RemoteA2aAgent handlers crash on None converter results (AttributeError)

[YizukiAme]

Bug Description

In remote_a2a_agent.py, both _handle_a2a_response() (legacy) and _handle_a2a_response_v2() access attributes like event.content or event.custom_metadata on results from convert_a2a_message_to_event() / convert_a2a_task_to_event() without checking for None. This results in AttributeError when a converter legitimately returns None.

Additionally, the legacy handler still uses the outdated event_converter.py path instead of the newer to_adk_event.py converters, and update.context_id is ignored in favor of task.context_id only.

Steps to Reproduce

This can be triggered when a remote A2A agent sends:

• A message with no convertible parts
• A task snapshot with no artifacts and no status message
• A status update where the message converter returns None

Expected Behavior

Handlers should guard against None converter results with early returns.

Affected Files

• src/google/adk/agents/remote_a2a_agent.py

[enjoykumawat]

I'd like to work on this. The fix is a None-check on converter results before accessing attributes. Will submit a PR shortly.

[sanketpatil06]

Hello @YizukiAme,
Thank you for reporting this issue and providing the details. I was able to reproduce it on my end.

The AttributeError occurs because the asynchronous _handle_a2a_response method tries to access attributes of an empty event. This happens when the internal converter processes A2A status updates that are empty or contain only metadata.

Pull Requests #5199 and #5219 have already been opened to address this, and our team is currently reviewing them.

We truly appreciate your contributions!