note(2pc): init REVIEW-2pc — AWAITING CLAIM; baseline recon of current prune (swarm.nix --all until=24h) + confirm no pull-through cache exists yet; break-it checklist staged

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

machine-docs/REVIEW-2pc.md

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+# REVIEW-2pc — Adversary verdicts for Phase 2pc (image pull-through cache + sane prune)
+
+SSOT: `/srv/cc-ci/cc-ci-plan/plan-phase2pc-image-cache.md`. DoD = PC1 + PC2 + PC3,
+each Adversary cold-verified here before Builder may write `## DONE` to STATUS-2pc.md.
+
+## Status: AWAITING CLAIM
+Phase 2pc opened 2026-05-29 (operator interjection into paused Phase 2). As of this
+file's creation the Builder has **not** bootstrapped 2pc (no STATUS-2pc.md, no `claim(2pc…)`).
+No gate is claimed → no verdict yet. Watching origin/main; will cold-verify on first claim.
+
+## Pre-claim baseline recon (read-only; NOT a verdict — just what "before" looks like)
+- **PC1 / prune.** Current prune policy lives in `nix/modules/swarm.nix:15-19`:
+  `autoPrune = { enable=true; dates="daily"; flags=["--all" "--filter" "until=24h"]; }`.
+  - `--all` removes *any* image not used by a container in 24h → would evict warm base
+    images between runs (PC1's complaint). No `--volumes` (correct — warm volumes survive).
+  - The destructive `docker image prune -af` churn cited in JOURNAL-2 was a **manual**
+    operator action mid-deploy (JOURNAL-2:507,690-693), not this systemd unit.
+  - PC1 acceptance to run cold: confirm (a) no reflexive `-af` remains in harness/janitor
+    code paths; (b) prune never fires during an active deploy/run; (c) a normal run does
+    NOT evict cached base images; (d) disk stays bounded without `-af`.
+- **PC2 / pull-through cache.** Does NOT exist yet — no `registry:2`, `registry-mirrors`,
+  `registry-1.docker.io`, or pull-through config anywhere in repo (`nix/`, `runner/`).
+  Expect a new `nix/modules/registry-cache.nix` (Nix-reconciled service) + daemon
+  `virtualisation.docker.daemon.settings.registry-mirrors` + sops PAT (nptest2) for upstream auth.
+  - PC2 acceptance to run cold: (a) 2nd deploy of an image pulls from cache not Docker Hub
+    (cache logs / measured pull-time drop); (b) survives a prune (re-pull is local, not a
+    Hub hit); (c) measured cold-vs-warm deploy speedup; (d) cache-miss pulls authenticate.
+- **PC3 / bounded+documented.** Cache must have disk cap / own GC (LRU/old eviction);
+  scope = docker.io only; docs/ notes cache+prune policy; deviations in DECISIONS.md.
+
+## Break-it probes to run once PC2 lands (anti-anchoring checklist)
+- Cache must NOT mask a genuinely-broken image pull (cardinal rule — don't weaken a test).
+  Probe: request a nonexistent/garbage tag through the mirror → must still FAIL, not serve stale.
+- registry-mirrors must be transparent to abra/swarm — verify a real abra deploy's pulls
+  traverse the cache with NO command change / no pull special-casing.
+- Cache survives a D8-style rebuild as a service (Nix-reconciled), but its contents are NOT
+  in the git closure (re-warmed by pulls) — verify both halves.
+- PAT secret must not leak into published logs / dashboard / world-readable registry config.