Vuong Hoang
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`/heid-bug-hunt` on U2's diff, four arms, artifact-only. Eight findings were real against live code; a ninth was already closed by v0.2.1 and is recorded as declined. Full triage in persistent-memory.d/2026-09-22-bug-hunt-panel.md. THE LOCK LIFECYCLE (4/4 convergent, and two defects in one place) `_Locked.__exit__` unlinked `.marks.lock` on the no-op path so a booth that had never been marked was left exactly as it was found. `flock` binds to an INODE: unlinking it under a blocked waiter leaves that waiter holding an exclusive lock on a deleted file while the next writer creates a fresh lock and takes it immediately. Two processes then run the read-modify-write concurrently, the later os.replace drops the earlier one's mark, and both obeyed the protocol. The cleanup existed to protect the booth's TTL, and was failing at that too: creating or removing a directory entry bumps the DIRECTORY's mtime, which is what `_newest_mtime` seeds from. The guard's comment reasons about the lock file's own mtime and misses that the directory moved underneath it. One fix: never unlink the lock, exempt `.<name>.lock` dotfiles from `_newest_mtime`, and restore the directory's mtime after creating one. THE READ PATH'S BLAST RADIUS `_clean_text` did `(text or "").replace(...)` and `marks_for` sorts on `(created, id)`, so a stored `text` that was a dict or a `created` that was a number raised out of the read path. `list_booths` reads every booth's marks on every index load, so one hand-edited file returned 500 for `/` and `/healthz` across all 25 booths. Guarded in two layers — a named type check and a `_hydrate_safe` backstop that cannot raise — and an unreadable mark now renders as ⚠ broken rather than as an empty note. ALSO - import_legacy_asks stamped `created` at whole-second resolution, so two sidecars from the same second lost the ordering the importer had just established and re-sorted alphabetically. Microseconds, per the stated `(mtime, name)` rule. - The five mark-write routes ran a blocking flock on the event loop; they now dispatch through run_in_threadpool, asserted structurally like INV-1. - `/answer` 500'd on a non-string `notes` form value where `/note` handled it. - The inline-doc tile had a flag control and no note field. - The marks panel was suppressed on any booth carrying a links.md. - The viewer's arrow keys and Escape threw away a note being typed. CLI `booth marks` printed a traceback and exited 0 on a failed read, and `--wait` emitted a whole JSON document per poll. `booth answer --wait` read a damaged file as "not yet" and spun the full hour. Both now use real exit codes — 0 ok, 1 unanswered/timed-out, 2 no such pick, 3 unreadable — and `--wait` prints once. `marks.read_error()` lets the CLI ask what the page must not: the browser stays lenient, the machine consumer gets the truth. `scripts/booth` had no tests; it has five now, run against the real script under the system python3, which also makes them a live check on INV-1. 275 tests (253 before). Live service restarted, 25/25 booth pages verified 200.
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80 lines
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# The U2 bug-hunt panel — full triage
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**Date:** 2026-09-22 · **Thread:** `01M33XEC1H0298C0D968FWBN7A` ·
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**Reply:** `01M33YZZ1VYGZ04JGNXNTBXDKS` · **Shipped as:** `v0.2.2`
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`/heid-bug-hunt` on U2's diff (+2251/−632, 20 sections, 18 post-change
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snapshots). Four arms — Gróa (Grok), Hulda (Codex), Regin (GLM-5.2), Kimi
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(kimi-k3) — artifact-only, 4/4 clean transport. Heid adjudicated **9 findings
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(6 bug / 3 robustness)**. Staleness was disclosed at build: `app.py` was edited
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after the 06:38:52Z capture.
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## Triage, five-category
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### Category 1 — genuine add (8 taken, all shipped)
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| # | finding | where | why it was real |
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|---|---|---|---|
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| 1 | Lock-inode split on the no-op unlink (**4/4 convergent**) | `marks._Locked` | `flock` binds to an inode; unlinking under a waiter destroys mutual exclusion silently |
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| 2 | No-op lock churn resets the TTL via **directory** mtime | `marks._Locked` + `app._newest_mtime` | the guard's own comment reasons about the lock FILE's mtime; the directory is what the sweeper reads |
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| 3 | Non-string `text` / `created` raise out of the read path | `marks._clean_text`, `marks_for` sort | `list_booths` reads every booth per page load → one bad file 500s `/` and `/healthz` |
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| 4 | Legacy import stamped `created` at whole-second resolution | `marks.import_legacy_asks` | same-second sidecars re-sorted alphabetically, reversing the order the importer had just set — violates the stated `(mtime, name)` rule |
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| 5 | `/answer` 500s on a non-string `notes` form value | `app.booth_answer` | the sibling `/note` guards it; same parser, same class of value, two answers |
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| 6 | All five mark-write routes hold a blocking `flock` on the event loop | `app.py` | a contended lock freezes every route, not just the one request |
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| 7 | CLI conflates a reader crash with "open" / "unanswered" | `scripts/booth` | `marks` printed a traceback and exited 0; `answer --wait` spun the full hour on a damaged file |
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| 8 | The inline-doc tile had `markcontrols` and not `marknotes` | `booth.html` | flag a report, cannot say why — on the one item kind that is prose |
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Two more taken on the same sweep, found while fixing the above rather than by
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the panel: a broken mark of any shape now renders **⚠ broken** instead of as an
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empty note (the rule `_hydrate` states for picks, applied to all three shapes),
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and the marks panel is no longer suppressed on a booth that carries a
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`links.md` *and* has marks.
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### Category 3 — restatement of a settled prior (1, no change)
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**Corrupt read → filtered writeback → silent deletion** (hulda F2, kimi F3,
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gróa F4; Heid ranked it #3). **Already fixed in `v0.2.1`** by
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`_read_raw_strict` + `MarksCorrupt` — reads lenient, writes strict. The panel
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reviewed the pre-fix capture and the staleness was disclosed up front. Verified
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against the current source before declining, not assumed.
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This is the exact case the cross-frontier triage discipline warns about: a
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confident, well-argued, four-arm-corroborated finding against code that no
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longer exists. **Check what the peer actually read before treating an omission
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or a defect claim as new.**
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### Category 4 — out of place, parked (2)
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- **Note-id recycling** (`note-1` reused after a withdrawal) lets a stale tab
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delete a newer note. Real mechanism; needs two tabs and an interleaving, and
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the Booth has one viewer. Non-reused ids are a schema change, not a patch.
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- **Unvalidated flag / note targets** accumulate orphan marks. Targets come
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from rendered items; the operator is the only writer through the browser.
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### Category 5 — wrong-grounding (1)
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**`delete_mark` can remove a pick, not only a note.** Framed as an
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access-control divergence. There is no auth by design, and restricting it would
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remove the only way to withdraw a pick that hydrates broken. Declined; the
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docstring is the thing that was imprecise, not the behaviour.
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## What the round is worth remembering for
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1. **The two review gates stayed complementary a second time.** The contract
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panel (2026-09-21) found three defects; this bug-hunt found eight more, with
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**no overlap**. Both ran on the same unit. Neither substitutes.
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2. **The panel beat the code's own comments three times.** The bundle's comments
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are unusually honest and still wrong about what protected the TTL, and
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"written atomically" sat next to a filter-then-replace. **A comment is a
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claim, and a claim can be tested.**
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3. **The headline bug class shipped with zero guard coverage, and both mutation
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tables said so.** `test_a_no_op_write_does_not_touch_the_booth` asserted only
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that `.marks.json` was absent — so removing the lock unlink, removing the
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whole lock lifecycle, or bumping the directory clock all **SURVIVED** it. The
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test asserted an artifact of the property instead of the property. The
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replacement asserts `booth_age_seconds` directly, with a positive control (a
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real mark still resets the clock) so the fix cannot overshoot into "marking
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is never activity".
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4. **`scripts/booth` had no tests at all** and two findings lived there. It has
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five now, running the real script under the system `python3`.
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