Modal takes a required initialFocus (field / close / action), a field that
loads late takes the focus while it still rests on the close button, and
ModalFooter portals a dialog's commit row under the scrolling body from any
depth. The header and footer fades follow the body's scroll timeline, and the
viewport's interactive-widget=resizes-content keeps the footer above an
on-screen keyboard.
Round 5 extracted `ui/dialogFocus` so no shell would hand-roll the focus
contract, then introduced four ways to lose the focus anyway — all four measured
in jsdom against the real components.
**Ownership was narrower than the trap.** `ui/Modal` traps Tab over the whole
dialog on purpose, so a toast's Undo or ✕ stays reachable; ownership was tracked
over the panel alone. Tabbing to that ✕ therefore read as "the user left the
dialog", and since removing a toast fires no `focusin` to re-arm, closing
afterwards skipped the restore and left the focus on <body>. Before this hook
existed the restore was unconditional, so it was a regression.
**A dialog stacked above us is still ours.** A nested `ui/Modal` portals into its
own host, so it is outside the outer dialog's root however wide that scope is
drawn — widening alone could not fix it. Both closing in one commit left the
focus on <body>: the outer skipped its restore, and the child's own target (a
control inside the outer panel) was already detached, because passive cleanups
run parent-first. Ownership now means "inside my dialog, or inside a modal layer
above it", which is what the rule always intended.
**The wizard disagreed with `ui/Modal` on its first line.** `trapTab(e, panel)`,
with neither the dialog-root scope (so its own toast host was outside the cycle
— the connection notice never auto-dismisses, and its ✕ was unreachable from the
keyboard) nor the `container` argument the JSDoc exists for: `panel.contains(
panel)` is true, so focus sitting ON the tabIndex=-1 panel matched no branch and
a Shift+Tab walked into the app behind the scrim. Both call sites now pass the
same three arguments.
**The toast handover was a render-phase read-modify-write.** A `useMemo` read a
module global that the next line overwrote; React re-invokes a component body
and every `useMemo` factory in it on a StrictMode double render, and the LAST
invocation commits — so the second pass re-read what the first had just written,
the takeover host classified its OWN new toast as inherited, and the dev build
behaved exactly like the code round 5 replaced. Snapshotted through a ref keyed
on `isTop`, so a repeated invocation of one render is a no-op.
And the fourth `aria-modal` shell, `Welcome`'s screenshot lightbox, is finally
swept into the same contract: it declared itself a modal dialog while leaving
the focus on the thumbnail behind an 80%-black scrim and letting Tab walk the
landing page underneath.
The headline fix of the previous commit — StrictMode's re-mount taking the focus
off an `autoFocus` field — had no test at all; deleting it left all 1009 green.
It has one now.
9 tests, mutation-checked against 8 mutations, each red on the test that names it.
peter