feat(openai-images): support prompt optimization control

backend/internal/handler/admin/account_handler.go

@@ -698,9 +698,10 @@ func (h *AccountHandler) Delete(c *gin.Context) {
 
 // TestAccountRequest represents the request body for testing an account
 type TestAccountRequest struct {
-	ModelID string `json:"model_id"`
-	Prompt  string `json:"prompt"`
-	Mode    string `json:"mode"`
+	ModelID            string `json:"model_id"`
+	Prompt             string `json:"prompt"`
+	Mode               string `json:"mode"`
+	PromptOptimization *bool  `json:"prompt_optimization"`
 }
 
 type SyncFromCRSRequest struct {
@@ -731,7 +732,7 @@ func (h *AccountHandler) Test(c *gin.Context) {
 	_ = c.ShouldBindJSON(&req)
 
 	// Use AccountTestService to test the account with SSE streaming
-	if err := h.accountTestService.TestAccountConnection(c, accountID, req.ModelID, req.Prompt, req.Mode); err != nil {
+	if err := h.accountTestService.TestAccountConnection(c, accountID, req.ModelID, req.Prompt, req.Mode, req.PromptOptimization); err != nil {
 		// Error already sent via SSE, just log
 		return
 	}

backend/internal/service/account_test_service.go

@@ -170,7 +170,7 @@ func createTestPayload(modelID string) (map[string]any, error) {
 // All account types use full Claude Code client characteristics, only auth header differs
 // modelID is optional - if empty, defaults to claude.DefaultTestModel
 // mode is optional - "compact" routes OpenAI accounts to the /responses/compact probe path
-func (s *AccountTestService) TestAccountConnection(c *gin.Context, accountID int64, modelID string, prompt string, mode string) error {
+func (s *AccountTestService) TestAccountConnection(c *gin.Context, accountID int64, modelID string, prompt string, mode string, promptOptimization *bool) error {
 	ctx := c.Request.Context()
 
 	// Get account
@@ -181,7 +181,7 @@ func (s *AccountTestService) TestAccountConnection(c *gin.Context, accountID int
 
 	// Route to platform-specific test method
 	if account.IsOpenAI() {
-		return s.testOpenAIAccountConnection(c, account, modelID, prompt, normalizeAccountTestMode(mode))
+		return s.testOpenAIAccountConnection(c, account, modelID, prompt, normalizeAccountTestMode(mode), promptOptimization)
 	}
 
 	if account.IsGemini() {
@@ -492,9 +492,8 @@ func (s *AccountTestService) testBedrockAccountConnection(c *gin.Context, ctx co
 }
 
 // testOpenAIAccountConnection tests an OpenAI account's connection
-func (s *AccountTestService) testOpenAIAccountConnection(c *gin.Context, account *Account, modelID string, prompt string, mode string) error {
+func (s *AccountTestService) testOpenAIAccountConnection(c *gin.Context, account *Account, modelID string, prompt string, mode string, promptOptimization *bool) error {
 	ctx := c.Request.Context()
-	_ = prompt
 	mode = normalizeAccountTestMode(mode)
 
 	// Default to openai.DefaultTestModel for OpenAI testing
@@ -520,7 +519,7 @@ func (s *AccountTestService) testOpenAIAccountConnection(c *gin.Context, account
 		if account.Type == "apikey" {
 			return s.testOpenAIImageAPIKey(c, ctx, account, testModelID, imagePrompt)
 		}
-		return s.testOpenAIImageOAuth(c, ctx, account, testModelID, imagePrompt)
+		return s.testOpenAIImageOAuth(c, ctx, account, testModelID, imagePrompt, promptOptimization)
 	}
 
 	// Determine authentication method and API URL
@@ -1415,7 +1414,7 @@ func (s *AccountTestService) testOpenAIImageAPIKey(c *gin.Context, ctx context.C
 }
 
 // testOpenAIImageOAuth tests OpenAI image generation using an OAuth account via Codex /responses API.
-func (s *AccountTestService) testOpenAIImageOAuth(c *gin.Context, ctx context.Context, account *Account, modelID, prompt string) error {
+func (s *AccountTestService) testOpenAIImageOAuth(c *gin.Context, ctx context.Context, account *Account, modelID, prompt string, promptOptimization *bool) error {
 	authToken := account.GetOpenAIAccessToken()
 	if authToken == "" {
 		return s.sendErrorAndEnd(c, "No access token available")
@@ -1432,9 +1431,10 @@ func (s *AccountTestService) testOpenAIImageOAuth(c *gin.Context, ctx context.Co
 	s.sendEvent(c, TestEvent{Type: "content", Text: "Calling Codex /responses image tool...\n"})
 
 	parsed := &OpenAIImagesRequest{
-		Endpoint: openAIImagesGenerationsEndpoint,
-		Model:    strings.TrimSpace(modelID),
-		Prompt:   prompt,
+		Endpoint:           openAIImagesGenerationsEndpoint,
+		Model:              strings.TrimSpace(modelID),
+		Prompt:             prompt,
+		PromptOptimization: promptOptimization,
 	}
 	applyOpenAIImagesDefaults(parsed)
 
@@ -1538,7 +1538,7 @@ func (s *AccountTestService) RunTestBackground(ctx context.Context, accountID in
 	ginCtx, _ := gin.CreateTestContext(w)
 	ginCtx.Request = (&http.Request{}).WithContext(ctx)
 
-	testErr := s.TestAccountConnection(ginCtx, accountID, modelID, "", AccountTestModeDefault)
+	testErr := s.TestAccountConnection(ginCtx, accountID, modelID, "", AccountTestModeDefault, nil)
 
 	finishedAt := time.Now()
 	body := w.Body.String()

backend/internal/service/account_test_service_openai_compact_test.go

@@ -49,7 +49,7 @@ func TestAccountTestService_TestAccountConnection_OpenAICompactOAuthSuccessPersi
 	c, _ := gin.CreateTestContext(rec)
 	c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/admin/accounts/1/test", bytes.NewReader(nil))
 
-	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact)
+	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact, nil)
 	require.NoError(t, err)
 
 	require.Equal(t, chatgptCodexAPIURL+"/compact", upstream.lastReq.URL.String())
@@ -102,7 +102,7 @@ func TestAccountTestService_TestAccountConnection_OpenAICompactOAuth404MarksUnsu
 	c, _ := gin.CreateTestContext(rec)
 	c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/admin/accounts/2/test", bytes.NewReader(nil))
 
-	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact)
+	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact, nil)
 	require.Error(t, err)
 
 	updates := <-updateCalls
@@ -148,7 +148,7 @@ func TestAccountTestService_TestAccountConnection_OpenAICompactAPIKeyUsesCompact
 	c, _ := gin.CreateTestContext(rec)
 	c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/admin/accounts/3/test", bytes.NewReader(nil))
 
-	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact)
+	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact, nil)
 	require.NoError(t, err)
 
 	require.Equal(t, "https://example.com/v1/responses/compact", upstream.lastReq.URL.String())
@@ -192,7 +192,7 @@ func TestAccountTestService_TestAccountConnection_OpenAICompactAPIKeyDefaultBase
 	c, _ := gin.CreateTestContext(rec)
 	c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/admin/accounts/4/test", bytes.NewReader(nil))
 
-	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact)
+	err := svc.TestAccountConnection(c, account.ID, "gpt-5.4", "", AccountTestModeCompact, nil)
 	require.NoError(t, err)
 	require.Equal(t, "https://api.openai.com/v1/responses/compact", upstream.lastReq.URL.String())
 	<-updateCalls

backend/internal/service/account_test_service_openai_image_test.go

@@ -43,13 +43,50 @@ func TestAccountTestService_OpenAIImageOAuthHandlesOutputItemDoneFallback(t *tes
 		},
 	}
 
-	err := svc.testOpenAIImageOAuth(c, context.Background(), account, "gpt-image-2", "draw a cat")
+	err := svc.testOpenAIImageOAuth(c, context.Background(), account, "gpt-image-2", "draw a cat", nil)
 	require.NoError(t, err)
 	require.Contains(t, rec.Body.String(), "Calling Codex /responses image tool")
 	require.Contains(t, rec.Body.String(), "data:image/png;base64,aGVsbG8=")
 	require.Contains(t, rec.Body.String(), "\"success\":true")
 }
 
+func TestAccountTestService_OpenAIImageOAuthCanDisablePromptOptimization(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/api/v1/admin/accounts/1/test", nil)
+
+	upstream := &httpUpstreamRecorder{
+		resp: &http.Response{
+			StatusCode: http.StatusOK,
+			Header: http.Header{
+				"Content-Type": []string{"text/event-stream"},
+			},
+			Body: io.NopCloser(strings.NewReader(
+				"data: {\"type\":\"response.output_item.done\",\"item\":{\"id\":\"ig_123\",\"type\":\"image_generation_call\",\"result\":\"aGVsbG8=\",\"output_format\":\"png\"}}\n\n" +
+					"data: {\"type\":\"response.completed\",\"response\":{\"created_at\":1710000006,\"tool_usage\":{\"image_gen\":{\"images\":1}},\"output\":[]}}\n\n" +
+					"data: [DONE]\n\n",
+			)),
+		},
+	}
+	svc := &AccountTestService{httpUpstream: upstream}
+	account := &Account{
+		ID:       53,
+		Name:     "openai-oauth",
+		Platform: PlatformOpenAI,
+		Type:     AccountTypeOAuth,
+		Credentials: map[string]any{
+			"access_token": "token-123",
+		},
+	}
+
+	disabled := false
+	err := svc.testOpenAIImageOAuth(c, context.Background(), account, "gpt-image-2", "draw a cat", &disabled)
+	require.NoError(t, err)
+	require.Contains(t, string(upstream.lastBody), "Do not rewrite")
+	require.Contains(t, rec.Body.String(), "\"success\":true")
+}
+
 func TestAccountTestService_OpenAIImageAPIKeyUsesConfiguredV1BaseURL(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	rec := httptest.NewRecorder()

backend/internal/service/account_test_service_openai_test.go

@@ -125,7 +125,7 @@ func TestAccountTestService_OpenAISuccessPersistsSnapshotFromHeaders(t *testing.
 		Credentials: map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.NoError(t, err)
 	require.NotEmpty(t, repo.updatedExtra)
 	require.Equal(t, 42.0, repo.updatedExtra["codex_5h_used_percent"])
@@ -152,7 +152,7 @@ func TestAccountTestService_OpenAIStreamEOFBeforeCompletedFails(t *testing.T) {
 		Credentials: map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Contains(t, recorder.Body.String(), "response.completed")
 	require.NotContains(t, recorder.Body.String(), `"success":true`)
@@ -182,7 +182,7 @@ func TestAccountTestService_OpenAI429PersistsSnapshotAndRateLimitState(t *testin
 		Credentials: map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.NotEmpty(t, repo.updatedExtra)
 	require.Equal(t, 100.0, repo.updatedExtra["codex_5h_used_percent"])
@@ -213,7 +213,7 @@ func TestAccountTestService_OpenAI429BodyOnlyPersistsRateLimitAndClearsStaleErro
 		Credentials:  map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Equal(t, account.ID, repo.rateLimitedID)
 	require.NotNil(t, repo.rateLimitedAt)
@@ -242,7 +242,7 @@ func TestAccountTestService_OpenAI429SyncsObservedPlanType(t *testing.T) {
 		Credentials: map[string]any{"access_token": "test-token", "plan_type": "plus"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Equal(t, []int64{account.ID}, repo.bulkUpdatedIDs)
 	require.Equal(t, "free", repo.bulkUpdatedPayload.Credentials["plan_type"])
@@ -269,7 +269,7 @@ func TestAccountTestService_OpenAI429ActiveAccountDoesNotClearError(t *testing.T
 		Credentials: map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Equal(t, account.ID, repo.rateLimitedID)
 	require.NotNil(t, repo.rateLimitedAt)
@@ -297,7 +297,7 @@ func TestAccountTestService_OpenAI429WithoutResetSignalDoesNotMutateRuntimeState
 		Credentials:  map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Zero(t, repo.rateLimitedID)
 	require.Nil(t, repo.rateLimitedAt)
@@ -325,7 +325,7 @@ func TestAccountTestService_OpenAI401SetsPermanentErrorOnly(t *testing.T) {
 		Credentials: map[string]any{"access_token": "test-token"},
 	}
 
-	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "")
+	err := svc.testOpenAIAccountConnection(ctx, account, "gpt-5.4", "", "", nil)
 	require.Error(t, err)
 	require.Equal(t, account.ID, repo.setErrorID)
 	require.Contains(t, repo.setErrorMsg, "Authentication failed (401)")

backend/internal/service/openai_images.go

@@ -65,6 +65,7 @@ type OpenAIImagesRequest struct {
 	Model              string
 	ExplicitModel      bool
 	Prompt             string
+	PromptOptimization *bool
 	Stream             bool
 	N                  int
 	Size               string
@@ -229,6 +230,11 @@ func parseOpenAIImagesJSONRequest(body []byte, req *OpenAIImagesRequest) error {
 		req.ExplicitModel = req.Model != ""
 	}
 	req.Prompt = strings.TrimSpace(gjson.GetBytes(body, "prompt").String())
+	promptOptimization, err := parseOpenAIImagesJSONOptionalBool(body, "prompt_optimization", "promptOptimization")
+	if err != nil {
+		return err
+	}
+	req.PromptOptimization = promptOptimization
 
 	if streamResult := gjson.GetBytes(body, "stream"); streamResult.Exists() {
 		if streamResult.Type != gjson.True && streamResult.Type != gjson.False {
@@ -374,6 +380,12 @@ func parseOpenAIImagesMultipartRequest(body []byte, contentType string, req *Ope
 			req.ExplicitModel = value != ""
 		case "prompt":
 			req.Prompt = value
+		case "prompt_optimization", "promptOptimization":
+			parsed, err := strconv.ParseBool(value)
+			if err != nil {
+				return fmt.Errorf("invalid %s field value", name)
+			}
+			req.PromptOptimization = &parsed
 		case "size":
 			req.Size = value
 			req.ExplicitSize = value != ""
@@ -436,6 +448,29 @@ func parseOpenAIImagesMultipartRequest(body []byte, contentType string, req *Ope
 	return nil
 }
 
+func parseOpenAIImagesJSONOptionalBool(body []byte, paths ...string) (*bool, error) {
+	for _, path := range paths {
+		result := gjson.GetBytes(body, path)
+		if !result.Exists() {
+			continue
+		}
+		switch result.Type {
+		case gjson.True, gjson.False:
+			value := result.Bool()
+			return &value, nil
+		case gjson.String:
+			value, err := strconv.ParseBool(strings.TrimSpace(result.String()))
+			if err != nil {
+				return nil, fmt.Errorf("invalid %s field value", path)
+			}
+			return &value, nil
+		default:
+			return nil, fmt.Errorf("invalid %s field type", path)
+		}
+	}
+	return nil, nil
+}
+
 func parseOpenAIImageDimensions(_ textproto.MIMEHeader) (int, int) {
 	return 0, 0
 }
@@ -808,21 +843,46 @@ func buildOpenAIImagesURL(base string, endpoint string) string {
 
 func rewriteOpenAIImagesModel(body []byte, contentType string, model string) ([]byte, string, error) {
 	model = strings.TrimSpace(model)
-	if model == "" {
-		return body, contentType, nil
-	}
 	mediaType, _, err := mime.ParseMediaType(contentType)
 	if err == nil && strings.EqualFold(mediaType, "multipart/form-data") {
 		rewrittenBody, rewrittenType, rewriteErr := rewriteOpenAIImagesMultipartModel(body, contentType, model)
 		return rewrittenBody, rewrittenType, rewriteErr
 	}
-	rewritten, err := sjson.SetBytes(body, "model", model)
+	rewritten, err := stripOpenAIImagesInternalJSONFields(body)
+	if err != nil {
+		return nil, "", err
+	}
+	if model == "" {
+		return rewritten, contentType, nil
+	}
+	rewritten, err = sjson.SetBytes(rewritten, "model", model)
 	if err != nil {
 		return nil, "", fmt.Errorf("rewrite image request model: %w", err)
 	}
 	return rewritten, contentType, nil
 }
 
+func stripOpenAIImagesInternalJSONFields(body []byte) ([]byte, error) {
+	rewritten := body
+	var err error
+	for _, path := range []string{"prompt_optimization", "promptOptimization"} {
+		rewritten, err = sjson.DeleteBytes(rewritten, path)
+		if err != nil {
+			return nil, fmt.Errorf("strip image request field %s: %w", path, err)
+		}
+	}
+	return rewritten, nil
+}
+
+func isOpenAIImagesInternalMultipartField(name string) bool {
+	switch strings.TrimSpace(name) {
+	case "prompt_optimization", "promptOptimization":
+		return true
+	default:
+		return false
+	}
+}
+
 func rewriteOpenAIImagesMultipartModel(body []byte, contentType string, model string) ([]byte, string, error) {
 	_, params, err := mime.ParseMediaType(contentType)
 	if err != nil {
@@ -848,14 +908,18 @@ func rewriteOpenAIImagesMultipartModel(body []byte, contentType string, model st
 		}
 
 		formName := strings.TrimSpace(part.FormName())
+		if part.FileName() == "" && isOpenAIImagesInternalMultipartField(formName) {
+			_ = part.Close()
+			continue
+		}
 		partHeader := cloneMultipartHeader(part.Header)
 		target, err := writer.CreatePart(partHeader)
 		if err != nil {
 			_ = part.Close()
 			return nil, "", fmt.Errorf("create multipart part: %w", err)
 		}
 
-		if formName == "model" && part.FileName() == "" {
+		if formName == "model" && part.FileName() == "" && model != "" {
 			if _, err := target.Write([]byte(model)); err != nil {
 				_ = part.Close()
 				return nil, "", fmt.Errorf("rewrite multipart model: %w", err)
@@ -871,7 +935,7 @@ func rewriteOpenAIImagesMultipartModel(body []byte, contentType string, model st
 		_ = part.Close()
 	}
 
-	if !modelWritten {
+	if !modelWritten && model != "" {
 		if err := writer.WriteField("model", model); err != nil {
 			return nil, "", fmt.Errorf("append multipart model field: %w", err)
 		}