Document Promptkit v0.5.0

README.md

@@ -33,6 +33,9 @@ boundary and constraints that framework work must preserve.
 
 ## Release Guidance
 
+Consumers upgrading from `v0.4.0` to `v0.5.0` should read the
+[v0.5.0 changelog and migration guide](docs/releases/v0.5.0.md).
+
 Consumers upgrading from `v0.3.0` to `v0.4.0` should read the
 [v0.4.0 changelog and adoption guide](docs/releases/v0.4.0.md).
 

docs/consumers/pkg-promptkit.md

@@ -40,6 +40,36 @@ validation, and default transport behavior. Source discovery, format
 validation, and profile precedence are defined by the
 [framework format reference](../formats.md).
 
+## Supply Embedded Application Defaults
+
+Use `WithFallbackProfileFS` when an application packages profile definitions
+that should apply unless an operator provides an ordinary configured profile
+with the same ID. For example, an application can embed its defaults while
+continuing to use `ProfileDir` for operator overrides:
+
+```go
+//go:embed profiles/*.yaml
+var applicationProfiles embed.FS
+
+engine, err := promptkit.NewEngine(promptkit.Config{
+	PromptDir:  "prompts",
+	ProfileDir: operatorProfileDir,
+},
+	promptkit.WithFallbackProfileFS(applicationProfiles, "profiles"),
+)
+```
+
+Keep application-owned profile IDs and definitions in the embedded source.
+Use the ordinary configured profile source for operator overrides. Leave
+`operatorProfileDir` empty when the operator did not configure an override
+directory; a non-empty path names an authoritative higher-precedence source,
+so an unavailable or unreadable directory is an error rather than a reason to
+fall back. The
+[framework format reference](../formats.md#source-and-profile-precedence)
+owns the exact profile format and lookup order; the
+[`WithFallbackProfileFS` GoDoc](../../engine.go) owns its option contract and
+validation rules.
+
 ## Inspect A Prompt Before Preparation
 
 Use [`Engine.InspectPrompt`](../../engine.go) to check one configured prompt's
@@ -152,8 +182,8 @@ replace execution settings or the complete output contract.
 The [public value GoDoc](../../types.go) defines nil, empty, zero, replacement,
 copy, and credential behavior. The
 [framework format reference](../formats.md) defines how those request values
-interact with prompt definitions, file-backed profiles, built-ins, schemas,
+interact with prompt definitions, file-backed and application fallback
-and framework defaults.
+profiles, built-ins, schemas, and framework defaults.
 
 For programmatic profiles,
 [`OpenAICompatibleProfile`](../../profiles.go) converts ordinary

docs/development.md

@@ -44,98 +44,3 @@ Start with:
 For cross-cutting changes, follow every applicable row. Do not create
 placeholder documents for packages, APIs, or integrations that do not yet
 exist.
-
-## Maintainer-Run Validation
-
-Promptkit does not currently use hosted CI. Maintainers are responsible for
-running the documented checks before accepting changes. Run the default Go
-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:
-
-```sh
-gofmt -l $(git ls-files '*.go')
-```
-
-The formatting command must produce no paths. Follow every added or changed
-Markdown link and confirm its target exists. Finally, check whitespace:
-
-```sh
-git diff --check
-```
-
-Documentation-only work does not require unrelated new tests, but it still
-requires link validation and `git diff --check`. Run the Go validation whenever
-documentation changes commands, examples, generated output, or another
-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 supports:
-
-```sh
-go test .
-go vet .
-go build .
-```
-
-Filter tests by name without assuming a fixed internal package layout:
-
-```sh
-go test ./... -run 'TestName'
-```
-
-Replace `TestName` with a useful regular expression. Target only paths that
-exist, and consult the internal component overview for their owning
-documentation. A filtered or package-specific run does not replace the
-complete repository validation.
-
-## Coordinated Work With Scriptorium
-
-Promptkit and Scriptorium must remain independently valid. For temporary local
-integration, use either a Go workspace outside both repositories or an
-uncommitted replacement in the consuming module.
-
-If the repositories are sibling directories, run the workspace commands from
-their parent directory:
-
-```sh
-go work init ./promptkit ./scriptorium
-go work sync
-```
-
-Use the workspace only for coordinated local checks. From the same parent
-directory, remove it when finished:
-
-```sh
-rm -f go.work go.work.sum
-```
-
-Alternatively, from the Scriptorium repository root, temporarily point its
-Promptkit dependency at the sibling checkout:
-
-```sh
-go mod edit -replace gitea.maximumdirect.net/eric/promptkit=../promptkit
-```
-
-After coordinated checks, remove the replacement and reconcile module
-metadata:
-
-```sh
-go mod edit -dropreplace gitea.maximumdirect.net/eric/promptkit
-go mod tidy
-```
-
-Never commit `go.work`, `go.work.sum`, or a local filesystem `replace`
-directive. Before committing in either repository, inspect its module files and
-working tree independently. Published consumer versions must depend on a tagged
-Promptkit version, not a workspace, local replacement, or unpublished commit.

docs/formats.md

@@ -188,25 +188,27 @@ they also cannot collide with the standard fields listed in the
 
 Execution settings resolve in this order:
 
-1. framework defaults;
+1. the framework timeout baseline;
 2. the selected backend, when the profile names one;
 3. the selected profile; and
 4. request `ExecutionTargetOverride` values.
 
-The framework defaults are:
+The framework baseline is:
 
 | Setting | Default |
 | --- | --- |
-| `temperature` | `0` |
+| `temperature` | Unspecified and omitted from compatible provider requests unless a profile or runtime override selects it. |
-| `max_tokens` | `0` |
+| `max_tokens` | Unspecified and omitted from compatible provider requests unless a profile or runtime override selects it. |
-| `top_p` | `1` |
+| `top_p` | Unspecified and omitted from compatible provider requests unless a profile or runtime override selects it. |
 | `timeout_seconds` | `600` |
 
-Numeric zero in a file or in-memory profile means that the profile does not
+Numeric zero in a file or in-memory profile does not select a numeric value.
-replace the framework default. Numeric request overrides use pointers, so an
+For `temperature`, `max_tokens`, and `top_p`, it leaves the provider control
-explicit zero is preserved. In particular, an explicit request
+unspecified. For `timeout_seconds`, it retains the framework deadline. Numeric
-`timeout_seconds` of zero disables the per-generation deadline while leaving
+request overrides use pointers, so an explicit zero is retained and sent to
-the caller context and transport timeout intact.
+compatible providers. 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 profile strings replace backend defaults, and non-empty request
 strings replace both. Request reasoning is the exception: a nil
@@ -231,14 +233,18 @@ default.
 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
+2. the ordinary configured source selected by a profile file, `fs.FS`, or
-3. embedded built-in profiles.
+   configured profile directory;
+3. application fallback profiles supplied with `WithFallbackProfileFS`; and
+4. embedded built-in profiles.
 
-A higher-precedence source falls back only when the profile is absent. An
+A profile source supplies a complete definition; definitions and their fields
-invalid matching profile is an error and does not fall back. In-memory
+are not merged across sources. A higher-precedence source falls back only when
-`Profile` values follow the same ranges as YAML profiles. They use
+the requested profile ID is absent. An invalid matching profile is an error and
-`APIKeyRequired` for request-scoped credentials instead of `api_key_env`.
+does not fall back. In-memory `Profile` values follow the same ranges as YAML
-Preparation and exact profile inspection use this same source precedence.
+profiles. They use `APIKeyRequired` for request-scoped credentials instead of
+`api_key_env`. Preparation and exact profile inspection use this same source
+precedence.
 
 ## Built-In Profile Catalog
 
@@ -246,8 +252,8 @@ Every built-in selects the `openrouter` backend. The engine's built-in backend
 registry supplies `https://openrouter.ai/api/v1` and the environment-variable
 name `OPENROUTER_API_KEY`, so individual profiles contain only model and
 generation settings. Built-in profile files do not repeat those connection
-values. A custom or in-memory profile with the same profile ID takes
+values. A configured, application fallback, or in-memory profile with the same
-precedence.
+profile ID takes precedence.
 
 | Provider | ID | Model |
 | --- | --- | --- |

docs/integrations/openai-compatible-chat.md

@@ -53,8 +53,9 @@ never also sent as a session header.
 
 The client conditionally includes:
 
-- `temperature`, `max_tokens`, and `top_p` when non-zero or explicitly
+- `temperature`, `max_tokens`, and `top_p` only when selected by a profile or
-  present;
+  runtime override, including an explicit runtime zero; they are absent when
+  unspecified;
 - non-empty `service_tier` and effective `reasoning_effort`; an explicitly
   disabled reasoning setting is empty and therefore omitted; and
 - `response_format` for JSON Schema structured output, including its name,

docs/internal/overview.md

@@ -11,7 +11,7 @@ contributor workflow and validation.
 
 | Component | Implemented responsibility | References |
 | --- | --- | --- |
-| Root `promptkit` package | Provides the supported engine facade, source, backend-registration, and injection options, public request, result, prompt-inspection, and profile-inspection values, opaque prepared-execution handles, profile construction, extension interfaces, value conversion, redacted formatting, typed capacity errors, public error mapping, and engine-local assembly. | [Package GoDoc](../../doc.go), [prepared execution](../../prepared_execution.go), [backend API](../../backends.go), [engine assembly](../../engine.go) |
+| Root `promptkit` package | Provides the supported engine facade, source, backend-registration, and injection options, public request, result, prompt-inspection, and profile-inspection values, opaque prepared-execution handles, profile construction, extension interfaces, value conversion, redacted formatting, typed capacity errors, public error mapping, and engine-local profile-source assembly including application fallbacks. | [Package GoDoc](../../doc.go), [prepared execution](../../prepared_execution.go), [backend API](../../backends.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) |
 | `examples/go-library/run` | Demonstrates an offline downstream consumer using a prompt file, in-memory profile, inline input, an injected deterministic model client, and `Run`. It is not a public library package. | [Example program](../../examples/go-library/run/main.go) |
 | `internal/backend` | Constructs each engine's immutable registry from the built-in OpenRouter definition and consumer additions, validates and defensively copies definitions through the shared JSON-value package, and consumes the LLM-owned OpenAI-compatible reserved request-field rule. | [Backend registry](../../internal/backend/registry.go) |
@@ -22,7 +22,7 @@ contributor workflow and validation.
 | `internal/jsonvalue` | Validates and deeply copies JSON-compatible extra-parameter and prepared-schema trees while preserving supported concrete value types. | [JSON values](../../internal/jsonvalue/jsonvalue.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, including backend selection, 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 profile catalog, whose entries select OpenRouter, and combines it with an optional primary repository. | [Built-in catalog](../formats.md#built-in-profile-catalog), [repository](../../internal/profile/builtin/repository.go) |
+| `internal/profile/builtin` | Embeds the built-in profile catalog, whose entries select OpenRouter. | [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 and creates frozen validation plans for prepared execution. | [Framework formats](../formats.md#schemas), [internal sources and validation](sources.md) |

docs/internal/sources.md

@@ -28,26 +28,30 @@ duplicate detection, and source containment:
 ## 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
+operating-system filesystem or an `fs.FS`. Its overlay repository consults the
-with fallback only when the primary reports that a profile is absent. Strict
+next repository only when the higher-precedence repository reports that a
-YAML decoding recognizes the optional `backend` field, trims its value, and
+profile is absent. Strict YAML decoding recognizes the optional `backend`
-requires a model plus at least one non-blank backend or endpoint. Loading does
+field, trims its value, and requires a model plus at least one non-blank
-not check registry membership because the available registry belongs to the
+backend or endpoint. Loading does not check registry membership because the
-assembled engine; the runner checks membership during preparation and exact
+available registry belongs to the assembled engine; the runner checks
-profile inspection.
+membership during preparation and exact profile inspection.
+
+The root engine assembles profile repositories in precedence order: in-memory
+profiles, one ordinary configured source, an application fallback source, then
+the embedded built-in catalog. An explicit file or `fs.FS` profile source
+replaces `Config.ProfileDir` within the ordinary configured-source category.
 
 Exact profile inspection performs one point-in-time lookup through those
 profile sources and checks the resolved target without reading prompt, input,
 or schema sources. It does not retain that lookup for a later execution.
 
-`internal/profile/builtin` embeds the maintained built-in profile catalog and
+`internal/profile/builtin` embeds the maintained built-in profile catalog.
-can place a caller-selected repository ahead of that catalog. Every embedded
+Every embedded profile selects `openrouter` and inherits its endpoint and
-profile selects `openrouter` and inherits its endpoint and credential
+credential environment-variable name from the built-in backend registry rather
-environment-variable name from the built-in backend registry rather than
+than repeating those values. Profile loading and overlay behavior are owned by
-repeating those values. Profile behavior is owned by the
+the [profile repository tests](../../internal/profile/repository_test.go),
-[profile repository tests](../../internal/profile/repository_test.go), while
+while catalog completeness, the backend-selection invariant, and duplicate IDs
-catalog completeness, the backend-selection invariant, duplicate IDs, and
+are owned by the
-overlay behavior are owned by the
 [built-in repository tests](../../internal/profile/builtin/repository_test.go).
 
 ## Ordinary Artifacts

docs/releases/v0.4.0.md

@@ -126,9 +126,9 @@ later request must provide a direct credential. Environment-variable names may
 be reported, but inspection does not read credential values or require the
 named variable to be populated.
 
-Inspection applies the ordinary configured and built-in profile precedence and
+Inspection applies the engine's profile source precedence and resolves any
-resolves any selected backend. It does not load a prompt, render content,
+selected backend. It does not load a prompt, render content, reserve capacity,
-reserve capacity, or contact a model.
+or contact a model.
 
 See the
 [profile-inspection consumer guide](../consumers/pkg-promptkit.md#inspect-a-profile-before-prompt-work)

docs/releases/v0.5.0.md

@@ -0,0 +1,125 @@
+# Promptkit v0.5.0
+
+This supplemental changelog and migration guide summarizes the consumer-facing
+changes from `v0.4.0` to `v0.5.0`. The annotated `v0.5.0` tag is the
+authoritative release record. Exact current contracts belong to the linked
+GoDoc and durable documentation.
+
+## Summary
+
+`v0.5.0` makes provider requests less prescriptive and adds an application
+fallback layer for profile definitions:
+
+- unset optional provider controls are omitted from OpenAI-compatible request
+  bodies instead of being populated with framework values; and
+- `WithFallbackProfileFS` lets an application package profile defaults that
+  operators can override through the existing ordinary profile sources.
+
+These changes let compatible providers apply their own model defaults while
+giving applications stable embedded profile IDs without weakening operator
+configuration precedence.
+
+## Compatibility
+
+The release adds one public function and removes no public declaration.
+Existing source code should continue to compile.
+
+There is one intentional behavior change: when no profile or runtime override
+selects `top_p`, Promptkit no longer sends the former framework value of `1`.
+It omits `top_p` and lets the provider choose its behavior. Unset
+`temperature` and `max_tokens` are likewise omitted. Explicit nonzero profile
+values and runtime values—including explicit runtime zero values—retain their
+precedence and wire effect.
+
+Consumers that relied on Promptkit always sending `top_p: 1` should add that
+value to the relevant profile or runtime override before upgrading. Consumers
+that did not rely on the implicit sampling value require no migration.
+
+Application fallback profiles are opt-in. Engines that do not call
+`WithFallbackProfileFS` retain the previous profile-source behavior.
+
+## Upgrade
+
+Update the module dependency with:
+
+```sh
+go get gitea.maximumdirect.net/eric/promptkit@v0.5.0
+go mod tidy
+```
+
+Run the consuming project's ordinary and race-enabled tests after upgrading.
+If request payloads or model behavior are asserted in fixtures, review them for
+the optional-parameter omission described below.
+
+## Omitted Optional Provider Controls
+
+The built-in OpenAI-compatible client now includes `temperature`,
+`max_tokens`, and `top_p` only when a profile or runtime override selects the
+value. An explicit runtime zero remains present because runtime override
+pointers distinguish zero from an unspecified value.
+
+Promptkit's positive generation deadline remains a framework concern and is
+not a provider request-body default. Required request fields, session IDs,
+structured output, reasoning selection, credentials, and explicit extra
+parameters retain their existing behavior.
+
+See the [framework default and precedence reference](../formats.md#defaults-and-overrides),
+the [`ExecutionTargetOverride` GoDoc](../../types.go), and the
+[OpenAI-compatible request-body contract](../integrations/openai-compatible-chat.md#request-body)
+for current details.
+
+## Embedded Application Fallback Profiles
+
+Applications can package ordinary profile YAML in an `fs.FS` and register it
+as a fallback source:
+
+```go
+//go:embed profiles/*.yaml
+var applicationProfiles embed.FS
+
+engine, err := promptkit.NewEngine(promptkit.Config{
+	PromptDir:  "prompts",
+	ProfileDir: operatorProfileDir,
+},
+	promptkit.WithFallbackProfileFS(applicationProfiles, "profiles"),
+)
+```
+
+Leave `operatorProfileDir` empty when no operator source is configured. A
+configured ordinary source is authoritative: a matching definition overrides
+the application fallback, while a read or validation failure remains an error
+instead of silently reaching a lower layer.
+
+Profile definitions resolve in this order:
+
+1. in-memory profiles supplied with `WithProfiles`;
+2. the ordinary configured source selected by `WithProfileFile`,
+   `WithProfileFS`, or `Config.ProfileDir`;
+3. the application source supplied with `WithFallbackProfileFS`; and
+4. Promptkit's embedded built-in profiles.
+
+Only an absent profile ID falls through. Sources provide complete profiles and
+do not merge fields. Loading remains lazy, and the new source uses the existing
+strict profile YAML and credential rules.
+
+See the
+[embedded-default consumer guidance](../consumers/pkg-promptkit.md#supply-embedded-application-defaults),
+the [`WithFallbackProfileFS` GoDoc](../../engine.go), and the
+[profile source reference](../formats.md#source-and-profile-precedence) for
+current details.
+
+## Public API Changes
+
+The release adds:
+
+- `WithFallbackProfileFS`.
+
+No public declaration was removed or changed.
+
+## Consumer Action
+
+- Review any workflow that depended on Promptkit's implicit `top_p: 1` and
+  configure the value explicitly when required.
+- Optionally adopt `WithFallbackProfileFS` when an application should package
+  overridable profile defaults.
+- Run consumer tests after updating the module dependency.

docs/roadmap/deferred.md

@@ -0,0 +1,82 @@
+# Deferred Feature Ideas
+
+## Purpose
+
+This document catalogs feature ideas that remain potentially useful but have
+been deliberately postponed. These ideas are not awaiting ordinary selection
+from the [future feature catalog](future.md); each has a stated reason to wait
+and should be reconsidered only when its trigger becomes relevant.
+
+Deferred entries are not commitments, schedules, active implementation plans,
+or descriptions of current behavior. When an entry is reactivated, move it to
+`future.md` for evaluation or directly into a focused roadmap after its open
+design dependencies have been resolved.
+
+## Deferred Ideas
+
+### Semantic Execution-Target Fingerprints
+
+**Reason for deferral:** A stable digest requires a deliberate semantic-
+equality and versioning design. Notarius can safely use conservative source
+hashes and a Promptkit release marker today, while Weatherreporter does not
+currently reuse LLM-dependent checkpoints.
+
+Promptkit could expose an opaque equality value for a resolved profile and its
+effective generation target. This would let checkpointing consumers detect
+generation-affecting configuration changes without hashing YAML presentation
+or depending on Promptkit's built-in catalog layout.
+
+The digest should change with semantically relevant state such as the resolved
+model, endpoint, backend routing identity, request defaults, extra parameters,
+profile generation settings, and selected built-in profile semantics. It
+should exclude credential values, concurrency and queue policy, source paths,
+comments, formatting, and other representation-only changes. Whether a
+credential environment-variable name affects equality must be decided
+explicitly. The encoding should remain opaque and internally versioned so
+Promptkit can deliberately invalidate earlier digests when its resolution
+semantics change.
+
+Reconsider this idea when a downstream consumer needs Promptkit-owned
+checkpoint equality or when a broader semantic identity design is selected.
+
+### Eager Source Validation
+
+**Reason for deferral:** Exact prompt and profile inspection may already
+provide a sufficiently small validation surface. Experience from downstream
+adoption should establish whether an engine-wide operation would add enough
+value to justify its broader contract.
+
+Promptkit could provide an explicit offline operation that discovers and
+structurally validates configured prompt, profile, and schema sources without
+model generation. The normal `NewEngine` path would remain lazy.
+
+An eager operation would need coherent handling for duplicate prompt IDs and
+versions, strict YAML decoding, referenced content files, profile/backend
+membership, schema syntax and transitive references, context cancellation,
+and source-specific public errors. Credential declarations must remain
+separate from credential values; checking current environment availability,
+if supported at all, should be an explicit option and must not expose secrets.
+
+Reconsider this idea after downstream use of `InspectPrompt`,
+`InspectProfile`, and fixture-based preparation demonstrates a concrete gap.
+
+### Structured Generation Errors
+
+**Reason for deferral:** Existing `ErrLLMGenerate` classification, preserved
+injected-client errors, and prepared execution details currently provide the
+necessary failure boundary. A typed error should wait for stronger downstream
+demand and a transport-neutral field design.
+
+Promptkit could expose safe structured generation context through
+`errors.As` while preserving `errors.Is(err, ErrLLMGenerate)`. Potential
+fields include the selected backend ID and model plus an optional HTTP status
+when the built-in OpenAI-compatible transport supplies one.
+
+The design must not expose provider response bodies, endpoints, credential
+environment names or values, request content, or generated content. It should
+not duplicate prompt and profile provenance already available from a prepared
+execution, and it must preserve the identity of errors returned by injected
+clients. Retry and backoff policy remains a consumer responsibility.
+
+Reconsider this idea when consumers need structured generation diagnostics
+beyond the existing sentinel, wrapped client error, and preparation record.

docs/roadmap/future.md

@@ -12,6 +12,9 @@ consumer value, and important scope boundaries. Defer API design,
 implementation details, sequencing, and acceptance criteria until an idea is
 selected.
 
+Ideas that have been deliberately postponed rather than left available for
+ordinary selection belong in the [deferred catalog](deferred.md).
+
 ## Using This Catalog
 
 - Add an idea when its purpose and likely value can be stated clearly.
@@ -23,6 +26,8 @@ selected.
 - When an idea is selected, move its active planning to a focused roadmap or,
   when it requires a durable architectural decision, an ADR. Update
   current-state documentation only when implementation lands.
+- Move an idea to `deferred.md` when maintainers decide to retain it but wait
+  for a stated design dependency, demand signal, or reconsideration trigger.
 - Remove ideas that are no longer relevant. Retain a rejected idea only when
   its rationale is likely to prevent repeated reconsideration.
 

docs/roadmap/notarius-promptkit-wishlist.md

@@ -1,245 +0,0 @@
-# Notarius PromptKit Wishlist
-
-## Purpose
-
-This document records features and interface changes that would be useful
-additions to PromptKit from the perspective of the maintainers of Notarius, a
-downstream application that consumes PromptKit.
-
-PromptKit now provides the capabilities Notarius currently needs. The
-remaining deferred ideas are optional opportunities to improve checkpointing
-and operational observability.
-
-The examples are API sketches intended to communicate the desired capability,
-not prescriptive names or finalized Go contracts.
-
-## Priority 1: Atomic Execution With Prepared Details
-
-**Disposition:** Implemented through [`Engine.PrepareExecution` and
-`Engine.RunPrepared`](../../engine.go). See the
-[consumer guidance](../consumers/pkg-promptkit.md#prepare-now-and-execute-the-same-snapshot-later).
-A separate `RunDetailed` method is not cataloged.
-
-### Downstream need
-
-Notarius needs both:
-
-- the completed `RunResult`; and
-- the rendered messages, effective output contract, hashes, and other
-  preparation details exposed by `PreparedRun`.
-
-Notarius uses the prepared details to construct redaction-aware debug bundles
-and retain enough information to diagnose model behavior.
-
-### Implemented behavior
-
-Notarius can prepare one frozen execution snapshot, retain a caller-owned and
-credential-redacted `Details` value for its debug bundle, and execute the same
-snapshot through `RunPrepared`. The opaque handle is engine-bound and
-single-use; an unused handle can be released with `Discard`. The consumer
-guide and exported GoDoc own the exact lifecycle and failure contracts.
-
-### Value to Notarius
-
-This removes duplicate work from PromptKit-backed calls and ensures that
-retained debug material corresponds atomically to the actual execution.
-
-## Priority 2: Prompt-Independent Profile Inspection
-
-**Disposition:** Implemented as
-[`Engine.InspectProfile`](../../engine.go). See the
-[consumer guidance](../consumers/pkg-promptkit.md#inspect-a-profile-before-prompt-work).
-
-### Downstream need
-
-Notarius validates configured pipeline profile IDs before beginning a run. It
-needs to determine whether:
-
-- a profile exists;
-- its referenced backend is registered;
-- its execution target can be resolved; and
-- it declares a credential requirement that the application may need to
-  enforce.
-
-This validation should not require model generation.
-
-### Previous integration
-
-Before profile inspection was available, Notarius constructed a synthetic
-prompt using `testing/fstest.MapFS`, supplied a dummy transcript, and called
-`Engine.Prepare` solely to exercise profile and backend resolution.
-
-### Value to Notarius
-
-The implemented interface eliminates a synthetic production-only prompt
-fixture and establishes a direct, supported contract for configuration-time
-profile and backend validation.
-
-## Priority 3: Semantic Execution-Target Fingerprints
-
-**Disposition:** Deferred pending a separate semantic-equality design for
-resolved execution targets.
-
-### Downstream need
-
-Notarius checkpoints model-backed pipeline stages. A checkpoint must not be
-reused when generation-affecting PromptKit configuration changes.
-
-Notarius therefore needs a stable equality signal for the effective profile
-and backend target used by a pipeline.
-
-### Current integration
-
-Notarius currently constructs this identity itself from:
-
-- a manually maintained marker for the PromptKit release and built-in profile
-  catalog;
-- raw hashes of configured profile files; and
-- a separate hash of the configured conventional local-backend endpoint.
-
-This is safe but conservative and coupled to PromptKit details. Raw file
-hashing also invalidates checkpoints for semantically irrelevant YAML changes,
-such as comments or formatting.
-
-### Requested capability
-
-Expose an opaque semantic digest for a resolved profile and its effective
-generation target. It could be returned by the proposed profile-resolution
-API:
-
-```go
-type ResolvedProfile struct {
-	ProfileID       string
-	BackendID       string
-	EffectiveTarget ExecutionTarget
-	ExecutionDigest string
-}
-```
-
-Alternatively, PromptKit could expose a dedicated method such as
-`ProfileExecutionDigest(profileID)`.
-
-### Desired equality semantics
-
-The digest should change when generation-affecting state changes, including:
-
-- resolved model and endpoint;
-- backend routing identity;
-- backend request defaults and extra parameters;
-- profile generation parameters; and
-- the semantic identity of any selected built-in profile.
-
-The digest should not incorporate:
-
-- credential values;
-- concurrency or queue capacity;
-- filesystem source paths;
-- YAML comments or formatting; or
-- other settings that affect scheduling or source representation without
-  changing the generation target.
-
-The credential environment-variable name may need to participate if changing
-it can select a materially different provider account or target. PromptKit
-should define this deliberately while continuing to exclude the resolved
-secret value.
-
-### Design considerations
-
-- Treat the digest as an opaque equality value rather than a public encoding
-  of internal structures.
-- Document which categories of change affect equality.
-- Include a versioned semantic marker internally so PromptKit can deliberately
-  invalidate old digests when its resolution semantics change.
-- Prefer a per-profile digest over a digest of every profile known to an
-  engine. Notarius generally knows which profiles a resolved pipeline uses.
-- Do not require consumers to know PromptKit's built-in catalog version.
-
-### Value to Notarius
-
-This would let Notarius remove its PromptKit release marker and raw
-profile-source fingerprinting, reduce unnecessary checkpoint invalidation, and
-delegate execution-target equality to the component that owns target
-resolution.
-
-## Priority 4: Structured Capacity Errors
-
-**Disposition:** Implemented behavior. See the consumer guide's
-[Handle Errors](../consumers/pkg-promptkit.md#handle-errors) section.
-
-### Downstream need
-
-Notarius translates PromptKit backend-capacity rejection into a
-provider-neutral application error. When multiple backends are active,
-operators would benefit from knowing which backend rejected admission without
-parsing an error string or exposing endpoint details.
-
-### Implemented behavior
-
-PromptKit now retains the broad capacity classification while allowing
-Notarius to obtain the selected backend ID without parsing diagnostic text.
-The consumer guide owns the application workflow, including retry and backoff
-policy.
-
-### Value to Notarius
-
-This improves operational diagnostics and future metrics while preserving
-the provider-neutral error boundary used by Notarius.
-
-## Capabilities PromptKit Already Provides Well
-
-The current PromptKit boundary is sufficient for Notarius's implemented
-behavior. In particular, PromptKit already provides:
-
-- filesystem, `fs.FS`, and programmatic prompt, profile, and schema sources;
-- offline preparation without model execution;
-- structured output and content validation;
-- direct session propagation;
-- tri-state per-run reasoning overrides;
-- selected profile, backend, model, endpoint, effective parameters, hashes, and
-  token-usage provenance;
-- endpoint-only profiles;
-- the conventional `local` backend helper;
-- arbitrary engine-scoped `Backend` registrations;
-- backend authentication environment names, extra parameters, concurrency
-  limits, and queue-capacity policies;
-- provider-client and artifact-reader extension interfaces;
-- context cancellation; and
-- useful public error sentinels, including profile absence and capacity
-  exhaustion.
-
-The wishlist does not imply that Notarius needs PromptKit to broaden its core
-responsibilities. It primarily asks for more direct access to information and
-operations that PromptKit already computes internally.
-
-## Responsibilities That Should Remain In Notarius
-
-The following concerns belong to the downstream application and should not
-move into PromptKit for the sake of Notarius:
-
-- pipeline staging, dependencies, and generated references;
-- application-wide scheduling across providers and backends;
-- module and validation retry policy;
-- checkpoints, resume, and recomputation;
-- durable run artifacts and manifests;
-- D&D prompts, schemas, extractors, validators, and normalizers;
-- Notarius configuration-file parsing and precedence;
-- domain-specific prompt-cache prefix policy; and
-- application-specific redaction, retention, and debug-bundle policy.
-
-PromptKit's complete `Backend` API already supports custom IDs, multiple local
-endpoints, authentication, extra parameters, and explicit queue policies.
-Whether Notarius exposes those capabilities in its own configuration is an
-application-policy decision, not an upstream PromptKit gap.
-
-## Suggested Upstream Sequence
-
-For downstream adoption and any remaining upstream work, the useful order is:
-
-1. Adopt prepared execution for atomic details and results.
-2. Add a semantic execution-target digest, preferably alongside profile
-   inspection.
-3. Use the implemented typed capacity error where backend admission diagnostics
-   are needed.
-
-The first removes the concrete execution workaround. The second would improve
-checkpoint correctness and reduce coupling. The third is operational polish.

docs/roadmap/weatherreporter-promptkit-wishlist.md

@@ -1,331 +0,0 @@
-# Weatherreporter PromptKit Wishlist
-
-## Purpose
-
-This document records features and interface changes that would be useful
-additions to PromptKit from the perspective of the maintainers of
-Weatherreporter, a downstream application planning to replace its Scriptorium
-CLI integration with PromptKit.
-
-PromptKit now provides the capabilities Weatherreporter needs for the
-migration. The remaining deferred ideas are optional opportunities to validate
-configuration earlier and improve durable failure diagnostics.
-
-The examples are API sketches intended to communicate the desired capability,
-not prescriptive names or finalized Go contracts. The related
-[Notarius PromptKit wishlist](notarius-promptkit-wishlist.md) proposes several
-overlapping features from another downstream consumer's perspective.
-
-## Priority 1: Executable Preparation Handles
-
-**Disposition:** Implemented as [`Engine.PrepareExecution` and
-`Engine.RunPrepared`](../../engine.go). See the
-[consumer guidance](../consumers/pkg-promptkit.md#prepare-now-and-execute-the-same-snapshot-later).
-
-### Downstream need
-
-Weatherreporter treats prompt preparation as a durable preflight boundary. It
-needs to:
-
-1. prepare the exact request that will be executed;
-2. persist a safe preparation record before starting the provider call; and
-3. execute without reloading or rerendering prompt, profile, schema, or input
-   sources.
-
-Persisting preflight before generation leaves useful evidence when a provider
-call fails or the process is interrupted during generation.
-
-### Implemented behavior
-
-Weatherreporter can prepare one frozen execution snapshot, persist a
-caller-owned and credential-redacted `Details` value, and execute that same
-snapshot through `RunPrepared`. The opaque handle is engine-bound and
-single-use; an unused handle can be released with `Discard`. The consumer
-guide and exported GoDoc own the exact lifecycle, credential, cancellation,
-and capacity contracts.
-
-### Value to Weatherreporter
-
-This preserves Weatherreporter's durable preflight behavior, removes duplicate
-work, eliminates the source-consistency window, and ensures that persisted
-provenance describes the actual execution.
-
-## Priority 2: Prompt-Definition Inspection
-
-**Disposition:** Implemented as
-[`Engine.InspectPrompt`](../../engine.go). See the
-[consumer guidance](../consumers/pkg-promptkit.md#inspect-a-prompt-before-preparation).
-
-### Downstream need
-
-Weatherreporter has a fixed registry of seven report definitions. Each report
-selects a prompt ID and one of two output workflows:
-
-- direct Markdown; or
-- structured generated text followed by application-owned domain validation
-  and Markdown template rendering.
-
-Weatherreporter will embed the PromptKit prompt definitions and private
-response schemas that implement those reports. It needs to validate that the
-report registry and embedded prompt corpus agree before weather collection or
-provider execution.
-
-### Previous integration option
-
-Before prompt inspection was available, Weatherreporter could maintain
-synthetic data-package fixtures and call `Engine.Prepare` for every report
-prompt during tests. Runtime validation could also occur through the ordinary
-per-report preparation stage.
-
-This required complete placeholder inputs and profile resolution when the
-application primarily wanted to inspect prompt identity and declared contracts.
-
-### Value to Weatherreporter
-
-The implemented interface lets Weatherreporter directly verify that every
-report prompt exists, requires the curated `data_package` input, and declares
-the expected Markdown or JSON Schema output contract. It reduces synthetic
-test setup and moves failures ahead of weather collection.
-
-## Priority 3: Prompt-Independent Profile Inspection
-
-**Disposition:** Implemented as
-[`Engine.InspectProfile`](../../engine.go). See the
-[consumer guidance](../consumers/pkg-promptkit.md#inspect-a-profile-before-prompt-work).
-
-### Downstream need
-
-Weatherreporter will allow operators to select an external PromptKit profile
-source and may allow an explicit profile override. It needs to reject a missing
-profile, unknown backend, or malformed execution target before collecting
-weather data or writing report artifacts, and to apply its own policy to a
-reported credential requirement.
-
-### Value to Weatherreporter
-
-The implemented interface improves fail-fast configuration validation and gives
-operator-facing errors direct profile and backend context. It remains optional
-for the initial migration.
-
-## Priority 4: Eager Source Validation
-
-**Disposition:** Deferred until prompt and profile inspection have been used
-to determine whether a broader engine-wide validation operation is still
-needed.
-
-### Downstream need
-
-PromptKit deliberately defers reading and validating filesystem and `fs.FS`
-prompt, profile, and schema content until a request needs it. Weatherreporter
-has a small fixed embedded prompt corpus and one optional external profile
-source. It would benefit from an explicit offline validation operation for
-tests, startup diagnostics, and configuration checks.
-
-### Current integration option
-
-Weatherreporter can prepare every report prompt with fixture inputs and inspect
-any explicit profiles individually. That provides strong coverage but requires
-consumer-maintained traversal and synthetic material.
-
-### Requested capability
-
-Consider an opt-in source-validation operation:
-
-```go
-type SourceValidationOptions struct {
-	RequireCredentials bool
-}
-
-func (e *Engine) ValidateSources(
-	ctx context.Context,
-	opts SourceValidationOptions,
-) error
-```
-
-The operation should eagerly discover and structurally validate the configured
-prompt, profile, and schema sources without model generation.
-
-### Design considerations
-
-- Keep deferred validation as the normal `NewEngine` behavior.
-- Make eager validation an explicit consumer choice.
-- Validate duplicate IDs and versions, strict YAML decoding, referenced content
-  files, profile/backend membership, schema syntax, and schema references.
-- Distinguish structural credential declarations from current environment
-  availability.
-- Do not read or expose credential values when credential availability is not
-  requested.
-- Preserve source-specific public error identities and useful path context.
-- Respect context cancellation during filesystem discovery and schema work.
-- Consider whether exact prompt and profile inspection APIs already provide a
-  smaller sufficient surface before adding an engine-wide operation.
-
-### Value to Weatherreporter
-
-This would simplify offline corpus checks and catch malformed operator profile
-sources before report work begins. It is helpful but lower priority than exact
-prompt and profile inspection.
-
-## Priority 5: Structured Generation Errors
-
-**Disposition:** Deferred pending stronger downstream demand and a narrower
-design that does not duplicate prepared provenance or impose HTTP-specific
-fields on injected model clients.
-
-### Downstream need
-
-Weatherreporter preserves redacted, inspectable failure receipts for report
-runs. When model generation fails operationally, it needs to classify the
-failure and retain safe execution context without parsing error prose.
-
-Prompt preparation already supplies selected profile, backend, and model
-identity. Provider status classification would add useful operator context,
-especially when the built-in OpenAI-compatible client receives a non-success
-HTTP status.
-
-### Current integration option
-
-PromptKit exposes `ErrLLMGenerate` and preserves injected client errors through
-`errors.Is`. Weatherreporter can reliably classify generation failure and use
-its preparation record for profile, backend, and model provenance. Any further
-diagnostic detail remains a redacted error string.
-
-### Requested capability
-
-Consider a typed generation error that continues to match `ErrLLMGenerate`:
-
-```go
-type GenerationError struct {
-	BackendID string
-	Model     string
-	StatusCode int
-}
-```
-
-The exact fields may differ. The useful contract is safe structured context
-available through `errors.As`, while `errors.Is(err, ErrLLMGenerate)` remains
-compatible.
-
-### Design considerations
-
-- Include only fields that PromptKit knows reliably and can expose safely.
-- Treat an HTTP status as optional because injected model clients may not use
-  HTTP.
-- Do not expose provider response bodies, endpoints, credential environment
-  names, credential values, request content, or generated content.
-- Do not make a structured error a second source of prompt/profile provenance
-  already present in a prepared execution.
-- Preserve injected client error identity.
-- Keep retry and backoff policy with the consuming application.
-
-### Value to Weatherreporter
-
-This would improve durable failure receipts and troubleshooting, particularly
-for built-in transport failures. It is not required if preparation details and
-the existing sentinel remain available.
-
-## Lower-Priority Shared Wishlist Items
-
-### Structured Capacity Errors
-
-**Disposition:** Implemented behavior. See the consumer guide's
-[Handle Errors](../consumers/pkg-promptkit.md#handle-errors) section.
-
-PromptKit now exposes the stable backend ID for capacity rejection without
-requiring Weatherreporter to parse error text.
-
-Weatherreporter currently generates batch reports sequentially and constructs
-one engine per invocation, so engine-local capacity exhaustion is unlikely in
-the initial design. The typed error becomes more valuable if report generation
-later becomes concurrent or PromptKit engines become longer-lived.
-It should not block adoption.
-
-### Semantic Execution-Target Fingerprints
-
-**Disposition:** Deferred pending a separate semantic-equality design for
-resolved execution targets.
-
-The semantic target digest proposed by the
-[Notarius wishlist](notarius-promptkit-wishlist.md#priority-3-semantic-execution-target-fingerprints)
-would provide a compact equality signal for audit metadata.
-
-Weatherreporter does not currently reuse LLM-dependent checkpoints. Its Recent
-Changes behavior compares deterministic module snapshots rather than generated
-reports, so the digest has no immediate cache-correctness role. Existing
-PromptKit result metadata is sufficient for the initial integration. A digest
-would still be useful provenance and future-proofing, but it is not a
-migration priority.
-
-## Capabilities PromptKit Already Provides Well
-
-PromptKit already provides the essential Weatherreporter integration surface:
-
-- importable in-process engine construction;
-- filesystem, `fs.FS`, and programmatic prompt, profile, and schema sources;
-- offline preparation without model execution;
-- prepared execution handles for a durable preflight boundary;
-- exact prompt and profile inspection;
-- versioned prompt selection;
-- text, Markdown, JSON, and JSON Schema output contracts;
-- single-pass output validation with raw output retained after completed
-  validation failure;
-- inline input artifacts with provenance URIs and input hashes;
-- selected profile, backend, model, effective target, prompt hashes, timing,
-  and token-usage provenance;
-- endpoint-only profiles and engine-scoped backend registration;
-- injected model-client and artifact-reader interfaces;
-- caller cancellation, generation timeout, and transport timeout behavior; and
-- public error sentinels for configuration, prompt, profile, artifact,
-  validation, capacity, and generation failures; and
-- structured backend identity for capacity rejection.
-
-These capabilities are sufficient for Weatherreporter to adopt PromptKit
-without waiting for new upstream work.
-
-## Responsibilities That Should Remain In Weatherreporter
-
-The following concerns belong to Weatherreporter and should not move into
-PromptKit:
-
-- report definitions, valid periods, batches, and output naming;
-- application prompt content and private report response schemas;
-- deterministic weather facts, modules, and Recent Changes;
-- curated `data_package` construction and persistence;
-- generated-text domain validation and Markdown template rendering;
-- managed artifact paths, atomic writes, metadata, and inspection commands;
-- preparation, execution, raw-output, and failure-receipt schemas;
-- CLI configuration loading and precedence;
-- debug enablement, redaction, placement, sensitivity, and retention;
-- distributor notification;
-- batch continuation and any future retry policy; and
-- application-level compatibility and migration policy.
-
-## Suggested Upstream Sequence
-
-For downstream adoption and any remaining upstream work, the useful order is:
-
-1. Adopt the implemented executable preparation handles.
-2. Consider eager source validation after evaluating whether the two exact
-   inspection APIs are sufficient.
-3. Add structured generation errors.
-4. Use structured capacity errors and consider semantic execution-target
-   fingerprints as lower-priority operational improvements.
-
-The first item removes the material integration workaround. Prompt and profile
-inspection improve fail-fast validation. The remaining items are optional
-ergonomic and diagnostic improvements.
-
-## Adoption Sequencing
-
-Weatherreporter should not wait for the deferred wishlist items. The current
-PromptKit interface is sufficient when Weatherreporter:
-
-- embeds immutable prompt and schema assets;
-- supplies immutable inline data-package bytes;
-- constructs one engine per CLI invocation;
-- prepares an execution, persists selected `Details`, and calls
-  `RunPrepared`; and
-- keeps PromptKit behind a weatherreporter-owned adapter contract.
-
-Prompt inspection, profile inspection, source validation, structured errors,
-capacity details, and semantic fingerprints should not gate adoption.

engine.go

@@ -98,9 +98,10 @@ type Config struct {
 	// It is required unless a WithPromptFS or WithPromptFile option supplies the
 	// prompt source.
 	PromptDir string
-	// ProfileDir is an optional directory whose profiles take precedence over
+	// ProfileDir is an optional ordinary configured source whose profiles take
-	// embedded built-in profiles. An empty value selects only built-ins unless
+	// precedence over application fallback and embedded built-in profiles. An
-	// profile options are also supplied.
+	// empty value selects the lower-precedence sources unless a profile-source
+	// option supplies the ordinary source.
 	ProfileDir string
 	// SchemaDir is the root for JSON Schema files. An empty value uses the
 	// current directory. WithSchemaFS or WithSchemaFile replaces this source.
@@ -119,12 +120,12 @@ type Config struct {
 // Option customizes engine construction.
 //
 // NewEngine applies options in argument order and ignores nil options. Within
-// each prompt-source, profile-source, in-memory-profile, schema-source,
+// each prompt-source, ordinary-profile-source, fallback-profile-source,
-// model-client, and artifact-reader category, the last non-nil valid option
+// in-memory-profile, schema-source, model-client, and artifact-reader
-// replaces earlier options in that category. WithBackend is the additive
+// category, the last non-nil valid option replaces earlier options in that
-// exception: unique registrations accumulate, and a repeated backend ID is an
+// category. WithBackend is the additive exception: unique registrations
-// error rather than a replacement. An invalid option fails construction even
+// accumulate, and a repeated backend ID is an error rather than a replacement.
-// if a later option would replace it.
+// An invalid option fails construction even if a later option would replace it.
 type Option interface {
 	apply(*engineOptions) error
 }
@@ -136,18 +137,20 @@ func (f optionFunc) apply(options *engineOptions) error {
 }
 
 type engineOptions struct {
-	llmClient       llm.Client
+	llmClient             llm.Client
-	artifactReader  artifactadapter.Reader
+	artifactReader        artifactadapter.Reader
-	promptDefs      promptdef.Repository
+	promptDefs            promptdef.Repository
-	profiles        profile.Repository
+	profiles              profile.Repository
-	memoryProfiles  profile.Repository
+	fallbackProfiles      profile.Repository
-	backends        []domain.Backend
+	memoryProfiles        profile.Repository
-	validator       validate.Validator
+	backends              []domain.Backend
-	promptSource    bool
+	validator             validate.Validator
-	profileSource   bool
+	promptSource          bool
-	memorySource    bool
+	profileSource         bool
-	validatorSource bool
+	fallbackProfileSource bool
-	artifactSource  bool
+	memorySource          bool
+	validatorSource       bool
+	artifactSource        bool
 }
 
 // WithLLMClient replaces the built-in model client used by [Engine.Run] and
@@ -224,12 +227,12 @@ func WithPromptFile(path string) Option {
 
 // WithProfileFS loads execution profiles from fsys under root.
 //
-// Profiles from this source overlay built-in profiles. Profile YAML must use
+// Profiles from this ordinary configured source take precedence over
-// api_key_env for environment-based credentials; raw API keys are rejected.
+// application fallback and built-in profiles. Profile YAML must use api_key_env
-// fsys must be non-nil and root must be non-empty; otherwise NewEngine fails
+// for environment-based credentials; raw API keys are rejected. fsys must be
-// with ErrInvalidConfig. This option replaces Config.ProfileDir and earlier
+// non-nil and root must be non-empty; otherwise NewEngine fails with
-// file or FS profile-source options, but remains below WithProfiles in
+// ErrInvalidConfig. This option replaces Config.ProfileDir and earlier file or
-// precedence.
+// FS profile-source options, but remains below WithProfiles in precedence.
 func WithProfileFS(fsys fs.FS, root string) Option {
 	return optionFunc(func(options *engineOptions) error {
 		if fsys == nil {
@@ -246,11 +249,12 @@ func WithProfileFS(fsys fs.FS, root string) Option {
 
 // 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
+// The profile takes precedence over application fallback and built-in profiles.
-// environment-based credentials; raw API keys are rejected. path must name an
+// Profile YAML must use api_key_env for environment-based credentials; raw API
-// existing non-directory file when NewEngine applies the option. This option
+// keys are rejected. path must name an existing non-directory file when
-// replaces Config.ProfileDir and earlier file or FS profile-source options,
+// NewEngine applies the option. This option replaces Config.ProfileDir and
-// but remains below WithProfiles in precedence.
+// earlier file or FS profile-source options, but remains below WithProfiles in
+// precedence.
 func WithProfileFile(path string) Option {
 	return optionFunc(func(options *engineOptions) error {
 		fsys, root, err := fileSource(path)
@@ -263,8 +267,41 @@ func WithProfileFile(path string) Option {
 	})
 }
 
+// WithFallbackProfileFS supplies application-owned fallback profile
+// definitions from fsys under root.
+//
+// Profile lookup checks, in order, profiles supplied by WithProfiles; the
+// ordinary configured source selected by WithProfileFile, WithProfileFS, or
+// Config.ProfileDir; this fallback source; and Promptkit's embedded built-in
+// profiles. Each source supplies a complete profile definition; profile fields
+// are not merged between sources. Only an absent profile ID proceeds to the
+// next source. A matching read, parse, duplicate, validation, or credential
+// format failure stops resolution.
+//
+// Files use the ordinary strict profile YAML and api_key_env credential rules.
+// Loading and validation are lazy: NewEngine validates this option's arguments
+// but does not read profile files. fsys must be non-nil and root must be
+// nonblank; otherwise NewEngine returns an error matching ErrInvalidConfig.
+// Repeating this option replaces the earlier valid fallback source.
+//
+// This option controls profile-definition lookup, not provider or generation
+// failover.
+func WithFallbackProfileFS(fsys fs.FS, root string) Option {
+	return optionFunc(func(options *engineOptions) error {
+		if fsys == nil {
+			return ErrInvalidConfig
+		}
+		if strings.TrimSpace(root) == "" {
+			return ErrInvalidConfig
+		}
+		options.fallbackProfiles = profile.NewFSRepository(fsys, root)
+		options.fallbackProfileSource = true
+		return nil
+	})
+}
+
 // WithProfiles configures in-memory profiles that take precedence over
-// configured profile files and built-in profiles.
+// ordinary configured, application fallback, and built-in profiles.
 //
 // NewEngine validates and copies every profile. IDs must be unique within one
 // call. An invalid profile, duplicate ID, or unsupported ExtraParams value
@@ -350,13 +387,7 @@ func NewEngine(cfg Config, opts ...Option) (*Engine, error) {
 		promptDefs = promptdef.NewFilesystemRepository(cfg.PromptDir)
 	}
 
-	profiles := builtin.NewRepositoryWithDirectory(cfg.ProfileDir)
+	profiles := newProfileRepository(cfg.ProfileDir, options)
-	if options.profileSource {
-		profiles = builtin.NewRepositoryWithPrimary(options.profiles)
-	}
-	if options.memorySource {
-		profiles = profile.NewOverlayRepository(options.memoryProfiles, profiles)
-	}
 
 	backendRegistry, err := backend.NewRegistry(options.backends)
 	if err != nil {
@@ -409,6 +440,26 @@ func NewEngine(cfg Config, opts ...Option) (*Engine, error) {
 	}, nil
 }
 
+func newProfileRepository(profileDir string, options engineOptions) profile.Repository {
+	repository := builtin.NewRepository()
+
+	if options.fallbackProfileSource {
+		repository = profile.NewOverlayRepository(options.fallbackProfiles, repository)
+	}
+
+	if options.profileSource {
+		repository = profile.NewOverlayRepository(options.profiles, repository)
+	} else if strings.TrimSpace(profileDir) != "" {
+		repository = profile.NewOverlayRepository(profile.NewFilesystemRepository(profileDir), repository)
+	}
+
+	if options.memorySource {
+		repository = profile.NewOverlayRepository(options.memoryProfiles, repository)
+	}
+
+	return repository
+}
+
 func fileSource(name string) (fs.FS, string, error) {
 	cleanName := strings.TrimSpace(name)
 	if cleanName == "" {
@@ -481,10 +532,10 @@ func (e *Engine) InspectPrompt(
 //
 // InspectProfile trims surrounding whitespace from profileID and looks up the
 // resulting nonblank ID exactly and case-sensitively through the engine's
-// ordinary in-memory, configured-source, and built-in profile precedence. It
+// in-memory, ordinary configured-source, application fallback, and built-in
-// applies framework defaults, the selected backend, and then the selected
+// profile precedence. It applies the framework timeout baseline, selected
-// profile to EffectiveModelParams without a request override. BackendID is
+// backend, and then selected profile to EffectiveModelParams without a request
-// empty for an endpoint-only profile.
+// override. BackendID is empty for an endpoint-only profile.
 //
 // APIKeyEnv in the returned target is an environment-variable name, never its
 // value. APIKeyRequired instead reports a direct credential requirement and is

engine_test.go

@@ -360,14 +360,14 @@ func TestEngineExecutionSettingPrecedence(t *testing.T) {
 		wantPresence promptkit.ExecutionTargetPresence
 	}{
 		{
-			name:    "framework defaults fill zero-valued profile settings",
+			name:    "unspecified provider controls retain framework timeout",
 			profile: defaultsProfile,
 			want: promptkit.ExecutionTarget{
 				Endpoint:        defaultsProfile.endpoint,
 				Model:           defaultsProfile.model,
 				Temperature:     0,
 				MaxTokens:       0,
-				TopP:            1,
+				TopP:            0,
 				TimeoutSeconds:  600,
 				ServiceTier:     defaultsProfile.serviceTier,
 				ReasoningEffort: defaultsProfile.reasoningEffort,
@@ -2301,6 +2301,8 @@ func TestSourceOptionsRejectInvalidInputs(t *testing.T) {
 		{name: "profile fs nil", opt: promptkit.WithProfileFS(nil, "profiles")},
 		{name: "profile fs empty root", opt: promptkit.WithProfileFS(fstest.MapFS{}, "")},
 		{name: "profile file empty", opt: promptkit.WithProfileFile("")},
+		{name: "fallback profile fs nil", opt: promptkit.WithFallbackProfileFS(nil, "profiles")},
+		{name: "fallback profile fs empty root", opt: promptkit.WithFallbackProfileFS(fstest.MapFS{}, "")},
 		{name: "schema fs nil", opt: promptkit.WithSchemaFS(nil, "schemas")},
 		{name: "schema fs empty root", opt: promptkit.WithSchemaFS(fstest.MapFS{}, "")},
 		{name: "schema file empty", opt: promptkit.WithSchemaFile("")},

internal/defaults/defaults.go

@@ -14,9 +14,6 @@ const (
 	ContentTypeApplicationJSON = "application/json"
 	OpenAIChatCompletionsPath  = "/chat/completions"
 
-	ExecutionDefaultTemperature    = 0.0
-	ExecutionDefaultMaxTokens      = 0
-	ExecutionDefaultTopP           = 1.0
 	ExecutionDefaultTimeoutSeconds = 600
 )
 
@@ -26,9 +23,6 @@ var (
 
 func ExecutionTargetDefault() domain.ExecutionTarget {
 	return domain.ExecutionTarget{
-		Temperature:    ExecutionDefaultTemperature,
-		MaxTokens:      ExecutionDefaultMaxTokens,
-		TopP:           ExecutionDefaultTopP,
 		TimeoutSeconds: ExecutionDefaultTimeoutSeconds,
 	}
 }

internal/profile/builtin/repository.go

@@ -2,7 +2,6 @@ package builtin
 
 import (
 	"embed"
-	"strings"
 
 	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
 )
@@ -15,17 +14,3 @@ 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

@@ -2,14 +2,11 @@ package builtin
 
 import (
 	"context"
-	"errors"
 	"io/fs"
 	"strings"
 	"testing"
 
 	"gitea.maximumdirect.net/eric/promptkit/internal/backend"
-	"gitea.maximumdirect.net/eric/promptkit/internal/domain"
-	"gitea.maximumdirect.net/eric/promptkit/internal/profile"
 	"gopkg.in/yaml.v3"
 )
 
@@ -91,53 +88,3 @@ func loadBuiltInProfileIDs(t *testing.T) map[string]string {
 	}
 	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/usecase/runner_test.go

@@ -1690,36 +1690,6 @@ func TestRunnerRunSelectedProfileBeatsBuiltInDefault(t *testing.T) {
 	}
 }
 
-func TestRunnerRunBuiltInDefaultsUsedWhenProfileOmitsOptionalFields(t *testing.T) {
-	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}
-	execRepo := &fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{
-		"exec": {ID: "exec", Endpoint: "http://profile/v1", Model: "profile-model"},
-	}}
-	llmClient := &fakeLLM{resp: &domain.GenerateResponse{Content: "ok"}}
-	runner := NewRunner(promptRepo, execRepo, nil, defaultArtifactReader(), defaultRenderer(), llmClient, nil, nil)
-
-	res, err := runner.Run(context.Background(), domain.RunRequest{
-		PromptID:  "p",
-		ProfileID: "exec",
-		Inputs:    singleInputRef(),
-	})
-	if err != nil {
-		t.Fatalf("expected no error, got %v", err)
-	}
-	if res.EffectiveModelParams.Temperature != defaults.ExecutionDefaultTemperature {
-		t.Fatalf("expected default temperature %v, got %v", defaults.ExecutionDefaultTemperature, res.EffectiveModelParams.Temperature)
-	}
-	if res.EffectiveModelParams.TopP != defaults.ExecutionDefaultTopP {
-		t.Fatalf("expected default top_p %v, got %v", defaults.ExecutionDefaultTopP, res.EffectiveModelParams.TopP)
-	}
-	if res.EffectiveModelParams.MaxTokens != defaults.ExecutionDefaultMaxTokens {
-		t.Fatalf("expected default max_tokens %d, got %d", defaults.ExecutionDefaultMaxTokens, res.EffectiveModelParams.MaxTokens)
-	}
-	if res.EffectiveModelParams.TimeoutSeconds != defaults.ExecutionDefaultTimeoutSeconds {
-		t.Fatalf("expected default timeout_seconds %d, got %d", defaults.ExecutionDefaultTimeoutSeconds, res.EffectiveModelParams.TimeoutSeconds)
-	}
-}
-
 func TestRunnerRunAPIKeyEnvResolvesFromEnvironment(t *testing.T) {
 	t.Setenv("PROMPTKIT_TEST_API_KEY", "secret")
 	promptRepo := &fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)}

public_contract_test.go

@@ -973,6 +973,24 @@ func TestRepeatedOptionsUseLastValueInEachCategory(t *testing.T) {
 		}
 	})
 
+	t.Run("fallback profile source", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", "profile", "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS("profile", "first-model"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS("profile", "second-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+		if err != nil {
+			t.Fatalf("prepare from last fallback profile source: %v", err)
+		}
+		if prepared.EffectiveModelParams.Model != "second-model" {
+			t.Fatalf("expected last fallback profile source, got %q", prepared.EffectiveModelParams.Model)
+		}
+	})
+
 	t.Run("in-memory profiles", func(t *testing.T) {
 		first := profile
 		first.Model = "first-model"
@@ -1057,6 +1075,212 @@ func TestRepeatedOptionsUseLastValueInEachCategory(t *testing.T) {
 	})
 }
 
+func TestFallbackProfileSourcePrecedence(t *testing.T) {
+	const profileID = "application-profile"
+
+	prepareModel := func(t *testing.T, engine *promptkit.Engine, promptID string) string {
+		t.Helper()
+		prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: promptID})
+		if err != nil {
+			t.Fatalf("prepare: %v", err)
+		}
+		return prepared.EffectiveModelParams.Model
+	}
+
+	t.Run("in-memory profiles override ordinary and fallback profiles", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+			promptkit.WithProfileFS(contractProfileFS(profileID, "ordinary-model"), "."),
+			promptkit.WithProfiles(promptkit.Profile{ID: profileID, Endpoint: "http://example.test/v1", Model: "memory-model"}),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if model := prepareModel(t, engine, "prompt"); model != "memory-model" {
+			t.Fatalf("expected in-memory profile, got %q", model)
+		}
+	})
+
+	t.Run("ordinary filesystem source overrides fallback profile", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+			promptkit.WithProfileFS(contractProfileFS(profileID, "ordinary-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if model := prepareModel(t, engine, "prompt"); model != "ordinary-model" {
+			t.Fatalf("expected ordinary profile, got %q", model)
+		}
+	})
+
+	t.Run("configured directory overrides fallback profile", func(t *testing.T) {
+		profileDir := t.TempDir()
+		writePublicProfileFile(t, profileDir, profileID, "http://example.test/v1", "directory-model")
+		engine, err := promptkit.NewEngine(promptkit.Config{ProfileDir: profileDir},
+			promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if model := prepareModel(t, engine, "prompt"); model != "directory-model" {
+			t.Fatalf("expected configured directory profile, got %q", model)
+		}
+	})
+
+	t.Run("fallback profile overrides built-in profile", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", "mistral-small-3", "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS("mistral-small-3", "fallback-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if model := prepareModel(t, engine, "prompt"); model != "fallback-model" {
+			t.Fatalf("expected fallback profile, got %q", model)
+		}
+	})
+
+	t.Run("missing fallback profile uses built-in profile", func(t *testing.T) {
+		t.Setenv("OPENROUTER_API_KEY", "test-key")
+		baseline, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", "mistral-small-3", "message"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct baseline engine: %v", err)
+		}
+		want := prepareModel(t, baseline, "prompt")
+
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", "mistral-small-3", "message"), "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if model := prepareModel(t, engine, "prompt"); model != want {
+			t.Fatalf("expected built-in profile model %q, got %q", want, model)
+		}
+	})
+}
+
+func TestFallbackProfileSourcePreservesLazyLoadingAndErrors(t *testing.T) {
+	const profileID = "application-profile"
+
+	t.Run("construction defers malformed fallback profiles", func(t *testing.T) {
+		_, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(fstest.MapFS{}, "."),
+			promptkit.WithFallbackProfileFS(fstest.MapFS{
+				"broken.yaml": &fstest.MapFile{Data: []byte("id: broken\nunknown: value\n")},
+			}, "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine with malformed fallback profile: %v", err)
+		}
+	})
+
+	t.Run("unrelated malformed fallback profile does not block matching definition", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+			promptkit.WithFallbackProfileFS(fstest.MapFS{
+				"broken.yaml": &fstest.MapFile{Data: []byte("id: unrelated\nunknown: value\n")},
+				"valid.yaml":  &fstest.MapFile{Data: []byte("id: application-profile\nendpoint: http://example.test/v1\nmodel: fallback-model\n")},
+			}, "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+		if err != nil {
+			t.Fatalf("prepare from valid fallback profile: %v", err)
+		}
+		if prepared.EffectiveModelParams.Model != "fallback-model" {
+			t.Fatalf("unexpected fallback profile model: %q", prepared.EffectiveModelParams.Model)
+		}
+	})
+
+	t.Run("matching malformed fallback profile does not reach built-in profile", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", "mistral-small-3", "message"), "."),
+			promptkit.WithFallbackProfileFS(fstest.MapFS{
+				"mistral-small-3.yaml": &fstest.MapFile{Data: []byte("id: mistral-small-3\nendpoint: http://example.test/v1\nmodel: fallback-model\nunknown: value\n")},
+			}, "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if _, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt"}); !errors.Is(err, promptkit.ErrProfileLoad) {
+			t.Fatalf("expected ErrProfileLoad, got %v", err)
+		}
+	})
+
+	t.Run("matching malformed ordinary profile does not reach fallback profile", func(t *testing.T) {
+		engine, err := promptkit.NewEngine(promptkit.Config{},
+			promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+			promptkit.WithProfileFS(fstest.MapFS{
+				"application-profile.yaml": &fstest.MapFile{Data: []byte("id: application-profile\nendpoint: http://example.test/v1\nmodel: ordinary-model\nunknown: value\n")},
+			}, "."),
+			promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+		)
+		if err != nil {
+			t.Fatalf("construct engine: %v", err)
+		}
+		if _, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt"}); !errors.Is(err, promptkit.ErrProfileLoad) {
+			t.Fatalf("expected ErrProfileLoad, got %v", err)
+		}
+	})
+}
+
+func TestFallbackProfileSourceWorksAcrossWorkflows(t *testing.T) {
+	const profileID = "application-profile"
+	client := &fakeLLMClient{response: &promptkit.GenerateResponse{Content: "ok"}}
+	engine, err := promptkit.NewEngine(promptkit.Config{},
+		promptkit.WithPromptFS(contractPromptFS("prompt", profileID, "message"), "."),
+		promptkit.WithFallbackProfileFS(contractProfileFS(profileID, "fallback-model"), "."),
+		promptkit.WithLLMClient(client),
+	)
+	if err != nil {
+		t.Fatalf("construct engine: %v", err)
+	}
+
+	inspection, err := engine.InspectProfile(context.Background(), profileID)
+	if err != nil {
+		t.Fatalf("inspect fallback profile: %v", err)
+	}
+	prepared, err := engine.Prepare(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+	if err != nil {
+		t.Fatalf("prepare fallback profile: %v", err)
+	}
+	preparedExecution, err := engine.PrepareExecution(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+	if err != nil {
+		t.Fatalf("prepare execution with fallback profile: %v", err)
+	}
+	preparedDetails := preparedExecution.Details()
+	preparedResult, err := engine.RunPrepared(context.Background(), preparedExecution)
+	if err != nil {
+		t.Fatalf("run prepared fallback profile: %v", err)
+	}
+	runResult, err := engine.Run(context.Background(), promptkit.RunRequest{PromptID: "prompt"})
+	if err != nil {
+		t.Fatalf("run fallback profile: %v", err)
+	}
+
+	for name, model := range map[string]string{
+		"inspection":         inspection.EffectiveModelParams.Model,
+		"preparation":        prepared.EffectiveModelParams.Model,
+		"prepared execution": preparedDetails.EffectiveModelParams.Model,
+		"prepared result":    preparedResult.EffectiveModelParams.Model,
+		"run result":         runResult.EffectiveModelParams.Model,
+	} {
+		if model != "fallback-model" {
+			t.Fatalf("%s model=%q, want fallback-model", name, model)
+		}
+	}
+}
+
 func TestEngineSupportsConcurrentPrepareAndRun(t *testing.T) {
 	engine, err := promptkit.NewEngine(promptkit.Config{},
 		promptkit.WithPromptFS(contractPromptFS("prompt", "profile", "message"), "."),

types.go

@@ -116,7 +116,8 @@ type RunRequest struct {
 	// empty maps are equivalent.
 	Vars map[string]string
 	// Execution optionally overrides individual execution settings. Nil uses
-	// the selected profile over its backend, when any, and framework defaults.
+	// the selected profile over its backend, when any, and the framework
+	// baseline.
 	Execution *ExecutionTargetOverride
 	// Validation optionally replaces the prompt's complete output contract. It
 	// does not merge individual fields. Nil uses the prompt contract.
@@ -144,9 +145,10 @@ type PreparedRun struct {
 	// SelectedBackendID equals EffectiveModelParams.BackendID. It is empty for
 	// an endpoint-only profile.
 	SelectedBackendID string `json:"selected_backend_id,omitempty"`
-	// EffectiveModelParams contains framework defaults overlaid by the selected
+	// EffectiveModelParams contains settings resolved from the framework timeout
-	// backend, profile, and then request overrides. It excludes resolved API-key
+	// baseline, selected backend, profile, and then request overrides. Unset
-	// values.
+	// optional provider controls remain zero rather than reporting a provider
+	// default. It excludes resolved API-key values.
 	EffectiveModelParams ExecutionTarget `json:"effective_model_params"`
 	// OutputContract is the complete effective output contract.
 	OutputContract OutputContract `json:"output_contract"`
@@ -298,13 +300,17 @@ type ExecutionTarget struct {
 	Endpoint string `json:"endpoint"`
 	// Model is the provider model identifier.
 	Model string `json:"model"`
-	// Temperature is the effective sampling temperature from 0 through 2.
+	// Temperature is the resolved sampling temperature from 0 through 2. Zero
+	// leaves the field unspecified to compatible providers unless the
+	// corresponding ExecutionTargetPresence bit is true.
 	Temperature float64 `json:"temperature"`
-	// MaxTokens is the non-negative effective output-token limit. Zero leaves
+	// MaxTokens is the non-negative resolved output-token limit. Zero leaves
-	// the limit unspecified to compatible providers unless it was an explicit
+	// the limit unspecified to compatible providers unless the corresponding
-	// request override.
+	// ExecutionTargetPresence bit is true.
 	MaxTokens int `json:"max_tokens"`
-	// TopP is the effective nucleus-sampling value from 0 through 1.
+	// TopP is the resolved nucleus-sampling value from 0 through 1. Zero leaves
+	// the field unspecified to compatible providers unless the corresponding
+	// ExecutionTargetPresence bit is true.
 	TopP float64 `json:"top_p"`
 	// TimeoutSeconds is the non-negative per-generation deadline. Zero disables
 	// this deadline without disabling caller cancellation or the transport cap.
@@ -329,9 +335,11 @@ type ExecutionTarget struct {
 type ProfileInspection struct {
 	// ProfileID is the trimmed, exact profile ID inspected by the engine.
 	ProfileID string
-	// EffectiveModelParams contains framework defaults overlaid by the selected
+	// EffectiveModelParams contains settings resolved from the framework timeout
-	// backend and then the profile, without a request override. APIKeyEnv is an
+	// baseline, selected backend, and then profile, without a request override.
-	// environment-variable name, never its credential value.
+	// Unset optional provider controls remain zero rather than reporting a
+	// provider default. APIKeyEnv is an environment-variable name, never its
+	// credential value.
 	EffectiveModelParams ExecutionTarget
 	// APIKeyRequired reports that a later execution must supply a direct API
 	// key or an explicit request environment override. It is mutually exclusive
@@ -382,19 +390,26 @@ type PromptInspection struct {
 // fields replace profile values and preserve explicit zero or empty values. A
 // non-empty ExtraParams map replaces the complete profile or backend map
 // rather than merging keys. Empty string fields, nil pointers, and a nil or
-// empty ExtraParams map inherit the selected profile over its backend, when
+// empty ExtraParams map inherit lower-precedence values. An optional provider
-// any, and framework defaults.
+// control that remains zero is unspecified; TimeoutSeconds retains its
+// framework deadline when no higher-precedence value is present.
 type ExecutionTargetOverride struct {
 	// Endpoint replaces the profile or backend endpoint when non-empty without
 	// changing the effective BackendID.
 	Endpoint string
 	// Model replaces the profile model when non-empty.
 	Model string
-	// Temperature, when non-nil, must point to a value from 0 through 2.
+	// Temperature, when non-nil, must point to a value from 0 through 2. A
+	// pointed-to zero is explicitly present; nil inherits a lower-precedence
+	// value and otherwise leaves the provider control unspecified.
 	Temperature *float64
-	// MaxTokens, when non-nil, must point to a non-negative value.
+	// MaxTokens, when non-nil, must point to a non-negative value. A pointed-to
+	// zero is explicitly present; nil inherits a lower-precedence value and
+	// otherwise leaves the provider control unspecified.
 	MaxTokens *int
-	// TopP, when non-nil, must point to a value from 0 through 1.
+	// TopP, when non-nil, must point to a value from 0 through 1. A pointed-to
+	// zero is explicitly present; nil inherits a lower-precedence value and
+	// otherwise leaves the provider control unspecified.
 	TopP *float64
 	// TimeoutSeconds, when non-nil, must point to a non-negative value. A
 	// pointed-to zero disables the per-generation deadline.
@@ -425,9 +440,12 @@ type ExecutionTargetOverride struct {
 // use profile YAML api_key_env with file and FS profile sources. Profile has no
 // stable JSON representation.
 //
-// WithProfiles validates and copies Profile values during NewEngine. Numeric
+// WithProfiles validates and copies Profile values during NewEngine. Zero
-// zero, blank strings, and an empty ExtraParams map inherit framework defaults;
+// Temperature, MaxTokens, and TopP values and blank ServiceTier and
-// use ExecutionTargetOverride pointer fields to request explicit numeric zero.
+// ReasoningEffort values leave those provider controls unspecified. A zero
+// TimeoutSeconds retains the framework deadline, while an empty ExtraParams map
+// inherits backend request defaults. Use ExecutionTargetOverride pointer fields
+// to request an explicit numeric zero.
 type Profile struct {
 	// ID is the required non-blank profile identifier. WithProfiles trims it.
 	ID string
@@ -441,19 +459,19 @@ type Profile struct {
 	Endpoint string
 	// Model is the required non-blank provider model identifier.
 	Model string
-	// Temperature is from 0 through 2. Zero inherits the framework default.
+	// Temperature is from 0 through 2. Zero leaves the provider control
+	// unspecified.
 	Temperature float64
-	// MaxTokens is non-negative. Zero inherits the framework default.
+	// MaxTokens is non-negative. Zero leaves the provider control unspecified.
 	MaxTokens int
-	// TopP is from 0 through 1. Zero inherits the framework default rather than
+	// TopP is from 0 through 1. Zero leaves the provider control unspecified
-	// selecting an explicit zero.
+	// rather than selecting an explicit zero.
 	TopP float64
-	// TimeoutSeconds is non-negative. Zero inherits the framework default.
+	// TimeoutSeconds is non-negative. Zero retains the framework deadline.
 	TimeoutSeconds int
-	// ServiceTier is optional; a blank value inherits the framework default.
+	// ServiceTier is optional; a blank value leaves it unspecified.
 	ServiceTier string
-	// ReasoningEffort is optional; a blank value inherits the framework
+	// ReasoningEffort is optional; a blank value leaves it unspecified.
-	// default.
 	ReasoningEffort string
 	// APIKeyRequired clears a backend's inherited API-key environment name and
 	// requires a non-blank RunRequest.APIKey unless the request explicitly