sequenceDiagram
    autonumber
    actor User as 员工
    participant H5 as H5 ConversationStore
    participant WS as FastAPI ws.py
    participant DB as PostgreSQL/messages
    participant WSM as ws_manager
    participant Agent as 坐席 Store/MessageBubble
    participant Task as h5_ai_task.py
    participant Dify as Dify Workflow
    participant REST as messages.py

    User->>H5: 点击选项
    H5->>H5: 首次生成 client_msg_id(UUID)
    H5->>WS: option_select(6字段)
    WS->>DB: BEGIN + pg_advisory_xact_lock(key)
    WS->>DB: 查询同会话同 client_msg_id
    alt 5秒内重复
        DB-->>WS: 返回首次 Message
        WS-->>H5: 不重复落库/广播/Dify
    else 首次受理
        WS->>DB: INSERT Message(msg_type=option_select)
        WS->>DB: COMMIT
        WS->>WSM: broadcast new_message(masked message)
        WSM-->>Agent: new_message
        Agent->>Agent: 追加消息并按 question_id 计算最新
        WS->>Task: create_task(feedback_context)
        Task->>Dify: inputs{feedback_type, question_id, option_id...}
        Dify-->>Task: 下一轮结构化回复
    end
    Agent-xWSM: 网络断开
    Agent->>REST: GET /conversations/{id}/messages
    REST->>DB: SELECT conversation_id ORDER BY created_at
    DB-->>REST: 含 option_select 历史
    REST-->>Agent: masked items
    Agent->>Agent: 用 created_at + id 恢复最新高亮