diff --git a/backend/internal/service/gateway_service_benchmark_test.go b/backend/internal/service/gateway_service_benchmark_test.go
index f6cd1404..42a711db 100644
--- a/backend/internal/service/gateway_service_benchmark_test.go
+++ b/backend/internal/service/gateway_service_benchmark_test.go
@@ -229,16 +229,16 @@ func benchmarkBodySizes() []struct {
 
 func buildSystemCacheableRequest(parts int) *ParsedRequest {
 	var builder strings.Builder
-	builder.WriteString(`{"system":[`)
+	_, _ = builder.WriteString(`{"system":[`)
 	for i := 0; i < parts; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteString(`{"text":"system_part_`)
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteString(`","cache_control":{"type":"ephemeral"}}`)
+		_, _ = builder.WriteString(`{"text":"system_part_`)
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_, _ = builder.WriteString(`","cache_control":{"type":"ephemeral"}}`)
 	}
-	builder.WriteString(`]}`)
+	_, _ = builder.WriteString(`]}`)
 	parsed, err := ParseGatewayRequest(NewRequestBodyRef([]byte(builder.String())), "")
 	if err != nil {
 		panic(err)
@@ -249,93 +249,93 @@ func buildSystemCacheableRequest(parts int) *ParsedRequest {
 func buildLargeAnthropicMessagesBody(targetBytes int, includeCacheControl bool) []byte {
 	var builder strings.Builder
 	builder.Grow(targetBytes + 1024)
-	builder.WriteString(`{"model":"claude-sonnet-4-5","stream":true,"system":[{"type":"text","text":"system seed"}],"messages":[`)
+	_, _ = builder.WriteString(`{"model":"claude-sonnet-4-5","stream":true,"system":[{"type":"text","text":"system seed"}],"messages":[`)
 	for i := 0; builder.Len() < targetBytes; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteString(`{"role":"user","content":[{"type":"text","text":"`)
-		builder.WriteString(strings.Repeat("anthropic payload ", 64))
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteByte('"')
+		_, _ = builder.WriteString(`{"role":"user","content":[{"type":"text","text":"`)
+		_, _ = builder.WriteString(strings.Repeat("anthropic payload ", 64))
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_ = builder.WriteByte('"')
 		if includeCacheControl && i%32 == 0 {
-			builder.WriteString(`,"cache_control":{"type":"ephemeral"}`)
+			_, _ = builder.WriteString(`,"cache_control":{"type":"ephemeral"}`)
 		}
-		builder.WriteString(`}]}`)
+		_, _ = builder.WriteString(`}]}`)
 	}
-	builder.WriteString(`]}`)
+	_, _ = builder.WriteString(`]}`)
 	return []byte(builder.String())
 }
 
 func buildLargeGeminiContentsBody(targetBytes int) []byte {
 	var builder strings.Builder
 	builder.Grow(targetBytes + 1024)
-	builder.WriteString(`{"model":"gemini-2.5-pro","systemInstruction":{"parts":[{"text":"system seed"}]},"contents":[`)
+	_, _ = builder.WriteString(`{"model":"gemini-2.5-pro","systemInstruction":{"parts":[{"text":"system seed"}]},"contents":[`)
 	for i := 0; builder.Len() < targetBytes; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteString(`{"role":"user","parts":[{"text":"`)
-		builder.WriteString(strings.Repeat("gemini payload ", 64))
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteString(`"}]}`)
+		_, _ = builder.WriteString(`{"role":"user","parts":[{"text":"`)
+		_, _ = builder.WriteString(strings.Repeat("gemini payload ", 64))
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_, _ = builder.WriteString(`"}]}`)
 	}
-	builder.WriteString(`]}`)
+	_, _ = builder.WriteString(`]}`)
 	return []byte(builder.String())
 }
 
 func buildLargeOpenAIResponsesBody(targetBytes int) []byte {
 	var builder strings.Builder
 	builder.Grow(targetBytes + 1024)
-	builder.WriteString(`{"model":"gpt-5.4","stream":true,"prompt_cache_key":"session-benchmark","input":[`)
+	_, _ = builder.WriteString(`{"model":"gpt-5.4","stream":true,"prompt_cache_key":"session-benchmark","input":[`)
 	for i := 0; builder.Len() < targetBytes; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteString(`{"type":"message","role":"user","content":[{"type":"input_text","text":"`)
-		builder.WriteString(strings.Repeat("openai responses payload ", 48))
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteString(`"}]}`)
+		_, _ = builder.WriteString(`{"type":"message","role":"user","content":[{"type":"input_text","text":"`)
+		_, _ = builder.WriteString(strings.Repeat("openai responses payload ", 48))
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_, _ = builder.WriteString(`"}]}`)
 	}
-	builder.WriteString(`],"tools":[{"type":"function","name":"lookup","parameters":{"type":"object","properties":{"query":{"type":"string"}}}}]}`)
+	_, _ = builder.WriteString(`],"tools":[{"type":"function","name":"lookup","parameters":{"type":"object","properties":{"query":{"type":"string"}}}}]}`)
 	return []byte(builder.String())
 }
 
 func buildLargeOpenAIResponsesToolContinuationBody(targetBytes int) []byte {
 	var builder strings.Builder
 	builder.Grow(targetBytes + 1024)
-	builder.WriteString(`{"model":"gpt-5.4","stream":true,"previous_response_id":"resp_benchmark","input":[`)
+	_, _ = builder.WriteString(`{"model":"gpt-5.4","stream":true,"previous_response_id":"resp_benchmark","input":[`)
 	for i := 0; builder.Len() < targetBytes; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
 		callID := "call_" + strconv.Itoa(i)
-		builder.WriteString(`{"type":"item_reference","id":"`)
-		builder.WriteString(callID)
-		builder.WriteString(`"},{"type":"function_call_output","call_id":"`)
-		builder.WriteString(callID)
-		builder.WriteString(`","output":"`)
-		builder.WriteString(strings.Repeat("tool output payload ", 48))
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteString(`"}`)
+		_, _ = builder.WriteString(`{"type":"item_reference","id":"`)
+		_, _ = builder.WriteString(callID)
+		_, _ = builder.WriteString(`"},{"type":"function_call_output","call_id":"`)
+		_, _ = builder.WriteString(callID)
+		_, _ = builder.WriteString(`","output":"`)
+		_, _ = builder.WriteString(strings.Repeat("tool output payload ", 48))
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_, _ = builder.WriteString(`"}`)
 	}
-	builder.WriteString(`]}`)
+	_, _ = builder.WriteString(`]}`)
 	return []byte(builder.String())
 }
 
 func buildLargeOpenAIResponsesImageToolBody(targetBytes int) []byte {
 	var builder strings.Builder
 	builder.Grow(targetBytes + 1024)
-	builder.WriteString(`{"model":"gpt-5.4","stream":false,"tools":[{"type":"image_generation","model":"gpt-image-2","size":"2048x1152"}],"input":[`)
+	_, _ = builder.WriteString(`{"model":"gpt-5.4","stream":false,"tools":[{"type":"image_generation","model":"gpt-image-2","size":"2048x1152"}],"input":[`)
 	for i := 0; builder.Len() < targetBytes; i++ {
 		if i > 0 {
-			builder.WriteByte(',')
+			_ = builder.WriteByte(',')
 		}
-		builder.WriteString(`{"type":"message","role":"user","content":[{"type":"input_text","text":"`)
-		builder.WriteString(strings.Repeat("openai image billing payload ", 48))
-		builder.WriteString(strconv.Itoa(i))
-		builder.WriteString(`"}]}`)
+		_, _ = builder.WriteString(`{"type":"message","role":"user","content":[{"type":"input_text","text":"`)
+		_, _ = builder.WriteString(strings.Repeat("openai image billing payload ", 48))
+		_, _ = builder.WriteString(strconv.Itoa(i))
+		_, _ = builder.WriteString(`"}]}`)
 	}
-	builder.WriteString(`]}`)
+	_, _ = builder.WriteString(`]}`)
 	return []byte(builder.String())
 }
diff --git a/backend/internal/service/openai_gateway_service.go b/backend/internal/service/openai_gateway_service.go
index d17b85d0..8fd4bc60 100644
--- a/backend/internal/service/openai_gateway_service.go
+++ b/backend/internal/service/openai_gateway_service.go
@@ -2544,6 +2544,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 			logger.LegacyPrintf("service.openai_gateway", "[OpenAI] Added Codex image_generation bridge instructions")
 		}
 	} else if imageGenerationAllowed && imageIntent && openAIRequestBodyHasImageGenerationTool(body) {
+		// 完整 image_generation tool 只做 raw 计费读取，校验/桥接/旧字段迁移命中时才展开大 input map。
 		logger.LegacyPrintf("service.openai_gateway", "[OpenAI] /responses image_generation request inbound_model=%s mapped_model=%s account_type=%s", requestView.Model, upstreamModel, account.Type)
 	}
 
@@ -6215,7 +6216,7 @@ func (v *openAIRequestView) MarkPatchSet(path string, value any) {
 		return
 	}
 	path = strings.TrimSpace(path)
-	if path == "" {
+	if !isSimpleOpenAIRequestPatchPath(path) {
 		v.DisablePatches()
 		return
 	}
@@ -6227,13 +6228,25 @@ func (v *openAIRequestView) MarkPatchDelete(path string) {
 		return
 	}
 	path = strings.TrimSpace(path)
-	if path == "" {
+	if !isSimpleOpenAIRequestPatchPath(path) {
 		v.DisablePatches()
 		return
 	}
 	v.patches = append(v.patches, openAIRequestPatch{path: path, delete: true})
 }
 
+func isSimpleOpenAIRequestPatchPath(path string) bool {
+	if path == "" || strings.ContainsRune(path, '\\') {
+		return false
+	}
+	for _, part := range strings.Split(path, ".") {
+		if strings.TrimSpace(part) == "" {
+			return false
+		}
+	}
+	return true
+}
+
 func (v *openAIRequestView) DisablePatches() {
 	if v == nil {
 		return
@@ -6772,7 +6785,7 @@ func openAIRequestBodyMayContainImageInput(body []byte) bool {
 		return false
 	}
 	input := gjson.GetBytes(body, "input")
-	messages := gjson.GetBytes(body, "messages")
+	messages := gjson.GetBytes(body, "messages.#-1")
 	return openAIJSONValueMayContainImageInput(input) || openAIJSONValueMayContainImageInput(messages)
 }
 
diff --git a/backend/internal/service/openai_gateway_service_hotpath_test.go b/backend/internal/service/openai_gateway_service_hotpath_test.go
index d240cec8..92a0d1ac 100644
--- a/backend/internal/service/openai_gateway_service_hotpath_test.go
+++ b/backend/internal/service/openai_gateway_service_hotpath_test.go
@@ -46,6 +46,15 @@ func TestOpenAIRequestView_ApplyPatches(t *testing.T) {
 	require.JSONEq(t, `{"model":"gpt-5.1","reasoning":{"effort":"none"},"input":[{"type":"message","content":"hi"}]}`, string(patched))
 }
 
+func TestOpenAIRequestView_RejectsEscapedPatchPath(t *testing.T) {
+	view := newOpenAIRequestView([]byte(`{"metadata":{"user.id":"old"}}`))
+	view.MarkPatchSet(`metadata.user\.id`, "new")
+
+	require.False(t, view.HasPatches())
+	_, err := view.ApplyPatches()
+	require.Error(t, err)
+}
+
 func TestOpenAIRequestView_ApplyPatchesDisabled(t *testing.T) {
 	view := newOpenAIRequestView([]byte(`{"model":"gpt-5"}`))
 	view.MarkPatchSet("model", "gpt-5.1")
@@ -260,6 +269,42 @@ func TestOpenAIGatewayService_Forward_ImageToolBillingDoesNotForceFullDecode(t *
 	require.Equal(t, "gpt-image-2", result.BillingModel)
 }
 
+func TestOpenAIGatewayService_Forward_ImageToolWithImageOnlyModelIsNormalized(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	upstream := &httpUpstreamRecorder{
+		resp: &http.Response{
+			StatusCode: http.StatusOK,
+			Header:     http.Header{"Content-Type": []string{"application/json"}},
+			Body:       io.NopCloser(strings.NewReader(`{"usage":{"input_tokens":1,"output_tokens":2}}`)),
+		},
+	}
+	cfg := &config.Config{}
+	cfg.Security.URLAllowlist.Enabled = false
+	svc := &OpenAIGatewayService{cfg: cfg, httpUpstream: upstream}
+	account := &Account{
+		ID:          11,
+		Name:        "openai-apikey",
+		Platform:    PlatformOpenAI,
+		Type:        AccountTypeAPIKey,
+		Concurrency: 1,
+		Credentials: map[string]any{
+			"api_key":  "sk-test",
+			"base_url": "https://example.com",
+		},
+		Extra: map[string]any{"use_responses_api": true},
+	}
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/openai/v1/responses", nil)
+	SetOpenAIClientTransport(c, OpenAIClientTransportHTTP)
+
+	body := []byte(`{"model":"gpt-image-2","stream":false,"tools":[{"type":"image_generation","model":"gpt-image-2"}],"input":"draw"}`)
+	result, err := svc.Forward(context.Background(), c, account, body)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, openAIImagesResponsesMainModel, gjson.GetBytes(upstream.lastBody, "model").String())
+}
+
 func TestOpenAIGatewayService_Forward_HTTPRetryRecoveryDoesNotDecodeBeforeError(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 	upstream := &httpUpstreamRecorder{
diff --git a/backend/internal/service/openai_tool_continuation.go b/backend/internal/service/openai_tool_continuation.go
index 92bc2613..6515c0c4 100644
--- a/backend/internal/service/openai_tool_continuation.go
+++ b/backend/internal/service/openai_tool_continuation.go
@@ -199,7 +199,7 @@ func ValidateFunctionCallOutputContextBytes(body []byte) FunctionCallOutputValid
 			}
 			referenceIDs[idValue] = struct{}{}
 		}
-		return !(result.HasFunctionCallOutput && result.HasToolCallContext)
+		return !result.HasFunctionCallOutput || !result.HasToolCallContext
 	})
 	if !result.HasFunctionCallOutput || result.HasToolCallContext || len(callIDs) == 0 || len(referenceIDs) == 0 {
 		return result