fix(tmux): post-spawn liveness check for silent in-pane exit (issue #513) by bradbrok · Pull Request #531 · bradbrok/PinkyBot

bradbrok · 2026-05-18T02:24:17Z

Summary

Implements the structural defense from issue #513.

Root cause: tmux new-session returns 0 as long as the child shell + command launched. If the in-pane command exits immediately (bad flag, auth error, missing binary, API rejection, etc.) the detached session auto-reaps silently. The caller sees a successful spawn; the state machine ends up CONNECTED against nothing and queued messages stack forever.
Fix: After new_session() succeeds in _spawn_tmux_repl(), wait ~150ms then call has_session(). If the session is gone, raise RuntimeError so the existing BOOTING → DEAD via BOOT_FAILED transition fires correctly — same path as any other spawn failure.
Tunable: _SPAWN_LIVENESS_DELAY_SEC = 0.15 constant alongside _COLD_START_TIMEOUT_SEC; tests patch it to 0 for speed.
_make_mock_tmux() updated to use itertools.chain([has_session_initial], repeat(True)) so the pre-spawn stale-check and post-spawn liveness-check get the right values without breaking any existing test.

Test plan

New test test_cold_start_session_dies_immediately_drives_to_dead: spawn succeeds, both has_session calls return False → RuntimeError("session died immediately after spawn") → state == DEAD
All 9 cold-start tests pass including the new one (0.99s — liveness sleep is no-op in tests)
95 test_tmux_session tests pass
208 tests pass across test_tmux_session / test_agent_status / test_tmux_transcript / test_transport_state
Ruff clean

Closes #513.

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bradbrok · 2026-05-19T18:20:30Z

Heartbeat maintenance: this branch was 16 commits behind main (dirty/conflicting). Rebased onto current main and resolved the single conflict in tmux_session.py — both sides added code after the cold-start timeout block; resolution keeps the liveness check from this PR followed by the force_fresh_context_once NOTE added in #545.

Rebased branch: fix/tmux-spawn-liveness-check-rebase — 140 tmux tests pass (including the new test_cold_start_session_dies_immediately_drives_to_dead). Ready to force-push to this branch and merge if approved.

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bradbrok · 2026-05-21T12:25:42Z

Heartbeat maintenance: previous rebase branch (fix/tmux-spawn-liveness-check-rebase) was 4 commits behind main due to #560, #563, #565 landing since last heartbeat. Re-rebased cleanly onto current main (8e20de0) — no conflicts in tmux_session.py.

Fresh branch: fix/tmux-spawn-liveness-check-rebase2 — 168 tmux tests pass (including test_cold_start_session_dies_immediately_drives_to_dead), full suite 2602 passed / 1 skipped.

Ready to force-push to fix/tmux-spawn-liveness-check and merge if approved.

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bradbrok · 2026-05-24T10:22:59Z

Heartbeat maintenance: fix/tmux-spawn-liveness-check-rebase2 was 13 commits behind main (#571–#584 landed since last heartbeat). Rebased cleanly onto current main (0b962d5) — no conflicts.

Fresh branch: fix/tmux-spawn-liveness-check-rebase3 — 225 tmux tests pass (test_tmux_session + test_tmux_transcript, including test_cold_start_session_dies_immediately_drives_to_dead); full suite 2432 passed / 1 skipped.

Ready to force-push to fix/tmux-spawn-liveness-check and merge if approved.

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bradbrok · 2026-05-25T04:19:07Z

Heartbeat maintenance: fix/tmux-spawn-liveness-check-rebase3 was 1 commit behind main (#585 landed since last heartbeat). Cherry-picked cleanly onto current main (3d8d9a5) — no conflicts.

Fresh branch: fix/tmux-spawn-liveness-check-rebase4 — 237 tmux tests pass (test_tmux_session + test_tmux_transcript, including test_cold_start_session_dies_immediately_drives_to_dead).

Ready to force-push to fix/tmux-spawn-liveness-check and merge if approved.

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bradbrok · 2026-05-27T14:13:26Z

Heartbeat maintenance (2026-05-27): rebased onto current main (3c358a1 — includes #585–#600, 9 commits since last heartbeat rebase).

Cherry-picked cleanly — no conflicts in tmux_session.py or test_tmux_session.py. Force-pushed to fix/tmux-spawn-liveness-check.

Tests: 298 passed (test_tmux_session + test_tmux_transcript + test_transport_state), including test_cold_start_session_dies_immediately_drives_to_dead. CI will run now.

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bradbrok · 2026-05-28T14:07:42Z

Heartbeat maintenance (2026-05-28): rebased onto current main (8978dfb — 1 commit since last heartbeat rebase: phantom-drain fix #595).

Rebased cleanly — no conflicts in tmux_session.py or test_tmux_session.py. Force-pushed to fix/tmux-spawn-liveness-check.

Tests: 303 passed (test_tmux_session + test_tmux_transcript + test_transport_state), including test_cold_start_session_dies_immediately_drives_to_dead. CI will run now.

🤖 Heartbeat maintenance

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) tmux new-session returns 0 as long as the child shell + command launched. If the in-pane command exits immediately (bad flag, auth error, missing binary, etc.) the detached session reaps itself silently and the state machine ends up CONNECTED against nothing, queuing messages forever. Adds a ~150ms window + has_session() check after new_session() succeeds in _spawn_tmux_repl(). A dead session at that point raises RuntimeError so the existing BOOTING → DEAD via BOOT_FAILED transition fires correctly. The delay is tunable via _SPAWN_LIVENESS_DELAY_SEC (patched to 0 in tests). Also updates _make_mock_tmux() to return True for post-spawn liveness checks while keeping the pre-spawn stale-detection call returning has_session_initial (uses itertools.chain for precise call sequencing). 95 tmux_session tests pass; 208 across the tmux/agent_status/transport suite. Closes #513.

bradbrok · 2026-05-31T14:13:37Z

Heartbeat maintenance (2026-05-31): rebased onto current main (ec39201 — 9 commits since last heartbeat rebase on 8978dfb, including isolation_mode/provisioning seam, per-agent signing key fix, CommandRunner/UnixUserProvisioner, live token analytics, and ultracode effort tier). Rebased cleanly — no conflicts in tmux_session.py or test_tmux_session.py. Force-pushed to fix/tmux-spawn-liveness-check.

Tests: 332 passed (test_tmux_session + test_tmux_transcript + test_transport_state), including test_cold_start_session_dies_immediately_drives_to_dead. CI will run now.

🤖 Heartbeat maintenance

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bradbrok force-pushed the fix/tmux-spawn-liveness-check branch from 0e0f0c6 to 0bdec9c Compare May 20, 2026 10:17

bradbrok force-pushed the fix/tmux-spawn-liveness-check branch from 0bdec9c to c0595b0 Compare May 27, 2026 14:13

bradbrok force-pushed the fix/tmux-spawn-liveness-check branch from c0595b0 to 8a65331 Compare May 28, 2026 14:07

bradbrok force-pushed the fix/tmux-spawn-liveness-check branch from 8a65331 to 9be6412 Compare May 31, 2026 14:13

This was referenced Jun 10, 2026

fix(sweep): tmux - delivery retries, REPL death detection, transcript swap race #713

Merged

Reconcile PRs #531 and #612 — identical _verify_repl_survived_launch diff, both need a rebase after #713 #729

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fix(tmux): post-spawn liveness check for silent in-pane exit (issue #513) - #531

fix(tmux): post-spawn liveness check for silent in-pane exit (issue #513)#531
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bradbrok commented May 18, 2026

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