claim(2pc): PC1 conservative prune deployed+verified; PC2/PC3 local-store cache confirmed

ci-docker-prune (gated surgical prune) live on cc-ci: old autoPrune --all gone, new timer
enabled (daily), no-ops below 80% disk keeping the local image cache, never --all/--volumes.
Daemon stays PAT-authenticated (nptest2); /var/lib/docker retained across rebuild. PC3 proof:
redis:7-alpine deploy->teardown(service rm, image retained)->redeploy = "Image is up to date",
no layer re-download (cold 5303ms -> warm 674ms). Docs: runbook "Image cache & prune policy",
warm.md, DECISIONS Phase-2pc, IDEAS (registry pull-through cache deferred + revisit trigger).
Gate 2pc CLAIMED, awaiting Adversary cold-verify.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/runbook.md

@@ -24,10 +24,10 @@ curl -s -H "Authorization: Bearer $DT" --proxy socks5h://localhost:1055 \
   convergence `TIMEOUT` (default 300s). Bump `TIMEOUT` via the recipe's `recipe_meta.py` `EXTRA_ENV`
   (lasuite-docs uses 900). Verify the stack converges manually: `docker stack services <stack>`.
 - **`toomanyrequests: unauthenticated pull rate limit`** (task Rejected "No such image"): Docker Hub
-  anonymous rate limit — the A1 registry-creds finding. Provide Docker Hub creds (sops `secrets/`,
-  wire into the docker daemon). Do **not** `docker image prune -af` mid-breadth — it evicts cached
-  images and forces re-pulls that hit the limit. Check disk first: `df -h /` (heavy recipes need
-  headroom; prune only `dangling` between runs or rely on the daily autoprune).
+  anonymous rate limit. The daemon is now PAT-authenticated (sops `dockerhub_auth` →
+  `/root/.docker/config.json`; `docker info` Username=nptest2; 200/6h per-account). Do **not**
+  `docker image prune -af` — it evicts cached base/in-use images and forces re-pulls that burn the
+  limit. See **Image cache & prune policy** below. Check disk first: `df -h /`.
 - **`authentication required: Unauthorized` fetching recipe tags:** an abra command tried to fetch
   from the private mirror origin. All recipe-touching harness calls pass `-C -o` (chaos+offline);
   `recipe_versions`/upgrade use the upstream tags fetched read-only at clone time. If you see this,
@@ -54,6 +54,31 @@ abra app volume remove "$D" -f -n; abra app secret remove "$D" --all -n; abra ap
 ```
 Confirm clean: `docker service ls | grep <prefix>` returns nothing.
 
+## Image cache & prune policy
+
+On this **single host, Docker's own local image store IS the cache** — a pulled image stays, and
+re-deploys (cold tests, warm canonical, reboots) reuse the local layers with no re-download; the
+daemon is PAT-authenticated so a warm redeploy makes at most one authenticated manifest check.
+Teardown removes the run's services/volumes/secrets/.env but **never images** — so the next deploy
+of the same recipe is local. (No separate `registry:2` pull-through cache: it only pays off
+multi-node / separate-survivable storage, neither of which we have — see DECISIONS Phase-2pc.)
+
+Pruning is the **`ci-docker-prune`** unit (`nix/modules/docker-prune.nix`), a daily timer that is
+**surgical and triple-gated** — it does **nothing** unless ALL hold: (1) `/` usage ≥ 80% (genuine
+disk pressure), (2) no run-app stack live (never prune mid-run), (3) no swarm service converging
+(no deploy/pull in flight). When it does run it prunes only **dangling images + stopped containers +
+dangling build cache, age-gated `until=24h`** — **never `--all`** (keeps tagged base/in-use images),
+**never `--volumes`** (warm canonical data). The old `virtualisation.docker.autoPrune --all` was
+removed — its daily `--all` evicted cached recipe base images → cold re-pull → Hub rate-limit churn.
+
+```sh
+ssh cc-ci 'systemctl list-timers ci-docker-prune.timer --no-pager; \
+           systemctl start ci-docker-prune.service; \
+           journalctl -u ci-docker-prune.service -n 3 --no-pager'   # below 80% -> no-op, keeps cache
+```
+Reclaim manually under real pressure (still surgical, never `-af`):
+`ssh cc-ci 'docker image prune -f --filter until=24h'` (dangling only).
+
 ## Re-running / triggering by hand
 
 - Re-comment `!testme` on the PR (distinct comment id → re-runs; deduped per comment).