fix(host): read a terminal session next to the destroy marker as destroyed by ThomasK33 · Pull Request #284 · coder/agent-tty

ThomasK33 · 2026-11-03T08:57:50Z

Why

ThomasK33 asked to work every deferred follow-up of the first autopilot round until none is left. This PR closes #265, the follow-ups after #256. Since #256, recordDestroyed writes an empty <session>/destroyed marker before its destroyed write, and a reconcile that wrote over that record writes destroyed again right after its own write. Three gaps stayed open, and all three reproduce on main 71d1b0c2:

A killed reconcile leaves failed. A reconcile killed between its own write and the repair write left failed, after destroy --force had printed destroyed: true. Every later reconcile skipped the terminal manifest, so the session stayed failed.
The reader window. A reader between those two writes saw failed, and scanHome counted the session. home list --all and the dashboard picker then showed one extra session, and after a killed reconcile they kept showing it.
A stale marker after a failed destroy. A destroy of an ended session that failed after its marker write left the marker next to exited or failed, and nothing repaired it.

What changed

src/host/lifecycle.ts
- reconcileSession first checks a terminal manifest other than destroyed for the marker. If the marker is there, writeMarkedDestroyed writes destroyed from that copy, with hostPid and childPid null, the exit code kept and no failure fields. The reconcile then unlinks the socket, which a destroy whose write failed left, removes the empty Home socket folder and returns. Only a destroy writes the marker, after it stopped the session and right before its destroyed write, so the marker means that destroy chose destroyed.
- listSessions reconciled only active sessions. It now also reconciles a terminal session that is not destroyed when the marker exists, so list heals items 1 and 3 itself. When that repair throws, list reads the manifest again and shows it: destroyed when only the socket cleanup after the write failed, and the copy it read before when the write itself failed, for example on a full disk, as before this PR.
- inspect calls reconcileSession when the stored record is terminal, not destroyed, and has the marker, so inspect shows destroyed as list does. A running session with a live host and the marker stays running: the marker repairs only an ended session.
src/storage/homeScope.ts. scanHome skips a session whose folder holds the marker when its status is terminal, the same rule as the repair. It asks its ScanHomeDependencies.pathExists for the marker. home list and the dashboard picker stay read-only and no longer count such a session.
The lifecycle check gets a new guard, ReconcileRepairsMarked.
- The model writes destroyed at the reconcile's first read when the marker is next to a terminal manifest other than destroyed.
- facts.mjs reads the guard, and writeMarkedDestroyed is covered.
- The new witness WitnessMarkedRepaired shows that the branch is reachable: one reconcile's first read repairs the failed that the other reconcile wrote.
- mutant-ReconcileRepairsMarked expects pass. The model has no crash of a reconciling process, so the repair after the reconcile's own write always runs there. The unit tests cover the crash. SKILL.md says so.
docs/USAGE.md, src/host/README.md, src/storage/README.md, src/dashboard/README.md and src/cli/commands/home/README.md describe the repair, which commands run it (list, inspect, gc) and the home list count.

Declined, as approved by the root: deleting the marker (item 4). A reconcile that read before a destroy's write can still write after it, and no process knows when the last such reconcile has finished. So deleting the marker would reopen the #217 race. The marker is one empty file, and gc removes it with the session folder.

Behavior changes for CLI and JSON users

No JSON shape, error code or exit code changes.
A session that a destroy marked reads destroyed after the next list, also when a reconcile was killed in the middle or when that destroy failed after its marker write. Before, such a session stayed failed or exited. gc repairs it too before it removes the folder.
home list and the dashboard picker no longer count such a session.

Validation

Red first. At 35bce9d8 (tests only), 3 tests failed: the two reconcileSession repair tests and the scanHome marker test. The control test (an exited session without the marker stays exited) passed. At 7ddc041e, the list test failed. All pass on the head.

Live repro with the CLI, a killed host and a held rename (REPLAY_HOLD), each run in an isolated AGENT_TTY_HOME and XDG_STATE_HOME:

Item	main `71d1b0c2`	head `aea5277e`
1. `destroy --force` prints `destroyed: true`, then the reconcile is killed before its repair write. The next `list` shows	`failed`	`destroyed`
2. `home list --all` while the repair write is held	`{"activeSessions":0,"totalSessions":1}`	home not listed (no visible session)
3. `destroy` of an `exited` session fails after the marker (`STORAGE_WRITE_ERROR`). The next `list` shows	`exited`	`destroyed`

Lifecycle check (.agents/skills/verify-session-lifecycle/scripts/check.sh --update-coverage): all 66 runs as expected. current explored 24,208,708 distinct states, current-no-token 23,413,352. WitnessMarkedRepaired is reached. coverage.json is synced at cb4b7f83.
CI-shaped gate on aea5277e: typecheck, lint and format pass. Unit 1736/1736. Integration shards 2 and 4 and e2e shards 1 and 3 pass. Three files failed under the 7 parallel shards and pass alone on the head: backend-selection.test.ts and export-fixtures.test.ts (12/12 together), and run.test.ts (14/14, plus 3/3 runs of detects session exit during wait before timing out). backend-selection and the export-fixtures color-grid test fail the same way on main under that load.
Round 2 (Codex round 1 on aea5277e): red 2c47894e (2 tests failed: the marked repair left the socket, and list --all dropped a marked failed session whose repair write failed), fix 8a6695fd, model c5482b20 (the repair goes on to the socket unlink), facts.mjs d875e821 (the guard pattern includes the unlink), coverage cb4b7f83. Unit tests of src/host, src/storage and the commands: 368/368. Alone on d875e821: lifecycle.test.ts 58/58, non-reaping-init.test.ts 3/3, socket-directory.test.ts 9/9. A full local gate on d875e821 ran at host load 130 to 180 and timed out in files that this change does not reach, so CI on the head is the full gate.
Round 3 (Codex round 2 on cb4b7f83): red 749795da (list showed failed when the socket cleanup threw after the repair write), fix e845dd71. Unit 1739/1739. facts.mjs drift 0, so check.sh did not run again.
Round 4 (Codex round 3 on e845dd71, plus the root verifier notes N1 to N3): red 35ae60d5 (inspect left a marked failed session failed, and scanHome read the marker from the real filesystem), fix 18336a12. Model b8b8dbb4 splits the marked repair into its read ("r_marked") and its write (ReconcileWritesMarked). b23d1214 pins the terminal-status rule (a running session with a live host and the marker stays running; I checked that the test fails without the rule) and adds a red test for scanHome, fixed in 6e0a595c. Docs b08dad39. Coverage ad17bf61. Lifecycle check: all 66 runs as expected, current explored 24,866,000 distinct states, current-no-token 24,005,824. Unit 1743/1743. lifecycle integration 58/58 and cli integration 65/65.
Round 5 (Codex round 4 on ad17bf61, security clean): red d22e3df4 (inspect failed when the marked repair threw, though list showed the session), fix 61e81f1c (inspect reads the manifest again, as list does). Docs eaae86e0 (the scanHome README line says "ended", USAGE and the commands README name the inspect fallback). facts.mjs drift 0, so check.sh did not run again. Unit 1745/1745. lifecycle and cli integration 123/123. Typecheck, lint and format pass.
Merge of main 307c0e99 (f7aad5b8, counts 3868d3b0), no Codex round. Codex round 5 on eaae86e0 was clean in both lanes. Main's fix(host): freeze a program group that no scan shows before the proven kill #283 changed the model, check.sh, facts.mjs and SKILL.md, and so did this PR. Conflicts: the guard list in SessionLifecycle.tla (both new guards kept), the run list in check.sh, two SKILL.md hunks and two src/host/README.md hunks (merged word by word), and coverage.json (rewritten by check.sh --update-coverage). check.sh on the merge: all 68 runs as expected, current 24,866,000 distinct states and current-no-token 24,005,824. SKILL.md now counts 68 runs and thirty guards. Unit 1888/1888. lifecycle and cli integration 138/138. Typecheck, lint and format pass.
Merge of main 142f7793 (fix(host): keep sockets under a per-uid root and remove a dead host socket #288, 2371636a) and two follow-ups from the root's advisor (90480ffa head). Conflicts: the SKILL.md Scope line (only the state counts, now from this run), a USAGE hunk (merged word by word) and coverage.json. Follow-up 1: removeDeadHostSocket returns when the host check throws, so it removes neither socket of a host it cannot judge (red 7e259ab7: destroy removed the old socket under /tmp/agent-tty when process.kill(pid, 0) threw EINVAL; fix 30c71732). Follow-up 2: USAGE limit 2 names umask 002, under which an older version made /tmp/agent-tty mode 0775, which the old-socket check refuses until chmod g-w (f452642d, with the host README). check.sh on the head: all 68 runs as expected, current 25,534,376 distinct states and current-no-token 24,675,744 (SKILL.md updated). facts.mjs drift 0. Unit 1922/1922. lifecycle, cli, socket-directory and socket-permissions integration 153/153. Typecheck, lint and format pass.
Merge of main 374937f9 (fix(host): read a group out of the CLI's pid space as running #291, fix(release): raise the Communique response token limit so release notes are not cut off #295; merge 8b2863b2, coverage 91d7f744), no Codex round (root's GO for a merge-only delta). Conflicts: the check.sh run list and a src/host/README.md hunk (merged word by word and checked against both sides), the SKILL.md counts (now 71 runs, CHECK_JOBS=71, eight runs that explore the whole model, thirty-one guards) and coverage.json. check.sh on the merge: all 71 runs as expected, current 25,534,376 distinct states and current-no-token 24,675,744. facts.mjs drift 0. Unit 1929/1929. lifecycle, cli and socket-directory integration 153/153. Typecheck, lint and format pass.
Deferred to the root's parking issue: Codex round 6's P2 (the marked repair unlinks only the current socket, not the old /tmp/agent-tty one).

Closes #265

Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: xhigh

…royed

…oncile read

…ist count

…arker

…marker

…pair

…tness

ThomasK33 · 2026-11-03T08:58:28Z

@codex review

ThomasK33 · 2026-11-03T08:58:29Z

@codex security review

chatgpt-codex-connector · 2026-11-03T08:58:45Z

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-11-03T17:53:03.981918Z	`90480ff`	Manual request
🔒 Security Review	✅ Completed 2026-11-03T17:52:22.659441Z	`90480ff`	Manual request

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…the session when the repair fails

… session whose repair fails

…link

ThomasK33 · 2026-11-03T11:46:57Z

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…pair write

…er its write

ThomasK33 · 2026-11-03T11:56:28Z

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…throws

…its output when the repair fails

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Codex Review: Didn't find any major issues. Can't wait for the next one!

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# Conflicts: # .agents/skills/verify-session-lifecycle/SKILL.md # .agents/skills/verify-session-lifecycle/coverage.json # .agents/skills/verify-session-lifecycle/model/SessionLifecycle.tla # .agents/skills/verify-session-lifecycle/scripts/check.sh # src/host/README.md

…main

# Conflicts: # .agents/skills/verify-session-lifecycle/SKILL.md # .agents/skills/verify-session-lifecycle/coverage.json # docs/USAGE.md

…t throws

…ckets when the host check throws

…main and the socket check fix

ThomasK33 · 2026-11-03T17:48:53Z

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# Conflicts: # .agents/skills/verify-session-lifecycle/SKILL.md # .agents/skills/verify-session-lifecycle/coverage.json # .agents/skills/verify-session-lifecycle/scripts/check.sh # src/host/README.md

…main

ThomasK33 added 11 commits November 3, 2026 06:46

test: a destroy marker makes a terminal session read destroyed

35bce9d

fix(host): read a terminal session next to the destroy marker as dest…

1352963

…royed

fix(skills): model the repair of a marked terminal session at the rec…

519ea8a

…oncile read

docs: describe the repair of a marked terminal session and the home l…

ac2e5bf

…ist count

test: list shows destroyed for a failed session next to the destroy m…

7ddc041

…arker

fix(host): let list reconcile a terminal session next to the destroy …

963e45c

…marker

chore(skills): sync the lifecycle coverage record after the marked re…

e274c6a

…pair

chore: trim comments in the marked repair

64b1092

refactor(host): name the marked terminal check isMarkedDestroyed

cd9af9c

fix(skills): witness the repair at the reconcile read with a ghost

7f3765d

chore(skills): sync the lifecycle coverage record after the repair wi…

aea5277

…tness

chatgpt-codex-connector Bot reviewed Nov 3, 2026

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Comment thread src/host/lifecycle.ts Resolved

Comment thread src/host/lifecycle.ts Resolved

ThomasK33 added 5 commits November 3, 2026 09:32

test: a marked repair removes the dead host's socket, and list keeps …

2c47894

…the session when the repair fails

fix(host): unlink the socket after a marked repair, and list a marked…

8a6695f

… session whose repair fails

fix(skills): the marked repair goes on to the socket unlink

c5482b2

fix(skills): read the marked repair with its socket unlink

d875e82

chore(skills): sync the lifecycle coverage record after the repair un…

cb4b7f8

…link

chatgpt-codex-connector Bot reviewed Nov 3, 2026

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Comment thread src/host/lifecycle.ts Resolved

ThomasK33 added 2 commits November 3, 2026 11:54

test: list shows destroyed when the socket cleanup fails after the re…

749795d

…pair write

fix(host): list re-reads the manifest when a marked repair throws aft…

e845dd7

…er its write

ThomasK33 added 3 commits November 3, 2026 15:07

test: inspect shows a marked session as it reads when its repair throws

d22e3df

fix(cli): inspect shows a marked session as it reads when its repair …

61e81f1

…throws

docs: scanHome skips only an ended marked session, and inspect keeps …

eaae86e

…its output when the repair fails

ThomasK33 added 7 commits November 3, 2026 15:46

docs(skills): count the 68 runs and thirty guards after the merge of …

3868d3b

…main

Merge remote-tracking branch 'origin/main' into fix/265-marker-repair

2371636

# Conflicts: # .agents/skills/verify-session-lifecycle/SKILL.md # .agents/skills/verify-session-lifecycle/coverage.json # docs/USAGE.md

test: destroy keeps the old socket when the host check throws

7e259ab

fix(host): keep both sockets when the host check of a dead-host socke…

30c7173

…t throws

docs: name the umask 002 case of the old socket root, and the kept so…

f452642

…ckets when the host check throws

chore(skills): sync the lifecycle coverage record after the merge of …

90480ff

…main and the socket check fix

chatgpt-codex-connector Bot reviewed Nov 3, 2026

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Comment thread src/host/lifecycle.ts Resolved

ThomasK33 added 2 commits November 3, 2026 18:38

Merge remote-tracking branch 'origin/main' into fix/265-marker-repair

8b2863b

# Conflicts: # .agents/skills/verify-session-lifecycle/SKILL.md # .agents/skills/verify-session-lifecycle/coverage.json # .agents/skills/verify-session-lifecycle/scripts/check.sh # src/host/README.md

chore(skills): sync the lifecycle coverage record after the merge of …

91d7f74

…main

ThomasK33 added this pull request to the merge queue Nov 3, 2026

Merged via the queue into main with commit 0024ddf Nov 3, 2026
14 checks passed

ThomasK33 deleted the fix/265-marker-repair branch November 3, 2026 20:42

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chore(release): 0.6.0 #172

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