[Bug]: EventConsumer treats TASK_STATE_UNSPECIFIED as terminal and closes the queue

[anxkhn]

What happened?

Legacy EventConsumer.is_final_event (src/a2a/server/events/event_consumer.py) includes TASK_STATE_UNSPECIFIED in the stop set. That is the proto default (value 0), not a finished state.

Spec 4.1.3: unspecified is unknown/indeterminate. Terminal is COMPLETED / FAILED / CANCELED / REJECTED. V2 TERMINAL_TASK_STATES already omits unspecified.

If an agent enqueues a Task without setting status, or a status update that omits state, consume_all closes the queue. Later WORKING/COMPLETED events never arrive on the legacy message/send, stream, cancel, and subscribe paths.

Repro

1. Enqueue Task(id=..., context_id=...) with default status.
2. Then enqueue WORKING and COMPLETED updates.

Observed: only the first Task is yielded and the queue is closed.
Expected: unspecified is non-final; WORKING and COMPLETED are still consumed.

Relevant log output

n/a. Covered by a consume_all unit test.

Code of Conduct

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[mykytanetipa]

EventConsumer is reachable only via deprecated LegacyRequestHandler + EventQueueLegacy, it's a 0.3.x deprecated path that exists purely for compatibility of un-migrated 1.x users and 0.3.x-compat clients.

Given that, I'd lean against patching the deprecated consumer at all, it adds churn/risk to a path we're retiring, and the real fix is migrating to V2 (already bug-free)

@rohityan what do you think?

[rohityan]

Hi @anxkhn , thanks for reporting this issue and contributing towards a fix.
I agree with @mykytanetipa since this path is slated for removal and V2 handles event streaming natively.

[rohityan]

Hi @ishymko , PTAL

[mykytanetipa]

Closing based on the comment above. Please let us know if it causes a real production issue; otherwise the recommended path is migrating to 1.x.