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.
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