OS updates, guest fast lane (11 §8 step 2): felhom-os-apply wrapper (R1-R13 refusals, repair first, snapshot.debian.org fallback), FELHOM_OSAPPLY sudoers, the OS leg after the primary backup, hub os_update block + os-report, --selftest=os-update

No automatic undo: a customer guest cannot be snapshotted (R-837, measured).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

internal/localapi/server.go

@@ -160,6 +160,10 @@ type Options struct {
 	// NetStorage is the privileged network-mount (NAS) surface (Part A1). OPTIONAL — when nil, the
 	// /netstorage endpoints report "not configured". Satisfied by *storage.SudoHostOps.
 	NetStorage NetworkStorageOps
+	// AfterPrimaryBackup (agent v0.140.0, `11-os-updates.md` §8 step 2) runs right after a SUCCESSFUL backup on the
+	// PRIMARY tier, inside the backup goroutine and BEFORE the host-wide heavy-op gate is released — so the OS leg
+	// that it starts can never overlap another backup or a restore-test (`11` C10). OPTIONAL — nil → nothing runs.
+	AfterPrimaryBackup func(ctx context.Context, vmid int)
 	// Privileged runs the fenced root wrappers (E-2a: felhom-backup-target-apply). OPTIONAL — when
 	// nil, POST /backup/target reports "not configured". Satisfied by *proxmox.ExecRunner.
 	Privileged PrivilegedRunner
@@ -276,6 +280,7 @@ type Server struct {
 	tiers []BackupTier
 	// inFlight (R-85) is shared with the restore-test scheduler so the two never run together.
 	inFlight *backup.InFlight
+	afterPrimaryBackup func(ctx context.Context, vmid int) // the OS leg (agent v0.140.0); nil = none
 	logger   *slog.Logger
 	now      func() time.Time
 
@@ -469,6 +474,7 @@ func NewServer(o Options) (*Server, error) {
 	// the primary is always first, because that is what the untargeted endpoints act on.
 	s.tiers = normalizeBackupTiers(o.BackupTiers, o.Backups, cadence)
 	s.inFlight = o.InFlight
+	s.afterPrimaryBackup = o.AfterPrimaryBackup
 	if s.backups == nil && len(s.tiers) > 0 {
 		s.backups = s.tiers[0].Service
 	}
@@ -894,6 +900,10 @@ func (s *Server) handleBackup(w http.ResponseWriter, r *http.Request, vmid int)
 		}
 		s.store.RecordBackup(b)
 		s.finishJob(key, jobID, b)
+		// OS leg (agent v0.140.0): after the night's whole-guest copy exists, still holding the heavy-op gate.
+		if b.Success && tier.Primary && s.afterPrimaryBackup != nil {
+			s.afterPrimaryBackup(base, vmid)
+		}
 	}()
 	writeStatus(w, http.StatusAccepted, true, BackupResponse{VMID: vmid, JobID: jobID, Phase: PhaseRunning}, "")
 }
@@ -1465,3 +1475,6 @@ func writeStatus(w http.ResponseWriter, code int, ok bool, data any, errMsg stri
 	w.WriteHeader(code)
 	_ = json.NewEncoder(w).Encode(apiResponse{OK: ok, Data: data, Error: errMsg})
 }
+
+// SetAfterPrimaryBackup wires the hook that runs after a successful primary-tier backup (the OS leg, agent v0.140.0).
+func (s *Server) SetAfterPrimaryBackup(fn func(ctx context.Context, vmid int)) { s.afterPrimaryBackup = fn }