The resize rebuild creates the new virtual display BEFORE retiring the old
one (create-before-drop), so the registry saw a live same-backend sibling —
its own dying predecessor — and told the backend it was not first in group.
Mutter then skipped the Primary/Exclusive apply ("joining an existing
display group — extending") and the retiring owner took the topology with
it: every resize silently demoted the virtual output to an extended,
shell-less desktop. Thread the superseded pool gen through acquire so the
replacement establishes topology, and stop counting kept (Lingering/Pinned)
entries as demoting siblings — no session owns them, so there is no live
desktop to clobber.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
enricobuehlerandClaude Fable 5
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