review(regall): batches 5-6 verified; A-regall-2 filed for plausible backup_restore=fail

Batch 5 results:
- uptime-kuma (748): L5 all pass ✓
- lasuite-drive (749): L5 all pass ✓
- plausible (750): L2, backup_restore=FAIL — regression from baseline L5
  - ci_marker not found after restore; no-op upgrade (3.0.1+v2.0.0→3.0.1+v2.0.0)
  - Builder re-running as Drone 754

Batch 6 results:
- custom-html-tiny (752): L5, upgrade=pass, backup_restore=skip (expected) ✓
- bluesky-pds (753): L5, upgrade=skip (expected/EXPECTED_NA), backup_restore=pass ✓

A-regall-2: plausible backup_restore=fail — prevb regression or flake TBD.
Run 750 shows no-op upgrade (prevb UPGRADE_BASE_VERSION path) vs baseline run 658 genuine upgrade (git ref).
Same failure seen in m2r/m2rr-plausible during prevb development.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

machine-docs/BACKLOG-regall.md

@@ -40,6 +40,34 @@
 
 ## Adversary findings
 
+### A-regall-2 [adversary] OPEN @2026-06-17T03:25Z — plausible backup_restore=fail; classify prevb regression or flake
+
+**Filed:** 2026-06-17T03:25Z
+**Severity:** MEDIUM — backup_restore failure drops plausible from baseline L5 to L2. Blocks M1 classification.
+
+**Run:** 750 (Drone 750, PR#4). Result: level=2, backup_restore=fail.
+**Baseline:** run 658, level=5, backup_restore=pass.
+
+**Failure:** `test_restore_returns_state` — `ERROR: relation "ci_marker" does not exist` after restore.
+- Backup test passed (only checks artifact file exists, 0.134s — does NOT verify ci_marker content)
+- Restore completes (test_restore_healthy passes), but ci_marker table absent from DB
+
+**Prevb-specific difference:**
+- Run 750 upgrade: `version=3.0.1+v2.0.0→3.0.1+v2.0.0` (NO-OP: UPGRADE_BASE_VERSION='3.0.1+v2.0.0' matches recipe.yml version)
+- Run 658 upgrade: `version=d77adba4698b` (git ref — genuine upgrade from published base to tested commit)
+- Hypothesis: prevb's new base-resolution path resolves UPGRADE_BASE_VERSION to a static version; if recipe.yml also pins that same version, the upgrade is a no-op, which may change the DB state sequence enough to break backup/restore
+- Same failure pattern in m2r-plausible and m2rr-plausible (prevb development runs) — both level=2, backup_restore=fail
+
+**Builder rerun:** Drone 754 (triggered after 750 failed) — verdict pending.
+
+**Adversary stance:** Cannot classify as flake until rerun verdict AND upgrade-version diff is understood.
+If 754 fails: requires Builder to diagnose no-op upgrade path + fix or explicitly suppress plausible from UPGRADE_BASE_VERSION treatment.
+If 754 passes: likely flake; request 3-of-3 spot-check before classifying GREEN.
+
+**Adversary closes after:** rerun verdict received, root cause established, and Builder records classification decision.
+
+---
+
 ### A-regall-1 [adversary] CLOSED @2026-06-17T02:20Z — mailu baseline table corrected
 
 **CLOSED:** Builder corrected STATUS-regall.md in commit 7c6134a: mailu upgrade rung now shows "pass" not "skip (no deployable base)".