fix(provider): preserve requested model in antigravity and sora

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent

)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

backend/internal/service/antigravity_gateway_service.go

@@ -1742,7 +1742,8 @@ func (s *AntigravityGatewayService) Forward(ctx context.Context, c *gin.Context,
 	return &ForwardResult{
 		RequestID:        requestID,
 		Usage:            *usage,
-		Model:            billingModel, // 使用映射模型用于计费和日志
+		Model:            originalModel,
+		UpstreamModel:    billingModel,
 		Stream:           claudeReq.Stream,
 		Duration:         time.Since(startTime),
 		FirstTokenMs:     firstTokenMs,
@@ -2435,7 +2436,8 @@ handleSuccess:
 	return &ForwardResult{
 		RequestID:        requestID,
 		Usage:            *usage,
-		Model:            billingModel,
+		Model:            originalModel,
+		UpstreamModel:    billingModel,
 		Stream:           stream,
 		Duration:         time.Since(startTime),
 		FirstTokenMs:     firstTokenMs,

backend/internal/service/antigravity_gateway_service_test.go

@@ -542,7 +542,8 @@ func TestAntigravityGatewayService_Forward_BillsWithMappedModel(t *testing.T) {
 	result, err := svc.Forward(context.Background(), c, account, body, false)
 	require.NoError(t, err)
 	require.NotNil(t, result)
-	require.Equal(t, mappedModel, result.Model)
+	require.Equal(t, "claude-sonnet-4-5", result.Model)
+	require.Equal(t, mappedModel, result.UpstreamModel)
 }
 
 // TestAntigravityGatewayService_ForwardGemini_BillsWithMappedModel
@@ -594,7 +595,8 @@ func TestAntigravityGatewayService_ForwardGemini_BillsWithMappedModel(t *testing
 	result, err := svc.ForwardGemini(context.Background(), c, account, "gemini-2.5-flash", "generateContent", true, body, false)
 	require.NoError(t, err)
 	require.NotNil(t, result)
-	require.Equal(t, mappedModel, result.Model)
+	require.Equal(t, "gemini-2.5-flash", result.Model)
+	require.Equal(t, mappedModel, result.UpstreamModel)
 }
 
 func TestAntigravityGatewayService_ForwardGemini_RetriesCorruptedThoughtSignature(t *testing.T) {
@@ -664,7 +666,8 @@ func TestAntigravityGatewayService_ForwardGemini_RetriesCorruptedThoughtSignatur
 	result, err := svc.ForwardGemini(context.Background(), c, account, originalModel, "streamGenerateContent", true, body, false)
 	require.NoError(t, err)
 	require.NotNil(t, result)
-	require.Equal(t, mappedModel, result.Model)
+	require.Equal(t, originalModel, result.Model)
+	require.Equal(t, mappedModel, result.UpstreamModel)
 	require.Len(t, upstream.requestBodies, 2, "signature error should trigger exactly one retry")
 
 	firstReq := string(upstream.requestBodies[0])

backend/internal/service/sora_gateway_service.go

@@ -148,10 +148,13 @@ func (s *SoraGatewayService) Forward(ctx context.Context, c *gin.Context, accoun
 		s.writeSoraError(c, http.StatusBadRequest, "invalid_request_error", "model is required", clientStream)
 		return nil, errors.New("model is required")
 	}
+	originalModel := reqModel
 
 	mappedModel := account.GetMappedModel(reqModel)
+	var upstreamModel string
 	if mappedModel != "" && mappedModel != reqModel {
 		reqModel = mappedModel
+		upstreamModel = mappedModel
 	}
 
 	modelCfg, ok := GetSoraModelConfig(reqModel)
@@ -214,7 +217,8 @@ func (s *SoraGatewayService) Forward(ctx context.Context, c *gin.Context, accoun
 		}
 		return &ForwardResult{
 			RequestID:     "",
-			Model:        reqModel,
+			Model:         originalModel,
+			UpstreamModel: upstreamModel,
 			Stream:        clientStream,
 			Duration:      time.Since(startTime),
 			FirstTokenMs:  firstTokenMs,
@@ -270,7 +274,8 @@ func (s *SoraGatewayService) Forward(ctx context.Context, c *gin.Context, accoun
 			}
 			return &ForwardResult{
 				RequestID:     "",
-				Model:        reqModel,
+				Model:         originalModel,
+				UpstreamModel: upstreamModel,
 				Stream:        clientStream,
 				Duration:      time.Since(startTime),
 				FirstTokenMs:  firstTokenMs,
@@ -420,7 +425,8 @@ func (s *SoraGatewayService) Forward(ctx context.Context, c *gin.Context, accoun
 
 	return &ForwardResult{
 		RequestID:     taskID,
-		Model:        reqModel,
+		Model:         originalModel,
+		UpstreamModel: upstreamModel,
 		Stream:        clientStream,
 		Duration:      time.Since(startTime),
 		FirstTokenMs:  firstTokenMs,

backend/internal/service/sora_gateway_service_test.go

@@ -144,6 +144,11 @@ func TestSoraGatewayService_ForwardPromptEnhance(t *testing.T) {
 		ID:       1,
 		Platform: PlatformSora,
 		Status:   StatusActive,
+		Credentials: map[string]any{
+			"model_mapping": map[string]any{
+				"prompt-enhance-short-10s": "prompt-enhance-short-15s",
+			},
+		},
 	}
 	body := []byte(`{"model":"prompt-enhance-short-10s","messages":[{"role":"user","content":"cat running"}],"stream":false}`)
 
@@ -152,6 +157,7 @@ func TestSoraGatewayService_ForwardPromptEnhance(t *testing.T) {
 	require.NotNil(t, result)
 	require.Equal(t, "prompt", result.MediaType)
 	require.Equal(t, "prompt-enhance-short-10s", result.Model)
+	require.Equal(t, "prompt-enhance-short-15s", result.UpstreamModel)
 }
 
 func TestSoraGatewayService_ForwardStoryboardPrompt(t *testing.T) {