Merge pull request #809 from alfadb/feature/openai-messages

feat(openai): 添加 /v1/messages 端点和 API 兼容层

backend/internal/service/openai_gateway_service.go

@@ -900,6 +900,22 @@ func isOpenAIInstructionsRequiredError(upstreamStatusCode int, upstreamMsg strin
 	return false
 }
 
+// ExtractSessionID extracts the raw session ID from headers or body without hashing.
+// Used by ForwardAsAnthropic to pass as prompt_cache_key for upstream cache.
+func (s *OpenAIGatewayService) ExtractSessionID(c *gin.Context, body []byte) string {
+	if c == nil {
+		return ""
+	}
+	sessionID := strings.TrimSpace(c.GetHeader("session_id"))
+	if sessionID == "" {
+		sessionID = strings.TrimSpace(c.GetHeader("conversation_id"))
+	}
+	if sessionID == "" && len(body) > 0 {
+		sessionID = strings.TrimSpace(gjson.GetBytes(body, "prompt_cache_key").String())
+	}
+	return sessionID
+}
+
 // GenerateSessionHash generates a sticky-session hash for OpenAI requests.
 //
 // Priority: