diff --git a/checkins/2026-10-18-volt.md b/checkins/2026-10-18-volt.md
index 99d5c9a..da9dfee 100644
--- a/checkins/2026-10-18-volt.md
+++ b/checkins/2026-10-18-volt.md
@@ -81,6 +81,24 @@ two columns apart). Called out because the number was in a table I was about to
 quote in this file, and a mislabelled count is the exact defect this archive
 keeps grading other lanes for.
 
+**A sibling gate's silent zero, found by using it.** `doc_census_check.py
+--tools <name>` takes repo-relative paths; passing the bare basename
+`checkin_check.py` scanned **zero** tools and exited **0** with `tools scanned at
+8932d06: 0` — indistinguishable from a clean pass over an empty claim set. Fixed
+at `76043b7`: a requested name that is not tracked at the rev is now rc 2
+with the names and the shape of a valid one, and `resolve_tools()` splits the
+request from the tree so both halves are unit-tested (2 cells; 33 → 35).
+
+    $ python3 tools/doc_census_check.py --repo . --tools checkin_check.py
+    cannot grade: --tools names nothing tracked at HEAD: checkin_check.py
+      names are repo-relative, e.g. --tools tools/checkin_check.py; a filter
+      that matches nothing is not a clean scan
+    rc=2
+    $ python3 tools/doc_census_check.py --repo . --rev 8932d06 --tools tools/checkin_check.py --no-run
+    tools scanned at 8932d06: 1 (internal-split only, label vocabulary)
+    tools/checkin_check.py: 0 INTERNAL SPLIT, 0 STALE claim(s), 0 leg failure(s), 0 claims checked
+    rc=0
+
 **Deliberately not done.** The tool renames nothing. The 25 historical names are
 the record; a gate that edited the record to turn its own report green would be
 worth less than the 25 lines it rewrote. That is why `--since` exists: the gate
@@ -101,6 +119,12 @@ Nothing. One open question needs a ruling, not a blocker — see Ask.
   check-ins were spent on claims that read STALE at a new rev. Verdict to be
   appended to this file, not asserted here.
 - Carry the four headings in every check-in from today.
+- The census verdict for the new tool, measured rather than assumed:
+  `tools/checkin_check.py: 0 INTERNAL SPLIT, 0 STALE claim(s), 0 leg failure(s),
+  0 claims checked` at `8932d06` — it carries no docstring census block, so
+  `doc_census_check` has nothing to adjudicate in it. The population question
+  (does a twelfth tool make a *sibling's* claim STALE?) is the full run's to
+  answer, not this line's.
 
 ## Ask