Introduce ``workspace/a2a_response.py`` as the single source of truth for
the wire shapes the workspace-server proxy can return at
``/workspaces/<id>/a2a``:
* ``Result`` — JSON-RPC success
* ``Error`` — JSON-RPC error or platform-level error (with
restart-in-progress metadata when present)
* ``Queued`` — poll-mode short-circuit envelope: the platform
queued the message into the target's inbox, the
target will fetch via /activity poll
* ``Malformed`` — anything the parser can't classify (logged at
WARNING so a future server change is loud)
``send_a2a_message`` (in ``a2a_client.py``) now dispatches via
``a2a_response.parse(data)`` instead of inline ``"result" in data`` /
``"error" in data`` sniffing. The Queued variant returns a new
``_A2A_QUEUED_PREFIX`` sentinel so callers can distinguish "delivered
async, no synchronous reply" from both success-with-text and failure.
reno-stars production data caught two intermittent failures that
both reduced to the same root cause:
1. **File transfer announce silently failed** — when CEO Ryan PC
(poll-mode external molecule-mcp) sent the harmi.zip
announcement to Reno Stars Business Intelligent (also poll-mode
external), ``send_a2a_message`` saw the platform's poll-queued
envelope ``{"status":"queued","delivery_mode":"poll","method":"..."}``,
didn't recognize it as the synthetic delivery-acknowledgement
it is, and returned ``[A2A_ERROR] unexpected response shape``.
The agent fell back to a chunk-shipping path; receiver did get
the file but operator-facing logs showed a failure that didn't
actually fail.
2. **Duplicated agent comm** — same bug, inverted direction. d76
delegated to 67d, send_a2a_message returned the unexpected-shape
error, delegate_task wrapped it as DELEGATION FAILED, the calling
agent retried with sharper wording, the recipient saw the same
request twice and self-reported "二次请求 — 我先不执行".
External molecule-mcp standalone runtimes are inherently poll-mode
(they have no public URL), so every external↔external A2A pair was
hitting this on every send. The pre-fix client only handled JSON-RPC
``result``/``error`` keys and treated the queued envelope (which has
neither) as malformed. RFC #2339 PR 2 added the queued envelope on
the server side; the client never caught up.
When ``send_a2a_message`` returns the ``_A2A_QUEUED_PREFIX`` sentinel,
``tool_delegate_task`` now transparently falls back to
``_delegate_sync_via_polling`` (RFC #2829 PR-5's durable
``/delegate`` + ``/delegations`` polling path, which DOES work for
poll-mode peers because the platform's executeDelegation goroutine
writes to the inbox queue and the result row arrives when the target
picks it up + replies). The agent gets a real synchronous reply
instead of the empty queued sentinel.
* ``test_a2a_response.py`` — 62 tests, **100% line coverage** on
the parser (verified via ``coverage run --source=a2a_response``).
Includes adversarial-input fuzzing across ~25 pathological
payloads — parser must never raise.
* ``test_a2a_client.py::TestSendA2AMessagePollMode`` — 4 tests for
the new Queued/Error wiring in ``send_a2a_message``.
* ``test_delegation_sync_via_polling.py::TestPollModeAutoFallback``
— 3 tests for the auto-fallback in ``tool_delegate_task``,
including negative cases (push-mode reply must NOT trigger
fallback; genuine error must NOT silently retry).
* **Verified all new tests FAIL on pre-fix source** by stashing
a2a_client.py + a2a_tools_delegation.py and re-running — 5
failures including ImportError for the missing
``_A2A_QUEUED_PREFIX``.
Per the operator-debuggability directive:
* INFO at every Queued classification (expected variant; operator
sees normal poll-mode-peer queueing in log stream).
* INFO at the auto-fallback decision in ``tool_delegate_task``
so a future operator can correlate "send returned queued →
falling back to polling path" without reading the source.
* WARNING at every Malformed classification (server contract
drift; operator MUST see this immediately).
* Existing transient-retry WARNING preserved.
* Mirror Go-side typed model in workspace-server. The wire shape
is documented in ``a2a_response.py``'s module docstring with
file:line pointers to the canonical emitters; a future PR can
introduce ``models/a2a_response.go`` without changing wire
behavior. The fixture corpus in ``test_a2a_response.py`` is
designed so a one-sided edit breaks CI.
* ``send_message_to_user`` and ``chat_upload_receive`` use a
different endpoint (``/notify``) and aren't affected by this
bug; their parsing stays unchanged.
* 135 tests pass across ``test_a2a_response.py`` +
``test_a2a_client.py`` + ``test_delegation_sync_via_polling.py``
+ ``test_a2a_tools_impl.py``.
* ``coverage run --source=a2a_response -m pytest`` reports 100%
line coverage with 0 missing.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
8b9f809966