feat(service): record upstream model across all gateway paths

Propagate UpstreamModel through ForwardResult and OpenAIForwardResult in Anthropic direct, API-key passthrough, Bedrock, and OpenAI gateway flows. Extract optionalNonEqualStringPtr and optionalTrimmedStringPtr into usage_log_helpers.go. Store upstream_model only when it differs from the requested model.

Also introduces anthropicPassthroughForwardInput struct to reduce parameter count.

backend/internal/service/gateway_service.go

@@ -491,6 +491,7 @@ type ForwardResult struct {
 	RequestID        string
 	Usage            ClaudeUsage
 	Model            string
+	UpstreamModel    string // Actual upstream model after mapping (empty = no mapping)
 	Stream           bool
 	Duration         time.Duration
 	FirstTokenMs     *int // 首字时间（流式请求）
@@ -3989,7 +3990,13 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 				passthroughModel = mappedModel
 			}
 		}
-		return s.forwardAnthropicAPIKeyPassthrough(ctx, c, account, passthroughBody, passthroughModel, parsed.Stream, startTime)
+		return s.forwardAnthropicAPIKeyPassthroughWithInput(ctx, c, account, anthropicPassthroughForwardInput{
+			Body:          passthroughBody,
+			RequestModel:  passthroughModel,
+			OriginalModel: parsed.Model,
+			RequestStream: parsed.Stream,
+			StartTime:     startTime,
+		})
 	}
 
 	if account != nil && account.IsBedrock() {
@@ -4513,6 +4520,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		RequestID:        resp.Header.Get("x-request-id"),
 		Usage:            *usage,
 		Model:            originalModel, // 使用原始模型用于计费和日志
+		UpstreamModel:    mappedModel,
 		Stream:           reqStream,
 		Duration:         time.Since(startTime),
 		FirstTokenMs:     firstTokenMs,
@@ -4520,14 +4528,38 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	}, nil
 }
 
+type anthropicPassthroughForwardInput struct {
+	Body          []byte
+	RequestModel  string
+	OriginalModel string
+	RequestStream bool
+	StartTime     time.Time
+}
+
 func (s *GatewayService) forwardAnthropicAPIKeyPassthrough(
 	ctx context.Context,
 	c *gin.Context,
 	account *Account,
 	body []byte,
 	reqModel string,
+	originalModel string,
 	reqStream bool,
 	startTime time.Time,
+) (*ForwardResult, error) {
+	return s.forwardAnthropicAPIKeyPassthroughWithInput(ctx, c, account, anthropicPassthroughForwardInput{
+		Body:          body,
+		RequestModel:  reqModel,
+		OriginalModel: originalModel,
+		RequestStream: reqStream,
+		StartTime:     startTime,
+	})
+}
+
+func (s *GatewayService) forwardAnthropicAPIKeyPassthroughWithInput(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	input anthropicPassthroughForwardInput,
 ) (*ForwardResult, error) {
 	token, tokenType, err := s.GetAccessToken(ctx, account)
 	if err != nil {
@@ -4543,19 +4575,19 @@ func (s *GatewayService) forwardAnthropicAPIKeyPassthrough(
 	}
 
 	logger.LegacyPrintf("service.gateway", "[Anthropic 自动透传] 命中 API Key 透传分支: account=%d name=%s model=%s stream=%v",
-		account.ID, account.Name, reqModel, reqStream)
+		account.ID, account.Name, input.RequestModel, input.RequestStream)
 
 	if c != nil {
 		c.Set("anthropic_passthrough", true)
 	}
 	// 重试间复用同一请求体，避免每次 string(body) 产生额外分配。
-	setOpsUpstreamRequestBody(c, body)
+	setOpsUpstreamRequestBody(c, input.Body)
 
 	var resp *http.Response
 	retryStart := time.Now()
 	for attempt := 1; attempt <= maxRetryAttempts; attempt++ {
-		upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, reqStream)
+		upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, input.RequestStream)
-		upstreamReq, err := s.buildUpstreamRequestAnthropicAPIKeyPassthrough(upstreamCtx, c, account, body, token)
+		upstreamReq, err := s.buildUpstreamRequestAnthropicAPIKeyPassthrough(upstreamCtx, c, account, input.Body, token)
 		releaseUpstreamCtx()
 		if err != nil {
 			return nil, err
@@ -4713,8 +4745,8 @@ func (s *GatewayService) forwardAnthropicAPIKeyPassthrough(
 	var usage *ClaudeUsage
 	var firstTokenMs *int
 	var clientDisconnect bool
-	if reqStream {
+	if input.RequestStream {
-		streamResult, err := s.handleStreamingResponseAnthropicAPIKeyPassthrough(ctx, resp, c, account, startTime, reqModel)
+		streamResult, err := s.handleStreamingResponseAnthropicAPIKeyPassthrough(ctx, resp, c, account, input.StartTime, input.RequestModel)
 		if err != nil {
 			return nil, err
 		}
@@ -4734,9 +4766,10 @@ func (s *GatewayService) forwardAnthropicAPIKeyPassthrough(
 	return &ForwardResult{
 		RequestID:        resp.Header.Get("x-request-id"),
 		Usage:            *usage,
-		Model:            reqModel,
+		Model:            input.OriginalModel,
-		Stream:           reqStream,
+		UpstreamModel:    input.RequestModel,
-		Duration:         time.Since(startTime),
+		Stream:           input.RequestStream,
+		Duration:         time.Since(input.StartTime),
 		FirstTokenMs:     firstTokenMs,
 		ClientDisconnect: clientDisconnect,
 	}, nil
@@ -5241,6 +5274,7 @@ func (s *GatewayService) forwardBedrock(
 		RequestID:        resp.Header.Get("x-amzn-requestid"),
 		Usage:            *usage,
 		Model:            reqModel,
+		UpstreamModel:    mappedModel,
 		Stream:           reqStream,
 		Duration:         time.Since(startTime),
 		FirstTokenMs:     firstTokenMs,
@@ -7529,6 +7563,7 @@ func (s *GatewayService) RecordUsage(ctx context.Context, input *RecordUsageInpu
 		AccountID:             account.ID,
 		RequestID:             requestID,
 		Model:                 result.Model,
+		UpstreamModel:         optionalNonEqualStringPtr(result.UpstreamModel, result.Model),
 		ReasoningEffort:       result.ReasoningEffort,
 		InboundEndpoint:       optionalTrimmedStringPtr(input.InboundEndpoint),
 		UpstreamEndpoint:      optionalTrimmedStringPtr(input.UpstreamEndpoint),
@@ -7710,6 +7745,7 @@ func (s *GatewayService) RecordUsageWithLongContext(ctx context.Context, input *
 		AccountID:             account.ID,
 		RequestID:             requestID,
 		Model:                 result.Model,
+		UpstreamModel:         optionalNonEqualStringPtr(result.UpstreamModel, result.Model),
 		ReasoningEffort:       result.ReasoningEffort,
 		InboundEndpoint:       optionalTrimmedStringPtr(input.InboundEndpoint),
 		UpstreamEndpoint:      optionalTrimmedStringPtr(input.UpstreamEndpoint),

backend/internal/service/openai_gateway_chat_completions.go

@@ -281,6 +281,7 @@ func (s *OpenAIGatewayService) handleChatBufferedStreamingResponse(
 		Usage:         usage,
 		Model:         originalModel,
 		BillingModel:  mappedModel,
+		UpstreamModel: mappedModel,
 		Stream:        false,
 		Duration:      time.Since(startTime),
 	}, nil
@@ -328,6 +329,7 @@ func (s *OpenAIGatewayService) handleChatStreamingResponse(
 			Usage:         usage,
 			Model:         originalModel,
 			BillingModel:  mappedModel,
+			UpstreamModel: mappedModel,
 			Stream:        true,
 			Duration:      time.Since(startTime),
 			FirstTokenMs:  firstTokenMs,

backend/internal/service/openai_gateway_messages.go

@@ -303,6 +303,7 @@ func (s *OpenAIGatewayService) handleAnthropicBufferedStreamingResponse(
 		Usage:         usage,
 		Model:         originalModel,
 		BillingModel:  mappedModel,
+		UpstreamModel: mappedModel,
 		Stream:        false,
 		Duration:      time.Since(startTime),
 	}, nil
@@ -351,6 +352,7 @@ func (s *OpenAIGatewayService) handleAnthropicStreamingResponse(
 			Usage:         usage,
 			Model:         originalModel,
 			BillingModel:  mappedModel,
+			UpstreamModel: mappedModel,
 			Stream:        true,
 			Duration:      time.Since(startTime),
 			FirstTokenMs:  firstTokenMs,

backend/internal/service/openai_gateway_service.go

@@ -216,6 +216,9 @@ type OpenAIForwardResult struct {
 	// This is set by the Anthropic Messages conversion path where
 	// the mapped upstream model differs from the client-facing model.
 	BillingModel string
+	// UpstreamModel is the actual model sent to the upstream provider after mapping.
+	// Empty when no mapping was applied (requested model was used as-is).
+	UpstreamModel string
 	// ServiceTier records the OpenAI Responses API service tier, e.g. "priority" / "flex".
 	// Nil means the request did not specify a recognized tier.
 	ServiceTier *string
@@ -2128,6 +2131,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 				firstTokenMs,
 				wsAttempts,
 			)
+			wsResult.UpstreamModel = mappedModel
 			return wsResult, nil
 		}
 		s.writeOpenAIWSFallbackErrorResponse(c, account, wsErr)
@@ -2263,6 +2267,7 @@ func (s *OpenAIGatewayService) Forward(ctx context.Context, c *gin.Context, acco
 			RequestID:       resp.Header.Get("x-request-id"),
 			Usage:           *usage,
 			Model:           originalModel,
+			UpstreamModel:   mappedModel,
 			ServiceTier:     serviceTier,
 			ReasoningEffort: reasoningEffort,
 			Stream:          reqStream,
@@ -4134,7 +4139,8 @@ func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRec
 		APIKeyID:              apiKey.ID,
 		AccountID:             account.ID,
 		RequestID:             requestID,
-		Model:                 billingModel,
+		Model:                 result.Model,
+		UpstreamModel:         optionalNonEqualStringPtr(result.UpstreamModel, result.Model),
 		ServiceTier:           result.ServiceTier,
 		ReasoningEffort:       result.ReasoningEffort,
 		InboundEndpoint:       optionalTrimmedStringPtr(input.InboundEndpoint),
@@ -4700,11 +4706,3 @@ func normalizeOpenAIReasoningEffort(raw string) string {
 		return ""
 	}
 }
-
-func optionalTrimmedStringPtr(raw string) *string {
-	trimmed := strings.TrimSpace(raw)
-	if trimmed == "" {
-		return nil
-	}
-	return &trimmed
-}

backend/internal/service/usage_log.go

@@ -98,6 +98,9 @@ type UsageLog struct {
 	AccountID int64
 	RequestID string
 	Model     string
+	// UpstreamModel is the actual model sent to the upstream provider after mapping.
+	// Nil means no mapping was applied (requested model was used as-is).
+	UpstreamModel *string
 	// ServiceTier records the OpenAI service tier used for billing, e.g. "priority" / "flex".
 	ServiceTier *string
 	// ReasoningEffort is the request's reasoning effort level.

backend/internal/service/usage_log_helpers.go

@@ -0,0 +1,21 @@
+package service
+
+import "strings"
+
+func optionalTrimmedStringPtr(raw string) *string {
+	trimmed := strings.TrimSpace(raw)
+	if trimmed == "" {
+		return nil
+	}
+	return &trimmed
+}
+
+// optionalNonEqualStringPtr returns a pointer to value if it is non-empty and
+// differs from compare; otherwise nil. Used to store upstream_model only when
+// it differs from the requested model.
+func optionalNonEqualStringPtr(value, compare string) *string {
+	if value == "" || value == compare {
+		return nil
+	}
+	return &value
+}