docs(incident): nh3-dev IO stall was a stalled backup, not the disk

hamr-dev reported /dev/sda stalled on nh3-dev: 45 writes in flight
completing zero, jbd2 and flush kworkers in D state for 33 minutes, io
pressure full at 96%, load 26. Every symptom pointed at a dying disk.

It was a vzdump to pbs-ana that collapsed from 64 MiB/s to 1.4 MiB/s and
sat there. Proxmox interposes a copy-before-write filter during a backup,
so every guest write must copy the original block to the target first — the
guest was throttled to the speed of a stalled cross-site backup.

Three things distinguished it, all cheap: there were no device errors
anywhere (a failing disk says so); Dirty was 3.8 MB while 45 requests were
in flight, so the writes were submitted and not completing rather than
backed up in page cache; and the hypervisor was idle at 0.00 io pressure,
which means the writes were not reaching it at all.

Cancelling the task detached the filter: inflight 45 -> 0, D-states gone,
191 MB/s dsync restored. Tonight's incremental is lost and re-runs cheaply,
which is the standing trade in "prefer no backup over one that can crash
the service".

Recurs nightly at 21:00 until changed, and the job has fleecing disabled —
which is why a slow TARGET can stall a GUEST at all.

persistent-memory.md

@@ -151,6 +151,7 @@ not arrived._
 
 ## Recent decisions
 
+- `[2026-09-03]` **nh3-dev wedged for ~40 min and it was the BACKUP, not the disk — a stalled cross-site vzdump holding every guest write via `copy-before-write`.** Symptoms screamed dying disk: 45 writes in flight completing zero, jbd2 + flush kworkers in D state 33 min, io pressure full 96%, load 26, `virtio_ring` in the stack. ⚠ **The discriminator was the ABSENCE of errors** — no SCSI/ATA/IO errors, rpool ONLINE 21%, guest fs 79%, memory fine, and **Dirty only 3.8 MB** (so nothing backed up in page cache; it was stuck BELOW the block layer). ⚠ **The hypervisor was IDLE** — load 0.63, io pressure 0.00, zpool ~0 writes: nothing was reaching the disk because the filter held it. Cause: `vzdump` of VM 102 → **pbs-ana** did 1% at 64 MiB/s then collapsed to **1.4 MiB/s for 35 min**; Proxmox backups interpose a `copy-before-write` filter, so every guest write queues behind the backup's copy-out. FIX = cancel the task (`pvesh delete /nodes/localhost/tasks/<UPID>`); filter detached, inflight 45→0, D-states gone, 191 MB/s dsync restored. ⚠ **`fleecing 0` on the job is why a slow TARGET can stall a GUEST** — fleecing routes copy-before-write to a fast local image instead. Job = `backup-5d8f1221-8f71`, **daily 21:00, `all 1`, storage pbs-ana** → recurs nightly until changed. A prior run of this VM managed 941 MiB/s read, so 1.4 MiB/s is degradation, not normal. → `docs/runbooks/nh3-dev-io-stall.md`
 - `[2026-09-02]` **althing deploy is SIX surfaces, and #6 is outside the althing repo: `~/.claude/settings.json` `crossSessionInbound: "accept"`.** Without it Claude Code HOLDS every cc poke — it auto-delivers only when the sender's permission-mode class matches, and the herald is a daemon that asserts none, so the notice goes to a human watching the pane instead of to the session. ⚠ **The seat reports declared, reachable and green throughout** — same failure shape as the SessionStart hook that was never deployed. Set on nh3-dev by forseti 09:28 with operator authorization (diff verified: one key, backup at `/tmp/settings.json.bak-20260902T092829`). Operator's reasoning: the herald reaches only local seats and a **pane poke already types+Enters into a session**, so the socket channel is strictly NARROWER than what it replaces — stating the existing trust boundary, not widening it. Cost without it is first-contact-only (in-memory correspondent record), not per-message. ⚠ **No attestation exists for the herald to send** — CC identifies a sender by verified pid against the session registry and reads that session's LIVE runtime mode; a daemon is not in it, and `from_mode` on a `type:"user"` frame is never consulted. **`deploy-althing.sh` reports surface 6 and deliberately never SETS it** — a deploy script that edits its own trust settings grants itself trust. → `docs/runbooks/althing-deploy.md`
 - `[2026-09-02]` **`vastblue` gitea org created (id 8, private, owner `vh`) with empty repo `vastblue/platform`** — third entity namespace alongside `corviduo` and `pfi`; most repos still live under `vh/`. Home of VastBlueDocumentAI + the anchor healthcare-billing SPA (signed 3-yr client contract). **Org scope was the decision**: org-level runner registration and secrets are inherited free by the DocumentAI repo when it splits out, and that is the only binding expensive to retrofit. Deliberately NOT set: org runner (instance-wide `ana-docker-runner` already serves it; org scope is for the DEDICATED runner, deferred to U10) and org secrets (none exist yet; a guessed secret looks bound). ⚠ **Dedicated runner is gated on the first client-premises release cut**, not on the first green pipeline — the risk is another repo's CI sharing a root-level daemon with a build that ships to a healthcare client, see the runner entry above. Push needs no credential: vastblue-dev is on nh3-dev and git-SSH there auths as `vh`. → `stacks/gitea-runner/README.md`
 - `[2026-09-02]` **althing 3.3.0 deployed — the `cc` channel, and a plugin-cache false green.** CC seats are now poked over their own message socket (`$XDG_RUNTIME_DIR/cc-socks/<pid>.sock`) instead of by typing into the pane: no process to reap, nothing near the input line. infra-ops moved to `channel=cc`; **the dwarves stay on pane and their guard-4 exposure is UNCHANGED** (`declare` prefers cc, falls back). ⚠ **An undocumented Claude Code interface, taken deliberately** (operator: the FIFO poker was also an unsanctioned hack — a better instance of a class we already had). Break mode = seat goes pull-only with a logged reason, mail still held. ⚠ **`claude plugin update` matches on the plugin VERSION and declines a content-only change** — 3.3.0 edited plugin content at an unchanged 0.1.1, so the CC cache stayed stale while every version check reported success (delta was docs-only, harmless this time). `deploy-althing.sh` now diffs marketplace vs live cache. ⚠ Ordering: **herald restart BEFORE anything declares cc**, or the seat goes silently pull-only. ⚠ This box was at **3.2.4, not 3.2.5** — rollback target here is 3.2.4. Follow-on 3.3.1: **the statusline bell measured a MECHANISM, not the property** — it read `wake-listener-<handle>.lock`, so a cc seat renders 🔕 while push/reachable. Both copies now ask the post office (`reachable` from the status payload) and add 📵 for an outage. ⚠ **TWO COPIES of that script now exist** — `scripts/claude-statusline-command.sh` here (the operator's wired one) and althing's `plugin/scripts/statusline.sh` — independently fixed to the same shape; a drift surface with a countdown, convergence not yet raised with the operator. → `docs/runbooks/althing-deploy.md`