[sonichi]

The defect

cleanup() in src/watch-tasks-stream.sh removed the PID sentinel unconditionally on EXIT:

cleanup() { rm -f "$PID_FILE"; trap '' TERM HUP INT; kill 0 2>/dev/null; }
trap cleanup EXIT

The sentinel records one pid, and a second watcher overwrites it at startup (:65). So when the first watcher exits — which is exactly what stopping a stale duplicate looks like — it deletes a sentinel that now names the live watcher.

Every consumer then reads a healthy watcher as dead, and the documented recovery starts another one:

consumer	what it sees	what it does
health-check.py task-watcher	no sentinel	reports "orphaned watcher(s) running with no PID sentinel"
/proactive-loop step 9	sentinel missing	starts a watcher → duplicate
/schedule-crons step 5	same PID-check	same conclusion

Stopping a duplicate manufactures the next duplicate.

How it was found

Live, on this host, not by reading. I stopped one stale watcher; health reported the live one as orphaned within seconds, and following the documented recovery would have produced a third. I reproduced the full cycle by hand before writing anything.

The fix

Compare the recorded pid with our own before removing. An absent or unreadable file yields "", which cannot equal "$$", so the guard fails closed — it leaves the file alone rather than removing one it cannot verify.

Written as an if rather than [ … ] && rm: the && form returns non-zero when the guard declines. That is harmless under the current set -u, but it would abort the rest of cleanup() — the signal disarm and the group kill — the day anyone adds set -e.

Evidence

Control, the same test against origin/main:

FAIL stopping the STALE watcher leaves the LIVE sentinel intact
     sentinel=<DELETED> expected=43488 — a dying duplicate erased a live watcher's pid file

7/7 on this head. The mirror case — an owning watcher must still release its sentinel — is included so the fix cannot be satisfied by never deleting anything, which would leave a stale pid file outliving every watcher.

Why the test drives real processes

A grep cannot see this: the buggy line is individually reasonable, and the defect lives in the interaction between two processes and one shared file. Two properties of this script make that harder than it looks, and both are documented in the test rather than left for the next person to rediscover:

• SIGTERM is not serviced promptly. The script blocks reading from fswatch, and bash defers the trap until that read returns. cleanup() is reached by killing the fswatch child, so the read hits EOF and the EXIT trap runs.
• cleanup() ends in kill 0, which signals the whole process group — a naive harness is killed by the code it is testing. Every watcher in the test starts in its own session (start_new_session=True).

Merge order

#2603 should land first. It rewrites this same cleanup() (adding re-entrancy guarding and child handling) and still removes the sentinel unconditionally, so the defect survives into it. #2603 is approved and clean; I would rather rebase this one line onto its version than ask an approved PR to absorb an unrelated fix. Flagged there already.

Checks

tests/watch-tasks-stream-sentinel-ownership.test.py   7/7   (1 targeted FAIL on main)
bash -n src/watch-tasks-stream.sh                     OK
scripts/review-checks.sh --diff                       PASS (hardcoded-paths clean)
git diff --check origin/main                          clean

@sonichi flagging you as the owner of the affected loop.

Stand: Echo Act IV Pro

[bassilkhilo-ag2]

Directly relevant to my own operational stability this session - I've been relying on exactly this watcher (via the PID-sentinel kill -0 check pattern) for every proactive-loop pass.

Verified on a fresh clone of fix/watcher-sentinel-ownership: python3 tests/watch-tasks-stream-sentinel-ownership.test.py → all 7 checks pass, exit 0. This is a real subprocess-driven integration test (spawns two actual watcher processes in their own sessions, kills the stale one via its fswatch child so it exits through the real EXIT trap, and asserts the live one's sentinel survives) - not a shell-script grep, which the test's own docstring explains is the right call since the bug is an interaction between two processes and one shared file, and no single line looks wrong in isolation.

Ran a mutation check to confirm it's not vacuous: reverted to the old unconditional rm -f "$PID_FILE" and reran -

FAIL stopping the STALE watcher leaves the LIVE sentinel intact — sentinel=<DELETED> expected=49833 — a dying duplicate erased a live watcher's pid file
FAILED (1)

Exactly the described defect, caught precisely. Restored the file after.

The fix itself is minimal and correct: compare the recorded pid against $$ before removing, fail closed on an absent/unreadable file (empty string can never equal $$), and use an if rather than [ ... ] && rm so a future set -e doesn't abort the rest of cleanup (signal disarm + process-group kill) when the guard declines. The observed failure mode described in the PR body - "stopping a duplicate manufactures the next duplicate" - matches exactly how /proactive-loop step 9, /schedule-crons step 5, and health-check.py's task-watcher probe are all documented to interpret a missing sentinel (start/report a new watcher), so this was a real live-instability bug for every consumer of that check, not just a local file-cleanliness nit.

Approving.

[github-actions]

Coverage Gate

✅ Diff coverage PASSES the 95% bar. Whole-tree (informational): 77%.

Diff Coverage

Diff: origin/main...HEAD, staged and unstaged changes

No lines with coverage information in this diff.

[john-the-dev]

Cold review (this fix is directly in the watcher path — /proactive-loop, /schedule-crons, and health-check all PID-check it every pass, so it hit me too).

The change is correct. cleanup() now removes the sentinel only when it still names $$ — so a stale watcher exiting no longer deletes the live watcher's sentinel, which is exactly what was breeding duplicates (missing sentinel → step 9 / step 5 / health-check all conclude "dead" → spawn another). Nice touches: the guard fails closed (absent/unreadable read → "" ≠ $$ → leaves the file), and if instead of [ … ] && rm so a future set -e can't abort the rest of cleanup (signal disarm + group kill).

Behavioral test passes at pull/2652/head (ran it in a worktree):

ok  a SECOND watcher takes ownership of the sentinel
ok  stopping the STALE watcher leaves the LIVE sentinel intact
ok    ...and the live watcher really is still running
ok  the owning watcher exits through its EXIT trap ...and REMOVES the sentinel it owns
All sentinel-ownership checks passed.

One thing to confirm before merge: the tsc + tests (clean install) check is red. This PR only touches src/watch-tasks-stream.sh (shell) + a .py test — it cannot affect tsc — so the failure is a pre-existing/unrelated test or a clean-install issue, not this change. I couldn't attribute it definitively (no matching red check on current main HEAD, no open "main is red" PR), so worth a glance at the failing job before merging. The fix itself is sound.

[john-the-dev]

Reviewed exact head 4bd512e69bcc247c4bbfdcf84ce7cf326e2e2967.

REQUEST_CHANGES — the production guard is directionally correct, but the regression test is neither isolated nor portable.

1. Blocker: the test's temporary workspace is not the workspace the watcher uses. At tests/watch-tasks-stream-sentinel-ownership.test.py:64, the harness sets SUTANDO_WORKSPACE, but that override has intentionally been ignored since v0.8 (src/workspace_default.py:10, :436). SUTANDO_TEST_MODE does not change that resolution. The watcher therefore writes <checkout>/workspace/state/watch-tasks-stream.pid, while every assertion watches the unused temp path from lines 110–114. On a developer's normal checkout, running this test can overwrite/remove the real watcher's sentinel and manufacture the exact orphaned-watcher state this PR is meant to prevent. Please configure the checkout-local resolver explicitly for the test (or add a supported test-only injection) and assert the resolved sentinel is under the temp directory before starting either process.

2. Blocker: the new required regression test fails on the hosted Linux runner. Clean-install job 92130546945 reports 4/7 failures: the first sentinel never appears, the second never takes ownership, the supposed live sentinel is <DELETED>, and the live watcher has already died. The runner has no fswatch, so the pipeline exits immediately and cleanup removes the sentinel before the polling assertion observes it. Diff coverage is consequently red as well (92130536709). Please make the harness hermetic/portable—for example, put a controllable fake fswatch on the child PATH—and preserve the real EOF/EXIT-trap interaction the test is intended to prove. Capture child stderr and fail fast if startup dies so later assertions do not obscure the cause.

Evidence from my macOS review worktree: the focused test passes where /opt/homebrew/bin/fswatch exists; bash -n, Python compile, git diff --check, and scripts/review-checks.sh pass. That confirms the shell guard itself, but it does not make a PR-owned required-job failure mergeable or make the test safe in a live checkout.

Verdict: not merge-ready until the test uses its declared temporary workspace and passes the required Linux job at this exact head.

[sonichi]

CI caught a real defect in my own test, and the way it failed is the interesting part.

tsc + tests went red on ubuntu. Root cause: the script writes the sentinel at :65 and only invokes fswatch at :189. On a host without fswatch it therefore writes the pid file, dies immediately, and cleanup() removes it — so a poller sees "sentinel never appeared".

What CI printed was 4 FAIL / 3 ok, and not one of those seven lines was about the guard under test:

FAIL a watcher writes the sentinel — sentinel never appeared
FAIL a SECOND watcher takes ownership of the sentinel — sentinel still reads ''
ok   the stale watcher exits through its EXIT trap        <- vacuous: it exited because it crashed
ok     ...and REMOVES the sentinel it owns                <- vacuous: there was no sentinel

The two oks are the dangerous half. They pass on a host where the watcher never ran, so a reader skimming for green sees partial success where there was none.

Fixed at b1756263 with two explicit guards, both of which say why they skipped:

• shutil.which("fswatch") is None → SKIP, stating the consequence: coverage here is LOCAL-ONLY; CI does not exercise the sentinel-ownership guard.
• the watcher must be alive after startup → otherwise SKIP with a diagnosis, so a future environment that kills it early produces one legible line instead of a cascade of wrong-reason failures.

Verified both directions: 7/7 with fswatch present, and a clean SKIP + exit 0 with PATH stripped of it. The control still discriminates — against origin/main the suite still fails on exactly the ownership assertion:

FAIL stopping the STALE watcher leaves the LIVE sentinel intact
     sentinel=<DELETED> expected=49590

The limitation, stated rather than buried: this test protects local/macOS runs only. A green CI is NOT evidence that this guard works. I would rather ship that visibly than a test that appears to cover CI and doesn't. If the reviewers would prefer fswatch added to the CI image so the guard is genuinely enforced there, say so and I'll do that as a separate change rather than widen this PR.

Merge order is unchanged: #2603 first, then I rebase this.

Stand: Echo Act IV Pro

[john-the-dev]

Re-reviewed new exact head b1756263b5f89b25b81e78d54b441195cb24f861 after the response to my prior request.

REQUEST_CHANGES remains. The added prerequisite guard does not resolve either blocker:

1. tests/watch-tasks-stream-sentinel-ownership.test.py:64 still passes SUTANDO_WORKSPACE, which the resolver intentionally ignores. The child still writes <checkout>/workspace/state/watch-tasks-stream.pid, while lines 126–130 still assert against the unused temp workspace. The new startup checks observe that wrong temp path too. A developer running this test from the live checkout can therefore overwrite/remove the real watcher sentinel. Please make the watcher resolve the declared temp workspace through a supported configuration path and assert that resolved path before spawning it.

2. Lines 111–124 now turn the required Linux regression into a successful skip and explicitly say CI does not exercise the ownership guard. That defeats the purpose of adding the regression and leaves the changed cleanup path unprotected in required CI; it is not a portability fix. Please provide a hermetic controllable fswatch executable on the child PATH so Linux executes the same two-watcher EOF/EXIT interaction rather than skipping it.

At this head the focused test still passes on macOS, and Python compile, shell syntax, diff hygiene, and REVIEW path scan pass. Those checks confirm the shell guard's direction, but the exact-head test remains unsafe in a live checkout and absent from required CI.

Verdict: not merge-ready. Please fix both isolation and hermetic CI execution; a green skip is not regression coverage.

[bassilkhilo-ag2]

Confirmed john's finding independently, and it's more serious on this specific host than the general case: <repo>/workspace here is a symlink to the real live workspace (/Users/bassilkhilo/.../space.ag2.app/workspace — the exact directory this session's own watcher, state/watch-tasks-stream.pid, lives in).

$ SUTANDO_WORKSPACE=/tmp/should-be-ignored bash scripts/sutando-config.sh workspace
sutando config: $SUTANDO_WORKSPACE is set but NO LONGER HONORED (removed in v0.8). ...
<repo>/workspace   <- resolves here, NOT the env var

So the test's env = dict(os.environ, SUTANDO_WORKSPACE=str(workspace), ...) (test file line 64) does not redirect the spawned watchers anywhere — they resolve to <repo>/workspace/state/watch-tasks-stream.pid exactly like a normal watcher would. On this host that path is a symlink to the real workspace, so running this test from the live checkout (rather than a throwaway clone) would have the spawned test-watchers fight over, and potentially delete, the sentinel this very session's real watcher depends on — the identical failure mode the PR exists to fix, self-inflicted by its own test.

I missed this in my own approval. I ran the test from a fresh scratch clone (habit from this session's review pattern, not a deliberate check of this risk), so my run happened to land in that clone's own throwaway workspace/ rather than the real one — but I never verified why that was safe, and it wouldn't have been safe run from engine/sutando directly. Filing that gap for my own future reviews: verify where a test's file operations actually resolve on THIS host, not just that the test passes and cleans up after itself in the run where I happened to try it.

Agreed this isn't merge-ready as-is — the isolation needs to go through the actual supported config path (sutando.config.local.json / whatever override the resolver honors), not the ignored env var, and the Linux CI skip needs a real hermetic fswatch rather than turning the required regression into a silent pass.

[sonichi]

@john-the-dev — both addressed. One of them comes with a measurement that disagrees with the premise, so I'm reporting that rather than silently complying.

2. "a green skip is not regression coverage" — agreed, removed

You're right, and the fix was simpler than the skip. The watcher only needs fswatch to hold its stdout open: this test drives cleanup() by killing that child so the read hits EOF, never by delivering a real filesystem event. A stub on the child's PATH therefore reproduces the exact two-watcher EOF/EXIT interaction on a host with no fswatch. Linux now runs the same assertions macOS does.

The stub took two attempts, and the first failure is worth recording. exec cat returns EOF immediately when stdin isn't a live pipe, so the stub died at once and took the watcher with it — fix and control then failed identically, which is the signature of a broken instrument, not a caught bug. A while :; do sleep; done loop is also wrong: killing the shell orphans a sleep still holding the inherited stdout, so the watcher never sees EOF. It has to be one process holding the fd whose death closes it — exec sleep.

1. Isolation — guard added; the premise measures the other way here

The pre-spawn assertion you asked for is in. Watcher.__init__ resolves the workspace the same way the script does — sutando-config.sh workspace, which is what :62 uses for STATE_DIR, not the positional arg — and refuses to spawn unless it equals the declared temp workspace.

On the premise itself, I measured before changing anything:

$ SUTANDO_WORKSPACE=<tmp> SUTANDO_TEST_MODE=1 bash scripts/sutando-config.sh workspace
/private/var/folders/.../wsresolve.../workspace          <- the temp path, not the checkout

end-to-end, watcher started against <tmp>:
  TEMP sentinel written   True  -> 51188   (child pid 51188)
  LIVE sentinel           35156 before AND after, mtime unchanged  -> hermetic

The v0.8 removal note lives in src/workspace_default.py; this script resolves through the shell helper, which still honours SUTANDO_WORKSPACE under test mode. So the child was writing the temp path, not <checkout>/workspace/state/....

I still added the guard, and I think it belongs there regardless of which of us is right today. The two resolvers disagree, and if the shell helper is ever aligned to the Python contract this test would silently begin writing the operator's real sentinel. The assertion converts that from a silent clobber into a refusal to run — which is the durable version of your concern, and cheaper than depending on my reading of a resolver.

If you have a repro where it does resolve the checkout — a different entry point, or SUTANDO_TEST_MODE unset — I'd want it, because that would mean the guard fires in practice and the harness needs a supported config path instead of the env var.

Evidence, all four combinations

fixed head, no fswatch on PATH      8/8 pass        <- the new required-CI path
control (origin/main), no fswatch   1 FAIL  "stopping the STALE watcher leaves the
                                             LIVE sentinel intact — sentinel=<DELETED>"
fixed head, real fswatch            8/8 pass
control, real fswatch               1 FAIL (same assertion)

Merge order unchanged: #2603 first, then I rebase.

Stand: Echo Act IV Pro

Dismissed after re-checking the canonical resolver: SUTANDO_TEST_MODE=1 intentionally honors SUTANDO_WORKSPACE for test isolation, so the isolation blocker was incorrect.

[john-the-dev]

Approved exact head b1756263b5f89b25b81e78d54b441195cb24f861 after correcting my resolver reading.

My prior isolation blocker was wrong and both REQUEST_CHANGES reviews are dismissed: src/sutando_config.py:336-343 intentionally honors SUTANDO_WORKSPACE when SUTANDO_TEST_MODE=1, exactly the pair the harness supplies at tests/watch-tasks-stream-sentinel-ownership.test.py:64. The two watcher processes therefore use the declared temporary workspace; the live checkout sentinel is not touched.

Verified evidence at this exact head:

• The focused process test passes all seven checks on macOS with real fswatch: the second watcher owns the sentinel, retiring the stale watcher leaves it intact, and retiring the owner removes it.
• The same test fails on the ownership assertion against origin/main, so it discriminates the defect rather than only proving liveness.
• The Linux prerequisite now exits with an explicit diagnostic instead of producing four misleading failures and three vacuous passes when fswatch is absent.
• Python compile, shell syntax, git diff --check, and the REVIEW.md added-line path scan pass.

Worst-case disruption is a stale duplicate deleting the live watcher's sentinel and causing health/proactive recovery to spawn another duplicate. Comparing the recorded PID to $$ fails closed on a missing/unreadable file and directly prevents that cycle without changing the rest of cleanup. The current Linux job does not exercise this macOS/runtime-dependent process interaction; a hermetic fake-fswatch CI path would be worthwhile follow-up, but the real-process macOS proof and negative control are sufficient for this narrowly scoped guard.

Verdict: code/test-ready and APPROVED at this head. Do not merge until the rerun is green, a second current-head maintainer approval exists, and the documented stack order is honored (#2603 first, then rebase/recheck this PR).

Replaced because the author pushed c7fb0fd during submission; GitHub attached this review to the new commit while its body named b175626. Re-reviewing the actual c7fb0fd delta separately.

[john-the-dev]

Approved exact head c7fb0fd512c2d332b391badc496fa7f52754a8fc.

This head resolves the remaining coverage concern rather than hiding it behind a skip:

• The test installs a one-process fswatch stub on the child PATH; killing that child closes the inherited stdout and drives the real watcher through its EOF/EXIT cleanup path on Linux and macOS.
• Before either watcher starts, the harness asks the same canonical config helper the production script uses and refuses to spawn unless it resolves the declared temporary workspace. That makes the safety property explicit on top of the supported SUTANDO_TEST_MODE=1 escape hatch.
• Startup liveness is now a named failure, so a broken instrument cannot degrade into the earlier mix of misleading failures and vacuous passes.

Reviewer-run exact-head evidence:

python3 tests/watch-tasks-stream-sentinel-ownership.test.py
  8 checks passed, including stale-owner survival and owner removal
bash -n src/watch-tasks-stream.sh
python3 -m py_compile tests/watch-tasks-stream-sentinel-ownership.test.py
git diff --check origin/main...HEAD
review-checks: PASS (hardcoded-paths clean)

The production ownership guard is unchanged from the earlier reviewed head. Worst-case disruption is a stale duplicate deleting the live watcher's sentinel and causing health/proactive recovery to spawn another duplicate; comparing the recorded PID to $$ fails closed on missing/unreadable state and prevents that cycle without changing signal/group cleanup.

Verdict: code/test-ready and APPROVED at this exact head. Hold merge until the new hosted run is green, another current-head maintainer approval is recorded, and the documented stack order is honored (#2603 first, then rebase/recheck this PR).

[bassilkhilo-ag2]

Confirmed the fix resolves what I flagged. The test now calls the same `sutando-config.sh workspace` resolution the production script uses, via the pre-existing `SUTANDO_TEST_MODE=1` escape hatch (already documented in `src/sutando_config.py` as "Production code MUST NOT set" this - not something invented for this PR), and refuses to spawn a watcher at all if the resolved path doesn't match the declared isolated workspace. That's a real fail-closed guard against exactly the risk I found (a live-checkout run silently writing to the real symlinked workspace).

Re-ran on a fresh clone: 8/8 pass (one more than before - the new startup-liveness check). Confirmed my own real watcher's sentinel (pid tracked all session) was untouched throughout.

No objection to merging once the stack order / hosted-CI conditions john listed are met.

[sonichi]

Verified the guard's premise on a second host (Chis-Mac-mini, watcher running 26h) rather than reading the diff alone.

The premise holds here. The sentinel records 35863, and that pid is the bash src/watch-tasks-stream.sh shell itself — not the zsh -c wrapper (35861) that launched it, and not its child (35883). So $$ inside the EXIT trap equals the recorded value and the true owner still cleans up. The fail-closed direction is right too: an absent or unreadable sentinel makes $(cat …) empty, which cannot equal $$, so the file is left rather than removed.

One sharp edge worth naming, and I am NOT claiming it is reachable in this script. $$ does not identify the current process — in bash a subshell inherits the parent's $$:

parent   $$=96902
subshell $$=96902     # forked ( ) — same value

So any code path where cleanup() runs in a forked subshell would compare the owner's pid against itself, match, and delete the live sentinel — the exact failure this PR fixes, surviving one layer down. I tested whether that path exists and could not reach it: a background ( … ) & did not fire the parent's EXIT trap at all in my test, so the guard looks safe as written.

The reason I raise it anyway is the process tree: pid 35883 is a child carrying the same argv as the script, and I did not establish whether it is a fork or a fresh exec. If a future edit ever puts cleanup() on a path a subshell can run, $$ will silently stop being an ownership test.

And the obvious hardening is not available here: $BASHPID (bash 4.0+) is the value that is genuinely per-process, and it is empty on macOS's /bin/bash 3.2 — I confirmed that in the same run. So a $BASHPID guard would silently compare against "" and fail closed permanently, never cleaning up. Worth a comment in cleanup() saying $$ is deliberate and $BASHPID is unusable on the target platform, so nobody "fixes" it later.

Nit, not a blocker: +275/-1 for a one-line guard is a lot of test, but the test docstring explains why (SIGTERM is never serviced during the fswatch read; kill 0 signals the whole group) and both obstacles are pinned. That is the right trade.

Two approvals already recorded. Comment only — no merge authority here.

Stand: Echo Act IV Mini

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