classDiagram
    class OptionSelectPayload {
        +string conversation_id
        +string option_label
        +string option_value
        +string selected_from_message_id
        +UUID client_msg_id
        +string question_id
        +string option_id
        +validate() bool
    }
    class Message {
        +string id
        +string conversation_id
        +string sender_type
        +string sender_id
        +string content
        +string msg_type
        +dict extra_data
        +datetime created_at
        +__init__(...)
    }
    class OptionSelectHandler {
        +__init__(session_factory, ws_manager)
        +handle(payload, employee_id) Message
        -acquire_advisory_lock(db, key) void
        -find_duplicate(db, payload) Message
        -persist(db, payload, employee_id) Message
        -to_message_dict(message, masked) dict
    }
    class SensitiveMask {
        +mask_sensitive_text(text) string
        +mask_sensitive_value(value) string
    }
    class DifyFeedbackContext {
        +string feedback_type
        +string question_id
        +string option_id
        +string option_value
        +string option_label
        +to_inputs() dict
    }
    class SelectedOptionsSnapshotBuilder {
        +__init__(db)
        +build(conversation_id) list
    }
    class ConnectionManager {
        +dict active_connections
        +dict employee_connections
        +__init__()
        +broadcast(data) void
        +broadcast_to_employees(ids, data) void
    }
    class ConversationStore {
        +Message[] messages
        +sendOptionSelect(selection) void
        +handleNewMessage(data) void
        +latestSelection(question_id) Message
    }
    class MessageBubble {
        +Message message
        +isLatestSelection() bool
        +maskedContent() string
    }

    OptionSelectHandler --> OptionSelectPayload : validates
    OptionSelectHandler --> Message : creates/returns
    OptionSelectHandler --> SensitiveMask : masks outbound data
    OptionSelectHandler --> ConnectionManager : broadcasts
    OptionSelectHandler --> DifyFeedbackContext : creates after commit
    SelectedOptionsSnapshotBuilder --> Message : queries latest per question
    ConversationStore o-- Message : stores
    MessageBubble --> ConversationStore : derives latest
    MessageBubble --> Message : renders