# SPIKE R-117 — a dead bind that reports healthy

**Class: Spike. No production code was written; no `.go` file in either repo was modified.**
Output is this document. Findings are filed as `R-n`, none fixed.

---

## 0. Verdict, up front

| # | Question | Answer |
|---|---|---|
| Q1 | Reproduce deliberately | **YES — 3/3 attempts, two independent device classes.** A device-node change is **NOT a precondition — it is a CONSEQUENCE** of the stale bind, proven by a control test |
| Q2 | What is dead, at which layer | The **guest bind and the host bind** (same mount, one peer group); the **raw host mount is healthy on the new device**. **Two distinct death states** with different errnos — `EIO`(5) both directions, and `EROFS`(30) on write only |
| Q3 | Why `boundUnderParent` returns true | It is a **string comparison of field 5 of a mountinfo line**. It never touches the filesystem, and **neither half reads field 3 (the device number)** — so neither can see that the two entries name different devices |
| Q4 | Cost + failure modes of a real check | A **pure-`/proc` check costs 0.16–0.45 ms, cannot hang, cannot spin up a disk and writes nothing.** The two cheapest *I/O* probes — `statfs` and `getdents` — **succeed over a fully dead filesystem** and are worthless. **Every probe that reaches the device blocks on a wedged one, and the process then cannot be killed even with `SIGKILL`** (§6.3) |
| Q5 | Where the check belongs | **The agent**, and not on balance — the controller **cannot** perform it: the inputs are host mount tables it has no access to |
| Q6 | In-place recovery possible | **YES — proven, guest never restarted** (init PID identical across the repair). And **the repair code already exists, is already invoked at exactly the right moment, and is short-circuited by the same false predicate** |
| Q7 | Scope — steady state too? | **YES, and this is the worse half.** A drive can die **with no detach/return cycle at all**; the gate then never runs, the `Return` branch never fires, and **no event of any kind is emitted** |

**The single most consequential finding is Q7.** R-117 was filed as a defect in the reattach path. It is
not confined to it: a device that fails **in place** produces the identical all-signals-healthy state
with no gate transition to hang a fix on. A fix that lives in the `Return` branch closes the half that
at least emits events, and leaves the silent half open.

**The second is Q6.** `AttachDrive`'s normalize leg (`intermediary.go:238-247`) already performs exactly
the repair this defect needs — `umount` every layer, lay down one fresh bind — the controller's `Return`
branch already asks the agent to do it (`controller/internal/web/intermediary.go:301-305`) **before** it
restarts the apps, and the agent's 20-second reconcile ticker (`cmd/felhom-agent/main.go:973-985`) calls
it unconditionally. All three are defeated by one line: `if n == 1 && b.GuestSeesMount(...)` returns
early (`intermediary.go:235`). **Making the predicate honest turns three already-wired call sites into a
self-heal.** That is the cheapest fix available and it is not the one a fresh design would have reached.

---

## 1. Confirmed baselines

Established fresh this run, not carried.

| Component | Version | Source |
|---|---|---|
| `felhom-agent` `main` | **v0.116.0** @ `d4eb259da241c4ae2af81d5dff6a51b86c411b42` | `git -C felhom-agent log`, `CHANGELOG.md:1` |
| `felhom-controller` `main` | **v0.186.0** @ `b331f18` | `git log`, CHANGELOG head |
| `felhom.eu` `main` HEAD | `29bcfeb` *(docs(R-120): CLOSED on both halves)* | `git log` |
| hub, **live** | **0.82.0** (`gitea.dooplex.hu/admin/felhom-hub:0.82.0`) | `kubectl -n felhom-system get deploy` |
| golden | **0.186.0** | `OPEN-ITEMS.md` R-120 row (rebaked + vouched 2026-07-30) |
| demo-hp PVE | `pve-manager/9.2.2/b9984c6d90a4bd80`, kernel `7.0.2-6-pve` | `pveversion` |
| **demo-hp agent, live** | **0.113.0** | `felhom-agent --version` on the box |

> **The live agent on the venue is 0.113.0 — three releases behind `main` (0.116.0) and behind R-113
> (0.114.0), the very conjunction under examination.** It equals the manifest's `MinAgent`, so it is the
> fleet's declared minimum, not drift. **It was therefore never used as the source of a behavioural
> claim.** Every predicate result in this document comes from a probe built from `main`
> @ `d4eb259` (§2.3), not from the installed agent — precisely the "do not silently reason about a
> different codebase" rule in the brief.

---

## 2. Venue

### 2.1 The named venue does not exist — recorded, not worked around

The brief specifies *"the standing snapshot-reset fixture on demo-hp, reset to `virgin` first"*.
**There is no such fixture on demo-hp.** Enumerated on the box:

```
pct list  ->  9201 running demo-hp          (FENCED by the brief)
qm list   ->  300  stopped drill-r50        (FENCED by the brief; the only drift fixture, R-93)
```

The only standing snapshot-reset fixture in the estate is the **nested-PVE golden-bake VM on DooPlex**
(`drill/drill.qcow2`, snapshot `virgin`) — a **Tier 2** machine, and
`runbooks/target-selection.md:56-61` states that using it as a drill victim "is not covered by that
exception and contradicts the 2026-07-25 ruling". So the two candidate venues were, respectively,
absent and prohibited.

**Resolution: the venue named by the brief (demo-hp) was kept and the *fixture* premise corrected.** A
purpose-built **scratch LXC guest (VMID 9301)** was created on demo-hp — Tier 1 on a Tier 0 host, which
`target-selection.md:83-87` permits as "create and destroy freely". This is a **mechanism** claim, so
per `target-selection.md:89-104` a fixture is the correct instrument and a day-0 would have been waste.

### 2.2 Fixture provenance — recorded per `target-selection.md:101`

Built **2026-07-30 11:18–11:24 CEST**, from scratch, this session. Nothing about it is of unknown
vintage:

| | |
|---|---|
| Guest | LXC **9301**, unprivileged, 256 MB / 1 core, **no network interface at all** |
| Template | `debian-13-standard_13.6-1_amd64.tar.zst`, downloaded this run, **checksum verified by `pveam`** |
| rootfs | **2 GB raw on a scratch dir storage `r117scratch`** at `/var/lib/vz/r117-scratch` — created for this run. **Never `local-lvm`** (fenced: over-subscribed thin pool backing live 9201) and **never `felhom-backup`** (the box's backup target) |
| Host | demo-hp, PVE 9.2.2, kernel 7.0.2-6-pve |
| Agent / controller **inside** it | **none** — see §2.4 |

### 2.3 What actually evaluated the predicates

A throwaway probe, `r117probe`, **outside both repos**, which calls the **real exported agent code**:

- The agent tree was exported at `HEAD` (`git archive d4eb259`) into the session scratchpad and the
  probe added there as `cmd/r117probe`. **`git status` against that worktree, excluding the probe dir,
  is empty** — the copy is byte-identical to `main`. Neither repo was touched. (Direct cross-module
  import is impossible: `internal/...` is unimportable from another module.)
- `HALF1` is a **real call** to `localapi.GuestBinder.GuestSeesMount` (`intermediary.go:276`) through a
  real `proxmox.ExecRunner`, so the real `lxc-info` lookup and the real mountinfo parse both run.
- `HALF2` is a **verbatim copy** of `isHostMountpoint` (`intermediary.go:394`) — the implementation
  behind `devicePresent` (`disks.go:972`), which is unexported. The copy is quoted against the original
  in §5.2; it is 12 lines with no branching beyond the field-count guard.

### 2.4 Fidelity gaps — stated, not glossed

| Gap | Consequence |
|---|---|
| **No agent daemon and no controller ran in the venue.** | No fresh `/disks` payload and no fresh controller gate log were captured this run. **Not a hole in the evidence:** `/disks` in all three states was captured verbatim **twice on real hardware** (`DIAG-r116-disks-payload-2026-07-30.md` §11; `R116-v0116-2026-07-30.md` §5), and the gate log four times. What was missing from that record was the *layer beneath* it — the mount tables and the errnos — which is what this run supplies |
| The dm-based drive (§3.2 drive A) could not have its device node **removed** while mounted | Only affects drive A. Drive B used `scsi_debug`, whose gendisk **can** be deleted while mounted — real USB-pull semantics — and it is drive B that carries the headline reproduction |
| One step on drive A was **modelled**: `systemctl stop` of the raw mount unit stood in for systemd reacting to device loss | **Superseded by measurement.** On drive B the real device deletion made systemd stop the raw mount unit **on its own** (`mnt-r117sd.mount` → `inactive`, §3.3), confirming the `BindsTo=` mechanism empirically. The modelled step is not load-bearing for any conclusion |

### 2.5 Two internet outages at the venue site

The venue is at the operator's vacation location until ~08-02; both demo boxes share one uplink.

- **Outage 1, ~11:07–11:13 CEST.** Both boxes went dark together. Four routes tried before concluding
  (standing rule 2): DooPlex→tailnet (`100.76.96.79`, `100.70.170.35`) timeout, with
  `tailscale status` reporting *both* peers `offline, last seen 7m ago`; DooPlex→LAN
  (`192.168.0.87`, `192.168.0.162`) down; `demo-hp-lan` via `ProxyJump felhom-pve` timeout;
  **ep0→WireGuard** (`ssh root@167.233.158.164` → `10.77.0.3`, `10.77.0.2`) ping down and ports 22 and
  **8822** both closed, with ep0's own `wg show` putting the last handshake at ~5 minutes prior.
  Cause confirmed by the operator: house internet. **demo-hp's `uptime` afterwards read `up 6 days`** —
  the box never rebooted, so the 124 MB template download running at the time did not destabilise it.
- **Outage 2, from ~11:27 CEST.** Interrupted the run **after** all of Q1/Q2/Q3/Q6/Q7 and most of Q4
  were captured, and **before** the Q4 hang measurement (§6.3) and teardown (§10).

---

## 3. Q1 — reproducing it deliberately

**Reproduced 3/3 attempts.** Two device classes were used deliberately, because they fail differently
and the difference turned out to matter.

### 3.1 Topology, faithful to the intermediary model

Built by hand to match `intermediary.go:11-19` and `:26-42`:

- scratch **shared parent** `/mnt/r117-drives` — self-bind, `--make-private`, `--make-shared`, the
  verbatim logic of `sharedParentScript`. **Deliberately NOT the live `/mnt/felhom-drives`**, whose peer
  group belongs to guest 9201.
- the guest's **permanent parent bind**, set before first start:
  `pct set 9301 -mp0 /mnt/r117-drives,mp=/mnt/r117-drives`.
- per drive: raw host mount at `/mnt/<name>`, namespace `<raw>/felhom-data` chowned `100000:100000`,
  bound to `/mnt/r117-drives/<name>`.
- raw mounts keyed by **fs-UUID**, matching `internal/storage/mountunit.go:51`
  (`What=/dev/disk/by-uuid/<UUID>`) — the detail that makes the host side heal onto a new device node.

Propagation verified correct before any test — the guest's parent bind is a **slave** of the host's
shared peer group:

```
guest: 1176 1175 252:1 /mnt/r117-drives /mnt/r117-drives rw,relatime shared:428 master:196 - ext4 ...
                                                                                 ^^^^^^^^^^
```

### 3.2 The two drives

| | Drive A | Drive B |
|---|---|---|
| Stack | file → `loop0` → **dm-linear** | **`scsi_debug`** (`dev_size_mb=64`) |
| Appears as | `/dev/mapper/r117cel`, **252:11** | **`/dev/sdb`, 8:16** |
| Death mechanism | swap the dm table to an **`error`** target | `echo 1 > /sys/block/sdb/device/delete` — **real gendisk removal while mounted** |
| Models | a device that **errors in place** | a device that is **pulled** |

### 3.3 The cycle, on drive B — the headline reproduction

```
HEALTHY        host raw   /mnt/r117sd        -> /dev/sdb  8:16  rw,stripe=512
               host bind  /mnt/r117-drives/sd -> /dev/sdb  8:16  rw,stripe=512
               guest bind /mnt/r117-drives/sd -> /dev/sdb  8:16  rw,stripe=512   master:450

PULL           echo 1 > /sys/block/sdb/device/delete
               /dev/sdb            -> No such file or directory
               mnt-r117sd.mount    -> inactive          <-- systemd stopped it ITSELF (BindsTo=)

ABSENT         host raw   /mnt/r117sd         -> NOT A MOUNTPOINT
               host bind  /mnt/r117-drives/sd -> /dev/sdb 8:16 rw,relatime,stripe=512,shutdown
               ==> BoundUnderParent = FALSE   (HALF1 true, HALF2 false)   <-- R-113 works here

RETURN         echo '- - -' > /sys/class/scsi_host/host1/scan
               returned as /dev/sdc  devno=8:32
               by-uuid/71e155fc-... -> /dev/sdc          <-- the UUID-keyed unit heals onto the new node

R-117          host raw   /mnt/r117sd         -> /dev/sdc  8:32  rw,stripe=512          [HEALTHY]
               host bind  /mnt/r117-drives/sd -> /dev/sdb  8:16  ...,shutdown           [DEAD]
               guest bind /mnt/r117-drives/sd -> /dev/sdb  8:16  ...,shutdown           [DEAD]
               ==> BoundUnderParent = TRUE
```

This is **byte-for-byte the state reported three times as cosmetic** — a drive back on `sdc` while
`findmnt` still reads `sdb[/felhom-data]`, with `shutdown` in the options.

### 3.4 The node change is a CONSEQUENCE, not a precondition — control test

The brief asks whether the defect *requires* `sdb`→`sdc`. It does not require it; **it causes it.**

```
with the stale bind still held:
  8:16 in /proc/partitions        -> 0        (the gendisk is gone)
  8:16 in /proc/self/mountinfo    -> 1        (the stale bind still references its superblock)
  device returns as               -> /dev/sdc  8:32      <-- NEW devno

after releasing the stale bind (umount), same pull + rescan:
  device returns as               -> /dev/sdb  8:16      <-- letter REUSED
```

The stale bind pins the dead superblock, which keeps the old device index allocated, which **forces the
returning device onto a different number.** The same effect appeared independently on drive A:
`dmsetup remove --force r117cel` failed with **`Device or resource busy`** — held open by the stale bind
alone.

> **Consequence for any fix: a device-number comparison is not a heuristic for the return case, it is
> sound.** Whenever a stale bind exists, the numbers differ *because* it exists. Stated as measured
> here, twice, on two device classes — not as a kernel guarantee quoted from documentation.

**Reliability: 3/3.** Two full detach/return cycles (drives A and B) and one in-place failure (§9), each
producing `BoundUnderParent = true` over a non-functioning namespace on the first attempt. No flakiness
observed; nothing was retried.

---

## 4. Q2 — what exactly is dead, and at which layer

**Dead: the bind.** The host bind and the guest bind are the same mount in one peer group, so they die
together and identically. **Alive and correct: the raw host mount**, re-mounted by fs-UUID on the new
device. The two disagree, and nothing compares them.

**There are two death states, and they present differently.** This matters more than it looks: a probe
tuned to one misses the other.

| | **(a) device removed** (drive B / real pull) | **(b) device errors in place** (drive A) |
|---|---|---|
| super options gain | **`shutdown`** | **`emergency_ro`** |
| guest `statfs` | **OK** | **OK** |
| guest `listdir` | **OK** | **OK** |
| guest read file content | **`errno=5 EIO`** | OK *(page cache)* |
| guest write | **`errno=5 EIO`** | **`errno=30 EROFS`** |
| host read via bind | **`errno=5 EIO`** | OK *(page cache)* |
| host write via bind | **`errno=5 EIO`** | **`errno=30 EROFS`** |
| host raw mount | not a mountpoint → then healthy on the **new** node | **stays mounted throughout** |
| `BoundUnderParent` | `false` while absent → **`true`** after return | **`true` the entire time** |

Errnos are numeric, from `os.statvfs` / `os.listdir` / `open` inside the guest via `pct exec python3`
and on the host, in the same capture.

Two consequences worth stating plainly:

1. **`statfs` and `listdir` succeed on a filesystem that returns `EIO` for every byte of content.** They
   are answered from the in-memory superblock and the dentry cache. Any liveness probe built on either
   is **hollow by construction** — it reports healthy in exactly the state it exists to detect.
2. **The host-side raw mount is genuinely fine.** The device is present, readable and writable at
   `/mnt/<name>`. Nothing is wrong with the drive. The damage is confined to the namespace the customer's
   apps actually use.

### 4.1 The brief's "materially worse" case — answered: no

The brief asks whether the host mount points at a device node *now belonging to a different device*. **It
does not.** In every state captured, the raw mount resolved through `/dev/disk/by-uuid/<UUID>` to the
correct returning device (`by-uuid/71e155fc-... -> /dev/sdc`), because the unit is keyed by filesystem
UUID (`mountunit.go:51`) and not by node. **The stale reference is held by the *bind*, which names the
old device — and it points at a dead superblock, not at a live foreign one.** No cross-device
mis-identification was observed or is structurally possible on this path.

---

## 5. Q3 — why `boundUnderParent` returns true

**Because neither half of the conjunction looks at which device the mount is on.** Both are presence
tests on a *path string*.

### 5.1 The conjunction

`disks.go:222` (Observe path) and `disks.go:358` (registry path), identically:

```go
di.BoundUnderParent = s.boundUnderParent(r.Context(), vmid, gp) &&
    s.devicePresent(t.MountPath)
```

### 5.2 Half 1 — `GuestSeesMount`

`disks.go:949` → `boundUnderParent` → `s.guestAttach.GuestSeesMount(ctx, vmid, stablePath)` →
`intermediary.go:276`:

```go
data, err := os.ReadFile("/proc/" + pid + "/mountinfo")
...
for _, line := range strings.Split(string(data), "\n") {
    f := strings.Fields(line)
    if len(f) >= 5 && f[4] == path {
        return true
    }
}
```

Half 2 — `devicePresent` (`disks.go:972`) → `isHostMountpoint` (`intermediary.go:394`) — is the same
test against `/proc/self/mountinfo` for the **raw** path:

```go
fields := strings.Fields(sc.Text())
if len(fields) >= 5 && fields[4] == path {
    return true
}
```

**`f[4]` is the mount point. `f[2]` — the `major:minor` of the backing device — is never read by either
function.** The information that settles the question is present in the very lines both functions
already parse, one field away, and is discarded.

Measured in the R-117 state, drive B:

```
HALF1  GuestSeesMount(9301, /mnt/r117-drives/sd) = true    [4.643178ms]   <- REAL agent code
HALF2  isHostMountpoint(/mnt/r117sd)             = true    [261.419µs]
=====> BoundUnderParent (disks.go:222 conjunction) = true

host  raw   : 814 33 8:32 /            /mnt/r117sd         ... - ext4 /dev/sdc rw,stripe=512
host  bind  : 755 118 8:16 /felhom-data /mnt/r117-drives/sd ... - ext4 /dev/sdb rw,stripe=512,shutdown
guest bind  : 759 1176 8:16 /felhom-data /mnt/r117-drives/sd ... - ext4 /dev/sdb rw,stripe=512,shutdown
                    ^^^^
```

Half 1 is satisfied by the **stale** entry; half 2 by the **new** device. Exactly as `OPEN-ITEMS.md`
predicted: neither half compares the two. **Confirmed, not inferred.**

### 5.3 This is a gap, not a false invariant — and the doc comment is the reason it survived

`disks.go:155-165` claims only the two cases the R-113 conjunction does fix (the boot-ordering window,
and a bind outliving its device *while still absent*). It does **not** claim staleness after a return, so
per the workspace rule this is a genuine gap rather than a seventh shipped false guarantee.

But the *summary line* is a wish:

> `// BoundUnderParent reports whether the drive is live + usable in the guest in the intermediary model.`

**Measured: it reports neither.** In the R-117 state the drive is not live in the guest and not usable —
every content read and every write returns `EIO` — and the field reads `true`. The interface comment at
`disks.go:154-155` makes the same promise (*"the guest-usable signal — distinct from the host having the
bind"*), and `disks.go:83` a third time. Three statements of a property nothing tests. **Per the standing
rule, whichever fix lands owes a test that pins the consequence** — that a dead namespace reports
`BoundUnderParent = false` — and not merely the mechanism.

---

## 6. Q4 — what a reliable check costs, and how it fails

All timings from the R-117 state on drive B, on the venue, one run each, `-timeout 3s`.

### 6.1 Measured

| Probe | What it does | R-117 state (B) | in-place state (A) | healthy | Cost | Verdict |
|---|---|---|---|---|---|---|
| **P1 devno compare** | field 3 of the bind's mountinfo line vs field 3 of the raw mount's — **pure `/proc`, host-side only** | **STALE=true** ✅ | STALE=**false** ❌ | false ✅ | **0.38–0.45 ms** | **Sound for the return case (§3.4). Blind to in-place death** |
| **P2 ext4 abort options** | `shutdown` **or** `emergency_ro` in the super options — **pure `/proc`** | **DEAD=true** ✅ | **DEAD=true** ✅ | false ✅ | **0.17–0.24 ms** | **Catches both.** ext4-specific |
| P3 `statfs` | one syscall | **OK — MISSES IT** ❌ | OK — misses ❌ | OK | 0.042 ms | **Worthless** |
| P4 `getdents` | read one dir entry | **OK — MISSES IT** ❌ | OK — misses ❌ | OK | 0.045–0.061 ms | **Worthless** |
| P5 write + unlink | create, write 1 byte, remove | `EIO`(5) ✅ | `EROFS`(30) ✅ | OK | 0.042–0.152 ms | Catches both, **but writes**, cannot distinguish a legitimately-`ro` mount from a dead one, **and BLOCKS on a wedged device** (§6.3) |
| P6 write + **fsync** | forces the byte to the device | — | — | OK, **11.4 ms** | **11.4 ms healthy** | **BLOCKS on a wedged device.** 25–70× the `/proc` probes even when healthy, on a loop device with no seek cost |
| P7 read with page cache dropped (`POSIX_FADV_DONTNEED`) | forces a read to reach the device | — | — | OK, 0.18 ms | 0.18 ms | **BLOCKS on a wedged device** |

`GuestSeesMount` itself costs **3.85–5.03 ms**, an order of magnitude more than any probe above,
because it forks `lxc-info`. **Any of P1/P2 is free relative to the check it would strengthen.**

### 6.2 The failure modes the brief named, answered from measurement

- **"A write probe fails wrongly on a legitimately read-only mount."** Confirmed as a real hazard, and
  worse than stated: in the in-place death state the mount *is* read-only (`emergency_ro`) and P5's
  `EROFS` is indistinguishable from an intentionally `ro` mount by errno alone. **P5 cannot be the sole
  signal.**
- **"A read probe on an empty drive has nothing to read."** Real, and it has a second and larger
  problem: **a read probe passes from page cache over a dead filesystem** (P4 succeeded in every dead
  state). Honest read probing requires dropping the cache first (P7), which converts it into a probe
  that must reach the device — i.e. one that can block.
- **"Spinning up a sleeping disk on every poll has a real hardware cost."** **P1 and P2 eliminate this
  concern entirely**: they read `/proc` and issue no block I/O, so a spun-down drive stays spun down.
  This is the strongest argument for the pure-`/proc` pair over anything else, independent of the hang
  question.

### 6.3 The hang case — MEASURED, and it is worse than "a probe that hangs"

Venue: the `dm-linear` drive suspended with `dmsetup suspend --noflush --nolockfs`, which **queues all
I/O indefinitely instead of returning `EIO`** — the controlled "half-dead or spun-down device" the brief
asks about. Verified suspended (`dmsetup info -o attr` → `L-sw`, the `s`), then the full probe set with
`-timeout 3s`, then `dmsetup resume`.

```
=== PROBES against a WEDGED (not erroring) device, timeout 3s ===
HALF1  GuestSeesMount = true    [3.983519ms]
HALF2  isHostMountpoint = true  [234.181µs]
=====> BoundUnderParent = true
P1 devno-compare   raw="252:12" bind="252:12" -> STALE=false  [363.878µs]   <-- COMPLETED
P2 ext4-abort-opts superopts="rw" -> DEAD=false               [206.104µs]   <-- COMPLETED
P3 statfs        COMPLETED in 40µs   err=<nil>                              <-- reports HEALTHY
P4 getdents      COMPLETED in 64µs   err=<nil>                              <-- reports HEALTHY
P6 write+fsync   TIMED OUT after 3.002s — caller proceeds; goroutine still blocked
P6                 ...still blocked 8s in; threads 5 -> 5 (LEAKED — the syscall is uninterruptible)
P7 read-uncached TIMED OUT after 3.002s — caller proceeds; goroutine still blocked
P7                 ...still blocked 8s in; threads 5 -> 5 (LEAKED)
P5 write+unlink  TIMED OUT after 3.002s — caller proceeds; goroutine still blocked
P5                 ...still blocked 8s in; threads 5 -> 6 (LEAKED)
```

**Four results, in ascending order of severity.**

1. **P1 and P2 completed normally, in microseconds.** They read `/proc/self/mountinfo`, which involves
   no block device. **This is the whole argument for the §11 recommendation**: on a wedged device the
   pure-`/proc` check is not merely faster, it is the only one that returns at all.
2. **P3 and P4 completed *and reported healthy*.** On a wedged device they do not even have the decency
   to hang — they lie, exactly as they do on a dead one (§6.1). Confirms **R-117b** in a second failure
   mode.
3. **Every probe that touches the device blocked — including P5.** P5 is a buffered `write` with no
   `fsync`, which was *expected* to complete out of page cache. It did not: the `O_CREAT` metadata path
   needs journal access (`wchan=do_get_write_access`). **There is no such thing as a cheap write probe
   that is safe on a wedged device.**
4. **The process could not be killed — not by `SIGTERM`, not by `SIGKILL`.** This is the finding that
   changes the recommendation from a preference into a fence:

```
# after `timeout 200` had already sent SIGTERM:
    PID STAT WCHAN                        ELAPSED COMMAND
2493045 Dl   folio_wait_bit_common          03:20 r117probe
  tid 2493045 stat=D wchan=folio_wait_bit_common
  tid 2493049 stat=D wchan=do_get_write_access

# explicit SIGKILL:
kill -9 2493045
after SIGKILL: 2493045 Dl  folio_wait_bit_common  03:50      <-- STILL ALIVE

# only the device recovering released it:
dmsetup resume r117cel2  -> probe still alive? no — it died once I/O completed
```

**A timeout protects the caller's control flow and nothing else.** The goroutine and its OS thread are
consumed permanently, and the *process* enters uninterruptible sleep. Applied to the agent, whose
reconcile ticker runs every 20 s (`main.go:973`):

- the report loop's caller proceeds, so the timeout "works" — and the evidence of the problem is a
  thread you cannot see and cannot reclaim;
- **`systemctl restart felhom-agent` would hang**, because `SIGKILL` does not reach a `D`-state thread.
  The agent becomes unrecoverable **until the device recovers or the host reboots** — on a box whose
  whole purpose is to be recovered remotely;
- the thread count is **not** a reliable tell (5→5, 5→5, 5→6): the Go runtime reuses threads, so the
  leak does not announce itself in the one metric an operator might watch.

> **This disqualifies I/O probing on this path outright.** Not "use a timeout", not "use it carefully" —
> a liveness probe that issues block I/O converts a dead drive into an unkillable agent. §11's
> recommendation issues none.

---

## 7. Q5 — where the check belongs

**The agent.** Not a balance of arguments — the controller is structurally incapable of it:

1. **The inputs are host mount tables.** P1 needs the host's raw-mount entry for `/mnt/<name>`; P2 needs
   the super options of the host bind. The controller runs **inside** the guest and can see neither. The
   guest's own mountinfo carries the stale entry (with `shutdown`, so P2 is available in-guest) but has
   **no entry at all for the raw host mount**, so P1 is unavailable to it in principle.
2. **Both inputs are already in the agent's hand, in the same function.** `disks.go:222` already calls
   `boundUnderParent(...)` and `devicePresent(t.MountPath)` with both paths in scope. The devno
   comparison adds no new data source and no new dependency.
3. **The agent owns drive identity** (`durable_id`, enrolment, the fs-UUID-keyed mount units), so a
   drive-liveness verdict belongs to the same owner under *one state, one owner*.
4. **The field already exists and is already documented to mean exactly this** (§5.3). The controller
   consumes it and keys the gate on it (`controller/.../intermediary.go:226`). Fixing the producer fixes
   every consumer at once; adding a second, in-guest liveness notion would create the competing
   definition the hub's liveness-threshold rule exists to forbid.

**Ruled on evidence, and the evidence points the same way as the principle** — but note it is (1) that is
decisive, not (3).

---

## 8. Q6 — in-place recovery, and the cheapest fix available

### 8.1 Recovery works, live, without stopping the guest — proven

The repair is `AttachDrive`'s normalize leg (`intermediary.go:238-247`) verbatim: `umount` every layer at
the stable path, then one fresh `mount --bind`, which re-fires propagation into the guest's namespace.

```
guest init pid BEFORE: 2465515
  umount /mnt/r117-drives/sd ... ; mount --bind /mnt/r117sd/felhom-data /mnt/r117-drives/sd
guest init pid AFTER:  2465515      <-- unchanged: the guest was never restarted
```

Verified after the repair:

```
host raw   /mnt/r117cel        -> /dev/mapper/r117cel2  252:12  rw,relatime
host bind  /mnt/r117-drives/cel -> /dev/mapper/r117cel2 252:12  rw,relatime
guest bind (mount id 744, NEW) -> 252:12 ... master:302
GUEST statfs/listdir/read-canary/write  ->  all OK
P1 devno-compare  raw="252:12" bind="252:12"  ->  STALE=false
```

**Two `mount` syscalls, no guest downtime, no app restart, full recovery.** So a fix can self-heal; it
does not have to settle for alarming.

### 8.2 The repair is already wired — three times — and defeated by one line

| Call site | What it does | Why it does nothing today |
|---|---|---|
| `cmd/felhom-agent/main.go:973-985` | 20-second ticker → `ReassertEnrolledMounts` then `ReassertGuestBinds` | → `disks.go:1108` → `AttachDrive` → short-circuits |
| `disks.go:951` | the same, at agent startup | same |
| `controller/internal/web/intermediary.go:301-305` | the `Return` branch calls `agent.GuestAttach(ctx, a.Raw)` — **before `restartStacks` at `:311`** | → `disks.go:624` → `AttachDrive` → short-circuits |

All three land on `intermediary.go:234-236`:

```go
n := countHostMounts(stable)
if n == 1 && b.GuestSeesMount(ctx, vmid, stable) {
    return stable, nil // exactly one bind + guest-visible → fully live, no-op
}
```

In the R-117 state `n == 1` and `GuestSeesMount` is `true`, so **`AttachDrive` declares the namespace
"fully live" and returns without touching it.** The comment on that line is the sixth entry in the
workspace's false-invariant table in all but name: *"fully live"* is precisely what it is not.

> **The ordering is already correct.** The controller asks the agent to re-attach at `:301-305` and only
> then restarts the apps at `:311`. If `AttachDrive` repaired the bind instead of short-circuiting, the
> apps would be restarted onto a **repaired** namespace by the code that exists today. **The defect is
> one predicate, not a missing recovery path.**

---

## 9. Q7 — scope, and the half a `Return`-branch fix cannot reach

**A bind can die in steady state, with no detach/return cycle at all — measured, not inferred.**

Drive A, device swapped to an `error` target with everything running and nothing detached:

```
write into the bind from the guest      ->  Input/output error   (immediately)
mnt-r117cel.mount                      ->  active               <-- still mounted
  BindsTo="dev-dm\x2d11.device"                                     the DEVICE never disappeared
host raw   /mnt/r117cel                ->  /dev/mapper/r117cel  252:11  rw,relatime
host bind  /mnt/r117-drives/cel        ->  /dev/mapper/r117cel  252:11  rw,relatime,emergency_ro
HALF1 GuestSeesMount = true    HALF2 isHostMountpoint = true
=====> BoundUnderParent = TRUE
GUEST write -> errno=30 Read-only file system
```

**Nothing transitions.** `State` stays `attached`, `BoundUnderParent` stays `true`, the drive is never
`Disconnected`, so `planDriveGates` produces **neither** a `Stop` action nor a `Return` action
(`controller/.../intermediary.go:254-259` — both arms require `sp.Disconnected` to differ from
`present[sp.Path]`). **No gate log line, no event, no email, no banner. The customer's apps write into a
read-only namespace and every signal reads healthy indefinitely.**

Reached in this run by a device that errors without disappearing. Real-world equivalents: a SATA/USB link
reset that recovers the *link* after ext4 has already aborted, a drive that develops write errors, an
enclosure that browns out briefly. **Not exotic.**

Two consequences for the eventual fix:

1. **A fix that lives in the `Return` branch cannot close this.** The branch never executes.
2. **P1 does not detect it either** — the device number is unchanged (252:11 on both sides), because the
   device never left. **Only P2 caught it** (`emergency_ro`). This is the reason §8's recommendation is
   **P1 ∨ P2** and not P1 alone; a fix built on the device-number comparison that the return case makes
   so clean would ship with the silent half still open.

**Probed deliberately, per the brief's instruction not to infer it from an absence of reports.**

---

## 10. The reproduction recipe

Exact enough to trigger on demand. `scsi_debug` is the load-bearing choice — it is the only mechanism
tried that can remove a gendisk **while it is mounted**, which is what a USB pull does and what dm and
loop cannot do (both are held open by the stale bind: `dmsetup remove --force` → `Device or resource
busy`).

```bash
# --- venue: any Proxmox host + a scratch LXC. Shared parent MUST exist before the guest starts. ---
PARENT=/mnt/r117-drives; RAW=/mnt/r117sd; VMID=9301
mkdir -p $PARENT
mountpoint -q $PARENT || { mount --bind $PARENT $PARENT
                           mount --make-private $PARENT; mount --make-shared $PARENT; }
pct set $VMID -mp0 $PARENT,mp=$PARENT     # then start the guest; verify `master:` in its mountinfo
pct start $VMID

# --- a drive whose device node can be removed while mounted ---
modprobe scsi_debug dev_size_mb=64 max_luns=1 num_tgts=1
DEV=/dev/sdb                                     # whichever /sys/block/sd*/device/model is scsi_debug
mkfs.ext4 -q -L R117SD $DEV
UUID=$(blkid -s UUID -o value $DEV)
mkdir -p $RAW
systemd-mount --no-block --collect -t ext4 /dev/disk/by-uuid/$UUID $RAW   # UUID-keyed, per mountunit.go:51
mkdir -p $RAW/felhom-data && chown 100000:100000 $RAW/felhom-data
echo canary > $RAW/felhom-data/.r117-canary && sync
mkdir -p $PARENT/sd && mount --bind $RAW/felhom-data $PARENT/sd
# the guest sees it immediately via propagation — no pct, no reboot

# --- 1. PULL: real device removal. systemd stops the raw mount unit by itself (BindsTo=). ---
echo 1 > /sys/block/sdb/device/delete
#     -> bind survives with `shutdown`; raw path is NOT a mountpoint; BoundUnderParent = false

# --- 2. RETURN: rescan. It comes back on a DIFFERENT node because the stale bind pins the old one. ---
echo '- - -' > /sys/class/scsi_host/host1/scan          # -> /dev/sdc, 8:32
systemd-mount --no-block --collect -t ext4 /dev/disk/by-uuid/$UUID $RAW
#     -> R-117: raw on 8:32 healthy, bind on 8:16 dead, BoundUnderParent = TRUE, EIO both directions

# --- Q7 variant: steady-state death, no cycle. Needs a device that ERRORS without disappearing. ---
#     dm-linear over a loop file, then swap the table to `error` and resume:
dmsetup load <name> --table "0 <sectors> error" && dmsetup resume <name>
#     -> raw mount stays ACTIVE, BoundUnderParent stays TRUE, writes EROFS, superopts gain emergency_ro

# --- repair (Q6), no guest restart: AttachDrive's normalize leg, verbatim ---
umount $PARENT/sd && mount --bind $RAW/felhom-data $PARENT/sd

# --- control test for §3.4: with NO stale bind holding it, the letter is REUSED ---
umount $PARENT/sd; echo 1 > /sys/block/sdc/device/delete
echo '- - -' > /sys/class/scsi_host/host1/scan           # -> /dev/sdb, 8:16 again
```

**Traps, each paid for in this run:**

- Establish the **shared parent before the guest starts**, or the guest's parent bind is `private` and no
  drive swap propagates. Verify by finding `master:<n>` on the guest's parent entry.
- The parent bind is **non-recursive**, so a drive already bound under the parent when the guest starts
  is **invisible** to it. Re-fire with `umount` + `mount --bind`. Observed directly at guest first start.
- Do **not** reuse the live `/mnt/felhom-drives`: a bind under it propagates into the real customer guest,
  and the agent's reconcile will act on it.
- `statfs` and `ls` **succeed** on the dead bind. Verify death by reading **file content** or writing.

---

## 11. Recommendation, and its cost

**Framed as a constraint on the fix, not as an implementation.** No code was written.

**Make the liveness signal compare the two mountinfo entries it already reads, and consult the
filesystem's own abort state. Do not add block I/O.**

```
live(stable, raw) :=  bindEntry(stable) exists
                  AND rawEntry(raw)     exists            <-- devicePresent today
                  AND bindEntry.devno == rawEntry.devno    <-- P1: closes the return case (§3.4)
                  AND bindEntry not aborted                <-- P2: closes the steady-state case (§9)
```

**Cost:** two `/proc/self/mountinfo` reads that `isHostMountpoint` and `countHostMounts` **already
perform** on every pass, plus two field comparisons. **Measured 0.17–0.45 ms**, against the 3.85–5.03 ms
`GuestSeesMount` already spends forking `lxc-info` on the same call. **No block I/O, so no disk spin-up,
no write, and no possibility of blocking the report loop.** Effectively free.

**Constraints the fix must respect, each earned above:**

1. **Both halves are needed.** P1 alone leaves Q7 silent; P2 alone leaves any non-ext4 filesystem
   uncovered. **Neither alone is sufficient, and the P1-only fix is the tempting one** because the return
   case is what R-117 was filed as.
2. **Keep the "cannot tell → never absent" rule** (`disks.go:983-986`). An unreadable `/proc`, a missing
   raw entry with an empty path, or an unrecognised filesystem must degrade to *unknown* and be treated
   as present — reporting absent stops a customer's apps. The `(bool)` return shape that made this
   impossible for `newestArchiveOn` (workspace table, row 2) is the trap to avoid: **`live` needs a third
   state, or an explicit unknown-is-present convention pinned by a test.**
3. **P2's token list is filesystem-specific.** `shutdown` and `emergency_ro` are ext4. Both were measured
   here; both must be in the list, because a probe checking only `shutdown` passes the entire Q7 state.
   For any other filesystem the honest answer is *unknown* (see 2), not *live*.
4. **Fixing the predicate is the whole fix, and it self-heals.** §8.2: three call sites already invoke
   the repair, including the controller's `Return` branch **before** it restarts apps, and the 20-second
   ticker. An honest predicate makes `AttachDrive` stop short-circuiting, and the bind is repaired within
   ~20 s with no guest restart. **Do not add a new recovery path; unblock the existing one.**
5. **The test must assert the consequence, not the mechanism.** Per the standing rule and R-97b's
   Scenario F: assert that a **dead namespace yields `BoundUnderParent = false`** (and that the drive-gate
   alarm fires), not merely that a devno comparison returns what it was fed. §5.3 lists **three** comments
   promising a property nothing currently tests; the fix owes one that pins it.
6. **Q7 needs its own scenario.** A test that only exercises detach→return will pass while the silent
   half stays broken. The in-place recipe in §10 is the second scenario.
7. **Do not add an I/O confirmation probe. Measured, not preferred** (§6.3). On a wedged device every
   probe that touches it blocks — including a buffered write with no `fsync` — and the process then
   **cannot be killed by `SIGKILL`**, so the agent could not be restarted until the device recovered or
   the host rebooted. A timeout protects the caller's control flow and nothing else. **P1 and P2 both
   returned in microseconds on that same wedged device**; the recommendation issues no block I/O, and
   that is now a fence rather than a preference.

---

## 12. What this changes about R-116's closure

**R-116's verdict stands. Its evidence was narrower than it reads, and one caveat needs re-labelling.**

- **The four-event sequence is unaffected.** R-116 was about *which event fires for which drive* — the
  pairing of `backup_target_absent`/`backup_target_restored` and their discrimination from the generic
  pair. That was proven on the wire, and every input to it (`isTarget`, the guest-path dedupe, the row
  join) is **configuration-derived** — `storage.cfg`'s `path` versus the `.mount` unit's `Where` — which
  R-117 does not touch. Nothing in this spike disturbs it.
- **`R116-v0116-2026-07-30.md` §5 already recorded the interference and drew the right line**
  (*"a `backup_target_restored` there proves pairing, not recovery"*). This run **confirms that caveat
  from the layer beneath**: on the reattach leg the namespace really was dead, `EIO` both directions, so
  the run's `bound_under_parent = true` was a correct answer to the pairing question and a **false**
  answer to the recovery question.
- **One thing does need re-labelling.** R-116's over-correction check is described in `OPEN-ITEMS.md` as
  *"PASSES with a positive observable — 0 ABSENT lines / 0 drive events over 2m14s with both drives
  present, target `degraded:false`, while 2 `RETURNED` lines prove the gate was ticking."* The two
  `RETURNED` lines do prove the gate was ticking, so the check is **not** an absent-log verdict and rule
  3 is satisfied. But `degraded:false` over that window was read off a drive whose bind was dead — so it
  evidences *"the gate did not over-fire"* and **not** *"the drive was healthy"*. **Narrower than it
  reads, and still true as written.** Recommend the R-116 row gain one clause: the over-correction window
  proves no spurious ABSENT, not drive health.
- **R-117 outranks R-116 in customer impact**, and §9 raises it further: the silent steady-state half has
  no event on any channel at all, where R-116's worst case sent the *wrong* message.

---

## 13. Findings filed — none fixed

| # | Finding | Severity | Evidence |
|---|---|---|---|
| **R-117** | *(existing row, now with a mechanism and a recipe)* The bind-liveness signal is a path-presence test; the R-117 state is `BoundUnderParent = true` over an `EIO` namespace | **HIGH** | §3, §5 |
| **R-117a** | **A drive's bind can die in STEADY STATE, with no detach/return cycle, and no event is emitted on any channel.** The gate produces neither action, so a `Return`-branch fix cannot reach it. **P1 does not detect it; only the filesystem's abort flag does** | **HIGH — larger than R-117 as filed** | §9 |
| **R-117b** | **`statfs` and `getdents` both SUCCEED on a namespace returning `EIO` for all content** — and also on a **wedged** one, where they do not even hang. Any liveness probe built on either is hollow by construction — it reports healthy in exactly the state it exists to detect | **MEDIUM (design trap)** | §4, §6.1, §6.3 |
| **R-117f** | **A liveness probe that issues block I/O turns a wedged drive into an UNKILLABLE AGENT.** On a suspended device every I/O probe blocked — including a buffered write with no `fsync` — and the process survived `SIGTERM` **and `SIGKILL`**, dying only when the device recovered. `systemctl restart felhom-agent` would therefore hang, leaving the agent unrecoverable until the device returns or the host reboots. **A timeout protects the caller's control flow and nothing else**, and the thread count does not reveal the leak (5→5, 5→6) | **HIGH (constraint on the fix — it disqualifies an entire probe class)** | §6.3 |
| **R-117c** | **Three comments** (`disks.go:83`, `:154-155`, `:155-165`) state that `BoundUnderParent` means "live + usable in the guest". **Nothing tests it, and it is false in the measured state.** Not counted as a shipped false invariant because `:158-165` scopes its own claim narrowly — but the summary lines do not | **MEDIUM** | §5.3 |
| **R-117d** | **`AttachDrive` logs and returns `"fully live"` for a namespace that is `EIO` on every call** (`intermediary.go:235`), disabling all three wired repair paths including the controller's pre-restart re-attach | **HIGH — this is the self-heal that already exists** | §8.2 |
| **R-117e** | **The two demo boxes share one uplink and one failure domain.** Both went unreachable together, twice in one session, on all four known routes including the WireGuard OOB path via ep0. There is no route to either box that survives the site losing internet — the "out-of-band" path is not out-of-band with respect to this failure | **LOW (operational, not a code defect)** | §2.5 |

**Observed, out of scope, not acted on:** demo-hp's live agent is **0.113.0** against `main`'s 0.116.0
(§1). It equals the manifest's declared `MinAgent`, so this is not R-115/R-111 drift — but it does mean
**the fleet's designated drill host does not run the R-113 conjunction whose successor this spike is
about.** Whoever fixes R-117 will need that box on a current agent to validate live.

---

## 14. Teardown — DONE, all three layers

Run after the venue came back; the site outage delayed it, it did not skip it.
**Ordering note, recorded because it is a real trap:** any suspended dm device must be `dmsetup resume`d
**before** any `umount`, or every unmount in the teardown blocks on the wedged device — the same
uninterruptible-sleep mechanism as §6.3. Both devices were verified `attr=L--w` (not suspended) first.

### 14.1 Layer 1 — the machine

```
BEFORE   pct list -> 9201 running demo-hp / 9301 running r117
         pct stop 9301 ; pct destroy 9301 --purge   ("purging CT 9301 from related configurations..")
AFTER    pct list -> 9201 running demo-hp          <-- only the pre-existing guest
```

### 14.2 Layer 2 — the host, with the space actually returned

| | Before | After |
|---|---|---|
| `pvesm status` | `r117scratch` **active**, `local` **38.97 %** | `r117scratch` **removed**, `local` **37.02 %** *(session start: 37.00 %)* |
| `df -h /var/lib/vz` | 16G used, **42 %** | 15G used, **40 %** *(session start: 40 %)* |
| `dmsetup ls` | `r117cel (252:11)`, `r117cel2 (252:12)` + 11 pre-existing | **both gone**; the 11 pre-existing `pve-*` unchanged |
| `losetup -a` | `/dev/loop0` (cel.img), `/dev/loop1` (9301 rootfs) | **empty — no loop devices** |
| `scsi_debug` | loaded (1) | **unloaded (0)**; `/dev/sd*` back to `sda1..3` only |
| r117 mounts | raw + bind + scratch shared parent | `findmnt \| grep r117` → **(none)** |
| `/mnt` | `+ r117-drives`, `r117cel`, `r117sd` | **`felhom-drives`, `nvme-1tb`, `vzsnap0`** — exactly as found |
| `/root` | 7 scratch files + `r117/` | `ls /root \| grep -i r117` → **(none)** |

The transient `mnt-r117cel.mount` / `mnt-r117sd.mount` units died with the unmounts
(`Unit mnt-r117sd.mount not loaded` — created by `systemd-mount`, so nothing was left in `/etc`). The
124 MB `debian-13-standard` template was also removed.

### 14.3 Layer 3 — the hub: nothing to dispose of

**This run created no hub-side record.** No customer, no appliance, no pairing, no claim: guest 9301 ran
no controller and had **no network interface at all**, and no agent was enrolled against it. Stated
explicitly per §13 of the template — "teardown clean" without layer 3 is the `sess-c` failure. Here layer
3 is genuinely empty, which is a different claim from silence.

### 14.4 Fences — re-verified after teardown, not assumed

| Fence | State |
|---|---|
| demo-hp guest **9201** | **`running`** — before, during and after; never a probe target |
| demo-hp **`drill-r50`** (VM 300) | **`stopped`** — never started, never touched |
| demo-hp **`local-lvm`** | **38.84 %** — byte-identical before and after, and to the session-start reading |
| demo-hp **`felhom-backup`** | **`active`, 0.46 %**, `content backup` **unchanged** — not re-targeted, not written to |
| live shared parent `/mnt/felhom-drives` | intact with **both** submounts (`nvme-1tb` on `/dev/nvme0n1[/felhom-data]`, `Felhom-Share` autofs) — a **separate** scratch parent was used throughout |
| `felhom-agent` service on demo-hp | **`active`** |
| demo-felhom, Peti's cluster | never contacted |
| **ep0** | **read-only** — one `ssh`, `wg show`, and TCP reachability probes toward `10.77.0.2/.3` during outage 1. Nothing written |
| **Code** | **no `.go` file in either repo modified**; nothing built for deployment, nothing published, no version bumped |
| Repos | the probe lives outside both, in the session scratchpad; the agent tree copy verified byte-identical to `d4eb259` |

---

## 15. What did not happen, and why

- **Everything the brief asked for was measured.** The two items the first internet outage deferred —
  Q4's hang case and teardown — were completed once the site came back: §6.3 and §14 are measurements,
  not plans. The thread-leak hypothesis P6/P7 were built to test turned out to be **the weaker half of
  the real result**: the leak is invisible in the thread count (5→5, 5→6), while the process being
  unkillable by `SIGKILL` is unambiguous.
- **No load or duration testing of the recommended check.** P1/P2 were measured as single calls
  (0.16–0.45 ms), not across a sustained reconcile loop on a box with many drives. Nothing suggests a
  problem — they are two `/proc` reads the code already performs — but it was not measured.
- **No fresh `/disks` payload and no fresh controller gate log** — deliberate, and the same call
  `DIAG-r116` §14 made: both were already captured verbatim on real hardware (twice and four times
  respectively), and running a controller here would have meant a hub customer, a pairing, a golden fetch
  and a claim — the work that consumed three prior sessions — to re-measure a known quantity. **The
  missing layer was the mount tables and the errnos beneath that payload, which is what this run
  supplies.** §5.2's capture is the join between the two.
- **The same-device-node return was not reproduced as a *defect* case** — because §3.4 showed it
  **cannot** occur while a stale bind exists: the stale bind is what forces the new number. The control
  test (letter reused once the bind is released) is the positive observable for that claim.
- **R-117 was not fixed**, per the fence — not even the one-line predicate change §8.2 identifies. The
  design constraints are in §11 for a spec to accept or reject.
- **`felhotest` was not tried**; `Connection refused` was already recorded 2026-07-30 and it is
  irrelevant to this mechanism.
- **Nothing was committed to `felhom-agent` or `felhom-controller`** — this run's only writes are this
  document and the `R-117` row in `backlog/OPEN-ITEMS.md`.

---

Every claim above is either quoted from pushed Gitea source at `file:line` (agent `d4eb259` / controller
`b331f18`) or is captured probe output from the venue. Where a result was inferred rather than measured,
it says so.
