sequenceDiagram
    participant Client
    participant App
    participant State
    participant StateProxy

    Note over App,State: Upload Handler Flow
    Client->>App: Upload request with handler name
    App->>State: _get_event_handler(handler_string)
    State->>State: Parse handler path
    State->>State: Get substate and handler
    State-->>App: Return (substate, event_handler)
    App->>App: Check if background task
    alt is background task
        App->>App: Raise UploadTypeError
    else not background task
        App->>App: Process upload with handler.fn
    end

    Note over App,StateProxy: Background Task Flow
    Client->>App: Event request
    App->>State: _get_event_handler(event)
    State->>State: Parse event.name
    State->>State: Get substate and handler
    State-->>App: Return (substate, handler)
    App->>App: Check if background task
    alt is background task
        App->>StateProxy: Wrap substate in StateProxy
        StateProxy->>StateProxy: Create async task
    else not background task
        App->>State: Process event normally
    end