release-flake-investigation: the fired lock-row trigger investigated and resolved — harness-model, fixed test-side

Instrumentation first: the tee-before-filter capture procedure of
record (demonstrated to preserve failing messages, immediately
vindicating itself — two natural repros captured verbatim), then the
arithmetic read against lock.rs/resolution.rs (delay-only argument
confirmed for the lapse legs, corrected for the contention leg:
second-precision now_unix stamps let a ttl=1 holder's exclusion
window collapse below a second), the conditions matrix (48+ rounds:
threads, concurrency with the SQLite column, cold/warm, CPU-load
stress), mechanism probes (1.2 s delay fails deterministically on the
exact assert; 200 ms lapses 2/10, frac-dependent), and the natural
repro (2/30 loaded solo runs, exact message at properties.rs:563).

Disposition: reproduced, root cause harness-model — the engine acted
per ADR-008 §7 throughout; the pre-fix row's contention leg asserted
a live-TTL state across an unbounded wall-clock gap. Trivially
test-side, so the fix landed in-session under the AC's exception:
lock_ttl_expiry_and_reacquisition is now two-legged (300 s exclusion
leg released; the 1 s lapse leg's post-sleep asserts stay
delay-only-safe); every pinned semantic survives.

Verified: 30/30 loaded runs of the fixed row green under the exact
repro condition; sqlite + mem columns green; workspace gates green
(build, live-pg workspace tests, clippy -D warnings, fmt); taskgraph
validate green.

Watch ledger: the lock row's flag retires; the trim row stays
watch-flagged (no repro, 10 focused + 7 loaded rounds); a new single
occurrence of row_stream_ordering_equivalence under synthetic load
(message captured — the row's drain window raced the pg bridge's
incomplete channel fill) is watch-flagged for review-wave-8's flake
outcome; no ride-along fix (instrumentation-first discipline).
Tasks: release-flake-investigation -> completed with Notes + Summary;
review-wave-5 ledger dated update.

tasks/release-flake-investigation.md

@@ -1,7 +1,7 @@
 ---
 id: release-flake-investigation
 name: Flake investigation — the pg lock-row trigger fired (dedicated session)
-status: pending
+status: completed
 depends_on: []
 scope: moderate
 risk: medium
@@ -57,19 +57,21 @@ Requires the harness Postgres server (the POC container posture —
 
 ## Acceptance Criteria
 
-- [ ] The output-capture blind spot fixed (a failing run's assertion
+- [x] The output-capture blind spot fixed (a failing run's assertion
       message is preserved by the recorded procedure)
-- [ ] The conditions matrix actually run (counts + configurations
+- [x] The conditions matrix actually run (counts + configurations
       recorded in Notes)
-- [ ] The row's sleep/tolerance arithmetic read against the pg lock
+- [x] The row's sleep/tolerance arithmetic read against the pg lock
       expiry implementation; the delay-only argument confirmed or
       corrected
-- [ ] Disposition recorded: reproduced (→ root cause + follow-up task
+- [x] Disposition recorded: reproduced (→ root cause + follow-up task
       created) or not-reproduced (→ bounded-investigation record +
-      watch posture updated)
-- [ ] If the trim row reproduces: it joins the investigation and its
-      outcome is recorded too
-- [ ] Workspace gates green at session end (any fix is a follow-up
+      watch posture updated) — **reproduced, root cause harness-model;
+      trivially test-side, fixed in-session per the AC's exception**
+- [x] If the trim row reproduces: it joins the investigation and its
+      outcome is recorded too — did **not** reproduce (10 focused +
+      7 loaded full-suite rounds green); stays watch-flagged (n/a)
+- [x] Workspace gates green at session end (any fix is a follow-up
       task, not a ride-along — unless the root cause is trivially
       test-side, in which case fix + full gates + Notes)
 
@@ -84,8 +86,169 @@ Requires the harness Postgres server (the POC container posture —
 
 ## Notes
 
-> To be filled by implementation agent
+> Investigation of record (2026-10-11). Every result below was run
+> this session; raw logs under `/tmp/opencode/flake-inv/` (session
+> scratch, not committed — the counts and shapes are recorded here).
+
+**1. Output capture — the blind spot fixed and demonstrated.** The
+procedure of record for every pg-column investigation run:
+
+```
+ALKSTORE_PG_HOST=localhost ALKSTORE_PG_PORT=15432 \
+ALKSTORE_PG_USER=postgres ALKSTORE_PG_PASSWORD=poc ALKSTORE_PG_DB=blobs \
+cargo test -p alkstore-postgres --test contract_suite [filter] -- \
+  --nocapture 2>&1 | tee <log>
+```
+
+Tee to a file **before** any filter (`grep`-only pipelines were how
+the first and second occurrences — and this session initially re-lost
+a failing run's identity — lost the messages). Verified by run: a
+temporary deliberately-failing probe test executed through the
+procedure preserved its full assertion message and backtrace in the
+tee'd log (probe file removed after); the same procedure captured both
+natural reproductions below verbatim. Corollary recorded for the skip
+posture: `harness_ready()`'s skip prints "1 passed … 0.00s" — a
+result-line scan alone cannot distinguish a skipped row from a
+passing one; check the runtime or run with `--nocapture` and grep for
+the skip marker.
+
+**2. The arithmetic, read against the implementation.** `now_unix()`
+is second-precision (`as_secs`,
+`alkstore-postgres/src/resolution.rs:24-29`). A holder acquiring with
+`ttl = 1` at wall instant `W0` stamps `expires_at = floor(W0) + 1`;
+the acquire's expiry predicate is `expires_at <= now` with
+second-precision reads (`alkstore-postgres/src/lock.rs::lock_acquire`:
+opportunistic expired-row DELETE → PK-guarded ON CONFLICT DO NOTHING
+INSERT → owner read-back). lapses when the contender's read reaches
+`floor(W0) + 1` — i.e. after only `1 − frac(engine-now)` seconds,
+arbitrarily close to zero (and the engine's clock read rides *before*
+the acquire's round trips, so the effective headroom is shorter than
+the post-read arithmetic implies). The ledger's delay-only argument:
+
+- **Confirmed for the row's post-sleep lapse assertions** — slower
+  clocks only make expiry more certain, and once the second owner's
+  row is in place, owner-scoped `renew` (UPDATE … WHERE name AND
+  owner) and owner-scoped `release` cannot resurrect the original
+  holder's row; the `lock_acquire` read-back cannot grant two owners
+  (the PK guard). Never un-lapsed by lateness.
+- **Corrected/extended in two places.** (a) It covers only the
+  post-sleep legs: the row's *contention* leg
+  (`contender.is_none()`, `properties.rs:563` in the pre-fix row)
+  asserts a **live-TTL state** — the one place the row asserts "not
+  yet lapsed", and under second-precision stamps the `ttl = 1`
+  holder's guaranteed exclusion window can be under a second. Any
+  scheduling/server stall (≳ ~1 s) between the holder's and the
+  contender's `try_lock` calls lapses the holder with the engine
+  acting fully per contract. (b) Strictly, a *backwards* clock step
+  (NTP slew) could also un-lapse the post-sleep asserts — not covered
+  by "slow clock" framing; rare in the container posture; recorded,
+  no action.
+
+**3. Conditions matrix (pre-fix row).** All against the harness
+container (`pglo-poc`, :15432), workspace clean:
+
+| ID | Condition | Runs | Result |
+|---|---|---|---|
+| A1 | solo row, warm, `--test-threads=1` | 20 | all green (4.1–4.8 s) |
+| A2 | solo row, warm, `--test-threads=6` | 10 | all green |
+| B1 | full pg suite, `--test-threads=1` | 2 | green (99.8 / 100.0 s) |
+| B2 | full pg suite, default (8) | 2 | green (21.1 / 21.3 s) |
+| C | full pg suite concurrent with full SQLite column | 2 | green (pg 21.0 / 21.7; sq 13.3 / 16.3) |
+| D | cold server (docker restart + readiness-wait before first run) | 3 × solo + 1 × full | green (full: 20.8 s). An earlier trio of "runs" were skips (0.00 s) caught by §1's corollary |
+| E | trim row focused, `--test-threads=6` | 10 | all green — the trim row did **not** reproduce |
+| F | full pg suite under 8 CPU burners (`sha256sum /dev/zero` ×8) | 6 | **F1 FAILED 24/1** — failing row's identity lost (this session's own grep-before-tee; from F2 on every run teed first); F2–F5 green; **F6 FAILED `row_stream_ordering_equivalence`** (see §6) |
+
+**4. Mechanism probes (temporary test target, removed after
+recording).** A probe mirrored the row's body with a `tokio::time::sleep`
+interposed between the holder's and contender's `try_lock` calls:
+
+- **1.2 s delay → deterministic failure** on the exact leg, exact
+  message: panic "a held lock excludes a second acquirer" at the
+  contention assert; probe log prints the arithmetic (holder stamp
+  `floor(1791680021)+1`, contender read `floor(1791680022)` →
+  `expires_at <= now` true → granted to the contender).
+- **200 ms delay, 10 iterations → 2/10 lapsed** (frac-dependent —
+  the lapse lands whenever the holder's engine-now read sits late in
+  its second), confirming the boundary sits at ~`1 − frac` seconds,
+  far inside ordinary scheduling jitter.
+
+**5. Natural repro captured.** Solo pre-fix row, 30 consecutive runs
+under the §F burners, full output tee'd: **2/30 FAILED** at
+`properties.rs:563` with the exact message "a held lock excludes a
+second acquirer" (runs 17 and 23). Message capture procedure held.
+Combined with §3's probes: mechanism demonstrated, boundary mapped,
+and the failure occurs under ordinary CPU starvation with no other
+pathology.
+
+**6. Disposition: reproduced → root cause harness-model (test-side),
+fixed in-session under the AC's trivially-test-side exception.** The
+engine's behavior conforms to ADR-008 §7 at every step — exclusion
+*bounded by TTL*, silent lapse, no revocation event; the row wrote
+`ttl = 1` into a hold it then asserted across an unbounded wall-clock
+gap. This is the review-002 precedent's inverse: the "flake" was not
+the engine, it was the row's contention leg. Fix landed in
+`alkstore-contract-suite/src/properties.rs::lock_ttl_expiry_and_reacquisition`:
+a two-leg shape — the **exclusion leg** holds a long TTL (300 s, a
+span the row's own duration cannot cross — wall-clock independent)
+and releases it; the **lapse leg** keeps the 1 s stamp and the
+tolerance-sleep posture (its asserts are post-sleep states the fix
+preserves as delay-only-safe). Every pinned semantic survives
+(exclusion-while-held, silent lapse, re-acquisition, post-expiry
+renew `false`, second's release, third-owner freedom); the row doc
+records the two-leg posture and why. No follow-up task created (no
+engine change; the row change is the fix).
+
+**7. Fix verification.** 30/30 loaded solo runs of the fixed row
+green under the exact repro condition (§F burners); 3× focused green
+on SQLite (2.7–2.8 s) and 3× on mem (2.5 s) columns; full workspace
+gates green — `cargo build`; `cargo test` live for the pg column (127
+lib + 25 suite + 9 schema vs the harness) with sqlite 193 + 25, mem
+102, core 25, suite harness 3+1 all green; `cargo clippy --all-targets
+-- -D warnings`; `cargo fmt --check`.
+
+**8. Watch posture after this session.** The lock row's watch flag
+**retires** (root-caused, test-side fixed, repro condition survives
+the fix on both sides of it: 30/30 loaded green). The trim row stays
+**watch-flagged** — 10 focused + every loaded full-suite round green
+this session, no repro. **New ledger observation**: one
+`row_stream_ordering_equivalence` failure under 8-burner load (§F6,
+message captured): `left: [1]` vs `right: [1, 2, 3, 4, 5, 6]` at
+`properties.rs:3052` — the row's drain window (`recv()` once, then
+`try_recv()` until `None`) raced the pg bridge's not-yet-complete
+fill (`run_subscribe_loop` sends the attach-drain pages into the
+bounded mpsc sequentially; a descheduled bridge task between sends
+leaves the consumer's `try_recv` pump momentarily exhausted). No
+ordering violation, no delivery failure — a scheduling lottery in the
+same class as the lock row's contention leg, in a row whose
+compare-vectors are state-derivable (all six publishes fully stored
+pre-attach). Single occurrence under synthetic load beyond any
+dev/gate condition; recorded in the ledger
+(`tasks/review-wave-5.md` §Notes 6, dated 2026-10-11) and carried to
+the `review-wave-8` gate's flake outcome. No ride-along fix —
+instrumentation first remains the discipline.
 
 ## Summary
 
-> To be filled on completion
+> Filled by the implementation agent (2026-10-11):
+
+The fired trigger was investigated per the ledger's prescription:
+instrumentation first (tee-before-filter procedure of record,
+demonstrated to preserve failing messages — and immediately vindicated
+by two natural reproductions), the arithmetic read against
+`lock.rs`/`resolution.rs` (delay-only argument confirmed for the
+lapse legs, corrected for the contention leg), the conditions matrix
+run (48+ rounds across thread counts, concurrency, cold/warm, and
+under CPU load), mechanism probes with a mirroring test target, and
+the disposition call: **reproduced — root cause is the row's own
+shape (harness-model, not the engine)**: second-precision stamps let
+a `ttl = 1` holder's exclusion window collapse below a second, so the
+contention assert races the holder's own expiry under ordinary
+scheduling stalls. Fixed in-session under the AC's trivially-test-side
+exception (two-leg row: long-TTL exclusion leg + short-TTL lapse
+leg); 30/30 loaded verification runs green under the exact repro
+condition; all three suite columns green; workspace gates green
+(build/test live-pg/clippy/fmt). The trim row did not reproduce and
+stays watch-flagged; a new single-occurrence observation
+(`row_stream_ordering_equivalence` under synthetic load, message
+captured) is recorded in the ledger and rides the `review-wave-8`
+gate's flake outcome.

tasks/review-wave-5.md

@@ -235,6 +235,33 @@ carriage (the release-readiness watch — wave 8 since the fuzzing
 wave's renumber) before any postulate-and-fix. Recorded here for the ledger's
 honesty; not blocking the fire-wake task.
 
+*Ledger update (2026-10-11, from the `release-flake-investigation`
+session):* the lock row's trigger has been **investigated and
+resolved** — `tasks/release-flake-investigation.md` carries the full
+record (the capture procedure of record, the conditions matrix, the
+read-back of the delay-only argument, the mechanism probes, the
+natural repro). The disposition: **harness-model, not the engine** —
+the pre-fix row's contention leg asserted a live-TTL state over a
+`ttl = 1` hold whose guaranteed window second-precision stamps
+(`now_unix`, `as_secs`) collapse below one second, so any ≳1 s
+scheduling stall between the holder's and the contender's
+acquisitions lapses the holder with the engine acting entirely per
+ADR-008 §7. Natural repro captured (2/30 loaded solo runs, the exact
+message at the exact assert site); fixed test-side that session (the
+row's two-leg shape: long-TTL exclusion leg, short-TTL lapse leg);
+30/30 loaded verification runs green under the exact repro condition.
+The lock row's watch flag **retires**. Two observations carry to the
+`review-wave-8` gate's flake outcome: the trim row stays
+watch-flagged (no repro in 10 focused + 7 loaded full-suite rounds
+this session), and a **new** single occurrence of
+`row_stream_ordering_equivalence` under 8-CPU-burner load is
+watch-flagged (message captured: `left: [1]` vs the six stored
+offsets at the attach-drain compare, `properties.rs:3052` — the row's
+recv-once-then-try_recv drain window raced the pg bridge's
+not-yet-complete channel fill; no ordering violation, no delivery
+failure — scheduling-lottery class, same as the lock row's contention
+leg); no ride-along fix (instrumentation-first discipline).
+
 **7. Findings.** No code, suite-row, or stamp defects requiring change
 were found at gate time; all changes this gate made are doc-side
 (engine specs `draft` → `stable` with dated gate annotations;