diff --git a/backend/internal/service/image_generation_intent.go b/backend/internal/service/image_generation_intent.go
index 80b6c66d56..12590f3f63 100644
--- a/backend/internal/service/image_generation_intent.go
+++ b/backend/internal/service/image_generation_intent.go
@@ -39,6 +39,9 @@ func IsImageGenerationIntent(endpoint string, requestedModel string, body []byte
 	if openAIJSONToolsContainImageGeneration(gjson.GetBytes(body, "tools")) {
 		return true
 	}
+	if openAIJSONInputContainsImageGenTool(gjson.GetBytes(body, "input")) {
+		return true
+	}
 	return openAIJSONToolChoiceSelectsImageGeneration(gjson.GetBytes(body, "tool_choice"))
 }
 
@@ -94,11 +97,52 @@ func openAIJSONToolsContainImageGeneration(tools gjson.Result) bool {
 			found = true
 			return false
 		}
+		if isImageGenNamespaceTool(item) {
+			found = true
+			return false
+		}
 		return true
 	})
 	return found
 }
 
+// isImageGenNamespaceTool detects the Codex namespace-style image generation
+// tool declaration: { "type": "namespace", "name": "image_gen", ... }.
+// Codex /image uses this instead of the flat { "type": "image_generation" }.
+func isImageGenNamespaceTool(tool gjson.Result) bool {
+	return openAIJSONString(tool.Get("type")) == "namespace" &&
+		openAIJSONString(tool.Get("name")) == "image_gen"
+}
+
+// openAIJSONInputContainsImageGenTool scans Responses input items for
+// additional_tools entries that declare the image_gen namespace. This covers
+// the "Responses Lite" format where tools are embedded inside input items
+// rather than top-level tools.
+func openAIJSONInputContainsImageGenTool(input gjson.Result) bool {
+	if !input.IsArray() {
+		return false
+	}
+	found := false
+	input.ForEach(func(_, item gjson.Result) bool {
+		if openAIJSONString(item.Get("type")) != "additional_tools" {
+			return true
+		}
+		tools := item.Get("tools")
+		if !tools.IsArray() {
+			return true
+		}
+		tools.ForEach(func(_, tool gjson.Result) bool {
+			if isImageGenNamespaceTool(tool) {
+				found = true
+				return false
+			}
+			return true
+		})
+		return !found
+	})
+	return found
+}
+
 func openAIRequestBodyHasImageGenerationTool(body []byte) bool {
 	if len(body) == 0 || !gjson.ValidBytes(body) {
 		return false
diff --git a/backend/internal/service/image_generation_intent_test.go b/backend/internal/service/image_generation_intent_test.go
index 59aab39c4b..1a32318cce 100644
--- a/backend/internal/service/image_generation_intent_test.go
+++ b/backend/internal/service/image_generation_intent_test.go
@@ -55,6 +55,27 @@ func TestIsImageGenerationIntent(t *testing.T) {
 			body:     []byte(`{"model":"gpt-5.4","input":"write code"}`),
 			want:     false,
 		},
+		{
+			name:     "namespace image_gen tool in top-level tools",
+			endpoint: "/v1/responses",
+			model:    "gpt-5.5",
+			body:     []byte(`{"model":"gpt-5.5","tools":[{"type":"namespace","name":"image_gen","tools":[{"type":"function","name":"imagegen"}]}]}`),
+			want:     true,
+		},
+		{
+			name:     "namespace image_gen in input additional_tools (Responses Lite)",
+			endpoint: "/v1/responses",
+			model:    "gpt-5.5",
+			body:     []byte(`{"model":"gpt-5.5","input":[{"type":"additional_tools","role":"developer","tools":[{"type":"namespace","name":"image_gen","tools":[{"type":"function","name":"imagegen"}]}]}]}`),
+			want:     true,
+		},
+		{
+			name:     "non-image namespace tool is not flagged",
+			endpoint: "/v1/responses",
+			model:    "gpt-5.5",
+			body:     []byte(`{"model":"gpt-5.5","tools":[{"type":"namespace","name":"code_tools","tools":[{"type":"function","name":"run"}]}]}`),
+			want:     false,
+		},
 	}
 
 	for _, tt := range tests {
@@ -64,6 +85,58 @@ func TestIsImageGenerationIntent(t *testing.T) {
 	}
 }
 
+func TestIsImageGenerationIntentMap_NamespaceImageGen(t *testing.T) {
+	tests := []struct {
+		name    string
+		reqBody map[string]any
+		want    bool
+	}{
+		{
+			name: "top-level namespace image_gen",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"tools": []any{
+					map[string]any{"type": "namespace", "name": "image_gen", "tools": []any{
+						map[string]any{"type": "function", "name": "imagegen"},
+					}},
+				},
+			},
+			want: true,
+		},
+		{
+			name: "additional_tools in input",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"input": []any{
+					map[string]any{
+						"type": "additional_tools",
+						"tools": []any{
+							map[string]any{"type": "namespace", "name": "image_gen"},
+						},
+					},
+				},
+			},
+			want: true,
+		},
+		{
+			name: "non-image namespace not flagged",
+			reqBody: map[string]any{
+				"model": "gpt-5.5",
+				"tools": []any{
+					map[string]any{"type": "namespace", "name": "code_tools"},
+				},
+			},
+			want: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equal(t, tt.want, IsImageGenerationIntentMap("/v1/responses", "gpt-5.5", tt.reqBody))
+		})
+	}
+}
+
 func TestResolveOpenAIResponsesImageBillingConfigUsesCurrentBodyModel(t *testing.T) {
 	imageModel, imageSize, err := resolveOpenAIResponsesImageBillingConfigFromBody(
 		[]byte(`{"model":"mapped-image-model","tools":[{"type":"image_generation","size":"1024x1024"}]}`),
diff --git a/backend/internal/service/openai_codex_transform.go b/backend/internal/service/openai_codex_transform.go
index 44c420edbe..36426e7377 100644
--- a/backend/internal/service/openai_codex_transform.go
+++ b/backend/internal/service/openai_codex_transform.go
@@ -593,8 +593,14 @@ func isCodexSparkModel(model string) bool {
 }
 
 func hasOpenAIImageGenerationTool(reqBody map[string]any) bool {
-	rawTools, ok := reqBody["tools"]
-	if !ok || rawTools == nil {
+	if toolsContainImageGeneration(reqBody["tools"]) {
+		return true
+	}
+	return inputContainsImageGenNamespace(reqBody["input"])
+}
+
+func toolsContainImageGeneration(rawTools any) bool {
+	if rawTools == nil {
 		return false
 	}
 	tools, ok := rawTools.([]any)
@@ -609,6 +615,34 @@ func hasOpenAIImageGenerationTool(reqBody map[string]any) bool {
 		if strings.TrimSpace(firstNonEmptyString(toolMap["type"])) == "image_generation" {
 			return true
 		}
+		if isImageGenNamespaceToolMap(toolMap) {
+			return true
+		}
+	}
+	return false
+}
+
+func isImageGenNamespaceToolMap(tool map[string]any) bool {
+	return strings.TrimSpace(firstNonEmptyString(tool["type"])) == "namespace" &&
+		strings.TrimSpace(firstNonEmptyString(tool["name"])) == "image_gen"
+}
+
+func inputContainsImageGenNamespace(rawInput any) bool {
+	input, ok := rawInput.([]any)
+	if !ok {
+		return false
+	}
+	for _, rawItem := range input {
+		item, ok := rawItem.(map[string]any)
+		if !ok {
+			continue
+		}
+		if strings.TrimSpace(firstNonEmptyString(item["type"])) != "additional_tools" {
+			continue
+		}
+		if toolsContainImageGeneration(item["tools"]) {
+			return true
+		}
 	}
 	return false
 }