fix(openai): preserve Codex image function tools during bridge injection

backend/internal/service/openai_codex_transform.go

@@ -83,6 +83,8 @@ type codexOAuthTransformOptions struct {
 	PreserveToolCallIDs     bool
 }
 
+const codexImageGenerationFunctionToolName = "image_gen.imagegen"
+
 const (
 	codexImageGenerationBridgeMarker = "<sub2api-codex-image-generation>"
 	codexImageGenerationBridgeText   = codexImageGenerationBridgeMarker + "\nWhen the user asks for raster image generation or editing, use the OpenAI Responses native `image_generation` tool attached to this request. The local Codex client may not expose an `image_gen` namespace, but that does not mean image generation is unavailable. Do not ask the user to switch to CLI fallback solely because `image_gen` is absent.\n</sub2api-codex-image-generation>"
@@ -616,6 +618,11 @@ func hasOpenAIImageGenerationTool(reqBody map[string]any) bool {
 	return inputContainsImageGenerationTool(reqBody["input"])
 }
 
+func hasCodexImageGenerationFunctionTool(reqBody map[string]any) bool {
+	return len(reqBody) > 0 &&
+		codexToolsContainFunctionName(reqBody["tools"], codexImageGenerationFunctionToolName)
+}
+
 func toolsContainImageGeneration(rawTools any) bool {
 	if rawTools == nil {
 		return false
@@ -855,6 +862,9 @@ func ensureOpenAIResponsesImageGenerationTool(reqBody map[string]any) bool {
 	if isCodexSparkModel(firstNonEmptyString(reqBody["model"])) {
 		return false
 	}
+	if hasCodexImageGenerationFunctionTool(reqBody) {
+		return false
+	}
 	if hasOpenAIImageGenerationTool(reqBody) {
 		return false
 	}
@@ -880,7 +890,7 @@ func ensureOpenAIResponsesImageGenerationTool(reqBody map[string]any) bool {
 }
 
 func ensureOpenAIResponsesImageGenerationToolChoiceAuto(reqBody map[string]any) bool {
-	if len(reqBody) == 0 || !hasOpenAIImageGenerationTool(reqBody) {
+	if len(reqBody) == 0 || hasCodexImageGenerationFunctionTool(reqBody) || !hasOpenAIImageGenerationTool(reqBody) {
 		return false
 	}
 	if isCodexSparkModel(firstNonEmptyString(reqBody["model"])) {
@@ -894,7 +904,7 @@ func ensureOpenAIResponsesImageGenerationToolChoiceAuto(reqBody map[string]any)
 }
 
 func applyCodexImageGenerationBridgeInstructions(reqBody map[string]any) bool {
-	if len(reqBody) == 0 || !hasOpenAIImageGenerationTool(reqBody) {
+	if len(reqBody) == 0 || hasCodexImageGenerationFunctionTool(reqBody) || !hasOpenAIImageGenerationTool(reqBody) {
 		return false
 	}
 	if isCodexSparkModel(firstNonEmptyString(reqBody["model"])) {

backend/internal/service/openai_codex_transform_test.go

@@ -676,6 +676,86 @@ func TestEnsureOpenAIResponsesImageGenerationTool_PreservesImageGenNamespace(t *
 	}
 }
 
+func TestCodexImageGenerationBridge_PreservesClientImageFunctionTools(t *testing.T) {
+	tests := []struct {
+		name       string
+		reqBody    map[string]any
+		wantClient bool
+	}{
+		{
+			name: "flat image_gen function",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"input": "draw a cat",
+				"tools": []any{
+					map[string]any{"type": "function", "name": "image_gen.imagegen"},
+				},
+			},
+			wantClient: true,
+		},
+		{
+			name: "nested image_gen function",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"input": "draw a cat",
+				"tools": []any{
+					map[string]any{
+						"type": "function",
+						"function": map[string]any{
+							"name": "image_gen.imagegen",
+						},
+					},
+				},
+			},
+			wantClient: true,
+		},
+		{
+			name: "similar function name still receives hosted bridge",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"input": "draw a cat",
+				"tools": []any{
+					map[string]any{"type": "function", "name": "image_gen.imagegenerator"},
+				},
+			},
+			wantClient: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.reqBody["instructions"] = "existing instructions"
+			require.Equal(t, tt.wantClient, hasCodexImageGenerationFunctionTool(tt.reqBody))
+
+			toolModified := ensureOpenAIResponsesImageGenerationTool(tt.reqBody)
+			choiceModified := ensureOpenAIResponsesImageGenerationToolChoiceAuto(tt.reqBody)
+			instructionsModified := applyCodexImageGenerationBridgeInstructions(tt.reqBody)
+
+			require.Equal(t, !tt.wantClient, toolModified)
+			require.Equal(t, !tt.wantClient, choiceModified)
+			require.Equal(t, !tt.wantClient, instructionsModified)
+
+			hasHostedTool := false
+			tools, _ := tt.reqBody["tools"].([]any)
+			for _, rawTool := range tools {
+				tool, ok := rawTool.(map[string]any)
+				if ok && firstNonEmptyString(tool["type"]) == "image_generation" {
+					hasHostedTool = true
+				}
+			}
+			require.Equal(t, !tt.wantClient, hasHostedTool)
+
+			if tt.wantClient {
+				require.NotContains(t, tt.reqBody, "tool_choice")
+				require.Equal(t, "existing instructions", tt.reqBody["instructions"])
+			} else {
+				require.Equal(t, "auto", tt.reqBody["tool_choice"])
+				require.Contains(t, tt.reqBody["instructions"], codexImageGenerationBridgeMarker)
+			}
+		})
+	}
+}
+
 func TestApplyCodexImageGenerationBridgeInstructions_AppendsBridgeOnce(t *testing.T) {
 	reqBody := map[string]any{
 		"model":        "gpt-5.4",

backend/internal/service/openai_image_generation_controls_test.go

@@ -353,6 +353,54 @@ func TestOpenAIGatewayServiceForward_CodexBridgeDoesNotInjectHostedToolAlongside
 	require.Equal(t, "namespace", gjson.GetBytes(upstream.lastBody, `input.#(type=="additional_tools").tools.#(name=="image_gen").type`).String())
 }
 
+func TestOpenAIGatewayServiceForward_CodexBridgePreservesImageGenFunction(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+
+	tests := []struct {
+		name string
+		tool string
+	}{
+		{
+			name: "flat function",
+			tool: `{"type":"function","name":"image_gen.imagegen","parameters":{"type":"object"}}`,
+		},
+		{
+			name: "nested function",
+			tool: `{"type":"function","function":{"name":"image_gen.imagegen","parameters":{"type":"object"}}}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			upstream := &httpUpstreamRecorder{
+				resp: &http.Response{
+					StatusCode: http.StatusOK,
+					Header:     http.Header{"Content-Type": []string{"application/json"}},
+					Body:       io.NopCloser(strings.NewReader(`{"id":"resp_function_image","model":"gpt-5.5","usage":{"input_tokens":1,"output_tokens":1}}`)),
+				},
+			}
+			svc := newOpenAIImageGenerationControlTestService(upstream)
+			svc.cfg.Gateway.CodexImageGenerationBridgeEnabled = true
+			c, _ := newOpenAIImageGenerationControlTestContext(true, "codex_cli_rs/0.144.1")
+			account := newOpenAIImageGenerationControlTestAccount()
+			body := []byte(`{"model":"gpt-5.5","input":"draw a cat","stream":false,"tools":[` + tt.tool + `]}`)
+
+			result, err := svc.Forward(context.Background(), c, account, body)
+
+			require.NoError(t, err)
+			require.NotNil(t, result)
+			require.NotNil(t, upstream.lastReq)
+
+			var forwarded map[string]any
+			require.NoError(t, json.Unmarshal(upstream.lastBody, &forwarded))
+			require.True(t, hasCodexImageGenerationFunctionTool(forwarded))
+			require.False(t, gjson.GetBytes(upstream.lastBody, `tools.#(type=="image_generation")`).Exists())
+			require.False(t, gjson.GetBytes(upstream.lastBody, "tool_choice").Exists())
+			require.NotContains(t, gjson.GetBytes(upstream.lastBody, "instructions").String(), codexImageGenerationBridgeMarker)
+		})
+	}
+}
+
 func TestOpenAIGatewayServiceForward_CodexBridgePreservesExistingToolChoice(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 

backend/internal/service/openai_ws_forwarder_ingress_session_test.go

@@ -425,6 +425,7 @@ func TestOpenAIGatewayService_ProxyResponsesWebSocketFromClient_CodexImageBridge
 		events: [][]byte{
 			[]byte(`{"type":"response.completed","response":{"id":"resp_codex_image_bridge","model":"gpt-5.5","usage":{"input_tokens":1,"output_tokens":1}}}`),
 			[]byte(`{"type":"response.completed","response":{"id":"resp_codex_image_lite","model":"gpt-5.5","usage":{"input_tokens":1,"output_tokens":1}}}`),
+			[]byte(`{"type":"response.completed","response":{"id":"resp_codex_image_function","model":"gpt-5.5","usage":{"input_tokens":1,"output_tokens":1}}}`),
 		},
 	}
 	captureDialer := &openAIWSCaptureDialer{conn: captureConn}
@@ -548,6 +549,25 @@ func TestOpenAIGatewayService_ProxyResponsesWebSocketFromClient_CodexImageBridge
 	require.Equal(t, coderws.MessageText, msgType)
 	require.Equal(t, "resp_codex_image_lite", gjson.GetBytes(message, "response.id").String())
 
+	writeCtx, cancelWrite = context.WithTimeout(context.Background(), 3*time.Second)
+	err = clientConn.Write(writeCtx, coderws.MessageText, []byte(`{
+		"type":"response.create",
+		"model":"gpt-5.5",
+		"stream":false,
+		"previous_response_id":"resp_codex_image_lite",
+		"input":"draw a cat",
+		"tools":[{"type":"function","name":"image_gen.imagegen","parameters":{"type":"object"}}]
+	}`))
+	cancelWrite()
+	require.NoError(t, err)
+
+	readCtx, cancelRead = context.WithTimeout(context.Background(), 3*time.Second)
+	msgType, message, err = clientConn.Read(readCtx)
+	cancelRead()
+	require.NoError(t, err)
+	require.Equal(t, coderws.MessageText, msgType)
+	require.Equal(t, "resp_codex_image_function", gjson.GetBytes(message, "response.id").String())
+
 	_ = clientConn.Close(coderws.StatusNormalClosure, "done")
 
 	select {
@@ -557,7 +577,7 @@ func TestOpenAIGatewayService_ProxyResponsesWebSocketFromClient_CodexImageBridge
 		t.Fatal("等待 ingress websocket 结束超时")
 	}
 
-	require.Len(t, captureConn.writes, 2)
+	require.Len(t, captureConn.writes, 3)
 	nonLitePayload := requestToJSONString(captureConn.writes[0])
 	require.True(t, gjson.Get(nonLitePayload, `tools.#(type=="image_generation")`).Exists())
 	require.Equal(t, "png", gjson.Get(nonLitePayload, `tools.#(type=="image_generation").output_format`).String())
@@ -573,6 +593,12 @@ func TestOpenAIGatewayService_ProxyResponsesWebSocketFromClient_CodexImageBridge
 	require.Equal(t, "collaboration", gjson.Get(litePayload, `input.#(type=="additional_tools").tools.1.name`).String())
 	require.Equal(t, "namespace", gjson.Get(litePayload, "tool_choice.type").String())
 	require.Equal(t, "collaboration", gjson.Get(litePayload, "tool_choice.name").String())
+
+	functionPayload := requestToJSONString(captureConn.writes[2])
+	require.True(t, gjson.Get(functionPayload, `tools.#(name=="image_gen.imagegen")`).Exists())
+	require.False(t, gjson.Get(functionPayload, `tools.#(type=="image_generation")`).Exists())
+	require.False(t, gjson.Get(functionPayload, "tool_choice").Exists())
+	require.NotContains(t, gjson.Get(functionPayload, "instructions").String(), codexImageGenerationBridgeMarker)
 }
 
 func TestOpenAIGatewayService_ProxyResponsesWebSocketFromClient_DedicatedModeDoesNotReuseConnAcrossSessions(t *testing.T) {