fix: 修复gpt->claude转换无法命中codex缓存问题

backend/internal/handler/openai_gateway_handler.go

@@ -560,6 +560,21 @@ func (h *OpenAIGatewayHandler) Messages(c *gin.Context) {
 	sessionHash := h.gatewayService.GenerateSessionHash(c, body)
 	promptCacheKey := h.gatewayService.ExtractSessionID(c, body)
 
+	// Anthropic 格式的请求在 metadata.user_id 中携带 session 标识，
+	// 而非 OpenAI 的 session_id/conversation_id headers。
+	// 从中派生 sessionHash（sticky session）和 promptCacheKey（upstream cache）。
+	if sessionHash == "" || promptCacheKey == "" {
+		if userID := strings.TrimSpace(gjson.GetBytes(body, "metadata.user_id").String()); userID != "" {
+			seed := reqModel + "-" + userID
+			if promptCacheKey == "" {
+				promptCacheKey = service.GenerateSessionUUID(seed)
+			}
+			if sessionHash == "" {
+				sessionHash = service.DeriveSessionHashFromSeed(seed)
+			}
+		}
+	}
+
 	maxAccountSwitches := h.maxAccountSwitches
 	switchCount := 0
 	failedAccountIDs := make(map[int64]struct{})

backend/internal/service/gateway_service.go

@@ -997,6 +997,11 @@ func (s *GatewayService) buildOAuthMetadataUserID(parsed *ParsedRequest, account
 	return fmt.Sprintf("user_%s_account__session_%s", userID, sessionID)
 }
 
+// GenerateSessionUUID creates a deterministic UUID4 from a seed string.
+func GenerateSessionUUID(seed string) string {
+	return generateSessionUUID(seed)
+}
+
 func generateSessionUUID(seed string) string {
 	if seed == "" {
 		return uuid.NewString()

backend/internal/service/openai_gateway_messages.go

@@ -78,7 +78,12 @@ func (s *OpenAIGatewayService) ForwardAsAnthropic(
 		if err := json.Unmarshal(responsesBody, &reqBody); err != nil {
 			return nil, fmt.Errorf("unmarshal for codex transform: %w", err)
 		}
-		applyCodexOAuthTransform(reqBody, false, false)
+		codexResult := applyCodexOAuthTransform(reqBody, false, false)
+		if codexResult.PromptCacheKey != "" {
+			promptCacheKey = codexResult.PromptCacheKey
+		} else if promptCacheKey != "" {
+			reqBody["prompt_cache_key"] = promptCacheKey
+		}
 		// OAuth codex transform forces stream=true upstream, so always use
 		// the streaming response handler regardless of what the client asked.
 		isStream = true

backend/internal/service/openai_gateway_service.go

@@ -3646,6 +3646,13 @@ type OpenAIRecordUsageInput struct {
 // RecordUsage records usage and deducts balance
 func (s *OpenAIGatewayService) RecordUsage(ctx context.Context, input *OpenAIRecordUsageInput) error {
 	result := input.Result
+
+	// 跳过所有 token 均为零的用量记录——上游未返回 usage 时不应写入数据库
+	if result.Usage.InputTokens == 0 && result.Usage.OutputTokens == 0 &&
+		result.Usage.CacheCreationInputTokens == 0 && result.Usage.CacheReadInputTokens == 0 {
+		return nil
+	}
+
 	apiKey := input.APIKey
 	user := input.User
 	account := input.Account

backend/internal/service/openai_sticky_compat.go

@@ -29,6 +29,13 @@ func openAIStickyCompatStats() (legacyReadFallbackTotal, legacyReadFallbackHit,
 		openAIStickyLegacyDualWriteTotal.Load()
 }
 
+// DeriveSessionHashFromSeed computes the current-format sticky-session hash
+// from an arbitrary seed string.
+func DeriveSessionHashFromSeed(seed string) string {
+	currentHash, _ := deriveOpenAISessionHashes(seed)
+	return currentHash
+}
+
 func deriveOpenAISessionHashes(sessionID string) (currentHash string, legacyHash string) {
 	normalized := strings.TrimSpace(sessionID)
 	if normalized == "" {