# Critical design review — Proxmox re-platform doc set

> ✅ **RESOLVED (2026-06-08).** All findings folded into 01/02/03 + `proxmox-platform.md`
> (Phase-3 spike run for B2/B3 → `tests/phase3-findings.md`). **Folded:** B1 (03 §4), B2
> (03 §7/§8 + platform §4.7), B3 (03 §2/§3 + platform §3.6), S1 (03 §6/§8), S2 (03 §10/§11),
> S3 (03 §7), S4 (01 §5/§7 + 02 + 03 §2), S5 (01 §7/§11 + 02 §6), S6 (02 §5), M1 (02 §3),
> M2 (03 §7), M3 (03 §10), §6-residual (03 §6). Plus the two Phase-3 design updates:
> provision-by-restore (03 §9) and the settled root-vs-API boundary (03 §3). **Deferred/none:**
> no finding was deferred; the pre-existing open items (operator signing-key mechanics,
> multi-tenant fairness, hub-side desired-state UX, golden-image refresh cadence) remain
> flagged in 03 §13. This artifact can be deleted once confirmed.

Working artifact. Review pass over `01-topology-and-trust.md`, `02-controller-module-map.md`,
`03-host-agent.md`, `proxmox-platform.md`, and the Phase 0 / Phase 1-2 findings, grounded
against the v0.33 source (`felhom-controller/controller/`). Every finding cites a
file+line or a doc section. Severity: **blocking** / **should-fix** / **minor**.

Two findings are self-corrections of my own earlier work (`02` and `proxmox-platform.md`) —
flagged as such.

---

## Ranked summary

| # | Severity | Finding | Where |
|---|---|---|---|
| B1 | **blocking** | Reversibility gate contradicts the self-heal reconcile loop — crashed-guest healing can require a signature-gated destroy → reconcile stalls | `03` §4 vs §4(a) |
| B2 | **blocking** | vzdump bulk-exclusion only works for **volume** mount points; Docker **named volumes live in the LXC rootfs and ARE captured** → naive placement silently backs up the 1 TB media drive. Unvalidated by spike. | `03` §7 vs `proxmox-platform.md` §4.3 + pct manpage |
| B3 | **blocking** | Agent's Proxmox role is called "the minimal role from Phase 1" — but that role is the *narrow self-backup* role that Phase 1 proved is **denied** create/allocate/restore. The agent's operator-tier role is undefined. | `03` §2/§3 vs `phase1-2` §1.3-1.4, `01` appendix |
| S1 | should-fix | Quiescing for agent/hub-scheduled backups has **no agent→controller channel** — the local API is controller→agent only | `03` §6, §8 |
| S2 | should-fix | Agent self-update revert authority unspecified — if the new binary won't boot, nothing outside it can flip back | `03` §11 |
| S3 | should-fix | Storage manifest drops fields `settings.StoragePath` carries today (Label, Schedulable/default, StoppedStacks, MigratedTo) with no re-homing stated | `03` §7 vs `settings.go:90-103` |
| S4 | should-fix | Geo-restriction WAF ownership + Cloudflare **API token** placement unspecified after tunnel placement was locked; zone-wide token in a guest is a blast-radius concern | `03` (absent), `01` §3, `config.go` InfrastructureConfig |
| S5 | should-fix | Cross-doc staleness: `01` §11 still lists tunnel placement OPEN; `02` §6 lists geo "blocked on tunnel placement" — both resolved by `03` §13 | `01` §11, `02` §6 vs `03` §13 |
| S6 | should-fix (self-correct) | `02` put self-restore-test **orchestration** in the controller; `03` correctly makes it agent-owned (controller only reads status) | `02` §5(3) vs `03` §6/§8 |
| M1 | minor (self-correct) | `02` §3 lists `UUID` as a `settings.StoragePath` field — it isn't; UUID is derived from fstab at runtime | `02` §3 vs `settings.go:91-103` |
| M2 | minor | `03` §7 says the manifest "absorbs the disk-state fields StoragePath carries today" incl. UUID — UUID isn't persisted today, so the manifest *adds* it (an improvement, not absorption) | `03` §7 |
| M3 | minor | controller-update is not in `03` §10's journaled-ops list, though it's a multi-step async op | `03` §10 vs §11 |

**Values check: clean.** No DR/key-custody/offboarding path leaves a customer locked out.
Zero-knowledge DR (`03` §8, `01` §8) correctly makes the customer recovery code the
irreducible residual; the operator cannot read data and the box can still restore-test.
No hostage path found.

**Locked premises:** reviewed for soundness/consistency only; not relitigated.

---

## Blocking findings

### B1 — The reversibility gate stalls the self-healing reconcile loop
**Where:** `03` §4(a) vs the gate in §4.
**What:** §4(a) lists "redeploy of a crashed controller" as benign convergence that "falls
out of reconciliation for free." The gate then lists **guest destroy** among the
irreversible ops that require an operator signature "*regardless of whether they arrive as a
job or as a desired-state delta*." These collide: if healing a wedged guest requires
destroy+recreate (corrupt rootfs, failed in-place restart, half-built guest from an
interrupted provision), the reconciler hits a signature-gated op and **cannot proceed
without an operator** — the loop either stalls or silently gives up, defeating "self-healing
… tolerant of missed polls."
**Why it matters:** This is the security-critical control model. A fuzzy benign/destructive
line is unimplementable: either the reconciler can destroy (and a compromised hub's desired
state can wipe guests — the exact threat §4 exists to stop), or it can't (and self-heal is a
fiction for the crashed-guest case).
**Grounding:** `03` §4 self-describes the gate as "security-critical"; §9/§10 already rely on
the reconciler rolling back "a half-built guest" — which *is* a destroy of a customer-id-bound
resource, contradicting the blanket "guest destroy needs a signature."
**Suggested fix (crisp, implementable rule):** Scope the reconciler's destructive verbs by
*provenance and data-bearing-ness*, not by verb:
- The reconciler MAY, without a signature: (a) create/start/restart; (b) destroy resources it
  **created earlier in the same journaled transaction** (compensating rollback, §10); (c)
  destroy resources **tagged ephemeral/scratch** (restore-test scratch guests, §8).
- Destroying or overwriting any resource that **holds the only/primary copy of customer data**
  always needs an operator signature.
- **Healing a crashed controller is non-destructive by construction:** the controller is
  reconstructable from its image + the guest's persistent volume, so "redeploy" = restart the
  LXC / `docker compose up -d` **inside the existing guest** — never a guest destroy. State
  this explicitly so the two clauses stop colliding. (The v0.33 self-heal precedent is already
  in-place restart: `watchdog.go` restarts stopped stacks, it never destroys the guest.)

### B2 — vzdump bulk-exclusion: the rootfs-Docker-volume trap
**Where:** `03` §7 ("Bulk external mounts are excluded from the guest's vzdump (a per-mount
backup flag)").
**What:** Two grounded problems:
1. The flag is real but narrow. The pct manpage (verified): `backup=<boolean>` —
   *"Whether to include the mount point in backups (**only used for volume mount points**)."*
   It does **not** apply to bind mounts / device mounts (those are handled separately).
2. The trap: `proxmox-platform.md` §4.3 (validated in `phase1-2` §2.2) proved that **Docker
   named volumes live inside the LXC rootfs and ARE captured by vzdump** — a sentinel in
   `pgdata` survived. The default Felhom app uses Docker named volumes. So unless bulk data is
   deliberately placed on a **dedicated Proxmox volume mount point** (backup=0) or a bind
   mount, a "bulk" volume will be an ordinary named volume in rootfs and will be **silently
   swept into the whole-guest image** — exactly the 1 TB-media-in-every-backup outcome §7 says
   it prevents.
**Why it matters:** Backup size/cost and RPO blow up silently; the failure is invisible until
a media drive fills the vzdump target. This is load-bearing for the §8 tier model.
**Grounding:** pct manpage (fetched 2026); `proxmox-platform.md` §4.3; `phase1-2` §2.2.
Not covered by any spike — `proxmox-platform.md` §6 "not yet validated" should gain this row.
**Suggested fix:** Make the placement contract explicit: a `bulk` volume **must** be realized
as a dedicated LXC mount point (volume mountpoint with `backup=0`, or an external bind mount),
**never** a Docker named volume in rootfs. The per-volume placement component (`02` §5(2))
must enforce this at deploy. Add a Phase-3 spike: create an LXC with a `backup=0` volume
mountpoint + a bind mount, vzdump it, confirm both are excluded and the rootfs+`backup=1`
volume are included.

### B3 — The agent's Proxmox role is mis-grounded as "the Phase-1 minimal role"
**Where:** `03` §2 ("scoped Proxmox API token (minimal role from Phase 1)"), §3 ("the
Phase-1 minimal role is the API floor").
**What:** Phase 1's minimal role (`FelhomSelfBackup` = `VM.Audit, VM.Snapshot, VM.Backup,
Datastore.AllocateSpace, Datastore.Audit`) is the **narrow self-backup** role scoped to one
guest, and Phase 1 explicitly proved it is **denied (403)** on create/allocate
(`phase1-2` §1.3 call #7) — i.e. exactly the operator-tier ops the agent's whole job consists
of (provision, restore, storage allocation). Worse, `01` appendix states that guest-side role
"**is not used** — we chose the agent-mediated path." So `03` cites, as the agent's role
floor, a role that (a) the architecture discarded and (b) is provably insufficient for the
agent.
**Why it matters:** The agent's actual operator-tier role is **undefined**. Provisioning,
restore, and storage management cannot be built or hardened against an undefined privilege
set, and §3's root-minimization argument ("the Phase-1 minimal role is the API floor")
collapses because that floor can't create a guest.
**Grounding:** `phase1-2` §1.3 (create CT = 403), §1.4 (role = self-backup only); `01`
appendix ("not used … confirmed restore = operator-tier"); `proxmox-platform.md` §3.4.
**Suggested fix:** Replace the Phase-1 reference with a **new agent operator role** to be
defined and least-privilege-tested in a Phase-3 spike — minimally `VM.Allocate`, `VM.Config.*`,
`VM.PowerMgmt`, `VM.Snapshot(.Rollback)`, `VM.Backup`, `VM.Audit`, `Datastore.Allocate(Space)`,
`Datastore.Audit`, plus whatever storage-attach needs (see S4/root-boundary below). Keep §3's
"API token, not root, where the API suffices" principle — that part is sound — but stop
calling it the Phase-1 role.

---

## Should-fix findings

### S1 — No agent→controller channel for backup quiescing
**Where:** `03` §6 (local API is controller→agent only) vs §8 ("the controller stops the app
stack … before a guest vzdump where app-consistency matters").
**What:** App-consistent LXC backup requires the controller to quiesce (no fsfreeze for LXC —
`proxmox-platform.md` §4.2, `phase1-2` §2.1). But the §6 surface is entirely controller→agent;
the box-initiated model forbids the hub calling in, and there is no agent→controller call
defined. For a **hub/agent-scheduled** backup (schedule lives in the manifest `policy`, §7),
the agent has no way to tell the controller "quiesce now."
**Why it matters:** Either scheduled backups silently fall back to crash-consistent (relying
on WAL recovery, which `phase1-2` §3 warns is unvalidated under write load), or the feature
can't be built as drawn.
**Suggested fix:** Make backups **controller-driven for app-consistency**: the controller
learns due/policy via its own hub channel (or a `GET /backup/due` on the local API), quiesces,
calls the existing `POST /backup`, then unquiesces on completion. Document that agent-initiated
vzdump is crash-consistent only. (No inbound-to-guest channel needed — preserves §3/§5.)

### S2 — Agent self-update revert authority unspecified
**Where:** `03` §11 ("a watchdog reverts to last-good if the new binary fails to come up
healthy").
**What:** The agent is a single host systemd service with `Restart=always` (§3). If the new
binary crashes on startup, systemd just restarts the **same bad binary** in a loop. "Revert
to last-good" cannot be done *by* the thing that won't boot. §11 doesn't name the actor.
**Why it matters:** A bad self-update can brick the crown-jewel host agent — the one component
that recovers everything else — with no automatic recovery, requiring break-glass.
**Suggested fix:** Put revert authority **outside** the swapped binary: e.g. an A/B symlink
(`current → good|new`) where a separate systemd oneshot health-gate (`ExecStartPost` probe; on
failure flip the symlink back and restart), or a tiny supervisor unit. Boot-into-last-good +
explicit "commit" after a clean health window is the robust pattern. Add agent-update to the
§10 journal so an interrupted swap is resumable.

### S3 — Manifest schema omits live `StoragePath` fields without re-homing them
**Where:** `03` §7 table vs `settings.go:90-103`.
**What:** Today's `StoragePath` carries `Label`, `IsDefault`, `Schedulable`, `StoppedStacks`,
`Decommissioned`/`DecommissionedAt`/`MigratedTo`. The manifest covers state (attached/
disconnected/decommissioned) and durable_id, but drops: **Label** (human name, e.g. "Külső
HDD 1TB" — UI), **Schedulable/IsDefault** (default placement target for new apps),
**StoppedStacks** (which apps to restart on reconnect — app-domain), **MigratedTo** (decommission
target pointer).
**Why it matters:** `02` named this manifest as the contract that the `settings.StoragePath`
reshape depends on. Silently dropped fields become lost behavior (no default-drive choice, no
restart-after-reconnect list, no friendly labels).
**Suggested fix:** Either add Label + a placement-default marker to the manifest, or explicitly
state which fields re-home to the controller's `settings` (StoppedStacks and Label are
plausibly controller-side; default/schedulable placement must live wherever placement decisions
are made). Make the split explicit so neither side assumes the other owns it.

### S4 — Geo-WAF ownership + Cloudflare API token placement unspecified
**Where:** `03` covers `cloudflared` (tunnel) health but is silent on geo-restriction WAF; `02`
§6 had `cloudflare/`+`geo` "blocked on tunnel placement"; `01` §3 lists the controller's creds
as "hub API key + local-API token" only.
**What:** Now that tunnel placement is locked (host), the **geo-restriction WAF** management
(`cloudflare/` package: zone/waf/geosync) still has no home. It requires a Cloudflare **API
token** (`config.go` InfrastructureConfig.cf_api_token) with zone-wide WAF edit rights. If geo
stays in the controller (app-domain, per `02`), a **zone-wide Cloudflare token sits inside the
customer guest** — a real blast-radius concern (compromise → edit/disable WAF for the whole
zone, potentially other customers on the same zone).
**Why it matters:** Trust-boundary gap. `01` §5's boundary table has no row for controller↔
Cloudflare-API. Unspecified ownership blocks the `02` geo classification from being unblocked.
**Suggested fix:** Decide geo-WAF ownership explicitly and add it to `01` §5. Options: (a) move
WAF management to the **agent/hub** (operator-tier, token off the customer box); (b) keep it in
the controller but scope the CF token per-zone/per-customer if the account model allows. Note
this is now *unblocked* by the tunnel decision and should leave `02` §6's "blocked" state.

### S5 — Cross-doc staleness on the now-locked tunnel placement
**Where:** `01` §11 ("Cloudflare Tunnel placement: host vs guest (§7)") and `02` §6
("`cloudflare/` + `api/geo.go` — blocked on tunnel placement") vs `03` §13 ("Resolved here:
tunnel placement (host, agent-managed)") and the LOCKED list.
**What:** `01` and `02` still present as OPEN/blocked a decision `03` and the locked set have
resolved.
**Why it matters:** A dev reading `01`/`02` would treat a settled decision as open (or a
classification as blocked when only geo-ownership, S4, actually remains).
**Suggested fix:** When folding this review in: update `01` §7/§11 to record tunnel=host
(agent-managed systemd service); update `02` §6 to reduce the cloudflare item from "blocked on
tunnel placement" to the narrower "blocked on geo-WAF ownership (S4)."

### S6 — (self-correction) self-restore-test orchestration belongs to the agent, not the controller
**Where:** `02` §5(3) said "Self-restore-test orchestration — *controller* asks the agent to
restore to scratch guest, validates, reports." `03` §8 makes the **agent** drive it
autonomously; §6 gives the controller only `GET /restore-test/status` (read-only).
**What:** `03` is right and `02` overreached. Zero-knowledge means only the box/agent holds the
PBS key (`03` §8); creating a scratch guest is operator-tier (create/allocate — `phase1-2`
§1.3 #7); the controller cannot do either. The controller's only piece is surfacing status.
**Why it matters:** Keeps the NEW-component list honest — this is not a controller component to
build beyond a status read.
**Suggested fix:** Amend `02` §5(3) to "self-restore-test **status display** (read-only); the
agent owns orchestration."

---

## Minor findings

- **M1 (self-correction):** `02` §3 lists `UUID` among `settings.StoragePath` fields. It is
  **not** there (`settings.go:91-103`: Path, Label, IsDefault, Schedulable, AddedAt,
  Disconnected/At, StoppedStacks, Decommissioned/At, MigratedTo). UUID is derived at runtime
  from fstab / `/host-dev/disk/by-uuid` by `system.ParseFstabUUID` and `watchdog.go`. The
  classification (settings = MODIFY/split) is unaffected; the field list was wrong.
- **M2:** Consequently `03` §7's "absorbs the disk-state fields `settings.StoragePath` carries
  today" overstates: `durable_id`/UUID is *not* carried today, so the manifest **adds** durable
  identity (a genuine improvement — today the controller re-derives UUID from fstab each boot,
  which is fragile). Reword "absorbs" → "absorbs + adds durable_id."
- **M3:** `03` §10 journals "provision, restore" but not **controller-update** (§11), which is
  also a multi-step async op (snapshot→pull→redeploy→health→rollback). Add it so an agent crash
  mid-controller-update is resume-or-rollback like the others.

---

## Verified-correct (no action) — grounding that held up

- LXC flags `nesting=1,keyctl=1` + overlayfs (`03` §9) match `proxmox-platform.md` §2.3 /
  `phase0` §3. ✓
- async `task exitstatus`, not POST return (`03` §8) matches `proxmox-platform.md` §3.5. ✓
- stop-mode backup not requiring `VM.PowerMgmt` (`03` §8 "per Phase 1") matches
  `proxmox-platform.md` §3.4. ✓ (applies to the agent role too.)
- running-LXC snapshot on LVM-thin (`03` §6/§8/§11) matches `proxmox-platform.md` §4.5 /
  `phase1-2` §1.6. ✓
- `monitor/pinger.go` deprecation (`02` DELETE-obsolete) confirmed in `main.go:168,175`
  ("legacy, will be removed" / "no longer used — monitoring is now handled by the Hub"). ✓
- backup keep/delete **intra-file tear** (`02` hazard) confirmed: `backup.go` holds both
  `RunDBDumps`/`DumpAppVolumes(Safe)` (keep) and `RunBackup`/`RunFullBackup` (restic, delete);
  `restore.go` holds `RestoreApp` (restic) + `RestoreAppFromTier2` (app). The §7-8 backup
  contract gives the extracted app-data-backup package a coherent destination. ✓
- Control-plane-not-data-plane (`03` §2/§43): apps keep serving if the agent dies — consistent
  with Docker-in-LXC running independently (`phase0` §3). ✓
- §6 per-guest local-API authorization (token→guest map): sound; a leaked token acts only on
  its own guest. Residual: a compromised controller can `POST /rollback` its **own** guest
  (blast radius = self) — acceptable per design; worth a one-line note that rollback is
  self-scoped and bounded.
