F20-BUG3: run mkfs detached (survives request deadline + agent restart); v0.31.0

The format ran mkfs under the HTTP request context, so the controller's 15s client timeout cancelled it → SIGKILL mid-write → corrupt disk. Now mkfs runs DETACHED off s.baseCtx (a dropped request can't kill it) via a persisted formatJob record; the handler still waits to return the synchronous result (backward-compatible with the v0.62.0 controller) but abandoning the wait on client-disconnect leaves the mkfs running to completion. New GET /disks/format/status surfaces the job (additive). RecoverFormatJob runs on agent startup: a record left 'running' (agent died mid-format) is re-resolved by durable-id (anti-retarget — absent/swapped disk NOT re-formatted) and the mkfs re-run; a blank/path-bound interrupted format is marked failed (retry), never auto-re-run. Tests: detached run persists running→done + binds durable-id; status endpoint; recovery re-runs an interrupted durable-id-bound format; skips blank; skips unresolvable durable-id. Version 0.30.0 → 0.31.0.
F9: auto-re-assert enrolled guest data-drive binds on agent startup
2026-06-14 15:16:01 +02:00 · 2026-06-14 15:07:37 +02:00 · 2026-06-14 15:00:56 +02:00
9 changed files with 923 additions and 13 deletions
@@ -43,7 +43,7 @@ import (

 // version is the agent version. Overridable at build time with
 // -ldflags "-X main.version=<v>"; defaults to the in-repo CHANGELOG version.
-var version = "0.30.0"
+var version = "0.31.0"

 func main() {
 	var (
@@ -340,6 +340,20 @@ func runDaemon(cfg config.Config, logger *slog.Logger) int {
 	} else {
 		intentReader = intentStore
 	}
+	// F9: per-guest enrolled-bind record, replayed by ReassertGuestBinds at startup to restore a
+	// guest data-drive bind that a re-provision dropped (durable-id-keyed; absent/swapped drives skipped).
+	guestBindStore, gbErr := localapi.OpenGuestBindStore(filepath.Join(intentStateDir, "guest-binds.json"))
+	if gbErr != nil {
+		logger.Warn("storage: guest-bind store unavailable — startup bind re-assert disabled (F9)", "err", gbErr)
+		guestBindStore = nil
+	}
+	// F20-BUG3: persisted disk-format job — lets mkfs run detached from the request and survive an agent
+	// restart (RecoverFormatJob re-runs an interrupted durable-id-bound format).
+	formatJobStore, fjErr := localapi.OpenFormatJobStore(filepath.Join(intentStateDir, "format-job.json"))
+	if fjErr != nil {
+		logger.Warn("storage: format-job store unavailable — format restart-recovery disabled (F20-BUG3)", "err", fjErr)
+		formatJobStore = nil
+	}
 	watchdog := storage.NewWatchdog(storage.WatchdogOptions{
 		Targets:   storage.NewCachingKnownTargets(observer, cfg.Storage.KnownRefresh()),
 		Liveness:  storage.NewHostLiveness(hostReader, 0),
@@ -424,7 +438,7 @@ func runDaemon(cfg config.Config, logger *slog.Logger) int {
 	jobsRunner := signedjobs.NewRunner(client, gate, signedjobs.ExecutorChain{wipeExec, decommExec}, cfg.Hub.HostID, logger)
 	loop.SetEnvelopeObserver(hub.MultiObserver(desiredSyncer, jobsRunner))

-	localSrv := buildLocalAPIServer(cfg, px, backupStore, observer, hostOps, gate, collector, intentRec, logger, &localTokens)
+	localSrv := buildLocalAPIServer(cfg, px, backupStore, observer, hostOps, gate, collector, intentRec, guestBindStore, formatJobStore, logger, &localTokens)
 	if localTokens != nil {
 		defer localTokens.Close()
 	}
@@ -462,6 +476,12 @@ func runDaemon(cfg config.Config, logger *slog.Logger) int {
 	go func() { errc <- pbsLoop.Run(ctx) }()
 	if localSrv != nil {
 		localServers = 1
+		// F9: on startup (the host's bring-up/reconcile trigger), re-assert any enrolled guest data-drive
+		// bind that a re-provision dropped — before serving, so the drive is back in the guest config
+		// (activates on the guest's next reboot). On-durable-id-match; absent/swapped drives are skipped.
+		localSrv.ReassertGuestBinds(ctx)
+		// F20-BUG3: complete a disk format that an agent restart interrupted (durable-id-bound, re-resolved).
+		localSrv.RecoverFormatJob(ctx)
 		go func() { errc <- localSrv.Run(ctx) }()
 	}
 	if lanLoop != nil {
@@ -576,7 +596,7 @@ func buildRestoreTestScheduler(cfg config.Config, px *proxmox.Client, engine *re
 // leaf (stable fingerprint). Any failure DISABLES the server (returns nil) WITHOUT crashing the
 // daemon — the host still reports/reconciles; only the controller channel is unavailable until
 // fixed. The opened token store is returned via outTokens so the caller can Close it.
-func buildLocalAPIServer(cfg config.Config, px *proxmox.Client, store *backup.Store, observer *storage.Observer, hostOps storage.HostOps, gate *reconcile.Gate, collector *hub.Collector, intent localapi.IntentRecorder, logger *slog.Logger, outTokens **localapi.TokenStore) *localapi.Server {
+func buildLocalAPIServer(cfg config.Config, px *proxmox.Client, store *backup.Store, observer *storage.Observer, hostOps storage.HostOps, gate *reconcile.Gate, collector *hub.Collector, intent localapi.IntentRecorder, guestBinds *localapi.GuestBindStore, formatJobs *localapi.FormatJobStore, logger *slog.Logger, outTokens **localapi.TokenStore) *localapi.Server {
 	if !cfg.LocalAPI.Enabled() {
 		return nil
 	}
@@ -620,6 +640,8 @@ func buildLocalAPIServer(cfg config.Config, px *proxmox.Client, store *backup.St
 		Guests2:     px,
 		GuestAttach: guestBinder, // slice 10 P2: bind enrolled data drives into the guest
 		Intent:      intent,      // slice 10 P3: record enroll/eject intent for self-heal
+		GuestBinds:  guestBinds,  // F9: per-guest bind record for the startup re-assert
+		FormatJobs:  formatJobs,  // F20-BUG3: detached-format job record + restart recovery

 		// Host metrics (slice 9): the shared collector serves GET /host/metrics — a fresh host +
 		// per-storage view to the customer's monitoring page (reuses the slice-4 collector).
@@ -2,6 +2,7 @@ package localapi

 import (
 	"context"
+	"fmt"
 	"net/http"
 	"strconv"
 	"strings"
@@ -103,6 +104,17 @@ type DiskInfo struct {
 	// controller strips the "uuid:" prefix to get the fs UUID it passes to POST /disks/assign —
 	// the only way the (de-privileged) controller can learn the mount key it cannot read itself.
 	DurableID string `json:"durable_id,omitempty"`
+	// WipeDurableID is the device's WIPE-binding durable id in the SAME scheme the format gate resolves
+	// against (byid:<wwn>/byuuid:<uuid>). F20-BUG2: the customer must confirm a data-bearing wipe with
+	// THIS id, not DurableID (uuid:) — passing the uuid: id was rejected as a binding_mismatch. "" when
+	// the device has no durable identity (a wipe of it can't be bound anyway). Distinct from DurableID
+	// (uuid:, used for /disks/assign) on purpose; both are derived from the agent's own device read.
+	WipeDurableID string `json:"wipe_durable_id,omitempty"`
+	// GuestAttached reports whether THIS guest (the token's vmid) actually has the drive's felhom-data
+	// namespace bound into its config — i.e. the drive is usable IN the guest, not merely present on the
+	// host. F9: host presence (State=attached) != guest-usable; this is the missing signal that made the
+	// HDD look available when it wasn't bound. Only meaningful for user-data drives.
+	GuestAttached bool `json:"guest_attached"`
 }

 // handleDisks lists the host's drives + data-bearing flags (read-only/benign).
@@ -119,16 +131,20 @@ func (s *Server) handleDisks(w http.ResponseWriter, r *http.Request, vmid int) {
 	// Resolve the OS/system disks ONCE for this request — role classification is agent-authoritative
 	// (the agent's own mount/topology read, never the caller's claim).
 	sysDisks, sysKnown := storage.SystemDisks(s.hostReader())
+	// F9: which host mount paths are actually BOUND into THIS guest's config (guest-usable, not just
+	// host-present). A bind's mp= equals the guest path, which is the drive's host mount path (`where`).
+	boundPaths := s.guestBoundPaths(r.Context(), vmid)
 	out := make([]DiskInfo, 0, len(targets))
 	for _, t := range targets {
 		di := DiskInfo{
 			Name: t.Name, Type: t.Type, State: t.State,
 			BackingDevice: t.BackingDevice, MountPath: t.MountPath, Class: t.ClassHint,
-			DurableID:    t.DurableID,
-			Role:         string(storage.RoleForStorage(t.Type, t.BackingDevice, sysDisks, sysKnown)),
-			TotalBytes:   t.TotalBytes,
-			UsedBytes:    t.UsedBytes,
-			UsedFraction: t.UsedFraction,
+			DurableID:     t.DurableID,
+			Role:          string(storage.RoleForStorage(t.Type, t.BackingDevice, sysDisks, sysKnown)),
+			TotalBytes:    t.TotalBytes,
+			UsedBytes:     t.UsedBytes,
+			UsedFraction:  t.UsedFraction,
+			GuestAttached: t.MountPath != "" && boundPaths[t.MountPath],
 		}
 		// Inspect the backing device for the UI's data-bearing hint (the authoritative check
 		// is re-run at format time on the actual device).
@@ -140,6 +156,11 @@ func (s *Server) handleDisks(w http.ResponseWriter, r *http.Request, vmid int) {
 				di.DataBearing = true // fail-safe
 				di.DataReason = "could not inspect device"
 			}
+			// F20-BUG2: surface the gate-scheme wipe id (byid:/byuuid:) so a customer-confirmed wipe
+			// binds with the id the gate accepts. Same seam the gate uses → guaranteed to match.
+			if wid, werr := s.deviceDurableID(t.BackingDevice); werr == nil {
+				di.WipeDurableID = wid
+			}
 		}
 		out = append(out, di)
 	}
@@ -266,6 +287,7 @@ func (s *Server) handleDiskGuestAttach(w http.ResponseWriter, r *http.Request, v
 	for key, spec := range mounts {
 		if _, mp, _ := parseMount(spec); mp == where {
 			s.recordIntent(r.Context(), where, "enrolled")
+			s.recordGuestBind(r.Context(), vmid, where)
 			s.logger.Info("local-api: guest-attach idempotent (already bound)", "vmid", vmid, "where", where, "slot", key)
 			writeOK(w, map[string]any{"vmid": vmid, "attached": where, "slot": key, "already": true})
 			return
@@ -281,8 +303,10 @@ func (s *Server) handleDiskGuestAttach(w http.ResponseWriter, r *http.Request, v
 		writeErr(w, http.StatusBadGateway, "guest-attach failed: "+err.Error())
 		return
 	}
-	// Record the drive as ENROLLED so the self-heal watchdog will reconcile it (P3).
+	// Record the drive as ENROLLED so the self-heal watchdog will reconcile it (P3), and persist the
+	// per-guest bind so the startup re-assert can restore it after a re-provision (F9).
 	s.recordIntent(r.Context(), where, "enrolled")
+	s.recordGuestBind(r.Context(), vmid, where)
 	writeOK(w, map[string]any{"vmid": vmid, "attached": where, "slot": slot})
 }

@@ -402,6 +426,44 @@ type PendingOp struct {
 	FSType    string `json:"fstype"`     // the filesystem to mkfs after the wipe
 }

+// errFormatClientGone signals the request context was cancelled (client/controller deadline) while the
+// detached mkfs keeps running — the handler returns without writing; the job record records the outcome.
+var errFormatClientGone = fmt.Errorf("format client gone (mkfs continues detached)")
+
+// awaitFormat waits for the detached mkfs result, OR returns errFormatClientGone if the request context
+// is cancelled first. Crucially the mkfs itself runs off s.baseCtx, so a cancelled request never kills it
+// (F20-BUG3) — abandoning the wait here only abandons the HTTP response, not the format.
+func (s *Server) awaitFormat(reqCtx context.Context, done <-chan error, vmid int, device string) error {
+	select {
+	case err := <-done:
+		return err
+	case <-reqCtx.Done():
+		s.logger.Warn("local-api: format client disconnected — mkfs continues detached (poll GET /disks/format/status)",
+			"vmid", vmid, "device", device)
+		return errFormatClientGone
+	}
+}
+
+// handleDiskFormatStatus reports the most-recent/in-flight format job (F20-BUG3), so a controller whose
+// request timed out (or that reconnects after an agent restart) can learn the real outcome instead of
+// assuming failure. Self-scoped (benign read).
+func (s *Server) handleDiskFormatStatus(w http.ResponseWriter, r *http.Request, vmid int) {
+	if s.formatJobs == nil {
+		writeOK(w, map[string]any{"vmid": vmid, "phase": "idle"})
+		return
+	}
+	job := s.formatJobs.get()
+	if job == nil {
+		writeOK(w, map[string]any{"vmid": vmid, "phase": "idle"})
+		return
+	}
+	writeOK(w, map[string]any{
+		"vmid": vmid, "phase": job.Phase, "device": job.Device, "fstype": job.FSType,
+		"durable_id": job.DurableID, "error": job.Error, "started_at": job.StartedAt, "updated_at": job.UpdatedAt,
+		"job_id": job.JobID,
+	})
+}
+
 // handleDiskFormat is the security centerpiece. The agent INSPECTS the device; if it is
 // data-bearing it is classified destructive and the gate refuses it `pending_signature` — the
 // caller's claim is never trusted. Only a device the agent itself reads as blank is formatted.
@@ -433,8 +495,14 @@ func (s *Server) handleDiskFormat(w http.ResponseWriter, r *http.Request, vmid i
 		// inspect error → fail-safe data-bearing (probe.DataBearing() is true on !Probed)
 	}
 	if !probe.DataBearing() {
-		// Blank device → benign → mkfs (role is irrelevant; there is nothing to destroy).
-		if err := s.disks.Format(r.Context(), req.Device, req.FSType); err != nil {
+		// Blank device → benign → mkfs (role is irrelevant; there is nothing to destroy). F20-BUG3: run
+		// it DETACHED off s.baseCtx so a request/client deadline can't SIGKILL mkfs mid-write; we still
+		// wait here to return the synchronous result (backward-compatible with the controller's client).
+		done := s.startFormatDetached(req.Device, "", req.FSType)
+		if err := s.awaitFormat(r.Context(), done, vmid, req.Device); err != nil {
+			if err == errFormatClientGone {
+				return // client gone; mkfs continues detached + the job record records the outcome
+			}
 			s.logger.Error("local-api: format", "vmid", vmid, "device", req.Device, "err", err)
 			writeErr(w, http.StatusBadGateway, "format failed: "+err.Error())
 			return
@@ -447,7 +515,7 @@ func (s *Server) handleDiskFormat(w http.ResponseWriter, r *http.Request, vmid i
 	// never the caller's claim). The agent also re-resolves the device's durable id; the customer's
 	// confirmation must bind to it.
 	role := s.deviceRole(r.Context(), req.Device)
-	deviceDurable, derr := storage.DeviceDurableID(req.Device)
+	deviceDurable, derr := s.deviceDurableID(req.Device)
 	if derr != nil {
 		deviceDurable = "" // refusal still stands; binding/pending-op just lack the id
 	}
@@ -473,7 +541,14 @@ func (s *Server) handleDiskFormat(w http.ResponseWriter, r *http.Request, vmid i
 				"wipe refused (device may have changed since confirmation): "+rerr.Error())
 			return
 		}
-		if err := s.disks.Format(r.Context(), device, req.FSType); err != nil {
+		// F20-BUG3: run the destructive mkfs DETACHED off s.baseCtx (bound durable id recorded for
+		// restart-recovery), so a request/client deadline can never SIGKILL it mid-write and corrupt the
+		// disk. We still wait to return the synchronous result (backward-compatible with the controller).
+		done := s.startFormatDetached(device, deviceDurable, req.FSType)
+		if err := s.awaitFormat(r.Context(), done, vmid, device); err != nil {
+			if err == errFormatClientGone {
+				return // client gone; the wipe continues detached + survives a restart via the job record
+			}
 			s.logger.Error("local-api: customer-confirmed format", "vmid", vmid, "device", device, "err", err)
 			writeErr(w, http.StatusBadGateway, "format failed: "+err.Error())
 			return
@@ -517,6 +592,108 @@ func (s *Server) handleDiskFormat(w http.ResponseWriter, r *http.Request, vmid i
 		"device is system/backup-protected — format requires an operator signature ("+dec.Reason+")")
 }

+// guestBoundPaths returns the set of guest mountpoint paths (the `mp=` of each entry in the guest's
+// config) — i.e. the host drives actually BOUND into the guest. F9: this is the guest-attached signal
+// (`GuestAttached`) that distinguishes a guest-usable drive from one merely present on the host. A bind
+// created by AttachBind has `mp=<where>` where `where` is the drive's host mount path, so a storage
+// target is guest-attached iff its MountPath is in this set. Best-effort: a config-read error yields an
+// empty set (reported as not-attached — the safe direction).
+func (s *Server) guestBoundPaths(ctx context.Context, vmid int) map[string]bool {
+	out := map[string]bool{}
+	if s.guests == nil {
+		return out
+	}
+	cfg, err := s.guests.GuestConfig(ctx, vmid)
+	if err != nil {
+		s.logger.Warn("local-api: guest-attached check — could not read guest config", "vmid", vmid, "err", err)
+		return out
+	}
+	for _, spec := range cfg.MountPoints() {
+		if _, mp, _ := parseMount(spec); mp != "" {
+			out[mp] = true
+		}
+	}
+	return out
+}
+
+// recordGuestBind persists that the drive at `where` (by its durable-id) is enrolled into `vmid`, so the
+// startup re-assert (ReassertGuestBinds) can restore the bind after a re-provision (F9). Best-effort.
+func (s *Server) recordGuestBind(ctx context.Context, vmid int, where string) {
+	if s.guestBinds == nil {
+		return
+	}
+	id := s.durableIDForMount(ctx, where)
+	if id == "" {
+		s.logger.Warn("local-api: guest-bind not recorded — durable-id unresolved", "vmid", vmid, "where", where)
+		return
+	}
+	if err := s.guestBinds.Record(vmid, id); err != nil {
+		s.logger.Warn("local-api: guest-bind record failed", "vmid", vmid, "where", where, "durable_id", id, "err", err)
+		return
+	}
+	s.logger.Info("local-api: guest-bind recorded for startup re-assert", "vmid", vmid, "where", where, "durable_id", id)
+}
+
+// ReassertGuestBinds re-adds, on agent startup (the host's bring-up/reconcile trigger), any enrolled
+// user-data drive bind a guest is MISSING from its config (F9 — a re-provision drops the mp, and nothing
+// previously restored it). For each recorded (vmid, durable-id): only when the durable-id STILL resolves
+// to a present, mounted drive AND the guest lacks the bind, it re-runs AttachBind. "On durable-id match"
+// — a swapped or absent drive is never auto-bound. The re-added bind is config state; it activates on the
+// guest's next reboot (logged), exactly like the enroll flow. Safe to call repeatedly (idempotent).
+func (s *Server) ReassertGuestBinds(ctx context.Context) {
+	if s.guestBinds == nil || s.guestAttach == nil || s.guests == nil {
+		return
+	}
+	// durable-id -> current host mount path (present drives only), from the agent's own storage view.
+	mountByDurable := map[string]string{}
+	if targets, err := s.storage.Observe(ctx); err == nil {
+		for _, t := range targets {
+			if t.DurableID != "" && t.MountPath != "" {
+				mountByDurable[t.DurableID] = t.MountPath
+			}
+		}
+	} else {
+		s.logger.Warn("F9 re-assert: storage view unavailable — skipping", "err", err)
+		return
+	}
+	for vmid, ids := range s.guestBinds.Guests() {
+		cfg, err := s.guests.GuestConfig(ctx, vmid)
+		if err != nil {
+			s.logger.Warn("F9 re-assert: skip guest (config read failed)", "vmid", vmid, "err", err)
+			continue
+		}
+		mounts := cfg.MountPoints()
+		boundPaths := map[string]bool{}
+		for _, spec := range mounts {
+			if _, mp, _ := parseMount(spec); mp != "" {
+				boundPaths[mp] = true
+			}
+		}
+		for _, id := range ids {
+			where, present := mountByDurable[id]
+			if !present {
+				s.logger.Warn("F9 re-assert: enrolled drive not present (durable-id absent) — skipping", "vmid", vmid, "durable_id", id)
+				continue
+			}
+			if boundPaths[where] {
+				continue // already bound — nothing to re-assert
+			}
+			slot, ok := freeMountSlot(mounts)
+			if !ok {
+				s.logger.Warn("F9 re-assert: no free mountpoint slot on guest", "vmid", vmid, "where", where)
+				continue
+			}
+			if err := s.guestAttach.AttachBind(ctx, vmid, slot, where); err != nil {
+				s.logger.Error("F9 re-assert: AttachBind failed", "vmid", vmid, "where", where, "slot", slot, "err", err)
+				continue
+			}
+			mounts[slot] = where // reserve the slot so a second enrolled drive takes the next one
+			s.logger.Warn("F9 re-assert: re-attached enrolled drive into guest config (reboot to activate)",
+				"vmid", vmid, "where", where, "slot", slot, "durable_id", id)
+		}
+	}
+}
+
 // durableIDForMount resolves the durable-id of the storage mounted at `where` (from the agent's own
 // storage view) — the key the intent store records enroll/eject against. "" if not resolvable.
 func (s *Server) durableIDForMount(ctx context.Context, where string) string {
@@ -0,0 +1,116 @@
+package localapi
+
+import (
+	"encoding/json"
+	"net/http"
+	"testing"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
+	"gitea.dooplex.hu/admin/felhom-agent/internal/storage"
+)
+
+// decodeDisks pulls the disks array out of a GET /disks response.
+func decodeDisks(t *testing.T, body []byte) []DiskInfo {
+	t.Helper()
+	var resp struct {
+		Data struct {
+			Disks []DiskInfo `json:"disks"`
+		} `json:"data"`
+	}
+	if err := json.Unmarshal(body, &resp); err != nil {
+		t.Fatalf("decode /disks: %v (body=%s)", err, string(body))
+	}
+	return resp.Data.Disks
+}
+
+// TestDisks_WipeDurableID_GateScheme asserts F20-BUG2: /disks surfaces a wipe_durable_id in the gate's
+// scheme (byid:/byuuid:, via the SAME s.deviceDurableID seam the format gate uses), DISTINCT from the
+// uuid: durable_id (which feeds /disks/assign). Pre-fix the only id was uuid:, which the gate rejected
+// as a binding_mismatch.
+func TestDisks_WipeDurableID_GateScheme(t *testing.T) {
+	d := &fakeDiskOps{probe: storage.DeviceProbe{Probed: true, HasFilesystem: true, FSType: "ext4"}}
+	sv := fakeStorage{targets: []hub.StorageTarget{
+		{Name: "bulk", Type: hub.StorageTypeUSB, BackingDevice: "/dev/sdb1", MountPath: "/mnt/bulk", DurableID: "uuid:abc-123"},
+	}}
+	h := newDiskServer(t, d, &fakeGate{}, sv, nil)
+
+	w := do(t, h, "GET", "/disks", "A", "")
+	if w.Code != http.StatusOK {
+		t.Fatalf("GET /disks: %d (%s)", w.Code, w.Body.String())
+	}
+	disks := decodeDisks(t, w.Body.Bytes())
+	if len(disks) != 1 {
+		t.Fatalf("want 1 disk, got %d", len(disks))
+	}
+	got := disks[0]
+	// The stub in newDiskServer maps /dev/sdb1 → byid:wwn-sdb1 (the gate scheme).
+	if got.WipeDurableID != "byid:wwn-sdb1" {
+		t.Fatalf("WipeDurableID = %q, want byid:wwn-sdb1 (gate scheme)", got.WipeDurableID)
+	}
+	if got.DurableID != "uuid:abc-123" {
+		t.Fatalf("DurableID = %q, want uuid:abc-123 (assign scheme, unchanged)", got.DurableID)
+	}
+	if got.WipeDurableID == got.DurableID {
+		t.Fatal("wipe id must differ from the assign (uuid:) id")
+	}
+}
+
+// TestDisks_WipeID_MatchesGateBinding asserts the BUG2 end-to-end property: when the customer confirms a
+// wipe with the wipe_durable_id surfaced by /disks, the handler derives the device's gate id through the
+// SAME seam — so the value the gate compares as DeviceDurableID equals the customer's ConfirmDurableID
+// (no binding_mismatch). Asserted via the request the handler forwards to the gate.
+func TestDisks_WipeID_MatchesGateBinding(t *testing.T) {
+	d := &fakeDiskOps{probe: storage.DeviceProbe{Probed: true, HasFilesystem: true, FSType: "ext4"}}
+	sv := fakeStorage{targets: []hub.StorageTarget{
+		{Name: "bulk", Type: hub.StorageTypeUSB, BackingDevice: "/dev/sdb1", MountPath: "/mnt/bulk", DurableID: "uuid:abc-123"},
+	}}
+	g := &fakeGate{decision: WipeDecision{Allowed: true, Tier: "customer_confirmable", Reason: "customer_confirmed"}}
+	h := newDiskServer(t, d, g, sv, nil)
+
+	wipeID := decodeDisks(t, do(t, h, "GET", "/disks", "A", "").Body.Bytes())[0].WipeDurableID
+
+	body := `{"device":"/dev/sdb1","fstype":"ext4","confirmed":true,"durable_id":"` + wipeID + `"}`
+	w := do(t, h, "POST", "/disks/format", "A", body)
+	if w.Code != http.StatusOK {
+		t.Fatalf("confirmed wipe with the list's wipe id: %d (%s)", w.Code, w.Body.String())
+	}
+	reqs := g.requests()
+	if len(reqs) != 1 {
+		t.Fatalf("gate consulted %d times, want 1", len(reqs))
+	}
+	// The crux: the customer's confirm id (from the list) equals the device id the gate resolves.
+	if reqs[0].ConfirmDurableID != wipeID {
+		t.Fatalf("ConfirmDurableID forwarded = %q, want the list's wipe id %q", reqs[0].ConfirmDurableID, wipeID)
+	}
+	if reqs[0].DeviceDurableID != reqs[0].ConfirmDurableID {
+		t.Fatalf("gate binding mismatch: device id %q != confirm id %q (BUG2 not fixed)", reqs[0].DeviceDurableID, reqs[0].ConfirmDurableID)
+	}
+}
+
+// TestDisks_GuestAttached asserts F9 reporting: a drive bound into THIS guest's config (mp=<mount_path>)
+// reports guest_attached=true; a host-present-but-unbound drive reports false — the signal that was
+// missing when the HDD looked available but wasn't attached.
+func TestDisks_GuestAttached(t *testing.T) {
+	d := &fakeDiskOps{probe: storage.DeviceProbe{Probed: true, HasFilesystem: true, FSType: "ext4"}}
+	sv := fakeStorage{targets: []hub.StorageTarget{
+		{Name: "usb", Type: hub.StorageTypeUSB, BackingDevice: "/dev/sdb1", MountPath: "/mnt/felhom-usb"},
+		{Name: "extra", Type: hub.StorageTypeUSB, BackingDevice: "/dev/sdc1", MountPath: "/mnt/extra"},
+	}}
+	// Guest 8200 (token "A") has /mnt/felhom-usb bound (Model-A bind: source .../felhom-data, mp=where),
+	// but NOT /mnt/extra.
+	h := newDiskServerWithGuestConfigs(t, d, sv, nil, map[int]map[string]string{
+		8200: {"mp3": "/mnt/felhom-usb/felhom-data,mp=/mnt/felhom-usb"},
+	})
+
+	disks := decodeDisks(t, do(t, h, "GET", "/disks", "A", "").Body.Bytes())
+	got := map[string]bool{}
+	for _, di := range disks {
+		got[di.MountPath] = di.GuestAttached
+	}
+	if !got["/mnt/felhom-usb"] {
+		t.Errorf("/mnt/felhom-usb should be guest_attached=true (bound into the guest)")
+	}
+	if got["/mnt/extra"] {
+		t.Errorf("/mnt/extra should be guest_attached=false (host-present but not bound)")
+	}
+}
@@ -118,6 +118,9 @@ func newDiskServer(t *testing.T, d *fakeDiskOps, g *fakeGate, sv StorageView, gl
 	// device the format tests use; antiRetargetResolve itself is covered directly
 	// in wipe_reresolve_test.go.
 	srv.reresolveWipe = func(_ context.Context, _ string) (string, error) { return "/dev/sdb", nil }
+	// F20-BUG2: the wipe id derivation hits /dev/disk/by-* in production; stub it deterministically so
+	// both the /disks list and the gate (which share this seam) resolve the same id in tests.
+	srv.deviceDurableID = func(device string) (string, error) { return "byid:wwn-" + strings.TrimPrefix(device, "/dev/"), nil }
 	return srv.Handler()
 }

@@ -0,0 +1,174 @@
+package localapi
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sync"
+	"time"
+)
+
+// formatJob is the persisted record of the most recent / in-flight disk format (F20-BUG3). It exists so
+// that (a) an mkfs runs DETACHED from the HTTP request — a client/request deadline can no longer SIGKILL
+// an in-progress mkfs and corrupt the disk — and (b) an in-progress format SURVIVES an agent restart:
+// on boot, a record still in `running` is re-resolved by durable-id and re-run (mkfs is idempotent).
+type formatJob struct {
+	JobID     string `json:"job_id"`
+	Device    string `json:"device"`
+	DurableID string `json:"durable_id"` // "" for a blank (benign) format — never auto-recovered
+	FSType    string `json:"fstype"`
+	Phase     string `json:"phase"` // running | done | failed
+	Error     string `json:"error,omitempty"`
+	StartedAt string `json:"started_at"`
+	UpdatedAt string `json:"updated_at"`
+}
+
+const (
+	formatPhaseRunning = "running"
+	formatPhaseDone    = "done"
+	formatPhaseFailed  = "failed"
+)
+
+// FormatJobStore persists the single most-recent format job (atomic tmp+rename, 0600). One slot: a host
+// formats one device at a time. Mirrors storage.IntentStore.
+type FormatJobStore struct {
+	path string
+	mu   sync.Mutex
+	cur  *formatJob
+}
+
+// OpenFormatJobStore loads (or initializes) the store. Missing file = no job; corrupt file = error.
+func OpenFormatJobStore(path string) (*FormatJobStore, error) {
+	s := &FormatJobStore{path: path}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return s, nil
+		}
+		return nil, fmt.Errorf("format-job store: read %s: %w", path, err)
+	}
+	if len(data) > 0 {
+		var j formatJob
+		if err := json.Unmarshal(data, &j); err != nil {
+			return nil, fmt.Errorf("format-job store: parse %s: %w", path, err)
+		}
+		s.cur = &j
+	}
+	return s, nil
+}
+
+func (s *FormatJobStore) get() *formatJob {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.cur == nil {
+		return nil
+	}
+	cp := *s.cur
+	return &cp
+}
+
+func (s *FormatJobStore) save(j *formatJob) error {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	cp := *j
+	s.cur = &cp
+	data, err := json.MarshalIndent(s.cur, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(s.path), 0o755); err != nil {
+		return err
+	}
+	tmp := s.path + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o600); err != nil {
+		os.Remove(tmp)
+		return err
+	}
+	return os.Rename(tmp, s.path)
+}
+
+// startFormatDetached persists a `running` record and runs mkfs in a goroutine off s.baseCtx (NOT the
+// request context), with a long bound. It returns a channel that yields the format error (nil on
+// success). The caller may stop waiting (client disconnect) without killing the mkfs — the goroutine
+// runs to completion and records the outcome. device is the ALREADY anti-retarget-resolved device; the
+// record carries durableID so a restart can re-resolve + re-run.
+func (s *Server) startFormatDetached(device, durableID, fstype string) <-chan error {
+	base := s.baseCtx
+	if base == nil {
+		base = context.Background()
+	}
+	job := &formatJob{
+		JobID: s.nowFn().UTC().Format("20060102T150405Z"), Device: device, DurableID: durableID,
+		FSType: fstype, Phase: formatPhaseRunning,
+		StartedAt: s.nowFn().UTC().Format(time.RFC3339), UpdatedAt: s.nowFn().UTC().Format(time.RFC3339),
+	}
+	if s.formatJobs != nil {
+		if err := s.formatJobs.save(job); err != nil {
+			s.logger.Warn("format-job: could not persist running record (format will still run)", "device", device, "err", err)
+		}
+	}
+	done := make(chan error, 1)
+	go func() {
+		ctx, cancel := context.WithTimeout(base, 60*time.Minute)
+		defer cancel()
+		err := s.disks.Format(ctx, device, fstype)
+		s.finishFormatJob(job, err)
+		done <- err
+	}()
+	return done
+}
+
+// finishFormatJob updates the persisted record to done/failed.
+func (s *Server) finishFormatJob(job *formatJob, err error) {
+	if s.formatJobs == nil {
+		return
+	}
+	job.UpdatedAt = s.nowFn().UTC().Format(time.RFC3339)
+	if err != nil {
+		job.Phase = formatPhaseFailed
+		job.Error = err.Error()
+	} else {
+		job.Phase = formatPhaseDone
+	}
+	if serr := s.formatJobs.save(job); serr != nil {
+		s.logger.Warn("format-job: could not persist final record", "device", job.Device, "phase", job.Phase, "err", serr)
+	}
+}
+
+// RecoverFormatJob, on agent startup, completes a format that an agent restart interrupted (F20-BUG3 +
+// the operator's "survive a restart" decision). A record still in `running` is re-resolved by its
+// durable-id (anti-retarget — a swapped/absent disk is NOT re-formatted) and the mkfs is re-run detached
+// (mkfs is idempotent). A blank (no-durable-id) format is NOT auto-re-run — it is marked failed for the
+// caller to retry, so recovery never formats a mutable /dev path.
+func (s *Server) RecoverFormatJob(ctx context.Context) {
+	if s.formatJobs == nil {
+		return
+	}
+	job := s.formatJobs.get()
+	if job == nil || job.Phase != formatPhaseRunning {
+		return
+	}
+	if job.DurableID == "" {
+		s.logger.Warn("format-job recover: interrupted blank format — marking failed (retry needed; not auto-re-running a path-bound format)", "device", job.Device)
+		s.finishFormatJob(job, fmt.Errorf("interrupted by agent restart; retry the format"))
+		return
+	}
+	device, err := s.reresolveWipe(ctx, job.DurableID)
+	if err != nil {
+		s.logger.Warn("format-job recover: durable-id no longer resolves — NOT re-formatting (anti-retarget)", "durable_id", job.DurableID, "err", err)
+		s.finishFormatJob(job, fmt.Errorf("durable-id %s did not re-resolve after restart: %w", job.DurableID, err))
+		return
+	}
+	s.logger.Warn("format-job recover: re-running interrupted format detached", "durable_id", job.DurableID, "device", device, "fstype", job.FSType)
+	_ = s.startFormatDetached(device, job.DurableID, job.FSType) // detached; updates the record on completion
+}
+
+// nowFn returns the server clock (testable), defaulting to time.Now.
+func (s *Server) nowFn() time.Time {
+	if s.now != nil {
+		return s.now()
+	}
+	return time.Now()
+}
@@ -0,0 +1,168 @@
+package localapi
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"log/slog"
+	"net/http"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/storage"
+)
+
+func tempFormatStore(t *testing.T) *FormatJobStore {
+	t.Helper()
+	fj, err := OpenFormatJobStore(filepath.Join(t.TempDir(), "format-job.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return fj
+}
+
+// formatServer builds a *Server with the destructive-format path wired (data-bearing probe, a gate, the
+// format-job store), plus the test stubs (reresolveWipe/deviceDurableID) so no real /dev is touched.
+func formatServer(t *testing.T, d *fakeDiskOps, g StorageGate, fj *FormatJobStore) *Server {
+	t.Helper()
+	srv, err := NewServer(Options{
+		ListenAddr: "127.0.0.1:0", Guests: &fakeGuests{}, Backups: &fakeBackups{}, Store: &fakeStore{},
+		Storage: fakeStorage{}, Tokens: staticTokens{"A": 8200},
+		Disks: d, DiskGate: g, FormatJobs: fj, HostReader: sysOnSDA(),
+		Logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	srv.baseCtx = context.Background()
+	srv.reresolveWipe = func(_ context.Context, _ string) (string, error) { return "/dev/sdb", nil }
+	srv.deviceDurableID = func(device string) (string, error) { return "byid:wwn-" + device, nil }
+	return srv
+}
+
+func waitFormatPhase(t *testing.T, fj *FormatJobStore, want string) *formatJob {
+	t.Helper()
+	deadline := time.Now().Add(2 * time.Second)
+	for time.Now().Before(deadline) {
+		if j := fj.get(); j != nil && j.Phase == want {
+			return j
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	got := fj.get()
+	t.Fatalf("format job did not reach phase %q in time (got %+v)", want, got)
+	return nil
+}
+
+// TestFormat_DetachedPersistsJobRecord asserts F20-BUG3: a customer-confirmed wipe runs through the
+// detached runner and a persisted job record reaches `done` with the device + durable-id bound (so it
+// can be polled / recovered). Also confirms backward-compat: the handler still returns 200 synchronously.
+func TestFormat_DetachedPersistsJobRecord(t *testing.T) {
+	d := &fakeDiskOps{probe: deviceProbeDataBearing()}
+	g := &fakeGate{decision: WipeDecision{Allowed: true, Tier: "customer_confirmable", Reason: "customer_confirmed"}}
+	fj := tempFormatStore(t)
+	srv := formatServer(t, d, g, fj)
+	h := srv.Handler()
+
+	w := do(t, h, "POST", "/disks/format", "A", `{"device":"/dev/sdb1","fstype":"ext4","confirmed":true,"durable_id":"byid:wwn-/dev/sdb1"}`)
+	if w.Code != http.StatusOK {
+		t.Fatalf("confirmed format: %d (%s)", w.Code, w.Body.String())
+	}
+	job := waitFormatPhase(t, fj, formatPhaseDone)
+	if job.Device != "/dev/sdb" { // the anti-retarget re-resolved device (stub returns /dev/sdb)
+		t.Fatalf("job device = %q, want /dev/sdb (re-resolved)", job.Device)
+	}
+	if job.DurableID == "" {
+		t.Fatalf("job durable-id empty — recovery could not re-bind")
+	}
+	if len(d.formatted()) != 1 {
+		t.Fatalf("mkfs called %d times, want 1", len(d.formatted()))
+	}
+}
+
+// TestFormatStatus reports the persisted job via GET /disks/format/status.
+func TestFormatStatus(t *testing.T) {
+	d := &fakeDiskOps{probe: deviceProbeDataBearing()}
+	g := &fakeGate{decision: WipeDecision{Allowed: true, Tier: "customer_confirmable", Reason: "customer_confirmed"}}
+	fj := tempFormatStore(t)
+	srv := formatServer(t, d, g, fj)
+	h := srv.Handler()
+
+	do(t, h, "POST", "/disks/format", "A", `{"device":"/dev/sdb1","fstype":"ext4","confirmed":true,"durable_id":"byid:wwn-/dev/sdb1"}`)
+	waitFormatPhase(t, fj, formatPhaseDone)
+
+	w := do(t, h, "GET", "/disks/format/status", "A", "")
+	if w.Code != http.StatusOK {
+		t.Fatalf("status: %d", w.Code)
+	}
+	var resp struct {
+		Data struct {
+			Phase  string `json:"phase"`
+			Device string `json:"device"`
+		} `json:"data"`
+	}
+	_ = json.Unmarshal(w.Body.Bytes(), &resp)
+	if resp.Data.Phase != formatPhaseDone {
+		t.Fatalf("status phase = %q, want done", resp.Data.Phase)
+	}
+}
+
+// TestRecoverFormatJob_ReRunsInterrupted asserts the operator's "survive an agent restart" decision: a
+// record left in `running` (agent died mid-format) is re-resolved by durable-id and the mkfs re-run.
+func TestRecoverFormatJob_ReRunsInterrupted(t *testing.T) {
+	d := &fakeDiskOps{probe: deviceProbeDataBearing()}
+	fj := tempFormatStore(t)
+	// Pre-seed an interrupted, durable-id-bound running job (as if the agent died mid-mkfs).
+	if err := fj.save(&formatJob{JobID: "j1", Device: "/dev/sdb", DurableID: "byid:wwn-x", FSType: "ext4", Phase: formatPhaseRunning}); err != nil {
+		t.Fatal(err)
+	}
+	srv := formatServer(t, d, &fakeGate{}, fj)
+
+	srv.RecoverFormatJob(context.Background())
+	waitFormatPhase(t, fj, formatPhaseDone)
+	if got := d.formatted(); len(got) != 1 || got[0] != "/dev/sdb" {
+		t.Fatalf("recovery should have re-run mkfs on /dev/sdb (re-resolved), got %v", got)
+	}
+}
+
+// TestRecoverFormatJob_SkipsBlank: an interrupted BLANK (no durable-id) format is NOT auto-re-run (never
+// format a mutable /dev path on recovery) — it is marked failed for the caller to retry.
+func TestRecoverFormatJob_SkipsBlank(t *testing.T) {
+	d := &fakeDiskOps{probe: deviceProbeDataBearing()}
+	fj := tempFormatStore(t)
+	_ = fj.save(&formatJob{JobID: "j2", Device: "/dev/sdb", DurableID: "", FSType: "ext4", Phase: formatPhaseRunning})
+	srv := formatServer(t, d, &fakeGate{}, fj)
+
+	srv.RecoverFormatJob(context.Background())
+	if got := d.formatted(); len(got) != 0 {
+		t.Fatalf("recovery must NOT re-run a path-bound (blank) format, but mkfs ran: %v", got)
+	}
+	if j := fj.get(); j == nil || j.Phase != formatPhaseFailed {
+		t.Fatalf("blank interrupted job should be marked failed, got %+v", j)
+	}
+}
+
+// TestRecoverFormatJob_SkipsUnresolvable: if the durable-id no longer resolves (drive removed/replaced),
+// recovery must NOT format anything (anti-retarget) and marks the job failed.
+func TestRecoverFormatJob_SkipsUnresolvable(t *testing.T) {
+	d := &fakeDiskOps{probe: deviceProbeDataBearing()}
+	fj := tempFormatStore(t)
+	_ = fj.save(&formatJob{JobID: "j3", Device: "/dev/sdb", DurableID: "byid:wwn-gone", FSType: "ext4", Phase: formatPhaseRunning})
+	srv := formatServer(t, d, &fakeGate{}, fj)
+	srv.reresolveWipe = func(_ context.Context, _ string) (string, error) {
+		return "", context.DeadlineExceeded // simulate "durable-id no longer resolves"
+	}
+
+	srv.RecoverFormatJob(context.Background())
+	if got := d.formatted(); len(got) != 0 {
+		t.Fatalf("recovery must NOT format when the durable-id is unresolvable: %v", got)
+	}
+	if j := fj.get(); j == nil || j.Phase != formatPhaseFailed {
+		t.Fatalf("unresolvable interrupted job should be marked failed, got %+v", j)
+	}
+}
+
+func deviceProbeDataBearing() storage.DeviceProbe {
+	return storage.DeviceProbe{Probed: true, HasFilesystem: true, FSType: "ext4"}
+}
@@ -0,0 +1,126 @@
+package localapi
+
+import (
+	"context"
+	"io"
+	"log/slog"
+	"path/filepath"
+	"testing"
+
+	"gitea.dooplex.hu/admin/felhom-agent/internal/hub"
+)
+
+func tempBindStore(t *testing.T) *GuestBindStore {
+	t.Helper()
+	gb, err := OpenGuestBindStore(filepath.Join(t.TempDir(), "guest-binds.json"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return gb
+}
+
+func reassertServer(t *testing.T, ga GuestAttacher, sv StorageView, mounts map[int]map[string]string, gb *GuestBindStore) *Server {
+	t.Helper()
+	srv, err := NewServer(Options{
+		ListenAddr: "127.0.0.1:0",
+		Guests:     &fakeGuestsCfg{mounts: mounts},
+		Backups:    &fakeBackups{}, Store: &fakeStore{},
+		Storage: sv, Tokens: staticTokens{"A": 8200},
+		GuestAttach: ga, GuestBinds: gb,
+		Logger: slog.New(slog.NewTextHandler(io.Discard, nil)),
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	srv.baseCtx = context.Background()
+	return srv
+}
+
+// usbPresent is a storage view with felhom-usb present at /mnt/felhom-usb (durable uuid:usb-1).
+func usbPresent() fakeStorage {
+	return fakeStorage{targets: []hub.StorageTarget{
+		{Name: "usb", Type: hub.StorageTypeUSB, BackingDevice: "/dev/sdb1", MountPath: "/mnt/felhom-usb", DurableID: "uuid:usb-1"},
+	}}
+}
+
+// TestReassertGuestBinds_RestoresMissingBind is the F9 core proof (the operator's "fire the real
+// trigger" requirement): an enrolled drive that is present on the host but MISSING from the guest config
+// (the post-re-provision gap) is auto-re-attached on the startup re-assert — with NO manual guest-attach
+// call. Fails on the pre-fix code (no re-assert existed).
+func TestReassertGuestBinds_RestoresMissingBind(t *testing.T) {
+	gb := tempBindStore(t)
+	if err := gb.Record(8200, "uuid:usb-1"); err != nil { // enrolled at a prior boot
+		t.Fatal(err)
+	}
+	ga := &fakeGuestAttacher{}
+	// guest 8200 has docker-data only — the felhom-usb bind was dropped by the re-provision.
+	srv := reassertServer(t, ga, usbPresent(), map[int]map[string]string{
+		8200: {"mp0": "local-lvm:8,mp=/var/lib/docker"},
+	}, gb)
+
+	srv.ReassertGuestBinds(context.Background())
+
+	if ga.count() != 1 {
+		t.Fatalf("AttachBind called %d times, want 1 (auto-re-assert on startup)", ga.count())
+	}
+	if ga.calls[0].vmid != 8200 || ga.calls[0].where != "/mnt/felhom-usb" {
+		t.Fatalf("re-asserted bind = %+v, want vmid 8200 where /mnt/felhom-usb", ga.calls[0])
+	}
+}
+
+// TestReassertGuestBinds_SkipsAbsentDurable: an enrolled drive whose durable-id is NOT currently present
+// (unplugged / swapped for a different disk) must NOT be auto-bound — the "on durable-id match" safety.
+func TestReassertGuestBinds_SkipsAbsentDurable(t *testing.T) {
+	gb := tempBindStore(t)
+	_ = gb.Record(8200, "uuid:usb-1")
+	ga := &fakeGuestAttacher{}
+	srv := reassertServer(t, ga, fakeStorage{}, map[int]map[string]string{ // empty storage view → absent
+		8200: {"mp0": "local-lvm:8,mp=/var/lib/docker"},
+	}, gb)
+
+	srv.ReassertGuestBinds(context.Background())
+	if ga.count() != 0 {
+		t.Fatalf("AttachBind called %d times — must NOT auto-bind an absent/swapped drive", ga.count())
+	}
+}
+
+// TestReassertGuestBinds_SkipsAlreadyBound: when the guest already has the bind, the re-assert is a no-op.
+func TestReassertGuestBinds_SkipsAlreadyBound(t *testing.T) {
+	gb := tempBindStore(t)
+	_ = gb.Record(8200, "uuid:usb-1")
+	ga := &fakeGuestAttacher{}
+	srv := reassertServer(t, ga, usbPresent(), map[int]map[string]string{
+		8200: {"mp0": "local-lvm:8,mp=/var/lib/docker", "mp3": "/mnt/felhom-usb/felhom-data,mp=/mnt/felhom-usb"},
+	}, gb)
+
+	srv.ReassertGuestBinds(context.Background())
+	if ga.count() != 0 {
+		t.Fatalf("AttachBind called %d times — already bound, must be a no-op", ga.count())
+	}
+}
+
+// TestGuestBindStore_Persist round-trips the store across reopen (the record must survive an agent
+// restart, since that is exactly when the re-assert runs).
+func TestGuestBindStore_Persist(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "guest-binds.json")
+	gb, err := OpenGuestBindStore(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_ = gb.Record(8200, "uuid:usb-1")
+	_ = gb.Record(8200, "uuid:usb-1") // idempotent
+	_ = gb.Record(9300, "byid:wwn-x")
+
+	re, err := OpenGuestBindStore(path) // simulate restart
+	if err != nil {
+		t.Fatal(err)
+	}
+	g := re.Guests()
+	if len(g[8200]) != 1 || g[8200][0] != "uuid:usb-1" {
+		t.Fatalf("vmid 8200 = %v, want [uuid:usb-1]", g[8200])
+	}
+	if len(g[9300]) != 1 || g[9300][0] != "byid:wwn-x" {
+		t.Fatalf("vmid 9300 = %v, want [byid:wwn-x]", g[9300])
+	}
+}
@@ -0,0 +1,103 @@
+package localapi
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"sync"
+)
+
+// GuestBindStore persists, per guest, the DURABLE-IDs of the user-data drives enrolled (guest-attached)
+// into it. F9: the in-guest bind (`pct set -mpN`) is config state that does NOT survive a destroy +
+// re-provision, and nothing re-asserted it — so a re-provisioned guest came up with the HDD unattached
+// even though it had been enrolled. This store is the record the startup re-assert (ReassertGuestBinds)
+// replays: for each enrolled durable-id still physically present, re-add the bind if the guest lacks it.
+//
+// Keyed by durable-id (NOT host path or sdX) so the re-assert is "on durable-id match" — a swapped or
+// absent drive is never auto-bound. Thread-safe; atomic file writes (tmp+rename), 0600. Mirrors
+// storage.IntentStore.
+type GuestBindStore struct {
+	path string
+	mu   sync.Mutex
+	m    map[int][]string // vmid -> sorted set of enrolled durable-ids
+}
+
+// OpenGuestBindStore loads (or initializes) the store. Missing file = empty store; corrupt file = error
+// (fail loud — losing a bind record would silently drop the re-assert).
+func OpenGuestBindStore(path string) (*GuestBindStore, error) {
+	s := &GuestBindStore{path: path, m: map[int][]string{}}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return s, nil
+		}
+		return nil, fmt.Errorf("guest-bind store: read %s: %w", path, err)
+	}
+	if len(data) > 0 {
+		// stored as {"<vmid>": ["durable-id", ...]} (string keys — JSON object keys are strings)
+		raw := map[string][]string{}
+		if err := json.Unmarshal(data, &raw); err != nil {
+			return nil, fmt.Errorf("guest-bind store: parse %s: %w", path, err)
+		}
+		for k, v := range raw {
+			vmid, err := strconv.Atoi(k)
+			if err != nil {
+				return nil, fmt.Errorf("guest-bind store: bad vmid key %q: %w", k, err)
+			}
+			s.m[vmid] = v
+		}
+	}
+	return s, nil
+}
+
+// Record adds (vmid, durableID) to the enrolled set. Idempotent — no write if already present. A blank
+// durable-id is refused (the re-assert must never act on a drive whose identity it can't pin).
+func (s *GuestBindStore) Record(vmid int, durableID string) error {
+	if durableID == "" {
+		return fmt.Errorf("guest-bind store: refusing to record an empty durable-id for vmid %d", vmid)
+	}
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	for _, id := range s.m[vmid] {
+		if id == durableID {
+			return nil // idempotent
+		}
+	}
+	s.m[vmid] = append(s.m[vmid], durableID)
+	sort.Strings(s.m[vmid])
+	return s.saveLocked()
+}
+
+// Guests returns a copy of the vmid → enrolled-durable-ids map.
+func (s *GuestBindStore) Guests() map[int][]string {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	out := make(map[int][]string, len(s.m))
+	for vmid, ids := range s.m {
+		out[vmid] = append([]string(nil), ids...)
+	}
+	return out
+}
+
+func (s *GuestBindStore) saveLocked() error {
+	raw := make(map[string][]string, len(s.m))
+	for vmid, ids := range s.m {
+		raw[strconv.Itoa(vmid)] = ids
+	}
+	data, err := json.MarshalIndent(raw, "", "  ")
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(filepath.Dir(s.path), 0o755); err != nil {
+		return err
+	}
+	tmp := s.path + ".tmp"
+	if err := os.WriteFile(tmp, data, 0o600); err != nil {
+		os.Remove(tmp)
+		return err
+	}
+	return os.Rename(tmp, s.path)
+}
@@ -87,6 +87,14 @@ type Options struct {
 	// Intent records drive enroll/eject intent for the self-heal watchdog (slice 10 P3). OPTIONAL —
 	// when nil, no intent is recorded (self-heal runs ungated).
 	Intent IntentRecorder
+	// GuestBinds persists which user-data drives (by durable-id) are enrolled into each guest, so the
+	// startup re-assert (ReassertGuestBinds) can restore a bind that a re-provision dropped (F9).
+	// OPTIONAL — when nil, guest binds are not recorded and the startup re-assert is a no-op.
+	GuestBinds *GuestBindStore
+	// FormatJobs persists the in-flight/last disk-format job so mkfs runs detached from the request
+	// (F20-BUG3: a request deadline can't kill it) and survives an agent restart (RecoverFormatJob).
+	// OPTIONAL — when nil, formats still run detached but are not persisted/recovered.
+	FormatJobs *FormatJobStore
 	// HostReader is the root-free host topology reader used to classify a device/mount's protection
 	// ROLE (it backs SystemDisks for the eject role-gate + the /disks role hints). OPTIONAL — when nil
 	// it defaults to the production *storage.ProcHostReader. Injectable so the role-gate is testable.
@@ -143,6 +151,8 @@ type Server struct {
 	guestList   GuestLister        // slice 8C (optional)
 	guestAttach GuestAttacher      // slice 10 P2 (optional)
 	intent      IntentRecorder     // slice 10 P3 (optional)
+	guestBinds  *GuestBindStore    // F9 startup bind re-assert record (optional)
+	formatJobs  *FormatJobStore    // F20-BUG3 detached-format job record (optional)
 	host        storage.HostReader // role classification source (optional; defaults to ProcHostReader)

 	hostMetrics HostMetricsProvider // slice 9 (optional)
@@ -154,6 +164,13 @@ type Server struct {
 	// override it to avoid touching real /dev.
 	reresolveWipe func(ctx context.Context, durableID string) (string, error)

+	// deviceDurableID derives the WIPE-binding durable id of a block device (the byid:/byuuid: scheme
+	// the wipe gate resolves against). F20-BUG2: BOTH the /disks list (DiskInfo.WipeDurableID) and the
+	// format gate use this single seam, so the id the customer copies from the list is exactly the id
+	// the gate accepts (no more uuid: vs byid: binding_mismatch). Defaults to storage.DeviceDurableID;
+	// tests override it. (DiskInfo.DurableID stays the uuid: storage id — that one feeds /disks/assign.)
+	deviceDurableID func(device string) (string, error)
+
 	jobsMu sync.Mutex
 	jobs   map[int]*backupJob // per-guest backup job state (slice 8B)

@@ -191,12 +208,15 @@ func NewServer(o Options) (*Server, error) {
 		guestList:   o.Guests2,
 		guestAttach: o.GuestAttach,
 		intent:      o.Intent,
+		guestBinds:  o.GuestBinds,
+		formatJobs:  o.FormatJobs,
 		host:        o.HostReader,
 		hostMetrics: o.HostMetrics,
 		hostID:      o.HostID,
 		jobs:        map[int]*backupJob{},
 	}
 	s.reresolveWipe = s.reresolveDurableForWipe
+	s.deviceDurableID = storage.DeviceDurableID
 	return s, nil
 }

@@ -218,6 +238,7 @@ func (s *Server) Handler() http.Handler {
 	mux.HandleFunc("POST /disks/assign", s.withGuest(s.handleDiskAssign))
 	mux.HandleFunc("POST /disks/eject", s.withGuest(s.handleDiskEject))
 	mux.HandleFunc("POST /disks/format", s.withGuest(s.handleDiskFormat))
+	mux.HandleFunc("GET /disks/format/status", s.withGuest(s.handleDiskFormatStatus))
 	// Guest data-drive passthrough (slice 10 P2): bind an enrolled drive's felhom-data namespace in.
 	mux.HandleFunc("POST /disks/guest-attach", s.withGuest(s.handleDiskGuestAttach))
 	// Guest reboot (slice 10 P2 activation): user-triggered restart to activate pending drive binds.