Keep Gemini image edits role-aware on the server path

The server now resolves source, identity, and style artifacts separately, emits role-labeled Gemini parts, and logs the effective request shape so deployed debugging can confirm which references reached upstream.

Constraint: The test deployment must stay on gemini-3.1-flash-image-preview while gaining better multi-image editing semantics
Rejected: Change the default model to gemini-3-pro-image-preview | test-server parity required keeping flash as default
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Preserve the source/identity/style logging until the upstream gateway exposes equivalent structured traces
Tested: go test ./internal/server
Tested: image img2img against http://101.42.99.35:18080/v1 (job_5af212df2c27)
Not-tested: Non-Gemini multi-image providers still fall back to the first reference only

internal/server/newapi.go

@@ -12,6 +12,7 @@ import (
 	_ "image/jpeg"
 	_ "image/png"
 	"io"
+	"log"
 	"mime/multipart"
 	"net/http"
 	"net/textproto"
@@ -138,6 +139,7 @@ type upstreamModel struct {
 }
 
 type imageEditReference struct {
+	Role        string
 	Filename    string
 	ContentType string
 	Content     []byte
@@ -479,18 +481,21 @@ func (c *newAPIClient) generateImageRefs(ctx context.Context, token, modelID str
 	return decodeImageGenerationResponse(resp.StatusCode, respBody, modelID)
 }
 
-func (c *newAPIClient) generateEditedImageRefs(ctx context.Context, token, modelID string, input map[string]any, ref imageEditReference) ([]resultRef, map[string]any, error) {
+func (c *newAPIClient) generateEditedImageRefs(ctx context.Context, token, modelID string, input map[string]any, refs []imageEditReference) ([]resultRef, map[string]any, error) {
 	if !c.enabled() {
 		return nil, nil, errors.New("PopiNewAPI base URL is not configured")
 	}
+	if len(refs) == 0 {
+		return nil, nil, errors.New("reference image content is required")
+	}
 	if useGeminiImageGenerateContent(modelID) {
-		return c.generateGeminiImageRefs(ctx, token, modelID, input, []imageEditReference{ref})
+		return c.generateGeminiImageRefs(ctx, token, modelID, input, refs)
 	}
 	if useSeedreamImageGenerations(modelID) {
-		return c.generateSeedreamImageRefs(ctx, token, modelID, input, []imageEditReference{ref})
+		return c.generateSeedreamImageRefs(ctx, token, modelID, input, refs)
 	}
 	if useMiniMaxImageGenerations(modelID) {
-		return c.generateMiniMaxImageRefs(ctx, token, modelID, input, []imageEditReference{ref})
+		return c.generateMiniMaxImageRefs(ctx, token, modelID, input, refs)
 	}
 	token = c.authorizedImageEditToken(token)
 	if token == "" {
@@ -501,6 +506,7 @@ func (c *newAPIClient) generateEditedImageRefs(ctx context.Context, token, model
 	if prompt == "" {
 		return nil, nil, errors.New("prompt is required")
 	}
+	ref := refs[0]
 	if len(ref.Content) == 0 {
 		return nil, nil, errors.New("reference image content is required")
 	}
@@ -735,10 +741,13 @@ func (c *newAPIClient) generateGeminiImageRefs(ctx context.Context, token, model
 
 	parts := make([]map[string]any, 0, 1+len(refs))
 	parts = append(parts, map[string]any{"text": prompt})
-	for _, ref := range refs {
+	for index, ref := range refs {
 		if len(ref.Content) == 0 {
 			return nil, nil, errors.New("reference image content is required")
 		}
+		if label := geminiReferenceLabel(ref, index); label != "" {
+			parts = append(parts, map[string]any{"text": label})
+		}
 		contentType := strings.TrimSpace(ref.ContentType)
 		if contentType == "" {
 			contentType = http.DetectContentType(ref.Content)
@@ -770,6 +779,13 @@ func (c *newAPIClient) generateGeminiImageRefs(ctx context.Context, token, model
 	if len(imageConfig) > 0 {
 		generationConfig["imageConfig"] = imageConfig
 	}
+	log.Printf(
+		"popiartServer: Gemini image request model=%s parts=%d refs=%d image_config=%v",
+		modelID,
+		len(parts),
+		len(refs),
+		imageConfig,
+	)
 
 	body, err := json.Marshal(payload)
 	if err != nil {
@@ -899,6 +915,21 @@ func (c *newAPIClient) submitImageToVideoTask(ctx context.Context, token, modelI
 	return taskID, nil
 }
 
+func geminiReferenceLabel(ref imageEditReference, index int) string {
+	switch strings.ToLower(strings.TrimSpace(ref.Role)) {
+	case "source":
+		return fmt.Sprintf("Image %d is the source scene. Keep the scene layout, camera framing, main action, and spatial relationships from this image.", index+1)
+	case "identity":
+		return fmt.Sprintf("Image %d is the identity reference. Keep the character face, hair, accessories, and recognizability from this image.", index+1)
+	case "style":
+		return fmt.Sprintf("Image %d is the style reference. Apply only the visual style, palette, texture, and illustration treatment from this image. Do not change the character identity because of this image.", index+1)
+	case "reference":
+		return fmt.Sprintf("Image %d is an additional reference. Use it only for supporting details explicitly requested in the prompt.", index+1)
+	default:
+		return ""
+	}
+}
+
 func (c *newAPIClient) submitImageToVideoTaskByURL(ctx context.Context, token, modelID string, input map[string]any, ref imageEditReference, prompt string) (string, error) {
 	payload := map[string]any{
 		"model":    modelID,

internal/server/newapi_image_test.go

@@ -52,11 +52,11 @@ func TestGenerateGeminiImageRefsUsesGenerateContentEndpoint(t *testing.T) {
 	refs, usage, err := client.generateEditedImageRefs(context.Background(), "sk-test", "gemini-3-pro-image-preview", map[string]any{
 		"prompt": "edit this image",
 		"size":   "1024x1536",
-	}, imageEditReference{
+	}, []imageEditReference{{
 		Filename:    "source.png",
 		ContentType: "image/png",
 		Content:     refBytes,
-	})
+	}})
 	if err != nil {
 		t.Fatalf("generateEditedImageRefs: %v", err)
 	}
@@ -185,12 +185,12 @@ func TestGenerateEditedImageRefsUsesSeedreamImagesGenerationsEndpoint(t *testing
 	refs, usage, err := client.generateEditedImageRefs(context.Background(), "sk-test", "seedream-4-5-251128", map[string]any{
 		"prompt": "edit this image into a dusk scene",
 		"size":   "2K",
-	}, imageEditReference{
+	}, []imageEditReference{{
 		Filename:    "source.jpg",
 		ContentType: "image/jpeg",
 		Content:     []byte("binary-image"),
 		URL:         "https://example.com/reference.jpg",
-	})
+	}})
 	if err != nil {
 		t.Fatalf("generateEditedImageRefs: %v", err)
 	}
@@ -347,9 +347,9 @@ func TestGenerateMiniMaxEditedImageRefsSendsStandardImageField(t *testing.T) {
 		"prompt":          "turn it into watercolor",
 		"size":            "832x1248",
 		"response_format": "url",
-	}, imageEditReference{
+	}, []imageEditReference{{
 		URL: "https://example.com/reference.jpg",
-	})
+	}})
 	if err != nil {
 		t.Fatalf("generateEditedImageRefs: %v", err)
 	}
@@ -360,3 +360,70 @@ func TestGenerateMiniMaxEditedImageRefsSendsStandardImageField(t *testing.T) {
 		t.Fatalf("expected size passthrough for minimax mapping, got %#v", gotBody["size"])
 	}
 }
+
+func TestGenerateGeminiImageRefsAnnotatesMultiImageRoles(t *testing.T) {
+	const png1x1 = "iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAQAAAC1HAwCAAAAC0lEQVR42mP8/x8AAwMCAO7Z7xkAAAAASUVORK5CYII="
+
+	var gotBody map[string]any
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if err := json.NewDecoder(r.Body).Decode(&gotBody); err != nil {
+			t.Fatalf("decode request body: %v", err)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{
+			"candidates": [{
+				"content": {
+					"parts": [{
+						"inlineData": {
+							"mimeType": "image/png",
+							"data": "` + png1x1 + `"
+						}
+					}]
+				}
+			}]
+		}`))
+	}))
+	defer srv.Close()
+
+	refBytes, err := base64.StdEncoding.DecodeString(png1x1)
+	if err != nil {
+		t.Fatalf("decode fixture: %v", err)
+	}
+	client := &newAPIClient{
+		baseURL:    strings.TrimRight(srv.URL, "/"),
+		httpClient: srv.Client(),
+	}
+
+	_, _, err = client.generateGeminiImageRefs(context.Background(), "sk-test", "gemini-3-pro-image-preview", map[string]any{
+		"prompt": "Replace the person in Image 1 with the character from Image 2 and apply the style from Image 3.",
+	}, []imageEditReference{
+		{Role: "source", Filename: "source.png", ContentType: "image/png", Content: refBytes},
+		{Role: "identity", Filename: "identity.png", ContentType: "image/png", Content: refBytes},
+		{Role: "style", Filename: "style.png", ContentType: "image/png", Content: refBytes},
+	})
+	if err != nil {
+		t.Fatalf("generateGeminiImageRefs: %v", err)
+	}
+
+	contents, ok := gotBody["contents"].([]any)
+	if !ok || len(contents) != 1 {
+		t.Fatalf("unexpected contents: %#v", gotBody["contents"])
+	}
+	content, ok := contents[0].(map[string]any)
+	if !ok {
+		t.Fatalf("unexpected content entry: %#v", contents[0])
+	}
+	parts, ok := content["parts"].([]any)
+	if !ok || len(parts) != 7 {
+		t.Fatalf("expected prompt plus three labeled images, got %#v", content["parts"])
+	}
+	if got := parts[1].(map[string]any)["text"]; got != "Image 1 is the source scene. Keep the scene layout, camera framing, main action, and spatial relationships from this image." {
+		t.Fatalf("unexpected source label: %#v", got)
+	}
+	if got := parts[3].(map[string]any)["text"]; got != "Image 2 is the identity reference. Keep the character face, hair, accessories, and recognizability from this image." {
+		t.Fatalf("unexpected identity label: %#v", got)
+	}
+	if got := parts[5].(map[string]any)["text"]; got != "Image 3 is the style reference. Apply only the visual style, palette, texture, and illustration treatment from this image. Do not change the character identity because of this image." {
+		t.Fatalf("unexpected style label: %#v", got)
+	}
+}

internal/server/server.go

@@ -1159,7 +1159,7 @@ func (s *Server) executeImageToImageJob(record *job) {
 	defer cancel()
 
 	input := buildImageToImageInput(record)
-	ref, err := s.resolveImageToImageReference(ctx, record, input)
+	imageRefs, err := s.resolveImageToImageReferences(ctx, record, input)
 	if err != nil {
 		if repoErr := s.store.failJob(record.JobID, "REFERENCE_IMAGE_RESOLUTION_FAILED", err.Error(), map[string]any{
 			"skill_id":  record.SkillID,
@@ -1169,15 +1169,23 @@ func (s *Server) executeImageToImageJob(record *job) {
 		}
 		return
 	}
+	log.Printf(
+		"popiartServer: image job %s using model=%s refs=%s preserve_composition=%t strength=%v",
+		record.JobID,
+		modelID,
+		summarizeImageEditReferenceRoles(imageRefs),
+		boolValue(input["preserve_composition"]),
+		input["strength"],
+	)
 
 	var (
-		refs  []resultRef
-		usage map[string]any
+		resultRefs []resultRef
+		usage      map[string]any
 	)
 	if useMiniMaxImageGenerations(modelID) {
-		refs, usage, err = s.newapi.generateMiniMaxImageRefs(ctx, record.UpstreamKey, modelID, input, []imageEditReference{ref})
+		resultRefs, usage, err = s.newapi.generateMiniMaxImageRefs(ctx, record.UpstreamKey, modelID, input, imageRefs)
 	} else {
-		refs, usage, err = s.newapi.generateEditedImageRefs(ctx, record.UpstreamKey, modelID, input, ref)
+		resultRefs, usage, err = s.newapi.generateEditedImageRefs(ctx, record.UpstreamKey, modelID, input, imageRefs)
 	}
 	if err != nil {
 		if repoErr := s.store.failJob(record.JobID, "MODEL_REQUEST_FAILED", err.Error(), map[string]any{
@@ -1189,7 +1197,7 @@ func (s *Server) executeImageToImageJob(record *job) {
 		return
 	}
 
-	refs, err = s.persistResultRefs(ctx, record, refs)
+	resultRefs, err = s.persistResultRefs(ctx, record, resultRefs)
 	if err != nil {
 		if repoErr := s.store.failJob(record.JobID, "MEDIA_PERSIST_FAILED", "failed to persist generated media", map[string]any{
 			"details":   err.Error(),
@@ -1201,7 +1209,7 @@ func (s *Server) executeImageToImageJob(record *job) {
 		return
 	}
 
-	if err := s.store.completeJobWithResults(record.JobID, refs, usage); err != nil {
+	if err := s.store.completeJobWithResults(record.JobID, resultRefs, usage); err != nil {
 		log.Printf("popiartServer: complete job %s failed: %v", record.JobID, err)
 		if failErr := s.store.failJob(record.JobID, "RESULT_REF_PERSIST_FAILED", "failed to persist job result refs", map[string]any{
 			"details": err.Error(),
@@ -1394,33 +1402,45 @@ func inferRouteKeyForModel(modelID string, input map[string]any) string {
 	return "image.text2image"
 }
 
-func (s *Server) resolveImageToImageReference(ctx context.Context, record *job, input map[string]any) (imageEditReference, error) {
+func (s *Server) resolveImageToImageReferences(ctx context.Context, record *job, input map[string]any) ([]imageEditReference, error) {
 	if record == nil {
-		return imageEditReference{}, fmt.Errorf("job record is required")
+		return nil, fmt.Errorf("job record is required")
 	}
 	if artifactID := strings.TrimSpace(stringValue(input["source_artifact_id"])); artifactID != "" {
-		item, ref, exists, err := s.store.artifactRef(record.UserID, artifactID)
+		sourceRef, err := s.resolveArtifactImageReference(ctx, record, artifactID, "source")
 		if err != nil {
-			return imageEditReference{}, err
+			return nil, err
 		}
-		if !exists {
-			return imageEditReference{}, fmt.Errorf("source artifact not found: %s", artifactID)
+		refs := []imageEditReference{sourceRef}
+		seen := map[string]struct{}{artifactID: {}}
+		var appendArtifactRefs = func(role string, values []string) error {
+			for _, value := range values {
+				value = strings.TrimSpace(value)
+				if value == "" {
+					continue
+				}
+				if _, exists := seen[value]; exists {
+					continue
+				}
+				ref, err := s.resolveArtifactImageReference(ctx, record, value, role)
+				if err != nil {
+					return err
+				}
+				seen[value] = struct{}{}
+				refs = append(refs, ref)
+			}
+			return nil
 		}
-		contentType, _, reader, err := s.newapi.openResultRef(ctx, record.UpstreamKey, ref)
-		if err != nil {
-			return imageEditReference{}, err
+		if err := appendArtifactRefs("identity", stringSliceValue(input["identity_reference_artifact_ids"])); err != nil {
+			return nil, err
 		}
-		defer reader.Close()
-		content, err := io.ReadAll(reader)
-		if err != nil {
-			return imageEditReference{}, err
+		if err := appendArtifactRefs("style", stringSliceValue(input["style_reference_artifact_ids"])); err != nil {
+			return nil, err
+		}
+		if err := appendArtifactRefs("reference", stringSliceValue(input["reference_artifact_ids"])); err != nil {
+			return nil, err
 		}
-		return imageEditReference{
-			Filename:    item.Filename,
-			ContentType: defaultString(contentType, item.ContentType),
-			Content:     content,
-			URL:         item.URL,
-		}, nil
+		return refs, nil
 	}
 
 	refURL := strings.TrimSpace(stringValue(
@@ -1432,9 +1452,25 @@ func (s *Server) resolveImageToImageReference(ctx context.Context, record *job,
 		refURL = defaultAliceReferenceURL
 	}
 	if refURL == "" {
+		return nil, fmt.Errorf("reference image is required")
+	}
+	ref, err := s.downloadReferenceImage(ctx, refURL)
+	if err != nil {
+		return nil, err
+	}
+	ref.Role = "source"
+	return []imageEditReference{ref}, nil
+}
+
+func (s *Server) resolveImageToImageReference(ctx context.Context, record *job, input map[string]any) (imageEditReference, error) {
+	refs, err := s.resolveImageToImageReferences(ctx, record, input)
+	if err != nil {
+		return imageEditReference{}, err
+	}
+	if len(refs) == 0 {
 		return imageEditReference{}, fmt.Errorf("reference image is required")
 	}
-	return s.downloadReferenceImage(ctx, refURL)
+	return refs[0], nil
 }
 
 func (s *Server) resolveVideoReferences(ctx context.Context, record *job, input map[string]any) ([]imageEditReference, error) {
@@ -1651,6 +1687,32 @@ func buildAliceShowcasePrompt(input map[string]any, scenePrompt string) string {
 	return strings.Join(parts, ", ")
 }
 
+func (s *Server) resolveArtifactImageReference(ctx context.Context, record *job, artifactID, role string) (imageEditReference, error) {
+	item, ref, exists, err := s.store.artifactRef(record.UserID, artifactID)
+	if err != nil {
+		return imageEditReference{}, err
+	}
+	if !exists {
+		return imageEditReference{}, fmt.Errorf("%s artifact not found: %s", defaultString(role, "reference"), artifactID)
+	}
+	contentType, _, reader, err := s.newapi.openResultRef(ctx, record.UpstreamKey, ref)
+	if err != nil {
+		return imageEditReference{}, err
+	}
+	defer reader.Close()
+	content, err := io.ReadAll(reader)
+	if err != nil {
+		return imageEditReference{}, err
+	}
+	return imageEditReference{
+		Role:        role,
+		Filename:    item.Filename,
+		ContentType: defaultString(contentType, item.ContentType),
+		Content:     content,
+		URL:         item.URL,
+	}, nil
+}
+
 func buildGenericImageToImagePrompt(input map[string]any, prompt string) string {
 	parts := make([]string, 0, 6)
 	if prompt != "" {
@@ -1668,6 +1730,21 @@ func buildGenericImageToImagePrompt(input map[string]any, prompt string) string
 	return strings.Join(parts, ", ")
 }
 
+func summarizeImageEditReferenceRoles(refs []imageEditReference) string {
+	if len(refs) == 0 {
+		return "none"
+	}
+	parts := make([]string, 0, len(refs))
+	for _, ref := range refs {
+		role := strings.TrimSpace(ref.Role)
+		if role == "" {
+			role = "reference"
+		}
+		parts = append(parts, role)
+	}
+	return strings.Join(parts, ",")
+}
+
 func stringValue(values ...any) string {
 	for _, value := range values {
 		if text, ok := value.(string); ok && strings.TrimSpace(text) != "" {
@@ -1677,6 +1754,40 @@ func stringValue(values ...any) string {
 	return ""
 }
 
+func boolValue(value any) bool {
+	switch typed := value.(type) {
+	case bool:
+		return typed
+	default:
+		return false
+	}
+}
+
+func stringSliceValue(value any) []string {
+	switch typed := value.(type) {
+	case []string:
+		return cleanedStringValues(typed)
+	case []any:
+		items := make([]string, 0, len(typed))
+		for _, item := range typed {
+			items = append(items, strings.TrimSpace(fmt.Sprint(item)))
+		}
+		return cleanedStringValues(items)
+	default:
+		return nil
+	}
+}
+
+func cleanedStringValues(values []string) []string {
+	items := make([]string, 0, len(values))
+	for _, value := range values {
+		if trimmed := strings.TrimSpace(value); trimmed != "" {
+			items = append(items, trimmed)
+		}
+	}
+	return items
+}
+
 func buildVideoResultRef(baseURL, taskID, modelID string, task *videoTaskResult) resultRef {
 	urlValue := strings.TrimSpace(task.URL)
 	if urlValue == "" {