fix(sdk): poll-driven cross-reasoner pause propagation

[AbirAbbas]

Summary

The v0.1.80 listener-based pause propagation never fired in production because it depended on the SDK's SSE event-stream subscription, which is gated behind enable_event_stream (default False) and not enabled on any deployed service.

Reproduced on Railway run run_1778268481826_8c9dd544: implement_from_issue timed out at exactly 7200s wallclock despite a ~21min hax-sdk approval gap clearly visible in the SWE-AF logs (20:10:42 → 20:31:35) and a second silent gap before the timeout.

Why the listener didn't fire

• Control plane DOES publish execution_waiting to the bus (verified in execute_approval.go).
• Parents subscribe to that bus only when enable_event_stream=True. Default is False and no service overrides it. Verified via railway ssh ... env: no service has the var set, and the only subscriber on the live SSE bus is the user's browser.
• So register_status_listener callbacks were never invoked, pause_clock.start_pause() was never called, total_paused() stayed at 0, active_elapsed == wallclock, watchdog tripped at the budget.

The previous tests poked _on_child_status_change and _handle_event_stream_payload directly, which bypassed the enable_event_stream gate entirely. They passed; production was broken.

Fix

Replace the SSE-listener mechanism with a poll-driven toggle inside wait_for_result:

• The polling task already runs unconditionally and already updates _executions[id].status from control-plane responses (_update_execution_from_status).
• wait_for_result now reads that status each loop iteration. When it reads as WAITING, the parent's pause_clock.start_pause() is called; when it reads back as anything else, end_pause() is called. A finally block closes any in-flight pause if we exit via terminal / timeout / exception.
• No SSE subscription needed. No listener registry. No refcount machinery. Works whether or not enable_event_stream is on.

Removed

• async_execution_manager.py: register_status_listener, _status_listeners, _fire_status_listeners, the execution.waiting event-type override (the WAITING-status branch in _handle_event_stream_payload stays for when SSE is on).
• agent.py: _on_child_status_change, _waiting_children, _parent_paused_children, the listener registration in call(). The pause_clock kwarg pass-through (the actual fix) is preserved.

Net: −387 / +274 lines across 4 files.

Tests

Replaced the listener tests with integration tests that drive the production data path: they update _executions[id].status the same way the polling task does, then assert wait_for_result toggles the parent clock and survives a long WAITING window. Includes a regression for the headline scenario (WAITING window > wait_timeout, must complete) and a finally-block check for cancelled-while-waiting.

Test plan

• cd sdk/python && ruff check . — clean
• cd sdk/python && python -m pytest --no-cov — 1482 passed, 4 skipped (integration tests requiring server sources, pre-existing)
• CI green
• Verify on Railway after release: re-run an implement_from_issue flow that hits the hax-sdk gate; parent should not time out at wallclock 2hr if active work < 2hr

🤖 Generated with Claude Code

[github-actions]

Performance

SDK	Memory	Δ	Latency	Δ	Tests	Status
Python	9.4 KB	+4%	0.31 µs	-11%	✓	✓

✓ No regressions detected

[github-actions]

📊 Coverage gate

Thresholds from .coverage-gate.toml: per-surface ≥ 86%, aggregate ≥ 88%, max per-surface regression ≤ 1.0 pp, max aggregate regression ≤ 0.50 pp.

Surface	Current	Baseline	Δ
control-plane	87.40%	87.30%	↑ +0.10 pp	🟡
sdk-go	91.90%	90.70%	↑ +1.20 pp	🟢
sdk-python	93.66%	93.63%	↑ +0.03 pp	🟢
sdk-typescript	92.68%	92.56%	↑ +0.12 pp	🟢
web-ui	89.91%	90.01%	↓ -0.10 pp	🟡
aggregate	88.99%	89.01%	↓ -0.02 pp	🟡

✅ Gate passed

No surface regressed past the allowed threshold and the aggregate stayed above the floor.

[github-actions]

📐 Patch coverage gate

Threshold: 80% on lines this PR touches vs origin/main (from .coverage-gate.toml:thresholds.min_patch).

Surface	Touched lines	Patch coverage	Status
control-plane	0	—	➖ no changes
sdk-go	0	—	➖ no changes
sdk-python	0	—	➖ no changes
sdk-typescript	0	—	➖ no changes
web-ui	0	—	➖ no changes

✅ Patch gate passed

Every surface whose lines were touched by this PR has patch coverage at or above the threshold.