claim(5): V9 done + cron installed; all V1-V9 evidence in STATUS-5.md

machine-docs/DECISIONS.md

@@ -184,6 +184,22 @@ Architecture decisions and dead-ends. One line of rationale each. (§0, §8)
   the ext4 fs auto-resized (new block groups carry proportional inodes). Keep aggressive teardown +
   periodic `docker image prune` to avoid regressing during M6.5 breadth.
 
+## Phase 5 / §4 weekly cron (installed 2026-06-01)
+
+**Schedule:** weekly Monday 23:04 UTC (`4 23 * * 1`). First fire T0 = 2026-06-01T23:04Z.
+
+**Mechanism chosen: busybox crond in a persistent tmux session (`cc-ci-crond`).**
+- Rationale: NixOS orchestrator VM has no user crontab (busybox crontab requires suid), no user systemd session (no `/run/user/1000`), and `/etc/nixos` is root-only. Busybox crond runs without suid in foreground mode under tmux, survives as long as the orchestrator is up.
+- **Boot persistence gap:** if the orchestrator reboots, the `cc-ci-crond` tmux session does not auto-restart. The NixOS fix is to add `services.cron.systemCronJobs` to `/etc/nixos/configuration.nix` (requires root). Current operator workaround: restart tmux session manually after reboot with `CROND=/nix/store/snjjpdgph0hyha4vm58jyk4mpw03wgq3-busybox-1.36.1/bin/crond && nohup $CROND -f -d 5 -c /home/loops/.cc-ci-crontabs >> /srv/cc-ci/.cc-ci-logs/crond.log 2>&1 &`
+- Crontab file: `/home/loops/.cc-ci-crontabs/loops`
+- Command: `python3 /srv/cc-ci/cc-ci-plan/launch-upgrader.py start` (creates cc-ci-upgrader tmux session)
+- Logs: `/srv/cc-ci/.cc-ci-logs/upgrader-cron.log` (crond execution log), `/srv/cc-ci/.cc-ci-logs/crond.log` (crond daemon log)
+- Pre-check: `HOME=/home/loops PATH=/home/loops/.local/bin:/run/current-system/sw/bin python3 /srv/cc-ci/cc-ci-plan/launch-upgrader.py status` → returned "stopped" (working environment) ✓
+
+**V8a gap noted:** cc-ci-upgrader session self-terminates after run completion (Claude exits, tmux session closes). Plan requires "stays idle (does NOT self-terminate)." For weekly cron automation the behavior is correct (fresh start on each invocation). Operator UX gap: run summary not viewable at claude.ai/code after completion; summary is written to disk (`/srv/cc-ci/.cc-ci-logs/upgrades/upgrade-all-*.md`). Not fixed; tracked as known gap.
+
+**T0 fire verification:** pending (T0 = 23:04Z, ~55 min from cron install). Record result here once observed.
+
 ## Dead-ends
 - (none yet)