internal/link/serve.go

@@ -668,12 +668,13 @@ func (s *Server) sourceMoved(ctx context.Context, m Control) {
 		return
 	}
 	err := s.upgrader.SourceMoved(ctx, moved)
+	// Left unsettled when the controller is ending, whatever error that gave (the plans' hold returns a bare
+	// context.Canceled): the bus hands it to whatever consumes next, and taking it would lose the merge.
+	if err != nil && ctx.Err() != nil {
+		return
+	}
 	if err != nil && errors.Is(err, ErrTryAgain) {
-		// Left unsettled when the controller is ending (the bus hands it to whatever consumes next, as decide
-		// does) and when the bus will not hold it: taking it would lose the merge.
-		if ctx.Err() != nil {
-			return
-		}
+		// Also left unsettled when the bus will not hold it.
 		delay := MergeRedeliverAfter(m.HeldFor())
 		if held := m.Hold(delay); held != nil {
 			s.log.Printf("%s/%s moved to %.8s and could not be held (%v): %v; left for the bus to hand over again",

internal/link/store_window_test.go

@@ -143,8 +143,9 @@ func TestAMergeIsLeftUnsettledWhenTheControllerEndsOrTheHoldFails(t *testing.T)
 	merged := SourceMoved{Owner: "novox", Repo: "one", Base: "main", Commit: "abcdef0123"}
 	try := errors.Join(ErrTryAgain, errors.New("another controller is working the plans"))
 
+	// The plans' hold returns a bare context.Canceled when the controller is replaced, not ErrTryAgain.
 	s, in := serving()
-	s.upgrader = upgradesWith{err: try}
+	s.upgrader = upgradesWith{err: context.Canceled}
 	to := &settled{}
 	ended, end := context.WithCancel(context.Background())
 	end()