feat(anthropic): 支持 API Key 自动透传并优化透传链路性能

- 新增 Anthropic API Key 自动透传开关与后端透传分支（仅替换认证）

- 账号编辑页新增自动透传开关，默认关闭

- 优化透传性能：SSE usage 解析 gjson 快路径、减少请求体重复拷贝、优化流式写回与非流式 usage 解析

- 补充单元测试与 benchmark，确保 Claude OAuth 路径不受影响

backend/internal/service/gateway_service.go

@@ -3041,6 +3041,10 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		return nil, fmt.Errorf("parse request: empty request")
 	}
 
+	if account != nil && account.IsAnthropicAPIKeyPassthroughEnabled() {
+		return s.forwardAnthropicAPIKeyPassthrough(ctx, c, account, parsed.Body, parsed.Model, parsed.Stream, startTime)
+	}
+
 	body := parsed.Body
 	reqModel := parsed.Model
 	reqStream := parsed.Stream
@@ -3120,14 +3124,14 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	// 调试日志：记录即将转发的账号信息
 	logger.LegacyPrintf("service.gateway", "[Forward] Using account: ID=%d Name=%s Platform=%s Type=%s TLSFingerprint=%v Proxy=%s",
 		account.ID, account.Name, account.Platform, account.Type, account.IsTLSFingerprintEnabled(), proxyURL)
+	// 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)
 
 	// 重试循环
 	var resp *http.Response
 	retryStart := time.Now()
 	for attempt := 1; attempt <= maxRetryAttempts; attempt++ {
 		// 构建上游请求（每次重试需要重新构建，因为请求体需要重新读取）
-		// Capture upstream request body for ops retry of this attempt.
-		c.Set(OpsUpstreamRequestBodyKey, string(body))
 		upstreamReq, err := s.buildUpstreamRequest(ctx, c, account, body, token, tokenType, reqModel, reqStream, shouldMimicClaudeCode)
 		if err != nil {
 			return nil, err
@@ -3491,6 +3495,538 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 	}, nil
 }
 
+func (s *GatewayService) forwardAnthropicAPIKeyPassthrough(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	body []byte,
+	reqModel string,
+	reqStream bool,
+	startTime time.Time,
+) (*ForwardResult, error) {
+	token, tokenType, err := s.GetAccessToken(ctx, account)
+	if err != nil {
+		return nil, err
+	}
+	if tokenType != "apikey" {
+		return nil, fmt.Errorf("anthropic api key passthrough requires apikey token, got: %s", tokenType)
+	}
+
+	proxyURL := ""
+	if account.ProxyID != nil && account.Proxy != nil {
+		proxyURL = account.Proxy.URL()
+	}
+
+	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)
+
+	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)
+
+	var resp *http.Response
+	retryStart := time.Now()
+	for attempt := 1; attempt <= maxRetryAttempts; attempt++ {
+		upstreamReq, err := s.buildUpstreamRequestAnthropicAPIKeyPassthrough(ctx, c, account, body, token)
+		if err != nil {
+			return nil, err
+		}
+
+		resp, err = s.httpUpstream.DoWithTLS(upstreamReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
+		if err != nil {
+			if resp != nil && resp.Body != nil {
+				_ = resp.Body.Close()
+			}
+			safeErr := sanitizeUpstreamErrorMessage(err.Error())
+			setOpsUpstreamError(c, 0, safeErr, "")
+			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+				Platform:           account.Platform,
+				AccountID:          account.ID,
+				AccountName:        account.Name,
+				UpstreamStatusCode: 0,
+				Passthrough:        true,
+				Kind:               "request_error",
+				Message:            safeErr,
+			})
+			c.JSON(http.StatusBadGateway, gin.H{
+				"type": "error",
+				"error": gin.H{
+					"type":    "upstream_error",
+					"message": "Upstream request failed",
+				},
+			})
+			return nil, fmt.Errorf("upstream request failed: %s", safeErr)
+		}
+
+		// 透传分支禁止 400 请求体降级重试（该重试会改写请求体）
+		if resp.StatusCode >= 400 && resp.StatusCode != 400 && s.shouldRetryUpstreamError(account, resp.StatusCode) {
+			if attempt < maxRetryAttempts {
+				elapsed := time.Since(retryStart)
+				if elapsed >= maxRetryElapsed {
+					break
+				}
+
+				delay := retryBackoffDelay(attempt)
+				remaining := maxRetryElapsed - elapsed
+				if delay > remaining {
+					delay = remaining
+				}
+				if delay <= 0 {
+					break
+				}
+
+				respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+				_ = resp.Body.Close()
+				appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+					Platform:           account.Platform,
+					AccountID:          account.ID,
+					AccountName:        account.Name,
+					UpstreamStatusCode: resp.StatusCode,
+					UpstreamRequestID:  resp.Header.Get("x-request-id"),
+					Passthrough:        true,
+					Kind:               "retry",
+					Message:            extractUpstreamErrorMessage(respBody),
+					Detail: func() string {
+						if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+							return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
+						}
+						return ""
+					}(),
+				})
+				logger.LegacyPrintf("service.gateway", "Anthropic passthrough account %d: upstream error %d, retry %d/%d after %v (elapsed=%v/%v)",
+					account.ID, resp.StatusCode, attempt, maxRetryAttempts, delay, elapsed, maxRetryElapsed)
+				if err := sleepWithContext(ctx, delay); err != nil {
+					return nil, err
+				}
+				continue
+			}
+			break
+		}
+
+		break
+	}
+	if resp == nil || resp.Body == nil {
+		return nil, errors.New("upstream request failed: empty response")
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode >= 400 && s.shouldRetryUpstreamError(account, resp.StatusCode) {
+		if s.shouldFailoverUpstreamError(resp.StatusCode) {
+			respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+			_ = resp.Body.Close()
+			resp.Body = io.NopCloser(bytes.NewReader(respBody))
+
+			logger.LegacyPrintf("service.gateway", "[Anthropic Passthrough] Upstream error (retry exhausted, failover): Account=%d(%s) Status=%d RequestID=%s Body=%s",
+				account.ID, account.Name, resp.StatusCode, resp.Header.Get("x-request-id"), truncateString(string(respBody), 1000))
+
+			s.handleRetryExhaustedSideEffects(ctx, resp, account)
+			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+				Platform:           account.Platform,
+				AccountID:          account.ID,
+				AccountName:        account.Name,
+				UpstreamStatusCode: resp.StatusCode,
+				UpstreamRequestID:  resp.Header.Get("x-request-id"),
+				Passthrough:        true,
+				Kind:               "retry_exhausted_failover",
+				Message:            extractUpstreamErrorMessage(respBody),
+				Detail: func() string {
+					if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+						return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
+					}
+					return ""
+				}(),
+			})
+			return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: respBody}
+		}
+		return s.handleRetryExhaustedError(ctx, resp, c, account)
+	}
+
+	if resp.StatusCode >= 400 && s.shouldFailoverUpstreamError(resp.StatusCode) {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+		_ = resp.Body.Close()
+		resp.Body = io.NopCloser(bytes.NewReader(respBody))
+
+		logger.LegacyPrintf("service.gateway", "[Anthropic Passthrough] Upstream error (failover): Account=%d(%s) Status=%d RequestID=%s Body=%s",
+			account.ID, account.Name, resp.StatusCode, resp.Header.Get("x-request-id"), truncateString(string(respBody), 1000))
+
+		s.handleFailoverSideEffects(ctx, resp, account)
+		appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+			Platform:           account.Platform,
+			AccountID:          account.ID,
+			AccountName:        account.Name,
+			UpstreamStatusCode: resp.StatusCode,
+			UpstreamRequestID:  resp.Header.Get("x-request-id"),
+			Passthrough:        true,
+			Kind:               "failover",
+			Message:            extractUpstreamErrorMessage(respBody),
+			Detail: func() string {
+				if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+					return truncateString(string(respBody), s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes)
+				}
+				return ""
+			}(),
+		})
+		return nil, &UpstreamFailoverError{StatusCode: resp.StatusCode, ResponseBody: respBody}
+	}
+
+	if resp.StatusCode >= 400 {
+		return s.handleErrorResponse(ctx, resp, c, account)
+	}
+
+	var usage *ClaudeUsage
+	var firstTokenMs *int
+	var clientDisconnect bool
+	if reqStream {
+		streamResult, err := s.handleStreamingResponseAnthropicAPIKeyPassthrough(ctx, resp, c, account, startTime)
+		if err != nil {
+			return nil, err
+		}
+		usage = streamResult.usage
+		firstTokenMs = streamResult.firstTokenMs
+		clientDisconnect = streamResult.clientDisconnect
+	} else {
+		usage, err = s.handleNonStreamingResponseAnthropicAPIKeyPassthrough(ctx, resp, c, account)
+		if err != nil {
+			return nil, err
+		}
+	}
+	if usage == nil {
+		usage = &ClaudeUsage{}
+	}
+
+	return &ForwardResult{
+		RequestID:        resp.Header.Get("x-request-id"),
+		Usage:            *usage,
+		Model:            reqModel,
+		Stream:           reqStream,
+		Duration:         time.Since(startTime),
+		FirstTokenMs:     firstTokenMs,
+		ClientDisconnect: clientDisconnect,
+	}, nil
+}
+
+func (s *GatewayService) buildUpstreamRequestAnthropicAPIKeyPassthrough(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	body []byte,
+	token string,
+) (*http.Request, error) {
+	targetURL := claudeAPIURL
+	baseURL := account.GetBaseURL()
+	if baseURL != "" {
+		validatedURL, err := s.validateUpstreamBaseURL(baseURL)
+		if err != nil {
+			return nil, err
+		}
+		targetURL = validatedURL + "/v1/messages"
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, targetURL, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+
+	if c != nil && c.Request != nil {
+		for key, values := range c.Request.Header {
+			lowerKey := strings.ToLower(strings.TrimSpace(key))
+			if !allowedHeaders[lowerKey] {
+				continue
+			}
+			for _, v := range values {
+				req.Header.Add(key, v)
+			}
+		}
+	}
+
+	// 覆盖入站鉴权残留，并注入上游认证
+	req.Header.Del("authorization")
+	req.Header.Del("x-api-key")
+	req.Header.Del("x-goog-api-key")
+	req.Header.Del("cookie")
+	req.Header.Set("x-api-key", token)
+
+	if req.Header.Get("content-type") == "" {
+		req.Header.Set("content-type", "application/json")
+	}
+	if req.Header.Get("anthropic-version") == "" {
+		req.Header.Set("anthropic-version", "2023-06-01")
+	}
+
+	return req, nil
+}
+
+func (s *GatewayService) handleStreamingResponseAnthropicAPIKeyPassthrough(
+	ctx context.Context,
+	resp *http.Response,
+	c *gin.Context,
+	account *Account,
+	startTime time.Time,
+) (*streamingResult, error) {
+	if s.rateLimitService != nil {
+		s.rateLimitService.UpdateSessionWindow(ctx, account, resp.Header)
+	}
+
+	writeAnthropicPassthroughResponseHeaders(c.Writer.Header(), resp.Header, s.cfg)
+
+	contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
+	if contentType == "" {
+		contentType = "text/event-stream"
+	}
+	c.Header("Content-Type", contentType)
+	if c.Writer.Header().Get("Cache-Control") == "" {
+		c.Header("Cache-Control", "no-cache")
+	}
+	if c.Writer.Header().Get("Connection") == "" {
+		c.Header("Connection", "keep-alive")
+	}
+	c.Header("X-Accel-Buffering", "no")
+	if v := resp.Header.Get("x-request-id"); v != "" {
+		c.Header("x-request-id", v)
+	}
+
+	w := c.Writer
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		return nil, errors.New("streaming not supported")
+	}
+
+	usage := &ClaudeUsage{}
+	var firstTokenMs *int
+	clientDisconnected := false
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanBuf := getSSEScannerBuf64K()
+	scanner.Buffer(scanBuf[:0], maxLineSize)
+	defer putSSEScannerBuf64K(scanBuf)
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if data, ok := extractAnthropicSSEDataLine(line); ok {
+			trimmed := strings.TrimSpace(data)
+			if firstTokenMs == nil && trimmed != "" && trimmed != "[DONE]" {
+				ms := int(time.Since(startTime).Milliseconds())
+				firstTokenMs = &ms
+			}
+			s.parseSSEUsagePassthrough(data, usage)
+		}
+
+		if !clientDisconnected {
+			if _, err := io.WriteString(w, line); err != nil {
+				clientDisconnected = true
+				logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] Client disconnected during streaming, continue draining upstream for usage: account=%d", account.ID)
+			} else if _, err := io.WriteString(w, "\n"); err != nil {
+				clientDisconnected = true
+				logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] Client disconnected during streaming, continue draining upstream for usage: account=%d", account.ID)
+			} else if line == "" {
+				// 按 SSE 事件边界刷出，减少每行 flush 带来的 syscall 开销。
+				flusher.Flush()
+			}
+		}
+	}
+	if !clientDisconnected {
+		// 兜底补刷，确保最后一个未以空行结尾的事件也能及时送达客户端。
+		flusher.Flush()
+	}
+
+	if err := scanner.Err(); err != nil {
+		if clientDisconnected {
+			logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] Upstream read error after client disconnect: account=%d err=%v", account.ID, err)
+			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+		}
+		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
+			logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] 流读取被取消: account=%d request_id=%s err=%v ctx_err=%v",
+				account.ID, resp.Header.Get("x-request-id"), err, ctx.Err())
+			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: true}, nil
+		}
+		if errors.Is(err, bufio.ErrTooLong) {
+			logger.LegacyPrintf("service.gateway", "[Anthropic passthrough] SSE line too long: account=%d max_size=%d error=%v", account.ID, maxLineSize, err)
+			return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, err
+		}
+		return &streamingResult{usage: usage, firstTokenMs: firstTokenMs}, fmt.Errorf("stream read error: %w", err)
+	}
+
+	return &streamingResult{usage: usage, firstTokenMs: firstTokenMs, clientDisconnect: clientDisconnected}, nil
+}
+
+func extractAnthropicSSEDataLine(line string) (string, bool) {
+	if !strings.HasPrefix(line, "data:") {
+		return "", false
+	}
+	start := len("data:")
+	for start < len(line) {
+		if line[start] != ' ' && line[start] != '\t' {
+			break
+		}
+		start++
+	}
+	return line[start:], true
+}
+
+func (s *GatewayService) parseSSEUsagePassthrough(data string, usage *ClaudeUsage) {
+	if usage == nil || data == "" || data == "[DONE]" {
+		return
+	}
+
+	parsed := gjson.Parse(data)
+	switch parsed.Get("type").String() {
+	case "message_start":
+		msgUsage := parsed.Get("message.usage")
+		if msgUsage.Exists() {
+			usage.InputTokens = int(msgUsage.Get("input_tokens").Int())
+			usage.CacheCreationInputTokens = int(msgUsage.Get("cache_creation_input_tokens").Int())
+			usage.CacheReadInputTokens = int(msgUsage.Get("cache_read_input_tokens").Int())
+
+			// 保持与通用解析一致：message_start 允许覆盖 5m/1h 明细（包括 0）。
+			cc5m := msgUsage.Get("cache_creation.ephemeral_5m_input_tokens")
+			cc1h := msgUsage.Get("cache_creation.ephemeral_1h_input_tokens")
+			if cc5m.Exists() || cc1h.Exists() {
+				usage.CacheCreation5mTokens = int(cc5m.Int())
+				usage.CacheCreation1hTokens = int(cc1h.Int())
+			}
+		}
+	case "message_delta":
+		deltaUsage := parsed.Get("usage")
+		if deltaUsage.Exists() {
+			if v := deltaUsage.Get("input_tokens").Int(); v > 0 {
+				usage.InputTokens = int(v)
+			}
+			if v := deltaUsage.Get("output_tokens").Int(); v > 0 {
+				usage.OutputTokens = int(v)
+			}
+			if v := deltaUsage.Get("cache_creation_input_tokens").Int(); v > 0 {
+				usage.CacheCreationInputTokens = int(v)
+			}
+			if v := deltaUsage.Get("cache_read_input_tokens").Int(); v > 0 {
+				usage.CacheReadInputTokens = int(v)
+			}
+
+			cc5m := deltaUsage.Get("cache_creation.ephemeral_5m_input_tokens")
+			cc1h := deltaUsage.Get("cache_creation.ephemeral_1h_input_tokens")
+			if cc5m.Exists() && cc5m.Int() > 0 {
+				usage.CacheCreation5mTokens = int(cc5m.Int())
+			}
+			if cc1h.Exists() && cc1h.Int() > 0 {
+				usage.CacheCreation1hTokens = int(cc1h.Int())
+			}
+		}
+	}
+
+	if usage.CacheReadInputTokens == 0 {
+		if cached := parsed.Get("message.usage.cached_tokens").Int(); cached > 0 {
+			usage.CacheReadInputTokens = int(cached)
+		}
+		if cached := parsed.Get("usage.cached_tokens").Int(); usage.CacheReadInputTokens == 0 && cached > 0 {
+			usage.CacheReadInputTokens = int(cached)
+		}
+	}
+	if usage.CacheCreationInputTokens == 0 {
+		cc5m := parsed.Get("message.usage.cache_creation.ephemeral_5m_input_tokens").Int()
+		cc1h := parsed.Get("message.usage.cache_creation.ephemeral_1h_input_tokens").Int()
+		if cc5m == 0 && cc1h == 0 {
+			cc5m = parsed.Get("usage.cache_creation.ephemeral_5m_input_tokens").Int()
+			cc1h = parsed.Get("usage.cache_creation.ephemeral_1h_input_tokens").Int()
+		}
+		total := cc5m + cc1h
+		if total > 0 {
+			usage.CacheCreationInputTokens = int(total)
+		}
+	}
+}
+
+func parseClaudeUsageFromResponseBody(body []byte) *ClaudeUsage {
+	usage := &ClaudeUsage{}
+	if len(body) == 0 {
+		return usage
+	}
+
+	parsed := gjson.ParseBytes(body)
+	usageNode := parsed.Get("usage")
+	if !usageNode.Exists() {
+		return usage
+	}
+
+	usage.InputTokens = int(usageNode.Get("input_tokens").Int())
+	usage.OutputTokens = int(usageNode.Get("output_tokens").Int())
+	usage.CacheCreationInputTokens = int(usageNode.Get("cache_creation_input_tokens").Int())
+	usage.CacheReadInputTokens = int(usageNode.Get("cache_read_input_tokens").Int())
+
+	cc5m := usageNode.Get("cache_creation.ephemeral_5m_input_tokens").Int()
+	cc1h := usageNode.Get("cache_creation.ephemeral_1h_input_tokens").Int()
+	if cc5m > 0 || cc1h > 0 {
+		usage.CacheCreation5mTokens = int(cc5m)
+		usage.CacheCreation1hTokens = int(cc1h)
+	}
+	if usage.CacheCreationInputTokens == 0 && (cc5m > 0 || cc1h > 0) {
+		usage.CacheCreationInputTokens = int(cc5m + cc1h)
+	}
+	if usage.CacheReadInputTokens == 0 {
+		if cached := usageNode.Get("cached_tokens").Int(); cached > 0 {
+			usage.CacheReadInputTokens = int(cached)
+		}
+	}
+	return usage
+}
+
+func (s *GatewayService) handleNonStreamingResponseAnthropicAPIKeyPassthrough(
+	ctx context.Context,
+	resp *http.Response,
+	c *gin.Context,
+	account *Account,
+) (*ClaudeUsage, error) {
+	if s.rateLimitService != nil {
+		s.rateLimitService.UpdateSessionWindow(ctx, account, resp.Header)
+	}
+
+	maxBytes := resolveUpstreamResponseReadLimit(s.cfg)
+	body, err := readUpstreamResponseBodyLimited(resp.Body, maxBytes)
+	if err != nil {
+		if errors.Is(err, ErrUpstreamResponseBodyTooLarge) {
+			setOpsUpstreamError(c, http.StatusBadGateway, "upstream response too large", "")
+			c.JSON(http.StatusBadGateway, gin.H{
+				"type": "error",
+				"error": gin.H{
+					"type":    "upstream_error",
+					"message": "Upstream response too large",
+				},
+			})
+		}
+		return nil, err
+	}
+
+	usage := parseClaudeUsageFromResponseBody(body)
+
+	writeAnthropicPassthroughResponseHeaders(c.Writer.Header(), resp.Header, s.cfg)
+	contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
+	if contentType == "" {
+		contentType = "application/json"
+	}
+	c.Data(resp.StatusCode, contentType, body)
+	return usage, nil
+}
+
+func writeAnthropicPassthroughResponseHeaders(dst http.Header, src http.Header, cfg *config.Config) {
+	if dst == nil || src == nil {
+		return
+	}
+	if cfg != nil {
+		responseheaders.WriteFilteredHeaders(dst, src, cfg.Security.ResponseHeaders)
+		return
+	}
+	if v := strings.TrimSpace(src.Get("Content-Type")); v != "" {
+		dst.Set("Content-Type", v)
+	}
+	if v := strings.TrimSpace(src.Get("x-request-id")); v != "" {
+		dst.Set("x-request-id", v)
+	}
+}
+
 func (s *GatewayService) buildUpstreamRequest(ctx context.Context, c *gin.Context, account *Account, body []byte, token, tokenType, modelID string, reqStream bool, mimicClaudeCode bool) (*http.Request, error) {
 	// 确定目标URL
 	targetURL := claudeAPIURL
@@ -5082,6 +5618,10 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 		return fmt.Errorf("parse request: empty request")
 	}
 
+	if account != nil && account.IsAnthropicAPIKeyPassthroughEnabled() {
+		return s.forwardCountTokensAnthropicAPIKeyPassthrough(ctx, c, account, parsed.Body)
+	}
+
 	body := parsed.Body
 	reqModel := parsed.Model
 
@@ -5241,6 +5781,158 @@ func (s *GatewayService) ForwardCountTokens(ctx context.Context, c *gin.Context,
 	return nil
 }
 
+func (s *GatewayService) forwardCountTokensAnthropicAPIKeyPassthrough(ctx context.Context, c *gin.Context, account *Account, body []byte) error {
+	token, tokenType, err := s.GetAccessToken(ctx, account)
+	if err != nil {
+		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Failed to get access token")
+		return err
+	}
+	if tokenType != "apikey" {
+		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Invalid account token type")
+		return fmt.Errorf("anthropic api key passthrough requires apikey token, got: %s", tokenType)
+	}
+
+	upstreamReq, err := s.buildCountTokensRequestAnthropicAPIKeyPassthrough(ctx, c, account, body, token)
+	if err != nil {
+		s.countTokensError(c, http.StatusInternalServerError, "api_error", "Failed to build request")
+		return err
+	}
+
+	proxyURL := ""
+	if account.ProxyID != nil && account.Proxy != nil {
+		proxyURL = account.Proxy.URL()
+	}
+
+	resp, err := s.httpUpstream.DoWithTLS(upstreamReq, proxyURL, account.ID, account.Concurrency, account.IsTLSFingerprintEnabled())
+	if err != nil {
+		setOpsUpstreamError(c, 0, sanitizeUpstreamErrorMessage(err.Error()), "")
+		appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+			Platform:           account.Platform,
+			AccountID:          account.ID,
+			AccountName:        account.Name,
+			UpstreamStatusCode: 0,
+			Passthrough:        true,
+			Kind:               "request_error",
+			Message:            sanitizeUpstreamErrorMessage(err.Error()),
+		})
+		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Request failed")
+		return fmt.Errorf("upstream request failed: %w", err)
+	}
+
+	maxReadBytes := resolveUpstreamResponseReadLimit(s.cfg)
+	respBody, err := readUpstreamResponseBodyLimited(resp.Body, maxReadBytes)
+	_ = resp.Body.Close()
+	if err != nil {
+		if errors.Is(err, ErrUpstreamResponseBodyTooLarge) {
+			setOpsUpstreamError(c, http.StatusBadGateway, "upstream response too large", "")
+			s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Upstream response too large")
+			return err
+		}
+		s.countTokensError(c, http.StatusBadGateway, "upstream_error", "Failed to read response")
+		return err
+	}
+
+	if resp.StatusCode >= 400 {
+		if s.rateLimitService != nil {
+			s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)
+		}
+
+		upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
+		upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
+		upstreamDetail := ""
+		if s.cfg != nil && s.cfg.Gateway.LogUpstreamErrorBody {
+			maxBytes := s.cfg.Gateway.LogUpstreamErrorBodyMaxBytes
+			if maxBytes <= 0 {
+				maxBytes = 2048
+			}
+			upstreamDetail = truncateString(string(respBody), maxBytes)
+		}
+		setOpsUpstreamError(c, resp.StatusCode, upstreamMsg, upstreamDetail)
+		appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+			Platform:           account.Platform,
+			AccountID:          account.ID,
+			AccountName:        account.Name,
+			UpstreamStatusCode: resp.StatusCode,
+			UpstreamRequestID:  resp.Header.Get("x-request-id"),
+			Passthrough:        true,
+			Kind:               "http_error",
+			Message:            upstreamMsg,
+			Detail:             upstreamDetail,
+		})
+
+		errMsg := "Upstream request failed"
+		switch resp.StatusCode {
+		case 429:
+			errMsg = "Rate limit exceeded"
+		case 529:
+			errMsg = "Service overloaded"
+		}
+		s.countTokensError(c, resp.StatusCode, "upstream_error", errMsg)
+		if upstreamMsg == "" {
+			return fmt.Errorf("upstream error: %d", resp.StatusCode)
+		}
+		return fmt.Errorf("upstream error: %d message=%s", resp.StatusCode, upstreamMsg)
+	}
+
+	writeAnthropicPassthroughResponseHeaders(c.Writer.Header(), resp.Header, s.cfg)
+	contentType := strings.TrimSpace(resp.Header.Get("Content-Type"))
+	if contentType == "" {
+		contentType = "application/json"
+	}
+	c.Data(resp.StatusCode, contentType, respBody)
+	return nil
+}
+
+func (s *GatewayService) buildCountTokensRequestAnthropicAPIKeyPassthrough(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	body []byte,
+	token string,
+) (*http.Request, error) {
+	targetURL := claudeAPICountTokensURL
+	baseURL := account.GetBaseURL()
+	if baseURL != "" {
+		validatedURL, err := s.validateUpstreamBaseURL(baseURL)
+		if err != nil {
+			return nil, err
+		}
+		targetURL = validatedURL + "/v1/messages/count_tokens"
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, targetURL, bytes.NewReader(body))
+	if err != nil {
+		return nil, err
+	}
+
+	if c != nil && c.Request != nil {
+		for key, values := range c.Request.Header {
+			lowerKey := strings.ToLower(strings.TrimSpace(key))
+			if !allowedHeaders[lowerKey] {
+				continue
+			}
+			for _, v := range values {
+				req.Header.Add(key, v)
+			}
+		}
+	}
+
+	req.Header.Del("authorization")
+	req.Header.Del("x-api-key")
+	req.Header.Del("x-goog-api-key")
+	req.Header.Del("cookie")
+	req.Header.Set("x-api-key", token)
+
+	if req.Header.Get("content-type") == "" {
+		req.Header.Set("content-type", "application/json")
+	}
+	if req.Header.Get("anthropic-version") == "" {
+		req.Header.Set("anthropic-version", "2023-06-01")
+	}
+
+	return req, nil
+}
+
 // buildCountTokensRequest 构建 count_tokens 上游请求
 func (s *GatewayService) buildCountTokensRequest(ctx context.Context, c *gin.Context, account *Account, body []byte, token, tokenType, modelID string, mimicClaudeCode bool) (*http.Request, error) {
 	// 确定目标 URL