[toast] Fix re-adding a closing toast

[atomiks]

Fixes #5253

Changes

• Reinitialized retained toast roots when a closing toast is re-added with the same ID.
• Kept content height recalculation from clearing transition state.
• Added regression tests for revived and remounted toast roots.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@5258
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@5258
  

commit: d13d9ea

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[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+196B(+0.04%)	🔺+54B(+0.04%)

Details of bundle changes

Performance

Total duration: 1,398.71 ms +26.65 ms^(+1.9%) | Renders: 78 ⁽⁺⁰⁾ | Paint: 2,209.31 ms +58.84 ms^(+2.7%)

Test	Duration	Renders
Select mount (200 instances)	177.50 ms 🔺+31.79 ms(+21.8%)	3 (+0)
Combobox type — 500 items, narrows to ~11 (type "Row 25")	44.52 ms 🔺+12.10 ms(+37.3%)	15 (+0)
Combobox open — 500 items	47.53 ms 🔺+9.16 ms(+23.9%)	4 (+0)
Checkbox mount (500 instances)	65.96 ms ▼-28.54 ms(-30.2%)	1 (+0)

11 tests within noise — details

Metric alarms

Test	Metric	Change
Select mount (200 instances)	bench:paint	🔺 +40.70 ms
Combobox type — 500 items, narrows to ~11 (type "Row 25")	bench:paint#combobox-open	🔺 +21.02 ms
Combobox type — 500 items, narrows to ~11 (type "Row 25")	bench:paint	🔺 +21.02 ms
Combobox open — 500 items	bench:paint#combobox-open	🔺 +15.21 ms
Combobox open — 500 items	bench:paint	🔺 +15.21 ms

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[Copilot]

Pull request overview

This PR fixes a Toast Manager edge case where re-triggering a toast while it is exiting (same id) could leave the UI in a broken state (incorrect stacking/data-behind behavior and missing content). It does so by ensuring toast roots are properly (re)initialized when a toast is revived, while preventing height recalculation updates from unintentionally clearing transition state.

Changes:

• Reinitialize ToastRoot internal registration (ref/height/transition state) on mount and when a retained root’s toast is revived (transitionStatus: 'starting').
• Stop height recalculation updates from writing transitionStatus: undefined, avoiding unintended transition-state resets during content/height observer updates.
• Add regression tests for reviving a closing toast and for correct re-registration after a toast root remounts (browser-only).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/react/src/toast/store.test.ts	Updates regression coverage to reflect the new “height-only” internal updates.
packages/react/src/toast/root/ToastRoot.tsx	Adds (re)initialization layout effect and refactors height measurement to avoid clearing transition state during height recalculation.
packages/react/src/toast/root/ToastRoot.test.tsx	Adds browser-only regression tests covering revived-toasts and remounted-root registration.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.