[rigel-mintaka]

What does this PR do?

Idle compaction (compression.idle_compact_after_seconds) never fired on gateway turns, such as Discord, Cotal and cron. _idle_compaction measured time.time() - _last_activity_ts, but two turn-start paths reset that timestamp first, so the gap was always about 0:

• gateway/run.py _init_cached_agent_for_turn (cached agent reuse);
• DurableTurnLease.start.

Related Issue

RIG-9162. Nemo enables idle compaction after this ships (RIG-9148).

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)

Changes Made

• gateway/run.py and agent/turn_facade_lease.py: save the elapsed gap into _idle_resume_gap_s before the clock reset, keeping the larger value if both run. The watchdog reset is unchanged.
• agent/turn_context_compaction.py: _idle_compaction reads and clears the saved gap, and falls back to the live gap if none was saved.
• tests/agent/test_compression_trigger_labels.py: a regression for the cached-turn reset path.

How to Test

1. The new regression fails before the fix (DID NOT RAISE _CompressionReached) and passes after.
2. The idle-compaction guard, trigger-label, lease and cached-agent suites: 53 passed.
3. Ruff passes.

Checklist

Code

• Conventional Commits
• Only this fix
• Regression test added

Documentation & Housekeeping

• Documentation: N/A. Idle compaction stays opt-in (default 0).

For New Skills

N/A.

Screenshots / Logs

N/A.

Refs RIG-9162

Co-authored-by: Matt Wilkinson matt@rigel.build

[linear-code]

RIG-9162

[rigel-mintaka]

Review rounds

Round 1 (107f54f): 0 high, 1 medium, 5 low.

• medium: no test covered the lease path. Fixed: tests/agent/test_idle_resume_gap.py covers the lease path, gateway then lease (max), and the clear when compression is disabled.
• low: copied save block. Fixed: shared save_idle_gap under _activity_lock.
• low: the carry rule was not stated. Fixed: comment and docs note.
• low: field not declared. Fixed: _TURN_STATE.
• low: the admission wait and the interrupt-recursive stall count as idle. Accepted: the cache is cold after that long either way.
• low: separate read and reset. Fixed by the locked helper.

Round 2 (interdiff 107f54f..e27ac75): 0 high, 0 medium, 1 low (a wordy comment; non-gating). 11 passed; ruff is clean. All-clear on e27ac75.

[rigel-mintaka]

Review all-clear on 71e3a1f (0 findings). The rebase over #50 moved only hunk context; the code hunks match all-clear e27ac75. Merge-ready.