if err == nil {
+		return nil
+	}
+	publicErr := publicErrorFor(err)
+	if publicErr == nil {
+		return err
+	}
+	return fmt.Errorf("%w: %w", publicErr, err)
+}
+
+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.ErrProfileRequired):
+		return errors.Join(ErrInvalidRequest, ErrProfileRequired)
+	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.ErrAPIKeyEnvMissing):
+		return errors.Join(ErrInvalidRequest, ErrAPIKeyEnvMissing)
+	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/go-library/prepare/main.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+
+	"gitea.maximumdirect.net/eric/promptkit"
+)
+
+type summary struct {
+	PromptID        string `json:"prompt_id"`
+	PromptVersion   string `json:"prompt_version"`
+	SelectedProfile string `json:"selected_profile"`
+	Model           string `json:"model"`
+	MessageCount    int    `json:"message_count"`
+}
+
+func main() {
+	engine, err := promptkit.NewEngine(
+		promptkit.Config{},
+		promptkit.WithPromptFile("examples/go-library/prepare/prompt.yaml"),
+		promptkit.WithProfiles(promptkit.Profile{
+			ID:       "offline-example",
+			Endpoint: "https://example.invalid/v1",
+			Model:    "offline-model",
+		}),
+	)
+	if err != nil {
+		exit(err)
+	}
+
+	prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{
+		PromptID: "example.prepare",
+		Inputs: map[string]promptkit.ArtifactRef{
+			"note": promptkit.Inline("Ada finished the migration review."),
+		},
+	})
+	if err != nil {
+		exit(err)
+	}
+
+	encoder := json.NewEncoder(os.Stdout)
+	encoder.SetIndent("", "  ")
+	if err := encoder.Encode(summary{
+		PromptID:        prepared.PromptID,
+		PromptVersion:   prepared.PromptVersion,
+		SelectedProfile: prepared.SelectedProfileID,
+		Model:           prepared.EffectiveModelParams.Model,
+		MessageCount:    len(prepared.Messages),
+	}); err != nil {
+		exit(err)
+	}
+}
+
+func exit(err error) {
+	fmt.Fprintln(os.Stderr, err)
+	os.Exit(1)
+}

examples/go-library/prepare/prompt.yaml

@@ -0,0 +1,16 @@
+id: example.prepare
+version: "1.0.0"
+default_profile: offline-example
+description: Prepare a prompt without contacting a model provider.
+inputs:
+  - name: note
+    required: true
+    content_type: text/plain
+messages:
+  - role: system
+    content: Summarize the note in one sentence.
+  - role: user
+    content: '{{input "note"}}'
+output:
+  format: text
+  validation_mode: basic

formatting.go

@@ -0,0 +1,51 @@
+package promptkit
+
+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(
+		"promptkit.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(
+		"promptkit.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),
+	)
+}

go.mod

@@ -1,3 +1,10 @@
 module gitea.maximumdirect.net/eric/promptkit
 
 go 1.25.5
+
+require (
+	github.com/santhosh-tekuri/jsonschema/v6 v6.0.2
+	gopkg.in/yaml.v3 v3.0.1
+)
+
+require golang.org/x/text v0.14.0 // indirect

go.sum

@@ -0,0 +1,10 @@
+github.com/dlclark/regexp2 v1.11.0 h1:G/nrcoOa7ZXlpoa/91N3X7mM3r8eIlMBBJZvsz/mxKI=
+github.com/dlclark/regexp2 v1.11.0/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
+github.com/santhosh-tekuri/jsonschema/v6 v6.0.2 h1:KRzFb2m7YtdldCEkzs6KqmJw4nqEVZGK7IN2kJkjTuQ=
+github.com/santhosh-tekuri/jsonschema/v6 v6.0.2/go.mod h1:JXeL+ps8p7/KNMjDQk3TCwPpBy0wYklyWTfbkIzdIFU=
+golang.org/x/text v0.14.0 h1:ScX5w1eTa3QqT8oi6+ziP7dTV1S2+ALU0bI+0zXKWiQ=
+golang.org/x/text v0.14.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/artifact/reader.go

@@ -0,0 +1,122 @@
+package artifact
+
+import (
+	"context"
+	"crypto/sha256"
+	"errors"
+	"fmt"
+	"io"
+	"mime"
+	"os"
+	"path/filepath"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/defaults"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+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")
+)
+
+// Reader resolves artifact references into actual artifacts.
+type Reader interface {
+	Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error)
+}
+
+// CompositeReader routes artifact resolution based on the reference type.
+type CompositeReader struct {
+	inlineReader *inlineReader
+	fileReader   Reader
+}
+
+func NewCompositeReader() Reader {
+	return &CompositeReader{
+		inlineReader: &inlineReader{},
+		fileReader:   &fileReader{},
+	}
+}
+
+func (c *CompositeReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	switch ref.Type {
+	case domain.ArtifactRefInline:
+		return c.inlineReader.Read(ctx, ref)
+	case domain.ArtifactRefFile:
+		return c.fileReader.Read(ctx, ref)
+	default:
+		return nil, fmt.Errorf("%w: %s", ErrUnsupportedRefType, ref.Type)
+	}
+}
+
+type inlineReader struct{}
+
+func (r *inlineReader) Read(ctx context.Context, ref domain.ArtifactRef) (*domain.Artifact, error) {
+	select {
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	default:
+	}
+
+	if ref.Body == "" {
+		return nil, ErrMissingInlineBody
+	}
+
+	body := []byte(ref.Body)
+	return &domain.Artifact{
+		ContentType: defaults.ContentTypeTextPlain,
+		Body:        body,
+		Size:        int64(len(body)),
+		Hash:        fmt.Sprintf("%x", sha256.Sum256(body)),
+		URI:         ref.URI,
+	}, nil
+}
+
+type fileReader struct{}
+
+func (r *fileReader) 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 readFileArtifact(ref.URI)
+}
+
+func readFileArtifact(path string) (*domain.Artifact, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+	defer file.Close()
+
+	data, err := io.ReadAll(file)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read file %s: %w", path, err)
+	}
+
+	contentType := mime.TypeByExtension(filepath.Ext(path))
+	if contentType == "" {
+		contentType = defaults.ContentTypeTextPlain
+	}
+
+	return &domain.Artifact{
+		Name:        filepath.Base(path),
+		ContentType: contentType,
+		Body:        data,
+		URI:         path,
+		Size:        int64(len(data)),
+		Hash:        fmt.Sprintf("%x", sha256.Sum256(data)),
+	}, nil
+}

internal/artifact/reader_test.go

@@ -0,0 +1,180 @@
+package artifact
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestCompositeReader_Read(t *testing.T) {
+	reader := NewCompositeReader()
+	ctx := context.Background()
+
+	t.Run("inline artifact", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefInline,
+			Body: "hello world",
+		}
+		art, err := reader.Read(ctx, ref)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if string(art.Body) != "hello world" {
+			t.Errorf("expected 'hello world', got %s", string(art.Body))
+		}
+		if art.ContentType != "text/plain" {
+			t.Errorf("expected text/plain content type, got %q", art.ContentType)
+		}
+		if art.Hash != "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9" {
+			t.Errorf("unexpected hash: %s", art.Hash)
+		}
+		if art.Size != int64(len(ref.Body)) {
+			t.Errorf("expected size %d, got %d", len(ref.Body), art.Size)
+		}
+	})
+
+	t.Run("inline artifact missing body", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefInline,
+			Body: "",
+		}
+		_, err := reader.Read(ctx, ref)
+		if !errors.Is(err, ErrMissingInlineBody) {
+			t.Errorf("expected ErrMissingInlineBody, got %v", err)
+		}
+	})
+
+	t.Run("unsupported ref type", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefType("unsupported"),
+			URI:  "unsupported://bucket/key",
+		}
+		_, err := reader.Read(ctx, ref)
+		if !errors.Is(err, ErrUnsupportedRefType) {
+			t.Error("expected error for unsupported type")
+		}
+	})
+}
+
+func TestCompositeReaderCopiesInlineData(t *testing.T) {
+	reader := NewCompositeReader()
+	ref := domain.ArtifactRef{
+		Type: domain.ArtifactRefInline,
+		Body: "hello",
+		URI:  "inline:greeting",
+	}
+
+	first, err := reader.Read(context.Background(), ref)
+	if err != nil {
+		t.Fatalf("read first artifact: %v", err)
+	}
+	first.Body[0] = 'j'
+
+	second, err := reader.Read(context.Background(), ref)
+	if err != nil {
+		t.Fatalf("read second artifact: %v", err)
+	}
+	if got := string(second.Body); got != ref.Body {
+		t.Fatalf("expected an independent body %q, got %q", ref.Body, got)
+	}
+	if second.URI != ref.URI {
+		t.Fatalf("expected URI %q, got %q", ref.URI, second.URI)
+	}
+}
+
+func TestCompositeReaderHonorsCancellation(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	_, err := NewCompositeReader().Read(ctx, domain.ArtifactRef{
+		Type: domain.ArtifactRefInline,
+		Body: "ignored",
+	})
+	if !errors.Is(err, context.Canceled) {
+		t.Fatalf("expected context cancellation, got %v", err)
+	}
+}
+
+func TestFileReader_Read(t *testing.T) {
+	content := []byte("test file content")
+	filePath := filepath.Join(t.TempDir(), "artifact.txt")
+	if err := os.WriteFile(filePath, content, 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	reader := NewCompositeReader()
+	ctx := context.Background()
+
+	t.Run("file artifact loading", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefFile,
+			URI:  filePath,
+		}
+		art, err := reader.Read(ctx, ref)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if string(art.Body) != string(content) {
+			t.Errorf("expected %s, got %s", string(content), string(art.Body))
+		}
+		if art.Name != filepath.Base(filePath) {
+			t.Errorf("expected name %q, got %q", filepath.Base(filePath), art.Name)
+		}
+		if !strings.HasPrefix(art.ContentType, "text/plain") {
+			t.Errorf("expected text content type, got %q", art.ContentType)
+		}
+		if art.URI != filePath {
+			t.Errorf("expected URI %q, got %q", filePath, art.URI)
+		}
+		if art.Size != int64(len(content)) {
+			t.Errorf("expected size %d, got %d", len(content), art.Size)
+		}
+		if art.Hash != "60f5237ed4049f0382661ef009d2bc42e48c3ceb3edb6600f7024e7ab3b838f3" {
+			t.Errorf("unexpected hash: %s", art.Hash)
+		}
+	})
+
+	t.Run("missing file path", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefFile,
+			URI:  "",
+		}
+		_, err := reader.Read(ctx, ref)
+		if !errors.Is(err, ErrMissingFilePath) {
+			t.Errorf("expected ErrMissingFilePath, got %v", err)
+		}
+	})
+
+	t.Run("missing file", func(t *testing.T) {
+		ref := domain.ArtifactRef{
+			Type: domain.ArtifactRefFile,
+			URI:  filepath.Join(t.TempDir(), "missing.txt"),
+		}
+		if _, err := reader.Read(ctx, ref); err == nil {
+			t.Fatal("expected missing file error")
+		}
+	})
+
+	t.Run("unknown extension uses text fallback", func(t *testing.T) {
+		path := filepath.Join(t.TempDir(), "artifact.unknownextension")
+		if err := os.WriteFile(path, content, 0o600); err != nil {
+			t.Fatal(err)
+		}
+
+		art, err := reader.Read(ctx, domain.ArtifactRef{
+			Type: domain.ArtifactRefFile,
+			URI:  path,
+		})
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if art.ContentType != "text/plain" {
+			t.Errorf("expected text/plain fallback, got %q", art.ContentType)
+		}
+	})
+}

internal/defaults/defaults.go

@@ -0,0 +1,34 @@
+package defaults
+
+import (
+	"time"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+const (
+	SchemaDirDefault           = "."
+	OutputArtifactName         = "output"
+	ContentTypeTextPlain       = "text/plain"
+	ContentTypeTextMarkdown    = "text/markdown"
+	ContentTypeApplicationJSON = "application/json"
+	OpenAIChatCompletionsPath  = "/chat/completions"
+
+	ExecutionDefaultTemperature    = 0.0
+	ExecutionDefaultMaxTokens      = 0
+	ExecutionDefaultTopP           = 1.0
+	ExecutionDefaultTimeoutSeconds = 600
+)
+
+var (
+	LLMRequestTimeoutDefault = 10 * time.Minute
+)
+
+func ExecutionTargetDefault() domain.ExecutionTarget {
+	return domain.ExecutionTarget{
+		Temperature:    ExecutionDefaultTemperature,
+		MaxTokens:      ExecutionDefaultMaxTokens,
+		TopP:           ExecutionDefaultTopP,
+		TimeoutSeconds: ExecutionDefaultTimeoutSeconds,
+	}
+}

internal/domain/domain.go

@@ -0,0 +1,288 @@
+package domain
+
+import (
+	"time"
+)
+
+// ArtifactRefType defines how an artifact is referenced.
+type ArtifactRefType string
+
+const (
+	ArtifactRefInline ArtifactRefType = "inline"
+	ArtifactRefFile   ArtifactRefType = "file"
+)
+
+// OutputFormat defines the desired format of the generated artifact.
+type OutputFormat string
+
+const (
+	FormatText     OutputFormat = "text"
+	FormatMarkdown OutputFormat = "markdown"
+	FormatJSON     OutputFormat = "json"
+)
+
+// ValidationMode defines how the output should be validated.
+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"
+)
+
+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     *ExecutionTargetOverride
+	Validation    *OutputContract
+	Metadata      map[string]string
+}
+
+// RunResult represents the complete result of a prompt execution run.
+type RunResult struct {
+	RunID                string
+	Artifact             Artifact
+	RawOutput            string
+	Validation           ValidationResult
+	PromptID             string
+	PromptVersion        string
+	PromptHash           string
+	RenderedPromptHash   string
+	SelectedProfileID    string
+	ModelName            string
+	Endpoint             string
+	EffectiveModelParams ExecutionTarget
+	InputHashes          map[string]string
+	Usage                TokenUsage
+	StartTime            time.Time
+	EndTime              time.Time
+	Duration             time.Duration
+}
+
+// PreparedRun contains pre-LLM execution state from the prepare/render phase.
+// It must never include resolved API key values, model output, or validation data.
+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"`
+	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"`
+	EndTime              time.Time               `json:"end_time,omitempty"`
+	DurationMS           int64                   `json:"duration_ms,omitempty"`
+}
+
+// ArtifactRef represents a reference to an input artifact.
+type ArtifactRef struct {
+	Type ArtifactRefType
+	URI  string
+	Body string // Used for inline
+}
+
+// Artifact represents the actual loaded content of a reference.
+type Artifact struct {
+	Name        string
+	ContentType string
+	Body        []byte
+	URI         string
+	Size        int64
+	Hash        string
+}
+
+// PromptDefinition represents a configured prompt execution definition.
+type PromptDefinition struct {
+	ID             string                  `yaml:"id"`
+	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"`
+	Validation     OutputContract          `yaml:"validation"`
+}
+
+// PromptInput describes one named input expected by a prompt definition.
+type PromptInput struct {
+	Name        string `yaml:"name"`
+	Required    bool   `yaml:"required"`
+	ContentType string `yaml:"content_type"`
+	Description string `yaml:"description"`
+}
+
+// PromptMessageTemplate defines a template for a chat message.
+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.
+type ExecutionProfile struct {
+	ID              string         `yaml:"id"`
+	Endpoint        string         `yaml:"endpoint"`
+	Model           string         `yaml:"model"`
+	Temperature     float64        `yaml:"temperature"`
+	MaxTokens       int            `yaml:"max_tokens"`
+	TopP            float64        `yaml:"top_p"`
+	TimeoutSeconds  int            `yaml:"timeout_seconds"`
+	ServiceTier     string         `yaml:"service_tier"`
+	ReasoningEffort string         `yaml:"reasoning_effort"`
+	APIKeyEnv       string         `yaml:"api_key_env"`
+	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.
+type ExecutionTarget struct {
+	Endpoint        string         `yaml:"endpoint" json:"endpoint"`
+	Model           string         `yaml:"model" json:"model"`
+	Temperature     float64        `yaml:"temperature" json:"temperature"`
+	MaxTokens       int            `yaml:"max_tokens" json:"max_tokens"`
+	TopP            float64        `yaml:"top_p" json:"top_p"`
+	TimeoutSeconds  int            `yaml:"timeout_seconds" json:"timeout_seconds"`
+	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"`
+	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.
+type OutputContract struct {
+	Format         OutputFormat   `yaml:"format"`
+	ValidationMode ValidationMode `yaml:"validation_mode"`
+	SchemaPath     string         `yaml:"schema_path"`
+	RepairAttempts int            `yaml:"repair_attempts"`
+}
+
+// RenderedPrompt represents the prompt after template application.
+type RenderedPrompt struct {
+	SessionID string            `json:"session_id,omitempty"`
+	Messages  []RenderedMessage `json:"messages"`
+}
+
+// RenderedMessage is a single message in a rendered prompt.
+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
+}
+
+// StructuredOutputType indicates which provider-level output mode is requested.
+type StructuredOutputType string
+
+const (
+	StructuredOutputJSONSchema StructuredOutputType = "json_schema"
+)
+
+// StructuredOutputSpec describes provider-level structured output requirements.
+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"`
+}
+
+// GenerateResponse is the response received from the LLM client.
+type GenerateResponse struct {
+	Content string
+	Usage   TokenUsage
+}
+
+// TokenUsage tracks token consumption.
+type TokenUsage struct {
+	PromptTokens     int
+	CompletionTokens int
+	TotalTokens      int
+	CachedTokens     int
+	CacheWriteTokens int
+}
+
+// ValidationResult represents the outcome of an output validation.
+type ValidationResult struct {
+	Status         ValidationStatus
+	Mode           ValidationMode
+	Errors         []string
+	SchemaPath     string
+	RepairAttempts int
+	IsValid        bool
+}

internal/domain/prepared_run_test.go

@@ -0,0 +1,141 @@
+package domain
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestPreparedRunJSONDoesNotIncludeSecretValues(t *testing.T) {
+	const envName = "PROMPTKIT_TEST_API_KEY"
+	const secret = "super-secret-value"
+	t.Setenv(envName, secret)
+
+	prepared := PreparedRun{
+		PromptID:          "prompt.id",
+		PromptVersion:     "v1",
+		PromptHash:        "prompt-hash",
+		SelectedProfileID: "local-fast",
+		EffectiveModelParams: ExecutionTarget{
+			Endpoint:  "http://llm/v1",
+			Model:     "gpt-test",
+			APIKeyEnv: envName,
+			APIKey:    secret,
+		},
+		InputHashes:        map[string]string{"transcript": "hash-1"},
+		RenderedPromptHash: "rendered-hash",
+		Messages: []RenderedMessage{
+			{Role: "system", Content: "You are helpful."},
+			{Role: "user", Content: "Summarize this."},
+		},
+	}
+
+	b, err := json.Marshal(prepared)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+
+	out := string(b)
+	if strings.Contains(out, secret) {
+		t.Fatalf("prepared run JSON unexpectedly contains secret value: %s", out)
+	}
+	if !strings.Contains(out, `"api_key_env":"`+envName+`"`) {
+		t.Fatalf("prepared run JSON should include api_key_env name: %s", out)
+	}
+
+	var top map[string]any
+	if err := json.Unmarshal(b, &top); err != nil {
+		t.Fatalf("unmarshal failed: %v", err)
+	}
+
+	for _, forbidden := range []string{"raw_output", "validation", "artifact"} {
+		if _, ok := top[forbidden]; ok {
+			t.Fatalf("prepared run JSON should not include %q", forbidden)
+		}
+	}
+}
+
+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

@@ -0,0 +1,142 @@
+package filecatalog
+
+import (
+	"context"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// FindYAMLFiles returns sorted full paths for .yaml and .yml files under root.
+func FindYAMLFiles(ctx context.Context, root string) ([]string, error) {
+	var files []string
+	err := filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		default:
+		}
+		if d.IsDir() {
+			return nil
+		}
+		if !IsYAMLFile(d.Name()) {
+			return nil
+		}
+		files = append(files, path)
+		return nil
+	})
+	sort.Strings(files)
+	return files, err
+}
+
+// FindFSYAMLFiles returns sorted paths for .yaml and .yml files under root in fsys.
+func FindFSYAMLFiles(ctx context.Context, fsys fs.FS, root string) ([]string, error) {
+	cleanRoot := CleanFSRoot(root)
+	var files []string
+	err := fs.WalkDir(fsys, cleanRoot, func(name string, d fs.DirEntry, err error) error {
+		if err != nil {
+			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")
+	name = strings.TrimSuffix(name, ".yml")
+	return name
+}
+
+func IsYAMLFile(name string) bool {
+	return strings.HasSuffix(name, ".yaml") || strings.HasSuffix(name, ".yml")
+}

internal/filecatalog/catalog_test.go

@@ -0,0 +1,270 @@
+package filecatalog
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"reflect"
+	"strings"
+	"testing"
+	"testing/fstest"
+)
+
+func TestFindYAMLFilesNestedSortedAndFiltered(t *testing.T) {
+	root := t.TempDir()
+	mustWriteFile(t, filepath.Join(root, "z", "prompt.yml"), "id: z")
+	mustWriteFile(t, filepath.Join(root, "a", "profile.yaml"), "id: a")
+	mustWriteFile(t, filepath.Join(root, "a", "ignore.txt"), "not yaml")
+	mustWriteFile(t, filepath.Join(root, "b", "ignore.yaml.bak"), "not yaml")
+
+	got, err := FindYAMLFiles(context.Background(), root)
+	if err != nil {
+		t.Fatalf("expected no error, got %v", err)
+	}
+
+	want := []string{
+		filepath.Join(root, "a", "profile.yaml"),
+		filepath.Join(root, "z", "prompt.yml"),
+	}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("expected sorted YAML files %v, got %v", want, got)
+	}
+}
+
+func TestFindYAMLFilesHonorsContextCancellation(t *testing.T) {
+	root := t.TempDir()
+	mustWriteFile(t, filepath.Join(root, "one.yaml"), "id: one")
+
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	_, err := FindYAMLFiles(ctx, root)
+	if !errors.Is(err, context.Canceled) {
+		t.Fatalf("expected context.Canceled, got %v", err)
+	}
+}
+
+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")
+	got := RelativePath(root, path)
+	want := filepath.Join("nested", "profiles", "local.yaml")
+	if got != want {
+		t.Fatalf("expected relative path %q, got %q", want, got)
+	}
+}
+
+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
+		in   string
+		want string
+	}{
+		{name: "yaml", in: "prompt.yaml", want: "prompt"},
+		{name: "yml", in: "profile.yml", want: "profile"},
+		{name: "other", in: "file.txt", want: "file.txt"},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if got := Stem(tc.in); got != tc.want {
+				t.Fatalf("expected %q, got %q", tc.want, got)
+			}
+		})
+	}
+}
+
+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 {
+		t.Fatalf("failed to create directory: %v", err)
+	}
+	if err := os.WriteFile(path, []byte(content), 0o644); err != nil {
+		t.Fatalf("failed to write file %q: %v", path, err)
+	}
+}

internal/llm/client.go

@@ -0,0 +1,11 @@
+package llm
+
+import (
+	"context"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+// Client executes a rendered prompt against an LLM endpoint.
+type Client interface {
+	Generate(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error)
+}

internal/llm/openai_compatible_client.go

@@ -0,0 +1,385 @@
+package llm
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"net/url"
+	"os"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/defaults"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+var (
+	ErrInvalidConfig     = errors.New("invalid llm client configuration")
+	ErrInvalidRequest    = errors.New("invalid generate request")
+	ErrRequestFailed     = errors.New("llm request failed")
+	ErrUnexpectedStatus  = errors.New("llm returned non-success status")
+	ErrMalformedResponse = errors.New("malformed llm response")
+)
+
+type OpenAICompatibleConfig struct {
+	BaseURL    string
+	Model      string
+	Timeout    time.Duration
+	HTTPClient *http.Client
+}
+
+type OpenAICompatibleClient struct {
+	baseURL      string
+	defaultModel string
+	httpClient   *http.Client
+}
+
+func NewOpenAICompatibleClient(cfg OpenAICompatibleConfig) (*OpenAICompatibleClient, error) {
+	baseURL := strings.TrimSpace(cfg.BaseURL)
+	if baseURL != "" {
+		if _, err := url.ParseRequestURI(baseURL); err != nil {
+			return nil, fmt.Errorf("%w: invalid base URL: %v", ErrInvalidConfig, err)
+		}
+	}
+
+	timeout := cfg.Timeout
+	if timeout <= 0 {
+		timeout = defaults.LLMRequestTimeoutDefault
+	}
+
+	var client *http.Client
+	if cfg.HTTPClient != nil {
+		cloned := *cfg.HTTPClient
+		if cloned.Timeout <= 0 {
+			cloned.Timeout = timeout
+		}
+		client = &cloned
+	} else {
+		client = &http.Client{Timeout: timeout}
+	}
+
+	return &OpenAICompatibleClient{
+		baseURL:      strings.TrimRight(baseURL, "/"),
+		defaultModel: cfg.Model,
+		httpClient:   client,
+	}, nil
+}
+
+func (c *OpenAICompatibleClient) Generate(ctx context.Context, req domain.GenerateRequest) (*domain.GenerateResponse, error) {
+	if req.Target.TimeoutSeconds < 0 {
+		return nil, fmt.Errorf("%w: timeout_seconds must be greater than or equal to 0", ErrInvalidRequest)
+	}
+
+	endpoint := strings.TrimSpace(req.Target.Endpoint)
+	if endpoint == "" {
+		endpoint = c.baseURL
+	}
+	if endpoint == "" {
+		return nil, fmt.Errorf("%w: endpoint is required", ErrInvalidRequest)
+	}
+	endpoint = strings.TrimRight(endpoint, "/") + defaults.OpenAIChatCompletionsPath
+
+	wireReq, err := openAIChatRequestFromGenerateRequest(req, c.defaultModel)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrInvalidRequest, err)
+	}
+
+	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)
+	}
+
+	requestContext := ctx
+	if req.Target.TimeoutSeconds > 0 {
+		var cancel context.CancelFunc
+		requestContext, cancel = context.WithTimeout(
+			ctx,
+			time.Duration(req.Target.TimeoutSeconds)*time.Second,
+		)
+		defer cancel()
+	}
+
+	httpReq, err := http.NewRequestWithContext(requestContext, http.MethodPost, endpoint, bytes.NewReader(payload))
+	if err != nil {
+		return nil, fmt.Errorf("%w: failed to create request: %v", ErrRequestFailed, err)
+	}
+	httpReq.Header.Set("Content-Type", "application/json")
+	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)
+		}
+		httpReq.Header.Set("Authorization", "Bearer "+apiKey)
+	}
+
+	httpClient := c.httpClient
+	if httpClient == nil {
+		httpClient = &http.Client{Timeout: defaults.LLMRequestTimeoutDefault}
+	}
+
+	httpResp, err := httpClient.Do(httpReq)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %v", ErrRequestFailed, err)
+	}
+	defer httpResp.Body.Close()
+
+	if httpResp.StatusCode < 200 || httpResp.StatusCode >= 300 {
+		_, _ = io.Copy(io.Discard, io.LimitReader(httpResp.Body, 4096))
+		return nil, fmt.Errorf("%w: status=%d", ErrUnexpectedStatus, httpResp.StatusCode)
+	}
+
+	var wireResp openAIChatResponse
+	if err := json.NewDecoder(httpResp.Body).Decode(&wireResp); err != nil {
+		return nil, fmt.Errorf("%w: failed to decode response: %v", ErrMalformedResponse, err)
+	}
+
+	if len(wireResp.Choices) == 0 {
+		return nil, fmt.Errorf("%w: no choices returned", ErrMalformedResponse)
+	}
+	content := wireResp.Choices[0].Message.Content
+	if content == "" {
+		return nil, fmt.Errorf("%w: first choice has empty message content", ErrMalformedResponse)
+	}
+
+	return &domain.GenerateResponse{
+		Content: content,
+		Usage: domain.TokenUsage{
+			PromptTokens:     wireResp.Usage.PromptTokens,
+			CompletionTokens: wireResp.Usage.CompletionTokens,
+			TotalTokens:      wireResp.Usage.TotalTokens,
+			CachedTokens:     wireResp.Usage.PromptTokensDetails.CachedTokens,
+			CacheWriteTokens: wireResp.Usage.CacheWriteTokens,
+		},
+	}, nil
+}
+
+func openAIChatRequestFromGenerateRequest(req domain.GenerateRequest, defaultModel string) (openAIChatRequest, error) {
+	model := strings.TrimSpace(req.Target.Model)
+	if model == "" {
+		model = strings.TrimSpace(defaultModel)
+	}
+	if model == "" {
+		return openAIChatRequest{}, errors.New("model is required")
+	}
+
+	wireReq := openAIChatRequest{
+		Model: model,
+	}
+	if sessionID := strings.TrimSpace(req.Prompt.SessionID); sessionID != "" {
+		if n := utf8.RuneCountInString(sessionID); n > domain.SessionIDMaxLength {
+			return openAIChatRequest{}, fmt.Errorf("session_id length %d exceeds maximum %d", n, domain.SessionIDMaxLength)
+		}
+		wireReq.SessionID = sessionID
+	}
+
+	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 || req.TargetPresence.MaxTokens {
+		wireReq.MaxTokens = &req.Target.MaxTokens
+	}
+	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 {
+			return openAIChatRequest{}, err
+		}
+		wireReq.ResponseFormat = responseFormat
+	}
+
+	return wireReq, nil
+}
+
+type openAIChatRequest struct {
+	Model           string                     `json:"model"`
+	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:"-"`
+}
+
+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 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"`
+}
+
+type openAIResponseFormat struct {
+	Type       string                    `json:"type"`
+	JSONSchema *openAIJSONSchemaEnvelope `json:"json_schema,omitempty"`
+}
+
+type openAIJSONSchemaEnvelope struct {
+	Name   string `json:"name"`
+	Strict bool   `json:"strict"`
+	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
+	}
+
+	switch spec.Type {
+	case domain.StructuredOutputJSONSchema:
+		if spec.JSONSchema == nil {
+			return nil, errors.New("json_schema structured output requires schema payload")
+		}
+		if strings.TrimSpace(spec.JSONSchema.Name) == "" {
+			return nil, errors.New("json_schema structured output requires non-empty schema name")
+		}
+		if spec.JSONSchema.Schema == nil {
+			return nil, errors.New("json_schema structured output requires schema document")
+		}
+		return &openAIResponseFormat{
+			Type: "json_schema",
+			JSONSchema: &openAIJSONSchemaEnvelope{
+				Name:   spec.JSONSchema.Name,
+				Strict: spec.JSONSchema.Strict,
+				Schema: spec.JSONSchema.Schema,
+			},
+		}, nil
+	default:
+		return nil, fmt.Errorf("unsupported structured output type %q", spec.Type)
+	}
+}

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-flash.yml

@@ -0,0 +1,7 @@
+id: deepseek-4-flash
+endpoint: https://openrouter.ai/api/v1
+model: deepseek/deepseek-v4-flash
+#reasoning_effort: medium
+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/promptkit/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/promptkit/internal/domain"
+	"gitea.maximumdirect.net/eric/promptkit/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

@@ -0,0 +1,213 @@
+package profile
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+	"gitea.maximumdirect.net/eric/promptkit/internal/filecatalog"
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	ErrProfileNotFound     = errors.New("execution profile not found")
+	ErrInvalidYAML         = errors.New("invalid YAML format")
+	ErrInvalidProfile      = errors.New("invalid execution profile configuration")
+	ErrRawAPIKeyNotAllowed = errors.New("raw api_key is not allowed; use api_key_env")
+)
+
+type filesystemRepository struct {
+	dir string
+}
+
+func NewFilesystemRepository(dir string) Repository {
+	return &filesystemRepository{dir: dir}
+}
+
+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.FindFSYAMLFiles(ctx, fsys, root)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read profile directory: %w", err)
+	}
+
+	var matches []profileMatch
+	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 {
+			return nil, fmt.Errorf("failed to read profile file %s: %w", relPath, err)
+		}
+		metadata := readProfileFileMetadata(data)
+		idMatch := fileMatch || metadata.id == id
+		if metadata.hasRawAPIKey {
+			if idMatch {
+				return nil, fmt.Errorf("%w: %s", ErrRawAPIKeyNotAllowed, relPath)
+			}
+			continue
+		}
+
+		var prof domain.ExecutionProfile
+		decoder := yaml.NewDecoder(bytes.NewReader(data))
+		decoder.KnownFields(true)
+		if err := decoder.Decode(&prof); err != nil {
+			if idMatch {
+				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidYAML, relPath, err)
+			}
+			continue
+		}
+
+		if prof.ID != id {
+			continue
+		}
+		if err := validateProfile(&prof); err != nil {
+			if errors.Is(err, ErrRawAPIKeyNotAllowed) {
+				return nil, fmt.Errorf("%w: %s", err, relPath)
+			}
+			return nil, fmt.Errorf("%w: %s: %v", ErrInvalidProfile, relPath, err)
+		}
+		matches = append(matches, profileMatch{
+			profile: &prof,
+			path:    relPath,
+		})
+	}
+
+	if len(matches) > 1 {
+		paths := make([]string, 0, len(matches))
+		for _, match := range matches {
+			paths = append(paths, match.path)
+		}
+		return nil, fmt.Errorf("%w: duplicate execution profile id %q found in: %s", ErrInvalidProfile, id, strings.Join(paths, ", "))
+	}
+
+	if len(matches) == 1 {
+		return matches[0].profile, nil
+	}
+
+	return nil, ErrProfileNotFound
+}
+
+type profileMatch struct {
+	profile *domain.ExecutionProfile
+	path    string
+}
+
+type profileFileMetadata struct {
+	id           string
+	hasRawAPIKey bool
+}
+
+func readProfileFileMetadata(data []byte) profileFileMetadata {
+	var node yaml.Node
+	if err := yaml.NewDecoder(bytes.NewReader(data)).Decode(&node); err != nil {
+		return profileFileMetadata{}
+	}
+	if node.Kind != yaml.DocumentNode || len(node.Content) == 0 {
+		return profileFileMetadata{}
+	}
+	mapping := node.Content[0]
+	if mapping.Kind != yaml.MappingNode {
+		return profileFileMetadata{}
+	}
+
+	var metadata profileFileMetadata
+	for i := 0; i+1 < len(mapping.Content); i += 2 {
+		key := mapping.Content[i]
+		value := mapping.Content[i+1]
+		switch key.Value {
+		case "id":
+			metadata.id = strings.TrimSpace(value.Value)
+		case "api_key":
+			metadata.hasRawAPIKey = true
+		}
+	}
+	return metadata
+}
+
+func validateProfile(p *domain.ExecutionProfile) error {
+	if strings.TrimSpace(p.ID) == "" {
+		return errors.New("id is required")
+	}
+	if strings.TrimSpace(p.Endpoint) == "" {
+		return errors.New("endpoint is required")
+	}
+	if strings.TrimSpace(p.Model) == "" {
+		return errors.New("model is required")
+	}
+
+	if p.Temperature < 0 || p.Temperature > 2 {
+		return errors.New("temperature must be between 0 and 2")
+	}
+	if p.MaxTokens < 0 {
+		return errors.New("max_tokens must be greater than or equal to 0")
+	}
+	if p.TopP < 0 || p.TopP > 1 {
+		return errors.New("top_p must be between 0 and 1")
+	}
+	if p.TimeoutSeconds < 0 {
+		return errors.New("timeout_seconds must be greater than or equal to 0")
+	}
+
+	return nil
+}

internal/profile/repository.go

@@ -0,0 +1,12 @@
+package profile
+
+import (
+	"context"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+// Repository loads execution profiles.
+type Repository interface {
+	GetProfile(ctx context.Context, id string) (*domain.ExecutionProfile, error)
+}

internal/profile/repository_test.go

@@ -0,0 +1,479 @@
+package profile
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestFilesystemRepository_GetProfile(t *testing.T) {
+	tmpDir, err := os.MkdirTemp("", "execution_profile_test")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	files, err := os.ReadDir("testdata")
+	if err != nil {
+		t.Fatalf("failed to read testdata: %v", err)
+	}
+	for _, f := range files {
+		src := filepath.Join("testdata", f.Name())
+		dst := filepath.Join(tmpDir, f.Name())
+		data, err := os.ReadFile(src)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(dst, data, 0644); err != nil {
+			t.Fatal(err)
+		}
+	}
+
+	repo := NewFilesystemRepository(tmpDir)
+	ctx := context.Background()
+
+	t.Run("valid local profile", func(t *testing.T) {
+		p, err := repo.GetProfile(ctx, "local-default")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.ID != "local-default" {
+			t.Fatalf("unexpected id: %q", p.ID)
+		}
+		if p.Endpoint == "" || p.Model == "" {
+			t.Fatalf("expected endpoint/model to be set: %+v", p)
+		}
+	})
+
+	t.Run("valid profile with api_key_env", func(t *testing.T) {
+		p, err := repo.GetProfile(ctx, "local-secure")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.APIKeyEnv != "PROMPTKIT_API_KEY" {
+			t.Fatalf("unexpected api_key_env: %q", p.APIKeyEnv)
+		}
+		if p.ReasoningEffort != "medium" {
+			t.Fatalf("unexpected reasoning_effort: %q", p.ReasoningEffort)
+		}
+		if p.ServiceTier != "priority" {
+			t.Fatalf("unexpected service_tier: %q", p.ServiceTier)
+		}
+	})
+
+	t.Run("valid nested profile", func(t *testing.T) {
+		nestedDir := filepath.Join(tmpDir, "local")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writeProfileTestFile(t, filepath.Join(nestedDir, "nested-local.yaml"), `
+id: nested-local
+endpoint: http://localhost:8000/v1
+model: nested-model
+temperature: 0.1
+`)
+
+		p, err := repo.GetProfile(ctx, "nested-local")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.Model != "nested-model" {
+			t.Fatalf("unexpected model: %q", p.Model)
+		}
+	})
+
+	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
+endpoint: http://localhost:8000/v1
+model: first-model
+`)
+		nestedDir := filepath.Join(tmpDir, "duplicates")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writeProfileTestFile(t, filepath.Join(nestedDir, "duplicate-profile-b.yaml"), `
+id: duplicate-profile
+endpoint: http://localhost:8000/v1
+model: second-model
+`)
+
+		_, err := repo.GetProfile(ctx, "duplicate-profile")
+		if !errors.Is(err, ErrInvalidProfile) {
+			t.Fatalf("expected duplicate profile to return ErrInvalidProfile, got %v", err)
+		}
+		for _, want := range []string{"duplicate execution profile id", "duplicate-profile-a.yaml", filepath.Join("duplicates", "duplicate-profile-b.yaml")} {
+			if !strings.Contains(err.Error(), want) {
+				t.Fatalf("expected error to contain %q, got %v", want, err)
+			}
+		}
+	})
+
+	t.Run("nested raw api_key rejected for likely target file", func(t *testing.T) {
+		nestedDir := filepath.Join(tmpDir, "secure")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writeProfileTestFile(t, filepath.Join(nestedDir, "not_named_like_id.yaml"), `
+id: nested_raw_api_key
+endpoint: http://localhost:8000/v1
+model: m
+api_key: secret
+`)
+
+		_, err := repo.GetProfile(ctx, "nested_raw_api_key")
+		if !errors.Is(err, ErrRawAPIKeyNotAllowed) {
+			t.Fatalf("expected ErrRawAPIKeyNotAllowed, got %v", err)
+		}
+		if !strings.Contains(err.Error(), filepath.Join("secure", "not_named_like_id.yaml")) {
+			t.Fatalf("expected nested path in error, got %v", err)
+		}
+	})
+
+	t.Run("raw api_key in non-target profile is ignored", func(t *testing.T) {
+		writeProfileTestFile(t, filepath.Join(tmpDir, "raw-api-key-non-target.yaml"), `
+id: raw-api-key-non-target
+endpoint: http://localhost:8000/v1
+model: m
+api_key: secret
+`)
+
+		_, err := repo.GetProfile(ctx, "does-not-exist-with-raw-key-nearby")
+		if !errors.Is(err, ErrProfileNotFound) {
+			t.Fatalf("expected ErrProfileNotFound for non-target raw api_key file, got %v", err)
+		}
+	})
+
+	t.Run("invalid yaml", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "invalid_yaml")
+		if !errors.Is(err, ErrInvalidYAML) {
+			t.Fatalf("expected ErrInvalidYAML, got %v", err)
+		}
+	})
+
+	t.Run("missing id", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "missing_id")
+		if !errors.Is(err, ErrProfileNotFound) {
+			t.Fatalf("expected ErrProfileNotFound, got %v", err)
+		}
+	})
+
+	t.Run("missing endpoint", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "missing-endpoint")
+		if !errors.Is(err, ErrInvalidProfile) {
+			t.Fatalf("expected ErrInvalidProfile, got %v", err)
+		}
+	})
+
+	t.Run("missing model", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "missing-model")
+		if !errors.Is(err, ErrInvalidProfile) {
+			t.Fatalf("expected ErrInvalidProfile, got %v", err)
+		}
+	})
+
+	t.Run("unknown field", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "unknown_field")
+		if !errors.Is(err, ErrInvalidYAML) {
+			t.Fatalf("expected ErrInvalidYAML for strict decode unknown field, got %v", err)
+		}
+	})
+
+	t.Run("raw api_key rejected", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "raw_api_key")
+		if !errors.Is(err, ErrRawAPIKeyNotAllowed) {
+			t.Fatalf("expected ErrRawAPIKeyNotAllowed, got %v", err)
+		}
+	})
+
+	t.Run("profile not found", func(t *testing.T) {
+		_, err := repo.GetProfile(ctx, "does-not-exist")
+		if !errors.Is(err, ErrProfileNotFound) {
+			t.Fatalf("expected ErrProfileNotFound, got %v", err)
+		}
+	})
+}
+
+func writeProfileTestFile(t *testing.T, path string, content string) {
+	t.Helper()
+	if err := os.WriteFile(path, []byte(strings.TrimLeft(content, "\n")), 0o644); err != nil {
+		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/profile/testdata/invalid_yaml.yaml

@@ -0,0 +1,3 @@
+id: invalid_yaml
+endpoint: http://localhost:8000/v1
+model: [broken

internal/profile/testdata/missing_endpoint.yaml

@@ -0,0 +1,2 @@
+id: missing-endpoint
+model: gpt-4o-mini

internal/profile/testdata/missing_id.yaml

@@ -0,0 +1,2 @@
+endpoint: http://localhost:8000/v1
+model: gpt-4o-mini

internal/profile/testdata/missing_model.yaml

@@ -0,0 +1,2 @@
+id: missing-model
+endpoint: http://localhost:8000/v1

internal/profile/testdata/raw_api_key.yaml

@@ -0,0 +1,4 @@
+id: raw-api-key
+endpoint: http://localhost:8000/v1
+model: gpt-4o-mini
+api_key: super-secret-should-not-be-here

internal/profile/testdata/unknown_field.yaml

@@ -0,0 +1,4 @@
+id: unknown-field
+endpoint: http://localhost:8000/v1
+model: gpt-4o-mini
+foo: bar

internal/profile/testdata/valid_local_profile.yaml

@@ -0,0 +1,7 @@
+id: local-default
+endpoint: http://localhost:8000/v1
+model: gpt-4o-mini
+temperature: 0.2
+max_tokens: 700
+top_p: 1.0
+timeout_seconds: 120

internal/profile/testdata/valid_with_api_key_env.yaml

@@ -0,0 +1,8 @@
+id: local-secure
+endpoint: http://localhost:8000/v1
+model: gpt-4o-mini
+api_key_env: PROMPTKIT_API_KEY
+service_tier: priority
+reasoning_effort: medium
+extra_params:
+  provider: local

internal/prompt/go_renderer.go

@@ -0,0 +1,125 @@
+package prompt
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+	"strings"
+	"text/template"
+	"unicode/utf8"
+)
+
+var (
+	ErrMissingRequiredInput = errors.New("missing required input artifact")
+	ErrUnknownInput         = errors.New("referenced unknown input artifact")
+	ErrInvalidTemplate      = errors.New("invalid prompt template")
+	ErrRenderFailure        = errors.New("prompt render failure")
+	ErrInvalidMessageRole   = errors.New("invalid or empty message role")
+)
+
+type goRenderer struct{}
+
+func NewGoRenderer() Renderer {
+	return &goRenderer{}
+}
+
+func (r *goRenderer) Render(ctx context.Context, definition *domain.PromptDefinition, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error) {
+	if definition == nil {
+		return nil, fmt.Errorf("%w: nil prompt definition", ErrRenderFailure)
+	}
+
+	// 1. Verify required inputs
+	for _, in := range definition.Inputs {
+		if !in.Required {
+			continue
+		}
+		art, ok := inputs[in.Name]
+		if !ok || art == nil {
+			return nil, fmt.Errorf("%w: %s", ErrMissingRequiredInput, in.Name)
+		}
+	}
+
+	// 2. Setup template functions
+	funcs := template.FuncMap{
+		"input": func(name string) (string, error) {
+			art, ok := inputs[name]
+			if !ok || art == nil {
+				return "", fmt.Errorf("%w: %s", ErrUnknownInput, name)
+			}
+			return string(art.Body), nil
+		},
+	}
+
+	sessionID, err := renderSessionID(definition.SessionID, funcs, vars)
+	if err != nil {
+		return nil, err
+	}
+
+	var renderedMessages []domain.RenderedMessage
+
+	for i, tmplMsg := range definition.Templates {
+		select {
+		case <-ctx.Done():
+			return nil, ctx.Err()
+		default:
+		}
+
+		if tmplMsg.Role == "" {
+			return nil, fmt.Errorf("%w: message %d", ErrInvalidMessageRole, i)
+		}
+
+		// Parse and execute template
+		tmpl, err := template.New(fmt.Sprintf("msg_%d", i)).Funcs(funcs).Option("missingkey=error").Parse(tmplMsg.Content)
+		if err != nil {
+			return nil, fmt.Errorf("%w: message %d: %v", ErrInvalidTemplate, i, err)
+		}
+
+		var buf bytes.Buffer
+		if err := tmpl.Execute(&buf, vars); err != nil {
+			return nil, fmt.Errorf("%w: message %d: %w", ErrRenderFailure, i, err)
+		}
+
+		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.go

@@ -0,0 +1,11 @@
+package prompt
+
+import (
+	"context"
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+// Renderer renders prompt templates using named artifacts and variables.
+type Renderer interface {
+	Render(ctx context.Context, definition *domain.PromptDefinition, inputs map[string]*domain.Artifact, vars map[string]string) (*domain.RenderedPrompt, error)
+}

internal/prompt/renderer_test.go

@@ -0,0 +1,345 @@
+package prompt
+
+import (
+	"context"
+	"errors"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestGoRenderer_Render(t *testing.T) {
+	renderer := NewGoRenderer()
+	ctx := context.Background()
+
+	inputs := map[string]*domain.Artifact{
+		"transcript": {Body: []byte("The quick brown fox.")},
+	}
+	vars := map[string]string{
+		"role": "helpful assistant",
+		"tone": "concise",
+	}
+
+	t.Run("rendering inline message content", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{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) != 1 {
+			t.Fatalf("expected 1 message, got %d", len(res.Messages))
+		}
+		if res.Messages[0].Content != "Analyze this: The quick brown fox." {
+			t.Fatalf("unexpected rendered content: %q", res.Messages[0].Content)
+		}
+	})
+
+	t.Run("rendering file-backed message content loaded into prompt definition", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "From file: {{input \"transcript\"}}", ContentFile: "/tmp/user.tmpl"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if got := res.Messages[0].Content; got != "From file: The quick brown fox." {
+			t.Fatalf("unexpected file-backed render result: %q", got)
+		}
+	})
+
+	t.Run("rendering system and user messages", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "system", Content: "You are a {{.role}}."},
+				{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].Role != "system" || res.Messages[1].Role != "user" {
+			t.Fatalf("unexpected roles: %#v", res.Messages)
+		}
+	})
+
+	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}},
+			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.Messages[0].Content != "Speak in a concise tone." {
+			t.Fatalf("unexpected vars rendering: %q", res.Messages[0].Content)
+		}
+	})
+
+	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}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "{{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if res.Messages[0].Content != "The quick brown fox." {
+			t.Fatalf("unexpected required input rendering: %q", res.Messages[0].Content)
+		}
+	})
+
+	t.Run("optional input absent and not referenced", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{
+				{Name: "transcript", Required: true},
+				{Name: "glossary", Required: false},
+			},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Transcript: {{input \"transcript\"}}"},
+			},
+		}
+
+		res, err := renderer.Render(ctx, def, inputs, vars)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if len(res.Messages) != 1 {
+			t.Fatalf("expected one rendered message, got %d", len(res.Messages))
+		}
+	})
+
+	t.Run("optional input absent but referenced, expecting failure", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{
+				{Name: "transcript", Required: true},
+				{Name: "glossary", Required: false},
+			},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Glossary: {{input \"glossary\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+		if !errors.Is(err, ErrUnknownInput) {
+			t.Fatalf("expected ErrUnknownInput, got %v", err)
+		}
+	})
+
+	t.Run("required input missing, expecting failure", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Analyze this: {{input \"transcript\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, map[string]*domain.Artifact{}, vars)
+		if !errors.Is(err, ErrMissingRequiredInput) {
+			t.Fatalf("expected ErrMissingRequiredInput, got %v", err)
+		}
+	})
+
+	t.Run("invalid template syntax", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Hello {{.unclosed"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrInvalidTemplate) {
+			t.Fatalf("expected ErrInvalidTemplate, got %v", err)
+		}
+	})
+
+	t.Run("unknown input reference", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "user", Content: "Hello {{input \"ghost\"}}"},
+			},
+		}
+
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrRenderFailure) {
+			t.Fatalf("expected ErrRenderFailure, got %v", err)
+		}
+		if !errors.Is(err, ErrUnknownInput) {
+			t.Fatalf("expected ErrUnknownInput, got %v", err)
+		}
+	})
+
+	t.Run("empty message role", func(t *testing.T) {
+		def := &domain.PromptDefinition{
+			Inputs: []domain.PromptInput{{Name: "transcript", Required: true}},
+			Templates: []domain.PromptMessageTemplate{
+				{Role: "", Content: "Hello"},
+			},
+		}
+		_, err := renderer.Render(ctx, def, inputs, vars)
+		if !errors.Is(err, ErrInvalidMessageRole) {
+			t.Fatalf("expected ErrInvalidMessageRole, got %v", err)
+		}
+	})
+}

internal/promptdef/filesystem_repository.go

@@ -0,0 +1,484 @@
+package promptdef
+
+import (
+	"bytes"
+	"context"
+	"errors"
+	"fmt"
+	"io/fs"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+	"gitea.maximumdirect.net/eric/promptkit/internal/filecatalog"
+	"gopkg.in/yaml.v3"
+)
+
+var (
+	ErrPromptDefinitionNotFound = errors.New("prompt definition not found")
+	ErrInvalidYAML              = errors.New("invalid YAML format")
+	ErrInvalidPromptDefinition  = errors.New("invalid prompt definition configuration")
+)
+
+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"`
+}
+
+type promptInputFile struct {
+	Name        string `yaml:"name"`
+	Required    bool   `yaml:"required"`
+	ContentType string `yaml:"content_type"`
+	Description string `yaml:"description"`
+}
+
+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 {
+	Format         domain.OutputFormat   `yaml:"format"`
+	ValidationMode domain.ValidationMode `yaml:"validation_mode"`
+	SchemaPath     string                `yaml:"schema_path"`
+	RepairAttempts int                   `yaml:"repair_attempts"`
+}
+
+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)
+	}
+
+	files, err := filecatalog.FindYAMLFiles(ctx, r.dir)
+	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.RelativePath(r.dir, fullPath)
+		fileMatch := filecatalog.Stem(filepath.Base(fullPath)) == id
+
+		raw, err := loadPromptDefinitionFile(fullPath)
+		if err != nil {
+			if fileMatch || promptDefinitionFileHasID(fullPath, id) {
+				return nil, fmt.Errorf("%w: %s: %v", ErrInvalidYAML, relPath, err)
+			}
+			continue
+		}
+
+		def, err := normalizePromptDefinition(raw, fullPath)
+		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 (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
+}
+
+func loadPromptDefinitionFile(path string) (*promptDefinitionFile, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read prompt definition file: %w", err)
+	}
+
+	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 promptDefinitionFileHasID(path string, id string) bool {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return false
+	}
+	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 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")
+	}
+
+	id := strings.TrimSpace(raw.ID)
+	if id == "" {
+		return nil, errors.New("id is required")
+	}
+
+	version := strings.TrimSpace(raw.Version)
+	if version == "" {
+		return nil, errors.New("version is required")
+	}
+
+	if len(raw.Messages) == 0 {
+		return nil, errors.New("at least one message is required")
+	}
+
+	inputs := make([]domain.PromptInput, 0, len(raw.Inputs))
+	seenInputNames := make(map[string]struct{}, len(raw.Inputs))
+	for i, in := range raw.Inputs {
+		name := strings.TrimSpace(in.Name)
+		if name == "" {
+			return nil, fmt.Errorf("input %d has empty name", i)
+		}
+		if _, exists := seenInputNames[name]; exists {
+			return nil, fmt.Errorf("duplicate input name %q", name)
+		}
+		seenInputNames[name] = struct{}{}
+
+		inputs = append(inputs, domain.PromptInput{
+			Name:        name,
+			Required:    in.Required,
+			ContentType: strings.TrimSpace(in.ContentType),
+			Description: strings.TrimSpace(in.Description),
+		})
+	}
+
+	templates := make([]domain.PromptMessageTemplate, 0, len(raw.Messages))
+	for i, msg := range raw.Messages {
+		role := strings.TrimSpace(msg.Role)
+		if role == "" {
+			return nil, fmt.Errorf("message %d role is required", i)
+		}
+
+		hasContent := strings.TrimSpace(msg.Content) != ""
+		hasContentFile := strings.TrimSpace(msg.ContentFile) != ""
+		if hasContent == hasContentFile {
+			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 {
+			body, resolvedPath, err := readContentFile(msg.ContentFile)
+			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 = body
+			resolvedContentFile = resolvedPath
+		}
+
+		templates = append(templates, domain.PromptMessageTemplate{
+			Role:         role,
+			Content:      templateContent,
+			ContentFile:  resolvedContentFile,
+			CacheControl: cacheControl,
+		})
+	}
+
+	if !isValidOutputFormat(raw.Output.Format) {
+		return nil, fmt.Errorf("invalid output format: %q", raw.Output.Format)
+	}
+	if !isValidValidationMode(raw.Output.ValidationMode) {
+		return nil, fmt.Errorf("invalid validation mode: %q", raw.Output.ValidationMode)
+	}
+	if raw.Output.ValidationMode == domain.ValidationJSONSchema && strings.TrimSpace(raw.Output.SchemaPath) == "" {
+		return nil, errors.New("output.schema_path is required when output.validation_mode is json_schema")
+	}
+	if raw.Output.RepairAttempts < 0 {
+		return nil, errors.New("output.repair_attempts must be greater than or equal to 0")
+	}
+
+	defaultProfile := ""
+	if raw.DefaultProfile != nil {
+		defaultProfile = strings.TrimSpace(*raw.DefaultProfile)
+		if defaultProfile == "" {
+			return nil, errors.New("default_profile must be a non-empty string when set")
+		}
+	}
+
+	return &domain.PromptDefinition{
+		ID:             id,
+		Version:        version,
+		DefaultProfile: defaultProfile,
+		Description:    strings.TrimSpace(raw.Description),
+		SessionID:      strings.TrimSpace(raw.SessionID),
+		Inputs:         inputs,
+		Templates:      templates,
+		OutputFormat:   raw.Output.Format,
+		Validation: domain.OutputContract{
+			Format:         raw.Output.Format,
+			ValidationMode: raw.Output.ValidationMode,
+			SchemaPath:     strings.TrimSpace(raw.Output.SchemaPath),
+			RepairAttempts: raw.Output.RepairAttempts,
+		},
+	}, 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:
+		return true
+	default:
+		return false
+	}
+}
+
+func isValidValidationMode(m domain.ValidationMode) bool {
+	switch m {
+	case domain.ValidationNone, domain.ValidationBasic, domain.ValidationJSON, domain.ValidationJSONSchema:
+		return true
+	default:
+		return false
+	}
+}

internal/promptdef/repository.go

@@ -0,0 +1,12 @@
+package promptdef
+
+import (
+	"context"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+// Repository loads prompt definitions.
+type Repository interface {
+	GetPromptDefinition(ctx context.Context, id string, version string) (*domain.PromptDefinition, error)
+}

internal/promptdef/repository_test.go

@@ -0,0 +1,526 @@
+package promptdef
+
+import (
+	"context"
+	"errors"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"testing/fstest"
+
+	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
+)
+
+func TestFilesystemRepository_GetPromptDefinition(t *testing.T) {
+	tmpDir := t.TempDir()
+	if err := copyTree("testdata", tmpDir); err != nil {
+		t.Fatalf("failed to copy testdata: %v", err)
+	}
+
+	repo := NewFilesystemRepository(tmpDir)
+	ctx := context.Background()
+
+	t.Run("valid inline prompt", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "valid-inline", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.ID != "valid-inline" {
+			t.Fatalf("unexpected id: %q", p.ID)
+		}
+		if p.Version != "1.0.0" {
+			t.Fatalf("unexpected version: %q", p.Version)
+		}
+		if p.OutputFormat != domain.FormatMarkdown {
+			t.Fatalf("unexpected output format: %q", p.OutputFormat)
+		}
+		if p.Validation.ValidationMode != domain.ValidationBasic {
+			t.Fatalf("unexpected validation mode: %q", p.Validation.ValidationMode)
+		}
+		if len(p.Templates) != 2 {
+			t.Fatalf("expected 2 messages, got %d", len(p.Templates))
+		}
+		if len(p.Inputs) != 1 {
+			t.Fatalf("expected 1 input, got %d", len(p.Inputs))
+		}
+		if p.Inputs[0].ContentType != "text/markdown" {
+			t.Fatalf("expected input content_type to be preserved, got %q", p.Inputs[0].ContentType)
+		}
+	})
+
+	t.Run("valid file-backed prompt", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "valid-file-backed", "")
+		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))
+		}
+		if !strings.Contains(p.Templates[1].Content, "{{input \"transcript\"}}") {
+			t.Fatalf("expected content_file template body to be loaded, got %q", p.Templates[1].Content)
+		}
+		if p.Templates[1].ContentFile == "" {
+			t.Fatal("expected ContentFile source metadata to be preserved")
+		}
+		if !filepath.IsAbs(p.Templates[1].ContentFile) {
+			t.Fatalf("expected resolved content_file path to be absolute, got %q", p.Templates[1].ContentFile)
+		}
+	})
+
+	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 {
+			t.Fatal(err)
+		}
+		writePromptTestFile(t, filepath.Join(nestedDir, "nested_recap.yaml"), `
+id: nested-recap
+version: "1.0.0"
+messages:
+  - role: user
+    content_file: ./nested_recap.user.tmpl
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+		writePromptTestFile(t, filepath.Join(nestedDir, "nested_recap.user.tmpl"), `Nested recap: {{input "transcript"}}`)
+
+		p, err := repo.GetPromptDefinition(ctx, "nested-recap", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if len(p.Templates) != 1 {
+			t.Fatalf("expected one template, got %d", len(p.Templates))
+		}
+		if !strings.Contains(p.Templates[0].Content, "Nested recap") {
+			t.Fatalf("expected nested content file body, got %q", p.Templates[0].Content)
+		}
+		if !strings.Contains(p.Templates[0].ContentFile, filepath.Join("dnd", "recap", "nested_recap.user.tmpl")) {
+			t.Fatalf("expected nested content file path, got %q", p.Templates[0].ContentFile)
+		}
+	})
+
+	t.Run("prompt with default_profile", func(t *testing.T) {
+		p, err := repo.GetPromptDefinition(ctx, "with-default-profile", "")
+		if err != nil {
+			t.Fatalf("expected no error, got %v", err)
+		}
+		if p.DefaultProfile != "local-default" {
+			t.Fatalf("unexpected default profile: %q", p.DefaultProfile)
+		}
+		if len(p.Inputs) != 1 {
+			t.Fatalf("expected one input, got %d", len(p.Inputs))
+		}
+		if p.Inputs[0].ContentType != "" {
+			t.Fatalf("expected missing content_type to remain empty, got %q", p.Inputs[0].ContentType)
+		}
+	})
+
+	t.Run("duplicate prompt IDs fail as ambiguous", func(t *testing.T) {
+		writePromptTestFile(t, filepath.Join(tmpDir, "duplicate_a.yaml"), `
+id: duplicate-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content: First duplicate.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+		nestedDir := filepath.Join(tmpDir, "nested")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writePromptTestFile(t, filepath.Join(nestedDir, "duplicate_b.yaml"), `
+id: duplicate-prompt
+version: "2.0.0"
+messages:
+  - role: user
+    content: Second duplicate.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+
+		_, err := repo.GetPromptDefinition(ctx, "duplicate-prompt", "")
+		if !errors.Is(err, ErrInvalidPromptDefinition) {
+			t.Fatalf("expected duplicate prompt to return ErrInvalidPromptDefinition, got %v", err)
+		}
+		for _, want := range []string{"duplicate prompt definition id", "duplicate_a.yaml", filepath.Join("nested", "duplicate_b.yaml")} {
+			if !strings.Contains(err.Error(), want) {
+				t.Fatalf("expected error to contain %q, got %v", want, err)
+			}
+		}
+	})
+
+	t.Run("duplicate prompt ID and requested version fails as ambiguous", func(t *testing.T) {
+		writePromptTestFile(t, filepath.Join(tmpDir, "version_duplicate_a.yaml"), `
+id: duplicate-version-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content: First duplicate version.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+		nestedDir := filepath.Join(tmpDir, "versioned")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writePromptTestFile(t, filepath.Join(nestedDir, "version_duplicate_b.yaml"), `
+id: duplicate-version-prompt
+version: "1.0.0"
+messages:
+  - role: user
+    content: Second duplicate version.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+
+		_, err := repo.GetPromptDefinition(ctx, "duplicate-version-prompt", "1.0.0")
+		if !errors.Is(err, ErrInvalidPromptDefinition) {
+			t.Fatalf("expected duplicate prompt version to return ErrInvalidPromptDefinition, got %v", err)
+		}
+		for _, want := range []string{"duplicate prompt definition id", "version \"1.0.0\"", "version_duplicate_a.yaml", filepath.Join("versioned", "version_duplicate_b.yaml")} {
+			if !strings.Contains(err.Error(), want) {
+				t.Fatalf("expected error to contain %q, got %v", want, err)
+			}
+		}
+	})
+
+	t.Run("non-matching malformed nested prompt is ignored for not found lookup", func(t *testing.T) {
+		nestedDir := filepath.Join(tmpDir, "broken")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writePromptTestFile(t, filepath.Join(nestedDir, "unrelated.yaml"), "id: [")
+
+		_, err := repo.GetPromptDefinition(ctx, "does-not-exist-even-with-broken-nested-file", "")
+		if !errors.Is(err, ErrPromptDefinitionNotFound) {
+			t.Fatalf("expected ErrPromptDefinitionNotFound, got %v", err)
+		}
+	})
+
+	t.Run("strict decode failure in nested prompt matches by YAML ID", func(t *testing.T) {
+		nestedDir := filepath.Join(tmpDir, "strict")
+		if err := os.MkdirAll(nestedDir, 0o755); err != nil {
+			t.Fatal(err)
+		}
+		writePromptTestFile(t, filepath.Join(nestedDir, "not_named_like_id.yaml"), `
+id: nested-strict-error
+version: "1.0.0"
+unknown_field: true
+messages:
+  - role: user
+    content: Invalid because of unknown field.
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0
+`)
+
+		_, err := repo.GetPromptDefinition(ctx, "nested-strict-error", "")
+		if !errors.Is(err, ErrInvalidYAML) {
+			t.Fatalf("expected ErrInvalidYAML, got %v", err)
+		}
+		if !strings.Contains(err.Error(), filepath.Join("strict", "not_named_like_id.yaml")) {
+			t.Fatalf("expected nested path in error, got %v", err)
+		}
+	})
+
+	t.Run("version lookup", func(t *testing.T) {
+		_, err := repo.GetPromptDefinition(ctx, "valid-inline", "9.9.9")
+		if !errors.Is(err, ErrPromptDefinitionNotFound) {
+			t.Fatalf("expected ErrPromptDefinitionNotFound, got %v", err)
+		}
+	})
+
+	cases := []struct {
+		name       string
+		id         string
+		targetErr  error
+		errSubstrs []string
+	}{
+		{name: "invalid YAML", id: "invalid_yaml", targetErr: ErrInvalidYAML},
+		{name: "missing id", id: "missing_id", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"id is required"}},
+		{name: "no messages", id: "no_messages", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"at least one message is required"}},
+		{name: "both content and content_file", id: "both_content_and_content_file", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"exactly one"}},
+		{name: "neither content nor content_file", id: "neither_content_nor_content_file", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"exactly one"}},
+		{name: "missing content_file", id: "missing_content_file", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"failed to read content_file"}},
+		{name: "duplicate input names", id: "duplicate_input_names", targetErr: ErrInvalidPromptDefinition, errSubstrs: []string{"duplicate input name"}},
+		{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 {
+		t.Run(tc.name, func(t *testing.T) {
+			_, err := repo.GetPromptDefinition(ctx, tc.id, "")
+			if !errors.Is(err, tc.targetErr) {
+				t.Fatalf("expected %v, got %v", tc.targetErr, err)
+			}
+			for _, sub := range tc.errSubstrs {
+				if !strings.Contains(err.Error(), sub) {
+					t.Fatalf("expected error to contain %q, got %v", sub, err)
+				}
+			}
+		})
+	}
+
+	t.Run("prompt definition not found", func(t *testing.T) {
+		_, err := repo.GetPromptDefinition(ctx, "does-not-exist", "")
+		if !errors.Is(err, ErrPromptDefinitionNotFound) {
+			t.Fatalf("expected ErrPromptDefinitionNotFound, got %v", err)
+		}
+	})
+}
+
+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 {
+		t.Fatalf("failed to write prompt test file %q: %v", path, err)
+	}
+}
+
+func copyTree(src, dst string) error {
+	return filepath.WalkDir(src, func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		rel, err := filepath.Rel(src, path)
+		if err != nil {
+			return err
+		}
+		if rel == "." {
+			return nil
+		}
+
+		target := filepath.Join(dst, rel)
+		if d.IsDir() {
+			return os.MkdirAll(target, 0o755)
+		}
+
+		data, err := os.ReadFile(path)
+		if err != nil {
+			return err
+		}
+		return os.WriteFile(target, data, 0o644)
+	})
+}

internal/promptdef/testdata/both_content_and_content_file.yaml

@@ -0,0 +1,10 @@
+id: both-content-and-content-file
+version: "1.0.0"
+messages:
+  - role: user
+    content: "Hi"
+    content_file: ./messages/user_prompt.tmpl
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

internal/promptdef/testdata/duplicate_input_names.yaml

@@ -0,0 +1,14 @@
+id: duplicate-input-names
+version: "1.0.0"
+inputs:
+  - name: transcript
+    required: true
+  - name: transcript
+    required: false
+messages:
+  - role: user
+    content: "Hi"
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

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/invalid_validation_mode.yaml

@@ -0,0 +1,9 @@
+id: invalid-validation-mode
+version: "1.0.0"
+messages:
+  - role: user
+    content: "Hi"
+output:
+  format: text
+  validation_mode: nope
+  repair_attempts: 0

internal/promptdef/testdata/invalid_yaml.yaml

@@ -0,0 +1,9 @@
+id: invalid-yaml
+version: "1.0.0"
+messages:
+  - role: user
+    content: [broken
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

internal/promptdef/testdata/json_schema_without_schema_path.yaml

@@ -0,0 +1,9 @@
+id: json-schema-without-schema-path
+version: "1.0.0"
+messages:
+  - role: user
+    content: "Return JSON"
+output:
+  format: json
+  validation_mode: json_schema
+  repair_attempts: 0

internal/promptdef/testdata/messages/user_prompt.tmpl

@@ -0,0 +1,2 @@
+Use transcript:
+{{input "transcript"}}

internal/promptdef/testdata/missing_content_file.yaml

@@ -0,0 +1,9 @@
+id: missing-content-file
+version: "1.0.0"
+messages:
+  - role: user
+    content_file: ./messages/does_not_exist.tmpl
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

internal/promptdef/testdata/missing_id.yaml

@@ -0,0 +1,8 @@
+version: "1.0.0"
+messages:
+  - role: user
+    content: "Hi"
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

internal/promptdef/testdata/neither_content_nor_content_file.yaml

@@ -0,0 +1,8 @@
+id: neither-content-nor-content-file
+version: "1.0.0"
+messages:
+  - role: user
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0

internal/promptdef/testdata/no_messages.yaml

@@ -0,0 +1,6 @@
+id: no-messages
+version: "1.0.0"
+output:
+  format: text
+  validation_mode: none
+  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/unknown_input_field.yaml

@@ -0,0 +1,13 @@
+id: unknown-input-field
+version: "1.0.0"
+inputs:
+  - name: transcript
+    required: true
+    unknown_input_setting: true
+messages:
+  - role: user
+    content: "Hi"
+output:
+  format: text
+  validation_mode: none
+  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_file_backed.yaml

@@ -0,0 +1,14 @@
+id: valid-file-backed
+version: "1.0.0"
+inputs:
+  - name: transcript
+    required: true
+messages:
+  - role: system
+    content: "Return markdown."
+  - role: user
+    content_file: ./messages/user_prompt.tmpl
+output:
+  format: markdown
+  validation_mode: basic
+  repair_attempts: 0

internal/promptdef/testdata/valid_inline.yaml

@@ -0,0 +1,18 @@
+id: valid-inline
+version: "1.0.0"
+inputs:
+  - name: transcript
+    required: true
+    content_type: text/markdown
+    description: Transcript content
+messages:
+  - role: system
+    content: "You are concise."
+  - role: user
+    content: |
+      Summarize:
+      {{input "transcript"}}
+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/promptdef/testdata/with_default_profile.yaml

@@ -0,0 +1,13 @@
+id: with-default-profile
+version: "1.0.0"
+default_profile: local-default
+inputs:
+  - name: transcript
+    required: true
+messages:
+  - role: user
+    content: "Write output"
+output:
+  format: text
+  validation_mode: none
+  repair_attempts: 0