Merge pull request #1242 from Ethan0x0000/feat/anthropic-openai-endpoint-compat

支持 Anthropic Responses / Chat Completions 兼容端点并完善会话一致性与错误可观测性

backend/internal/handler/gateway_handler.go

@@ -178,6 +178,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 	c.Request = c.Request.WithContext(service.WithThinkingEnabled(c.Request.Context(), parsedReq.ThinkingEnabled, h.metadataBridgeEnabled()))
 
 	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
 
 	// 验证 model 必填
 	if reqModel == "" {
@@ -1396,6 +1397,7 @@ func (h *GatewayHandler) CountTokens(c *gin.Context) {
 	}
 
 	setOpsRequestContext(c, parsedReq.Model, parsedReq.Stream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(parsedReq.Stream, false)))
 
 	// 获取订阅信息（可能为nil）
 	subscription, _ := middleware2.GetSubscriptionFromContext(c)

backend/internal/handler/gateway_handler_chat_completions.go

+package handler
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"time"
+
+	pkghttputil "github.com/Wei-Shaw/sub2api/internal/pkg/httputil"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ip"
+	middleware2 "github.com/Wei-Shaw/sub2api/internal/server/middleware"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+	"go.uber.org/zap"
+)
+
+// ChatCompletions handles OpenAI Chat Completions API endpoint for Anthropic platform groups.
+// POST /v1/chat/completions
+// This converts Chat Completions requests to Anthropic format (via Responses format chain),
+// forwards to Anthropic upstream, and converts responses back to Chat Completions format.
+func (h *GatewayHandler) ChatCompletions(c *gin.Context) {
+	streamStarted := false
+
+	requestStart := time.Now()
+
+	apiKey, ok := middleware2.GetAPIKeyFromContext(c)
+	if !ok {
+		h.chatCompletionsErrorResponse(c, http.StatusUnauthorized, "authentication_error", "Invalid API key")
+		return
+	}
+
+	subject, ok := middleware2.GetAuthSubjectFromContext(c)
+	if !ok {
+		h.chatCompletionsErrorResponse(c, http.StatusInternalServerError, "api_error", "User context not found")
+		return
+	}
+	reqLog := requestLogger(
+		c,
+		"handler.gateway.chat_completions",
+		zap.Int64("user_id", subject.UserID),
+		zap.Int64("api_key_id", apiKey.ID),
+		zap.Any("group_id", apiKey.GroupID),
+	)
+
+	// Read request body
+	body, err := pkghttputil.ReadRequestBodyWithPrealloc(c.Request)
+	if err != nil {
+		if maxErr, ok := extractMaxBytesError(err); ok {
+			h.chatCompletionsErrorResponse(c, http.StatusRequestEntityTooLarge, "invalid_request_error", buildBodyTooLargeMessage(maxErr.Limit))
+			return
+		}
+		h.chatCompletionsErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to read request body")
+		return
+	}
+
+	if len(body) == 0 {
+		h.chatCompletionsErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Request body is empty")
+		return
+	}
+
+	setOpsRequestContext(c, "", false, body)
+
+	// Validate JSON
+	if !gjson.ValidBytes(body) {
+		h.chatCompletionsErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
+		return
+	}
+
+	// Extract model and stream
+	modelResult := gjson.GetBytes(body, "model")
+	if !modelResult.Exists() || modelResult.Type != gjson.String || modelResult.String() == "" {
+		h.chatCompletionsErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "model is required")
+		return
+	}
+	reqModel := modelResult.String()
+	reqStream := gjson.GetBytes(body, "stream").Bool()
+	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
+
+	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
+
+	// Claude Code only restriction
+	if apiKey.Group != nil && apiKey.Group.ClaudeCodeOnly {
+		h.chatCompletionsErrorResponse(c, http.StatusForbidden, "permission_error",
+			"This group is restricted to Claude Code clients (/v1/messages only)")
+		return
+	}
+
+	// Error passthrough binding
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
+
+	subscription, _ := middleware2.GetSubscriptionFromContext(c)
+
+	service.SetOpsLatencyMs(c, service.OpsAuthLatencyMsKey, time.Since(requestStart).Milliseconds())
+
+	// 1. Acquire user concurrency slot
+	maxWait := service.CalculateMaxWait(subject.Concurrency)
+	canWait, err := h.concurrencyHelper.IncrementWaitCount(c.Request.Context(), subject.UserID, maxWait)
+	waitCounted := false
+	if err != nil {
+		reqLog.Warn("gateway.cc.user_wait_counter_increment_failed", zap.Error(err))
+	} else if !canWait {
+		h.chatCompletionsErrorResponse(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later")
+		return
+	}
+	if err == nil && canWait {
+		waitCounted = true
+	}
+	defer func() {
+		if waitCounted {
+			h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		}
+	}()
+
+	userReleaseFunc, err := h.concurrencyHelper.AcquireUserSlotWithWait(c, subject.UserID, subject.Concurrency, reqStream, &streamStarted)
+	if err != nil {
+		reqLog.Warn("gateway.cc.user_slot_acquire_failed", zap.Error(err))
+		h.handleConcurrencyError(c, err, "user", streamStarted)
+		return
+	}
+	if waitCounted {
+		h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		waitCounted = false
+	}
+	userReleaseFunc = wrapReleaseOnDone(c.Request.Context(), userReleaseFunc)
+	if userReleaseFunc != nil {
+		defer userReleaseFunc()
+	}
+
+	// 2. Re-check billing
+	if err := h.billingCacheService.CheckBillingEligibility(c.Request.Context(), apiKey.User, apiKey, apiKey.Group, subscription); err != nil {
+		reqLog.Info("gateway.cc.billing_check_failed", zap.Error(err))
+		status, code, message := billingErrorDetails(err)
+		h.chatCompletionsErrorResponse(c, status, code, message)
+		return
+	}
+
+	// Parse request for session hash
+	parsedReq, _ := service.ParseGatewayRequest(body, "chat_completions")
+	if parsedReq == nil {
+		parsedReq = &service.ParsedRequest{Model: reqModel, Stream: reqStream, Body: body}
+	}
+	parsedReq.SessionContext = &service.SessionContext{
+		ClientIP:  ip.GetClientIP(c),
+		UserAgent: c.GetHeader("User-Agent"),
+		APIKeyID:  apiKey.ID,
+	}
+	sessionHash := h.gatewayService.GenerateSessionHash(parsedReq)
+
+	// 3. Account selection + failover loop
+	fs := NewFailoverState(h.maxAccountSwitches, false)
+
+	for {
+		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, fs.FailedAccountIDs, "")
+		if err != nil {
+			if len(fs.FailedAccountIDs) == 0 {
+				h.chatCompletionsErrorResponse(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error())
+				return
+			}
+			action := fs.HandleSelectionExhausted(c.Request.Context())
+			switch action {
+			case FailoverContinue:
+				continue
+			case FailoverCanceled:
+				return
+			default:
+				if fs.LastFailoverErr != nil {
+					h.handleCCFailoverExhausted(c, fs.LastFailoverErr, streamStarted)
+				} else {
+					h.chatCompletionsErrorResponse(c, http.StatusBadGateway, "server_error", "All available accounts exhausted")
+				}
+				return
+			}
+		}
+		account := selection.Account
+		setOpsSelectedAccount(c, account.ID, account.Platform)
+
+		// 4. Acquire account concurrency slot
+		accountReleaseFunc := selection.ReleaseFunc
+		if !selection.Acquired {
+			if selection.WaitPlan == nil {
+				h.chatCompletionsErrorResponse(c, http.StatusServiceUnavailable, "api_error", "No available accounts")
+				return
+			}
+			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
+				c,
+				account.ID,
+				selection.WaitPlan.MaxConcurrency,
+				selection.WaitPlan.Timeout,
+				reqStream,
+				&streamStarted,
+			)
+			if err != nil {
+				reqLog.Warn("gateway.cc.account_slot_acquire_failed", zap.Int64("account_id", account.ID), zap.Error(err))
+				h.handleConcurrencyError(c, err, "account", streamStarted)
+				return
+			}
+		}
+		accountReleaseFunc = wrapReleaseOnDone(c.Request.Context(), accountReleaseFunc)
+
+		// 5. Forward request
+		writerSizeBeforeForward := c.Writer.Size()
+		result, err := h.gatewayService.ForwardAsChatCompletions(c.Request.Context(), c, account, body, parsedReq)
+
+		if accountReleaseFunc != nil {
+			accountReleaseFunc()
+		}
+
+		if err != nil {
+			var failoverErr *service.UpstreamFailoverError
+			if errors.As(err, &failoverErr) {
+				if c.Writer.Size() != writerSizeBeforeForward {
+					h.handleCCFailoverExhausted(c, failoverErr, true)
+					return
+				}
+				action := fs.HandleFailoverError(c.Request.Context(), h.gatewayService, account.ID, account.Platform, failoverErr)
+				switch action {
+				case FailoverContinue:
+					continue
+				case FailoverExhausted:
+					h.handleCCFailoverExhausted(c, fs.LastFailoverErr, streamStarted)
+					return
+				case FailoverCanceled:
+					return
+				}
+			}
+			h.ensureForwardErrorResponse(c, streamStarted)
+			reqLog.Error("gateway.cc.forward_failed",
+				zap.Int64("account_id", account.ID),
+				zap.Error(err),
+			)
+			return
+		}
+
+		// 6. Record usage
+		userAgent := c.GetHeader("User-Agent")
+		clientIP := ip.GetClientIP(c)
+		requestPayloadHash := service.HashUsageRequestPayload(body)
+		inboundEndpoint := GetInboundEndpoint(c)
+		upstreamEndpoint := GetUpstreamEndpoint(c, account.Platform)
+
+		h.submitUsageRecordTask(func(ctx context.Context) {
+			if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
+				Result:             result,
+				APIKey:             apiKey,
+				User:               apiKey.User,
+				Account:            account,
+				Subscription:       subscription,
+				InboundEndpoint:    inboundEndpoint,
+				UpstreamEndpoint:   upstreamEndpoint,
+				UserAgent:          userAgent,
+				IPAddress:          clientIP,
+				RequestPayloadHash: requestPayloadHash,
+				APIKeyService:      h.apiKeyService,
+			}); err != nil {
+				reqLog.Error("gateway.cc.record_usage_failed",
+					zap.Int64("account_id", account.ID),
+					zap.Error(err),
+				)
+			}
+		})
+		return
+	}
+}
+
+// chatCompletionsErrorResponse writes an error in OpenAI Chat Completions format.
+func (h *GatewayHandler) chatCompletionsErrorResponse(c *gin.Context, status int, errType, message string) {
+	c.JSON(status, gin.H{
+		"error": gin.H{
+			"type":    errType,
+			"message": message,
+		},
+	})
+}
+
+// handleCCFailoverExhausted writes a failover-exhausted error in CC format.
+func (h *GatewayHandler) handleCCFailoverExhausted(c *gin.Context, lastErr *service.UpstreamFailoverError, streamStarted bool) {
+	if streamStarted {
+		return
+	}
+	statusCode := http.StatusBadGateway
+	if lastErr != nil && lastErr.StatusCode > 0 {
+		statusCode = lastErr.StatusCode
+	}
+	h.chatCompletionsErrorResponse(c, statusCode, "server_error", "All available accounts exhausted")
+}

backend/internal/handler/gateway_handler_responses.go

+package handler
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"time"
+
+	pkghttputil "github.com/Wei-Shaw/sub2api/internal/pkg/httputil"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/ip"
+	middleware2 "github.com/Wei-Shaw/sub2api/internal/server/middleware"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+	"go.uber.org/zap"
+)
+
+// Responses handles OpenAI Responses API endpoint for Anthropic platform groups.
+// POST /v1/responses
+// This converts Responses API requests to Anthropic format, forwards to Anthropic
+// upstream, and converts responses back to Responses format.
+func (h *GatewayHandler) Responses(c *gin.Context) {
+	streamStarted := false
+
+	requestStart := time.Now()
+
+	apiKey, ok := middleware2.GetAPIKeyFromContext(c)
+	if !ok {
+		h.responsesErrorResponse(c, http.StatusUnauthorized, "authentication_error", "Invalid API key")
+		return
+	}
+
+	subject, ok := middleware2.GetAuthSubjectFromContext(c)
+	if !ok {
+		h.responsesErrorResponse(c, http.StatusInternalServerError, "api_error", "User context not found")
+		return
+	}
+	reqLog := requestLogger(
+		c,
+		"handler.gateway.responses",
+		zap.Int64("user_id", subject.UserID),
+		zap.Int64("api_key_id", apiKey.ID),
+		zap.Any("group_id", apiKey.GroupID),
+	)
+
+	// Read request body
+	body, err := pkghttputil.ReadRequestBodyWithPrealloc(c.Request)
+	if err != nil {
+		if maxErr, ok := extractMaxBytesError(err); ok {
+			h.responsesErrorResponse(c, http.StatusRequestEntityTooLarge, "invalid_request_error", buildBodyTooLargeMessage(maxErr.Limit))
+			return
+		}
+		h.responsesErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to read request body")
+		return
+	}
+
+	if len(body) == 0 {
+		h.responsesErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Request body is empty")
+		return
+	}
+
+	setOpsRequestContext(c, "", false, body)
+
+	// Validate JSON
+	if !gjson.ValidBytes(body) {
+		h.responsesErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "Failed to parse request body")
+		return
+	}
+
+	// Extract model and stream using gjson (like OpenAI handler)
+	modelResult := gjson.GetBytes(body, "model")
+	if !modelResult.Exists() || modelResult.Type != gjson.String || modelResult.String() == "" {
+		h.responsesErrorResponse(c, http.StatusBadRequest, "invalid_request_error", "model is required")
+		return
+	}
+	reqModel := modelResult.String()
+	reqStream := gjson.GetBytes(body, "stream").Bool()
+	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
+
+	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
+
+	// Claude Code only restriction:
+	// /v1/responses is never a Claude Code endpoint.
+	// When claude_code_only is enabled, this endpoint is rejected.
+	// The existing service-layer checkClaudeCodeRestriction handles degradation
+	// to fallback groups when the Forward path calls SelectAccountForModelWithExclusions.
+	// Here we just reject at handler level since /v1/responses clients can't be Claude Code.
+	if apiKey.Group != nil && apiKey.Group.ClaudeCodeOnly {
+		h.responsesErrorResponse(c, http.StatusForbidden, "permission_error",
+			"This group is restricted to Claude Code clients (/v1/messages only)")
+		return
+	}
+
+	// Error passthrough binding
+	if h.errorPassthroughService != nil {
+		service.BindErrorPassthroughService(c, h.errorPassthroughService)
+	}
+
+	subscription, _ := middleware2.GetSubscriptionFromContext(c)
+
+	service.SetOpsLatencyMs(c, service.OpsAuthLatencyMsKey, time.Since(requestStart).Milliseconds())
+
+	// 1. Acquire user concurrency slot
+	maxWait := service.CalculateMaxWait(subject.Concurrency)
+	canWait, err := h.concurrencyHelper.IncrementWaitCount(c.Request.Context(), subject.UserID, maxWait)
+	waitCounted := false
+	if err != nil {
+		reqLog.Warn("gateway.responses.user_wait_counter_increment_failed", zap.Error(err))
+	} else if !canWait {
+		h.responsesErrorResponse(c, http.StatusTooManyRequests, "rate_limit_error", "Too many pending requests, please retry later")
+		return
+	}
+	if err == nil && canWait {
+		waitCounted = true
+	}
+	defer func() {
+		if waitCounted {
+			h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		}
+	}()
+
+	userReleaseFunc, err := h.concurrencyHelper.AcquireUserSlotWithWait(c, subject.UserID, subject.Concurrency, reqStream, &streamStarted)
+	if err != nil {
+		reqLog.Warn("gateway.responses.user_slot_acquire_failed", zap.Error(err))
+		h.handleConcurrencyError(c, err, "user", streamStarted)
+		return
+	}
+	if waitCounted {
+		h.concurrencyHelper.DecrementWaitCount(c.Request.Context(), subject.UserID)
+		waitCounted = false
+	}
+	userReleaseFunc = wrapReleaseOnDone(c.Request.Context(), userReleaseFunc)
+	if userReleaseFunc != nil {
+		defer userReleaseFunc()
+	}
+
+	// 2. Re-check billing
+	if err := h.billingCacheService.CheckBillingEligibility(c.Request.Context(), apiKey.User, apiKey, apiKey.Group, subscription); err != nil {
+		reqLog.Info("gateway.responses.billing_check_failed", zap.Error(err))
+		status, code, message := billingErrorDetails(err)
+		h.responsesErrorResponse(c, status, code, message)
+		return
+	}
+
+	// Parse request for session hash
+	parsedReq, _ := service.ParseGatewayRequest(body, "responses")
+	if parsedReq == nil {
+		parsedReq = &service.ParsedRequest{Model: reqModel, Stream: reqStream, Body: body}
+	}
+	parsedReq.SessionContext = &service.SessionContext{
+		ClientIP:  ip.GetClientIP(c),
+		UserAgent: c.GetHeader("User-Agent"),
+		APIKeyID:  apiKey.ID,
+	}
+	sessionHash := h.gatewayService.GenerateSessionHash(parsedReq)
+
+	// 3. Account selection + failover loop
+	fs := NewFailoverState(h.maxAccountSwitches, false)
+
+	for {
+		selection, err := h.gatewayService.SelectAccountWithLoadAwareness(c.Request.Context(), apiKey.GroupID, sessionHash, reqModel, fs.FailedAccountIDs, "")
+		if err != nil {
+			if len(fs.FailedAccountIDs) == 0 {
+				h.responsesErrorResponse(c, http.StatusServiceUnavailable, "api_error", "No available accounts: "+err.Error())
+				return
+			}
+			action := fs.HandleSelectionExhausted(c.Request.Context())
+			switch action {
+			case FailoverContinue:
+				continue
+			case FailoverCanceled:
+				return
+			default:
+				if fs.LastFailoverErr != nil {
+					h.handleResponsesFailoverExhausted(c, fs.LastFailoverErr, streamStarted)
+				} else {
+					h.responsesErrorResponse(c, http.StatusBadGateway, "server_error", "All available accounts exhausted")
+				}
+				return
+			}
+		}
+		account := selection.Account
+		setOpsSelectedAccount(c, account.ID, account.Platform)
+
+		// 4. Acquire account concurrency slot
+		accountReleaseFunc := selection.ReleaseFunc
+		if !selection.Acquired {
+			if selection.WaitPlan == nil {
+				h.responsesErrorResponse(c, http.StatusServiceUnavailable, "api_error", "No available accounts")
+				return
+			}
+			accountReleaseFunc, err = h.concurrencyHelper.AcquireAccountSlotWithWaitTimeout(
+				c,
+				account.ID,
+				selection.WaitPlan.MaxConcurrency,
+				selection.WaitPlan.Timeout,
+				reqStream,
+				&streamStarted,
+			)
+			if err != nil {
+				reqLog.Warn("gateway.responses.account_slot_acquire_failed", zap.Int64("account_id", account.ID), zap.Error(err))
+				h.handleConcurrencyError(c, err, "account", streamStarted)
+				return
+			}
+		}
+		accountReleaseFunc = wrapReleaseOnDone(c.Request.Context(), accountReleaseFunc)
+
+		// 5. Forward request
+		writerSizeBeforeForward := c.Writer.Size()
+		result, err := h.gatewayService.ForwardAsResponses(c.Request.Context(), c, account, body, parsedReq)
+
+		if accountReleaseFunc != nil {
+			accountReleaseFunc()
+		}
+
+		if err != nil {
+			var failoverErr *service.UpstreamFailoverError
+			if errors.As(err, &failoverErr) {
+				// Can't failover if streaming content already sent
+				if c.Writer.Size() != writerSizeBeforeForward {
+					h.handleResponsesFailoverExhausted(c, failoverErr, true)
+					return
+				}
+				action := fs.HandleFailoverError(c.Request.Context(), h.gatewayService, account.ID, account.Platform, failoverErr)
+				switch action {
+				case FailoverContinue:
+					continue
+				case FailoverExhausted:
+					h.handleResponsesFailoverExhausted(c, fs.LastFailoverErr, streamStarted)
+					return
+				case FailoverCanceled:
+					return
+				}
+			}
+			h.ensureForwardErrorResponse(c, streamStarted)
+			reqLog.Error("gateway.responses.forward_failed",
+				zap.Int64("account_id", account.ID),
+				zap.Error(err),
+			)
+			return
+		}
+
+		// 6. Record usage
+		userAgent := c.GetHeader("User-Agent")
+		clientIP := ip.GetClientIP(c)
+		requestPayloadHash := service.HashUsageRequestPayload(body)
+		inboundEndpoint := GetInboundEndpoint(c)
+		upstreamEndpoint := GetUpstreamEndpoint(c, account.Platform)
+
+		h.submitUsageRecordTask(func(ctx context.Context) {
+			if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
+				Result:             result,
+				APIKey:             apiKey,
+				User:               apiKey.User,
+				Account:            account,
+				Subscription:       subscription,
+				InboundEndpoint:    inboundEndpoint,
+				UpstreamEndpoint:   upstreamEndpoint,
+				UserAgent:          userAgent,
+				IPAddress:          clientIP,
+				RequestPayloadHash: requestPayloadHash,
+				APIKeyService:      h.apiKeyService,
+			}); err != nil {
+				reqLog.Error("gateway.responses.record_usage_failed",
+					zap.Int64("account_id", account.ID),
+					zap.Error(err),
+				)
+			}
+		})
+		return
+	}
+}
+
+// responsesErrorResponse writes an error in OpenAI Responses API format.
+func (h *GatewayHandler) responsesErrorResponse(c *gin.Context, status int, code, message string) {
+	c.JSON(status, gin.H{
+		"error": gin.H{
+			"code":    code,
+			"message": message,
+		},
+	})
+}
+
+// handleResponsesFailoverExhausted writes a failover-exhausted error in Responses format.
+func (h *GatewayHandler) handleResponsesFailoverExhausted(c *gin.Context, lastErr *service.UpstreamFailoverError, streamStarted bool) {
+	if streamStarted {
+		return // Can't write error after stream started
+	}
+	statusCode := http.StatusBadGateway
+	if lastErr != nil && lastErr.StatusCode > 0 {
+		statusCode = lastErr.StatusCode
+	}
+	h.responsesErrorResponse(c, statusCode, "server_error", "All available accounts exhausted")
+}

backend/internal/handler/gemini_v1beta_handler.go

@@ -182,6 +182,7 @@ func (h *GatewayHandler) GeminiV1BetaModels(c *gin.Context) {
 	}
 
 	setOpsRequestContext(c, modelName, stream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(stream, false)))
 
 	// Get subscription (may be nil)
 	subscription, _ := middleware.GetSubscriptionFromContext(c)

backend/internal/handler/openai_chat_completions.go

@@ -77,6 +77,7 @@ func (h *OpenAIGatewayHandler) ChatCompletions(c *gin.Context) {
 	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
 
 	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
 
 	if h.errorPassthroughService != nil {
 		service.BindErrorPassthroughService(c, h.errorPassthroughService)

backend/internal/handler/openai_gateway_handler.go

@@ -183,6 +183,7 @@ func (h *OpenAIGatewayHandler) Responses(c *gin.Context) {
 	}
 
 	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
 
 	// 提前校验 function_call_output 是否具备可关联上下文，避免上游 400。
 	if !h.validateFunctionCallOutputRequest(c, body, reqLog) {
@@ -545,6 +546,7 @@ func (h *OpenAIGatewayHandler) Messages(c *gin.Context) {
 	reqLog = reqLog.With(zap.String("model", reqModel), zap.Bool("stream", reqStream))
 
 	setOpsRequestContext(c, reqModel, reqStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(reqStream, false)))
 
 	// 绑定错误透传服务，允许 service 层在非 failover 错误场景复用规则。
 	if h.errorPassthroughService != nil {
@@ -1096,6 +1098,7 @@ func (h *OpenAIGatewayHandler) ResponsesWebSocket(c *gin.Context) {
 		zap.String("previous_response_id_kind", previousResponseIDKind),
 	)
 	setOpsRequestContext(c, reqModel, true, firstMessage)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeWSV2))
 
 	var currentUserRelease func()
 	var currentAccountRelease func()

backend/internal/handler/ops_error_logger.go

@@ -27,6 +27,9 @@ const (
 	opsRequestBodyKey = "ops_request_body"
 	opsAccountIDKey   = "ops_account_id"
 
+	opsUpstreamModelKey = "ops_upstream_model"
+	opsRequestTypeKey   = "ops_request_type"
+
 	// 错误过滤匹配常量 — shouldSkipOpsErrorLog 和错误分类共用
 	opsErrContextCanceled            = "context canceled"
 	opsErrNoAvailableAccounts        = "no available accounts"
@@ -345,6 +348,18 @@ func setOpsRequestContext(c *gin.Context, model string, stream bool, requestBody
 	}
 }
 
+// setOpsEndpointContext stores upstream model and request type for ops error logging.
+// Called by handlers after model mapping and request type determination.
+func setOpsEndpointContext(c *gin.Context, upstreamModel string, requestType int16) {
+	if c == nil {
+		return
+	}
+	if upstreamModel = strings.TrimSpace(upstreamModel); upstreamModel != "" {
+		c.Set(opsUpstreamModelKey, upstreamModel)
+	}
+	c.Set(opsRequestTypeKey, requestType)
+}
+
 func attachOpsRequestBodyToEntry(c *gin.Context, entry *service.OpsInsertErrorLogInput) {
 	if c == nil || entry == nil {
 		return
@@ -628,7 +643,30 @@ func OpsErrorLoggerMiddleware(ops *service.OpsService) gin.HandlerFunc {
 					}
 					return ""
 				}(),
-				Stream:    stream,
+				Stream:           stream,
+				InboundEndpoint:  GetInboundEndpoint(c),
+				UpstreamEndpoint: GetUpstreamEndpoint(c, platform),
+				RequestedModel:   modelName,
+				UpstreamModel: func() string {
+					if v, ok := c.Get(opsUpstreamModelKey); ok {
+						if s, ok := v.(string); ok {
+							return strings.TrimSpace(s)
+						}
+					}
+					return ""
+				}(),
+				RequestType: func() *int16 {
+					if v, ok := c.Get(opsRequestTypeKey); ok {
+						switch t := v.(type) {
+						case int16:
+							return &t
+						case int:
+							v16 := int16(t)
+							return &v16
+						}
+					}
+					return nil
+				}(),
 				UserAgent: c.GetHeader("User-Agent"),
 
 				ErrorPhase: "upstream",
@@ -756,7 +794,30 @@ func OpsErrorLoggerMiddleware(ops *service.OpsService) gin.HandlerFunc {
 				}
 				return ""
 			}(),
-			Stream:    stream,
+			Stream:           stream,
+			InboundEndpoint:  GetInboundEndpoint(c),
+			UpstreamEndpoint: GetUpstreamEndpoint(c, platform),
+			RequestedModel:   modelName,
+			UpstreamModel: func() string {
+				if v, ok := c.Get(opsUpstreamModelKey); ok {
+					if s, ok := v.(string); ok {
+						return strings.TrimSpace(s)
+					}
+				}
+				return ""
+			}(),
+			RequestType: func() *int16 {
+				if v, ok := c.Get(opsRequestTypeKey); ok {
+					switch t := v.(type) {
+					case int16:
+						return &t
+					case int:
+						v16 := int16(t)
+						return &v16
+					}
+				}
+				return nil
+			}(),
 			UserAgent: c.GetHeader("User-Agent"),
 
 			ErrorPhase:        phase,

backend/internal/handler/ops_error_logger_test.go

@@ -274,3 +274,48 @@ func TestNormalizeOpsErrorType(t *testing.T) {
 		})
 	}
 }
+
+func TestSetOpsEndpointContext_SetsContextKeys(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", nil)
+
+	setOpsEndpointContext(c, "claude-3-5-sonnet-20241022", int16(2)) // stream
+
+	v, ok := c.Get(opsUpstreamModelKey)
+	require.True(t, ok)
+	vStr, ok := v.(string)
+	require.True(t, ok)
+	require.Equal(t, "claude-3-5-sonnet-20241022", vStr)
+
+	rt, ok := c.Get(opsRequestTypeKey)
+	require.True(t, ok)
+	rtVal, ok := rt.(int16)
+	require.True(t, ok)
+	require.Equal(t, int16(2), rtVal)
+}
+
+func TestSetOpsEndpointContext_EmptyModelNotStored(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+	c.Request = httptest.NewRequest(http.MethodPost, "/v1/messages", nil)
+
+	setOpsEndpointContext(c, "", int16(1))
+
+	_, ok := c.Get(opsUpstreamModelKey)
+	require.False(t, ok, "empty upstream model should not be stored")
+
+	rt, ok := c.Get(opsRequestTypeKey)
+	require.True(t, ok)
+	rtVal, ok := rt.(int16)
+	require.True(t, ok)
+	require.Equal(t, int16(1), rtVal)
+}
+
+func TestSetOpsEndpointContext_NilContext(t *testing.T) {
+	require.NotPanics(t, func() {
+		setOpsEndpointContext(nil, "model", int16(1))
+	})
+}

backend/internal/handler/sora_gateway_handler.go

@@ -159,6 +159,7 @@ func (h *SoraGatewayHandler) ChatCompletions(c *gin.Context) {
 	}
 
 	setOpsRequestContext(c, reqModel, clientStream, body)
+	setOpsEndpointContext(c, "", int16(service.RequestTypeFromLegacy(clientStream, false)))
 
 	platform := ""
 	if forced, ok := middleware2.GetForcePlatformFromContext(c); ok {

backend/internal/pkg/apicompat/anthropic_to_responses_response.go

+package apicompat
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"fmt"
+	"time"
+)
+
+// ---------------------------------------------------------------------------
+// Non-streaming: AnthropicResponse → ResponsesResponse
+// ---------------------------------------------------------------------------
+
+// AnthropicToResponsesResponse converts an Anthropic Messages response into a
+// Responses API response. This is the reverse of ResponsesToAnthropic and
+// enables Anthropic upstream responses to be returned in OpenAI Responses format.
+func AnthropicToResponsesResponse(resp *AnthropicResponse) *ResponsesResponse {
+	id := resp.ID
+	if id == "" {
+		id = generateResponsesID()
+	}
+
+	out := &ResponsesResponse{
+		ID:     id,
+		Object: "response",
+		Model:  resp.Model,
+	}
+
+	var outputs []ResponsesOutput
+	var msgParts []ResponsesContentPart
+
+	for _, block := range resp.Content {
+		switch block.Type {
+		case "thinking":
+			if block.Thinking != "" {
+				outputs = append(outputs, ResponsesOutput{
+					Type: "reasoning",
+					ID:   generateItemID(),
+					Summary: []ResponsesSummary{{
+						Type: "summary_text",
+						Text: block.Thinking,
+					}},
+				})
+			}
+		case "text":
+			if block.Text != "" {
+				msgParts = append(msgParts, ResponsesContentPart{
+					Type: "output_text",
+					Text: block.Text,
+				})
+			}
+		case "tool_use":
+			args := "{}"
+			if len(block.Input) > 0 {
+				args = string(block.Input)
+			}
+			outputs = append(outputs, ResponsesOutput{
+				Type:      "function_call",
+				ID:        generateItemID(),
+				CallID:    toResponsesCallID(block.ID),
+				Name:      block.Name,
+				Arguments: args,
+				Status:    "completed",
+			})
+		}
+	}
+
+	// Assemble message output item from text parts
+	if len(msgParts) > 0 {
+		outputs = append(outputs, ResponsesOutput{
+			Type:    "message",
+			ID:      generateItemID(),
+			Role:    "assistant",
+			Content: msgParts,
+			Status:  "completed",
+		})
+	}
+
+	if len(outputs) == 0 {
+		outputs = append(outputs, ResponsesOutput{
+			Type:    "message",
+			ID:      generateItemID(),
+			Role:    "assistant",
+			Content: []ResponsesContentPart{{Type: "output_text", Text: ""}},
+			Status:  "completed",
+		})
+	}
+	out.Output = outputs
+
+	// Map stop_reason → status
+	out.Status = anthropicStopReasonToResponsesStatus(resp.StopReason, resp.Content)
+	if out.Status == "incomplete" {
+		out.IncompleteDetails = &ResponsesIncompleteDetails{Reason: "max_output_tokens"}
+	}
+
+	// Usage
+	out.Usage = &ResponsesUsage{
+		InputTokens:  resp.Usage.InputTokens,
+		OutputTokens: resp.Usage.OutputTokens,
+		TotalTokens:  resp.Usage.InputTokens + resp.Usage.OutputTokens,
+	}
+	if resp.Usage.CacheReadInputTokens > 0 {
+		out.Usage.InputTokensDetails = &ResponsesInputTokensDetails{
+			CachedTokens: resp.Usage.CacheReadInputTokens,
+		}
+	}
+
+	return out
+}
+
+// anthropicStopReasonToResponsesStatus maps Anthropic stop_reason to Responses status.
+func anthropicStopReasonToResponsesStatus(stopReason string, blocks []AnthropicContentBlock) string {
+	switch stopReason {
+	case "max_tokens":
+		return "incomplete"
+	case "end_turn", "tool_use", "stop_sequence":
+		return "completed"
+	default:
+		return "completed"
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Streaming: AnthropicStreamEvent → []ResponsesStreamEvent (stateful converter)
+// ---------------------------------------------------------------------------
+
+// AnthropicEventToResponsesState tracks state for converting a sequence of
+// Anthropic SSE events into Responses SSE events.
+type AnthropicEventToResponsesState struct {
+	ResponseID     string
+	Model          string
+	Created        int64
+	SequenceNumber int
+
+	// CreatedSent tracks whether response.created has been emitted.
+	CreatedSent bool
+	// CompletedSent tracks whether the terminal event has been emitted.
+	CompletedSent bool
+
+	// Current output tracking
+	OutputIndex     int
+	CurrentItemID   string
+	CurrentItemType string // "message" | "function_call" | "reasoning"
+
+	// For message output: accumulate text parts
+	ContentIndex int
+
+	// For function_call: track per-output info
+	CurrentCallID string
+	CurrentName   string
+
+	// Usage from message_delta
+	InputTokens          int
+	OutputTokens         int
+	CacheReadInputTokens int
+}
+
+// NewAnthropicEventToResponsesState returns an initialised stream state.
+func NewAnthropicEventToResponsesState() *AnthropicEventToResponsesState {
+	return &AnthropicEventToResponsesState{
+		Created: time.Now().Unix(),
+	}
+}
+
+// AnthropicEventToResponsesEvents converts a single Anthropic SSE event into
+// zero or more Responses SSE events, updating state as it goes.
+func AnthropicEventToResponsesEvents(
+	evt *AnthropicStreamEvent,
+	state *AnthropicEventToResponsesState,
+) []ResponsesStreamEvent {
+	switch evt.Type {
+	case "message_start":
+		return anthToResHandleMessageStart(evt, state)
+	case "content_block_start":
+		return anthToResHandleContentBlockStart(evt, state)
+	case "content_block_delta":
+		return anthToResHandleContentBlockDelta(evt, state)
+	case "content_block_stop":
+		return anthToResHandleContentBlockStop(evt, state)
+	case "message_delta":
+		return anthToResHandleMessageDelta(evt, state)
+	case "message_stop":
+		return anthToResHandleMessageStop(state)
+	default:
+		return nil
+	}
+}
+
+// FinalizeAnthropicResponsesStream emits synthetic termination events if the
+// stream ended without a proper message_stop.
+func FinalizeAnthropicResponsesStream(state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if !state.CreatedSent || state.CompletedSent {
+		return nil
+	}
+
+	var events []ResponsesStreamEvent
+
+	// Close any open item
+	events = append(events, closeCurrentResponsesItem(state)...)
+
+	// Emit response.completed
+	events = append(events, makeResponsesCompletedEvent(state, "completed", nil))
+	state.CompletedSent = true
+	return events
+}
+
+// ResponsesEventToSSE formats a ResponsesStreamEvent as an SSE data line.
+func ResponsesEventToSSE(evt ResponsesStreamEvent) (string, error) {
+	data, err := json.Marshal(evt)
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("event: %s\ndata: %s\n\n", evt.Type, data), nil
+}
+
+// --- internal handlers ---
+
+func anthToResHandleMessageStart(evt *AnthropicStreamEvent, state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if evt.Message != nil {
+		state.ResponseID = evt.Message.ID
+		if state.Model == "" {
+			state.Model = evt.Message.Model
+		}
+		if evt.Message.Usage.InputTokens > 0 {
+			state.InputTokens = evt.Message.Usage.InputTokens
+		}
+	}
+
+	if state.CreatedSent {
+		return nil
+	}
+	state.CreatedSent = true
+
+	// Emit response.created
+	return []ResponsesStreamEvent{makeResponsesCreatedEvent(state)}
+}
+
+func anthToResHandleContentBlockStart(evt *AnthropicStreamEvent, state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if evt.ContentBlock == nil {
+		return nil
+	}
+
+	var events []ResponsesStreamEvent
+
+	switch evt.ContentBlock.Type {
+	case "thinking":
+		state.CurrentItemID = generateItemID()
+		state.CurrentItemType = "reasoning"
+		state.ContentIndex = 0
+
+		events = append(events, makeResponsesEvent(state, "response.output_item.added", &ResponsesStreamEvent{
+			OutputIndex: state.OutputIndex,
+			Item: &ResponsesOutput{
+				Type: "reasoning",
+				ID:   state.CurrentItemID,
+			},
+		}))
+
+	case "text":
+		// If we don't have an open message item, open one
+		if state.CurrentItemType != "message" {
+			state.CurrentItemID = generateItemID()
+			state.CurrentItemType = "message"
+			state.ContentIndex = 0
+
+			events = append(events, makeResponsesEvent(state, "response.output_item.added", &ResponsesStreamEvent{
+				OutputIndex: state.OutputIndex,
+				Item: &ResponsesOutput{
+					Type:   "message",
+					ID:     state.CurrentItemID,
+					Role:   "assistant",
+					Status: "in_progress",
+				},
+			}))
+		}
+
+	case "tool_use":
+		// Close previous item if any
+		events = append(events, closeCurrentResponsesItem(state)...)
+
+		state.CurrentItemID = generateItemID()
+		state.CurrentItemType = "function_call"
+		state.CurrentCallID = toResponsesCallID(evt.ContentBlock.ID)
+		state.CurrentName = evt.ContentBlock.Name
+
+		events = append(events, makeResponsesEvent(state, "response.output_item.added", &ResponsesStreamEvent{
+			OutputIndex: state.OutputIndex,
+			Item: &ResponsesOutput{
+				Type:   "function_call",
+				ID:     state.CurrentItemID,
+				CallID: state.CurrentCallID,
+				Name:   state.CurrentName,
+				Status: "in_progress",
+			},
+		}))
+	}
+
+	return events
+}
+
+func anthToResHandleContentBlockDelta(evt *AnthropicStreamEvent, state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if evt.Delta == nil {
+		return nil
+	}
+
+	switch evt.Delta.Type {
+	case "text_delta":
+		if evt.Delta.Text == "" {
+			return nil
+		}
+		return []ResponsesStreamEvent{makeResponsesEvent(state, "response.output_text.delta", &ResponsesStreamEvent{
+			OutputIndex:  state.OutputIndex,
+			ContentIndex: state.ContentIndex,
+			Delta:        evt.Delta.Text,
+			ItemID:       state.CurrentItemID,
+		})}
+
+	case "thinking_delta":
+		if evt.Delta.Thinking == "" {
+			return nil
+		}
+		return []ResponsesStreamEvent{makeResponsesEvent(state, "response.reasoning_summary_text.delta", &ResponsesStreamEvent{
+			OutputIndex:  state.OutputIndex,
+			SummaryIndex: 0,
+			Delta:        evt.Delta.Thinking,
+			ItemID:       state.CurrentItemID,
+		})}
+
+	case "input_json_delta":
+		if evt.Delta.PartialJSON == "" {
+			return nil
+		}
+		return []ResponsesStreamEvent{makeResponsesEvent(state, "response.function_call_arguments.delta", &ResponsesStreamEvent{
+			OutputIndex: state.OutputIndex,
+			Delta:       evt.Delta.PartialJSON,
+			ItemID:      state.CurrentItemID,
+			CallID:      state.CurrentCallID,
+			Name:        state.CurrentName,
+		})}
+
+	case "signature_delta":
+		// Anthropic signature deltas have no Responses equivalent; skip
+		return nil
+	}
+
+	return nil
+}
+
+func anthToResHandleContentBlockStop(evt *AnthropicStreamEvent, state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	switch state.CurrentItemType {
+	case "reasoning":
+		// Emit reasoning summary done + output item done
+		events := []ResponsesStreamEvent{
+			makeResponsesEvent(state, "response.reasoning_summary_text.done", &ResponsesStreamEvent{
+				OutputIndex:  state.OutputIndex,
+				SummaryIndex: 0,
+				ItemID:       state.CurrentItemID,
+			}),
+		}
+		events = append(events, closeCurrentResponsesItem(state)...)
+		return events
+
+	case "function_call":
+		// Emit function_call_arguments.done + output item done
+		events := []ResponsesStreamEvent{
+			makeResponsesEvent(state, "response.function_call_arguments.done", &ResponsesStreamEvent{
+				OutputIndex: state.OutputIndex,
+				ItemID:      state.CurrentItemID,
+				CallID:      state.CurrentCallID,
+				Name:        state.CurrentName,
+			}),
+		}
+		events = append(events, closeCurrentResponsesItem(state)...)
+		return events
+
+	case "message":
+		// Emit output_text.done (text block is done, but message item stays open for potential more blocks)
+		return []ResponsesStreamEvent{
+			makeResponsesEvent(state, "response.output_text.done", &ResponsesStreamEvent{
+				OutputIndex:  state.OutputIndex,
+				ContentIndex: state.ContentIndex,
+				ItemID:       state.CurrentItemID,
+			}),
+		}
+	}
+
+	return nil
+}
+
+func anthToResHandleMessageDelta(evt *AnthropicStreamEvent, state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	// Update usage
+	if evt.Usage != nil {
+		state.OutputTokens = evt.Usage.OutputTokens
+		if evt.Usage.CacheReadInputTokens > 0 {
+			state.CacheReadInputTokens = evt.Usage.CacheReadInputTokens
+		}
+	}
+
+	return nil
+}
+
+func anthToResHandleMessageStop(state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if state.CompletedSent {
+		return nil
+	}
+
+	var events []ResponsesStreamEvent
+
+	// Close any open item
+	events = append(events, closeCurrentResponsesItem(state)...)
+
+	// Determine status
+	status := "completed"
+	var incompleteDetails *ResponsesIncompleteDetails
+
+	// Emit response.completed
+	events = append(events, makeResponsesCompletedEvent(state, status, incompleteDetails))
+	state.CompletedSent = true
+	return events
+}
+
+// --- helper functions ---
+
+func closeCurrentResponsesItem(state *AnthropicEventToResponsesState) []ResponsesStreamEvent {
+	if state.CurrentItemType == "" {
+		return nil
+	}
+
+	itemType := state.CurrentItemType
+	itemID := state.CurrentItemID
+
+	// Reset
+	state.CurrentItemType = ""
+	state.CurrentItemID = ""
+	state.CurrentCallID = ""
+	state.CurrentName = ""
+	state.OutputIndex++
+	state.ContentIndex = 0
+
+	return []ResponsesStreamEvent{makeResponsesEvent(state, "response.output_item.done", &ResponsesStreamEvent{
+		OutputIndex: state.OutputIndex - 1, // Use the index before increment
+		Item: &ResponsesOutput{
+			Type:   itemType,
+			ID:     itemID,
+			Status: "completed",
+		},
+	})}
+}
+
+func makeResponsesCreatedEvent(state *AnthropicEventToResponsesState) ResponsesStreamEvent {
+	seq := state.SequenceNumber
+	state.SequenceNumber++
+	return ResponsesStreamEvent{
+		Type:           "response.created",
+		SequenceNumber: seq,
+		Response: &ResponsesResponse{
+			ID:     state.ResponseID,
+			Object: "response",
+			Model:  state.Model,
+			Status: "in_progress",
+			Output: []ResponsesOutput{},
+		},
+	}
+}
+
+func makeResponsesCompletedEvent(
+	state *AnthropicEventToResponsesState,
+	status string,
+	incompleteDetails *ResponsesIncompleteDetails,
+) ResponsesStreamEvent {
+	seq := state.SequenceNumber
+	state.SequenceNumber++
+
+	usage := &ResponsesUsage{
+		InputTokens:  state.InputTokens,
+		OutputTokens: state.OutputTokens,
+		TotalTokens:  state.InputTokens + state.OutputTokens,
+	}
+	if state.CacheReadInputTokens > 0 {
+		usage.InputTokensDetails = &ResponsesInputTokensDetails{
+			CachedTokens: state.CacheReadInputTokens,
+		}
+	}
+
+	return ResponsesStreamEvent{
+		Type:           "response.completed",
+		SequenceNumber: seq,
+		Response: &ResponsesResponse{
+			ID:                state.ResponseID,
+			Object:            "response",
+			Model:             state.Model,
+			Status:            status,
+			Output:            []ResponsesOutput{}, // Simplified; full output tracking would add complexity
+			Usage:             usage,
+			IncompleteDetails: incompleteDetails,
+		},
+	}
+}
+
+func makeResponsesEvent(state *AnthropicEventToResponsesState, eventType string, template *ResponsesStreamEvent) ResponsesStreamEvent {
+	seq := state.SequenceNumber
+	state.SequenceNumber++
+
+	evt := *template
+	evt.Type = eventType
+	evt.SequenceNumber = seq
+	return evt
+}
+
+func generateResponsesID() string {
+	b := make([]byte, 12)
+	_, _ = rand.Read(b)
+	return "resp_" + hex.EncodeToString(b)
+}
+
+func generateItemID() string {
+	b := make([]byte, 12)
+	_, _ = rand.Read(b)
+	return "item_" + hex.EncodeToString(b)
+}

backend/internal/pkg/apicompat/responses_to_anthropic_request.go

+package apicompat
+
+import (
+	"encoding/json"
+	"fmt"
+	"strings"
+)
+
+// ResponsesToAnthropicRequest converts a Responses API request into an
+// Anthropic Messages request. This is the reverse of AnthropicToResponses and
+// enables Anthropic platform groups to accept OpenAI Responses API requests
+// by converting them to the native /v1/messages format before forwarding upstream.
+func ResponsesToAnthropicRequest(req *ResponsesRequest) (*AnthropicRequest, error) {
+	system, messages, err := convertResponsesInputToAnthropic(req.Input)
+	if err != nil {
+		return nil, err
+	}
+
+	out := &AnthropicRequest{
+		Model:       req.Model,
+		Messages:    messages,
+		Temperature: req.Temperature,
+		TopP:        req.TopP,
+		Stream:      req.Stream,
+	}
+
+	if len(system) > 0 {
+		out.System = system
+	}
+
+	// max_output_tokens → max_tokens
+	if req.MaxOutputTokens != nil && *req.MaxOutputTokens > 0 {
+		out.MaxTokens = *req.MaxOutputTokens
+	}
+	if out.MaxTokens == 0 {
+		// Anthropic requires max_tokens; default to a sensible value.
+		out.MaxTokens = 8192
+	}
+
+	// Convert tools
+	if len(req.Tools) > 0 {
+		out.Tools = convertResponsesToAnthropicTools(req.Tools)
+	}
+
+	// Convert tool_choice (reverse of convertAnthropicToolChoiceToResponses)
+	if len(req.ToolChoice) > 0 {
+		tc, err := convertResponsesToAnthropicToolChoice(req.ToolChoice)
+		if err != nil {
+			return nil, fmt.Errorf("convert tool_choice: %w", err)
+		}
+		out.ToolChoice = tc
+	}
+
+	// reasoning.effort → output_config.effort + thinking
+	if req.Reasoning != nil && req.Reasoning.Effort != "" {
+		effort := mapResponsesEffortToAnthropic(req.Reasoning.Effort)
+		out.OutputConfig = &AnthropicOutputConfig{Effort: effort}
+		// Enable thinking for non-low efforts
+		if effort != "low" {
+			out.Thinking = &AnthropicThinking{
+				Type:         "enabled",
+				BudgetTokens: defaultThinkingBudget(effort),
+			}
+		}
+	}
+
+	return out, nil
+}
+
+// defaultThinkingBudget returns a sensible thinking budget based on effort level.
+func defaultThinkingBudget(effort string) int {
+	switch effort {
+	case "low":
+		return 1024
+	case "medium":
+		return 4096
+	case "high":
+		return 10240
+	case "max":
+		return 32768
+	default:
+		return 10240
+	}
+}
+
+// mapResponsesEffortToAnthropic converts OpenAI Responses reasoning effort to
+// Anthropic effort levels. Reverse of mapAnthropicEffortToResponses.
+//
+//	low    → low
+//	medium → medium
+//	high   → high
+//	xhigh  → max
+func mapResponsesEffortToAnthropic(effort string) string {
+	if effort == "xhigh" {
+		return "max"
+	}
+	return effort // low→low, medium→medium, high→high, unknown→passthrough
+}
+
+// convertResponsesInputToAnthropic extracts system prompt and messages from
+// a Responses API input array. Returns the system as raw JSON (for Anthropic's
+// polymorphic system field) and a list of Anthropic messages.
+func convertResponsesInputToAnthropic(inputRaw json.RawMessage) (json.RawMessage, []AnthropicMessage, error) {
+	// Try as plain string input.
+	var inputStr string
+	if err := json.Unmarshal(inputRaw, &inputStr); err == nil {
+		content, _ := json.Marshal(inputStr)
+		return nil, []AnthropicMessage{{Role: "user", Content: content}}, nil
+	}
+
+	var items []ResponsesInputItem
+	if err := json.Unmarshal(inputRaw, &items); err != nil {
+		return nil, nil, fmt.Errorf("parse responses input: %w", err)
+	}
+
+	var system json.RawMessage
+	var messages []AnthropicMessage
+
+	for _, item := range items {
+		switch {
+		case item.Role == "system":
+			// System prompt → Anthropic system field
+			text := extractTextFromContent(item.Content)
+			if text != "" {
+				system, _ = json.Marshal(text)
+			}
+
+		case item.Type == "function_call":
+			// function_call → assistant message with tool_use block
+			input := json.RawMessage("{}")
+			if item.Arguments != "" {
+				input = json.RawMessage(item.Arguments)
+			}
+			block := AnthropicContentBlock{
+				Type:  "tool_use",
+				ID:    fromResponsesCallIDToAnthropic(item.CallID),
+				Name:  item.Name,
+				Input: input,
+			}
+			blockJSON, _ := json.Marshal([]AnthropicContentBlock{block})
+			messages = append(messages, AnthropicMessage{
+				Role:    "assistant",
+				Content: blockJSON,
+			})
+
+		case item.Type == "function_call_output":
+			// function_call_output → user message with tool_result block
+			outputContent := item.Output
+			if outputContent == "" {
+				outputContent = "(empty)"
+			}
+			contentJSON, _ := json.Marshal(outputContent)
+			block := AnthropicContentBlock{
+				Type:      "tool_result",
+				ToolUseID: fromResponsesCallIDToAnthropic(item.CallID),
+				Content:   contentJSON,
+			}
+			blockJSON, _ := json.Marshal([]AnthropicContentBlock{block})
+			messages = append(messages, AnthropicMessage{
+				Role:    "user",
+				Content: blockJSON,
+			})
+
+		case item.Role == "user":
+			content, err := convertResponsesUserToAnthropicContent(item.Content)
+			if err != nil {
+				return nil, nil, err
+			}
+			messages = append(messages, AnthropicMessage{
+				Role:    "user",
+				Content: content,
+			})
+
+		case item.Role == "assistant":
+			content, err := convertResponsesAssistantToAnthropicContent(item.Content)
+			if err != nil {
+				return nil, nil, err
+			}
+			messages = append(messages, AnthropicMessage{
+				Role:    "assistant",
+				Content: content,
+			})
+
+		default:
+			// Unknown role/type — attempt as user message
+			if item.Content != nil {
+				messages = append(messages, AnthropicMessage{
+					Role:    "user",
+					Content: item.Content,
+				})
+			}
+		}
+	}
+
+	// Merge consecutive same-role messages (Anthropic requires alternating roles)
+	messages = mergeConsecutiveMessages(messages)
+
+	return system, messages, nil
+}
+
+// extractTextFromContent extracts text from a content field that may be a
+// plain string or an array of content parts.
+func extractTextFromContent(raw json.RawMessage) string {
+	if len(raw) == 0 {
+		return ""
+	}
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		return s
+	}
+	var parts []ResponsesContentPart
+	if err := json.Unmarshal(raw, &parts); err == nil {
+		var texts []string
+		for _, p := range parts {
+			if (p.Type == "input_text" || p.Type == "output_text" || p.Type == "text") && p.Text != "" {
+				texts = append(texts, p.Text)
+			}
+		}
+		return strings.Join(texts, "\n\n")
+	}
+	return ""
+}
+
+// convertResponsesUserToAnthropicContent converts a Responses user message
+// content field into Anthropic content blocks JSON.
+func convertResponsesUserToAnthropicContent(raw json.RawMessage) (json.RawMessage, error) {
+	if len(raw) == 0 {
+		return json.Marshal("") // empty string content
+	}
+
+	// Try plain string.
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		return json.Marshal(s)
+	}
+
+	// Array of content parts → Anthropic content blocks.
+	var parts []ResponsesContentPart
+	if err := json.Unmarshal(raw, &parts); err != nil {
+		// Pass through as-is if we can't parse
+		return raw, nil
+	}
+
+	var blocks []AnthropicContentBlock
+	for _, p := range parts {
+		switch p.Type {
+		case "input_text", "text":
+			if p.Text != "" {
+				blocks = append(blocks, AnthropicContentBlock{
+					Type: "text",
+					Text: p.Text,
+				})
+			}
+		case "input_image":
+			src := dataURIToAnthropicImageSource(p.ImageURL)
+			if src != nil {
+				blocks = append(blocks, AnthropicContentBlock{
+					Type:   "image",
+					Source: src,
+				})
+			}
+		}
+	}
+
+	if len(blocks) == 0 {
+		return json.Marshal("")
+	}
+	return json.Marshal(blocks)
+}
+
+// convertResponsesAssistantToAnthropicContent converts a Responses assistant
+// message content field into Anthropic content blocks JSON.
+func convertResponsesAssistantToAnthropicContent(raw json.RawMessage) (json.RawMessage, error) {
+	if len(raw) == 0 {
+		return json.Marshal([]AnthropicContentBlock{{Type: "text", Text: ""}})
+	}
+
+	// Try plain string.
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		return json.Marshal([]AnthropicContentBlock{{Type: "text", Text: s}})
+	}
+
+	// Array of content parts → Anthropic content blocks.
+	var parts []ResponsesContentPart
+	if err := json.Unmarshal(raw, &parts); err != nil {
+		return raw, nil
+	}
+
+	var blocks []AnthropicContentBlock
+	for _, p := range parts {
+		switch p.Type {
+		case "output_text", "text":
+			if p.Text != "" {
+				blocks = append(blocks, AnthropicContentBlock{
+					Type: "text",
+					Text: p.Text,
+				})
+			}
+		}
+	}
+
+	if len(blocks) == 0 {
+		blocks = append(blocks, AnthropicContentBlock{Type: "text", Text: ""})
+	}
+	return json.Marshal(blocks)
+}
+
+// fromResponsesCallIDToAnthropic converts an OpenAI function call ID back to
+// Anthropic format. Reverses toResponsesCallID.
+func fromResponsesCallIDToAnthropic(id string) string {
+	// If it has our "fc_" prefix wrapping a known Anthropic prefix, strip it
+	if after, ok := strings.CutPrefix(id, "fc_"); ok {
+		if strings.HasPrefix(after, "toolu_") || strings.HasPrefix(after, "call_") {
+			return after
+		}
+	}
+	// Generate a synthetic Anthropic tool ID
+	if !strings.HasPrefix(id, "toolu_") && !strings.HasPrefix(id, "call_") {
+		return "toolu_" + id
+	}
+	return id
+}
+
+// dataURIToAnthropicImageSource parses a data URI into an AnthropicImageSource.
+func dataURIToAnthropicImageSource(dataURI string) *AnthropicImageSource {
+	if !strings.HasPrefix(dataURI, "data:") {
+		return nil
+	}
+	// Format: data:<media_type>;base64,<data>
+	rest := strings.TrimPrefix(dataURI, "data:")
+	semicolonIdx := strings.Index(rest, ";")
+	if semicolonIdx < 0 {
+		return nil
+	}
+	mediaType := rest[:semicolonIdx]
+	rest = rest[semicolonIdx+1:]
+	if !strings.HasPrefix(rest, "base64,") {
+		return nil
+	}
+	data := strings.TrimPrefix(rest, "base64,")
+	return &AnthropicImageSource{
+		Type:      "base64",
+		MediaType: mediaType,
+		Data:      data,
+	}
+}
+
+// mergeConsecutiveMessages merges consecutive messages with the same role
+// because Anthropic requires alternating user/assistant turns.
+func mergeConsecutiveMessages(messages []AnthropicMessage) []AnthropicMessage {
+	if len(messages) <= 1 {
+		return messages
+	}
+
+	var merged []AnthropicMessage
+	for _, msg := range messages {
+		if len(merged) == 0 || merged[len(merged)-1].Role != msg.Role {
+			merged = append(merged, msg)
+			continue
+		}
+
+		// Same role — merge content arrays
+		last := &merged[len(merged)-1]
+		lastBlocks := parseContentBlocks(last.Content)
+		newBlocks := parseContentBlocks(msg.Content)
+		combined := append(lastBlocks, newBlocks...)
+		last.Content, _ = json.Marshal(combined)
+	}
+	return merged
+}
+
+// parseContentBlocks attempts to parse content as []AnthropicContentBlock.
+// If it's a string, wraps it in a text block.
+func parseContentBlocks(raw json.RawMessage) []AnthropicContentBlock {
+	var blocks []AnthropicContentBlock
+	if err := json.Unmarshal(raw, &blocks); err == nil {
+		return blocks
+	}
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		return []AnthropicContentBlock{{Type: "text", Text: s}}
+	}
+	return nil
+}
+
+// convertResponsesToAnthropicTools maps Responses API tools to Anthropic format.
+// Reverse of convertAnthropicToolsToResponses.
+func convertResponsesToAnthropicTools(tools []ResponsesTool) []AnthropicTool {
+	var out []AnthropicTool
+	for _, t := range tools {
+		switch t.Type {
+		case "web_search":
+			out = append(out, AnthropicTool{
+				Type: "web_search_20250305",
+				Name: "web_search",
+			})
+		case "function":
+			out = append(out, AnthropicTool{
+				Name:        t.Name,
+				Description: t.Description,
+				InputSchema: normalizeAnthropicInputSchema(t.Parameters),
+			})
+		default:
+			// Pass through unknown tool types
+			out = append(out, AnthropicTool{
+				Type:        t.Type,
+				Name:        t.Name,
+				Description: t.Description,
+				InputSchema: t.Parameters,
+			})
+		}
+	}
+	return out
+}
+
+// normalizeAnthropicInputSchema ensures the input_schema has a "type" field.
+func normalizeAnthropicInputSchema(schema json.RawMessage) json.RawMessage {
+	if len(schema) == 0 || string(schema) == "null" {
+		return json.RawMessage(`{"type":"object","properties":{}}`)
+	}
+	return schema
+}
+
+// convertResponsesToAnthropicToolChoice maps Responses tool_choice to Anthropic format.
+// Reverse of convertAnthropicToolChoiceToResponses.
+//
+//	"auto"                                     → {"type":"auto"}
+//	"required"                                 → {"type":"any"}
+//	"none"                                     → {"type":"none"}
+//	{"type":"function","function":{"name":"X"}} → {"type":"tool","name":"X"}
+func convertResponsesToAnthropicToolChoice(raw json.RawMessage) (json.RawMessage, error) {
+	// Try as string first
+	var s string
+	if err := json.Unmarshal(raw, &s); err == nil {
+		switch s {
+		case "auto":
+			return json.Marshal(map[string]string{"type": "auto"})
+		case "required":
+			return json.Marshal(map[string]string{"type": "any"})
+		case "none":
+			return json.Marshal(map[string]string{"type": "none"})
+		default:
+			return raw, nil
+		}
+	}
+
+	// Try as object with type=function
+	var tc struct {
+		Type     string `json:"type"`
+		Function struct {
+			Name string `json:"name"`
+		} `json:"function"`
+	}
+	if err := json.Unmarshal(raw, &tc); err == nil && tc.Type == "function" && tc.Function.Name != "" {
+		return json.Marshal(map[string]string{
+			"type": "tool",
+			"name": tc.Function.Name,
+		})
+	}
+
+	// Pass through unknown
+	return raw, nil
+}

backend/internal/repository/ops_repo.go

@@ -29,6 +29,11 @@ INSERT INTO ops_error_logs (
   model,
   request_path,
   stream,
+  inbound_endpoint,
+  upstream_endpoint,
+  requested_model,
+  upstream_model,
+  request_type,
   user_agent,
   error_phase,
   error_type,
@@ -57,7 +62,7 @@ INSERT INTO ops_error_logs (
   retry_count,
   created_at
 ) VALUES (
-  $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30,$31,$32,$33,$34,$35,$36,$37,$38
+  $1,$2,$3,$4,$5,$6,$7,$8,$9,$10,$11,$12,$13,$14,$15,$16,$17,$18,$19,$20,$21,$22,$23,$24,$25,$26,$27,$28,$29,$30,$31,$32,$33,$34,$35,$36,$37,$38,$39,$40,$41,$42,$43
 )`
 
 func NewOpsRepository(db *sql.DB) service.OpsRepository {
@@ -140,6 +145,11 @@ func opsInsertErrorLogArgs(input *service.OpsInsertErrorLogInput) []any {
 		opsNullString(input.Model),
 		opsNullString(input.RequestPath),
 		input.Stream,
+		opsNullString(input.InboundEndpoint),
+		opsNullString(input.UpstreamEndpoint),
+		opsNullString(input.RequestedModel),
+		opsNullString(input.UpstreamModel),
+		opsNullInt16(input.RequestType),
 		opsNullString(input.UserAgent),
 		input.ErrorPhase,
 		input.ErrorType,
@@ -231,7 +241,12 @@ SELECT
   COALESCE(g.name, ''),
   CASE WHEN e.client_ip IS NULL THEN NULL ELSE e.client_ip::text END,
   COALESCE(e.request_path, ''),
-  e.stream
+  e.stream,
+  COALESCE(e.inbound_endpoint, ''),
+  COALESCE(e.upstream_endpoint, ''),
+  COALESCE(e.requested_model, ''),
+  COALESCE(e.upstream_model, ''),
+  e.request_type
 FROM ops_error_logs e
 LEFT JOIN accounts a ON e.account_id = a.id
 LEFT JOIN groups g ON e.group_id = g.id
@@ -263,6 +278,7 @@ LIMIT $` + itoa(len(args)+1) + ` OFFSET $` + itoa(len(args)+2)
 		var resolvedBy sql.NullInt64
 		var resolvedByName string
 		var resolvedRetryID sql.NullInt64
+		var requestType sql.NullInt64
 		if err := rows.Scan(
 			&item.ID,
 			&item.CreatedAt,
@@ -294,6 +310,11 @@ LIMIT $` + itoa(len(args)+1) + ` OFFSET $` + itoa(len(args)+2)
 			&clientIP,
 			&item.RequestPath,
 			&item.Stream,
+			&item.InboundEndpoint,
+			&item.UpstreamEndpoint,
+			&item.RequestedModel,
+			&item.UpstreamModel,
+			&requestType,
 		); err != nil {
 			return nil, err
 		}
@@ -334,6 +355,10 @@ LIMIT $` + itoa(len(args)+1) + ` OFFSET $` + itoa(len(args)+2)
 			item.GroupID = &v
 		}
 		item.GroupName = groupName
+		if requestType.Valid {
+			v := int16(requestType.Int64)
+			item.RequestType = &v
+		}
 		out = append(out, &item)
 	}
 	if err := rows.Err(); err != nil {
@@ -393,6 +418,11 @@ SELECT
   CASE WHEN e.client_ip IS NULL THEN NULL ELSE e.client_ip::text END,
   COALESCE(e.request_path, ''),
   e.stream,
+  COALESCE(e.inbound_endpoint, ''),
+  COALESCE(e.upstream_endpoint, ''),
+  COALESCE(e.requested_model, ''),
+  COALESCE(e.upstream_model, ''),
+  e.request_type,
   COALESCE(e.user_agent, ''),
   e.auth_latency_ms,
   e.routing_latency_ms,
@@ -427,6 +457,7 @@ LIMIT 1`
 	var responseLatency sql.NullInt64
 	var ttft sql.NullInt64
 	var requestBodyBytes sql.NullInt64
+	var requestType sql.NullInt64
 
 	err := r.db.QueryRowContext(ctx, q, id).Scan(
 		&out.ID,
@@ -464,6 +495,11 @@ LIMIT 1`
 		&clientIP,
 		&out.RequestPath,
 		&out.Stream,
+		&out.InboundEndpoint,
+		&out.UpstreamEndpoint,
+		&out.RequestedModel,
+		&out.UpstreamModel,
+		&requestType,
 		&out.UserAgent,
 		&authLatency,
 		&routingLatency,
@@ -540,6 +576,10 @@ LIMIT 1`
 		v := int(requestBodyBytes.Int64)
 		out.RequestBodyBytes = &v
 	}
+	if requestType.Valid {
+		v := int16(requestType.Int64)
+		out.RequestType = &v
+	}
 
 	// Normalize request_body to empty string when stored as JSON null.
 	out.RequestBody = strings.TrimSpace(out.RequestBody)
@@ -1479,3 +1519,10 @@ func opsNullInt(v any) any {
 		return sql.NullInt64{}
 	}
 }
+
+func opsNullInt16(v *int16) any {
+	if v == nil {
+		return sql.NullInt64{}
+	}
+	return sql.NullInt64{Int64: int64(*v), Valid: true}
+}

backend/internal/server/routes/gateway.go

@@ -69,12 +69,30 @@ func RegisterGatewayRoutes(
 		})
 		gateway.GET("/models", h.Gateway.Models)
 		gateway.GET("/usage", h.Gateway.Usage)
-		// OpenAI Responses API
-		gateway.POST("/responses", h.OpenAIGateway.Responses)
-		gateway.POST("/responses/*subpath", h.OpenAIGateway.Responses)
+		// OpenAI Responses API: auto-route based on group platform
+		gateway.POST("/responses", func(c *gin.Context) {
+			if getGroupPlatform(c) == service.PlatformOpenAI {
+				h.OpenAIGateway.Responses(c)
+				return
+			}
+			h.Gateway.Responses(c)
+		})
+		gateway.POST("/responses/*subpath", func(c *gin.Context) {
+			if getGroupPlatform(c) == service.PlatformOpenAI {
+				h.OpenAIGateway.Responses(c)
+				return
+			}
+			h.Gateway.Responses(c)
+		})
 		gateway.GET("/responses", h.OpenAIGateway.ResponsesWebSocket)
-		// OpenAI Chat Completions API
-		gateway.POST("/chat/completions", h.OpenAIGateway.ChatCompletions)
+		// OpenAI Chat Completions API: auto-route based on group platform
+		gateway.POST("/chat/completions", func(c *gin.Context) {
+			if getGroupPlatform(c) == service.PlatformOpenAI {
+				h.OpenAIGateway.ChatCompletions(c)
+				return
+			}
+			h.Gateway.ChatCompletions(c)
+		})
 	}
 
 	// Gemini 原生 API 兼容层（Gemini SDK/CLI 直连）
@@ -92,12 +110,25 @@ func RegisterGatewayRoutes(
 		gemini.POST("/models/*modelAction", h.Gateway.GeminiV1BetaModels)
 	}
 
-	// OpenAI Responses API（不带v1前缀的别名）
-	r.POST("/responses", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.OpenAIGateway.Responses)
-	r.POST("/responses/*subpath", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.OpenAIGateway.Responses)
+	// OpenAI Responses API（不带v1前缀的别名）— auto-route based on group platform
+	responsesHandler := func(c *gin.Context) {
+		if getGroupPlatform(c) == service.PlatformOpenAI {
+			h.OpenAIGateway.Responses(c)
+			return
+		}
+		h.Gateway.Responses(c)
+	}
+	r.POST("/responses", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, responsesHandler)
+	r.POST("/responses/*subpath", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, responsesHandler)
 	r.GET("/responses", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.OpenAIGateway.ResponsesWebSocket)
-	// OpenAI Chat Completions API（不带v1前缀的别名）
-	r.POST("/chat/completions", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.OpenAIGateway.ChatCompletions)
+	// OpenAI Chat Completions API（不带v1前缀的别名）— auto-route based on group platform
+	r.POST("/chat/completions", bodyLimit, clientRequestID, opsErrorLogger, endpointNorm, gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, func(c *gin.Context) {
+		if getGroupPlatform(c) == service.PlatformOpenAI {
+			h.OpenAIGateway.ChatCompletions(c)
+			return
+		}
+		h.Gateway.ChatCompletions(c)
+	})
 
 	// Antigravity 模型列表
 	r.GET("/antigravity/models", gin.HandlerFunc(apiKeyAuth), requireGroupAnthropic, h.Gateway.AntigravityModels)

backend/internal/service/antigravity_gateway_service.go

@@ -643,6 +643,7 @@ urlFallbackLoop:
 					AccountID:          p.account.ID,
 					AccountName:        p.account.Name,
 					UpstreamStatusCode: 0,
+					UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 					Kind:               "request_error",
 					Message:            safeErr,
 				})
@@ -720,6 +721,7 @@ urlFallbackLoop:
 							AccountName:        p.account.Name,
 							UpstreamStatusCode: resp.StatusCode,
 							UpstreamRequestID:  resp.Header.Get("x-request-id"),
+							UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 							Kind:               "retry",
 							Message:            upstreamMsg,
 							Detail:             getUpstreamDetail(respBody),
@@ -754,6 +756,7 @@ urlFallbackLoop:
 							AccountName:        p.account.Name,
 							UpstreamStatusCode: resp.StatusCode,
 							UpstreamRequestID:  resp.Header.Get("x-request-id"),
+							UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 							Kind:               "retry",
 							Message:            upstreamMsg,
 							Detail:             getUpstreamDetail(respBody),

backend/internal/service/gateway_forward_as_chat_completions.go

+package service
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/Wei-Shaw/sub2api/internal/util/responseheaders"
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+	"go.uber.org/zap"
+)
+
+// ForwardAsChatCompletions accepts an OpenAI Chat Completions API request body,
+// converts it to Anthropic Messages format (chained via Responses format),
+// forwards to the Anthropic upstream, and converts the response back to Chat
+// Completions format. This enables Chat Completions clients to access Anthropic
+// models through Anthropic platform groups.
+func (s *GatewayService) ForwardAsChatCompletions(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	body []byte,
+	parsed *ParsedRequest,
+) (*ForwardResult, error) {
+	startTime := time.Now()
+
+	// 1. Parse Chat Completions request
+	var ccReq apicompat.ChatCompletionsRequest
+	if err := json.Unmarshal(body, &ccReq); err != nil {
+		return nil, fmt.Errorf("parse chat completions request: %w", err)
+	}
+	originalModel := ccReq.Model
+	clientStream := ccReq.Stream
+	includeUsage := ccReq.StreamOptions != nil && ccReq.StreamOptions.IncludeUsage
+
+	// 2. Convert CC → Responses → Anthropic (chained conversion)
+	responsesReq, err := apicompat.ChatCompletionsToResponses(&ccReq)
+	if err != nil {
+		return nil, fmt.Errorf("convert chat completions to responses: %w", err)
+	}
+
+	anthropicReq, err := apicompat.ResponsesToAnthropicRequest(responsesReq)
+	if err != nil {
+		return nil, fmt.Errorf("convert responses to anthropic: %w", err)
+	}
+
+	// 3. Force upstream streaming
+	anthropicReq.Stream = true
+	reqStream := true
+
+	// 4. Model mapping
+	mappedModel := originalModel
+	if account.Type == AccountTypeAPIKey {
+		mappedModel = account.GetMappedModel(originalModel)
+	}
+	if mappedModel == originalModel && account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
+		normalized := claude.NormalizeModelID(originalModel)
+		if normalized != originalModel {
+			mappedModel = normalized
+		}
+	}
+	anthropicReq.Model = mappedModel
+
+	logger.L().Debug("gateway forward_as_chat_completions: model mapping applied",
+		zap.Int64("account_id", account.ID),
+		zap.String("original_model", originalModel),
+		zap.String("mapped_model", mappedModel),
+		zap.Bool("client_stream", clientStream),
+	)
+
+	// 5. Marshal Anthropic request body
+	anthropicBody, err := json.Marshal(anthropicReq)
+	if err != nil {
+		return nil, fmt.Errorf("marshal anthropic request: %w", err)
+	}
+
+	// 6. Apply Claude Code mimicry for OAuth accounts
+	isClaudeCode := false // CC API is never Claude Code
+	shouldMimicClaudeCode := account.IsOAuth() && !isClaudeCode
+
+	if shouldMimicClaudeCode {
+		if !strings.Contains(strings.ToLower(mappedModel), "haiku") &&
+			!systemIncludesClaudeCodePrompt(anthropicReq.System) {
+			anthropicBody = injectClaudeCodePrompt(anthropicBody, anthropicReq.System)
+		}
+	}
+
+	// 7. Enforce cache_control block limit
+	anthropicBody = enforceCacheControlLimit(anthropicBody)
+
+	// 8. Get access token
+	token, tokenType, err := s.GetAccessToken(ctx, account)
+	if err != nil {
+		return nil, fmt.Errorf("get access token: %w", err)
+	}
+
+	// 9. Get proxy URL
+	proxyURL := ""
+	if account.ProxyID != nil && account.Proxy != nil {
+		proxyURL = account.Proxy.URL()
+	}
+
+	// 10. Build upstream request
+	upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, reqStream)
+	upstreamReq, err := s.buildUpstreamRequest(upstreamCtx, c, account, anthropicBody, token, tokenType, mappedModel, reqStream, shouldMimicClaudeCode)
+	releaseUpstreamCtx()
+	if err != nil {
+		return nil, fmt.Errorf("build upstream request: %w", err)
+	}
+
+	// 11. Send request
+	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,
+			Kind:               "request_error",
+			Message:            safeErr,
+		})
+		writeGatewayCCError(c, http.StatusBadGateway, "server_error", "Upstream request failed")
+		return nil, fmt.Errorf("upstream request failed: %s", safeErr)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	// 12. Handle error response with failover
+	if resp.StatusCode >= 400 {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+		_ = resp.Body.Close()
+		resp.Body = io.NopCloser(bytes.NewReader(respBody))
+
+		upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
+		upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
+
+		if s.shouldFailoverUpstreamError(resp.StatusCode) {
+			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+				Platform:           account.Platform,
+				AccountID:          account.ID,
+				AccountName:        account.Name,
+				UpstreamStatusCode: resp.StatusCode,
+				UpstreamRequestID:  resp.Header.Get("x-request-id"),
+				Kind:               "failover",
+				Message:            upstreamMsg,
+			})
+			if s.rateLimitService != nil {
+				s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)
+			}
+			return nil, &UpstreamFailoverError{
+				StatusCode:   resp.StatusCode,
+				ResponseBody: respBody,
+			}
+		}
+
+		writeGatewayCCError(c, mapUpstreamStatusCode(resp.StatusCode), "server_error", upstreamMsg)
+		return nil, fmt.Errorf("upstream error: %d %s", resp.StatusCode, upstreamMsg)
+	}
+
+	// 13. Extract reasoning effort from CC request body
+	reasoningEffort := extractCCReasoningEffortFromBody(body)
+
+	// 14. Handle normal response
+	// Read Anthropic SSE → convert to Responses events → convert to CC format
+	var result *ForwardResult
+	var handleErr error
+	if clientStream {
+		result, handleErr = s.handleCCStreamingFromAnthropic(resp, c, originalModel, mappedModel, reasoningEffort, startTime, includeUsage)
+	} else {
+		result, handleErr = s.handleCCBufferedFromAnthropic(resp, c, originalModel, mappedModel, reasoningEffort, startTime)
+	}
+
+	return result, handleErr
+}
+
+// extractCCReasoningEffortFromBody reads reasoning effort from a Chat Completions
+// request body. It checks both nested (reasoning.effort) and flat (reasoning_effort)
+// formats used by OpenAI-compatible clients.
+func extractCCReasoningEffortFromBody(body []byte) *string {
+	raw := strings.TrimSpace(gjson.GetBytes(body, "reasoning.effort").String())
+	if raw == "" {
+		raw = strings.TrimSpace(gjson.GetBytes(body, "reasoning_effort").String())
+	}
+	if raw == "" {
+		return nil
+	}
+	normalized := normalizeOpenAIReasoningEffort(raw)
+	if normalized == "" {
+		return nil
+	}
+	return &normalized
+}
+
+// handleCCBufferedFromAnthropic reads Anthropic SSE events, assembles the full
+// response, then converts Anthropic → Responses → Chat Completions.
+func (s *GatewayService) handleCCBufferedFromAnthropic(
+	resp *http.Response,
+	c *gin.Context,
+	originalModel string,
+	mappedModel string,
+	reasoningEffort *string,
+	startTime time.Time,
+) (*ForwardResult, error) {
+	requestID := resp.Header.Get("x-request-id")
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
+
+	var finalResp *apicompat.AnthropicResponse
+	var usage ClaudeUsage
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "event: ") {
+			continue
+		}
+
+		if !scanner.Scan() {
+			break
+		}
+		dataLine := scanner.Text()
+		if !strings.HasPrefix(dataLine, "data: ") {
+			continue
+		}
+		payload := dataLine[6:]
+
+		var event apicompat.AnthropicStreamEvent
+		if err := json.Unmarshal([]byte(payload), &event); err != nil {
+			continue
+		}
+
+		// message_start carries the initial response structure and cache usage
+		if event.Type == "message_start" && event.Message != nil {
+			finalResp = event.Message
+			mergeAnthropicUsage(&usage, event.Message.Usage)
+		}
+
+		// message_delta carries final usage and stop_reason
+		if event.Type == "message_delta" {
+			if event.Usage != nil {
+				mergeAnthropicUsage(&usage, *event.Usage)
+			}
+			if event.Delta != nil && event.Delta.StopReason != "" && finalResp != nil {
+				finalResp.StopReason = event.Delta.StopReason
+			}
+		}
+		if event.Type == "content_block_start" && event.ContentBlock != nil && finalResp != nil {
+			finalResp.Content = append(finalResp.Content, *event.ContentBlock)
+		}
+		if event.Type == "content_block_delta" && event.Delta != nil && finalResp != nil && event.Index != nil {
+			idx := *event.Index
+			if idx < len(finalResp.Content) {
+				switch event.Delta.Type {
+				case "text_delta":
+					finalResp.Content[idx].Text += event.Delta.Text
+				case "thinking_delta":
+					finalResp.Content[idx].Thinking += event.Delta.Thinking
+				case "input_json_delta":
+					finalResp.Content[idx].Input = appendRawJSON(finalResp.Content[idx].Input, event.Delta.PartialJSON)
+				}
+			}
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
+			logger.L().Warn("forward_as_cc buffered: read error",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+			)
+		}
+	}
+
+	if finalResp == nil {
+		writeGatewayCCError(c, http.StatusBadGateway, "server_error", "Upstream stream ended without a response")
+		return nil, fmt.Errorf("upstream stream ended without response")
+	}
+
+	// Update usage from accumulated delta
+	if usage.InputTokens > 0 || usage.OutputTokens > 0 {
+		finalResp.Usage = apicompat.AnthropicUsage{
+			InputTokens:              usage.InputTokens,
+			OutputTokens:             usage.OutputTokens,
+			CacheCreationInputTokens: usage.CacheCreationInputTokens,
+			CacheReadInputTokens:     usage.CacheReadInputTokens,
+		}
+	}
+
+	// Chain: Anthropic → Responses → Chat Completions
+	responsesResp := apicompat.AnthropicToResponsesResponse(finalResp)
+	ccResp := apicompat.ResponsesToChatCompletions(responsesResp, originalModel)
+
+	if s.responseHeaderFilter != nil {
+		responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.responseHeaderFilter)
+	}
+	c.JSON(http.StatusOK, ccResp)
+
+	return &ForwardResult{
+		RequestID:       requestID,
+		Usage:           usage,
+		Model:           originalModel,
+		UpstreamModel:   mappedModel,
+		ReasoningEffort: reasoningEffort,
+		Stream:          false,
+		Duration:        time.Since(startTime),
+	}, nil
+}
+
+// handleCCStreamingFromAnthropic reads Anthropic SSE events, converts each
+// to Responses events, then to Chat Completions chunks, and writes them.
+func (s *GatewayService) handleCCStreamingFromAnthropic(
+	resp *http.Response,
+	c *gin.Context,
+	originalModel string,
+	mappedModel string,
+	reasoningEffort *string,
+	startTime time.Time,
+	includeUsage bool,
+) (*ForwardResult, error) {
+	requestID := resp.Header.Get("x-request-id")
+
+	if s.responseHeaderFilter != nil {
+		responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.responseHeaderFilter)
+	}
+	c.Writer.Header().Set("Content-Type", "text/event-stream")
+	c.Writer.Header().Set("Cache-Control", "no-cache")
+	c.Writer.Header().Set("Connection", "keep-alive")
+	c.Writer.Header().Set("X-Accel-Buffering", "no")
+	c.Writer.WriteHeader(http.StatusOK)
+
+	// Use Anthropic→Responses state machine, then convert Responses→CC
+	anthState := apicompat.NewAnthropicEventToResponsesState()
+	anthState.Model = originalModel
+	ccState := apicompat.NewResponsesEventToChatState()
+	ccState.Model = originalModel
+	ccState.IncludeUsage = includeUsage
+
+	var usage ClaudeUsage
+	var firstTokenMs *int
+	firstChunk := true
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
+
+	resultWithUsage := func() *ForwardResult {
+		return &ForwardResult{
+			RequestID:       requestID,
+			Usage:           usage,
+			Model:           originalModel,
+			UpstreamModel:   mappedModel,
+			ReasoningEffort: reasoningEffort,
+			Stream:          true,
+			Duration:        time.Since(startTime),
+			FirstTokenMs:    firstTokenMs,
+		}
+	}
+
+	writeChunk := func(chunk apicompat.ChatCompletionsChunk) bool {
+		sse, err := apicompat.ChatChunkToSSE(chunk)
+		if err != nil {
+			return false
+		}
+		if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+			return true // client disconnected
+		}
+		return false
+	}
+
+	processAnthropicEvent := func(event *apicompat.AnthropicStreamEvent) bool {
+		if firstChunk {
+			firstChunk = false
+			ms := int(time.Since(startTime).Milliseconds())
+			firstTokenMs = &ms
+		}
+
+		// Extract usage from message_delta
+		if event.Type == "message_delta" && event.Usage != nil {
+			mergeAnthropicUsage(&usage, *event.Usage)
+		}
+		// Also capture usage from message_start (carries cache fields)
+		if event.Type == "message_start" && event.Message != nil {
+			mergeAnthropicUsage(&usage, event.Message.Usage)
+		}
+
+		// Chain: Anthropic event → Responses events → CC chunks
+		responsesEvents := apicompat.AnthropicEventToResponsesEvents(event, anthState)
+		for _, resEvt := range responsesEvents {
+			ccChunks := apicompat.ResponsesEventToChatChunks(&resEvt, ccState)
+			for _, chunk := range ccChunks {
+				if disconnected := writeChunk(chunk); disconnected {
+					return true
+				}
+			}
+		}
+		c.Writer.Flush()
+		return false
+	}
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "event: ") {
+			continue
+		}
+
+		if !scanner.Scan() {
+			break
+		}
+		dataLine := scanner.Text()
+		if !strings.HasPrefix(dataLine, "data: ") {
+			continue
+		}
+		payload := dataLine[6:]
+
+		var event apicompat.AnthropicStreamEvent
+		if err := json.Unmarshal([]byte(payload), &event); err != nil {
+			continue
+		}
+
+		if processAnthropicEvent(&event) {
+			return resultWithUsage(), nil
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
+			logger.L().Warn("forward_as_cc stream: read error",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+			)
+		}
+	}
+
+	// Finalize both state machines
+	finalResEvents := apicompat.FinalizeAnthropicResponsesStream(anthState)
+	for _, resEvt := range finalResEvents {
+		ccChunks := apicompat.ResponsesEventToChatChunks(&resEvt, ccState)
+		for _, chunk := range ccChunks {
+			writeChunk(chunk) //nolint:errcheck
+		}
+	}
+	finalCCChunks := apicompat.FinalizeResponsesChatStream(ccState)
+	for _, chunk := range finalCCChunks {
+		writeChunk(chunk) //nolint:errcheck
+	}
+
+	// Write [DONE] marker
+	fmt.Fprint(c.Writer, "data: [DONE]\n\n") //nolint:errcheck
+	c.Writer.Flush()
+
+	return resultWithUsage(), nil
+}
+
+// writeGatewayCCError writes an error in OpenAI Chat Completions format for
+// the Anthropic-upstream CC forwarding path.
+func writeGatewayCCError(c *gin.Context, statusCode int, errType, message string) {
+	c.JSON(statusCode, gin.H{
+		"error": gin.H{
+			"type":    errType,
+			"message": message,
+		},
+	})
+}

backend/internal/service/gateway_forward_as_chat_completions_test.go

+//go:build unit
+
+package service
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExtractCCReasoningEffortFromBody(t *testing.T) {
+	t.Parallel()
+
+	t.Run("nested reasoning.effort", func(t *testing.T) {
+		got := extractCCReasoningEffortFromBody([]byte(`{"reasoning":{"effort":"HIGH"}}`))
+		require.NotNil(t, got)
+		require.Equal(t, "high", *got)
+	})
+
+	t.Run("flat reasoning_effort", func(t *testing.T) {
+		got := extractCCReasoningEffortFromBody([]byte(`{"reasoning_effort":"x-high"}`))
+		require.NotNil(t, got)
+		require.Equal(t, "xhigh", *got)
+	})
+
+	t.Run("missing effort", func(t *testing.T) {
+		require.Nil(t, extractCCReasoningEffortFromBody([]byte(`{"model":"gpt-5"}`)))
+	})
+}
+
+func TestHandleCCBufferedFromAnthropic_PreservesMessageStartCacheUsageAndReasoning(t *testing.T) {
+	t.Parallel()
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	reasoningEffort := "high"
+	resp := &http.Response{
+		Header: http.Header{"x-request-id": []string{"rid_cc_buffered"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`event: message_start`,
+			`data: {"type":"message_start","message":{"id":"msg_1","type":"message","role":"assistant","content":[],"model":"claude-sonnet-4.5","stop_reason":"","usage":{"input_tokens":12,"cache_read_input_tokens":9,"cache_creation_input_tokens":3}}}`,
+			``,
+			`event: content_block_start`,
+			`data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":"hello"}}`,
+			``,
+			`event: message_delta`,
+			`data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":7}}`,
+			``,
+		}, "\n"))),
+	}
+
+	svc := &GatewayService{}
+	result, err := svc.handleCCBufferedFromAnthropic(resp, c, "gpt-5", "claude-sonnet-4.5", &reasoningEffort, time.Now())
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 12, result.Usage.InputTokens)
+	require.Equal(t, 7, result.Usage.OutputTokens)
+	require.Equal(t, 9, result.Usage.CacheReadInputTokens)
+	require.Equal(t, 3, result.Usage.CacheCreationInputTokens)
+	require.NotNil(t, result.ReasoningEffort)
+	require.Equal(t, "high", *result.ReasoningEffort)
+}
+
+func TestHandleCCStreamingFromAnthropic_PreservesMessageStartCacheUsageAndReasoning(t *testing.T) {
+	t.Parallel()
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	reasoningEffort := "medium"
+	resp := &http.Response{
+		Header: http.Header{"x-request-id": []string{"rid_cc_stream"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`event: message_start`,
+			`data: {"type":"message_start","message":{"id":"msg_2","type":"message","role":"assistant","content":[],"model":"claude-sonnet-4.5","stop_reason":"","usage":{"input_tokens":20,"cache_read_input_tokens":11,"cache_creation_input_tokens":4}}}`,
+			``,
+			`event: content_block_start`,
+			`data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":"hello"}}`,
+			``,
+			`event: message_delta`,
+			`data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":8}}`,
+			``,
+			`event: message_stop`,
+			`data: {"type":"message_stop"}`,
+			``,
+		}, "\n"))),
+	}
+
+	svc := &GatewayService{}
+	result, err := svc.handleCCStreamingFromAnthropic(resp, c, "gpt-5", "claude-sonnet-4.5", &reasoningEffort, time.Now(), true)
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 20, result.Usage.InputTokens)
+	require.Equal(t, 8, result.Usage.OutputTokens)
+	require.Equal(t, 11, result.Usage.CacheReadInputTokens)
+	require.Equal(t, 4, result.Usage.CacheCreationInputTokens)
+	require.NotNil(t, result.ReasoningEffort)
+	require.Equal(t, "medium", *result.ReasoningEffort)
+	require.Contains(t, rec.Body.String(), `[DONE]`)
+}

backend/internal/service/gateway_forward_as_responses.go

+package service
+
+import (
+	"bufio"
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/Wei-Shaw/sub2api/internal/pkg/apicompat"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/claude"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
+	"github.com/Wei-Shaw/sub2api/internal/util/responseheaders"
+	"github.com/gin-gonic/gin"
+	"github.com/tidwall/gjson"
+	"go.uber.org/zap"
+)
+
+// ForwardAsResponses accepts an OpenAI Responses API request body, converts it
+// to Anthropic Messages format, forwards to the Anthropic upstream, and converts
+// the response back to Responses format. This enables OpenAI Responses API
+// clients to access Anthropic models through Anthropic platform groups.
+//
+// The method follows the same pattern as OpenAIGatewayService.ForwardAsAnthropic
+// but in reverse direction: Responses → Anthropic upstream → Responses.
+func (s *GatewayService) ForwardAsResponses(
+	ctx context.Context,
+	c *gin.Context,
+	account *Account,
+	body []byte,
+	parsed *ParsedRequest,
+) (*ForwardResult, error) {
+	startTime := time.Now()
+
+	// 1. Parse Responses request
+	var responsesReq apicompat.ResponsesRequest
+	if err := json.Unmarshal(body, &responsesReq); err != nil {
+		return nil, fmt.Errorf("parse responses request: %w", err)
+	}
+	originalModel := responsesReq.Model
+	clientStream := responsesReq.Stream
+
+	// 2. Convert Responses → Anthropic
+	anthropicReq, err := apicompat.ResponsesToAnthropicRequest(&responsesReq)
+	if err != nil {
+		return nil, fmt.Errorf("convert responses to anthropic: %w", err)
+	}
+
+	// 3. Force upstream streaming (Anthropic works best with streaming)
+	anthropicReq.Stream = true
+	reqStream := true
+
+	// 4. Model mapping
+	mappedModel := originalModel
+	reasoningEffort := ExtractResponsesReasoningEffortFromBody(body)
+	if account.Type == AccountTypeAPIKey {
+		mappedModel = account.GetMappedModel(originalModel)
+	}
+	if mappedModel == originalModel && account.Platform == PlatformAnthropic && account.Type != AccountTypeAPIKey {
+		normalized := claude.NormalizeModelID(originalModel)
+		if normalized != originalModel {
+			mappedModel = normalized
+		}
+	}
+	anthropicReq.Model = mappedModel
+
+	logger.L().Debug("gateway forward_as_responses: model mapping applied",
+		zap.Int64("account_id", account.ID),
+		zap.String("original_model", originalModel),
+		zap.String("mapped_model", mappedModel),
+		zap.Bool("client_stream", clientStream),
+	)
+
+	// 5. Marshal Anthropic request body
+	anthropicBody, err := json.Marshal(anthropicReq)
+	if err != nil {
+		return nil, fmt.Errorf("marshal anthropic request: %w", err)
+	}
+
+	// 6. Apply Claude Code mimicry for OAuth accounts (non-Claude-Code endpoints)
+	isClaudeCode := false // Responses API is never Claude Code
+	shouldMimicClaudeCode := account.IsOAuth() && !isClaudeCode
+
+	if shouldMimicClaudeCode {
+		if !strings.Contains(strings.ToLower(mappedModel), "haiku") &&
+			!systemIncludesClaudeCodePrompt(anthropicReq.System) {
+			anthropicBody = injectClaudeCodePrompt(anthropicBody, anthropicReq.System)
+		}
+	}
+
+	// 7. Enforce cache_control block limit
+	anthropicBody = enforceCacheControlLimit(anthropicBody)
+
+	// 8. Get access token
+	token, tokenType, err := s.GetAccessToken(ctx, account)
+	if err != nil {
+		return nil, fmt.Errorf("get access token: %w", err)
+	}
+
+	// 9. Get proxy URL
+	proxyURL := ""
+	if account.ProxyID != nil && account.Proxy != nil {
+		proxyURL = account.Proxy.URL()
+	}
+
+	// 10. Build upstream request
+	upstreamCtx, releaseUpstreamCtx := detachStreamUpstreamContext(ctx, reqStream)
+	upstreamReq, err := s.buildUpstreamRequest(upstreamCtx, c, account, anthropicBody, token, tokenType, mappedModel, reqStream, shouldMimicClaudeCode)
+	releaseUpstreamCtx()
+	if err != nil {
+		return nil, fmt.Errorf("build upstream request: %w", err)
+	}
+
+	// 11. Send request
+	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,
+			Kind:               "request_error",
+			Message:            safeErr,
+		})
+		writeResponsesError(c, http.StatusBadGateway, "server_error", "Upstream request failed")
+		return nil, fmt.Errorf("upstream request failed: %s", safeErr)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	// 12. Handle error response with failover
+	if resp.StatusCode >= 400 {
+		respBody, _ := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
+		_ = resp.Body.Close()
+		resp.Body = io.NopCloser(bytes.NewReader(respBody))
+
+		upstreamMsg := strings.TrimSpace(extractUpstreamErrorMessage(respBody))
+		upstreamMsg = sanitizeUpstreamErrorMessage(upstreamMsg)
+
+		if s.shouldFailoverUpstreamError(resp.StatusCode) {
+			appendOpsUpstreamError(c, OpsUpstreamErrorEvent{
+				Platform:           account.Platform,
+				AccountID:          account.ID,
+				AccountName:        account.Name,
+				UpstreamStatusCode: resp.StatusCode,
+				UpstreamRequestID:  resp.Header.Get("x-request-id"),
+				Kind:               "failover",
+				Message:            upstreamMsg,
+			})
+			if s.rateLimitService != nil {
+				s.rateLimitService.HandleUpstreamError(ctx, account, resp.StatusCode, resp.Header, respBody)
+			}
+			return nil, &UpstreamFailoverError{
+				StatusCode:   resp.StatusCode,
+				ResponseBody: respBody,
+			}
+		}
+
+		// Non-failover error: return Responses-formatted error to client
+		writeResponsesError(c, mapUpstreamStatusCode(resp.StatusCode), "server_error", upstreamMsg)
+		return nil, fmt.Errorf("upstream error: %d %s", resp.StatusCode, upstreamMsg)
+	}
+
+	// 13. Handle normal response (convert Anthropic → Responses)
+	var result *ForwardResult
+	var handleErr error
+	if clientStream {
+		result, handleErr = s.handleResponsesStreamingResponse(resp, c, originalModel, mappedModel, reasoningEffort, startTime)
+	} else {
+		result, handleErr = s.handleResponsesBufferedStreamingResponse(resp, c, originalModel, mappedModel, reasoningEffort, startTime)
+	}
+
+	return result, handleErr
+}
+
+// ExtractResponsesReasoningEffortFromBody reads Responses API reasoning.effort
+// and normalizes it for usage logging.
+func ExtractResponsesReasoningEffortFromBody(body []byte) *string {
+	raw := strings.TrimSpace(gjson.GetBytes(body, "reasoning.effort").String())
+	if raw == "" {
+		return nil
+	}
+	normalized := normalizeOpenAIReasoningEffort(raw)
+	if normalized == "" {
+		return nil
+	}
+	return &normalized
+}
+
+func mergeAnthropicUsage(dst *ClaudeUsage, src apicompat.AnthropicUsage) {
+	if dst == nil {
+		return
+	}
+	if src.InputTokens > 0 {
+		dst.InputTokens = src.InputTokens
+	}
+	if src.OutputTokens > 0 {
+		dst.OutputTokens = src.OutputTokens
+	}
+	if src.CacheReadInputTokens > 0 {
+		dst.CacheReadInputTokens = src.CacheReadInputTokens
+	}
+	if src.CacheCreationInputTokens > 0 {
+		dst.CacheCreationInputTokens = src.CacheCreationInputTokens
+	}
+}
+
+// handleResponsesBufferedStreamingResponse reads all Anthropic SSE events from
+// the upstream streaming response, assembles them into a complete Anthropic
+// response, converts to Responses API JSON format, and writes it to the client.
+func (s *GatewayService) handleResponsesBufferedStreamingResponse(
+	resp *http.Response,
+	c *gin.Context,
+	originalModel string,
+	mappedModel string,
+	reasoningEffort *string,
+	startTime time.Time,
+) (*ForwardResult, error) {
+	requestID := resp.Header.Get("x-request-id")
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
+
+	// Accumulate the final Anthropic response from streaming events
+	var finalResp *apicompat.AnthropicResponse
+	var usage ClaudeUsage
+
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "event: ") {
+			continue
+		}
+		eventType := strings.TrimPrefix(line, "event: ")
+
+		// Read the data line
+		if !scanner.Scan() {
+			break
+		}
+		dataLine := scanner.Text()
+		if !strings.HasPrefix(dataLine, "data: ") {
+			continue
+		}
+		payload := dataLine[6:]
+
+		var event apicompat.AnthropicStreamEvent
+		if err := json.Unmarshal([]byte(payload), &event); err != nil {
+			logger.L().Warn("forward_as_responses buffered: failed to parse event",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+				zap.String("event_type", eventType),
+			)
+			continue
+		}
+
+		// message_start carries the initial response structure
+		if event.Type == "message_start" && event.Message != nil {
+			finalResp = event.Message
+			mergeAnthropicUsage(&usage, event.Message.Usage)
+		}
+
+		// message_delta carries final usage and stop_reason
+		if event.Type == "message_delta" {
+			if event.Usage != nil {
+				mergeAnthropicUsage(&usage, *event.Usage)
+			}
+			if event.Delta != nil && event.Delta.StopReason != "" && finalResp != nil {
+				finalResp.StopReason = event.Delta.StopReason
+			}
+		}
+
+		// Accumulate content blocks
+		if event.Type == "content_block_start" && event.ContentBlock != nil && finalResp != nil {
+			finalResp.Content = append(finalResp.Content, *event.ContentBlock)
+		}
+		if event.Type == "content_block_delta" && event.Delta != nil && finalResp != nil && event.Index != nil {
+			idx := *event.Index
+			if idx < len(finalResp.Content) {
+				switch event.Delta.Type {
+				case "text_delta":
+					finalResp.Content[idx].Text += event.Delta.Text
+				case "thinking_delta":
+					finalResp.Content[idx].Thinking += event.Delta.Thinking
+				case "input_json_delta":
+					finalResp.Content[idx].Input = appendRawJSON(finalResp.Content[idx].Input, event.Delta.PartialJSON)
+				}
+			}
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
+			logger.L().Warn("forward_as_responses buffered: read error",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+			)
+		}
+	}
+
+	if finalResp == nil {
+		writeResponsesError(c, http.StatusBadGateway, "server_error", "Upstream stream ended without a response")
+		return nil, fmt.Errorf("upstream stream ended without response")
+	}
+
+	// Update usage from accumulated delta
+	if usage.InputTokens > 0 || usage.OutputTokens > 0 {
+		finalResp.Usage = apicompat.AnthropicUsage{
+			InputTokens:              usage.InputTokens,
+			OutputTokens:             usage.OutputTokens,
+			CacheCreationInputTokens: usage.CacheCreationInputTokens,
+			CacheReadInputTokens:     usage.CacheReadInputTokens,
+		}
+	}
+
+	// Convert to Responses format
+	responsesResp := apicompat.AnthropicToResponsesResponse(finalResp)
+	responsesResp.Model = originalModel // Use original model name
+
+	if s.responseHeaderFilter != nil {
+		responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.responseHeaderFilter)
+	}
+	c.JSON(http.StatusOK, responsesResp)
+
+	return &ForwardResult{
+		RequestID:       requestID,
+		Usage:           usage,
+		Model:           originalModel,
+		UpstreamModel:   mappedModel,
+		ReasoningEffort: reasoningEffort,
+		Stream:          false,
+		Duration:        time.Since(startTime),
+	}, nil
+}
+
+// handleResponsesStreamingResponse reads Anthropic SSE events from upstream,
+// converts each to Responses SSE events, and writes them to the client.
+func (s *GatewayService) handleResponsesStreamingResponse(
+	resp *http.Response,
+	c *gin.Context,
+	originalModel string,
+	mappedModel string,
+	reasoningEffort *string,
+	startTime time.Time,
+) (*ForwardResult, error) {
+	requestID := resp.Header.Get("x-request-id")
+
+	if s.responseHeaderFilter != nil {
+		responseheaders.WriteFilteredHeaders(c.Writer.Header(), resp.Header, s.responseHeaderFilter)
+	}
+	c.Writer.Header().Set("Content-Type", "text/event-stream")
+	c.Writer.Header().Set("Cache-Control", "no-cache")
+	c.Writer.Header().Set("Connection", "keep-alive")
+	c.Writer.Header().Set("X-Accel-Buffering", "no")
+	c.Writer.WriteHeader(http.StatusOK)
+
+	state := apicompat.NewAnthropicEventToResponsesState()
+	state.Model = originalModel
+	var usage ClaudeUsage
+	var firstTokenMs *int
+	firstChunk := true
+
+	scanner := bufio.NewScanner(resp.Body)
+	maxLineSize := defaultMaxLineSize
+	if s.cfg != nil && s.cfg.Gateway.MaxLineSize > 0 {
+		maxLineSize = s.cfg.Gateway.MaxLineSize
+	}
+	scanner.Buffer(make([]byte, 0, 64*1024), maxLineSize)
+
+	resultWithUsage := func() *ForwardResult {
+		return &ForwardResult{
+			RequestID:       requestID,
+			Usage:           usage,
+			Model:           originalModel,
+			UpstreamModel:   mappedModel,
+			ReasoningEffort: reasoningEffort,
+			Stream:          true,
+			Duration:        time.Since(startTime),
+			FirstTokenMs:    firstTokenMs,
+		}
+	}
+
+	// processEvent handles a single parsed Anthropic SSE event.
+	processEvent := func(event *apicompat.AnthropicStreamEvent) bool {
+		if firstChunk {
+			firstChunk = false
+			ms := int(time.Since(startTime).Milliseconds())
+			firstTokenMs = &ms
+		}
+
+		// Extract usage from message_delta
+		if event.Type == "message_delta" && event.Usage != nil {
+			mergeAnthropicUsage(&usage, *event.Usage)
+		}
+		// Also capture usage from message_start
+		if event.Type == "message_start" && event.Message != nil {
+			mergeAnthropicUsage(&usage, event.Message.Usage)
+		}
+
+		// Convert to Responses events
+		events := apicompat.AnthropicEventToResponsesEvents(event, state)
+		for _, evt := range events {
+			sse, err := apicompat.ResponsesEventToSSE(evt)
+			if err != nil {
+				logger.L().Warn("forward_as_responses stream: failed to marshal event",
+					zap.Error(err),
+					zap.String("request_id", requestID),
+				)
+				continue
+			}
+			if _, err := fmt.Fprint(c.Writer, sse); err != nil {
+				logger.L().Info("forward_as_responses stream: client disconnected",
+					zap.String("request_id", requestID),
+				)
+				return true // client disconnected
+			}
+		}
+		if len(events) > 0 {
+			c.Writer.Flush()
+		}
+		return false
+	}
+
+	finalizeStream := func() (*ForwardResult, error) {
+		if finalEvents := apicompat.FinalizeAnthropicResponsesStream(state); len(finalEvents) > 0 {
+			for _, evt := range finalEvents {
+				sse, err := apicompat.ResponsesEventToSSE(evt)
+				if err != nil {
+					continue
+				}
+				fmt.Fprint(c.Writer, sse) //nolint:errcheck
+			}
+			c.Writer.Flush()
+		}
+		return resultWithUsage(), nil
+	}
+
+	// Read Anthropic SSE events
+	for scanner.Scan() {
+		line := scanner.Text()
+		if !strings.HasPrefix(line, "event: ") {
+			continue
+		}
+		eventType := strings.TrimPrefix(line, "event: ")
+
+		// Read data line
+		if !scanner.Scan() {
+			break
+		}
+		dataLine := scanner.Text()
+		if !strings.HasPrefix(dataLine, "data: ") {
+			continue
+		}
+		payload := dataLine[6:]
+
+		var event apicompat.AnthropicStreamEvent
+		if err := json.Unmarshal([]byte(payload), &event); err != nil {
+			logger.L().Warn("forward_as_responses stream: failed to parse event",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+				zap.String("event_type", eventType),
+			)
+			continue
+		}
+
+		if processEvent(&event) {
+			return resultWithUsage(), nil
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		if !errors.Is(err, context.Canceled) && !errors.Is(err, context.DeadlineExceeded) {
+			logger.L().Warn("forward_as_responses stream: read error",
+				zap.Error(err),
+				zap.String("request_id", requestID),
+			)
+		}
+	}
+
+	return finalizeStream()
+}
+
+// appendRawJSON appends a JSON fragment string to existing raw JSON.
+func appendRawJSON(existing json.RawMessage, fragment string) json.RawMessage {
+	if len(existing) == 0 {
+		return json.RawMessage(fragment)
+	}
+	return json.RawMessage(string(existing) + fragment)
+}
+
+// writeResponsesError writes an error response in OpenAI Responses API format.
+func writeResponsesError(c *gin.Context, statusCode int, code, message string) {
+	c.JSON(statusCode, gin.H{
+		"error": gin.H{
+			"code":    code,
+			"message": message,
+		},
+	})
+}
+
+// mapUpstreamStatusCode maps upstream HTTP status codes to appropriate client-facing codes.
+func mapUpstreamStatusCode(code int) int {
+	if code >= 500 {
+		return http.StatusBadGateway
+	}
+	return code
+}

backend/internal/service/gateway_forward_as_responses_test.go

+//go:build unit
+
+package service
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExtractResponsesReasoningEffortFromBody(t *testing.T) {
+	t.Parallel()
+
+	got := ExtractResponsesReasoningEffortFromBody([]byte(`{"model":"claude-sonnet-4.5","reasoning":{"effort":"HIGH"}}`))
+	require.NotNil(t, got)
+	require.Equal(t, "high", *got)
+
+	require.Nil(t, ExtractResponsesReasoningEffortFromBody([]byte(`{"model":"claude-sonnet-4.5"}`)))
+}
+
+func TestHandleResponsesBufferedStreamingResponse_PreservesMessageStartCacheUsage(t *testing.T) {
+	t.Parallel()
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	resp := &http.Response{
+		Header: http.Header{"x-request-id": []string{"rid_buffered"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`event: message_start`,
+			`data: {"type":"message_start","message":{"id":"msg_1","type":"message","role":"assistant","content":[],"model":"claude-sonnet-4.5","stop_reason":"","usage":{"input_tokens":12,"cache_read_input_tokens":9,"cache_creation_input_tokens":3}}}`,
+			``,
+			`event: content_block_start`,
+			`data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":"hello"}}`,
+			``,
+			`event: message_delta`,
+			`data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":7}}`,
+			``,
+		}, "\n"))),
+	}
+
+	svc := &GatewayService{}
+	result, err := svc.handleResponsesBufferedStreamingResponse(resp, c, "claude-sonnet-4.5", "claude-sonnet-4.5", nil, time.Now())
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 12, result.Usage.InputTokens)
+	require.Equal(t, 7, result.Usage.OutputTokens)
+	require.Equal(t, 9, result.Usage.CacheReadInputTokens)
+	require.Equal(t, 3, result.Usage.CacheCreationInputTokens)
+	require.Contains(t, rec.Body.String(), `"cached_tokens":9`)
+}
+
+func TestHandleResponsesStreamingResponse_PreservesMessageStartCacheUsage(t *testing.T) {
+	t.Parallel()
+	gin.SetMode(gin.TestMode)
+
+	rec := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(rec)
+
+	resp := &http.Response{
+		Header: http.Header{"x-request-id": []string{"rid_stream"}},
+		Body: io.NopCloser(strings.NewReader(strings.Join([]string{
+			`event: message_start`,
+			`data: {"type":"message_start","message":{"id":"msg_2","type":"message","role":"assistant","content":[],"model":"claude-sonnet-4.5","stop_reason":"","usage":{"input_tokens":20,"cache_read_input_tokens":11,"cache_creation_input_tokens":4}}}`,
+			``,
+			`event: content_block_start`,
+			`data: {"type":"content_block_start","index":0,"content_block":{"type":"text","text":"hello"}}`,
+			``,
+			`event: message_delta`,
+			`data: {"type":"message_delta","delta":{"stop_reason":"end_turn"},"usage":{"output_tokens":8}}`,
+			``,
+			`event: message_stop`,
+			`data: {"type":"message_stop"}`,
+			``,
+		}, "\n"))),
+	}
+
+	svc := &GatewayService{}
+	result, err := svc.handleResponsesStreamingResponse(resp, c, "claude-sonnet-4.5", "claude-sonnet-4.5", nil, time.Now())
+	require.NoError(t, err)
+	require.NotNil(t, result)
+	require.Equal(t, 20, result.Usage.InputTokens)
+	require.Equal(t, 8, result.Usage.OutputTokens)
+	require.Equal(t, 11, result.Usage.CacheReadInputTokens)
+	require.Equal(t, 4, result.Usage.CacheCreationInputTokens)
+	require.Contains(t, rec.Body.String(), `response.completed`)
+}

backend/internal/service/gateway_request.go

@@ -5,6 +5,8 @@ import (
 	"encoding/json"
 	"fmt"
 	"math"
+	"regexp"
+	"sort"
 	"strings"
 	"unsafe"
 
@@ -34,6 +36,9 @@ var (
 	patternEmptyTextSpaced = []byte(`"text": ""`)
 	patternEmptyTextSp1    = []byte(`"text" : ""`)
 	patternEmptyTextSp2    = []byte(`"text" :""`)
+
+	sessionUserAgentProductPattern = regexp.MustCompile(`([A-Za-z0-9._-]+)/[A-Za-z0-9._-]+`)
+	sessionUserAgentVersionPattern = regexp.MustCompile(`\bv?\d+(?:\.\d+){1,3}\b`)
 )
 
 // SessionContext 粘性会话上下文，用于区分不同来源的请求。
@@ -75,6 +80,49 @@ type ParsedRequest struct {
 	OnUpstreamAccepted func()
 }
 
+// NormalizeSessionUserAgent reduces UA noise for sticky-session and digest hashing.
+// It preserves the set of product names from Product/Version tokens while
+// discarding version-only changes and incidental comments.
+func NormalizeSessionUserAgent(raw string) string {
+	raw = strings.TrimSpace(raw)
+	if raw == "" {
+		return ""
+	}
+
+	matches := sessionUserAgentProductPattern.FindAllStringSubmatch(raw, -1)
+	if len(matches) == 0 {
+		return normalizeSessionUserAgentFallback(raw)
+	}
+
+	products := make([]string, 0, len(matches))
+	seen := make(map[string]struct{}, len(matches))
+	for _, match := range matches {
+		if len(match) < 2 {
+			continue
+		}
+		product := strings.ToLower(strings.TrimSpace(match[1]))
+		if product == "" {
+			continue
+		}
+		if _, exists := seen[product]; exists {
+			continue
+		}
+		seen[product] = struct{}{}
+		products = append(products, product)
+	}
+	if len(products) == 0 {
+		return normalizeSessionUserAgentFallback(raw)
+	}
+	sort.Strings(products)
+	return strings.Join(products, "+")
+}
+
+func normalizeSessionUserAgentFallback(raw string) string {
+	normalized := strings.ToLower(strings.Join(strings.Fields(raw), " "))
+	normalized = sessionUserAgentVersionPattern.ReplaceAllString(normalized, "")
+	return strings.Join(strings.Fields(normalized), " ")
+}
+
 // ParseGatewayRequest 解析网关请求体并返回结构化结果。
 // protocol 指定请求协议格式（domain.PlatformAnthropic / domain.PlatformGemini），
 // 不同协议使用不同的 system/messages 字段名。

backend/internal/service/gateway_service.go

@@ -658,7 +658,7 @@ func (s *GatewayService) GenerateSessionHash(parsed *ParsedRequest) string {
 	if parsed.SessionContext != nil {
 		_, _ = combined.WriteString(parsed.SessionContext.ClientIP)
 		_, _ = combined.WriteString(":")
-		_, _ = combined.WriteString(parsed.SessionContext.UserAgent)
+		_, _ = combined.WriteString(NormalizeSessionUserAgent(parsed.SessionContext.UserAgent))
 		_, _ = combined.WriteString(":")
 		_, _ = combined.WriteString(strconv.FormatInt(parsed.SessionContext.APIKeyID, 10))
 		_, _ = combined.WriteString("|")
@@ -4148,6 +4148,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 				AccountID:          account.ID,
 				AccountName:        account.Name,
 				UpstreamStatusCode: 0,
+				UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 				Kind:               "request_error",
 				Message:            safeErr,
 			})
@@ -4174,6 +4175,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 						AccountName:        account.Name,
 						UpstreamStatusCode: resp.StatusCode,
 						UpstreamRequestID:  resp.Header.Get("x-request-id"),
+						UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 						Kind:               "signature_error",
 						Message:            extractUpstreamErrorMessage(respBody),
 						Detail: func() string {
@@ -4228,6 +4230,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 									AccountName:        account.Name,
 									UpstreamStatusCode: retryResp.StatusCode,
 									UpstreamRequestID:  retryResp.Header.Get("x-request-id"),
+									UpstreamURL:        safeUpstreamURL(retryReq.URL.String()),
 									Kind:               "signature_retry_thinking",
 									Message:            extractUpstreamErrorMessage(retryRespBody),
 									Detail: func() string {
@@ -4258,6 +4261,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 											AccountID:          account.ID,
 											AccountName:        account.Name,
 											UpstreamStatusCode: 0,
+											UpstreamURL:        safeUpstreamURL(retryReq2.URL.String()),
 											Kind:               "signature_retry_tools_request_error",
 											Message:            sanitizeUpstreamErrorMessage(retryErr2.Error()),
 										})
@@ -4297,6 +4301,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 						AccountName:        account.Name,
 						UpstreamStatusCode: resp.StatusCode,
 						UpstreamRequestID:  resp.Header.Get("x-request-id"),
+						UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 						Kind:               "budget_constraint_error",
 						Message:            errMsg,
 						Detail: func() string {
@@ -4358,6 +4363,7 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 					AccountName:        account.Name,
 					UpstreamStatusCode: resp.StatusCode,
 					UpstreamRequestID:  resp.Header.Get("x-request-id"),
+					UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 					Kind:               "retry",
 					Message:            extractUpstreamErrorMessage(respBody),
 					Detail: func() string {
@@ -4628,6 +4634,7 @@ func (s *GatewayService) forwardAnthropicAPIKeyPassthroughWithInput(
 				AccountID:          account.ID,
 				AccountName:        account.Name,
 				UpstreamStatusCode: 0,
+				UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 				Passthrough:        true,
 				Kind:               "request_error",
 				Message:            safeErr,
@@ -4667,6 +4674,7 @@ func (s *GatewayService) forwardAnthropicAPIKeyPassthroughWithInput(
 					AccountName:        account.Name,
 					UpstreamStatusCode: resp.StatusCode,
 					UpstreamRequestID:  resp.Header.Get("x-request-id"),
+					UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 					Passthrough:        true,
 					Kind:               "retry",
 					Message:            extractUpstreamErrorMessage(respBody),
@@ -5344,6 +5352,7 @@ func (s *GatewayService) executeBedrockUpstream(
 				AccountID:          account.ID,
 				AccountName:        account.Name,
 				UpstreamStatusCode: 0,
+				UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 				Kind:               "request_error",
 				Message:            safeErr,
 			})
@@ -5380,6 +5389,7 @@ func (s *GatewayService) executeBedrockUpstream(
 					AccountID:          account.ID,
 					AccountName:        account.Name,
 					UpstreamStatusCode: resp.StatusCode,
+					UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 					Kind:               "retry",
 					Message:            extractUpstreamErrorMessage(respBody),
 					Detail: func() string {
@@ -8064,6 +8074,7 @@ func (s *GatewayService) forwardCountTokensAnthropicAPIKeyPassthrough(ctx contex
 			AccountID:          account.ID,
 			AccountName:        account.Name,
 			UpstreamStatusCode: 0,
+			UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 			Passthrough:        true,
 			Kind:               "request_error",
 			Message:            sanitizeUpstreamErrorMessage(err.Error()),
@@ -8119,6 +8130,7 @@ func (s *GatewayService) forwardCountTokensAnthropicAPIKeyPassthrough(ctx contex
 			AccountName:        account.Name,
 			UpstreamStatusCode: resp.StatusCode,
 			UpstreamRequestID:  resp.Header.Get("x-request-id"),
+			UpstreamURL:        safeUpstreamURL(upstreamReq.URL.String()),
 			Passthrough:        true,
 			Kind:               "http_error",
 			Message:            upstreamMsg,