# REPORT — F-CRIT-1 + F-A1: one alarm that never fired, one that fired wrongly (v0.179.0) (2026-07-28)

**Overwritten** per the standing rule. Controller **v0.178.0 → v0.179.0**. Both Campaign 8 findings,
fixed together because both are "the alarm is wrong" and both live in `internal/quiesce` plus its
`classifyRunStates` consumer. No wire/contract change; no agent behaviour change (its 409 is correct
and was left alone — only a wrong comment there was corrected).

## Baselines (reconfirmed, not copied)
Controller `0.178.0` live on both boxes; agent `0.106.0`; `felhom-controller 8f46495`,
`felhom.eu d0cec9d`, `felhom-agent af1c21a`, all clean.

---

## F-CRIT-1 — a failed app restart never alarmed. Two independent causes.

### Cause 1 — the outcome was thrown away
`restartAll` returned nothing; a failed `StartStack` was logged and dropped on the spot, so no
caller could learn a customer's app had not come back. It now **returns the stacks that failed**, and
both call sites (the cycle's unquiesce and crash recovery) record the result via
`noteRestartOutcome`.

### Cause 2 — a documented invariant the quiesce path had made false
`classifyRunStates` whitelists `StateStopped` because v0.164.0 correctly refused to alarm on
deliberate user stops, resting on I1: *"StateStopped means deployed, deliberately stopped by the
user."* **The quiesce loop stops stacks by the same `docker compose down` path**, so a stack it
stopped and then failed to restart is also `StateStopped` — byte-identical on the Docker side — and
was whitelisted into total silence.

No state test can separate them; they *are* the same state. The distinguishing fact is that the loop
**tried to restart it and could not**, now surfaced by `Loop.FailedRestarts()`. That set is the only
thing that lifts the whitelist:

```go
userStopped := st.State == stacks.StateStopped && !failedRestart[st.Name]
down := stacks.IsDownState(st.State) && !userStopped && !quiesced[st.Name]
```

The flag is only ever consulted for an already-down stack, so a stale entry cannot manufacture an
alarm on a healthy app; it clears the moment a later restart of that stack succeeds.

### Why the existing tests missed it
R-97b's Scenario F asserted that **suppression expires**. It never asserted that **an alarm
follows**. Suppression lifted correctly and the whitelist ate the alarm one layer down — a green,
red-proofed suite over a production path broken two independent ways. That is why §5 exists.

---

## F-A1 — a correct refusal reported as a failure

HTTP 409 from `POST /backup` is the agent's R-85 single-flight gate refusing while a restore-test
holds it. The start path had no 409 branch, so it called `noteTierFailure`: breaker armed,
`whole_guest_backup_failed` emailed. At real cadences a ~12-minute restore-test against a daily
backup collides roughly once per 420 guest-days — about **every 4 days on a 100-guest fleet** —
training the operator to ignore the alarm and quietly undoing R-97a.

409 is now contention: `agentapi` returns a typed `*StatusError` on POST (it was `fmt.Errorf`, i.e.
string-only), the adapter maps 409 → `quiesce.ErrTierBusy` at the same seam that maps 404 →
`ErrTiersUnsupported`, and the loop defers. No breaker, no event, no email; the tier stays **DUE**.

### The two traps, and the bounds chosen

**Silence.** "Just ignore 409" would let a wedged restore-test block backups forever with nobody
told. So contention outliving **`contentionAlarmAfter` = 3h** raises its own signal, headlined
**BLOCKED**, not FAILED. The bound is set by the agent's own ceiling, not taste: its PBS restore-test
task is capped at **120 minutes** (`config.RestoreTestPBSRestoreTimeout`, default 120m), after which
the agent times out and releases the gate itself — so contention outliving that is a *stuck* gate,
not a busy one. 3h adds an hour of margin for teardown and 5-minute poll granularity, and is 15×
the longest contention actually observed (12m01s).

**App thrash.** Removing the failure treatment also removes the breaker's deferral, which had been
(accidentally) preventing a re-quiesce every 5 minutes. Without a replacement the customer's apps
would be stopped and restarted on **every poll** for the whole restore-test — worse than the bug. A
contended tier is therefore dropped from the due set **before anything stops**, on
**`contentionRetryAfter` = 15m** (longest observed restore-test 12m01s; the agent's local
restore-test wait is 10m), capping churn at 4/hour instead of 12/hour.

---

## Red-proofs — all six observed failing

| # | red-proof | observed failure |
|---|---|---|
| 1 | restore the unconditional `StateStopped` whitelist | `a stack that FAILED to restart is silent (Down=false) — this is F-CRIT-1` · `absent from the dashboard dead-list` |
| 2 | treat every `StateStopped` as a failed restart | `a deliberate user stop alarmed — that is the v0.164.0 regression this must not reintroduce` · `stopped alarmed with no failed restarts` |
| 3 | make `restartAll` drop its errors again | `restartAll returned [], want exactly [immich]` · `want immich to be recorded as a failed restart, got map[]` |
| 4 | remove the 409 branch | `runOnce: start backup on (untargeted): quiesce: tier busy — a concurrent heavy operation holds the agent: agentapi: POST /backup: HTTP 409` |
| 5 | treat all errors as contention | `breaker did not arm on a real 500 (failures=0) — a real 500 was swallowed as contention` · `operator was NOT notified of a real failure` |
| 6 | remove the contention alarm bound | `no alarm after 3h0m0s of unbroken contention — that is a silence path, the exact thing this fix must not create` |

`go build`, `go vet ./...`, `go test ./...` — all green, run separately from the commit.
(Red-proof 6 first produced a *compile* error, which is a weaker proof; it was redone so the code
compiles and the alarm simply never fires.)

---

## §5 — LIVE replay of BOTH findings on demo-hp, with the hub DB as arbiter

### F-CRIT-1
One image tag made unresolvable, then a normal quiesce:
```
06:54:30 unquiescing (snapshotted (early resume, last tier)): restarting 1 stack(s)
06:54:36 [ERROR] [quiesce] restart paperless-ngx: starting stack paperless-ngx: exit code 1
         containers: 0
```
| moment | result |
|---|---|
| during grace (06:54:59) | 0 events, 0 banner markers, 0 pushes — **suppressed** |
| grace expiry | 06:54:30 + 180s = **06:57:30** |
| **06:57:39** | `PushEvent: type=app_start_failed severity=warn` → hub `Event from demo-hp: app_start_failed` |
| dashboard | `alert-icon … Telepített alkalmazás nem fut: Paperless-ngx (stopped)` |

The banner names the `(stopped)` state explicitly — the whitelist was lifted, not bypassed. Nine
seconds after the window closed, on the first scan.

### Scenario B live — the inverse, same box
The app was restored to healthy, then stopped **deliberately** via the UI path:
```
containers after deliberate stop: 0     stack state: stopped
deadapp scans during the silent window: 9
app_start_failed events for demo-hp TODAY (events table) = 1     ← still just the failed restart
```
Same box, same `stopped` state, opposite outcomes — driven purely by whether the loop failed to
restart it. The 9 scans are the positive observable that the silence is suppression, not a dead
detector.

### F-A1
A restore-test was forced to hold the gate, then a backup triggered:
```
agent:      backup refused — a heavy operation is already in flight  busy=restore-test   (both tiers)
controller: tier local is BUSY — the agent refused ... This is contention, NOT a failure:
            the tier stays due and retries in 15m0s (contended for 0s)
controller: tier felhom-pbs is BUSY — ... same
controller: unquiescing (last tier is busy — deferring to a later cycle): restarting 1 stack(s)
```

### Scenario G live — the inverse, same box, same event type
A **real** transport failure (PBS path dropped at nft, not a 409):
```
07:41:47 [WARN] tier felhom-pbs: backup job ... failed
07:41:47 [WARN] tier felhom-pbs has now failed 1 time(s) in a row — deferring by 15m0s
07:41:47 [INFO] Event pushed: whole_guest_backup_failed (error) — Whole-guest backup FAILED on the felhom-pbs tier
```

### The hub DB, not the logs — the decisive numbers
| injection | `whole_guest_backup_failed` sent(operator), demo-hp |
|---|---|
| baseline before either replay | **8** |
| after the **409** contention replay | **8** — zero spurious emails |
| after the **real failure** (Scenario G) | **9** — fired 09:41:48 CEST |

Breaker arming lines since deploy: **0** for the 409, **1** for the real failure. Same box, same
day, same event type; the only difference is 409 versus a genuine error.

### Scenario F live
After contention cleared, the backup **ran and both tiers succeeded** (`tier local: done`,
`tier felhom-pbs: snapshotted`) — contention did not poison the tier. The armed breaker from
Scenario G was then cleared by a successful backup, with
`whole_guest_backup_recovered` emitted.

---

## Deployed & fleet state

`felhom-controller 0.179.0` on **demo-hp** and **demo-felhom**, both healthy. demo-felhom 15/15
containers, demo-hp 8/8, zero unhealthy, no nft leftovers, cadences untouched
(`local 0`, `rt 302400`, `felhom-pbs 604800`), agent `0.106.0` on both.

**demo-felhom had no injection and produced 0 event/alarm lines since its deploy** — the fix is not
chattering on an untouched box.

One leftover of my own making was cleaned up: Scenario G's block failed a restore-test mid-flight,
which leaked scratch guest `990000` — the already-filed F-LEAK/R-99 behaviour (a failed restore-test
cannot destroy its own scratch guest, 403 `VM.Allocate`). Destroyed; `pct list` shows only 9201.

## Comments corrected (three of the six catalogued)
- `classifyRunStates` I1 — now states what `StateStopped` actually means and names the quiesce path.
- `quiesce.go`'s "would record a spurious failure" — records that this was not hypothetical until now.
- agent `inflight.go`'s "a caller that cannot acquire DEFERS" — records that this was true of the
  restore-test caller and not the backup caller; fixed controller-side.

Standing rule added to **both** copies of `CLAUDE.md` (live + versioned): *a comment asserting an
invariant needs a test pinning it, or it is a wish*, with all six instances catalogued.

## NOT yet live-validated (carried forward, minus what this closes)
- Fault 4 — restic transport interruption; four injection approaches defeated by guest-bridged
  networking. **Still the most valuable follow-up**: F-CRIT-2 answered the phantom question for PBS
  and it remains open for restic.
- **R-99** — prune never removes phantom snapshots (no retention bug; they accumulate).
- **F-LEAK** — a failed restore-test cannot destroy its own scratch guest; observed again here.
- Fault 12 (host reboot mid-backup); the three-way backup+restore-test+GC overlap; the agent's DR
  bring-up path (`ModeDRGuestLoss`), still read-only-verified.
- `contentionAlarmAfter` (3h) itself — proven by unit test with an injected clock, **not** live; a
  live proof needs a gate wedged for three hours.
