Drop _compat.py: if mcp/python-sdk#2610 still silent on 2026-06-12, port the fix as our own upstream PR — due 2026-06-12 #127

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1. mlorentedev

   added a commit that references this issue on May 28, 2026

   chore: WAL cleanup + DX bundle (test-one, logs, cross-platform clean) (…

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2. mlorentedev commented on Jun 12, 2026

   

   mlorentedev

   on Jun 12, 2026 – with Claude

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   +21d escalation checkpoint — upstream still silent

   Hey @mlorentedev — it has been 21 days since PR-4 shipped. Upstream modelcontextprotocol/python-sdk#2610 is still OPEN with no new maintainer engagement since 2026-05-22. The installed mcp 1.27.2 (latest within the pinned >=1.26,<2.0 range) still carries the raw assertion at mcp/shared/session.py:129:

   assert not self._completed, "Request already responded to"

   No if self._completed: return guard exists anywhere in RequestResponder.__exit__ or respond(). The upstream fix has not shipped.

   Recommended action: port the fix ourselves

   src/hive/_compat.py is small, self-gated, and battle-tested across the four HIVE-115 PRs. Porting it to upstream is mostly a translation exercise:

   1. Fork modelcontextprotocol/python-sdk.
   2. Apply the same patch shape to mcp/shared/session.py (the _patched_exit and _patched_respond logic from _compat.py becomes inline guards in RequestResponder.__exit__ and respond).
   3. Port the regression test from tests/test_compat_shim.py::test_classify_cancellation_race — adapt to upstream's test layout.
   4. Open the PR referencing modelcontextprotocol/python-sdk#2610 and mlorentedev/hive#127.

   Estimated effort

   • ~2 hours coding (the work is already done; just translation + test port)
   • ~30 min review prep (cite the two independent reports: ours + jshaofa-ui 2026-05-16)
   • Variable review wait at upstream

   Outcome routes from here

   • Port the fix — open the upstream PR, comment its URL here, leave this issue open. Set a new +30d deadline to check on review state.
   • Defer 14 more days — comment with reason, leave open, update title due-date to 2026-06-26.
   • Accept _compat.py as permanent — comment with rationale (shim is stable, pin caps risk, upstream effort budget needed elsewhere), close with wontfix label. Reopen only if the shim begins failing.

   ---

   Posted by the +21d remote routine (one-shot, scheduled 2026-05-22 alongside this issue + the vault TODO for belt-and-braces — _meta/patterns/pattern-triple-reminder-belt-and-braces). Do not reschedule; the next step is a human call.

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   Generated by Claude Code
3. mlorentedev commented on Jun 19, 2026

   

   mlorentedev

   on Jun 19, 2026

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   Decision gate resolved — re-pointed to two distinct upstream races

   Re-evaluated against installed mcp 1.26.0. The original gate tracked python-sdk#2610, but the _compat.py workaround actually covers two distinct races with two distinct upstream trackers — so the gate is now split accordingly.

   1. __exit__ CancelledError leak (issue #75) — REMOVED ✅

   Upstream: python-sdk#2610 (open) · fix proposed in PR #2624 (open).

   On mcp 1.26.0 the issue-#75 symptom no longer reproduces. Server._handle_request catches the in-flight handler cancellation before it can reach RequestResponder.__exit__:

   except anyio.get_cancelled_exc_class():
       logger.info("Request %s cancelled - duplicate response suppressed", message.request_id)
       return

   That guard masks the leak regardless of whether #2610/#2624 land, so the __exit__ monkey-patch is redundant and has been removed.

   Coverage was preserved, not dropped: the old reproduction was a Windows-only subprocess test, so a new deterministic, cross-platform regression test now drives a real lowlevel Server receive loop and sends an actual notifications/cancelled mid-handler — tests/test_transport_recovery.py::TestProtocolLevelCancellation. It fails on any platform if the masking behaviour regresses (e.g. a future mcp/anyio bump).

   2. respond() "Request already responded to" assertion — STILL PATCHED

   Upstream: python-sdk#2416 (open) — not #2624 (that PR fixes only __exit__).

   This is the narrow race where notifications/cancelled marks the responder _completed between handler completion and respond(), firing assert not self._completed at mcp/shared/session.py:129. hive is unusually exposed via _helpers.run_sync_tool (git on a worker thread that can call respond() late). The respond short-circuit in hive._compat stays, guarded by tests/test_concurrency_fixes.py::TestRespondPatchPreventsKill.

   New gate

   Watch python-sdk#2416. Drop the remaining respond patch once a guarded respond() ships within our pinned mcp >=1.26,<2.0 range. Re-check by 2026-07-18.

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   Housekeeping: the previous checkpoint referenced tests/test_compat_shim.py::test_classify_cancellation_race, which no longer exists — the guards now live in tests/test_concurrency_fixes.py and tests/test_transport_recovery.py.
4. mlorentedev commented on Jun 19, 2026

   

   mlorentedev

   on Jun 19, 2026

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   Correction — re-validated on the pinned mcp (1.27.2), now in PR #248

   My checkpoint above was drafted against a local env pinned to mcp 1.26.0 on a stale branch. The repo actually pins mcp>=1.27,<2.0, so I re-validated against mcp 1.27.2 before implementing. The conclusions hold:

   • The __exit__ patch is redundant on mcp >=1.27: a real notifications/cancelled mid-handler on a bare lowlevel Server with no hive patches survives on 1.27.2 (Server._handle_request catches the in-flight cancellation via except anyio.get_cancelled_exc_class(): ... return when message.cancelled, before RequestResponder.__exit__).
   • The respond() race (python-sdk#2416) is not covered by that guard and stays patched (with its ghost-response observability).

   Implemented in #248 — removes the __exit__ patch, keeps the respond() patch, and adds a deterministic cross-platform regression test (TestProtocolLevelCancellation) so the masking behaviour is guarded on every platform (not just the prior Windows-only subprocess test).

   Gate unchanged: watch python-sdk#2416; re-check 2026-07-18.
5. mlorentedev

   added a commit that references this issue on Jun 19, 2026

   refactor(compat): drop redundant RequestResponder.__exit__ patch (#248)

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   7578aa3
6. mlorentedev commented on Aug 8, 2026

   

   mlorentedev

   on Aug 8, 2026

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   This ticket's premise no longer holds

   Re-checked today against the code and all three upstream trackers. The escalation condition here is written as "if modelcontextprotocol/python-sdk#2610 is still silent on 2026-06-12, port the fix as our own upstream PR". Both halves of that have moved.

   1. _compat.py no longer depends on #2610. The __exit__ patch this ticket was written about has already been removed. _compat.py's docstring records why: the issue-#75 symptom stopped reproducing on mcp >= 1.27, because Server._handle_request catches the in-flight handler cancellation (except anyio.get_cancelled_exc_class(): ... return when message.cancelled) before it can reach RequestResponder.__exit__ — masking the leak whether or not #2610 ever lands. tests/test_transport_recovery.py guards that masking behaviour cross-platform.

   What remains in _compat.py is a patch on RequestResponder.respond, for a different upstream bug.

   2. #2610 already has an upstream fix PR. #2624 ("Fix completed request cancellation cleanup") is open. Porting the __exit__ fix ourselves would duplicate it.

   What the ticket should be about

   The shim we actually still carry tracks python-sdk#2416 — "AssertionError: Request already responded to — cancellation race in v1.27.0". Current state:

   • Open, last activity 2026-07-11.
   • Maintainer bot confirmed the bug on both main and origin/v1.x; respond() asserts not self._completed at session.py:133.
   • Reproduced independently by another user on Windows via Claude Code's stdio transport.
   • We already posted our reproduction and the guard we use, on 2026-06-19.
   • On 2026-07-11 a contributor said they intend to fix it — "replace assert not self._completed with a silent early return in RequestResponder.respond()", which is materially the same fix as ours. No PR has appeared in the ~4 weeks since.

   So the escalation logic still applies, just aimed at #2416 instead. The etiquette wrinkle is that the issue is informally claimed: opening a competing PR without a ping would be rude. Suggested sequence — comment on #2416 offering to open the PR if the volunteer has stalled, wait a short window, then port our guard.

   Adjacent finding

   AGENTS.md carried all three stale facts (wrong patch target, wrong tracker, and a stale mcp pin quoted as >=1.26,<2.0 when it is now >=1.27,<3.0). Corrected in #336.

   That PR also flags a lost guard: the narrow <2.0 cap existed so a major RequestResponder refactor could not silently break the shim, and #316 widened it to <3.0, which admits mcp 2.x — exactly the boundary the cap excluded. Not a live bug (apply() degrades loudly), but worth a deliberate decision on whether to re-narrow.

   Proposed retitle / rescope

   Drop _compat.py: gated on python-sdk#2416 (respond-after-cancel), not #2610 — ping the volunteer, then port our guard if stalled
7. mlorentedev

   self-assigned this

   on Aug 8, 2026
8. mlorentedev

   added 2 commits that reference this issue on Aug 8, 2026

   docs(lessons): capture three lessons from the ADR-018 rescope session (…

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   docs: correct the compat-shim description in AGENTS.md (#336)

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9. mlorentedev commented on Aug 8, 2026

   

   mlorentedev

   on Aug 8, 2026

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   Upstream state verified 2026-08-07 — the premise in this issue and in the last handoff was wrong on two counts

   1. The tracker is #2416, not #2610. This issue is written entirely around #2610, but the __exit__ patch that #2610 covers was already removed — the issue-#75 symptom stopped reproducing on mcp >= 1.27, where Server._handle_request catches the cancellation first. What _compat.py actually patches today is RequestResponder.respond, which is #2416. (#2610 also already has an open upstream fix PR, #2624.) This was established in the 2026-08-07 review; recording it here so the issue body stops pointing at the wrong tracker.

   2. "Claimed 2026-07-11 with no PR since" was false. The handoff carried this, but the claim was a PR:

   Date	Event
   2026-04-10	#2418 opened — still open, but untouched since the day it was created
   2026-05-18	#2417 closed by maxisbey, no comment
   2026-06-19	We commented on #2416 with hive's guard
   2026-06-23	#2949 closed by maxisbey, no comment
   2026-07-11	shivamsingh-007 claims it and opens #3088 the same day
   2026-07-19	shivamsingh-007 closes their own PR

   The reason the handoff missed this: PRs referencing an issue do not appear in that issue's comment thread once closed unmerged. They have to be searched for separately.

   What this changes

   The lane is clear — there is no active claimant to defer to, so the "ping the claimant first" protocol no longer applies. But a new signal replaces it: four community PRs, none merged, two closed by a core contributor without any stated reason. A fifth blind community PR is a poor bet.

   So the escalation was re-shaped rather than executed: a maintainer-directed comment now asks whether a fix would be accepted and against which base (main, v1.x, or both) before any PR is written — #2416 comment.

   Next step: wait for a maintainer answer. PR authorization is deferred until there is one, or until silence makes the answer moot.
10. mlorentedev

    added a commit that references this issue on Aug 8, 2026

    fix(deps): re-narrow the mcp cap to <2.0 and correct its rationale (#345

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11. mlorentedev commented on Sep 25, 2026

    

    mlorentedev

    on Sep 25, 2026

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    Superseded by #443 (merged 2026-09-25). hive now requires mcp 2.x, whose dispatcher never answers a cancelled request, so the RequestResponder.respond patch was deleted instead of waiting for python-sdk#2416 (which stays open for the 1.x line). tests/test_cancel_race.py guards the behaviour: it fails on 1.x without the patch and passes on 2.2.0.

    src/hive/_compat.py still exists, but it holds only the GHOST_RESPONSES counter. Deleting the file, and deciding what feeds the counter's cancellation source on 2.x, is tracked in #442. Closing this as done by #443.
12. mlorentedev

    closed this as completedon Sep 25, 2026