Mark chunk plan implementation complete

docs/internal/diagnostics.md

@@ -32,7 +32,10 @@ digests, requested module, lookup decision, materialization action, validation
 decision, and publication decision. Its closed decision values make failures
 and recoverable invalid records inspectable without serializing plan ranges,
 annotations, source content, reference content, prompts, model responses, or
-raw invalid-file bytes.
+raw invalid-file bytes. Lookup reasons are derived only from the lookup status:
+`stored chunk plan is valid`, `chunk plan not found`, `stored chunk plan is
+invalid`, or `chunk plan lookup skipped`. Store-provided reasons and malformed
+record details never enter this artifact.
 
 JSON methods indent their payload and append a newline. All artifact writes use
 a temporary file in the target directory, apply the requested permissions, and

docs/internal/modules.md

@@ -71,7 +71,8 @@ Chunkers implement `contracts.Chunker.Plan`. A plan identifies ordered source
 unit ranges and may carry optional namespaced JSON annotations; it does not
 contain materialized chunk content. The framework canonicalizes annotations,
 validates ranges against the current source, and materializes chunk IDs,
-indexes, references, content, units, and generic metadata. Annotation
+indexes, references, content, units, and generic metadata. Materialized source
+unit metadata is independently owned. Annotation
 namespaces remain optional data: generic framework code and downstream modules
 must not require D&D scene annotations or import `dnd/scenes`.
 

docs/internal/overview.md

@@ -34,7 +34,7 @@ normalize continuations that may overlap across lanes.
 | `internal/core/artifacts` | Run-manifest and provenance models. |
 | `internal/core/config` | Defaults, YAML parsing, environment overrides, validation, redaction, and effective pipeline resolution. |
 | `internal/core/diagnostics` | Scoped run directories, diagnostics writers, atomic writes, and retention decisions. |
-| `internal/core/source` | Generic source documents, units, chunks, canonical references, lookup, validation, and deterministic source digests. |
+| `internal/core/source` | Generic source documents, units, chunks, canonical references, validation, deterministic source digests, and independent metadata materialization. |
 | `internal/core/workspace` | Effective workspace settings, confined paths and writes, and checkpoint identity and manifest models. |
 
 ## Framework Packages

docs/internal/pipeline.md

@@ -214,7 +214,10 @@ Plan canonicalization requires canonical JSON annotations, a matching source
 digest, at least one range, existing ordered boundaries, and increasing range
 starts. Ranges may overlap or leave gaps; a chunker may impose stricter policy.
 Materialization deterministically reconstructs each range from the current
-source document and copies annotations without interpreting their namespaces.
+source document, deep-clones JSON-shaped source-unit metadata, and copies
+annotations without interpreting their namespaces. Materialized chunks and
+separate materializations do not share mutable unit metadata; unsupported or
+cyclic metadata fails materialization with context.
 
 Before lane execution, generic chunk validation checks the materialized chunks'
 identities, order, source references, content, media type, units, and metadata.

docs/operations.md

@@ -97,6 +97,11 @@ an `auto` run regenerates and atomically replaces it only after validation
 succeeds. Delete an exact cache root or digest directory only when regeneration
 cost is acceptable.
 
+The configured root is the cache trust boundary. An operator-supplied root path
+may itself resolve through a symlink, but cache-owned digest directories and
+plan files must be real directory and regular-file entries. Links or other
+unexpected entry types are rejected rather than followed.
+
 Publication uses atomic replacement. Concurrent readers observe a complete old
 or new plan, and concurrent writers leave one complete valid winner; there is
 no history, lock protocol, or rollback facility. Do not share a cache root

docs/roadmap/adr0005.md

@@ -1,9 +1,8 @@
 # ADR-0005 Feature Roadmap
 
-This roadmap defines the intended end state for
-[ADR-0005](../adr/0005-cache-canonical-chunk-plans-by-source.md). The feature
-is not implemented. The ordered coding work belongs in the
-[implementation plan](implementation.md).
+This roadmap records the implemented target state for
+[ADR-0005](../adr/0005-cache-canonical-chunk-plans-by-source.md). The
+[implementation record](implementation.md) preserves the completed work.
 
 ## Intent
 
@@ -156,11 +155,11 @@ This feature does not provide:
 
 ## Completion Outcomes
 
-The feature is complete when independent runs over the same canonical source
+**Achieved.** Independent runs over the same canonical source
 reuse byte-stable materialized chunks across pipeline, lane, reference,
 chunk-module, and LLM configuration changes; bypass and refresh obey their
 documented state semantics; provenance identifies the effective producer;
 legacy chunk checkpoints cannot compete with plan reuse; and all focused,
-integration, compatibility, CLI, and repository-wide validation passes. The
+integration, compatibility, CLI, and repository-wide validation pass. The
 configuration and operations references must also document both the per-user
 default and the recommended system-wide Linux setting.

docs/roadmap/implementation.md

@@ -4,11 +4,9 @@ This document records the implementation of the target state in
 [ADR-0005 Feature Roadmap](adr0005.md), governed by
 [ADR-0005](../adr/0005-cache-canonical-chunk-plans-by-source.md).
 
-Stages 1 through 8 summarize the completed initial implementation. Stages 9
-through 12 track pending remediation identified by the post-implementation
-review. Current behavior is documented in the canonical references linked from
-[Development](../development.md); those references must not describe the Stages
-9 through 12 target state until the corresponding stage is complete.
+All stages are complete. This document remains a concise historical
+implementation record. Current behavior is documented in the canonical
+references linked from [Development](../development.md).
 
 ## Execution Rules
 
@@ -351,7 +349,7 @@ feature and its per-user and system-wide deployment guidance.
 
 ## Stage 9: Redact invalid cache-record diagnostics
 
-**Status:** Pending
+**Status:** Complete
 
 ### Objective
 
@@ -408,7 +406,7 @@ remain correctly classified, and all focused and repository-wide checks pass.
 
 ## Stage 10: Enforce rooted chunk-plan filesystem access
 
-**Status:** Pending
+**Status:** Complete
 
 ### Objective
 
@@ -469,7 +467,7 @@ concurrency tests and the race detector pass, and the repository is green.
 
 ## Stage 11: Deep-clone source metadata during materialization
 
-**Status:** Pending
+**Status:** Complete
 
 ### Objective
 
@@ -526,7 +524,7 @@ current materialized bytes remain stable; and all checks pass.
 
 ## Stage 12: Finalize remediation documentation and roadmap status
 
-**Status:** Pending
+**Status:** Complete
 
 ### Objective
 

internal/cli/chunk_cache_test.go

@@ -255,6 +255,22 @@ func TestRunRecordsExplicitChunkCacheOverrideAndEffectiveMode(t *testing.T) {
 	}
 }
 
+func TestRunChunkPlanDiagnosticsRedactStoreDecisionReason(t *testing.T) {
+	diagnosticsDir := t.TempDir()
+	configPath := writeTestConfig(t, cacheTestConfig("auto", t.TempDir(), diagnosticsDir))
+	factory := &recordingChunkPlanFactory{store: &recordingChunkPlanStore{
+		decision: pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanInvalid, Reason: "SENTINEL_INVALID_RECORD_CONTENT"},
+	}}
+	code, stderr := runCacheCommand(t, cacheRunArgs(t, configPath), cacheTestOptions(t, nil, factory))
+	if code != 0 || stderr != "" {
+		t.Fatalf("code=%d stderr=%q", code, stderr)
+	}
+	summary := string(readFile(t, filepath.Join(onlyChildDir(t, diagnosticsDir), diagnostics.ArtifactChunkPlan)))
+	if strings.Contains(summary, "SENTINEL_INVALID_RECORD_CONTENT") || !strings.Contains(summary, `"lookup_reason": "stored chunk plan is invalid"`) {
+		t.Fatalf("chunk plan diagnostic = %s", summary)
+	}
+}
+
 func TestDefaultAutoReusesPlanAcrossIndependentInvocations(t *testing.T) {
 	cacheBase := filepath.Join(t.TempDir(), "cache")
 	workspaceDir := filepath.Join(t.TempDir(), "workspace")

internal/core/source/chunk_plan.go

@@ -162,7 +162,10 @@ func MaterializeChunkPlan(doc *SourceDocument, plan ChunkPlan) ([]Chunk, error)
 	for index, chunkRange := range plan.Ranges {
 		start, _ := UnitIndex(doc, chunkRange.StartUnitID)
 		end, _ := UnitIndex(doc, chunkRange.EndUnitID)
-		units := cloneSourceUnits(doc.Units[start : end+1])
+		units, err := cloneSourceUnits(doc.Units[start : end+1])
+		if err != nil {
+			return nil, fmt.Errorf("clone chunk plan range[%d] units: %w", index, err)
+		}
 		content, err := json.Marshal(struct {
 			Units []SourceUnit `json:"units"`
 		}{Units: units})
@@ -189,52 +192,18 @@ func MaterializeChunkPlan(doc *SourceDocument, plan ChunkPlan) ([]Chunk, error)
 	return chunks, nil
 }
 
-func cloneSourceUnits(units []SourceUnit) []SourceUnit {
+func cloneSourceUnits(units []SourceUnit) ([]SourceUnit, error) {
 	if len(units) == 0 {
-		return nil
+		return nil, nil
 	}
 	cloned := make([]SourceUnit, len(units))
 	for i, unit := range units {
 		cloned[i] = unit
-		cloned[i].Metadata = cloneJSONMap(unit.Metadata)
-	}
-	return cloned
-}
-
-func cloneJSONMap(values map[string]any) map[string]any {
-	if len(values) == 0 {
-		return nil
-	}
-	cloned := make(map[string]any, len(values))
-	for key, value := range values {
-		cloned[key] = cloneJSONValue(value)
-	}
-	return cloned
-}
-
-func cloneJSONValue(value any) any {
-	switch typed := value.(type) {
-	case map[string]any:
-		return cloneJSONMap(typed)
-	case []any:
-		cloned := make([]any, len(typed))
-		for i := range typed {
-			cloned[i] = cloneJSONValue(typed[i])
-		}
-		return cloned
-	case json.RawMessage:
-		return append(json.RawMessage(nil), typed...)
-	case []byte:
-		return append([]byte(nil), typed...)
-	case []string:
-		return append([]string(nil), typed...)
-	case map[string]string:
-		cloned := make(map[string]string, len(typed))
-		for key, item := range typed {
-			cloned[key] = item
-		}
-		return cloned
-	default:
-		return value
+		metadata, err := CloneMetadata(unit.Metadata)
+		if err != nil {
+			return nil, fmt.Errorf("source unit[%d] metadata: %w", i, err)
 		}
+		cloned[i].Metadata = metadata
+	}
+	return cloned, nil
 }

internal/core/source/chunk_plan_test.go

@@ -3,11 +3,16 @@ package source
 import (
 	"bytes"
 	"encoding/json"
+	"math"
 	"reflect"
 	"strings"
 	"testing"
 )
 
+type typedMetadataMap map[string]any
+type typedMetadataSlice []typedMetadataMap
+type typedMetadataArray [2]any
+
 func TestCanonicalizeChunkAnnotations(t *testing.T) {
 	original := ChunkAnnotations{
 		"domain/items": json.RawMessage(` { "z": [3, 2, 1], "a": 1.0 } `),
@@ -218,6 +223,87 @@ func TestMaterializeChunkPlanDeepClonesUnitMetadata(t *testing.T) {
 	}
 }
 
+func TestMaterializeChunkPlanClonesConcreteJSONMetadata(t *testing.T) {
+	doc := planDocument()
+	doc.Units[0].Metadata = map[string]any{
+		"typed_map":   typedMetadataMap{"bytes": []byte("map")},
+		"typed_slice": typedMetadataSlice{{"raw": json.RawMessage(`{"slice":true}`)}},
+		"typed_array": typedMetadataArray{map[string]any{"bytes": []byte("array")}, []any{json.RawMessage(`{"array":true}`)}},
+		"interface":   any(typedMetadataMap{"bytes": []byte("interface")}),
+		"raw":         json.RawMessage(`{"raw":true}`),
+		"bytes":       []byte("bytes"),
+	}
+
+	chunks, err := MaterializeChunkPlan(doc, validChunkPlan(doc))
+	if err != nil {
+		t.Fatal(err)
+	}
+	again, err := MaterializeChunkPlan(doc, validChunkPlan(doc))
+	if err != nil {
+		t.Fatal(err)
+	}
+	metadata := chunks[0].Units[0].Metadata
+	metadata["typed_map"].(typedMetadataMap)["bytes"].([]byte)[0] = 'M'
+	metadata["typed_slice"].(typedMetadataSlice)[0]["raw"].(json.RawMessage)[0] = '['
+	metadata["typed_array"].(typedMetadataArray)[0].(map[string]any)["bytes"].([]byte)[0] = 'A'
+	metadata["typed_array"].(typedMetadataArray)[1].([]any)[0].(json.RawMessage)[0] = '['
+	metadata["interface"].(typedMetadataMap)["bytes"].([]byte)[0] = 'I'
+	metadata["raw"].(json.RawMessage)[0] = '['
+	metadata["bytes"].([]byte)[0] = 'B'
+
+	for name, candidate := range map[string]map[string]any{
+		"source": doc.Units[0].Metadata,
+		"again":  again[0].Units[0].Metadata,
+	} {
+		if got := string(candidate["typed_map"].(typedMetadataMap)["bytes"].([]byte)); got != "map" {
+			t.Fatalf("%s typed map bytes = %q, want map", name, got)
+		}
+		if got := string(candidate["typed_slice"].(typedMetadataSlice)[0]["raw"].(json.RawMessage)); got != `{"slice":true}` {
+			t.Fatalf("%s typed slice raw = %q", name, got)
+		}
+		array := candidate["typed_array"].(typedMetadataArray)
+		if got := string(array[0].(map[string]any)["bytes"].([]byte)); got != "array" || string(array[1].([]any)[0].(json.RawMessage)) != `{"array":true}` {
+			t.Fatalf("%s typed array = %#v", name, array)
+		}
+		if got := string(candidate["interface"].(typedMetadataMap)["bytes"].([]byte)); got != "interface" {
+			t.Fatalf("%s interface bytes = %q, want interface", name, got)
+		}
+		if got := string(candidate["raw"].(json.RawMessage)); got != `{"raw":true}` {
+			t.Fatalf("%s raw = %q", name, got)
+		}
+		if got := string(candidate["bytes"].([]byte)); got != "bytes" {
+			t.Fatalf("%s bytes = %q, want bytes", name, got)
+		}
+	}
+}
+
+func TestMaterializeChunkPlanRejectsInvalidMetadata(t *testing.T) {
+	cyclic := make(map[string]any)
+	cyclic["self"] = cyclic
+	for _, tc := range []struct {
+		name  string
+		value any
+		want  string
+	}{
+		{name: "cycle", value: cyclic, want: "metadata.cycle.self contains a cycle"},
+		{name: "unsupported", value: func() {}, want: "metadata.unsupported has unsupported type func()"},
+		{name: "nonfinite", value: math.NaN(), want: "metadata.nonfinite has a non-finite number"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			doc := planDocument()
+			doc.Units[0].Metadata = map[string]any{tc.name: tc.value}
+			_, first := MaterializeChunkPlan(doc, validChunkPlan(doc))
+			_, second := MaterializeChunkPlan(doc, validChunkPlan(doc))
+			if first == nil || !strings.Contains(first.Error(), "clone chunk plan range[0] units: source unit[0] metadata: "+tc.want) {
+				t.Fatalf("first MaterializeChunkPlan() error = %v, want %q", first, tc.want)
+			}
+			if second == nil || second.Error() != first.Error() {
+				t.Fatalf("MaterializeChunkPlan() errors = %v and %v, want deterministic error", first, second)
+			}
+		})
+	}
+}
+
 func planDocument() *SourceDocument {
 	doc := &SourceDocument{ID: "source-plan", Kind: "test", Format: "application/test", Digest: "sha256:source-plan"}
 	for _, id := range []int{10, 20, 30, 40, 50} {

internal/core/source/metadata.go

@@ -0,0 +1,119 @@
+package source
+
+import (
+	"fmt"
+	"math"
+	"reflect"
+	"sort"
+)
+
+// CloneMetadata returns an independently owned copy of JSON-shaped metadata.
+// It preserves concrete map, slice, and array types while rejecting values that
+// cannot be safely represented as JSON-shaped metadata.
+func CloneMetadata(metadata map[string]any) (map[string]any, error) {
+	if len(metadata) == 0 {
+		return nil, nil
+	}
+	cloned, err := cloneMetadataValue(reflect.ValueOf(metadata), "metadata", make(map[metadataVisit]struct{}))
+	if err != nil {
+		return nil, err
+	}
+	return cloned.Interface().(map[string]any), nil
+}
+
+type metadataVisit struct {
+	typ reflect.Type
+	ptr uintptr
+}
+
+func cloneMetadataValue(value reflect.Value, location string, active map[metadataVisit]struct{}) (reflect.Value, error) {
+	if !value.IsValid() {
+		return value, nil
+	}
+
+	switch value.Kind() {
+	case reflect.Interface:
+		if value.IsNil() {
+			return reflect.Zero(value.Type()), nil
+		}
+		cloned, err := cloneMetadataValue(value.Elem(), location, active)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		result := reflect.New(value.Type()).Elem()
+		result.Set(cloned)
+		return result, nil
+	case reflect.Map:
+		if value.IsNil() {
+			return reflect.Zero(value.Type()), nil
+		}
+		if value.Type().Key().Kind() != reflect.String {
+			return reflect.Value{}, fmt.Errorf("%s has unsupported map key type %s", location, value.Type().Key())
+		}
+		leave, err := enterMetadataValue(value, active, location)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		defer leave()
+
+		keys := value.MapKeys()
+		sort.Slice(keys, func(i, j int) bool { return keys[i].String() < keys[j].String() })
+		result := reflect.MakeMapWithSize(value.Type(), value.Len())
+		for _, key := range keys {
+			cloned, err := cloneMetadataValue(value.MapIndex(key), location+"."+key.String(), active)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			result.SetMapIndex(key, cloned)
+		}
+		return result, nil
+	case reflect.Slice:
+		if value.IsNil() {
+			return reflect.Zero(value.Type()), nil
+		}
+		leave, err := enterMetadataValue(value, active, location)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+		defer leave()
+
+		result := reflect.MakeSlice(value.Type(), value.Len(), value.Len())
+		for i := 0; i < value.Len(); i++ {
+			cloned, err := cloneMetadataValue(value.Index(i), fmt.Sprintf("%s[%d]", location, i), active)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			result.Index(i).Set(cloned)
+		}
+		return result, nil
+	case reflect.Array:
+		result := reflect.New(value.Type()).Elem()
+		for i := 0; i < value.Len(); i++ {
+			cloned, err := cloneMetadataValue(value.Index(i), fmt.Sprintf("%s[%d]", location, i), active)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			result.Index(i).Set(cloned)
+		}
+		return result, nil
+	case reflect.Float32, reflect.Float64:
+		if math.IsNaN(value.Float()) || math.IsInf(value.Float(), 0) {
+			return reflect.Value{}, fmt.Errorf("%s has a non-finite number", location)
+		}
+		return value, nil
+	case reflect.Bool, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
+		reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.String:
+		return value, nil
+	default:
+		return reflect.Value{}, fmt.Errorf("%s has unsupported type %s", location, value.Type())
+	}
+}
+
+func enterMetadataValue(value reflect.Value, active map[metadataVisit]struct{}, location string) (func(), error) {
+	visit := metadataVisit{typ: value.Type(), ptr: value.Pointer()}
+	if _, exists := active[visit]; exists {
+		return nil, fmt.Errorf("%s contains a cycle", location)
+	}
+	active[visit] = struct{}{}
+	return func() { delete(active, visit) }, nil
+}

internal/framework/chunkplan/store.go

@@ -2,8 +2,10 @@ package chunkplan
 
 import (
 	"bytes"
+	"crypto/rand"
 	"encoding/hex"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"os"
@@ -16,9 +18,11 @@ import (
 
 const SchemaVersion = pipeline.ChunkPlanSchemaVersion
 
+const planFileName = "plan.json"
+
 type filesystemStore struct {
 	root  string
-	write func(string, []byte) error
+	write func(*os.Root, string, []byte) error
 }
 
 func NewFilesystemStore(root string) (pipeline.ChunkPlanStore, error) {
@@ -33,14 +37,46 @@ func NewFilesystemStore(root string) (pipeline.ChunkPlanStore, error) {
 }
 
 func (s *filesystemStore) Load(sourceDigest string) (pipeline.ChunkPlanRecord, pipeline.ChunkPlanDecision, error) {
-	target, err := s.planPath(sourceDigest)
+	digestDir, err := digestPathSegment(sourceDigest)
 	if err != nil {
 		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{}, err
 	}
-	data, err := os.ReadFile(target)
+	root, err := s.openRoot(false)
 	if err != nil {
 		if os.IsNotExist(err) {
-			return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanMissing, Reason: "chunk plan not found"}, nil
+			return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanMissing, Reason: lookupReason(pipeline.ChunkPlanMissing)}, nil
+		}
+		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{}, fmt.Errorf("open chunk plan root: %w", err)
+	}
+	defer root.Close()
+
+	state, err := inspectDirectory(root, digestDir)
+	if err != nil {
+		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{}, fmt.Errorf("inspect chunk plan directory: %w", err)
+	}
+	if state == entryMissing {
+		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanMissing, Reason: lookupReason(pipeline.ChunkPlanMissing)}, nil
+	}
+	if state == entryRejected {
+		return invalidDecision()
+	}
+
+	target := planPath(digestDir)
+	state, err = inspectPlan(root, target)
+	if err != nil {
+		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{}, fmt.Errorf("inspect chunk plan file: %w", err)
+	}
+	if state == entryMissing {
+		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanMissing, Reason: lookupReason(pipeline.ChunkPlanMissing)}, nil
+	}
+	if state == entryRejected {
+		return invalidDecision()
+	}
+
+	data, err := root.ReadFile(target)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanMissing, Reason: lookupReason(pipeline.ChunkPlanMissing)}, nil
 		}
 		return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{}, fmt.Errorf("read chunk plan: %w", err)
 	}
@@ -50,26 +86,23 @@ func (s *filesystemStore) Load(sourceDigest string) (pipeline.ChunkPlanRecord, p
 	decoder.DisallowUnknownFields()
 	decoder.UseNumber()
 	if err := decoder.Decode(&record); err != nil {
-		return invalidDecision(fmt.Sprintf("decode stored chunk plan: %v", err))
+		return invalidDecision()
 	}
 	var trailing any
 	if err := decoder.Decode(&trailing); err != io.EOF {
-		if err == nil {
-			return invalidDecision("stored chunk plan contains trailing JSON")
-		}
-		return invalidDecision(fmt.Sprintf("decode stored chunk plan trailer: %v", err))
+		return invalidDecision()
 	}
 	if err := validateRecord(record, sourceDigest); err != nil {
-		return invalidDecision(err.Error())
+		return invalidDecision()
 	}
-	return record, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanHit, Reason: "stored chunk plan is valid"}, nil
+	return record, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanHit, Reason: lookupReason(pipeline.ChunkPlanHit)}, nil
 }
 
 func (s *filesystemStore) Save(record pipeline.ChunkPlanRecord) error {
 	if err := validateRecord(record, record.SourceDigest); err != nil {
 		return fmt.Errorf("validate chunk plan record: %w", err)
 	}
-	target, err := s.planPath(record.SourceDigest)
+	digestDir, err := digestPathSegment(record.SourceDigest)
 	if err != nil {
 		return err
 	}
@@ -78,25 +111,134 @@ func (s *filesystemStore) Save(record pipeline.ChunkPlanRecord) error {
 		return fmt.Errorf("encode chunk plan record: %w", err)
 	}
 	data = append(data, '\n')
+	root, err := s.openRoot(true)
+	if err != nil {
+		return fmt.Errorf("open chunk plan root: %w", err)
+	}
+	defer root.Close()
+	if err := ensureDirectory(root, digestDir); err != nil {
+		return fmt.Errorf("prepare chunk plan directory: %w", err)
+	}
+	target := planPath(digestDir)
+	state, err := inspectPlan(root, target)
+	if err != nil {
+		return fmt.Errorf("inspect chunk plan file: %w", err)
+	}
+	if state == entryRejected {
+		return fmt.Errorf("chunk plan file has an unsupported type")
+	}
 	writer := s.write
 	if writer == nil {
 		writer = writeAtomic
 	}
-	if err := writer(target, data); err != nil {
+	if err := writer(root, target, data); err != nil {
 		return fmt.Errorf("write chunk plan: %w", err)
 	}
 	return nil
 }
 
-func (s *filesystemStore) planPath(sourceDigest string) (string, error) {
+func (s *filesystemStore) openRoot(create bool) (*os.Root, error) {
 	if s == nil || strings.TrimSpace(s.root) == "" {
-		return "", fmt.Errorf("chunk plan store must not be nil")
+		return nil, fmt.Errorf("chunk plan store must not be nil")
 	}
-	hexDigest, err := digestPathSegment(sourceDigest)
+	if create {
+		if err := os.MkdirAll(s.root, 0o700); err != nil {
+			return nil, err
+		}
+	}
+	root, err := os.OpenRoot(s.root)
 	if err != nil {
-		return "", err
+		return nil, err
 	}
-	return filepath.Join(s.root, hexDigest, "plan.json"), nil
+	if !create {
+		return root, nil
+	}
+	rootDirectory, err := root.Open(".")
+	if err != nil {
+		_ = root.Close()
+		return nil, err
+	}
+	defer rootDirectory.Close()
+	if err := rootDirectory.Chmod(0o700); err != nil {
+		_ = root.Close()
+		return nil, err
+	}
+	return root, nil
+}
+
+type entryState uint8
+
+const (
+	entryPresent entryState = iota
+	entryMissing
+	entryRejected
+)
+
+func inspectDirectory(root *os.Root, digestDir string) (entryState, error) {
+	info, err := root.Lstat(digestDir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return entryMissing, nil
+		}
+		return entryPresent, err
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.IsDir() {
+		return entryRejected, nil
+	}
+	return entryPresent, nil
+}
+
+func ensureDirectory(root *os.Root, digestDir string) error {
+	for {
+		state, err := inspectDirectory(root, digestDir)
+		if err != nil {
+			return err
+		}
+		switch state {
+		case entryRejected:
+			return fmt.Errorf("chunk plan directory has an unsupported type")
+		case entryMissing:
+			if err := root.Mkdir(digestDir, 0o700); err != nil && !errors.Is(err, os.ErrExist) {
+				return err
+			}
+			continue
+		}
+
+		directory, err := root.Open(digestDir)
+		if err != nil {
+			return err
+		}
+		info, statErr := directory.Stat()
+		if statErr == nil && !info.IsDir() {
+			statErr = fmt.Errorf("chunk plan directory has an unsupported type")
+		}
+		if statErr == nil {
+			statErr = directory.Chmod(0o700)
+		}
+		closeErr := directory.Close()
+		if statErr != nil {
+			return statErr
+		}
+		return closeErr
+	}
+}
+
+func inspectPlan(root *os.Root, target string) (entryState, error) {
+	info, err := root.Lstat(target)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return entryMissing, nil
+		}
+		return entryPresent, err
+	}
+	if info.Mode()&os.ModeSymlink != 0 || !info.Mode().IsRegular() {
+		return entryRejected, nil
+	}
+	return entryPresent, nil
+}
+
+func planPath(digestDir string) string {
+	return digestDir + "/" + planFileName
 }
 
 func digestPathSegment(digest string) (string, error) {
@@ -165,8 +307,21 @@ func validateRecord(record pipeline.ChunkPlanRecord, requestedDigest string) err
 	return nil
 }
 
-func invalidDecision(reason string) (pipeline.ChunkPlanRecord, pipeline.ChunkPlanDecision, error) {
-	return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanInvalid, Reason: reason}, nil
+func invalidDecision() (pipeline.ChunkPlanRecord, pipeline.ChunkPlanDecision, error) {
+	return pipeline.ChunkPlanRecord{}, pipeline.ChunkPlanDecision{Status: pipeline.ChunkPlanInvalid, Reason: lookupReason(pipeline.ChunkPlanInvalid)}, nil
+}
+
+func lookupReason(status pipeline.ChunkPlanStatus) string {
+	switch status {
+	case pipeline.ChunkPlanHit:
+		return "stored chunk plan is valid"
+	case pipeline.ChunkPlanMissing:
+		return "chunk plan not found"
+	case pipeline.ChunkPlanInvalid:
+		return "stored chunk plan is invalid"
+	default:
+		return "chunk plan lookup skipped"
+	}
 }
 
 type atomicWriteHooks struct {
@@ -174,33 +329,24 @@ type atomicWriteHooks struct {
 	BeforeRename     func() error
 }
 
-func writeAtomic(target string, data []byte) error {
-	return writeAtomicWithHooks(target, data, atomicWriteHooks{})
+func writeAtomic(root *os.Root, target string, data []byte) error {
+	return writeAtomicWithHooks(root, target, data, atomicWriteHooks{})
 }
 
-func writeAtomicWithHooks(target string, data []byte, hooks atomicWriteHooks) error {
-	dir := filepath.Dir(target)
-	if err := os.MkdirAll(dir, 0o700); err != nil {
-		return err
-	}
-	if err := os.Chmod(dir, 0o700); err != nil {
-		return err
-	}
-
+func writeAtomicWithHooks(root *os.Root, target string, data []byte, hooks atomicWriteHooks) error {
 	if hooks.BeforeCreateTemp != nil {
 		if err := hooks.BeforeCreateTemp(); err != nil {
 			return err
 		}
 	}
-	temp, err := os.CreateTemp(dir, ".plan.json.tmp-*")
+	temp, tempPath, err := createTemporaryFile(root, target)
 	if err != nil {
 		return err
 	}
-	tempPath := temp.Name()
 	removeTemp := true
 	defer func() {
 		if removeTemp {
-			_ = os.Remove(tempPath)
+			_ = root.Remove(tempPath)
 		}
 	}()
 	if err := temp.Chmod(0o600); err != nil {
@@ -223,9 +369,28 @@ func writeAtomicWithHooks(target string, data []byte, hooks atomicWriteHooks) er
 			return err
 		}
 	}
-	if err := os.Rename(tempPath, target); err != nil {
+	if err := root.Rename(tempPath, target); err != nil {
 		return err
 	}
 	removeTemp = false
 	return nil
 }
+
+func createTemporaryFile(root *os.Root, target string) (*os.File, string, error) {
+	for attempt := 0; attempt < 32; attempt++ {
+		var suffix [16]byte
+		if _, err := rand.Read(suffix[:]); err != nil {
+			return nil, "", err
+		}
+		path := strings.TrimSuffix(target, planFileName) + ".plan.json.tmp-" + hex.EncodeToString(suffix[:])
+		file, err := root.OpenFile(path, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
+		if errors.Is(err, os.ErrExist) {
+			continue
+		}
+		if err != nil {
+			return nil, "", err
+		}
+		return file, path, nil
+	}
+	return nil, "", fmt.Errorf("create unique temporary chunk plan file")
+}

internal/framework/chunkplan/store_test.go

@@ -84,19 +84,118 @@ func TestFilesystemStorePermissions(t *testing.T) {
 }
 
 func TestFilesystemStoreMissingAndOperationalErrors(t *testing.T) {
-	root := t.TempDir()
+	root := filepath.Join(t.TempDir(), "plans")
 	store := newStore(t, root)
 	_, decision, err := store.Load(testSourceDigest)
 	if err != nil || decision.Status != pipeline.ChunkPlanMissing {
 		t.Fatalf("missing decision=%#v error=%v", decision, err)
 	}
+	if _, err := os.Stat(root); !os.IsNotExist(err) {
+		t.Fatalf("Load() created missing root: %v", err)
+	}
 
 	target := filepath.Join(root, strings.TrimPrefix(testSourceDigest, "sha256:"), "plan.json")
 	if err := os.MkdirAll(target, 0o700); err != nil {
 		t.Fatal(err)
 	}
-	if _, _, err := store.Load(testSourceDigest); err == nil {
-		t.Fatal("Load(plan.json directory) error = nil")
+	_, decision, err = store.Load(testSourceDigest)
+	if err != nil || decision.Status != pipeline.ChunkPlanInvalid {
+		t.Fatalf("Load(plan.json directory) decision=%#v error=%v", decision, err)
+	}
+}
+
+func TestFilesystemStoreRejectsSymlinkedEntries(t *testing.T) {
+	tests := []struct {
+		name  string
+		setup func(t *testing.T, root, outside string)
+	}{
+		{
+			name: "digest directory",
+			setup: func(t *testing.T, root, outside string) {
+				t.Helper()
+				if err := os.MkdirAll(outside, 0o700); err != nil {
+					t.Fatal(err)
+				}
+				writeFile(t, filepath.Join(outside, "plan.json"), []byte("outside plan"), 0o640)
+				createSymlink(t, outside, filepath.Join(root, strings.TrimPrefix(testSourceDigest, "sha256:")))
+			},
+		},
+		{
+			name: "plan file",
+			setup: func(t *testing.T, root, outside string) {
+				t.Helper()
+				digestDir := filepath.Join(root, strings.TrimPrefix(testSourceDigest, "sha256:"))
+				if err := os.MkdirAll(digestDir, 0o700); err != nil {
+					t.Fatal(err)
+				}
+				writeFile(t, outside, []byte("outside plan"), 0o640)
+				createSymlink(t, outside, filepath.Join(digestDir, "plan.json"))
+			},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			root := filepath.Join(t.TempDir(), "plans")
+			if err := os.MkdirAll(root, 0o700); err != nil {
+				t.Fatal(err)
+			}
+			outside := filepath.Join(t.TempDir(), "outside")
+			tc.setup(t, root, outside)
+			before := readFile(t, outsidePlanPath(tc.name, outside))
+			beforeMode := fileMode(t, outsidePlanPath(tc.name, outside))
+
+			store := newStore(t, root)
+			_, decision, err := store.Load(testSourceDigest)
+			if err != nil || decision.Status != pipeline.ChunkPlanInvalid {
+				t.Fatalf("Load() decision=%#v error=%v", decision, err)
+			}
+			if err := store.Save(testRecord(t, 1)); err == nil {
+				t.Fatal("Save() error = nil")
+			}
+			outsidePlan := outsidePlanPath(tc.name, outside)
+			if got := readFile(t, outsidePlan); !bytes.Equal(got, before) {
+				t.Fatalf("outside content = %q, want %q", got, before)
+			}
+			if got := fileMode(t, outsidePlan); got != beforeMode {
+				t.Fatalf("outside mode = %04o, want %04o", got, beforeMode)
+			}
+		})
+	}
+}
+
+func TestFilesystemStoreRejectsUnexpectedEntryTypes(t *testing.T) {
+	tests := []struct {
+		name  string
+		setup func(t *testing.T, root string)
+	}{
+		{
+			name: "digest file",
+			setup: func(t *testing.T, root string) {
+				writeFile(t, filepath.Join(root, strings.TrimPrefix(testSourceDigest, "sha256:")), []byte("not a directory"), 0o600)
+			},
+		},
+		{
+			name: "plan directory",
+			setup: func(t *testing.T, root string) {
+				if err := os.MkdirAll(filepath.Join(root, strings.TrimPrefix(testSourceDigest, "sha256:"), "plan.json"), 0o700); err != nil {
+					t.Fatal(err)
+				}
+			},
+		},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			root := t.TempDir()
+			tc.setup(t, root)
+			store := newStore(t, root)
+			_, decision, err := store.Load(testSourceDigest)
+			if err != nil || decision.Status != pipeline.ChunkPlanInvalid {
+				t.Fatalf("Load() decision=%#v error=%v", decision, err)
+			}
+			if err := store.Save(testRecord(t, 1)); err == nil {
+				t.Fatal("Save() error = nil")
+			}
+		})
 	}
 }
 
@@ -122,14 +221,13 @@ func TestFilesystemStoreReportsInvalidRecordsAsRecoverable(t *testing.T) {
 	tests := []struct {
 		name   string
 		mutate func([]byte) []byte
-		want   string
 	}{
 		{name: "unknown field", mutate: func(data []byte) []byte {
-			return bytes.Replace(data, []byte(`{"schema_version"`), []byte(`{"unknown":true,"schema_version"`), 1)
-		}, want: "unknown"},
-		{name: "truncated JSON", mutate: func(data []byte) []byte { return data[:len(data)/2] }, want: "decode"},
-		{name: "schema mismatch", mutate: replaceJSON(`notarius.chunk-plan.v1`, `notarius.chunk-plan.v2`), want: "schema_version"},
-		{name: "source mismatch", mutate: replaceJSON(testSourceDigest, "sha256:"+strings.Repeat("b", 64)), want: "source_digest"},
+			return bytes.Replace(data, []byte(`{"schema_version"`), []byte(`{"SENTINEL_UNKNOWN_FIELD":true,"schema_version"`), 1)
+		}},
+		{name: "truncated JSON", mutate: func(data []byte) []byte { return data[:len(data)/2] }},
+		{name: "schema mismatch", mutate: replaceJSON(`notarius.chunk-plan.v1`, `SENTINEL_SCHEMA_VALUE`)},
+		{name: "source mismatch", mutate: replaceJSON(testSourceDigest, "sha256:"+strings.Repeat("b", 64))},
 		{name: "plan digest mismatch", mutate: func(data []byte) []byte {
 			prefix := []byte(`"plan_digest":"sha256:`)
 			index := bytes.Index(data, prefix)
@@ -137,14 +235,15 @@ func TestFilesystemStoreReportsInvalidRecordsAsRecoverable(t *testing.T) {
 				data[index+len(prefix)] = '0'
 			}
 			return data
-		}, want: "plan_digest"},
+		}},
 		{name: "noncanonical annotation", mutate: func(data []byte) []byte {
-			return bytes.Replace(data, []byte(`{"value":1}`), []byte(`{ "value": 1 }`), 1)
-		}, want: "canonical JSON"},
+			return bytes.Replace(data, []byte(`"test/value"`), []byte(`"SENTINEL_ANNOTATION_NAMESPACE"`), 1)
+		}},
 		{name: "bad boundary", mutate: func(data []byte) []byte {
 			return bytes.Replace(data, []byte(`"start_unit_id":1`), []byte(`"start_unit_id":0`), 1)
-		}, want: "boundaries must be positive"},
-		{name: "trailing JSON", mutate: func(data []byte) []byte { return append(data, []byte(` {}`)...) }, want: "trailing"},
+		}},
+		{name: "timestamp", mutate: replaceJSON(`2026-07-18T12:00:00Z`, `SENTINEL_TIMESTAMP`)},
+		{name: "trailing JSON", mutate: func(data []byte) []byte { return append(data, []byte(` {"SENTINEL_TRAILING":true}`)...) }},
 	}
 	for _, tc := range tests {
 		t.Run(tc.name, func(t *testing.T) {
@@ -163,9 +262,14 @@ func TestFilesystemStoreReportsInvalidRecordsAsRecoverable(t *testing.T) {
 				t.Fatal(err)
 			}
 			got, decision, err := store.Load(testSourceDigest)
-			if err != nil || decision.Status != pipeline.ChunkPlanInvalid || !reflect.DeepEqual(got, pipeline.ChunkPlanRecord{}) || !strings.Contains(decision.Reason, tc.want) {
+			if err != nil || decision.Status != pipeline.ChunkPlanInvalid || !reflect.DeepEqual(got, pipeline.ChunkPlanRecord{}) || decision.Reason != "stored chunk plan is invalid" {
 				t.Fatalf("record=%#v decision=%#v error=%v", got, decision, err)
 			}
+			for _, sentinel := range []string{"SENTINEL_UNKNOWN_FIELD", "SENTINEL_SCHEMA_VALUE", "SENTINEL_ANNOTATION_NAMESPACE", "SENTINEL_TIMESTAMP", "SENTINEL_TRAILING"} {
+				if strings.Contains(decision.Reason, sentinel) {
+					t.Fatalf("decision leaked %q: %#v", sentinel, decision)
+				}
+			}
 		})
 	}
 }
@@ -290,7 +394,9 @@ func TestFilesystemStoreInterruptedWritesPreservePreviousRecord(t *testing.T) {
 		{name: "before rename", hooks: atomicWriteHooks{BeforeRename: func() error { return errors.New("interrupted before rename") }}},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
-			store.write = func(target string, data []byte) error { return writeAtomicWithHooks(target, data, tc.hooks) }
+			store.write = func(root *os.Root, target string, data []byte) error {
+				return writeAtomicWithHooks(root, target, data, tc.hooks)
+			}
 			if err := store.Save(testRecord(t, 2)); err == nil {
 				t.Fatal("Save() error = nil")
 			}
@@ -358,3 +464,45 @@ func assertNoTemps(t *testing.T, dir string) {
 		}
 	}
 }
+
+func createSymlink(t *testing.T, target, link string) {
+	t.Helper()
+	if err := os.Symlink(target, link); err != nil {
+		t.Skipf("create symlink: %v", err)
+	}
+}
+
+func writeFile(t *testing.T, path string, data []byte, mode os.FileMode) {
+	t.Helper()
+	if err := os.WriteFile(path, data, mode); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Chmod(path, mode); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func readFile(t *testing.T, path string) []byte {
+	t.Helper()
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return data
+}
+
+func fileMode(t *testing.T, path string) os.FileMode {
+	t.Helper()
+	info, err := os.Stat(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return info.Mode().Perm()
+}
+
+func outsidePlanPath(name, outside string) string {
+	if name == "digest directory" {
+		return filepath.Join(outside, "plan.json")
+	}
+	return outside
+}

internal/framework/pipeline/runner.go

@@ -679,41 +679,11 @@ func validateOutputFileName(name string) error {
 }
 
 func cloneMetadata(metadata map[string]any) map[string]any {
-	if len(metadata) == 0 {
-		return nil
-	}
-	out := make(map[string]any, len(metadata))
-	for key, value := range metadata {
-		out[key] = cloneMetadataValue(value)
-	}
-	return out
-}
-
-func cloneMetadataValue(value any) any {
-	switch typed := value.(type) {
-	case map[string]any:
-		return cloneMetadata(typed)
-	case []any:
-		out := make([]any, len(typed))
-		for i := range typed {
-			out[i] = cloneMetadataValue(typed[i])
-		}
-		return out
-	case json.RawMessage:
-		return append(json.RawMessage(nil), typed...)
-	case []byte:
-		return append([]byte(nil), typed...)
-	case []string:
-		return append([]string(nil), typed...)
-	case map[string]string:
-		out := make(map[string]string, len(typed))
-		for key, item := range typed {
-			out[key] = item
-		}
-		return out
-	default:
-		return value
+	cloned, err := source.CloneMetadata(metadata)
+	if err != nil {
+		return metadata
 	}
+	return cloned
 }
 
 func cloneLLMProfiles(profiles []artifacts.LLMProfileManifest) []artifacts.LLMProfileManifest {

internal/framework/pipeline/runner_chunk_plan.go

@@ -47,11 +47,11 @@ func (r *Runner) runChunkPlan(ctx context.Context, input RunInput, doc *source.S
 	if mode == ChunkCacheAuto {
 		record, decision, err := input.ChunkPlans.Load(doc.Digest)
 		result.lookup = decision
-		result.summary.LookupStatus = string(decision.Status)
-		result.summary.LookupReason = decision.Reason
+		result.summary.LookupStatus = chunkPlanLookupStatus(decision.Status)
+		result.summary.LookupReason = chunkPlanLookupReason(decision.Status)
 		if err != nil {
 			result.summary.LookupStatus = "skipped"
-			result.summary.LookupReason = "chunk plan lookup failed"
+			result.summary.LookupReason = chunkPlanLookupReason("")
 			return result, fmt.Errorf("load chunk plan: %w", err)
 		}
 		switch decision.Status {
@@ -68,13 +68,13 @@ func (r *Runner) runChunkPlan(ctx context.Context, input RunInput, doc *source.S
 				result.setValidation(validationWarnings, rejection, err)
 				return result, err
 			}
-			result.lookup = ChunkPlanDecision{Status: ChunkPlanInvalid, Reason: "stored chunk plan cannot be materialized against the current source"}
+			result.lookup = ChunkPlanDecision{Status: ChunkPlanInvalid, Reason: chunkPlanLookupReason(ChunkPlanInvalid)}
 			result.summary.LookupStatus = "invalid"
-			result.summary.LookupReason = result.lookup.Reason
+			result.summary.LookupReason = chunkPlanLookupReason(ChunkPlanInvalid)
 		case ChunkPlanMissing, ChunkPlanInvalid:
 			// Generate below.
 		default:
-			return result, fmt.Errorf("load chunk plan returned unsupported status %q", decision.Status)
+			return result, fmt.Errorf("load chunk plan returned unsupported decision status")
 		}
 	}
 	if mode == ChunkCacheAuto || mode == ChunkCacheRefresh {
@@ -171,6 +171,32 @@ func (r *Runner) runChunkPlan(ctx context.Context, input RunInput, doc *source.S
 	return result, nil
 }
 
+func chunkPlanLookupStatus(status ChunkPlanStatus) string {
+	switch status {
+	case ChunkPlanHit:
+		return "hit"
+	case ChunkPlanMissing:
+		return "missing"
+	case ChunkPlanInvalid:
+		return "invalid"
+	default:
+		return "skipped"
+	}
+}
+
+func chunkPlanLookupReason(status ChunkPlanStatus) string {
+	switch status {
+	case ChunkPlanHit:
+		return "stored chunk plan is valid"
+	case ChunkPlanMissing:
+		return "chunk plan not found"
+	case ChunkPlanInvalid:
+		return "stored chunk plan is invalid"
+	default:
+		return "chunk plan lookup skipped"
+	}
+}
+
 func (result *chunkPlanExecution) setCandidate(record ChunkPlanRecord, action string) {
 	cloned := cloneChunkPlanRecord(record)
 	result.record = &cloned

internal/framework/pipeline/runner_chunk_plan_test.go

@@ -143,6 +143,43 @@ func TestRunnerChunkPlanModeMatrix(t *testing.T) {
 	}
 }
 
+func TestRunnerUsesStatusDerivedChunkPlanSummaryReasons(t *testing.T) {
+	for _, tc := range []struct {
+		name       string
+		status     ChunkPlanStatus
+		wantStatus string
+		wantReason string
+	}{
+		{name: "hit", status: ChunkPlanHit, wantStatus: "hit", wantReason: "stored chunk plan is valid"},
+		{name: "missing", status: ChunkPlanMissing, wantStatus: "missing", wantReason: "chunk plan not found"},
+		{name: "invalid", status: ChunkPlanInvalid, wantStatus: "invalid", wantReason: "stored chunk plan is invalid"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			prepared, plan := preparedTerminalDebugPipeline(t)
+			store := &recordingChunkPlanStore{
+				record:   chunkPlanRecord(t, prepared, plan),
+				decision: ChunkPlanDecision{Status: tc.status, Reason: "SENTINEL_STORE_REASON"},
+			}
+			output, err := New().Run(context.Background(), RunInput{Prepared: prepared, RawInput: []byte("input"), ChunkCacheMode: ChunkCacheAuto, ChunkPlans: store})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if output.ChunkPlan.LookupStatus != tc.wantStatus || output.ChunkPlan.LookupReason != tc.wantReason || strings.Contains(output.ChunkPlan.LookupReason, "SENTINEL_STORE_REASON") {
+				t.Fatalf("summary = %#v", output.ChunkPlan)
+			}
+		})
+	}
+
+	prepared, _ := preparedTerminalDebugPipeline(t)
+	output, err := New().Run(context.Background(), RunInput{
+		Prepared: prepared, RawInput: []byte("input"), ChunkCacheMode: ChunkCacheAuto,
+		ChunkPlans: &recordingChunkPlanStore{loadErr: errors.New("read failed")},
+	})
+	if err == nil || output.ChunkPlan == nil || output.ChunkPlan.LookupStatus != "skipped" || output.ChunkPlan.LookupReason != "chunk plan lookup skipped" {
+		t.Fatalf("operational lookup output=%#v error=%v", output.ChunkPlan, err)
+	}
+}
+
 func TestRunnerChunkPlanHitUsesStoredProducerProvenance(t *testing.T) {
 	prepared, plan := preparedTerminalDebugPipeline(t)
 	prepared.resolved.Chunk.Module = "chunk/requested"

internal/framework/pipeline/runner_extract_handoff_test.go

@@ -16,6 +16,24 @@ type extractCaptureRecorder struct {
 	checkpoint ExtractCheckpoint
 }
 
+type pipelineTypedMetadata map[string]any
+
+type mutatingMetadataValidator struct {
+	seen string
+}
+
+func (*mutatingMetadataValidator) Name() string { return "test/mutating-metadata" }
+func (*mutatingMetadataValidator) ExecutionClass() contracts.ExecutionClass {
+	return contracts.ExecutionClassDeterministic
+}
+func (v *mutatingMetadataValidator) Validate(_ context.Context, request contracts.ChunkValidationRequest) (contracts.ValidationResult, error) {
+	nested := request.Chunks[0].Units[0].Metadata["typed"].(pipelineTypedMetadata)
+	v.seen = string(nested["raw"].(json.RawMessage))
+	nested["raw"].(json.RawMessage)[0] = '['
+	nested["changed"] = true
+	return contracts.ValidationResult{Approved: true}, nil
+}
+
 func (r *extractCaptureRecorder) ExtractSucceeded(_ string, _ string, _ []CheckpointFingerprint, outputs []CheckpointArtifact, rejected []contracts.RejectedOutput, warnings []contracts.Warning) error {
 	r.checkpoint = ExtractCheckpoint{
 		Outputs:  cloneCheckpointArtifacts(outputs),
@@ -77,6 +95,46 @@ func TestRunnerPassesIndependentAnnotationScopesToExtractors(t *testing.T) {
 	}
 }
 
+func TestRunnerPassesIndependentConcreteMetadataToValidatorsAndExtractors(t *testing.T) {
+	prepared := preparedAttemptDebugPipeline(t)
+	input := prepared.input.(*typedTestInput)
+	input.doc.Units[0].Metadata = map[string]any{
+		"typed": pipelineTypedMetadata{"raw": json.RawMessage(`{"value":true}`)},
+	}
+	var err error
+	input.doc.Digest, err = source.DigestDocument(input.doc)
+	if err != nil {
+		t.Fatal(err)
+	}
+	chunker := prepared.chunker.(*typedTestChunker)
+	chunker.plan = typedTestPlan(input.doc)
+
+	validator := &mutatingMetadataValidator{}
+	prepared.chunkValidators.validators = []preparedValidator{{
+		resolved: ResolvedValidator{Binding: Binding(validator.Name()), Target: ValidatorTargetChunk},
+		chunk:    validator,
+	}}
+	var extractorSeen string
+	installExtractOperation(prepared, 0, func(_ context.Context, request contracts.TypedExtractionRequest) (erasedTypedResult, error) {
+		nested := request.Chunk.Units[0].Metadata["typed"].(pipelineTypedMetadata)
+		extractorSeen = string(nested["raw"].(json.RawMessage))
+		nested["raw"].(json.RawMessage)[0] = '['
+		nested["changed"] = true
+		return erasedTypedResult{Value: typedValueForLane(0, request.Chunk.Index)}, nil
+	})
+
+	if _, err := New().Run(context.Background(), RunInput{Prepared: prepared, RawInput: []byte("input")}); err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	if validator.seen != `{"value":true}` || extractorSeen != `{"value":true}` {
+		t.Fatalf("validator/extractor metadata = %q / %q", validator.seen, extractorSeen)
+	}
+	original := input.doc.Units[0].Metadata["typed"].(pipelineTypedMetadata)
+	if _, changed := original["changed"]; changed || string(original["raw"].(json.RawMessage)) != `{"value":true}` {
+		t.Fatalf("source metadata changed through runner handoff: %#v", original)
+	}
+}
+
 func TestRunnerContinuesFromFreshAndReusedExtractResults(t *testing.T) {
 	prepared := preparedAttemptDebugPipeline(t)
 	extractCalls := 0