fix: allow composite grok messages routing

backend/internal/handler/composite_platform_test.go

@@ -22,6 +22,18 @@ func TestCompositeTargetPlatformAllowedResolvesKnownAllowedModel(t *testing.T) {
 	require.Equal(t, service.PlatformOpenAI, platform)
 }
 
+func TestOpenAICompatibleMessagesTargetAllowsCompositeGrokModel(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	c, _ := gin.CreateTestContext(httptest.NewRecorder())
+	c.Request = httptest.NewRequest("POST", "/v1/messages", nil)
+	apiKey := &service.APIKey{Group: &service.Group{Platform: service.PlatformComposite}}
+
+	require.True(t, openAICompatibleMessagesTargetAllowed(c, apiKey, "grok-4.3"))
+	platform, ok := service.ResolvedTargetPlatformFromContext(c.Request.Context())
+	require.True(t, ok)
+	require.Equal(t, service.PlatformGrok, platform)
+}
+
 func TestCompositeTargetPlatformAllowedRejectsWrongOrUnknownModel(t *testing.T) {
 	gin.SetMode(gin.TestMode)
 

backend/internal/handler/openai_gateway_handler.go

@@ -147,6 +147,10 @@ func allowOpenAICompatibleMessagesDispatch(apiKey *service.APIKey) bool {
 	return apiKey.Group.AllowMessagesDispatch
 }
 
+func openAICompatibleMessagesTargetAllowed(c *gin.Context, apiKey *service.APIKey, model string) bool {
+	return compositeTargetPlatformAllowed(c, apiKey, model, service.PlatformOpenAI, service.PlatformGrok)
+}
+
 // NewOpenAIGatewayHandler creates a new OpenAIGatewayHandler
 func NewOpenAIGatewayHandler(
 	gatewayService *service.OpenAIGatewayService,
@@ -873,7 +877,7 @@ func (h *OpenAIGatewayHandler) Messages(c *gin.Context) {
 	}
 	reqModel := modelResult.String()
 	ensureCompositeTargetPlatform(c, apiKey, reqModel)
-	if !compositeTargetPlatformAllowed(c, apiKey, reqModel, service.PlatformOpenAI) {
+	if !openAICompatibleMessagesTargetAllowed(c, apiKey, reqModel) {
 		h.anthropicErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Model is not supported by this OpenAI-compatible endpoint for composite groups")
 		return
 	}

backend/internal/server/routes/gateway_test.go

@@ -193,6 +193,21 @@ func TestGatewayRoutesCompositeVideoStatusUsesGrokHandler(t *testing.T) {
 	}
 }
 
+func TestGatewayRoutesCompositeMessagesWithGrokModelUsesOpenAIGateway(t *testing.T) {
+	router := newGatewayRoutesTestRouter(service.PlatformComposite)
+
+	req := httptest.NewRequest(http.MethodPost, "/v1/messages", strings.NewReader(`{"model":"grok-4.3","messages":[{"role":"user","content":"hi"}]}`))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+
+	router.ServeHTTP(w, req)
+
+	require.NotEqual(t, http.StatusNotFound, w.Code)
+	require.NotContains(t, w.Body.String(), "not supported")
+	require.NotContains(t, w.Body.String(), "OpenAI-compatible endpoint")
+	require.NotContains(t, w.Body.String(), "composite groups")
+}
+
 func TestGatewayRoutesNonGrokVideosAreRejectedAtPlatformGate(t *testing.T) {
 	router := newGatewayRoutesTestRouter(service.PlatformOpenAI)