No board window has shown its NSToolbar or the titlebar board-info
chevron since m6: on macOS 26, SwiftUI stages a scene's content
against a provisional window, then dismantles and re-makes the
window-sensing background view while moving content into the real
window. HostedWindowController.detach() treated that dismantle as the
window's death and discarded the held titlebar accessory and toolbar
controller — so the real window attached moments later to empty slots.
Observed live via instrumented launch: install arrives with no window,
detach follows (slots cleared), then the real window attaches.
detach() now removes the chrome from the window but retains the slots
— their lifetime is the controller's, not the sensing view's — and
attach() reinstalls whatever is held. Verified on a fixture launch:
the board window carries its toolbar and the leading accessory.
Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY
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