recon(prevb): M1 code pre-review (sound; 63 prevb unit tests pass cold) + builder heads-up (pre-existing red test)

machine-docs/REVIEW-prevb.md

@@ -18,8 +18,39 @@ SSOT: `/srv/cc-ci/cc-ci-plan/plan-phase-prevb-previous-dynamic-base.md`.
   Facts CONFIRMED. (Caution noted: gitea `raw?ref=<shortsha>` silently falls back to default branch —
   must use the FULL sha when cold-verifying head content.) Foundation for "discourse needs no previous/" holds.
 
+## Pre-review (M1 code, gate NOT yet CLAIMED — preliminary recon, not a verdict)
+2026-06-17T00:30Z — studied the M1 `feat` commit bb2e3c6 (code/diff only, NOT JOURNAL). Design looks sound:
+- `resolve_upgrade_base` → BasePlan(kind, version, ref, reason): override → last-green (`canonical.read_registry`)
+  → main-tip (`recipe_branch_commit`) → skip. `.runs` gates the upgrade tier. head_ref = `recipe_head_commit`.
+- `previous/` surface (lifecycle): `has_previous`, `previous_target_version` (VERSION marker), `previous_status`
+  (version-guarded apply/stale), provide/remove overlay, compose_file add/remove. Base-only; **stripped before
+  head redeploy** (`generic.perform_upgrade` → `remove_previous_overlay` + COMPOSE_FILE strip). Good teeth.
+- discourse migrated: `compose.ccci.yml` now ENVIRONMENTAL-ONLY (`order: stop-first`); bitnamilegacy pins +
+  sidekiq + UPGRADE_BASE_VERSION **removed**. `test_upgrade.py` asserts running `app` image == official
+  `discourse/discourse:3.5.3` (not bitnamilegacy) + sidekiq gone; resolves as the upgrade-tier overlay
+  (`resolve_overlay_op`→`test_{op}.py`), run as its own pytest → rc!=0 fails the tier. Real teeth confirmed.
+- **Unit tests run cold (nix pytest): 63 passed** (test_upgrade_base + test_previous + test_meta). Matrix
+  EXPANDED, not weakened (override-wins / last-green-primary / main-tip-fallback / head==main-tip skip / no-pred skip).
+
+STILL REQUIRED for the formal M1 PASS (needs the Builder's e2e claim + my cold acceptance run):
+  (a) discourse upgrade tier GREEN locally with proof the head ran real 3.5.3 (not bitnamilegacy) + no sidekiq;
+  (b) BREAK-IT: a deliberately-broken head still fails the upgrade tier (base resolution didn't paper over it);
+  (c) base falls back to main when last-green absent (unit-covered; e2e desirable);
+  (d) `previous/` ignored for the head (code-confirmed; e2e desirable).
+
+## Adversary findings (pre-review notes)
+- [F-prevb-A] (PRE-EXISTING, NOT a prevb regression; INFO) `tests/unit/test_warm_reconcile.py::
+  test_traefik_spec_is_stateless_with_setup` is RED on main — `KeyError: 'health_domain'`. Fails identically at
+  the gtea-DONE commit 778720c (verified by checkout), and the prevb feat never touched warm_reconcile — the
+  `pxgate-M1` traefik-probe change (0e9fd38) refactored the spec without updating this test. Out of prevb scope,
+  but it means the FULL `tests/unit/` suite is NOT all-green (283 pass / 1 fail). Flagging so "unit green" claims
+  are scoped honestly. Not an M1 blocker.
+- [F-prevb-B] (NIT) old `test_expected_na_other_rung_does_not_suppress` was dropped in the rewrite; the behavior
+  (an EXPECTED_NA for a non-upgrade rung must not suppress the base) is preserved via `.get("upgrade")` but no
+  longer has a dedicated test. Low risk; consider re-adding one line of coverage.
+
 ## Verdicts
-(none yet)
+(none yet — awaiting M1 CLAIM with e2e evidence)
 
 ## Open VETOes
 (none)