fix: heartbeat is_current_turn false after steer via command()

[Christian-Sidak]

Summary

After a steer (interrupt + new message on a session), the displaced turn's heartbeat kept reporting is_current_turn: true. Clients polling the old turn had no signal that it had been superseded.

Root cause. heartbeat() used the durable row's turn_id to disambiguate a lock loss: if prior_stream.turn_id == request.turn_id the key being gone meant cancellation; if not, it looked like a first-beat race and was left as is_current_turn=True. A steer calls _start_turn(), which overwrites the durable row's turn_id with the new turn before the old turn's next heartbeat fires. So the old turn's beat always saw a "different" turn_id in the row, concluded "first-beat race", and stayed True -- even though it had been displaced.

Fix. When refresh_alive fails, read the alive lock's current holder directly via get_alive_owner. If the lock is held by a different turn_id, the old turn was displaced by a steer (is_current_turn=False). The durable row check (turn_was_established) is kept as the fallback for the cancel case (lock absent, row still matches our turn).

Files changed:

• api/oss/src/core/sessions/streams/service.py -- import get_alive_owner, fix is_current_turn logic in heartbeat()
• api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py -- regression test that goes through command() write path

Fixes #5790

Testing

Verified locally

• Ran api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py (all 5 tests pass)
• Ran related session unit tests (33 tests pass): test_command_matrix_inputs_data.py, test_project_scoped_locks.py, test_owner_claim.py, test_heartbeat_ownership.py, test_heartbeat_first_touch_race.py
• ruff format and ruff check pass on changed files

Added or updated tests

Added test_steer_via_command_flips_old_turn_heartbeat_to_not_current to test_heartbeat_is_current_turn.py. This test drives the real steer write path via command(force=True) -- the exact sequence from the bug report -- rather than manually simulating a lock cancellation. It verifies that after a steer via the command endpoint, the old turn's heartbeat reports is_current_turn=False.

QA follow-up

This is a pure coordination-plane logic fix with no user-visible UI or API shape change. All regression tests pass locally.

Demo

This fix changes only the backend coordination plane (the is_current_turn boolean in internal heartbeat responses). There is no UI, no API shape change, and no user-visible output to record.

The demo below shows the full pytest run confirming the fix: the new regression test test_steer_via_command_flips_old_turn_heartbeat_to_not_current drives the exact steer sequence from the bug report end-to-end through command(force=True) and verifies is_current_turn=False for the displaced turn. Without this fix, that test fails on main.

$ pytest api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py -v
============================= test session starts ==============================
collected 5 items

test_heartbeat_is_current_turn.py::test_uninterrupted_heartbeats_stay_current PASSED
test_heartbeat_is_current_turn.py::test_cancel_between_beats_flips_next_beat_to_not_current PASSED
test_heartbeat_is_current_turn.py::test_steer_flips_the_old_turns_next_beat_to_not_current PASSED
test_heartbeat_is_current_turn.py::test_losing_owner_claim_reports_not_current PASSED
test_heartbeat_is_current_turn.py::test_steer_via_command_flips_old_turn_heartbeat_to_not_current PASSED

============================== 5 passed in 1.84s ===============================

The new test would fail on main (before this fix) because the old code's durable-row comparison cannot detect the steer displacement.

Checklist

• I have included a demo of the fix (pytest output above showing all 5 tests pass, including the new regression test for the bug scenario)
• Relevant tests pass locally
• Relevant linting and formatting pass locally
• I have signed the CLA, or I will sign it when the bot prompts me

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All committers have signed the CLA.

[github-actions]

Hi @Christian-Sidak, thanks for opening a pull request. 🙏

This PR was automatically closed because it does not yet meet our contribution requirements:

• This PR changes functional code (SDK, API, or frontend) but includes no demo. Add a screenshot or short video of the change. Only test-only, docs-only, or chore changes may skip it.

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Run ID: 11a45b5d-5cfb-48cd-b163-3b4bb7bae93e

📥 Commits

Reviewing files that changed from the base of the PR and between e73fb2e and 0cd4d02.

📒 Files selected for processing (2)

• api/oss/src/core/sessions/streams/service.py
• api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py

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📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes

  • Improved heartbeat interruption detection during turn steering and cancellation.
  • Prevented stale turns from continuing when another turn takes ownership or the active lock disappears.
  • Preserved correct behavior for initial heartbeat races.

• Tests

  • Added regression coverage for command-based steering and displaced-turn heartbeat status.

Walkthrough

Heartbeat interruption detection now checks Redis alive-lock ownership. Displaced turns become non-current when another turn owns the lock. Established turns become non-current when the lock disappears. A command-path regression test covers force steering.

Changes

Heartbeat ownership detection

Layer / File(s)	Summary
Alive-lock heartbeat evaluation api/oss/src/core/sessions/streams/service.py	Heartbeat refresh failures now use the Redis alive-lock owner to distinguish steering, cancellation, and initial heartbeat races.
Command-path steering regression api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py	The test starts a turn, force-steers a replacement through command(), and verifies that the displaced turn reports is_current_turn=False.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• Agenta-AI/agenta#5688: Extends related heartbeat stale-turn handling and steering tests.
• Agenta-AI/agenta#5820: Describes the same alive-lock ownership detection changes.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

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