# REUSE.md — felhom-agent

> Before writing new code, check here. Canonical helpers, patterns to copy, traps to avoid.
> Maintenance: update in the SAME commit that adds/changes/deprecates a shared helper.
> Entries cite file + symbol. Line numbers are landmarks only — reconfirm before editing.

## 1. Canonical helpers (MUST reuse — do not reinvent)

### Allowlisted exec / privileged surface (sudoers)

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `Runner` / `ExecRunner.Run`, `RunStdin` | internal/proxmox/privileged.go | `Run(ctx, name, args...) (stdout, stderr []byte, err)` | ALL host command exec (direct or `sudo -n` prefix) | Arg vectors only, never a shell string; `capBuf` caps output at 1 MiB |
| `Privileged` (CreateGoldenLXC/MountUSBByUUID/SMART/Sensors) | internal/proxmox/privileged.go | methods on `*Privileged` | the 3 fenced root-CLI exceptions ONLY | Do NOT add methods — fence is structural (`routing_test.go` asserts it) |
| `SudoHostOps.run` | internal/storage/hostops.go | `run(ctx, name, args...) error` | allowlisted exec with stderr-wrapped error | Every arg pre-validated via validate.go before this is called |
| `Prober.Probe` | internal/capability/probe.go | `Probe(ctx) []Status` | live sudo-policy capability check (`sudo -n -l --`) | Needs a DIRECT runner (never the sudo-prefixing one — double-sudo); never executes probed cmds |
| `stageTemp` | internal/localapi/intermediary.go | `stageTemp(pattern, content) (path, err)` | random-named temp before a root `install` (audit B1) | Fixed /tmp names are a TOCTOU — sudoers globs expect `/tmp/felhom-*-*.ext` |
| `guesthook.InstallSnippet` / `Register` | internal/guesthook/install.go | `InstallSnippet(ctx, runner) error` | pre-start self-heal hook install (C1 net) | Same random-temp+install pattern; snippet delegates to the agent binary (no shell logic). Issues `mkdir -p /var/lib/vz/snippets` FIRST (v0.63.0, B2 — fresh boxes lack the dir; sudoers grants exactly that argv) |

### Disk / format safety (role gates, durable IDs, format guards)

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `SudoHostOps.Format` | internal/storage/hostops.go | `Format(ctx, device, fstype) error` | THE only mkfs path | Guards, in order: `ValidateBlockDevice` + `ValidateFSType` → mandatory `deviceUnclaimed` (claim.go) → exec `felhom-mkfs-guarded` (sudoers allowlists ONLY the wrapper, not raw mkfs) |
| `SudoHostOps.InspectDevice` + `DeviceProbe.DataBearing` | internal/storage/hostops.go | `InspectDevice(ctx, device) (DeviceProbe, error)` | data-bearing verdict from the AGENT's own read | Fail-safe: `Probed=false` ⇒ DataBearing=true; blkid output is evidence, lsblk is read-success authority |
| `classifyClaim` / `SudoHostOps.deviceUnclaimed` | internal/storage/claim.go | `classifyClaim(claimFacts) (unclaimed bool, reason string)` | "is this disk provably free to format" | Pure function of `gatherClaimFacts`; ANY read error/ambiguity/empty-lsblk ⇒ CLAIMED (audit D2); Felhom's own `/mnt/felhom-drives` mounts are not a foreign claim |
| `SudoHostOps.ListCandidateDisks` | internal/storage/candidates.go | `ListCandidateDisks(ctx) ([]CandidateDisk, error)` | enroll-candidate discovery | Fail-safe: omits anything not provably unclaimed |
| `antiRetargetResolveExpect` (+ `antiRetargetResolve`, `antiRetargetResolveBlank`) | internal/localapi/wipe_reresolve.go | `(durableID, expectDataBearing, resolve, derive, inspect) (device, err)` | pre-mkfs anti-retarget: resolve durable id → re-derive+match → re-inspect | AGENT-001 + audit D3; refuses path-only bindings; wired via `Server.reresolveWipe`/`reresolveBlank` (test-injectable) |
| `signedjobs.WipeExecutor.Execute` | internal/signedjobs/wipe.go | `Execute(ctx, op, params) error` | operator-signed data-bearing wipe | Durable-id bound; nonce burned by gate BEFORE execute; refuses no-longer-data-bearing targets |
| `Gate.AuthorizeStorageWipe` | internal/reconcile/gate.go | `AuthorizeStorageWipe(StorageWipeAuthz, *SignedOp) Decision` | tiered wipe authz | user-data ⇒ customer confirm bound to agent's DeviceDurableID; system/backup ⇒ operator signature only, `Confirmed` IGNORED by role |
| `Gate.Authorize` | internal/reconcile/gate.go | `Authorize(Intent, *SignedOp) Decision` | every destructive intent | role-scoping (`roleAuthorizes`) + op-to-action binding; benign passes unsigned; audits every decision |
| `storage.DeviceDurableID` / `ResolveDurableDevice` | internal/storage/durable_device.go | `DeviceDurableID(device) (string, error)` | WIPE-binding ids (`byid:`/`byuuid:`) | Single seam for /disks list AND gate (F20-BUG2); `ResolveDurableDevice` refuses bare paths |
| `storage.ResolveStorageDevice` | internal/storage/durable_device.go | `ResolveStorageDevice("uuid:<fs-uuid>") (dev, err)` | re-resolve enrolled STORAGE drives (remount) | `uuid:` scheme ONLY — distinct from the wipe schemes; never trust a remembered /dev node |
| `deriveDurableID` | internal/storage/durableid.go | `deriveDurableID(typ, s, backingDevice, uuid) string` | storage-target durable id (DR re-attach key) | Deterministic per type; `uuid:` for usb/local-dir; PBS id includes `#<fingerprint>` |
| `SystemDisks` / `isSystemBacked` / `RoleForStorage` / `RoleForRawDevice` | internal/storage/role.go | `RoleForRawDevice(device, sysDisks, sysKnown) DeviceRole` | protection-tier classification | Fails safe to `system` (most protected) on any ambiguity; role is AGENT-derived, never caller-supplied |
| `ValidateUUID/MountPath/BlockDevice/FSType/SMARTDevice/LVMName`, `UnitNameForMount` | internal/storage/validate.go | `Validate*(v) error` | EVERY arg that reaches a root shell-out | The security boundary; strict whitelists (no by-* symlinks, no dm, no traversal); `systemdEscapePath` computed in-process |
| `ValidateNetworkMountSpec` | internal/storage/netmount.go | `ValidateNetworkMountSpec(spec) error` | NAS mount input boundary | Same discipline as validate.go; SMB requires a creds ref; mountpoint confined under `NetworkMountRoot` |

### Mount lifecycle (host + guest binds)

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `SudoHostOps.EnsureMount` | internal/storage/hostops.go | `EnsureMount(ctx, MountSpec) error` | persistent by-UUID systemd .mount | Validate→render→stage→`install`→`enable --now`; idempotent |
| `SudoHostOps.Unmount` | internal/storage/hostops.go | `Unmount(ctx, where) error` | detach a mount unit | DESTRUCTIVE — caller MUST have gated it; does not self-authorize |
| `SudoHostOps.ReassertEnrolledMounts` | internal/storage/hostops.go | `ReassertEnrolledMounts(ctx)` | reboot remount (re-resolve by UUID) | Re-asserts unless mounted AND enabled (`shouldReassertMount`); skips absent UUIDs |
| `GuestBinder.AttachDrive` / `DetachDrive` | internal/localapi/intermediary.go | `AttachDrive(ctx, vmid, where) (guestPath, err)` | live drive hot-swap under `/mnt/felhom-drives` | Normalizes to EXACTLY ONE bind via `countHostMounts` (converges double-binds); force re-bind when guest can't see it |
| `GuestBinder.EnsureSharedParent` | internal/localapi/intermediary.go | `EnsureSharedParent(ctx) error` | shared-parent bind + boot unit | make-private+make-shared ONLY on first bind — re-running orphans the guest's slave; F2-a: compares script AND unit for staleness |
| `StablePathForRaw` / `DriveNameFromRaw` | internal/localapi/intermediary.go | `StablePathForRaw("/mnt/<n>") string` | raw host mount → stable guest path | Single source of truth both repos derive from |
| `GuestBinder.GuestSeesMount` / `GuestBootID` | internal/localapi/intermediary.go | `GuestSeesMount(ctx, vmid, path) bool` | guest-visible (usable) signal; reboot detection | Host bind present ≠ guest sees it (non-recursive parent bind) |
| `SudoHostOps.EnsureNetworkMount` / `RemoveNetworkMount` / `ListNetworkMounts` | internal/storage/netmount.go | `EnsureNetworkMount(ctx, spec) error` | NAS automount pair | rm glob confined to `mnt-felhom*` units; NAS ≠ drive (no durable-id/SMART/wipe) |

### Durable stores (atomic state)

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `IntentStore` (`Get/SetEnrolled/SetEjected/SetDecommissioned/OnAbsent`) | internal/storage/intent.go | `OpenIntentStore(path)` | drive intent (4-state self-heal) | Keyed by durable-id only; `OnAbsent` is the ONLY ejected→enrolled path; refuses empty ids |
| `GuestBindStore` (`Record/Remove/Guests`) | internal/localapi/guestbindstore.go | `OpenGuestBindStore(path)` | per-guest enrolled binds (F9 re-assert) | Same tmp+rename 0600 pattern as IntentStore |
| `FormatJobStore` + `startFormatDetached` + `RecoverFormatJob` | internal/localapi/formatjob.go | `startFormatDetached(device, durableID, fstype, blank) <-chan error` | detached, restart-surviving mkfs (F20-BUG3) | Runs off `s.baseCtx` (60-min bound) so a request deadline can't SIGKILL mkfs; recovery re-resolves by durable id; blank jobs re-check STILL-blank |
| `TokenStore.Mint` / `Lookup` | internal/localapi/tokenstore.go | `Mint(vmid) (plaintext, error)` | per-guest local-API tokens | Only the SHA-256 hash persists (fsync'd append log); constant-time compare on lookup; plaintext returned exactly once. Lookup RELOADS the file once on a miss (v0.63.0, B3): the one-shot provisioner mints into the same file the daemon indexes — cross-process coherence without a restart; append-only size check bounds the re-read |
| `FileNonceStore.SeenOrRecord` | internal/authz/noncestore.go | `SeenOrRecord(nonce, exp) bool` | durable anti-replay | fsync'd before returning false; prune only after exp |
| `Journal` (`Append/Latest/InFlight/AlreadyApplied`) | internal/reconcile/journal.go | `OpenJournal(path)` | op journal + idempotency + crash recovery | `Recover` consumes `InFlight()`; scratch entries special-cased |

### Local-API plumbing

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `Server.withGuest` | internal/localapi/server.go | `withGuest(fn(w, r, vmid)) http.HandlerFunc` | bearer auth + self-scoping for EVERY route | Token→vmid is the authority; explicit `?vmid=` only a consistency check (403 on mismatch) |
| `Server.scopedFromBody` | internal/localapi/server.go | `scopedFromBody(w, bodyVMID, tokenVMID, path) bool` | POST-body vmid self-scope check | Call right after decode; false = already 403'd |
| `decodeBody` / `writeOK` / `writeErr` / `writeStatus` | internal/localapi/server.go | `writeStatus(w, code, ok, data, errMsg)` | ALL local-API JSON I/O | Do not hand-roll response envelopes |
| `EnsureLeaf` | internal/localapi/cert.go | `EnsureLeaf(certPath, keyPath, host) (cert, fingerprint, generated, err)` | pinned self-signed leaf | `generated=true` invalidates every issued bootstrap pin — log LOUD (B.1) |
| `Server.RecoverStaleLockedGuests` | internal/localapi/stalelock.go | `RecoverStaleLockedGuests(ctx)` | startup stale vzdump-lock heal (F2-b) | Clears ONLY `backup`/`snapshot-delete`, only when no vzdump in-flight; A1 RESOLVED (v0.62.0): scan is pool-intersected (`ListLXC` ∩ `Client.Pool`), fail-safe skip on pool-read failure |
| `ControllerSwapper.Swap` + `ValidControllerImage` | internal/localapi/controllerswap.go | `Swap(ctx, vmid, target) *ControllerSwapState` | agent-owned controller image swap + rollback | Strict image regex (repo + 3-part semver); state file written BEFORE swap; no-healthcheck images need `verifyDwell` |

### Proxmox client / hub / PBS / provisioning

| Symbol | File | Short signature | Use for | Gotchas |
|---|---|---|---|---|
| `Client.WaitTask` | internal/proxmox/task.go | `WaitTask(ctx, upid, opts) (TaskStatus, error)` | asserting EVERY mutating op | POST 200 ≠ success; authz can fail at task exec; `AllowWarnings` opt-in |
| `Client.Pool` | internal/proxmox/query.go | `Pool(ctx, name) (PoolInfo, error)` | felhom-pool membership (the ownership registry, A1) | Needs `Pool.Audit` at `/pool/<name>` (host-install v1.9.0+); `Pool.Allocate` does NOT satisfy the read; members can be storages (type `storage`, vmid 0) — filter them |
| `Client` mutate wrappers (`RestoreLXC/Vzdump/DestroyLXC/Snapshot/Rollback/SetConfig/ResizeLXC/Start/Stop`) | internal/proxmox/mutate.go | return `(upid, error)` | all API mutations | Async → always pair with WaitTask; route via gate/queue, not ad-hoc |
| `TLSConfig.build` / `normalizeFingerprint` | internal/proxmox/tls.go | `build() (*tls.Config, error)` | PVE leaf-cert SHA-256 pinning | No insecure default |
| `pinnedTLS` | internal/pbs/pin.go | `pinnedTLS(fingerprint) (*tls.Config, error)` | PBS leaf pinning | Same model as PVE; 64-hex fingerprint normalized |
| `hub.Client.Report` | internal/hub/client.go | `Report(ctx, *HostReport) (*ControlEnvelope, error)` | the heartbeat | Typed `TransportError`/`HTTPError`, never contain the bearer token |
| `hub.Loop` + `MultiObserver` | internal/hub/loop.go | `NewLoop(...)`; `MultiObserver(obs...)` | resilient report loop + envelope fan-out | Errors logged, loop continues; interval clamped 60–3600 s |
| `provision.BackHalf.Provision` | internal/provision/backhalf.go | `Provision(ctx, Input) (Result, error)` | guest bootstrap back-half | mint→render→0600 write→chown 100000:100000→`pct set` ro bind→onboot; token NEVER logged/returned |
| `reconcile.Queue.Submit` | internal/reconcile/queue.go | `Submit(vmid, fn) <-chan error` | per-guest serialization of ALL mutations | Same vmid strictly FIFO; lanes parallel across guests |
| `Engine.RunSignedJob` | internal/reconcile/job.go | `RunSignedJob(ctx, intent, signed, exec) JobResult` | executing a gated destructive job | Idempotency by nonce; journaled |
| `escrow.Create` | internal/escrow/escrow.go | `Create(ctx, CreateOptions) (CreateResult, R, error)` | PBS-key escrow (zero-knowledge) | Recovery code returned SEPARATELY from the result (anti-log); self-verifies recoverability |

## 2. Canonical patterns (copy structure from THE named file)

| Pattern | Canonical file | Key traits |
|---|---|---|
| Validate-then-exec privileged op | internal/storage/hostops.go (`EnsureMount`) | validate EVERY arg (validate.go) → render → stage in agent dir → root `install` → `systemctl`; refuse before any command exists |
| Fail-safe pure classifier over gathered facts | internal/storage/claim.go (`classifyClaim` over `claimFacts`) | pure function ⇒ fixture-testable; any error/ambiguity refuses; gather separated from verdict |
| Anti-retarget durable-id binding | internal/localapi/wipe_reresolve.go | resolve id → re-derive + exact match → re-inspect expected state → act on RE-RESOLVED device only |
| Atomic single-file JSON store | internal/storage/intent.go | `Open*` loads (missing=empty, corrupt=fail-loud), mutex, tmp+rename 0600, idempotent set |
| Durable append-only log + index | internal/authz/noncestore.go (`FileNonceStore`) | fsync before returning "new"; replay into index on open; expiry-only compaction |
| Injectable seam funcs on Server | internal/localapi/server.go (`reresolveWipe`, `deviceDurableID`, `boundCheck`) | prod default wired in `NewServer`; tests override — no real /dev in tests |
| Optional dependency degradation | internal/localapi/server.go (`Options`) | nil dep ⇒ endpoint answers "not configured" (503), never a crash |
| Root-file install via random temp | internal/localapi/intermediary.go (`installSharedParentUnit`) | `stageTemp` (os.CreateTemp) → sudoers-globbed `install -m` → pinned destination |
| Detached destructive job + restart recovery | internal/localapi/formatjob.go | persist `running` → run off baseCtx → record outcome; recovery re-resolves durable id, never a path |
| Signed-op verify pipeline | internal/authz/verifier.go (`Verify`) | armor→namespace→key-material allowlist→crypto over RAW bytes→blob→target→window→nonce LAST |
| Resilient daemon loop | internal/hub/loop.go (`Loop.Run`) | ctx-cancel returns nil; errors logged and loop continues |
| Guarded-below-the-agent wrapper | configs/felhom-mkfs-guarded.sh | root re-checks catastrophic cases (system disk/LVM PV/foreign mount/RO/member FS) even against an agent bug |

## 3. Dangerous lookalikes — do NOT reuse

| Trap | Why it bites | Use instead |
|---|---|---|
| Acting on the caller's `req.Device` (or any remembered /dev path) after inspection | classify→mkfs TOCTOU (AGENT-001): /dev re-enumeration retargets the node to a different physical disk | `Server.reresolveWipe`/`reresolveBlank` → format the RE-RESOLVED device |
| Exec'ing raw `mkfs.*` (incl. `Binaries.MkfsExt4/MkfsXfs`) | sudoers no longer allowlists raw mkfs; bypasses the claim filter + wrapper re-checks | `SudoHostOps.Format` (→ `felhom-mkfs-guarded`) |
| `DiskInfo.DurableID` (`uuid:`) as a wipe-confirmation id | wipe gate resolves `byid:`/`byuuid:` — a `uuid:` id is a `binding_mismatch` (F20-BUG2) | `DiskInfo.WipeDurableID` / `storage.DeviceDurableID` |
| `ResolveDurableDevice` for enrolled-storage remounts (or vice versa) | schemes differ: wipe = `byid:`/`byuuid:`, storage = `uuid:` — each refuses the other | `ResolveStorageDevice` for mounts; `ResolveDurableDevice` for wipes |
| `authz.MemoryNonceStore` on a real host | replay protection dies on restart | `authz.FileNonceStore` |
| Adding methods to `proxmox.Privileged` | breaks the 3-exception root-CLI fence (`routing_test.go`) | `proxmox.Runner` + a new sudoers Cmnd_Alias + validate.go-style checks |
| Calling `Client.DestroyLXC`/`Vzdump`/`SetConfig` outside the gate/queue/journal | skips classification, signature, per-guest serialization, crash recovery | `reconcile.Engine` paths / `RunSignedJob`; queue via `Queue.Submit` |
| `GuestBinder.AttachBind`/`DetachBind` (per-drive `pct set -mpN`) | legacy model; a missing bind source can brick guest boot (C1) | `AttachDrive`/`DetachDrive` (intermediary model) |
| `isHostMountpoint` to reconcile bind state | boolean can't converge stacked double-binds (the /mnt doubling bug) | `countHostMounts` normalization inside `AttachDrive` |
| Acting on a raw `ListLXC` list as if it were "guests the agent owns" | audit A1 (pre-v0.62.0 the stale-lock reaper did exactly this — contained only by the pool-scoped token) | ownership must be PROVEN: intersect with `Client.Pool` membership like `staleLockController.Guests()` (v0.62.0), fail-safe on read failure |

## 4. Seams & interfaces (testing + cross-repo)

| Interface | Defined in | Implemented by | Fakes/tests at |
|---|---|---|---|
| `proxmox.Runner` | internal/proxmox/privileged.go | `*ExecRunner` (direct/sudo) | `mockRunner` internal/proxmox/mock_test.go; runner fakes in storage tests |
| `storage.HostOps` | internal/storage/hostops.go | `*SudoHostOps` (prod), `NoopHostOps` (degraded) | fakes in internal/storage/observe_test.go, watchdog_test.go |
| `storage.HostReader` | internal/storage/hostread.go | `*ProcHostReader` | `fakeHostReader` internal/localapi/disks_test.go; internal/storage/role_test.go |
| `localapi.DiskOps` / `StorageGate` / `GuestAttacher` / `GuestLister` | internal/localapi/disks.go | `*storage.SudoHostOps`; `storageGateAdapter` (cmd/felhom-agent/main.go); `*GuestBinder`; `*proxmox.Client` | `fakeDiskOps`/`fakeGate`/`fakeGuestAttacher`/`fakeGuestList` internal/localapi/disks_test.go |
| `localapi.GuestAPI` / `BackupService` / `BackupStore` / `TokenAuthority` | internal/localapi/server.go | `*proxmox.Client`, `*backup.BackupRunner`, `*backup.Store`, `*TokenStore` | `fakeGuests`/`fakeBackups`/`fakeStore` internal/localapi/server_test.go |
| `localapi.StaleLockController` | internal/localapi/stalelock.go | `*staleLockController` (Client + Runner + pool) | `fakeStaleLock` (Server-level) stalelock_test.go; `fakeStaleLockAPI` (controller-level, tests the A1 pool intersect) stalelock_pool_test.go |
| `localapi.GuestExecutor` | internal/localapi/controllerswap.go | `*GuestBinder` (pct exec) | `fakeGuestExec` internal/localapi/controllerswap_test.go |
| `reconcile.OpVerifier` | internal/reconcile/gate.go | `*authz.Verifier` | fake verifier in internal/reconcile gate tests |
| `signedjobs.WipeOps` / `Executor` (`ExecutorChain`) | internal/signedjobs/wipe.go + runner.go | `*storage.SudoHostOps`; `WipeExecutor`+`DecommissionExecutor` | internal/signedjobs wipe/runner/decommission tests |
| `hub.reporter` / `collectorIface` / `EnvelopeObserver` | internal/hub/loop.go | `*hub.Client`, `*hub.Collector`; `desired.Syncer` + `signedjobs.Runner` | `fakeReporter`/`fakeCollector` internal/hub/loop_test.go |
| `capability.Runner` | internal/capability/probe.go | `*proxmox.ExecRunner` (RunnerDirect) | `fakeRunner` internal/capability/probe_test.go |
| Cross-repo: local API ↔ controller | internal/localapi/server.go routes; contract seeded by internal/provision/doc.go (`bootstrap.json`: endpoint + leaf fingerprint + token) | felhom-controller's agentapi client | pin = served leaf cert (memory gotcha) |
| Cross-repo: agent ↔ hub | internal/hub/report.go (`HostReport`), `ControlEnvelope`; POST `/api/v1/host-report` | hub mirrors structs field-for-field | new event/report fields need hub-side ingest changes |
| Cross-repo: shipped host artifacts | configs/felhom-agent.sudoers, configs/felhom-mkfs-guarded.sh, shared-parent script/unit (inline in internal/localapi/intermediary.go) | deployed WITH the binary | sudoers globs must match `stageTemp` patterns + staging dirs exactly |
| Operator signing | internal/authz (OpBlob, SSHSIG) | cmd/felhom-opsign (offline CLI) | blob/verify tests in internal/authz |

## 5. Extension points (where new features plug in)

- **Local-API route**: add to `Server.Handler` (internal/localapi/server.go) wrapped in `s.withGuest`; new deps go into `Options` as OPTIONAL fields degrading to "not configured".
- **New signed-job verb**: implement `signedjobs.Executor` (return `ErrNoExecutor` for foreign ops) and append to the `signedjobs.ExecutorChain` in cmd/felhom-agent/main.go; add the op class + role scoping in internal/reconcile (classify.go, gate.go `roleAuthorizes`).
- **New privileged host op**: validate args (internal/storage/validate.go style) → exec via `Runner` → add a `Cmnd_Alias` to configs/felhom-agent.sudoers → add a probe vector to internal/capability/manifest.go (so degradation is visible) → ship sudoers with the binary.
- **New reconcile action**: `ActionKind` + `classOfAction` (internal/reconcile/classify.go), plan emission in internal/reconcile/plan.go; destructive ⇒ gate handles it automatically.
- **Hub-report field**: extend `hub.HostReport` (internal/hub/report.go) + `Collector` — hub side must mirror + allowlist it (cross-repo).
- **Envelope-driven behavior**: implement `hub.EnvelopeObserver`, add to the `MultiObserver` in cmd/felhom-agent/main.go.
- **Selftest mode**: `selftestFlag` + `runSelftest*` in cmd/felhom-agent/main.go.
- **Config**: internal/config/config.go (`Load` + `applyEnv` `FELHOM_AGENT_*` overlay; keep secrets out of `Redacted()` output).

## 6. Known duplication (observed — NOT fixed)

- Two lsblk `-J` parsers with near-identical structs: `parseLsblkDevice`/`lsblkDevice` (internal/storage/hostops.go) vs `parseLsblkNodes`/`lsblkDev` (internal/storage/claim.go).
- Two smartctl `-a -j` paths: `SudoHostOps.SMART` (internal/storage/hostops.go, parsed `hub.SmartSummary`) vs `Privileged.SMART` (internal/proxmox/privileged.go, raw map).
- Atomic tmp+rename JSON store implemented 3×: `IntentStore.saveLocked` (internal/storage/intent.go), `FormatJobStore.save` (internal/localapi/formatjob.go), `GuestBindStore.saveLocked` (internal/localapi/guestbindstore.go) — comments say "mirrors", no shared helper.
- `run(ctx, name, args...) error` stderr-wrapping helper duplicated 4×: `SudoHostOps.run`, `Privileged.run`, `BackHalf.run` (internal/provision/backhalf.go), `GuestBinder.run` (internal/localapi/guestbind.go).
- Several independent /proc mount-table readers: `SudoHostOps.mountedSet` (internal/storage/hostops.go), `ProcHostReader.Mounts` (internal/storage/hostread.go), `isHostMountpoint` + `countHostMounts` (internal/localapi/intermediary.go).
- Deliberate mirror: `antiRetargetResolveExpect` (internal/localapi/wipe_reresolve.go) duplicates `WipeExecutor.Execute` steps 1–3 (internal/signedjobs/wipe.go) across packages.
- `stableParentDir` literal duplicated in internal/provision/backhalf.go to avoid a provision→localapi import edge (commented as intentional); `trim` (internal/storage/hostops.go) vs `trimBody` (internal/proxmox/errors.go) output-truncation twins.
