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 Clients polling the old turn had no signal that it had been superseded.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

N/A -- pure coordination-plane logic fix, no user-visible UI or API shape change.

Demo

This is a pure backend coordination-plane fix -- no UI change, no API shape change. The observable behavior change is a correctness fix in a boolean field on an internal heartbeat response.

Test run demonstrating the fix (all 5 tests pass, including the new regression test):

PASSED test_uninterrupted_heartbeats_stay_current
PASSED test_cancel_between_beats_flips_next_beat_to_not_current
PASSED test_steer_flips_the_old_turns_next_beat_to_not_current
PASSED test_losing_owner_claim_reports_not_current
PASSED test_steer_via_command_flips_old_turn_heartbeat_to_not_current  <- new regression test
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 video or screen recording for UI changes, or marked Demo as N/A
• 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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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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All committers have signed the CLA.

[coderabbitai]

Caution

Review failed

The pull request is closed.

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⚙️ Run configuration

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Run ID: 5bda64c4-68e5-4a31-9954-085fb8eb7211

📥 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 when a session turn is replaced or its lock is cancelled.
  • Ensured older turns correctly report that they are no longer active after a command redirects the session.

• Tests

  • Added regression coverage for turn-steering commands and heartbeat status updates.

Walkthrough

Heartbeat interruption detection now checks the Redis alive-lock owner before using the durable turn row. A regression test exercises steering through command(force=True) and verifies that the displaced turn reports is_current_turn=False.

Changes

Heartbeat current-turn detection

Layer / File(s)	Summary
Heartbeat lock-owner detection api/oss/src/core/sessions/streams/service.py	Heartbeat processing uses the Redis alive-lock owner to distinguish turn displacement from initial lock establishment and marks displaced turns as stale.
Command steering regression coverage api/oss/tests/pytest/unit/sessions/test_heartbeat_is_current_turn.py	The test starts a turn, steers through command(force=True), and verifies that the original turn reports is_current_turn=False while a replacement turn exists.

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

Possibly related PRs

• Agenta-AI/agenta#5688: Modifies the same heartbeat current-turn logic and regression test.

✨ Finishing Touches 💡 1

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