sequenceDiagram
    participant OC as OpenClaw
    participant GW as API Gateway
    participant LB as 负载均衡器
    participant QM as 队列管理器
    participant RL as Rate Limiter
    participant P as Provider
    participant CD as Cooldown Detector
    participant ST as 统计引擎

    OC->>GW: POST /v1/chat/completions
    GW->>LB: 路由到目标池

    Note over LB: Weighted RR 5-10s刷新<br/>weight=(max_rpm-current_rpm)/max_rpm

    LB->>RL: BEGIN IMMEDIATE 事务 检查 RPM + 预占

    alt RPM 不足
        RL->>QM: 入队等待 超时30s
        QM-->>RL: 令牌可用
    end

    RL-->>LB: 允许转发

    LB->>P: 转发请求
    P-->>LB: 响应

    alt 200 OK
        LB->>ST: INSERT ON CONFLICT 记录 usage_logs
        LB-->>GW: 正常响应
    else 429 Too Many Requests
        LB->>CD: 上报429
        CD->>P: 移入冷却池 cooldown_until=now+30s×2^n

        LB->>LB: 重新选择 Provider B

        alt Provider B 正常
            LB->>P: 转发到 Provider B
            P-->>LB: 200 OK
        end

        alt 主池全部冷却
            Note over LB: 降级 Fallback 池<br/>检查即将恢复的Provider<br/>剩余<10s 等待

            alt Fallback 可用
                LB->>P: 转发 Fallback Provider
                P-->>LB: 200 OK +降级标记
            else Fallback 也全冷却
                LB->>P: 紧急通道 1 Provider 10% RPM
                alt 紧急通道成功
                    P-->>LB: 200 OK
                else
                    LB-->>OC: 503 Service Unavailable
                    OC->>OC: OpenClaw 自身 fallback
                end
            end
        end
    end