v0.238.1: the nightly backup leaves an app alone WHILE it is being updated, not only once it is held (slice 4 follow-up)

Found live in v0.238.0 Scenario F on demo-hp: during an update's 5-minute health wait the app is not
yet held, and the periodic recovery-unit capture at 10:17:09 wrote the never-started definition
(alpine:3.20) into its PRIMARY unit, 53 s before the hold landed. The Tier-2 mirror the hold names
survived only because Tier 2 runs daily; a nightly Tier 2 inside a verify window would have mirrored
the broken definition over the copy the customer is told to restore from.

backup.Manager.isHeld — consulted by the capture sweep, the Tier-2 run and the volume dump — is now
also true while a guarded update is moving the app, via SetUpdatingCheck wired in main.go to
stacks.Manager.IsUpdating. Test with positive control + red-proof; wiring pinned.

Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/backup/backup.go

@@ -170,6 +170,9 @@ type Manager struct {
 	// disconnected) can be unit-tested without Docker. Nil → the real DumpAppVolumesSafe.
 	dumpVolumesSafe func(stackName string) error
 
+	// updatingCheck (slice 4) — nil-safe; see isHeld / SetUpdatingCheck.
+	updatingCheck func(stackName string) bool
+
 	// R-354 volume-REPLAY seam — the mirror of the F17 DB seams above, so the off-site path's new
 	// volume leg is unit-testable without Docker. Nil → the real restoreDockerVolumesFrom.
 	volumeReplayFrom func(stackName, dumpDir string) (int, error)

controller/internal/backup/slice4_update_guard_test.go

@@ -166,3 +166,30 @@ func TestSlice4_NightlyLegsLeaveAHeldAppAlone(t *testing.T) {
 		t.Errorf("positive control: the unheld app must still be mirrored, got %v", mirrored)
 	}
 }
+
+// v0.238.1 — the gap Scenario F found live: during the update's health wait the app is not yet held,
+// and the periodic capture wrote the never-started new definition into its primary unit. An app a
+// guarded update is moving must be left alone by all three nightly legs, exactly like a held one.
+//
+// COMPANION RED-PROOF (REPORT.md): delete the updatingCheck clause from isHeld — the updating app is
+// then dumped, captured and mirrored, and this test fails.
+func TestSlice4_NightlyLegsLeaveAnAppMidUpdateAlone(t *testing.T) {
+	h := newAdmissionHarness(t, "updating", "free")
+	h.m.settings = slice4Settings(t)
+	h.m.SetUpdatingCheck(func(name string) bool { return name == "updating" })
+	h.m.runVolumeDumps()
+	h.m.captureAllRecoveryUnits()
+	var mirrored []string
+	h.m.perAppTier2 = func(name string) error { mirrored = append(mirrored, name); return nil }
+	h.m.RunAllTier2()
+	for _, list := range [][]string{h.volDumped, h.prov.stopped, h.prov.infoHits, mirrored} {
+		for _, n := range list {
+			if n == "updating" {
+				t.Fatalf("a nightly leg touched an app MID-UPDATE (dumped=%v stopped=%v captured=%v mirrored=%v)", h.volDumped, h.prov.stopped, h.prov.infoHits, mirrored)
+			}
+		}
+	}
+	if len(mirrored) != 1 || mirrored[0] != "free" {
+		t.Errorf("positive control: the app not being updated must still be mirrored, got %v", mirrored)
+	}
+}

controller/internal/backup/update_guard.go

@@ -295,10 +295,29 @@ func (m *Manager) HoldAfterFailedUpdate(stackName string, at time.Time, copyDate
 	return nil
 }
 
-// isHeld reports whether an app carries ANY hold. Used by the nightly legs to leave a held app alone.
+// isHeld reports whether the nightly legs must leave an app alone: it carries ANY hold, OR a guarded
+// update is moving it right now.
+//
+// THE SECOND HALF WAS FOUND LIVE, v0.238.0 Scenario F on demo-hp 2026-09-13. During the update's
+// 5-minute health wait the app is not yet held, and the periodic capture ran at 10:17:09 and wrote
+// the NEW definition (alpine:3.20, which never started) into the app's PRIMARY unit, 53 s before the
+// hold landed at 10:18:02. The Tier-2 mirror the hold names was intact only because the Tier-2 run is
+// daily — a nightly Tier-2 falling inside a verify window would have mirrored the broken definition
+// over the very copy the customer is told to restore from. An app mid-update has a restore point that
+// must not move, exactly like a held one.
 func (m *Manager) isHeld(stackName string) bool {
 	held, _ := m.RestoreHoldFor(stackName)
-	return held
+	if held {
+		return true
+	}
+	return m.updatingCheck != nil && m.updatingCheck(stackName)
+}
+
+// SetUpdatingCheck wires the "is a guarded update moving this app" question (stacks.Manager.IsUpdating).
+// INIT-ONLY, in main.go — pinned by TestSlice4_UpdatingCheckIsWiredAtStartup. The backup package cannot
+// import stacks, which is why it is a seam.
+func (m *Manager) SetUpdatingCheck(fn func(stackName string) bool) {
+	m.updatingCheck = fn
 }
 
 // clearUpdateHoldAfterRestore lifts an UPDATE hold once a person has restored the app successfully.