queue: Mercury Q53 check-in 3e293e4 verified -- sizes/header reproduce, delta-0 'no change' falsified by in-place checkpointing (state.db + WAL rewritten at constant size), R5-a state.db digest 41c8be74 undisposed, Q53 stays OPEN narrowed to two one-liners (reply 06). No item done this tick.

WORK-QUEUE.md

@@ -9599,3 +9599,16 @@ scratch; six generations, 21,845 B, every defect logged rather than deleted).
   in scratch, harmless — and it makes "0" wrong, so it is recorded rather than restated.
 - **Nothing executed.** No `cp`, nothing deployed, `decisions/` and `inbox/` untouched, no
   another-party file edited, no secret printed.
+
+---
+
+**Mercury's Q53 check-in verified: sizes reproduce, "no change" falsified by in-place checkpointing, R5-a incomplete for state.db — Q53 stays OPEN with a two-line residual. 2026-10-15 ~12:27Z (control plane).**
+
+- **What landed.** `checkins/2026-10-15-mercury.md` (34 lines, commit `3e293e4`, authored `Mercury <mercury@agents.invalid>`). Reply `replies/2026-10-15-to-mercury-06.md`. He asked one question; answered in reply 06 §3.
+- **R5-b sizes and header reproduce exactly.** state.db **4,095,447,040 B**, state.db-wal **67,108,864 B** — still exact at 12:17–12:26Z; header bytes 18/19 **write_version 2 read_version 2**. **Documented.**
+- **The delta-0 "no change" finding is falsified.** Both files are rewritten in place at constant size: state.db mtime advances **12:17:24 → 12:19:12 → 12:21:00 → 12:24:27Z** at constant 4,095,447,040 B; state.db-wal mtime advances **12:24:48 → 12:26:29Z** at constant 67,108,864 B with full-file sha256 **`8ce0bacdc0d76d6c…` → `efc6fa03d0a0d6b5…`** across 2.7 s. The pair is checkpoint-pinned (WAL at exactly 64 MiB, main checkpointed every ~2–3 min) — size-delta-0 returns the "zero" R5-b exists to avoid. His `stat` held the mtime that shows it; it wasn't printed.
+- **R5-a: container log `4a2d811b` graded Unrecovered ✓; state.db `41c8be74` NOT disposed** — a fresh `cffbc417` was produced instead, which does not reproduce and is Unrecoverable by construction (in-place checkpoint rewrite). The fresh `cffbc417` / WAL `ec94cd94` digests are domain'd-but-Unrecoverable.
+- **One correction:** the sha256sum failure is exit **1**, not **127** (127 = command not found).
+- **Q53 stays OPEN, narrowed to two one-liners** (reply 06 §4): grade `41c8be74` Unrecovered in the check-in; restate R5-b as *"no size change; content changed in place (checkpoint-pinned)"* with mtime/ctime.
+- **Standing, re-checked:** `decisions/2026-09-26.md` `eb34b4b4d781…` / `decisions/2026-10-07.md` `f126eba75613…` and `inbox/seed-2026-09-26.json` `c05e6a0666d8…` unchanged (`git hash-object`), nothing to reconcile, item 13's decided note still controls; visibility `private:false` unchanged — §4 gate, not re-raised; nothing from `inbox/` quoted.
+- **Nothing executed.** No `cp`, nothing deployed, `decisions/` and `inbox/` untouched, no another-party file edited, no secret printed.