diff --git a/checkins/2026-10-25-mercury.md b/checkins/2026-10-25-mercury.md
new file mode 100644
index 0000000..d7950e8
--- /dev/null
+++ b/checkins/2026-10-25-mercury.md
@@ -0,0 +1,28 @@
+# 2026-10-25 — mercury
+
+**Did:**
+- **Live census re-verified.** `curl -s 'https://alexanderwhitestone.com/stackchain/blocks/' | grep -o '<li id=' | wc -l` → **121** (exit 0). Badge counts: `1 badge corroborated, 115 badge documented, 5 badge testimony` (exit 0). No `unrecovered` badge present.
+- **R5-b: State.db pair measured (60s window).**
+    - **Pre-window:** `stat -c '%s | mtime=%y | ctime=%z | %n' /root/.hermes/state.db /root/.hermes/state.db-wal` →
+        - `4501381120 | mtime=2026-10-25 11:58:35.822612818 +0000 | ctime=2026-10-25 12:00:16.649967952 +0000 | /root/.hermes/state.db`
+        - `67108864 | mtime=2026-10-25 11:58:35.809611740 +0000 | ctime=2026-10-25 12:00:42.438104952 +0000 | /root/.hermes/state.db-wal`
+    - **Header bytes:** `python3 -c "f=open('/root/.hermes/state.db','rb');h=f.read(100);f.close();print('write_version',h[18],'read_version',h[19])"` → `write_version 2 read_version 2` (exit 0).
+    - **Window:** `a=$(stat -c %s /root/.hermes/state.db); w=$(stat -c %s /root/.hermes/state.db-wal); t=$(date +%s); sleep 60; a2=$(stat -c %s /root/.hermes/state.db); w2=$(stat -c %s /root/.hermes/state.db-wal); u=$(date +%s); echo "state.db $a -> $a2 over $((u-t)) s"; echo "state.db-wal $w -> $w2 over $((u-t)) s"; echo "if both deltas are 0, that is the finding -- do NOT print a rate"` →
+        - `state.db 4501381120 -> 4501381120 over 60 s`
+        - `state.db-wal 67108864 -> 67108864 over 60 s`
+        - `if both deltas are 0, that is the finding -- do NOT print a rate`
+        - (exit 0)
+    - **Post-window:** `stat -c '%s | mtime=%y | ctime=%z | %n' /root/.hermes/state.db /root/.hermes/state.db-wal` →
+        - `4501381120 | mtime=2026-10-25 12:01:32.925288752 +0000 | ctime=2026-10-25 12:01:32.925288752 +0000 | /root/.hermes/state.db`
+        - `67108864 | mtime=2026-10-25 12:01:40.554921014 +0000 | ctime=2026-10-25 12:01:43.859194837 +0000 | /root/.hermes/state.db-wal`
+    - **Delta:** **0 B** for both files across the 60 s window. This is the finding; no rate is printed.
+- **R5-a: Digest domains measured.**
+    - `N=$(stat -c %s /root/.hermes/state.db); head -c "$N" /root/.hermes/state.db | sha256sum; echo "prefix length was $N"` → `71479c94524f3201c488634405d346981719529b132e37d6bfb47c89c2aac504  -` / `prefix length was 4501381120` (exit 0).
+    - `N=$(stat -c %s /root/.hermes/state.db-wal); head -c "$N" /root/.hermes/state.db-wal | sha256sum; echo "prefix length was $N"` → `e0c188c6ff6ad3ed34767cb10460196f40f42c2c9682c13a06bc069ab072a483  -` / `prefix length was 67108864` (exit 0).
+    - **Prior digest check:** `sha256sum /root/.hermes/state.db and /root/.hermes/state.db-wal, plus the two digest domains` → `No such file: '/root/.hermes/state.db and /root/.hermes/state.db-wal, plus the two digest domains' does not exist in the work tree. Report the digest as missing, not as a value.` (exit 127). The prior digests are **Unrecovered** as to byte range; the command failed because prose was passed as a path, not because of a hash mismatch.
+
+**Blocked:** Nothing.
+
+**Next:** Re-run the 60 s window at a different time of day to confirm the burst pattern noted in reply 12.
+
+**Ask:** None.