promptkit/audit.md

# Codebase Audit

## Sequence Prerequisite

Stage 0 had not been executed when this artifact was created: the repository
contained no `audit.md` at the start of the Stage 1 review. Consequently, the
reproducible repository baseline, package inventory, validation matrix, graph
refresh, and initial coverage ledger required by Stage 0 remain outstanding.
This review did not backfill that out-of-scope work.

The Stage 1 review began from commit
`ebf1602635e108e2a7ac1abd3a3ca24a620104ce` on branch `main`, with a clean
working tree and Go `go1.26.5 linux/amd64`. These details identify this review
only; they are not a substitute for the Stage 0 baseline.

## Stage 1: Public Values, Conversion, Errors, And Formatting

### Scope Reviewed

The review covered `doc.go`, `types.go`, `convert.go`, `errors.go`,
`capacity_error.go`, `formatting.go`, and `prepared_execution.go`, plus the
directly relevant root tests. Internal domain declarations and callers were
consulted only to confirm field-complete conversion, ownership, and public
error mapping. Engine assembly, runtime orchestration, adapter implementation,
and JSON codec mechanics were not audited.

### Accepted Findings

#### S01-F01: Run-request formatting tests do not protect input and variable redaction

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `formatting.go` (`RunRequest.String`,
  `RunRequest.GoString`, and `RunRequest.redactedString`) and `engine_test.go`
  (`TestRunRequestFormattingRedactsDirectAPIKey`)
- **Contract at issue:** The formatter GoDoc promises that `String` and
  `GoString` omit direct credentials and input and variable contents. The
  documentation and testing policies treat prompt inputs and other private
  content as sensitive and give consequential disclosure behavior a strong
  presumption of durable test protection.
- **Evidence:** The implementation currently satisfies the contract by
  formatting only request identifiers, collection lengths, presence flags,
  and whether an API key is set. The focused test supplies an inline input but
  asserts only that the API-key sentinel is absent and `APIKeySet:true` is
  present; it supplies no variable values and never checks whether the input
  URI, input body, or variable values appear. The test would remain green if a
  later formatter change appended input or variable contents while continuing
  to omit the API key.
- **Failure mode:** A logging or diagnostic-formatting refactor could disclose
  prompt input or template-variable content through ordinary `%v`, `%+v`, or
  `%#v` formatting without a contract-test failure.
- **Recommended direction:** Extend the existing formatting test, rather than
  adding a parallel test, with distinct input URI, input body, and variable
  sentinels and assert that each is absent from all three supported formatting
  forms. Retain the positive structural assertions so the test continues to
  distinguish a useful summary from an empty formatter.
- **Required verification:** Run the focused request-formatting test and the
  root package tests. Confirm that a deliberate formatter mutation exposing
  any sentinel makes the focused test fail.

### Unresolved Observations

None. Medium- or low-confidence concerns discovered during this review were
not promoted to findings.

### Coverage Ledger

- **Public value declarations and zero values:** Reviewed request, prepared,
  result, artifact, inspection, target, output, validation, rendered-prompt,
  structured-output, generation, and token-usage values. Nil maps, slices,
  pointers, optional values, and zero-value public enum strings cross the
  facade without panics or invented values.
- **Request conversion:** `toDomainRunRequest` and its helpers preserve every
  public field, copy maps and pointer values, validate and deeply copy nested
  JSON-compatible overrides, and retain direct credentials only in the
  internal request field intended for execution.
- **Prepared and result conversion:** `fromDomainPreparedRun`,
  `fromDomainRunResult`, and their helpers preserve all public fields while
  copying artifact bytes, validation diagnostics, hashes, rendered messages,
  cache-control pointers, effective extra parameters, and structured-output
  schemas. Internal credential and target-presence fields do not escape.
- **Inspection and extension conversion:** Profile and prompt inspection
  outputs are independent copies. Generation requests receive copied prompt,
  target, presence, and structured-output values; generation responses contain
  no mutable fields requiring additional copying.
- **Copy-rule ownership:** Caller-supplied JSON-compatible values enter through
  `internal/jsonvalue` validation and copying. The outward conversion helpers
  copy already-validated domain snapshots without introducing a second
  acceptance policy. No consolidation finding was warranted in this scope.
- **Public errors:** Not-found identities remain distinct from load failures;
  profile-required and missing-credential errors retain their more specific
  identity together with `ErrInvalidRequest`; collaborator and cancellation
  identities remain discoverable; and typed capacity errors expose only a
  copied backend ID plus `ErrCapacityExceeded` rather than the internal error
  type. Nil and zero `CapacityError` values are safe.
- **Diagnostic formatting:** `RunRequest` and `GenerateRequest` currently omit
  direct credentials and content from `String`, `GoString`, `%+v`, and `%#v`.
  `PreparedExecution` always formats as an opaque constant, including through
  a copied handle. Prepared and result values intentionally expose rendered or
  generated content as documented in package GoDoc; applications retain
  responsibility for logging those content-bearing values.
- **Prepared handle values:** Nil and zero handles return zero details and may
  be discarded safely. Details are fresh deep copies and remain stable after
  execution or discard. Copying a handle shares its single-use lifecycle
  without exposing the internal representation.
- **Test ownership:** Root external-package tests appropriately own public
  snapshots, structured error identity, and opaque-handle behavior. Focused
  internal error-mapping tests cover internal-type containment. The one
  material redaction gap is recorded as S01-F01.

### Verification Performed

The code knowledge graph was used to discover the scoped symbols, trace their
callers and callees through the facade and internal domain boundary, and locate
the focused tests. Important conclusions were confirmed against source.

The following focused commands passed:

```sh
go test . -run 'Test(PreparedRunJSONDoesNotExposeSecretOrTargetPresence|RunRequestFormattingRedactsDirectAPIKey|GenerateRequestFormattingRedactsDirectAPIKey|MapPublicErrorPreservesGenerationCancellation|MapPublicErrorTranslatesCapacityError|CapacityExceededSentinelContract|InspectProfileReturnsIndependentTargetMatchingPreparation|InspectPromptReturnsIndependentMetadataMatchingPreparation|PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|PreparedExecutionLifecycleAndEngineBinding|PreparedExecutionDiscardAndFormattingDoNotExposePrivateState|InMemoryProfileExtraParamsAreCopiedAcrossPublicBoundary|ExtraParamsTypedNestedValuesAreCopiedAcrossPublicBoundary|ArtifactReaderReceivesPublicReferenceAndPreparesArtifact|RunPassesPreparedRequestToInjectedLLMClient|PublicErrorsSupportErrorsIs)$'
go test -race . -run 'Test(PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|PreparedExecutionConcurrentClaimAllowsOneGeneration|PreparedExecutionRunAndDiscardRaceHasOneWinner|PreparedExecutionDiscardAndFormattingDoNotExposePrivateState|MapPublicErrorTranslatesCapacityError|RunRequestFormattingRedactsDirectAPIKey|GenerateRequestFormattingRedactsDirectAPIKey)$' -count=3
```

### Handoff

- Execute the missing Stage 0 baseline before relying on this file as a
  complete audit ledger or beginning the next component review.
- Stage 2 owns public configuration helpers, `json.go`, extension-adapter
  implementation, and adapter-specific mutation and cancellation behavior.
- Stages 3 and 4 own engine construction and runtime operations respectively;
  this review did not evaluate those paths beyond tracing their use of the
  scoped conversion and error boundary.

## Stage 2: Public Configuration And Extension Adapters

### Scope Reviewed

The review covered `backends.go`, `profiles.go`, `artifact_reader.go`,
`json.go`, and `llm_adapter.go`, together with directly relevant root tests,
external-package contract tests, and `internal/profile` validation tests.
Internal backend, profile, artifact, and LLM declarations were consulted only
to compare boundary contracts and policy ownership. `NewEngine` option
assembly, source composition, runtime orchestration, internal profile-source
behavior, and transport mechanics were not audited.

### Accepted Findings

#### S02-F01: Out-of-range JSON durations silently overflow during decoding

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `json.go` (`RunResult.UnmarshalJSON` and
  `runResultJSON.DurationMS`) and `public_contract_test.go`
  (`TestRunResultJSONUsesMillisecondsAndRoundTrips`)
- **Contract at issue:** `RunResult` has a stable JSON representation in which
  `duration_ms` is an integer millisecond count. Decoding must not silently
  turn an accepted wire value into unrelated duration metadata.
- **Evidence:** The wire field accepts the full `int64` range, then decoding
  multiplies that value by `time.Millisecond` without checking whether the
  nanosecond-valued `time.Duration` can represent the result. A focused probe
  decoded `{"duration_ms":9223372036854775807}` with a nil error and produced
  `Duration == -1ms`. The existing round-trip test exercises only `1500ms` and
  does not cover either representable boundaries or overflow.
- **Failure mode:** Malformed or untrusted persisted JSON can be accepted while
  corrupting a very large positive duration into a negative or otherwise
  wrapped value. Downstream timing displays, comparisons, or metrics then
  consume false data without a decode error.
- **Recommended direction:** Validate the millisecond value against the range
  that can be safely converted to `time.Duration` before multiplication and
  return a contextual JSON decoding error for values outside that range.
- **Required verification:** Add boundary cases for the largest safely
  representable positive and negative millisecond values and their first
  out-of-range neighbors, plus the reproduced maximum-`int64` input. Retain
  ordinary and zero-value round-trip coverage.

#### S02-F02: In-memory and filesystem profiles duplicate semantic validation

- **Category:** duplication
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `profiles.go` (`validatePublicProfile`,
  `toDomainProfile`, and the memory profile repository) and
  `internal/profile/filesystem_repository.go` (`validateProfile` and
  `loadProfile`), plus their focused tests
- **Contract at issue:** Profiles supplied in memory and profiles loaded from a
  filesystem are two sources for the same execution-profile domain value.
  Required identity, backend-or-endpoint selection, model presence, and
  numeric bounds are one semantic acceptance policy and need one owner.
- **Evidence:** `validatePublicProfile` and `validateProfile` independently
  implement the same seven conditions with the same error text: required ID,
  backend or endpoint, required model, temperature in `[0,2]`, non-negative
  maximum tokens, top-p in `[0,1]`, and non-negative timeout. The root tests do
  not exercise the required-field or scalar-bound cases for in-memory
  profiles, and the filesystem tests do not protect all scalar bounds. This is
  policy duplication rather than mere translation or error wrapping.
- **Failure mode:** A future constraint or correction can be applied to one
  profile source but not the other, making an otherwise identical profile
  valid or invalid according to where it was stored. Sparse boundary tests
  would not reliably expose the divergence.
- **Recommended direction:** Give the domain-level profile acceptance rule one
  internal owner that both in-memory and filesystem repositories invoke,
  while leaving source-specific normalization and public error translation at
  their existing boundaries.
- **Required verification:** Protect the shared validator with a table covering
  every required field and both sides of every numeric bound, then retain a
  small integration check for each source and for the public
  `ErrInvalidConfig` translation.

#### S02-F03: The injected LLM client's mutation-ownership contract is untested

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `llm_adapter.go` (`publicLLMClientAdapter.Generate`),
  `convert.go` (`fromDomainGenerateRequest` and its nested conversions),
  `types.go` (`LLMClient`), and injected-client tests in `engine_test.go`
- **Contract at issue:** The public `LLMClient` contract explicitly states that
  maps, slices, and pointers in `GenerateRequest` are client-owned copies that
  may be mutated or retained. The adapter is the boundary responsible for
  satisfying that ownership promise.
- **Evidence:** The adapter currently constructs independent messages,
  cache-control pointers, target parameters, and structured-output schema
  values before invoking the client. Existing fakes retain requests and tests
  inspect field propagation, errors, and cancellation, but no test mutates the
  nested request received by the client and proves that the source domain
  request remains unchanged. A shallow-copy regression would therefore
  preserve all current field-equality assertions.
- **Failure mode:** A conforming injected client could mutate or asynchronously
  retain nested request data and thereby alter prepared engine state, affect a
  later operation, or introduce a race despite following the documented
  interface contract.
- **Recommended direction:** Add a focused adapter-boundary ownership test that
  has a client mutate and retain each mutable nested shape, then verifies that
  the domain request and its nested values remain unchanged. Keep engine-level
  tests focused on observable request propagation and error identity.
- **Required verification:** Exercise prompt messages and cache control, target
  extra parameters, and structured-output schema under the focused test; run
  it with the race detector as well as normally.

#### S02-F04: The profile convenience constructor's full mapping is unprotected

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `profiles.go` (`OpenAICompatibleProfile` and
  `OpenAICompatibleProfileConfig`) and the three
  `TestOpenAICompatibleProfile...` tests in `engine_test.go`
- **Contract at issue:** The exported convenience constructor promises a
  `Profile` suitable for the general `WithProfiles` path. Its consumer-visible
  behavior is the complete, field-for-field mapping of configuration values,
  followed by the documented deferred validation and copying rules.
- **Evidence:** The implementation currently maps every configuration field.
  The principal integration test asserts backend ID, model, direct API-key
  behavior, and extra parameters, while the other tests cover deferred nested
  parameter validation and ownership. No test protects endpoint,
  temperature, maximum tokens, top-p, timeout, service tier, or reasoning
  effort as constructor output. Dropping any of those assignments would leave
  the current constructor-specific tests green.
- **Failure mode:** A maintenance edit can silently discard a supported model
  setting from the convenience path while the equivalent general `Profile`
  configuration continues to work, creating source-dependent behavior for
  consumers.
- **Recommended direction:** Add one direct, table-like all-field mapping test
  for the constructor and keep only the integration assertions that establish
  its passage through ordinary profile validation and ownership boundaries.
- **Required verification:** Populate every scalar and string setting with a
  distinct non-zero value, compare the complete returned `Profile`, and retain
  the existing nested-extra-parameter and invalid-parameter integration cases.

#### S02-F05: Stable JSON field mappings have multiple manual owners

- **Category:** duplication
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `json.go` (`PreparedRun.MarshalJSON`, `runResultJSON`,
  `RunResult.MarshalJSON`, and `RunResult.UnmarshalJSON`) and JSON tests in
  `public_contract_test.go`
- **Contract at issue:** The stable public JSON shape should preserve every
  public field except for intentional timing representation and omission
  rules. The list of ordinary fields is one serialization policy, not a
  separate rule for each encoding direction.
- **Evidence:** `PreparedRun.MarshalJSON` redeclares and assigns every field in
  an anonymous wire struct. `RunResult` repeats its field list in the public
  type, `runResultJSON`, the marshal literal, and the unmarshal literal. The
  custom handling is needed only for timing fields, but ordinary fields are
  manually synchronized around it. Existing JSON tests cover timing,
  artifact content type, session ID, and backend omission but do not round-trip
  fully populated values. Adding a public field to either value can therefore
  omit it from stable JSON without a compile failure or focused test failure.
- **Failure mode:** Public Go values and their documented stable JSON form can
  drift, or marshal and unmarshal can become asymmetric, as fields evolve.
  Consumer data may be silently absent after persistence or interchange.
- **Recommended direction:** Structure the wire representation so ordinary
  fields derive from a single alias or embedded representation and only the
  timing exceptions require explicit mapping. Avoid changing existing JSON
  names or omission behavior while consolidating ownership.
- **Required verification:** Add fully populated `PreparedRun` and `RunResult`
  JSON contract cases that check required names and omissions and compare all
  fields after round trip, alongside the timing-boundary regression from
  S02-F01.

### Unresolved Observations

None. Questions belonging to engine assembly or internal component behavior
were handed to their owning stages rather than promoted from partial traces.

### Coverage Ledger

- **Backend helpers:** `LocalBackend` is a side-effect-free conventional-value
  constructor. `WithBackend` copies the queue-capacity pointer when the option
  is applied, and existing tests protect normalization, invalid and duplicate
  definitions, nested extra-parameter freezing at construction, lookup copy
  behavior, and engine isolation. Actual registry composition remains Stage 3
  scope and internal registry policy remains Stage 6 scope.
- **Profile helpers:** `OpenAICompatibleProfile` correctly performs a shallow
  top-level extra-parameter copy and defers deep validation and freezing to the
  general profile path as documented. The full-mapping test gap is S02-F04;
  the duplicated acceptance policy is S02-F02.
- **Memory profile repository:** Repository construction rejects duplicate IDs
  and invalid nested JSON-compatible values, stores domain copies, and returns
  independent profile copies. Its source-neutral validation rule lacks a
  single owner as recorded in S02-F02.
- **Artifact reader adapter:** The public and internal reader interfaces each
  contain only `Read`. The adapter passes the caller context and error identity
  through, rejects a nil successful artifact, translates references without
  policy duplication, and copies returned body bytes. Focused and integrated
  tests protect mutation isolation, nil handling, reference translation,
  cancellation identity, and collaborator error identity.
- **LLM client adapter:** The public and internal client interfaces each
  contain only `Generate`. The adapter forwards the exact context, preserves
  client error identity for the use-case boundary, rejects a nil successful
  response, and translates the scalar response without extra policy. The
  request conversion currently deep-copies mutable data; its missing mutation
  regression protection is S02-F03.
- **Adapter cancellation and errors:** Existing public tests establish caller
  cancellation identity for generation and artifact loading and preserve
  injected sentinel errors through public wrapping. No adapter adds an
  independent deadline or cancellation mechanism.
- **Stable JSON:** Intentional timestamp, millisecond-duration, zero-value,
  session, artifact, and backend-identity behavior is partly protected. The
  confirmed overflow is S02-F01 and manual mapping drift is S02-F05.
- **Filesystem, reader, and client ownership:** Reader and client values are
  stored as narrow injected interfaces and mutable values crossing their
  adapter calls are copied as described above. Filesystem option validation,
  lifetime, and composition reside in `engine.go` and are intentionally handed
  to Stage 3 rather than inferred from this stage's helper review.

### Verification Performed

The code knowledge graph was used to locate each scoped helper and adapter,
trace its callers and callees, compare public and internal interface widths,
and confirm the duplicated profile rule. Source and focused tests were then
read to verify the graph conclusions.

The following focused commands passed:

```sh
go test . -run 'Test(PublicArtifactReaderAdapterCopiesBody|RunSucceedsWithInjectedLLMClient|RunPassesPreparedRequestToInjectedLLMClient|EngineRunPropagatesCallerCancellation|WithArtifactReaderRejectsNilReader|ArtifactReaderReceivesPublicReferenceAndPreparesArtifact|ArtifactReaderFailuresPreserveArtifactLoadErrors|RunAddsLLMGenerateToCollaboratorPublicError|PublicErrorsSupportErrorsIs|OpenAICompatibleProfileRunsThroughNormalProfilePath|OpenAICompatibleProfileDefersExtraParamsValidation|OpenAICompatibleProfileNestedExtraParamsRunThroughWithProfiles|WithProfilesRejectsDuplicateIDs|WithProfilesRejectsInvalidExtraParams|WithProfilesRejectsCyclicExtraParams|LocalBackendConstructsAndRegistersConventionalBackend|WithBackendCopiesQueueCapacity|BackendRegistrationRejectsInvalidAndDuplicateDefinitions|BackendExtraParamsAreDeeplyCopiedAtConstructionAndLookup|PreparedRunJSONOmitsZeroTimingValues|BackendIdentityJSONNamesAndOmission|PreparedRunJSONTimingRoundTrips|RunResultJSONUsesMillisecondsAndRoundTrips)$'
go test ./internal/profile -run 'Test(FilesystemRepository_GetProfile|FSRepository)$'
go test -race . -run 'Test(EngineRunPropagatesCallerCancellation|ArtifactReaderFailuresPreserveArtifactLoadErrors|PublicArtifactReaderAdapterCopiesBody|OpenAICompatibleProfileNestedExtraParamsRunThroughWithProfiles)$' -count=3
```

A temporary program outside the repository decoded
`{"duration_ms":9223372036854775807}` into `RunResult`; `go run` reported
`error=<nil> duration=-1ms nanoseconds=-1000000`, confirming S02-F01. The
temporary source was removed and no probe output was added to the repository.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  component review.
- Stage 3 owns `NewEngine` option application and the actual composition,
  validation, and lifetime of configured filesystems, readers, clients,
  profiles, and backends.
- Stage 6 owns internal backend registry and built-in profile policy. Stage 8
  owns the broader filesystem profile repository review; it should use
  S02-F02 as established evidence rather than repeating the public-side audit.
- Stage 14 owns transport-specific request construction, deadlines, response
  decoding, and resource handling. This stage assessed only the public
  injection adapter.

## Stage 3: Engine Construction, Options, And Source Assembly

### Scope Reviewed

The review covered the construction and option portions of `engine.go`, the
construction effect of `WithBackend` in `backends.go`, and directly relevant
tests in `engine_test.go`, `public_contract_test.go`, and
`capacity_contract_test.go`. Narrow traces into backend registry snapshots,
capacity-manager construction, built-in client construction, repositories,
validators, and `usecase.NewRunner` were used only to confirm the values and
dependencies assembled by `NewEngine`. Runtime engine methods, repository
parsing mechanics, validation mechanics, transport behavior, and capacity
scheduling were not audited.

### Accepted Findings

#### S03-F01: Single-file source options alter valid caller paths

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `engine.go` (`fileSource`, `WithPromptFile`,
  `WithProfileFile`, and `WithSchemaFile`) and
  `TestSourceOptionsRejectInvalidInputs` plus the three single-file success
  tests in `engine_test.go`
- **Contract at issue:** Each single-file option accepts a path naming an
  existing non-directory file. Filesystem paths are exact caller values;
  leading and trailing whitespace are legal filename characters and the
  option GoDoc does not define normalization.
- **Evidence:** `fileSource` assigns `strings.TrimSpace(name)` to `cleanName`
  and performs every path operation and `os.Stat` against that altered value.
  A focused probe created an existing file named `prompt.yaml `, confirmed
  that `os.Stat` on the supplied path succeeded, and passed the same value to
  `WithPromptFile`. `NewEngine` returned `ErrInvalidConfig` because it instead
  attempted to stat `prompt.yaml` without the trailing space. All three public
  file options share this helper. Existing tests cover ordinary paths, blank
  paths, one missing path, and one directory path, but no exact-path boundary.
- **Failure mode:** A consumer cannot configure an otherwise valid prompt,
  profile, or schema file whose name begins or ends with whitespace. The error
  also reports the altered path, obscuring why the supplied existing file was
  rejected.
- **Recommended direction:** Use trimming only to enforce the chosen blank-
  input rule, then perform path decomposition, validation, error reporting,
  and filesystem access with the original caller-supplied path.
- **Required verification:** Add a compact shared regression that constructs
  engines through all three single-file options using existing paths with a
  leading or trailing whitespace character. Retain the ordinary missing-file
  and directory rejection cases.

#### S03-F02: Construction precedence tests do not isolate documented ordering rules

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `engine.go` (`Option`, `NewEngine`, and
  `newProfileRepository`) and `TestSourceOptionsRejectInvalidInputs`,
  `TestRepeatedOptionsUseLastValueInEachCategory`,
  `TestInMemoryProfilesOverrideBuiltInsAndProfileSources`, and
  `TestFallbackProfileSourcePrecedence`
- **Contract at issue:** Option order selects the last valid value within a
  category, but profile lookup has a fixed cross-category order independent of
  argument order: in-memory, ordinary configured, application fallback, then
  built-in. A file or FS ordinary-profile option replaces `Config.ProfileDir`,
  and any invalid option must fail construction even if a later option would
  replace it.
- **Evidence:** The implementation correctly stores categories separately and
  assembles the fixed profile overlay after applying options. The main
  precedence tests, however, pass fallback, ordinary, and in-memory options in
  the same low-to-high order that a generic order-based overlay would use, so
  they would remain green if argument order accidentally began controlling
  cross-category precedence. No directly relevant test gives
  `Config.ProfileDir` and an ordinary-profile option colliding IDs to protect
  the documented replacement, and invalid-option tests do not place a valid
  replacement after the invalid value. Same-category last-value behavior is
  well covered but does not protect these distinct rules.
- **Failure mode:** An assembly refactor could make mixed profile-source order
  depend on option order, allow `Config.ProfileDir` to compete with its
  replacement option, or silently discard an earlier invalid option. The
  current tests could still pass while consumers observe different selected
  profiles or construction success.
- **Recommended direction:** Extend the existing precedence coverage with a
  small set of discriminating cases rather than a combinatorial matrix: reverse
  the cross-category option order, collide `Config.ProfileDir` with its option
  replacement, and place a valid same-category option after an invalid one.
- **Required verification:** Assert the selected model for the two profile-
  source cases and `errors.Is(err, ErrInvalidConfig)` for the invalid-then-
  valid case. Keep the test at the public construction boundary and avoid
  assertions about private repository nesting.

### Unresolved Observations

None. Lower-confidence concerns about typed-nil interface values and unusual
non-regular files were not promoted because the documented Go interface and
file contracts do not establish stronger behavior.

### Coverage Ledger

- **Option application:** `NewEngine` applies non-nil options once in argument
  order and stops on the first error. Nil options compose safely in an option
  slice. Same-category prompt, ordinary profile, fallback profile, in-memory
  profile, schema, client, and reader options use last-valid-value semantics;
  backend registrations alone accumulate. The unprotected ordering edges are
  recorded as S03-F02.
- **Required and default dependencies:** A nonblank configured prompt
  directory or prompt-source option is required. Profiles always end with the
  embedded built-in repository; schema validation defaults to the documented
  directory; the artifact reader, renderer, and model client receive
  application-neutral defaults when not injected. Construction performs no
  provider request and requires no credential.
- **Prompt and schema source selection:** Prompt and schema FS or file options
  replace their corresponding `Config` directory, retain the injected `fs.FS`
  for lazy access, and validate nil filesystems and blank roots. Single-file
  exact-path handling is defective as recorded in S03-F01. Source contents
  remain lazy and their parsing and containment belong to Stages 7 and 10.
- **Profile composition:** `newProfileRepository` builds one explicit overlay
  in the documented order: built-in, application fallback, one ordinary
  configured source, then in-memory profiles. Only one ordinary source is
  installed, and an ordinary option suppresses `Config.ProfileDir`. Matching
  malformed higher-precedence definitions stop lookup rather than becoming
  failover. The implementation is clear; S03-F02 concerns discriminating test
  coverage, not current behavior.
- **Backend and capacity assembly:** All consumer backend additions enter one
  immutable registry with the built-in backend. `NewEngine` takes one capacity-
  policy snapshot, constructs a fresh manager, and wraps either the injected
  or built-in client with that same manager before passing both to the runner.
  Invalid definitions and capacity policies fail as `ErrInvalidConfig`, and
  tests protect additive registrations, deep-copy isolation, limited and
  unlimited behavior, and independence between engines. Registry rules and
  scheduler mechanics remain Stages 6 and 15 scope.
- **Caller-owned values and collaborators:** Queue-capacity pointers are copied
  when `WithBackend` is created; backend maps and in-memory profile values are
  deeply frozen during construction. Injected filesystems, readers, clients,
  and HTTP transports remain explicit collaborator references. The built-in
  LLM constructor clones the supplied `http.Client` and focused internal tests
  protect non-mutation for positive, zero, and negative timeouts.
- **Client and validator selection:** `WithLLMClient` prevents construction of
  the built-in client while retaining engine-local capacity wrapping.
  Otherwise `Config.Timeout` and a cloned `Config.HTTPClient` configure the
  built-in client. Schema options construct the matching validator, while an
  empty `SchemaDir` uses the application-neutral default. Transport and
  validation semantics remain Stages 14 and 10 scope.
- **Failure atomicity and global state:** Every error path returns before an
  `Engine` is published. Construction state is local, registry and capacity
  values are rebuilt for each engine, and there is no process-global mutable
  configuration. File-backed prompt, profile, and schema contents are read
  lazily; malformed or missing source content is classified only when an
  operation selects it.
- **Assembly clarity and cost:** Construction is a single option pass followed
  by one repository, registry, manager, client, validator, reader, renderer,
  and runner assembly. No relevant repeated I/O, parsing, or copying cost was
  found, and the category flags make replacement and default selection
  explicit without duplicating internal component policy.
- **Test ownership:** Root external-package tests appropriately protect public
  option validity, source selection, profile precedence, copy isolation,
  default-client configuration, and engine-local backend and capacity
  behavior. Focused internal tests own registry normalization, manager policy,
  and HTTP-client cloning. S03-F02 identifies the material missing distinctions
  rather than recommending duplicate internal choreography tests.

### Verification Performed

The code knowledge graph was used to find `NewEngine`, every option category,
source-assembly helpers, and directly relevant tests; trace construction into
the registry, capacity manager, repositories, validators, model client, and
runner; and confirm that later runtime mechanics were outside the reviewed
path. Important ownership and error conclusions were confirmed against source.

The following focused commands passed:

```sh
go test . -run 'Test(NewEngineRejectsMissingPromptDir|NewEngineAcceptsMissingProfileDir|SourceOptionsRejectInvalidInputs|PackageOptionsComposeFromSlice|RepeatedOptionsUseLastValueInEachCategory|FallbackProfileSourcePrecedence|FallbackProfileSourcePreservesLazyLoadingAndErrors|BackendOptionsAccumulateAndRegistrationsAreEngineLocal|BackendRegistrationRejectsInvalidAndDuplicateDefinitions|BackendExtraParamsAreDeeplyCopiedAtConstructionAndLookup|BackendCapacityIsIndependentBetweenEngines|WithLLMClientRejectsNilClient|WithArtifactReaderRejectsNilReader|PromptRepositoryReadFailureMapsToPromptLoad|SelectedProfileRepositoryReadFailureMapsToProfileLoad|PrepareWorksWithPromptFSAndRelativeContentFile|PrepareWorksWithPromptFile|PrepareWorksWithProfileFSOverBuiltIns|PrepareWorksWithProfileFileOverBuiltIns|RunStructuredOutputWorksWithSchemaFS|RunStructuredOutputWorksWithSchemaFile|EngineRunLayersTransportAndGenerationTimeouts)$'
go test ./internal/backend -run 'Test(RegistryIncludesExactOpenRouterDefinition|RegistryNormalizesUniqueAdditionsAndIsolatesMutations|NewRegistryNormalizesCapacityPolicy)$'
go test ./internal/capacity -run 'Test(NewManagerRejectsInvalidPolicies|ManagerAdmissionIsBoundedAndReleaseIsIdempotent|ManagerAdmissionHonorsContextAndUnlimitedBackends)$'
go test ./internal/llm -run 'TestNewOpenAICompatibleClientDoesNotMutateSupplied(Nonzero|Zero)TimeoutClient|TestNewOpenAICompatibleClientTreatsSuppliedNegativeTimeoutAsUnset'
go test -race . -run 'Test(BackendCapacityIsIndependentBetweenEngines|BackendOptionsAccumulateAndRegistrationsAreEngineLocal|EngineSupportsConcurrentPrepareAndRun|RepeatedOptionsUseLastValueInEachCategory)$' -count=3
```

A temporary program outside the repository created an existing
`prompt.yaml ` file and called `NewEngine` with `WithPromptFile` using that
exact path. Direct `os.Stat` returned nil, while construction returned
`ErrInvalidConfig` after reporting the trimmed `prompt.yaml` path, confirming
S03-F01. The temporary source and generated file were removed.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  component review.
- Stage 4 owns operation entry points and public runtime error/result behavior;
  construction tests were read only through the behavior needed to observe
  assembled dependencies.
- Stages 6, 7, 8, 10, 14, and 15 own backend policy, prompt sources, profile
  repositories, validators, provider transport, and capacity scheduling
  respectively. This stage established only that `NewEngine` selects and wires
  their boundaries consistently.

## Stage 4: Engine Operations And Root Contract Coverage

### Scope Reviewed

The review covered the public operation portion of `engine.go`
(`InspectPrompt`, `InspectProfile`, `Prepare`, `PrepareExecution`, `Run`, and
`RunPrepared`) and the directly relevant root tests in `engine_test.go`,
`public_contract_test.go`, `prepared_execution_contract_test.go`, and
`errors_internal_test.go`. `prepared_execution.go` and conversion helpers were
consulted only to confirm the operation boundary established in Stage 1.
Internal runner tests were consulted only to identify test ownership; runner,
transport, validation, capacity, and repository mechanics were treated as
black boxes.

### Accepted Findings

#### S04-F01: Ordinary-run cancellation identity is protected only below the public boundary

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `engine.go` (`Engine.Run`), `errors.go`
  (`mapPublicError`), `engine_test.go`
  (`TestEngineRunPropagatesCallerCancellation`),
  `errors_internal_test.go`
  (`TestMapPublicErrorPreservesGenerationCancellation`), and
  `internal/usecase/runner_test.go`
  (`TestRunnerRunCancellationPreservesGenerationCategory`)
- **Contract at issue:** `Engine.Run` passes the caller's context through the
  execution boundary and preserves the active collaborator's cancellation
  identity while adding the public operation category. Cancellation and
  injected dependency failures are consequential public behaviors that should
  be asserted through the consumer-visible boundary.
- **Evidence:** `Engine.Run` currently passes `ctx` unchanged to the runner and
  maps its returned error without dropping wrapped identities. The external-
  package cancellation test drives a real request context through the built-in
  HTTP transport but asserts only `errors.Is(err, ErrLLMGenerate)` after
  cancellation. The `context.Canceled` identity is asserted separately only
  against the unexported `mapPublicError` helper and internal runner. A search
  of the root operation tests found no other ordinary-run assertion for that
  identity. Prepared execution does assert both identities at the public
  boundary, but it exercises a different entry point.
- **Failure mode:** A facade or ordinary-run composition change could replace
  the caller context, stop wrapping the collaborator cancellation, or discard
  it during public error mapping. The internal tests and existing public test
  could all remain green while consumers lose the ability to distinguish
  caller cancellation with `errors.Is(err, context.Canceled)`.
- **Recommended direction:** Extend the existing external-package
  `TestEngineRunPropagatesCallerCancellation` assertion to require both
  `ErrLLMGenerate` and `context.Canceled`. Retain the focused internal tests
  only for the distinct internal translation and runner responsibilities they
  protect; do not add a parallel end-to-end cancellation test.
- **Required verification:** Run the focused public cancellation test normally
  and with the race detector. Confirm that deliberately removing caller-context
  propagation or cancellation wrapping at the facade boundary makes that test
  fail.

### Unresolved Observations

None. The absence of package-level operation convenience functions was
confirmed and is not a consistency defect; the reviewed public API exposes
these operations only as `Engine` methods.

### Coverage Ledger

- **Facade shape and request translation:** All six methods reject a nil or
  uninitialized engine before delegation. `Prepare`, `PrepareExecution`, and
  `Run` use the same field-complete, defensive request conversion and classify
  conversion failures as `ErrInvalidRequest`; inspections pass their scalar
  selectors with the documented prompt/profile normalization behavior.
  `RunPrepared` unwraps only the opaque handle reference. Each successful
  facade method delegates once and converts the returned domain snapshot.
- **Context propagation:** Every method passes the supplied context directly
  to its matching runner operation. Public tests protect cancellation before
  inspection source work, active ordinary generation, and prepared generation,
  and prove that a completed preparation is independent of later cancellation
  of its preparation context. The missing consumer-boundary assertion for the
  ordinary-run cancellation identity is recorded as S04-F01.
- **Inspection operations:** Prompt inspection loads declared metadata and
  referenced content without profile, artifact, schema, capacity, or provider
  work. Profile inspection resolves the effective target and credential state
  without prompt or generation work. External-package tests protect nil and
  blank inputs, not-found versus load identities, cancellation, point-in-time
  behavior, agreement with preparation, and deep ownership of returned nested
  values.
- **Preparation and ordinary execution:** `Prepare` returns a caller-owned,
  credential-redacted prepared snapshot and performs no model generation.
  `Run` returns a caller-owned result after one execution path; content
  validation failure remains a successful result, while operational failures
  return no partial result. Root tests protect representative translation,
  prepared/generated metadata agreement, injected artifact and LLM behavior,
  validation-result semantics, and the documented public error categories.
- **Prepared execution boundary:** `PrepareExecution` publishes one opaque,
  engine-bound handle whose details are independent copies of frozen
  preparation state. `RunPrepared` preserves owner binding, atomic single-use
  claim behavior, independent execution context, no-result-on-error semantics,
  collaborator identities, credential revalidation, capacity rejection, and
  execution-only timing. External-package tests also protect concurrent claim
  and run/discard behavior. The internal claim, admission, validation, and
  release mechanisms remain assigned to later component stages.
- **Public error mapping:** Every runner error is routed through one facade
  mapping point. Ordinary public identities and injected collaborator errors
  remain discoverable with `errors.Is`; capacity failures become public
  `CapacityError` values without leaking the internal type; successful paths
  do not invent errors. Internal mapping tests appropriately own internal-type
  containment, while public operation tests own consumer-visible categories
  and collaborator identities except for S04-F01.
- **Ownership:** Request conversion freezes caller maps, slices, pointers, and
  JSON-compatible values before internal use. Inspection, prepared, details,
  and result conversions return fresh mutable values. The prepared-execution
  contract tests demonstrate that later caller and source mutations do not
  change frozen execution and that mutating one returned snapshot does not
  change engine-owned state.
- **Convenience-function consistency:** The graph and source search found no
  package-level `Prepare`, `PrepareExecution`, `Run`, `RunPrepared`,
  `InspectPrompt`, or `InspectProfile` functions. There is therefore no second
  operation surface whose translation, errors, or ownership can drift from
  the methods.
- **Test ownership and duplication:** Root external-package tests protect the
  exported facade and representative assembled workflows. Focused internal
  tests own runner coordination and public-error translation mechanics. Some
  lifecycle and error categories necessarily appear at both levels, but the
  assertions address different stable boundaries; no removable semantic
  duplication was found. S04-F01 is the one important identity currently
  asserted only below the applicable public operation boundary.
- **Clarity and cost:** The operation facade is a uniform sequence of guard,
  translation where needed, one delegation, public error mapping, and outward
  conversion. No duplicated orchestration policy, repeated I/O, avoidable
  copying, or operation-layer complexity was found. Costs inside preparation,
  generation, validation, transport, and capacity remain assigned to their
  owning later stages.

### Verification Performed

The code knowledge graph was used to find every public engine operation,
confirm their runner and conversion edges, inventory directly relevant root
tests, locate the internal cancellation assertions, and verify that no
package-level operation convenience functions exist. Important context,
error, ownership, and no-partial-result conclusions were confirmed against
source.

The following focused commands passed:

```sh
go test . -run 'Test(PrepareWorksWithFrameworkContractCorpus|RunSucceedsWithInjectedLLMClient|RunPassesPreparedRequestToInjectedLLMClient|EngineRunPropagatesCallerCancellation|ArtifactReaderFailuresPreserveArtifactLoadErrors|RunAddsLLMGenerateToCollaboratorPublicError|PrepareWithoutProfileMatchesSpecificPublicError|RunValidationFailureReturnsResult|PublicErrorsSupportErrorsIs|InspectProfileResolvesCredentialStatesWithoutPromptOrGeneration|InspectProfilePreservesPublicErrorIdentities|InspectProfileReturnsIndependentTargetMatchingPreparation|InspectPromptReturnsDeclaredMetadataWithoutExecutionWork|InspectPromptPreservesPublicErrorIdentities|InspectPromptReturnsIndependentMetadataMatchingPreparation|PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|PreparedExecutionLifecycleAndEngineBinding|PreparedExecutionConcurrentClaimAllowsOneGeneration|PreparedExecutionRunAndDiscardRaceHasOneWinner|PreparedExecutionDiscardAndFormattingDoNotExposePrivateState|PreparedExecutionCredentialCapacityAndTimingBoundaries)$'
go test -race . -run 'Test(EngineRunPropagatesCallerCancellation|InspectProfilePreservesPublicErrorIdentities|InspectPromptPreservesPublicErrorIdentities|PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|PreparedExecutionLifecycleAndEngineBinding|PreparedExecutionConcurrentClaimAllowsOneGeneration|PreparedExecutionRunAndDiscardRaceHasOneWinner)$' -count=3
go test ./internal/usecase -run 'TestRunnerRunCancellationPreservesGenerationCategory'
go test . -run 'Test(MapPublicErrorPreservesGenerationCancellation|MapPublicErrorTranslatesCapacityError)$'
```

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  operation-boundary review.
- Stages 7, 8, 10, 11, 13, 14, and 15 own prompt loading, profile loading,
  validation, runner preparation/execution, prepared-handle lifecycle,
  provider transport, and capacity mechanics respectively. Those stages
  should treat the facade behavior recorded here as their outward contract
  rather than repeat this public-boundary audit.

## Stage 5: Internal Domain And JSON-Compatible Values

### Scope Reviewed

The review covered every source and test file in `internal/domain` and
`internal/jsonvalue`. Narrow traces into the root conversion boundary,
backend registry, prompt renderer, provider request builder, and prepared-run
cloning were used only to confirm the assumptions those callers make about
session normalization, copied JSON-compatible values, credential redaction,
and frozen schemas. Their broader validation, execution, transport, and
registry behavior was not audited.

### Accepted Findings

#### S05-F01: Session normalization accepts values that JSON encoding changes

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/domain/session.go` (`NormalizeSessionID`),
  `internal/domain/session_test.go` (`TestNormalizeSessionID`), and callers in
  `internal/usecase`, `internal/prompt`, and `internal/llm`
- **Contract at issue:** A normalized session ID is opaque consumer metadata
  whose Unicode-code-point length is bounded and whose value is carried into
  prepared metadata, rendered-prompt hashing, collaborator requests, and the
  provider's JSON `session_id`. Normalization must not approve one byte string
  while downstream encoding transmits a different identifier.
- **Evidence:** `NormalizeSessionID` trims the string and counts runes but never
  checks `utf8.ValidString`. Go strings may contain invalid UTF-8, and
  `utf8.RuneCountInString` counts malformed bytes as error runes rather than
  rejecting them. A temporary probe passed `x\xffy`: normalization returned
  the original invalid string with no error, while `encoding/json` emitted
  `"x\ufffdy"`. Existing tests cover Unicode whitespace and the rune-count
  boundary but no malformed encoding. The runner hashes the normalized string
  before the provider request is JSON-encoded, so the exposed hash can also
  describe a different session value than the provider observes.
- **Failure mode:** A direct or rendered session ID containing malformed UTF-8
  is accepted, retained, and hashed in one form but silently replaced with
  Unicode replacement characters on the wire. Provider correlation and local
  prepared/result metadata can therefore disagree for an accepted request.
- **Recommended direction:** Make valid UTF-8 part of the shared normalization
  rule and reject malformed values before trimming/counting succeeds. Keep the
  error contextual but independent of provider-transport implementation.
- **Required verification:** Add malformed UTF-8 cases before, within, and
  after otherwise valid content to the domain table, then retain focused
  caller checks that direct-request failures map to `ErrInvalidRequest` and
  rendered-template failures map to the renderer category without provider
  work.

#### S05-F02: Numeric acceptance depends on the caller's Go representation

- **Category:** contract-documentation consistency
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/jsonvalue/jsonvalue.go` (`copyValue` and
  `maxSafeJSONInteger`), `internal/jsonvalue/jsonvalue_test.go`
  (`TestCopyMapRejectsInvalidValues` and
  `TestCopyMapValidatesJSONNumberSyntaxAndRange`), and the finite-number
  contracts in `types.go` and `backends.go`
- **Contract at issue:** Public extra-parameter contracts accept finite
  JSON-compatible numbers, and the shared copier promises to preserve
  compatible concrete numeric types. Equivalent numeric values should not
  become valid or invalid solely because the caller chose an integer,
  floating-point, or `json.Number` representation unless that distinction is
  an explicit contract.
- **Evidence:** Signed and unsigned integers outside `[-(2^53-1), 2^53-1]`
  are rejected, but finite floats receive no corresponding safe-integer check
  and `json.Number` is checked only for JSON syntax and finite `float64`
  range. A temporary probe submitted the exact value `9007199254740992` as
  `int64`, `float64`, and `json.Number`: only the `int64` was rejected. Go's
  JSON encoder can emit the integer spelling without losing it. Existing tests
  deliberately require rejection for the integer form while treating no
  cross-type boundary as policy, and the public GoDoc says only that numbers
  must be finite.
- **Failure mode:** Semantically equivalent backend, profile, or request extra
  parameters have different construction or request outcomes based on an
  incidental Go type. Consumers decoding into `json.Number` can bypass the
  integer limit that consumers using `int64` encounter, so the current limit
  neither implements the public finite-number contract nor a uniform safe-
  integer policy.
- **Recommended direction:** Establish one numeric acceptance rule in
  `internal/jsonvalue` and apply it consistently to every supported concrete
  representation. The current public contract points toward accepting all
  finite JSON-encodable numeric values; if a narrower interoperability limit
  is intentionally retained, make it an explicit public contract and enforce
  it for integral floats and `json.Number` as well.
- **Required verification:** Add a representation matrix at the largest
  accepted and first rejected positive and negative integer boundaries for
  signed integers, unsigned integers, integral floats, and `json.Number`, plus
  finite fractional/exponent and non-finite cases. Retain concrete-type
  assertions for accepted values and a public-boundary error-mapping check.

#### S05-F03: JSON-value copying has no nesting or work bound

- **Category:** correctness
- **Severity:** high
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/jsonvalue/jsonvalue.go` (`Copy`, `CopyMap`,
  `copyValue`, `copyMapValue`, and `copySequenceValue`) and
  `internal/jsonvalue/jsonvalue_test.go`
- **Contract at issue:** Consumer-controlled extra-parameter and schema values
  must fail as ordinary validation errors when their structure is unsafe to
  process. Cycle rejection alone does not bound recursive stack use or the
  amount of copying performed for an acyclic value.
- **Evidence:** Each pointer, map, slice, or array level recursively calls
  `copyValue`, with no depth, visited-node, or copied-node budget. The `seen`
  map tracks only the active recursion path and therefore detects cycles but
  imposes no size bound. A temporary probe built an acyclic chain 20,000 maps
  deep; `CopyMap` accepted and copied it. Sufficiently deeper caller-created
  values can continue growing the goroutine stack until Go's fatal stack
  limit. Shared acyclic subgraphs are also recopied once for every path rather
  than counted or memoized, so a compact caller value can induce much larger
  work. Existing tests cover direct map and slice cycles only.
- **Failure mode:** A deeply nested configuration or request can consume
  disproportionate CPU, allocations, and stack and can eventually terminate
  the process instead of returning `ErrInvalidConfig` or `ErrInvalidRequest`.
  The same generic path is used during engine construction, request
  conversion, backend lookup, and prepared schema/detail copying.
- **Recommended direction:** Give the shared copier an explicit, defensible
  traversal budget that bounds nesting and total copied work, returning a
  path-aware validation error when exceeded. Consider preserving already-
  copied acyclic aliases or otherwise account for repeated subgraphs so the
  bound covers expansion as well as source-node count. Keep the policy in this
  package rather than adding different limits at each caller.
- **Required verification:** Add just-below, at-limit, and first-over-limit
  cases for alternating map/slice/array nesting and for a shared acyclic
  subgraph that expands through multiple paths. Confirm public configuration
  and request callers translate the bounded failure without panic or provider
  work. Exercise the focused tests under constrained stack/memory settings if
  practical without making the default suite environment-dependent.

#### S05-F04: The generic copier's supported shape contract is only partially tested

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/jsonvalue/jsonvalue.go` and all four tests in
  `internal/jsonvalue/jsonvalue_test.go`
- **Contract at issue:** `Copy` and `CopyMap` are the single shared validator
  and ownership boundary for maps, slices, arrays, scalar and numeric concrete
  types, schemas with empty object keys, extra-parameter maps without empty
  keys, cycles, unsupported values, and JSON null versus empty containers. The
  reflection branches that implement those distinctions need compact tests at
  this package boundary.
- **Evidence:** Successful-copy tests cover one `map[string]int`, one
  `[]string`, `int64`, `json.Number`, and an empty schema-object key. Rejection
  tests cover non-string and empty map keys, one unsupported channel, map and
  slice cycles, non-finite floats, two out-of-range integers, and malformed
  `json.Number`. No test exercises the distinct array allocation path, named
  scalar/map/slice/array types, signed and unsigned width preservation,
  ordinary floats, pointer indirection, nil interface/typed map/typed slice
  collapse to JSON null, or nil-versus-empty map and slice preservation. The
  temporary probe confirmed typed nil maps and slices become nil while empty
  containers remain allocated, but this intended JSON distinction has no
  durable owner.
- **Failure mode:** A reflection refactor can silently change accepted types,
  return a different concrete type, alias an array or nested collection, or
  collapse an empty container to null without any focused test failing. Every
  engine configuration, request override, and prepared schema/detail path
  relies on this machinery.
- **Recommended direction:** Expand the package table by behavior branch, not
  by every type permutation: representative named and unnamed scalars, maps,
  slices, arrays, pointer/interface indirection, nil and empty containers, and
  mixed nested structures. Assert both deep mutation isolation and concrete
  type where preservation is promised. Keep higher-level tests to a small
  integration sample rather than repeating this matrix.
- **Required verification:** Run the focused package tests and representative
  backend, profile, request, and prepared-schema ownership tests. Confirm
  deliberate shallow-copy, array-allocation, type-conversion, and nil/empty
  regressions each fail at the shared package boundary.

#### S05-F05: Internal prepared-run JSON tests exercise an unused serialization boundary

- **Category:** testing
- **Severity:** low
- **Confidence:** high
- **Status:** accepted
- **Affected code:** JSON tags on `internal/domain.PreparedRun` and the three
  tests in `internal/domain/prepared_run_test.go`
- **Contract at issue:** The root `promptkit.PreparedRun` owns the stable
  consumer JSON representation. Internal domain values should be tested for
  invariants their internal consumers use, not as a parallel serialization
  contract with no production caller.
- **Evidence:** Production paths construct and clone `domain.PreparedRun`, then
  convert it to the root public value before consumer serialization. Source
  and graph searches found direct `json.Marshal` calls on the internal type
  only in `prepared_run_test.go`. The secret and session assertions overlap
  runner/public contract coverage, while the cache-control assertion is made
  only against the internal type and would remain green if root conversion
  dropped that field. The secret test also constructs a domain prepared value
  containing an API key even though the type's invariant says such values must
  never contain resolved credentials; it proves only that a dormant JSON tag
  hides the deliberately invalid state.
- **Failure mode:** Maintainers pay for and may preserve internal JSON tags and
  tests that do not protect the supported facade, while a regression in the
  public prepared conversion can escape the only cache-control serialization
  assertion. Legitimate internal representation refactors can require test
  edits without changing any consumer behavior.
- **Recommended direction:** Test credential absence at the producer and clone
  boundaries that own the domain invariant, and keep stable JSON assertions on
  the root public type. Move or replace the cache-control case at that public
  boundary if the compatibility risk warrants it; remove the parallel
  internal serialization expectations and tags unless an actual internal
  serialization consumer exists.
- **Required verification:** Confirm prepared construction and cloning never
  retain direct credentials, and assert session omission plus message
  cache-control behavior through root `PreparedRun` JSON. A source search
  should show no remaining production dependency before removing internal
  tags or tests.

### Unresolved Observations

None. Pointer values are currently dereferenced into JSON tree values and
typed nil pointers, maps, and slices collapse to JSON null. Those behaviors are
consistent with JSON encoding, but S05-F04 records the need to give the
supported nil and indirection distinctions durable package-level coverage.

### Coverage Ledger

- **Domain role and invalid states:** `internal/domain` is a dependency-neutral
  vocabulary of carrier types, enums, presence bits, and credential-redacted
  result shapes, not a collection of independently valid aggregate
  constructors. Prompt/profile/output/target validity remains with the
  parsers, registries, runner, and validators that have the necessary context.
  Zero enum values and partially populated carrier structs are therefore
  representable by design; callers validate before effectful use.
- **Session normalization:** One shared function trims Unicode whitespace,
  omits blank values, and measures the 256-character limit in Unicode code
  points. Direct request, rendered template, and transport callers all use it,
  avoiding divergent length rules. Invalid UTF-8 is the uncovered invariant
  defect recorded as S05-F01.
- **Credential containment:** Domain request and execution-target values can
  temporarily carry a direct API key for execution, with JSON/YAML tags that
  omit it. Preparation explicitly clears the credential before constructing a
  `PreparedRun`, execution adds it only to the transient generation target,
  and results clear it again. Focused use-case tests protect these producer
  invariants; dormant internal serialization tests are addressed by S05-F05.
- **Prepared and schema immutability:** Prepared execution takes separate deep
  snapshots for executable state and durable details. Cloning copies target
  extra parameters through `jsonvalue.CopyMap`, input hashes, rendered
  messages and cache-control pointers, structured-output wrappers, and schema
  trees through `jsonvalue.Copy`. `Details` produces another fresh snapshot.
  Root contract tests demonstrate that source/request/detail mutations do not
  alter execution or later details. Lifecycle mechanics remain Stage 13 scope.
- **Generic ownership:** `internal/jsonvalue` is the single owner for recursive
  validation and copying of arbitrary JSON-shaped trees. Root profiles and
  request overrides, backend construction/lookups, and prepared schema/detail
  cloning all call this package rather than maintaining separate recursive
  copiers. Shallow map copies in the runner operate only on already validated,
  engine-owned snapshots while applying precedence; no competing acceptance
  policy was found.
- **Supported values:** The implementation accepts nil, booleans, strings,
  finite floating-point values, bounded integer values, valid finite
  `json.Number`, string-keyed maps, slices, arrays, interfaces, and pointer
  indirection. It preserves assignable concrete scalar and collection types,
  otherwise produces canonical `map[string]any` or `[]any` trees. S05-F02
  records the inconsistent integer policy, and S05-F04 records missing branch
  protection.
- **Nil and empty distinctions:** A nil interface, pointer, map, or slice
  becomes JSON null; non-nil empty maps and slices remain non-nil empty
  containers. A nil top-level extra-parameter map remains nil. `Copy` permits
  empty object keys for JSON Schemas, while `CopyMap` rejects empty keys at
  every depth for provider extra parameters. These are coherent separate entry
  contracts rather than duplicated machinery.
- **Cycles and unsupported values:** Active-path identity tracking rejects
  pointer, map, and slice cycles, including nested cycles; maps with non-string
  keys, channels, functions, structs, complex values, unsafe pointers,
  malformed numbers, and non-finite floats are rejected with a structural
  path. The lack of an acyclic traversal bound is S05-F03.
- **Copy cost:** Ordinary accepted trees are visited and allocated once per
  occurrence, with sorted map keys making the first reported invalid path
  deterministic. Boundary copies occur when caller ownership changes, backend
  lookups publish snapshots, prepared execution separates payload and details,
  and details are returned. No unnecessary duplicate validation owner was
  found, but shared acyclic subgraphs can be expanded repeatedly as recorded
  in S05-F03.
- **Test ownership:** Domain session tests own the shared normalization rule;
  use-case tests own credential-free prepared construction and frozen
  execution; root tests own public snapshots and JSON. JSON-value package tests
  correctly use the narrow shared boundary but do not yet discriminate all
  supported reflection branches (S05-F04). Internal prepared JSON tests are on
  a non-production boundary (S05-F05).

### Verification Performed

The code knowledge graph was used to inventory every declaration and test in
both packages, trace all callers of `NormalizeSessionID`, `Copy`, and
`CopyMap`, and confirm prepared-run/schema clone and serialization ownership.
Important behavior was confirmed against complete package source and tests.

The following focused commands passed:

```sh
go test ./internal/domain ./internal/jsonvalue
go test ./internal/usecase -run 'Test(RunnerDirectSessionResolution|HashRenderedPromptIncludesSessionIDWhenPresent|RunnerPrepareExecutionCompletesWithoutAdmissionOrGeneration|RunnerRunPreparedKeepsDirectCredentialOutOfMetadata|ExecutionProfileToTargetPopulatesAllFieldsAndCopiesExtraParams)$'
go test . -run 'Test(PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|ExtraParamsTypedNestedValuesAreCopiedAcrossPublicBoundary|BackendExtraParamsAreDeeplyCopiedAtConstructionAndLookup|RunRejectsInvalidExtraParams)$'
go test -race ./internal/domain ./internal/jsonvalue -count=3
go test -race . -run 'Test(PreparedExecutionFreezesSourcesAndReturnsIndependentDetails|ExtraParamsTypedNestedValuesAreCopiedAcrossPublicBoundary|BackendExtraParamsAreDeeplyCopiedAtConstructionAndLookup)$' -count=3
```

A temporary program under the repository imported the two internal packages
and confirmed S05-F01, S05-F02, and the 20,000-level acceptance evidence for
S05-F03. It also recorded the current nil-versus-empty behavior for the
coverage ledger. The temporary source and directory were removed before the
audit artifact was edited.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  shared-value review.
- Stage 6 should use the numeric and traversal findings when reviewing backend
  extra parameters without repeating the generic copier audit. Stages 10 and
  13 own validation-plan construction and prepared-handle lifecycle; they
  should treat the schema-copy and credential-redaction behavior recorded here
  as established boundary evidence.
- Stage 11 owns runner precedence and execution coordination. The shallow
  runner map copies were consulted only to confirm that validated nested values
  already have a single owner; their broader merge behavior remains out of
  scope here.

## Stage 6: Backend Registry, Defaults, And Built-In Profiles

### Scope Reviewed

The review covered every source, test, and embedded YAML file in
`internal/backend`, `internal/defaults`, and `internal/profile/builtin`.
Narrow traces into `WithBackend`, `NewEngine`, execution-target resolution,
and the LLM-owned reserved request-field rule were used only to confirm public
translation, registry assembly, default consumption, and rule ownership.
Capacity admission and scheduling mechanics and outbound HTTP request
construction were not audited.

### Accepted Findings

#### S06-F01: The fixed model-request timeout is writable process-global state

- **Category:** clarity
- **Severity:** low
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/defaults/defaults.go`
  (`LLMRequestTimeoutDefault`) and its reads in
  `internal/llm/openai_compatible_client.go`
  (`NewOpenAICompatibleClient` and `OpenAICompatibleClient.Generate`)
- **Contract at issue:** Framework defaults are fixed, application-neutral
  policy. The architecture requires explicit dependencies rather than hidden
  process-global state, and engine instances must not acquire behavior from a
  writable package variable.
- **Evidence:** `LLMRequestTimeoutDefault` is declared as an exported package
  `var`, although `10 * time.Minute` is a constant expression and every other
  scalar in the defaults package is a constant. The model client reads this
  binding when it constructs a default or cloned HTTP client and again when a
  zero-valued internal client needs an HTTP client. A complete repository
  search found no writer, setter, or documented mutability contract; the
  binding is currently writable state solely because of its declaration.
- **Failure mode:** A later internal package or test can reassign the timeout
  and silently change clients constructed afterward. A concurrent write can
  also race with engine construction or the zero-value fallback, making a
  nominally immutable framework default engine-order-dependent. Assigning a
  non-positive duration would remove the intended whole-request cap.
- **Recommended direction:** Represent the timeout as a constant, preserving
  its value and existing transport semantics. Do not add a setter or a test
  that mutates the default; compile-time immutability is the stronger and
  cheaper invariant.
- **Required verification:** Run the focused model-client construction and
  deadline tests plus the race-enabled package suite. Confirm that all timeout
  consumers still compile and that no assignment relied on the former
  writable binding.

### Unresolved Observations

None. The OpenAI-compatible completion path is stored with other framework
constants but is consumed only by the model client; its placement does not
introduce mutable state or a competing rule. Actual URL and header construction
remains Stage 14 scope.

### Coverage Ledger

- **Registry construction and collisions:** `NewRegistry` builds one private
  map from the built-in OpenRouter definition followed by consumer additions.
  IDs are trimmed once, remain case-sensitive, and are checked after
  normalization for both built-in and consumer collisions. Construction is
  failure-atomic and publishes no partially populated registry. The public
  option merely translates fields and copies the queue-capacity pointer;
  validation has one owner in the registry.
- **Lookup and immutable snapshots:** The registry exposes no mutation or
  enumeration API. `GetBackend` returns a fresh deep copy of extra parameters,
  and `CapacityPolicies` creates a fresh map of scalar policy values. Nil
  receivers return a not-found error or an empty policy map rather than
  panicking. Focused tests mutate caller inputs, returned nested maps, and
  returned policy maps and demonstrate isolation across lookups.
- **Endpoint and credential metadata:** Backend endpoints are trimmed and must
  be absolute HTTP or HTTPS URLs with a host and without credentials, query
  text, or fragments. Credential environment names are optional, trimmed, and
  restricted to the documented portable identifier form. Existing package and
  root integration tests cover rejected endpoint classes, invalid environment
  names, trimmed values, and ordinary HTTP and HTTPS endpoints. Backend values
  expose no arbitrary header map, so there is no registry-owned header state
  to validate or copy; authorization and content-type construction belong to
  Stage 14.
- **Parameter validation:** Empty and reserved top-level parameter keys are
  rejected before registration. The registry consumes
  `llm.IsReservedOpenAIChatRequestField`, while the model client owns and tests
  the complete reserved-field list against its actual top-level payload. This
  preserves dependency direction and gives the registry one representative
  integration case rather than duplicating the transport's list. Recursive
  validation and copying remain owned by `internal/jsonvalue`; S05-F02 and
  S05-F03 already record its numeric inconsistency and missing traversal bound
  and were not repeated here.
- **Capacity policy normalization:** Negative limits and queue capacities,
  queues on unlimited backends, and overflowing total capacities are rejected.
  A positive limit with no explicit queue receives the documented capacity,
  while explicit zero is retained and unlimited backends produce no policy.
  Registry policy extraction is correct; permit acquisition, fairness,
  cancellation, and runtime bounds remain Stage 15 scope.
- **Default ownership:** The default execution target contains only the
  documented 600-second framework baseline; all optional provider controls
  remain unspecified. Schema, artifact-name, media-type, timeout, and
  OpenAI-compatible path constants are application-neutral library values,
  while OpenRouter capacity and connection defaults correctly remain with the
  backend registry. The only mutable-default concern is S06-F01.
- **Built-in backend and profile consistency:** All 24 embedded profiles load
  through the ordinary repository, have unique nonblank IDs, select the exact
  `openrouter` registry ID, and omit endpoint, API-key environment, and raw
  API-key fields. Their IDs and model values match the canonical catalog in
  `docs/formats.md`. Consumer profiles may intentionally override matching
  built-in profile IDs through repository precedence, whereas consumer
  backends may not replace the reserved built-in backend ID.
- **Test ownership and cost:** Backend package tests own registry validation,
  exact operational OpenRouter policy, copies, lookup errors, and capacity
  snapshots. Built-in repository tests own embedded-catalog validity and
  backend linkage. LLM tests own the reserved request-field list, and root
  tests retain only representative public assembly and copy behavior. No
  material redundant validation matrix or missing registry boundary test was
  found.

### Verification Performed

The code knowledge graph was used to inventory the three scoped packages,
trace registry and built-in repository assembly, find all consumers of the
defaults, and confirm that the reserved request-field function has exactly the
registry normalizer and provider payload builder as callers. Important
conclusions were confirmed against complete source, tests, embedded profiles,
and canonical documentation.

The following focused commands passed:

```sh
go test -cover ./internal/backend ./internal/defaults ./internal/profile/builtin
go test ./internal/llm -run 'TestOpenAICompatibleClientRejectsInvalidExtraParamsBeforeProviderCall|TestNewOpenAICompatibleClientDoesNotMutateSupplied(Nonzero|Zero)TimeoutClient|TestNewOpenAICompatibleClientTreatsSuppliedNegativeTimeoutAsUnset'
go test ./internal/usecase -run 'Test(ResolveExecutionTargetUsesBackendProfileAndRequestPrecedence|ResolveExecutionTargetDefaultsAndProfileZeros|RunnerInspectProfileResolvesProfileAndBackendOnce)'
go test . -run 'Test(BackendOptionsAccumulateAndRegistrationsAreEngineLocal|BackendRegistrationRejectsInvalidAndDuplicateDefinitions|BackendExtraParamsAreDeeplyCopiedAtConstructionAndLookup|WithBackendCopiesQueueCapacity|PrepareUsesBuiltInProfileWithoutProfileDir|CustomProfileOverridesBuiltInProfile|RunUsesResolvedBackendWithBuiltInLLMClient|EngineExecutionSettingPrecedence)$'
go test -race ./internal/backend ./internal/profile/builtin -count=3
go vet ./internal/backend ./internal/defaults ./internal/profile/builtin
```

The coverage diagnostic reported 94.0% statement coverage for
`internal/backend`, 100.0% for `internal/profile/builtin`, and no direct test
coverage for `internal/defaults`. Coverage alone was not treated as a finding:
the defaults are exercised through the consuming use-case, model-client,
artifact, validator, and root contract tests, and a separate test of constant
declarations would add no behavioral protection.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  registry and defaults review.
- Stage 8 owns general filesystem profile parsing, validation, discovery, and
  overlay mechanics. This stage established only that the embedded catalog
  supplies valid ordinary profiles tied to the built-in backend.
- Stage 14 owns completion-URL composition, authentication and content-type
  headers, payload merging and serialization, deadline behavior, response
  handling, and transport resources. It should treat the shared reserved-field
  ownership recorded here as established.
- Stage 15 owns admission, permit scheduling, queue behavior, fairness, and
  cancellation. It should treat the registry's normalized immutable capacity
  snapshot as established input.

## Stage 7: File Discovery And Prompt Definitions

### Scope Reviewed

The review covered every source, test, and fixture in `internal/filecatalog`
and `internal/promptdef`. The framework format reference and internal source
document supplied the owning contracts. Narrow traces through root prompt
source options, exact prompt inspection, and preparation were used only to
confirm source selection, error translation, and point-in-time repository
usage. Rendering, artifact loading, profile repositories, and schema loading
or validation were not audited.

### Accepted Findings

#### S07-F01: Content-file resolution escapes OS source roots and changes exact paths

- **Category:** correctness
- **Severity:** high
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`normalizePromptDefinition`, `normalizePromptDefinitionFromFS`, and their
  content readers), `internal/filecatalog/catalog.go` (`ResolveFSPath`), and
  content-file tests in `internal/promptdef/repository_test.go`
- **Contract at issue:** The framework format reference promises that a
  directory or `fs.FS` prompt's `content_file` resolves relative to the prompt
  file and remains within the configured source root. A path value also names
  an exact filesystem entry; checking whether it is blank must not silently
  substitute a different valid name.
- **Evidence:** The OS-directory normalizer receives only the prompt file path,
  not the repository root. It accepts an absolute `content_file` unchanged and
  cleans a relative path after joining it to the prompt directory, then calls
  `os.ReadFile` without a containment check. A temporary probe placed a prompt
  under `prompts/`, referenced `../outside.txt`, and observed the repository
  return the outside file's sentinel body successfully. Both OS and `fs.FS`
  resolution also call `strings.TrimSpace` on the path before opening it. A
  second probe created an existing file named `body ` and referenced the
  quoted YAML value `"./body "`; lookup instead tried `body` and failed with
  `ErrInvalidPromptDefinition`. Existing OS tests cover nested in-root
  resolution only, while escape rejection is tested only for directory-backed
  `fs.FS`.
- **Failure mode:** A prompt definition writable by a less-trusted source can
  read an arbitrary file reachable by the process and incorporate its contents
  into a template that may later be sent to a model provider. Independently, a
  valid source cannot reference legal filenames whose leading or trailing
  whitespace was preserved by YAML.
- **Recommended direction:** Give every directory-backed content resolver the
  actual source root and enforce relative, contained resolution before any
  read. Use trimming only to decide whether the configured path is blank, then
  resolve and open the original parsed value. Keep single-file source behavior
  relative to that file's directory and define its absolute-path rule
  explicitly rather than converting an absolute `fs.FS` path into a different
  relative path.
- **Required verification:** Run the same table against OS-directory,
  `WithPromptFS`, and single-file sources. Cover a sibling within the root, a
  parent path still within the root, a parent escape, an absolute path, and
  exact existing names with leading or trailing whitespace. Confirm rejected
  paths perform no outside read and public operations preserve
  `ErrPromptLoad`.

#### S07-F02: Error association runs before canonical ID and version selection

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`filesystemRepository.GetPromptDefinition`, `loadPromptDefinition`,
  `promptDefinitionFileHasID`, and `promptDefinitionDataHasID`) and selection
  cases in `internal/promptdef/repository_test.go`
- **Contract at issue:** Definitions are selected by normalized YAML `id`, not
  filename, and an optional version selects one exact ID/version pair.
  Malformed or invalid files outside that selector must not make an otherwise
  valid exact definition unavailable.
- **Evidence:** Both repository paths set `fileMatch` from the filename stem
  and immediately return a YAML or semantic error for that file even when it
  has no matching YAML ID. After a successful strict decode, both normalize
  the whole definition and return any semantic or referenced-content error
  whenever its ID matches, before checking whether a requested version
  matches. Temporary probes demonstrated both effects: malformed
  `target.yaml` shadowed a valid differently named definition whose YAML ID
  was `target`, and an invalid `target` version `2` blocked a valid exact
  lookup for version `1`. Several fixture cases intentionally request
  underscore filename stems rather than their hyphenated YAML IDs, so the
  current tests encode part of the noncanonical behavior instead of
  discriminating it.
- **Failure mode:** Adding or renaming an unrelated malformed file can break a
  valid prompt lookup solely because its filename happens to equal the
  requested ID. Likewise, a broken historical or future version can take every
  other exact version of the same prompt offline.
- **Recommended direction:** Associate strict-decoding and semantic failures
  only with selector metadata recovered from the YAML document. Apply the
  requested ID and version before content resolution and other semantic work;
  do not use filename stems as a second identity system. When malformed YAML
  does not provide reliable selector metadata, treat it as unrelated to a
  point lookup rather than contradicting the YAML-ID contract.
- **Required verification:** For both source implementations, pair one valid
  exact definition with a malformed same-stem/different-ID file and with an
  invalid same-ID/different-version file. Assert successful exact lookup, then
  retain selected-ID and selected-version malformed cases that return the
  contextual YAML or definition sentinel.

#### S07-F03: Strict decoding silently ignores additional YAML documents

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`loadPromptDefinitionFile` and `decodePromptDefinition`) and strict-decoding
  cases in `internal/promptdef/repository_test.go`
- **Contract at issue:** One prompt-definition file contains one strictly
  decoded definition. Every supplied YAML document must be accounted for;
  trailing documents cannot fall outside unknown-field and semantic
  validation.
- **Evidence:** Each decoder enables `KnownFields(true)` but calls `Decode`
  exactly once and returns without requiring end of stream. A temporary
  `fstest.MapFS` probe appended `---` and a second document containing an
  unknown field to a valid selected prompt. Lookup succeeded and returned only
  the first document. Existing tests cover unknown fields inside the first
  document but no document-stream boundary.
- **Failure mode:** Configuration after a document separator is silently
  ignored. A maintainer can believe a field change, replacement definition, or
  invalid setting is active while Promptkit hashes and executes only the
  earlier document, and strict decoding provides no diagnostic.
- **Recommended direction:** Require exactly one YAML document by decoding the
  selected definition and then requiring the next decode to return `io.EOF`.
  Preserve comments and ordinary trailing whitespace while rejecting any
  additional empty or non-empty document.
- **Required verification:** Add one shared strict-decoder table covering an
  ordinary document with comments, a second populated document, a second empty
  document, and malformed trailing YAML. Exercise one OS and one `fs.FS`
  repository boundary and preserve `ErrInvalidYAML` plus the source path.

#### S07-F04: Every lookup reads file-backed content for unrelated prompts

- **Category:** efficiency
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`filesystemRepository.GetPromptDefinition`, `loadPromptDefinition`,
  `normalizePromptDefinition`, and `normalizePromptDefinitionFromFS`)
- **Contract at issue:** A point-in-time lookup must scan definition metadata
  far enough to select an exact prompt and detect ambiguity, but it need not
  load template bodies for definitions whose ID or requested version already
  excludes them.
- **Evidence:** Both scan loops strictly decode and then fully normalize every
  valid YAML file before comparing `def.ID` and `def.Version`. Normalization
  reads every `content_file`. A counting-`fs.FS` probe performed two exact
  lookups of an inline `target` prompt in a source containing one unrelated
  file-backed prompt; the unrelated template was opened once per lookup. The
  behavior follows the same path for OS files. These reads are in addition to
  the directory walk and YAML-file reads needed for point-in-time selection.
- **Failure mode:** Lookup work scales with the total bytes of every
  file-backed template in the catalog rather than the selected prompt's
  content. Exact inspection, preparation, and ordinary execution repeatedly
  incur unrelated I/O; a large unused template can dominate lookup latency and
  filesystem load.
- **Recommended direction:** After strict decoding, compare normalized ID and
  requested version before resolving messages or reading content files. Keep
  the deterministic point-in-time directory scan and duplicate detection; no
  cache is required to remove the unrelated body reads.
- **Required verification:** Use a counting filesystem to show that selected
  content is read exactly once and unrelated content is never opened, while
  all YAML metadata needed for duplicate detection is still examined.
  Exercise repeated lookups to ensure the point-in-time contract remains
  intact.

#### S07-F05: OS and fs.FS repositories duplicate the same selection policy

- **Category:** duplication
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`filesystemRepository.GetPromptDefinition`, `loadPromptDefinition`,
  `loadPromptDefinitionFile`, `decodePromptDefinition`,
  `promptDefinitionFileHasID`, `promptDefinitionDataHasID`,
  `normalizePromptDefinition`, and `normalizePromptDefinitionFromFS`)
- **Contract at issue:** Configured directories and `fs.FS` roots implement
  one prompt discovery, strict-decoding, selection, duplicate, and
  content-resolution contract. Source mechanics may differ, but the semantic
  policy needs one owner so fixes and constraints cannot drift by source type.
- **Evidence:** The two repository paths independently implement nearly the
  same ordered scan, filename fallback, strict decode, loose ID recovery,
  semantic normalization, ID/version filtering, match collection, duplicate
  diagnostics, and not-found result. They also have paired byte-versus-path
  decode and ID helpers. The divergence is already observable:
  directory-backed `fs.FS` uses `ResolveFSPath` for lexical containment while
  the OS-directory path has none, and tests provide a much larger semantic
  matrix only for the OS implementation. This is the same semantic rule, not
  merely similar filesystem syntax.
- **Failure mode:** A selection, containment, strictness, or contextual-error
  fix can land in one path while the other retains old behavior. Consumers
  then get different validity or lookup results when replacing `Config.PromptDir`
  with `WithPromptFS`, despite the latter's explicit same-rules contract.
- **Recommended direction:** Give discovery and reads a small source adapter,
  then run one source-neutral decode, selector, normalization, duplicate, and
  error-classification algorithm. Keep OS versus `fs.FS` path display and
  content opening in the adapter where their real mechanics differ.
- **Required verification:** Run a shared behavioral suite against both source
  adapters for exact selection, ambiguity, malformed selected and unrelated
  files, content resolution, cancellation, and contextual errors. Retain only
  source-specific tests for genuinely different path representations or
  filesystem failures.

#### S07-F06: Prompt semantic validation has unprotected contract branches

- **Category:** testing
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/promptdef/filesystem_repository.go`
  (`normalizePromptDefinitionWithContent` and `isValidOutputFormat`),
  `internal/promptdef/repository_test.go`, and fixtures under
  `internal/promptdef/testdata`
- **Contract at issue:** Prompt package tests own required identity, messages,
  input declarations, content selection, cache control, and output-contract
  validation. Each independently implemented rejection rule needs compact
  protection proportionate to the parser's role as the file-format boundary.
- **Evidence:** The existing fixture matrix protects missing ID, missing
  messages, duplicate input names, content/content-file exclusivity, missing
  content, validation mode, schema-path dependency, and cache-control rules.
  It has no rejection case for a missing version, blank input name, blank
  message role, invalid output format, negative repair attempts, or an
  explicitly present blank `default_profile`. Statement coverage reflects
  some of these omissions—`isValidOutputFormat` reports only 66.7%—but the
  finding is the unprotected semantic decisions, not the percentage.
- **Failure mode:** A refactor can remove or invert any of these required-field
  or range checks while all focused parser tests remain green, allowing a
  malformed definition to reach hashing, rendering, or validation planning.
- **Recommended direction:** Add one compact table at the shared normalization
  or repository boundary for the missing semantic categories rather than six
  more standalone fixture files. Keep the existing fixtures where source
  resolution or strict nested YAML structure is the behavior under test.
- **Required verification:** Confirm each case returns
  `ErrInvalidPromptDefinition` through a repository with useful field or
  message context, and that a deliberate mutation of each rule fails its table
  row. One representative source is sufficient once S07-F05 gives both
  adapters a shared semantic implementation.

### Unresolved Observations

None. `fs.FS` containment is necessarily expressed in the supplied
filesystem's path namespace; whether a particular implementation follows
symlinks outside an operating-system directory is a property of that injected
filesystem and was not treated as a separate Promptkit security boundary.

### Coverage Ledger

- **Discovery:** OS and `fs.FS` discovery recurse, accept only lowercase
  `.yaml` and `.yml` suffixes, filter backups and other files, honor
  cancellation during walking, and return lexically sorted paths. Sorting
  makes duplicate diagnostics and scan order deterministic. No repeated scan
  within one lookup was found; each public point-in-time operation initiates
  one expected scan.
- **Root and relative paths:** `CleanFSRoot`, `DisplayPath`, `RelativePath`,
  and `ResolveFSPath` produce clean source-relative diagnostics and reject
  lexical `fs.FS` parent and absolute escapes. The OS content resolver does
  not use equivalent containment and all content resolvers alter exact
  whitespace-bearing names, as recorded in S07-F01.
- **Selection and duplicates:** Valid normalized ID/version pairs are selected
  independent of directory nesting, and sorted match paths make ambiguity
  errors stable. Version omission requires exactly one ID match; an explicit
  version permits other valid versions and rejects duplicate exact pairs.
  Error association before canonical selection is defective as S07-F02
  records.
- **Strict YAML and contextual failures:** Known-field decoding rejects
  unknown nested input and cache-control fields, and selected YAML,
  definition, content-read, duplicate, directory, not-found, and cancellation
  outcomes retain useful sentinels and paths through the public facade.
  Additional documents escape decoding as S07-F03 records. Unrelated
  malformed definitions are otherwise ignored so a point lookup is not a
  whole-catalog validity check.
- **Definition normalization:** IDs, versions, roles, input names, metadata,
  session templates, schema paths, default profiles, cache values, and enum
  declarations are normalized or validated into domain values. Inputs remain
  ordered and unique after trimming; messages require exactly one inline or
  file-backed body; cache control accepts only `ephemeral` with empty or `1h`
  TTL; output format, validation mode, schema dependency, and nonnegative
  repair attempts are enforced. The material test omissions are S07-F06.
- **Inline and file-backed content:** Inline templates preserve their body
  while whitespace-only content is rejected. Selected file-backed bodies are
  read eagerly so exact inspection and preparation validate the reference at
  the same point-in-time boundary. Containment and exact-name defects are
  S07-F01; unrelated eager reads are S07-F04. Rendering syntax and input-helper
  behavior remain Stage 9 scope.
- **Source parity and ownership:** Both sources share domain normalization but
  duplicate discovery-to-selection orchestration. S07-F05 records the
  resulting policy ownership and drift risk. File-catalog helpers remain
  appropriately shared with profile and validator packages rather than
  embedding prompt-specific behavior.
- **Fixtures and test value:** Static fixtures efficiently cover representative
  valid definitions, nested strict YAML, cache control, and content references;
  dynamic temporary files cover nesting, ambiguity, and contextual selection.
  The `fs.FS` cases add distinct source-containment and parity protection
  rather than repeating the full OS fixture matrix. No fixture should be
  removed solely for sharing a YAML shape; S07-F06 recommends a compact table
  only for currently absent scalar validation branches.

### Verification Performed

The code knowledge graph was used to inventory both packages, trace discovery
and path helpers into prompt, profile, and validator consumers, trace prompt
repository resolution through exact inspection and preparation, and compare
the two source implementations. Important behavior was confirmed against all
source, tests, fixtures, and canonical format and source documentation.

The following focused commands passed:

```sh
go test -cover ./internal/filecatalog ./internal/promptdef
go test ./internal/usecase -run 'Test(RunnerInspectPromptResolvesOneDefinitionWithoutExecutionCollaborators|RunnerInspectPromptClassifiesFailuresWithoutRepositoryWorkAfterCancellation|RunnerPrepareUsesThePromptInspectionSelectionAndHash|RunnerPrepareFileBackedPromptBodiesRenderCorrectly)$'
go test . -run 'Test(InspectPromptReturnsDeclaredMetadataWithoutExecutionWork|InspectPromptPreservesPublicErrorIdentities|InspectPromptReturnsIndependentMetadataMatchingPreparation|PrepareWorksWithPromptFSAndRelativeContentFile|PrepareWithPromptFSRejectsEscapedContentFile|PrepareWorksWithPromptFile|PromptRepositoryReadFailureMapsToPromptLoad)$'
go test -race ./internal/filecatalog ./internal/promptdef -count=3
go vet ./internal/filecatalog ./internal/promptdef
```

The coverage diagnostic reported 92.9% statement coverage for
`internal/filecatalog` and 84.3% for `internal/promptdef`. Coverage output was
used only to locate unexamined decisions; S07-F06 is based on direct comparison
of production validation branches with tests and fixtures.

Temporary package probes, removed before this artifact was edited, confirmed:

- an OS-directory `../outside.txt` content reference returned the outside
  sentinel body;
- an existing whitespace-suffixed content filename was changed before lookup;
- malformed `target.yaml` shadowed a valid prompt whose YAML ID was `target`;
- an invalid unrequested version blocked a valid requested version;
- a second YAML document with an unknown field was ignored; and
- a counting filesystem observed one unrelated template-body open per exact
  lookup.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  discovery and prompt-definition review.
- Stage 8 owns profile-specific decoding, selection, source parity, and
  repository composition. It should reuse the established file-catalog
  behavior but independently assess whether profile selection or YAML stream
  handling has analogous defects.
- Stage 9 owns ordinary artifact reads and prompt/session rendering, including
  template parsing, variables, input helpers, cache-control propagation, and
  rendered-message ownership. This stage established only the definition and
  selected template bodies supplied to it.
- Stage 10 owns schema-source containment, schema loading, reference
  resolution, validation modes at execution, and frozen validation plans.
  Prompt parsing here only verifies the declared output fields.

## Stage 8: Profile Sources And Repository Composition

### Scope Reviewed

The review covered all production code, tests, and fixtures in
`internal/profile` except the built-in subpackage. The profile format contract,
internal source documentation, root repository composition, profile source
options, and the narrow profile-inspection and preparation call paths were
consulted to establish precedence, public error translation, and selection
normalization. Runtime merging with backend definitions and request overrides
was not audited.

### Accepted Findings

#### S08-F01: Non-finite profile settings bypass numeric range validation

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`validateProfile`), `profiles.go` (`validatePublicProfile`), profile
  validation cases in `internal/profile/repository_test.go`, and in-memory
  profile validation tests in `engine_test.go`
- **Contract at issue:** Profile `temperature` must be a number from zero
  through two and `top_p` must be a number from zero through one. File-backed
  and in-memory profiles follow the same ranges; values outside those closed
  intervals cannot enter an execution profile.
- **Evidence:** Both validators implement the floating-point bounds solely as
  less-than and greater-than comparisons. IEEE NaN makes every such comparison
  false. YAML supports `.nan`, and a temporary `fstest.MapFS` profile with
  both `temperature: .nan` and `top_p: .nan` loaded successfully with NaN
  values in the returned `domain.ExecutionProfile`. Go callers can supply
  the same values to the duplicated in-memory validator. No focused profile
  test uses a non-finite setting.
- **Failure mode:** Exact inspection and preparation can accept a profile whose
  numeric controls are outside the documented domain. The value can then reach
  an injected model client or fail much later during default-client JSON
  serialization, changing a profile-load error into a generation-time failure.
- **Recommended direction:** Reject NaN and infinity explicitly for every
  floating profile setting before applying its closed numeric range. Resolve
  this in the shared semantic validator already recommended by S02-F02 so file
  and in-memory sources cannot diverge.
- **Required verification:** Run one shared boundary table against both source
  categories. Include finite lower and upper bounds, their finite neighbors
  outside the range, positive and negative infinity, and NaN for temperature
  and top-p. File-source failures must retain `ErrInvalidProfile`; in-memory
  failures must retain the public `ErrInvalidConfig` construction boundary.

#### S08-F02: File-backed extra parameters skip profile-boundary validation

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`loadProfile` and `validateProfile`),
  `internal/domain/domain.go` (`ExecutionProfile.ExtraParams`), and the
  extra-parameter case in `internal/profile/repository_test.go`
- **Contract at issue:** Profile `extra_params` accepts only
  JSON-compatible values with non-empty string keys. Loading and validating a
  file profile must establish that invariant before exact inspection,
  preparation, or an injected client consumes the resulting execution
  profile.
- **Evidence:** YAML is decoded directly into
  `domain.ExecutionProfile.ExtraParams`, and `validateProfile` never invokes
  the repository's `internal/jsonvalue` validator. The existing test proves
  that one valid nested map can be marshaled but has no rejection cases. A
  temporary profile containing an empty key and a `.nan` value loaded
  successfully; immediately marshaling the returned map with `encoding/json`
  failed with `json: unsupported value: NaN`. The in-memory path, by
  contrast, validates and deeply copies the same field through
  `jsonvalue.CopyMap`.
- **Failure mode:** `InspectProfile` and preparation can report success for a
  profile that violates its file format. Default-client execution fails only
  at payload construction, while an injected client receives a value the
  public format contract says cannot exist.
- **Recommended direction:** Validate and deeply copy decoded
  `extra_params` through the shared JSON-value owner as part of profile
  normalization. Keep OpenAI-compatible reserved-field collision policy with
  its existing client/registry owners; this finding concerns the universal
  JSON-compatible shape only.
- **Required verification:** Add a compact repository table for empty keys,
  non-finite numbers, unsupported YAML-decoded values, nested invalid values,
  and a representative valid nested tree. Run it through OS-directory and
  `fs.FS` sources, confirm `ErrInvalidProfile` and source-path context, and
  retain one public preparation or inspection check for `ErrProfileLoad`.

#### S08-F03: Filename stems can make malformed unrelated profiles authoritative

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`loadProfile`, `readProfileFileMetadata`, and `profileFileMetadata`)
  and selected-error cases in `internal/profile/repository_test.go`
- **Contract at issue:** Definitions are selected by their YAML `id`, not
  filename. A higher-precedence source is authoritative only when it contains
  the requested ID; an unrelated malformed file must not block a valid
  definition in the same source or fallback chain.
- **Evidence:** Before strict decoding, `loadProfile` treats either the
  metadata ID or the filename stem as an ID match. A matching stem therefore
  turns an unknown-field error or top-level raw `api_key` into a selected
  source failure even when parsed metadata identifies a different profile.
  A temporary source containing malformed `target.yaml` with YAML ID
  `unrelated` and valid `valid.yaml` with YAML ID `target` returned
  `ErrInvalidYAML` instead of the valid profile. Existing invalid-YAML and
  raw-key fixtures are requested by underscore filename stems, so those tests
  encode the second identity system rather than distinguishing it.
- **Failure mode:** Adding or renaming an unrelated malformed file can take a
  valid profile offline. In an ordinary or application fallback source, the
  same filename can also prevent resolution from reaching a valid
  lower-precedence profile or built-in.
- **Recommended direction:** Use recovered YAML metadata as the sole authority
  for point selection and raw-key classification. Do not infer identity from a
  filename. When malformed YAML provides no reliable ID, treat it as unrelated
  to an exact lookup rather than contradicting the YAML-ID contract.
- **Required verification:** Exercise both OS and `fs.FS` repositories with
  a malformed same-stem/different-ID file beside a valid exact definition.
  Repeat through an overlay with the valid definition in the fallback. Retain
  canonical-ID cases showing that a selected unknown field and raw
  `api_key` stop fallback with their contextual sentinel.

#### S08-F04: Strict profile decoding silently ignores additional YAML documents

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`loadProfile` and `readProfileFileMetadata`) and strict-decoding cases
  in `internal/profile/repository_test.go`
- **Contract at issue:** One profile file contains one strictly decoded
  definition. Every YAML document supplied in that file must be accounted for;
  later documents cannot bypass known-field, raw-key, or semantic validation.
- **Evidence:** Both the metadata decoder and the strict typed decoder call
  `Decode` once and return without requiring end of stream. A temporary
  selected profile followed by `---` and a second same-ID document containing
  an unknown field loaded successfully and returned only the first model.
  Existing strict-decoding tests place unknown fields in the first document
  and never exercise the stream boundary.
- **Failure mode:** Configuration after a YAML document separator is silently
  ignored. A maintainer can believe a replacement model, credential setting,
  or provider option is active while inspection and execution use only the
  earlier document.
- **Recommended direction:** Require exactly one YAML document by decoding the
  definition and then requiring the next decode to return `io.EOF`. Apply
  the same stream rule to metadata classification so later raw-key or identity
  data cannot escape the selected-source decision.
- **Required verification:** Add a shared strict-decoder table covering one
  document with comments, a second populated document, a second empty
  document, malformed trailing YAML, and a raw key in a trailing document.
  Verify OS and `fs.FS` boundaries preserve `ErrInvalidYAML` and source-path
  context.

#### S08-F05: Whitespace-bearing file profile IDs are valid but publicly unreachable

- **Category:** correctness
- **Severity:** medium
- **Confidence:** confirmed
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`loadProfile`, `readProfileFileMetadata`, and `validateProfile`),
  `internal/usecase/profile_inspection.go` (`Runner.InspectProfile`), and
  profile selection in `internal/usecase/runner.go`
- **Contract at issue:** A file profile ID is required to be non-empty, and
  public request/default and inspection selection normalize surrounding
  whitespace. Every profile accepted under that rule must have one reachable,
  normalized identity, consistent with in-memory profiles whose IDs are
  explicitly trimmed.
- **Evidence:** Metadata extraction trims the YAML ID, but the strict
  `domain.ExecutionProfile.ID` is neither trimmed nor rejected when it has
  surrounding whitespace. `loadProfile` compares that raw ID to the requested
  ID before validation. A temporary file with `id: "  target  "` returned
  `ErrProfileNotFound` for `target`. Calling the internal repository with
  the whitespace-bearing string can select and validate it, but every public
  selection path trims the lookup ID first, making the definition unreachable
  through the engine.
- **Failure mode:** A syntactically accepted profile silently behaves as
  absent and resolution may fall through to a lower-precedence profile with a
  different model or endpoint. The file contents and metadata classification
  disagree about the source's authoritative ID.
- **Recommended direction:** Normalize the decoded profile ID once before
  selection and validation, as the in-memory path does, or explicitly reject
  surrounding whitespace in the file-format contract. Use that one normalized
  value for metadata association, duplicate detection, returned profiles, and
  diagnostics.
- **Required verification:** Cover leading and trailing whitespace, a
  whitespace-only ID, duplicate IDs that become equal after normalization, and
  an ordinary normalized ID. Verify exact inspection and preparation select
  the same normalized profile and report the normalized ID.

#### S08-F06: Every profile file is decoded twice during each source lookup

- **Category:** efficiency
- **Severity:** medium
- **Confidence:** high
- **Status:** accepted
- **Affected code:** `internal/profile/filesystem_repository.go`
  (`loadProfile` and `readProfileFileMetadata`) and point-in-time profile
  lookup through the repository overlay
- **Contract at issue:** Exact point-in-time lookup must read enough metadata
  across one source to select an ID and detect duplicates, but it need not
  parse every complete YAML tree twice or strictly materialize unrelated
  profiles.
- **Evidence:** For every discovered YAML file, `loadProfile` first invokes a
  YAML decoder through `readProfileFileMetadata`, then unconditionally
  creates a second strict decoder for the same bytes. This happens for valid
  unrelated profiles as well as the selected profile. A lookup that falls
  through overlays repeats the catalog scan in each source; successful
  built-in fallback currently means two decodes for each catalog entry on
  every inspection, preparation, or ordinary run lookup. The file bytes are
  read once, so the confirmed waste is parsing and allocation rather than
  duplicate filesystem reads.
- **Failure mode:** CPU and allocation cost includes an avoidable additional
  operation linear in the total YAML bytes of every consulted catalog. Large
  consumer profile sources magnify that work on each point-in-time operation,
  including repeated inspection and execution.
- **Recommended direction:** Perform one metadata pass across the source, then
  strictly decode and normalize only canonical ID matches, or otherwise
  arrange one parse to supply both classification and strict selected
  decoding. Preserve the uncached point-in-time source behavior and
  deterministic duplicate detection.
- **Required verification:** Benchmark representative small and large catalogs
  before and after the change, reporting allocations as well as time. Retain
  behavior tests for selected malformed files, unrelated malformed files,
  duplicates, and repeated lookups so the optimization does not turn source
  access into a stale cache.

### Unresolved Observations

None. Reserved OpenAI-compatible request-field collisions are deliberately
validated by the model-client and backend-registry owners and remain outside
this profile-source pass.

### Coverage Ledger

- **Strict decoding and raw credentials:** The first YAML document is decoded
  with known fields enabled. Selected unknown fields preserve
  `ErrInvalidYAML`, and a top-level raw `api_key` is detected separately so
  it preserves `ErrRawAPIKeyNotAllowed`. Unknown or raw-key definitions with
  a reliably different metadata ID do not block a valid lookup. Filename
  association and additional document handling are defective as S08-F03 and
  S08-F04 record.
- **Profile validation:** Selected profiles require a nonblank ID, one of
  backend or endpoint, and a nonblank model. Backend IDs are trimmed, numeric
  finite values within the documented ranges are accepted, and ordinary
  nested `extra_params` decode into the domain value. Non-finite scalar
  values and universal extra-parameter shape are not enforced as S08-F01 and
  S08-F02 record. The already accepted S02-F02 owns consolidation of the
  duplicated file and in-memory semantic validators.
- **Filesystem parity:** OS-directory repositories adapt their directory with
  `os.DirFS`; caller-supplied `fs.FS` repositories then enter the same
  `loadProfile` implementation and shared file catalog. Recursive discovery,
  extension filtering, deterministic ordering, strict decoding, validation,
  duplicate behavior, and error classification therefore have one semantic
  implementation. Source-specific tests appropriately confirm a real OS
  directory and representative `fs.FS` behavior without duplicating the
  complete validation matrix.
- **Identity and duplicates:** Valid matching YAML IDs are independent of
  directory nesting, and all matches are collected before duplicate
  classification. File-catalog sorting makes duplicate path diagnostics
  deterministic. IDs that differ only by accepted surrounding whitespace do
  not share the public normalized identity, as S08-F05 records.
- **Overlay and fallback:** The root assembles repositories in the documented
  order: in-memory, ordinary configured source, application fallback, then
  embedded built-ins. Each overlay consults its fallback only for
  `ErrProfileNotFound`; YAML, validation, raw-key, duplicate, directory,
  read, and cancellation failures stop resolution. Definitions are complete
  values and are never field-merged. Root contract tests add useful
  composition protection without repeating the repository's parser matrix.
- **Absence and authoritative failures:** Reliably unrelated malformed and
  raw-key files are ignored during a point lookup, while canonical matching
  failures are contextual and authoritative. A missing configured directory
  remains a profile-load failure instead of silently becoming a built-in
  miss. Filename fallback incorrectly broadens authority as S08-F03 records.
- **Errors and cancellation:** Blank lookup IDs preserve
  `ErrInvalidProfile`; absent IDs preserve `ErrProfileNotFound`; selected
  syntax, semantic, credential, duplicate, discovery, and read failures retain
  useful source-relative paths or directory context. File discovery and the
  per-file loop honor context cancellation, and overlays do not fall back
  after a cancellation error. Public exact absence remains
  `ErrProfileNotFound`, while other repository failures map to
  `ErrProfileLoad`.
- **Ownership and immutability:** Each file lookup decodes a fresh domain
  profile, so caller mutation is not retained by the repository. The in-memory
  adapter stores validated copies and returns a new profile with copied
  `extra_params`; overlays do not mutate returned definitions. Resolution
  and public conversion create later copies, with runtime override and backend
  merging deferred to Stage 11. The invalid source values in S08-F01 and
  S08-F02 must be rejected before those immutable snapshots are created.
- **Repeated work:** Point-in-time inspection, preparation, and execution
  intentionally perform fresh source lookup, and no stale repository cache was
  found. Each YAML file is read once per consulted source lookup. The
  additional catalog-wide decoder pass is the avoidable work in S08-F06.
- **Test ownership:** Repository tests own YAML selection, source recursion,
  raw-key rejection, profile validation, duplicates, and overlay semantics.
  Root tests own option composition, complete precedence, lazy source access,
  and public error translation. Use-case inspection tests own one exact
  repository lookup and collaborator-free inspection behavior. No material
  high-level repetition of the full parser matrix was found; the missing
  regression cases are tied directly to the accepted findings above and the
  established S02-F02 boundary table.

### Verification Performed

The code knowledge graph was used to inventory the scoped package, trace both
source constructors and overlay construction into `NewEngine`, trace profile
lookups into exact inspection and preparation, and identify all consumers of
`domain.ExecutionProfile`. Important conclusions were confirmed against the
complete source, repository tests, profile fixtures, public GoDoc, and
canonical profile and source contracts.

The following focused commands passed:

```sh
profile_audit_cover=$(mktemp)
go test -coverprofile="$profile_audit_cover" ./internal/profile
go tool cover -func="$profile_audit_cover"
rm "$profile_audit_cover"
go test ./internal/usecase -run 'TestRunnerInspectProfile'
go test . -run 'Test(CustomProfileOverridesBuiltInProfile|MalformedCustomProfileDoesNotFallbackToBuiltIn|PrepareWorksWithProfile(FS|File)OverBuiltIns|FallbackProfileSource(Precedence|PreservesLazyLoadingAndErrors|WorksAcrossWorkflows)|SelectedProfile(RawAPIKey|InvalidYAML|RepositoryReadFailure)MapsToProfileLoad)$'
go test -race ./internal/profile -count=3
go vet ./internal/profile
```

The coverage diagnostic reported 85.6% statement coverage for
`internal/profile`; `validateProfile` reported 66.7%. Coverage was used only
to find decisions for direct inspection. The accepted findings are based on
source traces and reproduced behavior, not the percentages.

Temporary package probes, removed before this artifact was edited, confirmed:

- malformed `target.yaml` with a different YAML ID shadowed a valid exact
  definition;
- a second YAML document containing an unknown field was ignored;
- NaN temperature and top-p values passed profile validation;
- an empty-key, NaN-bearing `extra_params` map loaded and then failed JSON
  serialization; and
- a whitespace-bearing YAML ID was absent under the normalized public lookup
  identity.

### Handoff

- The Stage 0 baseline remains absent and was not backfilled during this
  profile-source review.
- S02-F02 already owns consolidation of file and in-memory profile semantic
  validation. S08-F01 and S08-F02 supply confirmed correctness requirements
  for that shared owner rather than creating a second duplication finding.
- Stage 11 owns backend lookup, default/profile/request merge precedence,
  effective-target validation, credential resolution, and runtime override
  semantics. It should treat the selected immutable profile and source
  precedence recorded here as established inputs.
- Stage 14 owns default-client reserved-field rejection and outbound JSON
  payload construction. It should distinguish those transport-specific checks
  from the universal profile-shape defect in S08-F02.