Remove legacy manifest provenance decoding

internal/manifest/manifest.go

@@ -1,7 +1,6 @@
 package manifest
 
 import (
-	"encoding/json"
 	"strings"
 	"time"
 
@@ -76,18 +75,6 @@ type EffectiveConfigProvenance struct {
 	EffectiveConfigDigest string                     `json:"effective_config_digest,omitempty"`
 }
 
-// UnmarshalJSON accepts unknown informational provenance from older manifests.
-// The enclosing manifest and its execution state remain strictly decoded.
-func (p *EffectiveConfigProvenance) UnmarshalJSON(data []byte) error {
-	type provenance EffectiveConfigProvenance
-	var decoded provenance
-	if err := json.Unmarshal(data, &decoded); err != nil {
-		return err
-	}
-	*p = EffectiveConfigProvenance(decoded)
-	return nil
-}
-
 // SelectedOverlayProvenance identifies an explicitly or default-selected
 // pipeline overlay without recording overlay content.
 type SelectedOverlayProvenance struct {

internal/manifest/store_test.go

@@ -75,18 +75,19 @@ func TestLocalStoreCreateSaveLoadRoundTrip(t *testing.T) {
 	}
 }
 
-func TestLocalStoreLoadsManifestWithHistoricalSelectionProvenance(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "manifest.json")
-	data := `{"schema_version":"narratio.session-manifest.v1","session_id":"2026-05-03","created_at":"2026-05-03T10:00:00Z","updated_at":"2026-05-03T10:00:00Z","effective_config":{"selected_profile":{"name":"testing","source":"explicit"},"effective_config_digest":"001122"},"stages":{}}`
-	if err := os.WriteFile(path, []byte(data), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	loaded, err := (&LocalStore{}).Load(context.Background(), path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if loaded.EffectiveConfig == nil || loaded.EffectiveConfig.EffectiveConfigDigest != "001122" || loaded.EffectiveConfig.SelectedOverlay != nil {
-		t.Fatalf("historical informational provenance = %#v", loaded.EffectiveConfig)
+func TestLocalStoreRejectsUnknownProvenanceFields(t *testing.T) {
+	for _, tc := range []struct{ name, provenance, field string }{
+		{"retired selection", `{"selected_profile":{"name":"testing","source":"explicit"}}`, "selected_profile"},
+		{"unknown provenance", `{"unexpected":true}`, "unexpected"},
+		{"unknown selection field", `{"selected_overlay":{"name":"testing","source":"explicit","unexpected":true}}`, "unexpected"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			data := `{"schema_version":"narratio.session-manifest.v1","session_id":"2026-05-03","created_at":"2026-05-03T10:00:00Z","updated_at":"2026-05-03T10:00:00Z","effective_config":` + tc.provenance + `,"stages":{}}`
+			_, err := (&LocalStore{}).LoadReader(context.Background(), strings.NewReader(data))
+			if err == nil || !strings.Contains(err.Error(), tc.field) {
+				t.Fatalf("expected rejection identifying %q, got %v", tc.field, err)
+			}
+		})
 	}
 }