fix(a2a-client): recognize poll-mode 'queued' envelope (#2967) - #2972
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workspace-server's a2a_proxy poll-mode short-circuit returns
{status: "queued", delivery_mode: "poll", method: <a2a_method>}
when the peer has no URL to dispatch to (poll-mode peers, including
every external molecule-mcp standalone runtime). The bare
send_a2a_message parser only knew about JSON-RPC {result, error}
keys, so this envelope fell through to the "unexpected response shape"
error path. Two production symptoms on the reno-stars tenant traced
to it:
1. File transfer logged as failed when it actually succeeded —
operator-facing logs showed an A2A_ERROR but the receiving
workspace did get the chunked file via the agent's fallback path.
2. delegate_task retried after the false failure → peer received
duplicate delegations → conversation got confused, the second
peer self-diagnosed in a notify ("⚠️ Peer 二次请求 — 我先不执行").
Add a third branch to the parser, BETWEEN the existing JSON-RPC
{result, error} cases and the catch-all "unexpected" fallback. The
queued envelope is delivery-acknowledged-but-pending-consumption —
not an error — so it returns a clean success string the agent can
render as a normal outcome. The success string includes "queued"
and "poll" so an operator scanning logs sees the routing path
without parsing JSON.
Defensive: the new branch only fires when BOTH status="queued" AND
delivery_mode="poll" are present. A partial envelope (one key
missing) still falls through to the catch-all, so a future server
bug that emits a malformed shape gets surfaced instead of silently
swallowed.
Tests:
- test_poll_queued_envelope_returns_success_string — pins the canonical
envelope returns a non-error string. Discriminating: verified to FAIL
on old code (returned [A2A_ERROR] string), PASS on new.
- test_poll_queued_envelope_with_other_method — pins the parser doesn't
hardcode message/send. Discriminating: also FAILS on old code.
- test_status_queued_without_poll_mode_still_falls_through — pins both
keys are required (defensive against future server bugs).
12 existing tests in TestSendA2AMessage still pass — no regression.
Scope: hotfix for the bare send_a2a_message path. The full SSOT
typed-A2AResponse refactor (#158-#163, parents under #2967) covers the
broader vocabulary alignment between Go server and Python client. This
PR ends the production symptoms now without preempting that work.
HongmingWang-Rabbit
requested a review
from hongmingwang-moleculeai
as a code owner
May 5, 2026 23:59
HongmingWang-Rabbit
enabled auto-merge
May 5, 2026 23:59
This was referenced May 6, 2026
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Summary
Fixes the immediate production symptoms from #2967: external molecule-mcp standalone runtimes (which are inherently poll-mode) hit "unexpected response shape" on every A2A send to a poll-mode peer, causing false-failure logs + delegate_task retries that produced duplicate delegations.
The workspace-server's poll-mode short-circuit returns `{status:"queued", delivery_mode:"poll", method:...}` (`a2a_proxy.go:402`). The Python client only knew JSON-RPC `{result, error}` keys → fell through to the catch-all error path.
Adds a third parser branch BETWEEN the existing `{result, error}` cases and the catch-all "unexpected" fallback. Returns a clean queued-success string (no `_A2A_ERROR_PREFIX`) so callers route it through the normal-outcome path.
Scope
This is the hotfix for bare `send_a2a_message`. The broader SSOT typed-A2AResponse refactor (#158-#163 in #2967's plan) is out of scope — it ends the symptom now without preempting that longer arc.
Test plan
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