diff --git a/tools/lock/with-lock.sh b/tools/lock/with-lock.sh
index ca78406b2..33e9f8ad1 100755
--- a/tools/lock/with-lock.sh
+++ b/tools/lock/with-lock.sh
@@ -3,14 +3,20 @@
 # MEASUREMENTS (test networks, hash-rate samples, simulators, anything whose numbers go in the bench log).
 #   tools/lock/with-lock.sh build   <command...>      one build at a time (builds also nice -n 19, 4 jobs)
 #   tools/lock/with-lock.sh measure <command...>      one measurement at a time, and no build may start meanwhile
+#   tools/lock/with-lock.sh run     <command...>      a functional run (test network, attack harness, simulator whose
+#                                                     outputs are counts, locks, forks, seconds): one at a time, but
+#                                                     builds may continue; nothing hash-rate, latency-in-ms or power
 # Rule (4 October 2026): code and documents run in parallel; builds and measurements queue. Waits up to 2 hours.
+# Evening of 4 October: a 3-hour finality network run held the build lock with six agents queued behind it, so
+# functional runs now take the measure lock only (`run`); `measure` stays for numbers a nice-19 build could disturb.
 set -euo pipefail
 kind="$1"; shift
 dir=/tmp/igneum-locks; mkdir -p "$dir"
 case "$kind" in
   build)   locks=("$dir/build");;
   measure) locks=("$dir/measure" "$dir/build");;
-  *) echo "usage: with-lock.sh build|measure <command...>" >&2; exit 2;;
+  run)     locks=("$dir/measure");;
+  *) echo "usage: with-lock.sh build|measure|run <command...>" >&2; exit 2;;
 esac
 fds=(); i=9
 for l in "${locks[@]}"; do