Identify built-in generation preparation failures

docs/roadmap/implementation.md

@@ -198,6 +198,11 @@ fails with the public invalid-request category and zero dispatch. Existing
 provider rejection, missing-key, capacity, injected, and cancellation tests
 retain their respective outcomes.
 
+Completion: built-in preparation failures carry direct error and evidence
+markers; diagnostics return invalid-request errors before dispatch. Generation,
+use-case, and root tests pass on Go 1.27.3, including the previously deferred
+injected-client classification cases.
+
 ## Stage 7: Bound Authentication Recognition And Report Overflow
 
 **Catalog:** 2. **Files:** current authentication probe, public/domain smoke reasons.

internal/generation/coordinator.go

@@ -85,6 +85,12 @@ func (c *Coordinator) GenerateWithEvidence(
 	return c.generate(ctx, req, true)
 }
 
+// PreparationError identifies a built-in request preparation failure.
+type PreparationError struct{ Cause error }
+
+func (e *PreparationError) Error() string { return e.Cause.Error() }
+func (e *PreparationError) Unwrap() error { return e.Cause }
+
 func (c *Coordinator) generate(
 	ctx context.Context,
 	req domain.GenerateRequest,
@@ -95,7 +101,7 @@ func (c *Coordinator) generate(
 	}
 	prepared, err := c.builtIn.PrepareGeneration(req)
 	if err != nil {
-		return nil, err, GenerationEvidence{}
+		return nil, &PreparationError{Cause: err}, GenerationEvidence{PreparationFailed: true}
 	}
 
 	evidence := GenerationEvidence{}

internal/generation/evidence.go

@@ -10,6 +10,8 @@ import (
 // GenerationEvidence contains invocation-local request evidence without raw
 // provider bodies, headers, credentials, or generated content.
 type GenerationEvidence struct {
+	// PreparationFailed identifies a built-in request rejected before attempts.
+	PreparationFailed bool
 	// InitialEndpoint is the frozen built-in request URL, if prepared.
 	// Injected generation leaves it unknown.
 	InitialEndpoint string

internal/usecase/prepared_execution_test.go

@@ -498,7 +498,7 @@ func TestRunnerRunPreparedReleasesAdmissionAcrossExecutionErrors(t *testing.T) {
 				}},
 			},
 			repairer:   &fakeRepairer{err: repairInvalidRequest},
-			wantError:  ErrInvalidRequest,
+			wantError:  ErrLLMGenerate,
 			wantSource: repairInvalidRequest,
 		},
 		{

internal/usecase/runner.go

@@ -18,6 +18,7 @@ import (
 	"go.maximumdirect.net/promptkit/internal/capacity"
 	"go.maximumdirect.net/promptkit/internal/defaults"
 	"go.maximumdirect.net/promptkit/internal/domain"
+	"go.maximumdirect.net/promptkit/internal/generation"
 	"go.maximumdirect.net/promptkit/internal/jsonvalue"
 	"go.maximumdirect.net/promptkit/internal/llm"
 	"go.maximumdirect.net/promptkit/internal/observation"
@@ -269,6 +270,9 @@ func (r *Runner) executePreparedRun(
 }
 
 func wrapGenerationError(err error) error {
+	if _, ok := err.(*generation.PreparationError); ok {
+		return &OperationError{Category: ErrInvalidRequest, Cause: err}
+	}
 	return &OperationError{Category: ErrLLMGenerate, Cause: err}
 }
 

internal/usecase/runner_test.go

@@ -2074,7 +2074,7 @@ func TestRunnerRunCancellationPreservesGenerationCategory(t *testing.T) {
 	}
 }
 
-func TestRunnerRunLLMInvalidRequestMapsToUsecaseInvalidRequest(t *testing.T) {
+func TestRunnerRunInjectedInvalidRequestRemainsGenerationFailure(t *testing.T) {
 	runner := NewRunner(
 		&fakePromptRepo{def: promptDef(domain.FormatText, domain.ValidationNone, 0)},
 		&fakeExecutionProfileRepo{profiles: map[string]*domain.ExecutionProfile{"exec": defaultExecutionProfile()}},
@@ -2089,11 +2089,8 @@ func TestRunnerRunLLMInvalidRequestMapsToUsecaseInvalidRequest(t *testing.T) {
 		ProfileID: "exec",
 		Inputs:    singleInputRef(),
 	})
-	if !errors.Is(err, ErrInvalidRequest) {
+	if !errors.Is(err, ErrLLMGenerate) || !errors.Is(err, llm.ErrInvalidRequest) {
-		t.Fatalf("expected ErrInvalidRequest, got %v", err)
+		t.Fatalf("expected generation error retaining cause, got %v", err)
-	}
-	if errors.Is(err, ErrLLMGenerate) {
-		t.Fatalf("did not expect ErrLLMGenerate, got %v", err)
 	}
 }
 

internal/usecase/smoke_tester.go

@@ -210,6 +210,9 @@ func (t *SmokeTester) runInference(
 		report.Failure = generation.ClassifyFailure(contextErr)
 		return finish(contextErr)
 	}
+	if evidence.PreparationFailed && generationErr != nil {
+		return nil, &OperationError{Category: ErrInvalidRequest, Cause: generationErr}
+	}
 	if generationErr != nil {
 		report.Failure = generation.ClassifyFailure(generationErr)
 		report.Completed = true

preparation_error_contract_test.go

@@ -0,0 +1,29 @@
+package promptkit_test
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"testing"
+
+	"go.maximumdirect.net/promptkit"
+)
+
+func TestBuiltInPreparationFailureIsInvalidRequestWithoutDispatch(t *testing.T) {
+	calls := 0
+	cfg := simpleConfig("hello")
+	cfg.HTTPClient = &http.Client{Transport: roundTripFunc(func(*http.Request) (*http.Response, error) { calls++; return nil, errors.New("unexpected dispatch") })}
+	engine, err := promptkit.NewEngine(cfg)
+	if err != nil {
+		t.Fatal(err)
+	}
+	override := &promptkit.ExecutionTargetOverride{ExtraParams: map[string]any{"model": "reserved"}}
+	_, err = engine.Run(context.Background(), promptkit.RunRequest{PromptID: "prompt", Execution: override})
+	if !errors.Is(err, promptkit.ErrInvalidRequest) || calls != 0 {
+		t.Fatalf("run error = %v, calls = %d", err, calls)
+	}
+	report, err := engine.SmokeTest(context.Background(), promptkit.SmokeTestRequest{Kind: promptkit.SmokeTestTextInference, ProfileID: "profile", Execution: override})
+	if !errors.Is(err, promptkit.ErrInvalidRequest) || report != nil || calls != 0 {
+		t.Fatalf("smoke = %+v, %v, calls = %d", report, err, calls)
+	}
+}