Switches `_replay_session_history` from `loop.call_soon`-deferred (after the
`LoadSessionResponse` is written) to `await`-inline (before the response is
constructed) for both `session/load` and `session/resume`. Adds defensive
try/except around the awaited call so a replay helper crash still yields a
successful load response — partial transcripts are acceptable, total
load failure is not.
The deferral was added on May 2 in commit 19854c7cd with the rationale "Zed
only attaches streamed transcript/tool updates once the load/resume response
has completed." That justification was incorrect:
- Zed's current ACP integration (zed-industries/zed
crates/agent_servers/src/acp.rs) explicitly registers the session-update
routing entry BEFORE awaiting the loadSession RPC, with the comment:
"so that any session/update notifications that arrive during the call
(e.g. history replay during session/load) can find the thread."
- Every other reference ACP server (Codex, Claude Code, OpenCode, Pi, agentao)
replays history BEFORE responding to the load request.
- The ACP spec wording ("Stream the entire conversation history back to the
client via notifications") and the natural JSON-RPC reading both mean
"during the request's lifetime", not "after the response resolves".
Empirical reproduction (reported by Biraj on @agentclientprotocol/sdk
v0.21.1): the same custom ACP client works correctly against Codex /
Claude Code / OpenCode / Pi but receives 0 notifications from Hermes
because it measures the per-call notification count at the moment
`loadSession` resolves — which on Hermes was before the `call_soon`-
scheduled replay coroutine had a chance to run.
Changes:
- `acp_adapter/server.py`: remove `_schedule_history_replay`; both
`load_session` and `resume_session` now `await self._replay_session_history`
before returning, wrapped in try/except that logs and continues on
helper exceptions.
- `tests/acp/test_server.py`: replace the single
`test_load_session_schedules_history_replay_after_response`
(which encoded the now-incorrect post-response ordering) with two tests
asserting `events == ["replay", "returned"]` for load and resume.
Add two regression tests confirming that a replay helper raising still
yields a `LoadSessionResponse` / `ResumeSessionResponse` rather than
propagating the exception out as a JSON-RPC error.
Result: 240 ACP tests pass (was 238), ruff clean. Verified end-to-end:
biraj's synchronous notification-counter pattern now sees 6 notifications
during `loadSession` for a 5-message session, matching all other reference
ACP servers.
The `_fenced_text` change in `acp_adapter/tools.py` from the same May 2
commit is orthogonal and intentionally left intact — it's a separate,
still-valid fix for Zed's pipe-as-table rendering.
Refs #12285. Follows up #26943 (which added thought-chunk replay but kept
the deferral).
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