Method on

python/copilot/session.py:1684–1718

Subscribe to events from this session. Events include assistant messages, tool executions, errors, and session state changes. Multiple handlers can be registered and will all receive events. Args: handler: A callback function that receives sessi

(self, handler: Callable[[SessionEvent], None])

            unsubscribe()

    def on(self, handler: Callable[[SessionEvent], None]) -> Callable[[], None]:
        """
        Subscribe to events from this session.

        Events include assistant messages, tool executions, errors, and session
        state changes. Multiple handlers can be registered and will all receive
        events.

        Args:
            handler: A callback function that receives session events. The function
                takes a single :class:`SessionEvent` argument and returns None.

        Returns:
            A function that, when called, unsubscribes the handler.

        Example:
            >>> from copilot.session_events import AssistantMessageData, SessionErrorData
            >>> def handle_event(event):
            ...     match event.data:
            ...         case AssistantMessageData() as data:
            ...             print(f"Assistant: {data.content}")
            ...         case SessionErrorData() as data:
            ...             print(f"Error: {data.message}")
            >>> unsubscribe = session.on(handle_event)
            >>> # Later, to stop receiving events:
            >>> unsubscribe()
        """
        with self._event_handlers_lock:
            self._event_handlers.add(handler)

        def unsubscribe():
            with self._event_handlers_lock:
                self._event_handlers.discard(handler)

        return unsubscribe

    def _dispatch_event(self, event: SessionEvent) -> None:
        """