Finish the domain pipeline cleanup

internal/framework/pipeline/artifact_codec_registry_test.go

@@ -24,19 +24,28 @@ type codecScore struct {
 type codecNotesAlias codecNotes
 
 type testArtifactCodec[T any] struct {
-	kind       contracts.ArtifactKind
-	schema     contracts.ArtifactSchema
-	mediaType  string
-	encodeFunc func(T) ([]byte, error)
-	decodeFunc func([]byte) (T, error)
+	kind          contracts.ArtifactKind
+	schema        contracts.ArtifactSchema
+	mediaType     string
+	encodeFunc    func(T) ([]byte, error)
+	candidateFunc func(T) ([]byte, error)
+	decodeFunc    func([]byte) (T, error)
 }
 
 func (c testArtifactCodec[T]) Kind() contracts.ArtifactKind     { return c.kind }
 func (c testArtifactCodec[T]) Schema() contracts.ArtifactSchema { return c.schema }
 func (c testArtifactCodec[T]) MediaType() string                { return c.mediaType }
+func (c testArtifactCodec[T]) EncodeCandidate(value T) ([]byte, error) {
+	if c.candidateFunc != nil {
+		return c.candidateFunc(value)
+	}
+	return c.encodeFunc(value)
+}
 func (c testArtifactCodec[T]) Encode(value T) ([]byte, error)   { return c.encodeFunc(value) }
 func (c testArtifactCodec[T]) Decode(content []byte) (T, error) { return c.decodeFunc(content) }
 
+var _ contracts.ArtifactCodec[codecNotes] = testArtifactCodec[codecNotes]{}
+
 func TestArtifactCodecRegistryStoresHeterogeneousExactTypes(t *testing.T) {
 	registry := NewArtifactCodecRegistry()
 	if err := RegisterArtifactCodec(registry, notesCodec()); err != nil {
@@ -92,6 +101,43 @@ func TestArtifactCodecRegistryStoresHeterogeneousExactTypes(t *testing.T) {
 	}
 }
 
+func TestArtifactCodecRegistryKeepsCandidateAndFinalEncodingDistinct(t *testing.T) {
+	candidateCalls, finalCalls := 0, 0
+	codec := notesCodec()
+	codec.candidateFunc = func(codecNotes) ([]byte, error) {
+		candidateCalls++
+		return []byte(`{"items":["candidate"]}`), nil
+	}
+	codec.encodeFunc = func(codecNotes) ([]byte, error) {
+		finalCalls++
+		return []byte(`{"items":["final"]}`), nil
+	}
+	registry := NewArtifactCodecRegistry()
+	if err := RegisterArtifactCodec(registry, codec); err != nil {
+		t.Fatalf("RegisterArtifactCodec() error = %v, want nil", err)
+	}
+	entry, _, err := registry.entry(codec.kind)
+	if err != nil {
+		t.Fatalf("entry() error = %v, want nil", err)
+	}
+
+	candidate, err := serializeArtifact(entry, codecNotes{}, true)
+	if err != nil {
+		t.Fatalf("serialize candidate error = %v, want nil", err)
+	}
+	if string(candidate.Content) != `{"items":["candidate"]}` || candidateCalls != 1 || finalCalls != 0 {
+		t.Fatalf("candidate content = %s, calls = candidate %d, final %d", candidate.Content, candidateCalls, finalCalls)
+	}
+
+	final, err := serializeArtifact(entry, codecNotes{}, false)
+	if err != nil {
+		t.Fatalf("serialize final error = %v, want nil", err)
+	}
+	if string(final.Content) != `{"items":["final"]}` || candidateCalls != 1 || finalCalls != 1 {
+		t.Fatalf("final content = %s, calls = candidate %d, final %d", final.Content, candidateCalls, finalCalls)
+	}
+}
+
 func TestArtifactCodecRegistryStoresValidatedSchemaMetadata(t *testing.T) {
 	registry := NewArtifactCodecRegistry()
 	codec := notesCodec()