The way back: a node whose placement key is deleted returns to the controller's compositions without a restart, says so in its journal and its have, and answers such a candidate as returning; pin mesh-sdk 472d5f3 (issue 1126, the seed's revert)

The seed's revert (mesh-catalog #526) was refused on 'would stop running node',
while a self-composing node would have refused its placement's absence, kept
what runs and marked every have failed until a restart. endWhenUnplaced ends the
agent's run when the key goes, so it begins again on the controller's
compositions, as at a start without a key; the composer refuses nothing while
unplaced; the node's have says whose compositions it applies (Composes); the
shadow answers a deleted placement Returns, verdict same.

internal/selfcompose/shadow.go

@@ -292,18 +292,11 @@ func (s *Shadow) answerGroup(ctx context.Context, group string) (delivery.Candid
 		running = c.env.Running()
 	}
 	if p, ok := given[node]; ok && p == nil {
-		// The head removes this node's placement file: everything it runs is removed.
-		a := delivery.CandidateAnswer{Head: head, Revision: rev}
-		for _, r := range running {
-			if r.Module == "" {
-				a.Removed = append(a.Removed, delivery.HaveNodeWord)
-			} else {
-				a.Removed = append(a.Removed, r.Module)
-			}
-		}
-		sort.Strings(a.Removed)
-		a.Verdict = delivery.VerdictOf(a)
-		return a, true
+		// The head deletes this node's placement file: the node then returns to the controller's compositions, as one the
+		// catalogue does not place (endWhenUnplaced), and keeps what runs; nothing is removed (issue 1126, the seed's
+		// revert, whose check read "would stop running node").
+		return delivery.CandidateAnswer{Head: head, Revision: rev, Returns: delivery.ReturnsToController,
+			Verdict: delivery.CandidateSame}, true
 	}
 
 	placement := given[node]