diff --git a/docs/roadmap/implementation.md b/docs/roadmap/implementation.md
index 38c63c3..2c01e7f 100644
--- a/docs/roadmap/implementation.md
+++ b/docs/roadmap/implementation.md
@@ -188,6 +188,8 @@ GOWORK=off go test -race -count=1 ./internal/adapters/promptkit ./internal/app
 
 ### Stage 3: Extend The Project-Owned Prompt Execution Contract
 
+Status: Complete.
+
 Purpose: establish dependency-neutral repair and structured-generation-error
 values before the adapter or application relies on them.
 
diff --git a/internal/adapters/promptkit/adapter.go b/internal/adapters/promptkit/adapter.go
index 3660866..811fee4 100644
--- a/internal/adapters/promptkit/adapter.go
+++ b/internal/adapters/promptkit/adapter.go
@@ -193,6 +193,7 @@ func executionValue(value *promptkit.RunResult, captureDebug bool) *promptexec.E
 		promptexec.ValidationStatus(value.Validation.Status),
 		string(value.Validation.Mode),
 		value.Validation.SchemaPath,
+		0,
 		value.Validation.Errors,
 	)
 	rawOutput := []byte(nil)
@@ -203,6 +204,7 @@ func executionValue(value *promptkit.RunResult, captureDebug bool) *promptexec.E
 			promptexec.ValidationFailed,
 			string(value.Validation.Mode),
 			value.Validation.SchemaPath,
+			0,
 			[]string{"generated output exceeds the configured size limit"},
 		)
 	}
diff --git a/internal/app/comparison_execution_test.go b/internal/app/comparison_execution_test.go
index d072c3f..14f1762 100644
--- a/internal/app/comparison_execution_test.go
+++ b/internal/app/comparison_execution_test.go
@@ -202,7 +202,7 @@ func (e *barrierExecutor) Execute(ctx context.Context, req promptexec.ExecuteReq
 		PromptID: req.PromptID, PromptVersion: req.PromptVersion, PromptHash: generationPromptHash,
 		ProfileID: req.ProfileID, BackendID: profile.BackendID, ModelName: profile.ModelName,
 		StartedAt: stamp, EndedAt: stamp, RawOutput: comparisonRawOutput(),
-		Validation: promptexec.NewValidation(promptexec.ValidationPassed, "json_schema", generationDefinitionForPrompt(req.PromptID).GeneratedTextSchemaID+".generated_text.schema.json", nil),
+		Validation: promptexec.NewValidation(promptexec.ValidationPassed, "json_schema", generationDefinitionForPrompt(req.PromptID).GeneratedTextSchemaID+".generated_text.schema.json", 0, nil),
 	}, nil
 }
 
diff --git a/internal/app/generation_test.go b/internal/app/generation_test.go
index d570c1a..348ed26 100644
--- a/internal/app/generation_test.go
+++ b/internal/app/generation_test.go
@@ -162,7 +162,7 @@ func (e *generationExecutor) Execute(ctx context.Context, req promptexec.Execute
 	if cancelBeforeReturn != nil {
 		cancelBeforeReturn()
 	}
-	execution := &promptexec.Execution{RunID: "provider-run", PromptID: req.PromptID, PromptVersion: req.PromptVersion, PromptHash: generationPromptHash, RenderedPromptHash: "rendered-hash", ProfileID: req.ProfileID, BackendID: "fixture", ModelName: "fixture-model", StartedAt: stamp, EndedAt: stamp, RawOutput: rawOutput, Validation: promptexec.NewValidation(status, "json_schema", generationDefinitionForPrompt(req.PromptID).GeneratedTextSchemaID+".generated_text.schema.json", nil)}
+	execution := &promptexec.Execution{RunID: "provider-run", PromptID: req.PromptID, PromptVersion: req.PromptVersion, PromptHash: generationPromptHash, RenderedPromptHash: "rendered-hash", ProfileID: req.ProfileID, BackendID: "fixture", ModelName: "fixture-model", StartedAt: stamp, EndedAt: stamp, RawOutput: rawOutput, Validation: promptexec.NewValidation(status, "json_schema", generationDefinitionForPrompt(req.PromptID).GeneratedTextSchemaID+".generated_text.schema.json", 0, nil)}
 	if complete != nil {
 		complete(execution)
 	}
diff --git a/internal/promptdebug/debug_writer_test.go b/internal/promptdebug/debug_writer_test.go
index eb2f3eb..54b86e7 100644
--- a/internal/promptdebug/debug_writer_test.go
+++ b/internal/promptdebug/debug_writer_test.go
@@ -349,7 +349,7 @@ func promptDebugExecutionFixture() promptexec.Execution {
 		InputHashes: map[string]string{"data_package": "input-hash"}, ProfileID: "local", BackendID: "local", ModelName: "weather-model",
 		GeneratedHash: "generated-hash", Usage: promptexec.TokenUsage{PromptTokens: 10, CompletionTokens: 5, TotalTokens: 15},
 		StartedAt: startedAt, EndedAt: startedAt.Add(time.Second), Duration: time.Second,
-		Validation: promptexec.NewValidation(promptexec.ValidationPassed, "strict", "schemas/daily.json", []string{"validation details"}),
+		Validation: promptexec.NewValidation(promptexec.ValidationPassed, "strict", "schemas/daily.json", 0, []string{"validation details"}),
 		RawOutput:  []byte("Generated forecast prose."),
 		Debug:      &promptexec.ExecutionDebug{ValidationDiagnostics: []string{"validation details"}},
 	}
diff --git a/internal/promptexec/copy.go b/internal/promptexec/copy.go
index 8a05611..9fe3ea0 100644
--- a/internal/promptexec/copy.go
+++ b/internal/promptexec/copy.go
@@ -78,3 +78,15 @@ func boundText(value string, limit int) string {
 	}
 	return value
 }
+
+func boundCodePoints(value string, limit int) string {
+	if limit <= 0 || value == "" {
+		return ""
+	}
+	value = strings.ToValidUTF8(value, "�")
+	runes := []rune(value)
+	if len(runes) <= limit {
+		return value
+	}
+	return string(runes[:limit])
+}
diff --git a/internal/promptexec/promptexec.go b/internal/promptexec/promptexec.go
index c5a1f29..e47507b 100644
--- a/internal/promptexec/promptexec.go
+++ b/internal/promptexec/promptexec.go
@@ -51,6 +51,7 @@ type OutputContract struct {
 	Format         string
 	ValidationMode string
 	SchemaPath     string
+	RepairAttempts int
 }
 
 // ProfileInspection describes the safe, selected execution identity for one profile.
@@ -141,19 +142,21 @@ type TokenUsage struct {
 
 // Validation records a completed output validation check.
 type Validation struct {
-	Status      ValidationStatus
-	Mode        string
-	SchemaPath  string
-	Diagnostics []string
+	Status         ValidationStatus
+	Mode           string
+	SchemaPath     string
+	RepairAttempts int
+	Diagnostics    []string
 }
 
 // NewValidation returns a completed validation value with bounded diagnostics.
-func NewValidation(status ValidationStatus, mode string, schemaPath string, diagnostics []string) Validation {
+func NewValidation(status ValidationStatus, mode string, schemaPath string, repairAttempts int, diagnostics []string) Validation {
 	return Validation{
-		Status:      status,
-		Mode:        mode,
-		SchemaPath:  schemaPath,
-		Diagnostics: boundDiagnostics(diagnostics),
+		Status:         status,
+		Mode:           mode,
+		SchemaPath:     schemaPath,
+		RepairAttempts: repairAttempts,
+		Diagnostics:    boundDiagnostics(diagnostics),
 	}
 }
 
@@ -235,6 +238,86 @@ func (e *Error) Category() ErrorCategory {
 	return e.category
 }
 
+// GenerationError retains provider failure details for programmatic handling
+// without exposing them through routine formatting or serialization.
+type GenerationError struct {
+	statusCode      int
+	providerCode    string
+	providerType    string
+	providerMessage string
+	err             *Error
+}
+
+// NewGenerationError returns a classified generation failure with bounded
+// provider details. The dependency cause remains reachable through err only.
+func NewGenerationError(statusCode int, providerCode string, providerType string, providerMessage string, cause error) *GenerationError {
+	return &GenerationError{
+		statusCode:      statusCode,
+		providerCode:    boundCodePoints(providerCode, 256),
+		providerType:    boundCodePoints(providerType, 256),
+		providerMessage: boundCodePoints(providerMessage, 4096),
+		err:             NewError(Generation, "provider generation failed", cause),
+	}
+}
+
+// StatusCode returns the provider HTTP status when one was available.
+func (e *GenerationError) StatusCode() int {
+	if e == nil {
+		return 0
+	}
+	return e.statusCode
+}
+
+// ProviderCode returns the bounded provider error code.
+func (e *GenerationError) ProviderCode() string {
+	if e == nil {
+		return ""
+	}
+	return e.providerCode
+}
+
+// ProviderType returns the bounded provider error type.
+func (e *GenerationError) ProviderType() string {
+	if e == nil {
+		return ""
+	}
+	return e.providerType
+}
+
+// ProviderMessage returns the bounded provider error message.
+func (e *GenerationError) ProviderMessage() string {
+	if e == nil {
+		return ""
+	}
+	return e.providerMessage
+}
+
+// Category returns Generation for every generation failure.
+func (e *GenerationError) Category() ErrorCategory { return Generation }
+
+// Error intentionally excludes provider details from ordinary error text.
+func (e *GenerationError) Error() string {
+	if e == nil {
+		return ""
+	}
+	message := NewError(Generation, "provider generation failed", nil).Error()
+	if e.statusCode == 0 {
+		return message
+	}
+	return fmt.Sprintf("%s (HTTP %d)", message, e.statusCode)
+}
+
+// GoString keeps %#v formatting as safe as ordinary error formatting.
+func (e *GenerationError) GoString() string { return e.Error() }
+
+// Unwrap preserves the project-owned classified error and its hidden cause.
+func (e *GenerationError) Unwrap() error {
+	if e == nil {
+		return nil
+	}
+	return e.err
+}
+
 // CapacityError adds the safe backend identity to a capacity failure.
 type CapacityError struct {
 	BackendID string
diff --git a/internal/promptexec/promptexec_test.go b/internal/promptexec/promptexec_test.go
index d13361d..fdfd917 100644
--- a/internal/promptexec/promptexec_test.go
+++ b/internal/promptexec/promptexec_test.go
@@ -3,6 +3,7 @@ package promptexec
 import (
 	"context"
 	"errors"
+	"fmt"
 	"strings"
 	"testing"
 	"unicode/utf8"
@@ -172,8 +173,8 @@ func TestBoundDiagnosticAndErrorText(t *testing.T) {
 	if bounded[0] != "a�b" {
 		t.Fatalf("invalid UTF-8 diagnostic = %q, want replacement", bounded[0])
 	}
-	validation := NewValidation(ValidationFailed, "json_schema", "daily.schema.json", values)
-	if len(validation.Diagnostics) != maxValidationDiagnostics || validation.Diagnostics[0] != "a�b" {
+	validation := NewValidation(ValidationFailed, "json_schema", "daily.schema.json", 2, values)
+	if validation.RepairAttempts != 2 || len(validation.Diagnostics) != maxValidationDiagnostics || validation.Diagnostics[0] != "a�b" {
 		t.Fatalf("validation = %#v, want bounded diagnostics", validation)
 	}
 
@@ -187,8 +188,53 @@ func TestBoundDiagnosticAndErrorText(t *testing.T) {
 	}
 }
 
+func TestGenerationErrorKeepsProviderDetailsOutOfRoutineFormatting(t *testing.T) {
+	cause := errors.New("provider response must stay hidden")
+	error := NewGenerationError(
+		429,
+		string([]byte{'c', 0xff})+strings.Repeat("界", 300),
+		strings.Repeat("type", 100),
+		string([]byte{'m', 0xff})+strings.Repeat("界", 4_200),
+		cause,
+	)
+	if error.StatusCode() != 429 || error.Category() != Generation || CategoryOf(error) != Generation {
+		t.Fatalf("generation error identity = %#v", error)
+	}
+	if utf8.RuneCountInString(error.ProviderCode()) != 256 || utf8.RuneCountInString(error.ProviderType()) != 256 || utf8.RuneCountInString(error.ProviderMessage()) != 4096 {
+		t.Fatalf("provider detail bounds = %d/%d/%d", utf8.RuneCountInString(error.ProviderCode()), utf8.RuneCountInString(error.ProviderType()), utf8.RuneCountInString(error.ProviderMessage()))
+	}
+	if !utf8.ValidString(error.ProviderCode()) || !utf8.ValidString(error.ProviderType()) || !utf8.ValidString(error.ProviderMessage()) {
+		t.Fatalf("provider details are not valid UTF-8: %#v", error)
+	}
+	if !errors.Is(error, cause) {
+		t.Fatal("errors.Is() = false, want preserved dependency cause")
+	}
+	var owned *Error
+	if !errors.As(error, &owned) || owned.Category() != Generation {
+		t.Fatalf("errors.As(*Error) = %#v, want project-owned generation error", owned)
+	}
+	want := "generation: provider generation failed (HTTP 429)"
+	if error.Error() != want || fmt.Sprintf("%#v", error) != want {
+		t.Fatalf("ordinary formatting = %q / %#v, want %q", error.Error(), error, want)
+	}
+	for _, private := range []string{cause.Error(), error.ProviderCode(), error.ProviderType(), error.ProviderMessage()} {
+		if strings.Contains(error.Error(), private) || strings.Contains(fmt.Sprintf("%#v", error), private) {
+			t.Fatalf("generation error leaks provider detail %q", private)
+		}
+	}
+
+	statusOnly := NewGenerationError(503, "", "", "", nil)
+	if statusOnly.Error() != "generation: provider generation failed (HTTP 503)" {
+		t.Fatalf("status-only error = %q", statusOnly)
+	}
+	var nilError *GenerationError
+	if nilError.StatusCode() != 0 || nilError.ProviderCode() != "" || nilError.ProviderType() != "" || nilError.ProviderMessage() != "" || nilError.Category() != Generation || nilError.Error() != "" || nilError.GoString() != "" || nilError.Unwrap() != nil {
+		t.Fatalf("nil generation error = %#v", nilError)
+	}
+}
+
 func TestContractCopiesMutableValues(t *testing.T) {
-	preparation := Preparation{InputHashes: map[string]string{"data_package": "input-hash"}}
+	preparation := Preparation{InputHashes: map[string]string{"data_package": "input-hash"}, Output: OutputContract{RepairAttempts: 3}}
 	preparationDebug := &PreparationDebug{
 		RenderedMessages: []RenderedMessage{{Role: "user", Content: "rendered input"}},
 		StructuredSchema: []byte("schema body"),
@@ -196,7 +242,7 @@ func TestContractCopiesMutableValues(t *testing.T) {
 	}
 	execution := Execution{
 		InputHashes: map[string]string{"data_package": "input-hash"},
-		Validation:  Validation{Diagnostics: []string{"validation detail"}},
+		Validation:  Validation{RepairAttempts: 2, Diagnostics: []string{"validation detail"}},
 		RawOutput:   []byte("generated output"),
 		Debug: &ExecutionDebug{
 			RawOutput:             []byte("provider output"),
@@ -217,13 +263,13 @@ func TestContractCopiesMutableValues(t *testing.T) {
 	execution.Debug.RawOutput[0] = 'x'
 	execution.Debug.ValidationDiagnostics[0] = "changed"
 
-	if preparationCopy.InputHashes["data_package"] != "input-hash" {
+	if preparationCopy.InputHashes["data_package"] != "input-hash" || preparationCopy.Output.RepairAttempts != 3 {
 		t.Fatalf("preparation copy = %#v", preparationCopy)
 	}
 	if debugCopy.RenderedMessages[0].Content != "rendered input" || string(debugCopy.StructuredSchema) != "schema body" || string(debugCopy.ParametersJSON) != `{"temperature":0.2}` {
 		t.Fatalf("preparation debug copy = %#v", debugCopy)
 	}
-	if executionCopy.InputHashes["data_package"] != "input-hash" || executionCopy.Validation.Diagnostics[0] != "validation detail" || string(executionCopy.RawOutput) != "generated output" || string(executionCopy.Debug.RawOutput) != "provider output" || executionCopy.Debug.ValidationDiagnostics[0] != "detailed validation" {
+	if executionCopy.InputHashes["data_package"] != "input-hash" || executionCopy.Validation.RepairAttempts != 2 || executionCopy.Validation.Diagnostics[0] != "validation detail" || string(executionCopy.RawOutput) != "generated output" || string(executionCopy.Debug.RawOutput) != "provider output" || executionCopy.Debug.ValidationDiagnostics[0] != "detailed validation" {
 		t.Fatalf("execution copy = %#v", executionCopy)
 	}
 }