review(regression): A-reg-3 — bad-backup/bad-restore compose.yml empty (wrong tier fails); bad-install/bad-upgrade PASS cold-verified

machine-docs/BACKLOG-regression.md

@@ -44,6 +44,42 @@ cc-ci-run -m pytest tests/regression/ --collect-only
 
 ---
 
+### A-reg-3 [adversary] OPEN — CRITICAL: bad-backup and bad-restore fixtures broken (empty compose.yml)
+**Filed:** 2026-06-02T01:58Z
+**Severity:** CRITICAL — both fixtures fail at upgrade instead of their intended tier
+
+Cold-verified by inspecting `regression-bad-backup` and `regression-bad-restore` branches:
+```bash
+ssh cc-ci 'cd /root/.abra/recipes/custom-html && git diff origin/main..origin/regression-bad-backup -- compose.yml'
+```
+Result: compose.yml is completely empty (entire file deleted, leaving only a blank line). Same
+for `regression-bad-restore`.
+
+**Evidence from run artifacts:**
+- `regression-bad-backup-1`: `results: install=pass, upgrade=fail, backup=skip`
+  - Expected: `install=pass, upgrade=pass, backup=fail`
+  - Actual: upgrade fails because chaos deploy deploys empty compose → no service → deploy error
+- `regression-bad-restore-*`: never ran to completion (same root cause blocks it)
+
+**Impact on regression test assertions:**
+`_assert_red_at_tier` for bad-backup:
+- `failing_tier="backup"` → checks `results["backup"]="skip"` → FAIL: "expected 'backup'='fail', got 'skip'"
+- Test would FAIL with confusing assertion, not passing as expected
+
+**Fix:** Recreate both fixture branches with correct compose.yml that:
+- bad-backup: keeps full valid nginx service, only changes `backupbot.backup.path` label to `/nonexistent-cc-ci-canary-bad`
+- bad-restore: keeps full valid nginx service, changes backup scope to capture a subdir that doesn't contain ci-marker.txt (so restore doesn't recover the marker)
+
+The compose.yml should be identical to main EXCEPT for the single label/config change.
+
+**Repro:** `git diff origin/main..origin/regression-bad-backup -- compose.yml` → empty file
+
+**Adversary closes:** after both fixtures are recreated correctly, runs confirm:
+- bad-backup: `install=pass, upgrade=pass, backup=fail`
+- bad-restore: `install=pass, upgrade=pass, backup=pass, restore=fail` with `test_restore_returns_state` FAIL
+
+---
+
 ### A-reg-2 [adversary] OPEN — Plan gap: 4 per-tier RED canaries required by updated DoD
 **Filed:** 2026-06-02T01:37Z
 **Severity:** HIGH — DoD#4 unmet; Builder cannot claim DONE without these