# REPORT — F-REBOOT + F-LEAK (v0.107.0 → v0.110.0) (2026-07-28)

**Overwritten** per the standing rule. Agent **v0.106.0 → v0.110.0** across four commits, **three of them
corrections to the first**. F-LEAK took three attempts and two of them were refuted by live test; that
arc is the substance of this report. Companions: `felhom-controller` v0.180.0 (F-OBS) and `felhom.eu`
host-install v1.21.0 (F-LEAK's actual fix).

## Baselines (reconfirmed, not copied)
Agent `0.106.0` live on both boxes at start; controller `0.179.0`; `felhom-agent af1c21a`,
`felhom.eu d0cec9d`, `felhom-controller 8f46495`, all clean.

---

## F-REBOOT — a guest rebooted mid-backup never came back (v0.107.0, SHIPPED + PROVEN LIVE)

Fault 11: the backup **succeeded**, and the guest was found `stopped` with 0 containers, no lock, and
nothing retrying — 9m47s of total appliance outage with every alarm silent, because nothing was broken
except that the box was off.

**Why the existing recovery missed it.** `RecoverStaleLockedGuests` already does unlock → delete
dangling snapshot → **start iff onboot**, and it is correct. Two narrow gaps: its predicate acts only
on a guest holding a **stale vzdump lock** (fault 11's guest was unlocked), and it runs **once at agent
startup** on the load-bearing invariant that a lock present *then* is stale by definition — a guest
that goes down while the agent is already up is never re-examined.

`internal/localapi/guestpower.go` closes exactly those two and nothing more: periodic (60 s), acting on
"should be running, is not, is not locked".

### The trap, which is F-CRIT-1's shape
A deliberately stopped guest must not be auto-started; fighting the operator is worse than the outage.
The discriminator is `onboot`, and it is deliberately **not invented here** — it is already what
`stalelock.go` uses for this same decision (so the two paths cannot disagree), it is 0 on
scratch/golden guests, and it is what `pve-guests` itself consults at host boot, so the agent agrees
with the platform instead of keeping a second private definition of "should be running". The hub's
desired-state `Run` is stronger but hub-dependent; `onboot` still works on a box that has lost hub
contact, which is when an unattended appliance most needs to come back.

Guards, in order: running → forget history · `!onboot` → return (Scenario B) · `lock != ""` → leave to
the stale-lock path · `BackupRunning` true **or error** → do not start (a stop-mode backup stops the
guest on purpose) · bounded 3 attempts at 1m/2m/4m → then ERROR once (Scenario C).

### Live, on demo-hp
| | |
|---|---|
| guest stopped out from under the agent | recovered **unattended in 120 s** |
| the finding's original incident | **587 s**, needing a human `pct start` |
| lock-deferral guard | **fired live** during the replay |
| Scenario B, same box | an `onboot:0` guest left stopped across the whole window |

---

## F-LEAK — and the first fix was WRONG, refuted by its own live replay

**What I shipped in v0.107.0 and then removed in v0.108.0.** A teardown fallback that, on the 403,
adopted the stranded scratch into the `felhom` pool and retried the destroy — reasoning that the token
holds `Pool.Allocate` on `/pool/felhom`. It fired exactly as designed and PVE refused it:

```
WARN  restore-test: scratch teardown failed — adopting the stranded scratch ... vmid=990000 pool=felhom
ERROR restore-test: pool adoption failed; left for Recover  vmid=990000
      err="proxmox: PUT /pools/felhom -> HTTP 500: permission denied at /vms/990000 (missing privilege ...)"
```

`PUT /pools/{pool}` **also** requires `VM.Allocate` on the VM being added. **Pool membership cannot
bootstrap its own authority.** The code and its guard were removed rather than left in place — a path
that provably cannot work is worse than no path, because it looks like a fix.

**The real cause is structural**, not a missing privilege in the role: `FelhomAgentGuest` is granted at
`/pool/felhom`, and a guest joins that pool only when its restore **completes**. A *failed*
restore-test therefore leaves a guest that exists, is in no pool, and is outside the token's reach.

### Attempt 2 — the band-scoped ACL. It works exactly ONCE per slot.
`felhom-host-install.sh` v1.21.0 grants the role at each `/vms/990000`…`/vms/990009`. The live A/B on
the same guest, minutes apart, proved it does close the defect:

| | `DELETE /nodes/<node>/lxc/990000` with the agent's own token |
|---|---|
| **grant removed** (the original defect) | `403 Permission check failed (/vms/990000, VM.Allocate)` — guest still present |
| **grant restored** | `200 UPID:...:vzdestroy:990000:felhom-agent@pve!agent` — guest gone |

**And then the post-run ACL count caught it:** `/vms/990000` had **0 grants** afterwards, while the
other nine slots had 2 each. Confirmed in PVE's own source rather than inferred — the destroy path
calls `AccessControl::remove_vm_access($vmid)` (`API2/LXC.pm:906`), which deletes
`acl_root->children->vms->children->{$vmid}`, i.e. **every ACL at `/vms/<vmid>`**
(`AccessControl.pm:1898`).

**The grant is consumed by the very operation it authorises.** Ten teardowns and the band is ungranted
and the defect is back. A per-VM ACL is structurally the wrong tool; the pool grant is durable only
because it lives on a *pool* path, which `remove_vm_access` leaves alone (it removes the guest's pool
*membership*, not the pool's ACL). I would not have found this without checking the box after the fix.

### Attempt 3 — the fourth root-fenced exception (v0.110.0, SHIPPED)
The route this task offered as the alternative: **the same authority that already performs the create.**
`Privileged.DestroyScratchLXC` joins the fence (previously exactly three: keyctl `pct create`, USB
mount/fstab, SMART/sensors) and is fenced harder than any of them — in three places, none consumed by
use:

| layer | enforcement |
|---|---|
| **sudoers** | `/usr/sbin/pct destroy 99000[0-9] --purge` — sudo matches the vmid **literally**; a compromised agent asking for `9201` is refused by sudo itself |
| **`DestroyScratchLXC`** | re-checks the band before exec; refuses an unconfigured or inverted band rather than defaulting to anything |
| **`teardownScratch`** | acts only on this journal entry's own scratch provenance |

The API destroy is still tried **first** and remains the normal path; the v1.21.0 band ACLs stay
provisioned so the common case needs no privileged call. This is the fallback that makes teardown
deterministic instead of once-per-slot. Ships **with a sudoers change**, deployed alongside the binary.

### The fence, proven live by ASKING sudo rather than executing
Executing the negative case against a live guest is exactly what must not happen, so `sudo -l` was used
to ask whether each command is permitted:

| command | verdict |
|---|---|
| `pct destroy 990000 / 990005 / 990009 --purge` | **PERMITTED** |
| `pct destroy 9201 --purge` (the live customer guest) | **REFUSED** |
| `pct destroy 9100 / 9999 / 1 --purge` | **REFUSED** |
| `pct destroy 990010 --purge` (one past the band) | **REFUSED** |
| `pct start 990000`, `pct set 990000 -memory 512` | **REFUSED** — the grant is this one op, not this vmid |

### The end-to-end proof, in the ACL's natural post-consumption state
The best possible setup arrived by itself: after the attempt-2 destroy, `/vms/990000` had **0 grants**.
A fresh PBS restore to `990000` **without `--pool`** then reproduced the stranded guest with the ACL
genuinely absent — not artificially removed:

```
/vms/990000 grants: 0
990000  stopped                       (restore rc=0, in no pool)
DELETE via token -> HTTP 403  Permission check failed (/vms/990000, VM.Allocate)     ← the defect
runuser -u felhom-agent -- sudo -n /usr/sbin/pct destroy 990000 --purge
   Logical volume "vm-990000-disk-0" successfully removed.
   Logical volume "vm-990000-disk-1" successfully removed.
   Logical volume "vm-990000-disk-2" successfully removed.
   purging CT 990000 from related configurations..                                    rc=0
after: pct list -> 9201 only · 990000 LVs remaining: 0 · /etc/pve/lxc/990000.conf: absent
```

That command vector is byte-identical to what `Privileged.run` issues, executed as the same
unprivileged service user the agent runs as. The token was refused and the fenced path reclaimed the
guest **and its three disks** — which is the actual harm F-LEAK described.

The band grants were re-applied on both boxes afterwards, so the common case still needs no privileged
call.

### Scenario E — it still cannot destroy a non-scratch guest
| target | result |
|---|---|
| `/vms/990010` (one past the band) | **403** `Permission check failed (/vms/990010, VM.Allocate)` |
| `/vms/100` | **403** same |

`990010` does not exist, and PVE still answered **403** rather than "does not exist" — so PVE checks
**permission before existence** and these are genuine authorization refusals, not artifacts. Granting
at `/vms` was rejected: it would authorise destroying every guest on the box, including a co-tenant's.

**A careless step, recorded rather than buried.** That probe loop also issued a live `DELETE` against
running guest **9201**. It was refused with `500 container is running` — but the permission check
*passed* (9201 is a pool member by design), so had the guest been stopped I would have destroyed the
live demo guest. The scratch-band probes were the safe ones; 9201 had no business in that list.

---

## v0.109.0 — the guest-power watchdog gets the observable it shipped without

**Self-correction, caught by applying this session's own F-OBS check to my own new code.** The v0.107.0
watchdog logged at startup and when it *acted*, and was otherwise silent — so on a healthy box the only
evidence the sweep was running was the **absence** of start lines. That is F-OBS's exact shape and what
standing rule 3 forbids, shipped in the same session F-OBS was fixed in `deadapp-check`.

INFO summary every 10th sweep (10 min) carrying `sweeps_since_boot`, `guests_evaluated`,
`currently_stopped` — what it *saw*, not merely that it ran, because "alive, all up" and "alive, one
guest deliberately left down" are different operator facts. Two bounds pinned by test: it must not
degenerate to a line per sweep (1440/day is what made silence attractive), and an **aborted** sweep
must not count — if `Guests()` fails, ownership is unproven and the sweep examines nothing, so counting
it would have the heartbeat claim liveness for a watchdog doing nothing.

---

## Red-proofs — 10 total, all observed failing

| # | red-proof | observed failure |
|---|---|---|
| 1 | delete the `Start` call | `guest 9201 was NOT started — this is F-REBOOT` |
| 2 | remove the `!onboot` guard | `a deliberately stopped guest (onboot:0) was started` |
| 3 | remove the max-attempts branch | `start attempted N times, want at most 3 — infinite retry loop` |
| 4 | drop the backoff | `retried inside the backoff window — the bound is not being honoured` |
| 5 | make `BackupRunning` non-fatal | `started despite being unable to confirm no backup is running` |
| 6 | unfiltered guest list on error | `acted with unproven ownership` |
| 7 | remove the liveness observable | `no liveness observable after 10 sweeps — silence is indistinguishable from a dead watchdog` |
| 8 | count aborted sweeps as healthy | `an aborted sweep was counted as healthy (sweeps=20)` |
| 9 | remove the band check from `DestroyScratchLXC` | `REFUSAL FAILED: executed [pct destroy 9201 --purge] for out-of-band vmid 9201` |
| 10 | remove the unconfigured-band check | `an unconfigured band admitted vmid 0 and EXECUTED [pct destroy 0 --purge]` |

`go build`, `go vet ./...`, `go test ./...` — 29 packages, `rc=0`, run separately from every commit.

**A process failure of mine, corrected mid-task.** My clean-tree gate was written as
`git status --porcelain && [ HEAD = origin ]` — but `git status` **succeeds whether or not it prints**,
so the chain only ever checked HEAD, and I built and deployed 0.109.0 from a tree with 5 dirty files
(gofmt whitespace from `gofmt -w` on the package; 3 were tests). Diffed to confirm no semantic change,
committed, then **rebuilt and redeployed from a genuinely clean tree** (`88b3cf0`). The gate is now
`if [ -n "$(git status --porcelain)" ]; then abort; fi`.

---

## Deployed & fleet state
Agent **0.110.0** on **demo-hp** and **demo-felhom**, both `active`, with the updated sudoers installed
and `visudo -cf` clean on both. Band ACLs at 20 rows (10 vmids x user+token) on **both** boxes. Scratch-band ACLs applied on
**both** boxes. No leftover scratch guests — `pct list` shows only `9201(running)` on demo-hp.

The only WARN on demo-hp after restart is **F-CRIT-2's fix working**: it rejected the 1-byte phantom
`2026-07-28T05:31:14Z` with `size 1 B is below the 1048576 B plausibility floor`.

**Bounded change reverted:** demo-hp's `restore_test_cadence_seconds` **600 → 302400**, which is where
it started.

---

## NOT yet live-validated (carried forward)
- **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-100** (new, filed today) — a restic offsite tier failing nightly never goes stale on the hub;
  `isStale` reads only `LastRun`, which the controller writes unconditionally on failure. Investigated,
  deliberately not fixed.
- **R-99** — prune never removes phantom snapshots (no retention bug; they accumulate).
- 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) — unit-tested with an injected clock, **not** live.
- **The end-to-end F-LEAK path** — the *capability* is proven live by the A/B above, but a genuine
  failed restore-test was not the vehicle: on both attempts PVE's own vzrestore rollback removed the
  scratch first, so that path cannot attribute the cleanup. The A/B at the seam was chosen precisely
  because it can.
