Cancellation path never drains passive observer tasks, losing the side effects on_loop_cancelled exists to release

[zhanghanduo]

BaseObserver.on_loop_cancelled exists precisely because "cancellation bypasses on_loop_end". But the drain in notify_observers is keyed on on_loop_end alone:

if method == "on_loop_end":
    await drain_background_observers()

Consequence: on the cancellation path, passive tasks already scheduled — trajectory writes, metric flushes, event-sink appends — are never awaited. When the enclosing task tree is cancelled and the event loop closes, they are dropped: exactly the side effects the hook is meant to release.

Fix direction: drain on on_loop_cancelled too. Interacts with #2 — the drain should become loop-scoped in the same change rather than twice.

Provenance: pre-existing in ApodexHarness/miroharness/core/loop_types.py, ported verbatim by #1 — not introduced by the refactor. ApodexHarness carries the same code and needs the same change until it consumes AgentCore.

[zhanghanduo]

Fixed on main by 63dba6f, in the same change as #2 as this issue asked ("the drain should become loop-scoped in the same change rather than twice"). Not auto-linked because that commit's Refs trailer was written after a literal \n\n.

notify_observers now drains on both terminal paths (agent_core/loop_types.py:577):

if method in {"on_loop_end", "on_loop_cancelled"}:
    await drain_background_observers()

So trajectory writes, metric flushes and event-sink appends already scheduled are awaited before the cancellation path returns, instead of being dropped when the task tree unwinds.

Downstream: miroharness/core/loop_types.py still keys the drain on on_loop_end alone. Tracking that backport separately.

[zhanghanduo]

Correction to the "Downstream" note above.

That note is accurate for MiroHarness main, which still carries the standalone 790-line copy — but it is already stale for the integration branch. On refactor/agent-core, miroharness/core/loop_types.py is a 75-line compatibility facade that re-exports agent_core.loop_types (done by 1bedcc52 refactor: consume shared runtime contracts), and that branch pins:

apodex-agent-core @ git+ssh://git@github.com/ApodexAI/AgentCore.git@a9b5272d

git merge-base --is-ancestor 63dba6f a9b5272 confirms the pin already contains this fix.

So no backport is needed. The downstream copy is not being patched in parallel; it is being deleted by the extraction. MiroHarness main keeps the old code only until refactor/agent-core lands, and this fix arrives there through the pin rather than through a second edit.

The only product-specific symbol that stays behind in the facade is wall_deadline_remaining_s, which binds miroharness.core.execution_context and is registered as an allowed delta in scripts/contract/manifest.py.