[atomiks]

Toast now handles several limit, timer, and focus edge cases that could leave hidden or inactive toasts in the wrong state.

Changes

• Recomputed limited toast state when the provider limit changes.
• Shared limited-state recomputation across add, close, and provider sync paths.
• Reset paused timer state when all active timers are cleared so future toasts can pause and resume normally.
• Only prevented touch scrolling while a toast swipe is active.
• Kept timers paused while the window is blurred, even if mouseleave or blur handlers run.
• Skipped ending and limited toasts when focus enters the viewport.
• Updated Toast docs and API output for the current limit and manager behavior.
• Added regression coverage for Toast root, viewport, content, manager, and store behavior.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4933
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4933
  

commit: 9bc852c

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+442B(+0.10%)	🔺+104B(+0.07%)

Details of bundle changes

Performance

Total duration: 1,380.94 ms +167.95 ms^(+13.8%) | Renders: 50 ⁽⁺⁰⁾ | Paint: 2,081.84 ms +252.13 ms^(+13.8%)

Test	Duration	Renders
Slider mount (300 instances)	202.69 ms 🔺+34.78 ms(+20.7%)	3 (+0)
Scroll Area mount (300 instances)	102.12 ms 🔺+21.56 ms(+26.8%)	3 (+0)
Dialog mount (300 instances)	70.37 ms 🔺+16.11 ms(+29.7%)	1 (+0)
Mixed surface mount (app-like density)	85.70 ms 🔺+15.35 ms(+21.8%)	5 (+0)
Tooltip mount (300 contained roots)	63.31 ms 🔺+10.60 ms(+20.1%)	1 (+0)

7 tests within noise — details

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[flaviendelangle]

Critical Issues

None — the PR is mergeable as is.

Important Issues

1. clearTimer reset bypassed when timer fires for a removed toast — packages/react/src/toast/store.ts:444-447, :411-419, :312-318
scheduleTimer and resumeTimers inline this.timers.delete(id); callback() instead of routing through clearTimer. closeToast then early-returns at :314 if the toast was concurrently removed via removeToast — so the areTimersPaused = false reset never happens, re-introducing the bug this PR fixes. Narrow path (requires external removeToast of a toast with a running timer), but easy to close: extract private onTimerFired(id) { this.timers.delete(id); if (this.timers.size === 0) this.areTimersPaused = false; } and call it from both inline callbacks.

2. store.handleDocumentPointerDown and ToastViewport.handleKeyDown (Shift+Tab) still call resumeTimers() unconditionally — store.ts:425-437, ToastViewport.tsx:152-162
   The PR added resumeTimersIfWindowFocused to handleMouseLeave/handleBlur but didn't apply the same gate elsewhere. Likely intentional (these paths imply explicit user activity), but worth confirming; if intentional, a one-line comment explains the asymmetry.

3. Touchmove test doesn't verify scroll re-enables after pointer end — packages/react/src/toast/root/ToastRoot.test.tsx:584-596
   The new test fires pointerCancel but doesn't re-dispatch a touchmove afterward to assert defaultPrevented === false. Add one more dispatch after pointerCancel to lock in the contract.

4. Brittle addEventListenerSpy reversed-find pattern — ToastViewport.test.tsx ~:492-494, :539-541
   Selecting the listener by last-registered ordering is fragile. Prefer dispatching a real window.dispatchEvent(blurEvent) or filter by the capture flag (the viewport's blur listener is the only true-capture one in these tests).

Suggestions

5. applyLimited rot risk — store.ts:69-83
   Comment asserts "Toasts are ordered newest-first" but the function trusts iteration order. Tighten to "Caller guarantees newest-first ordering (see addToast)."

6. Docs use "inert" colloquially — docs/.../page.mdx:151, types.md, ToastProvider.tsx:75
   Implementation does set the HTML inert attribute (ToastRoot.tsx:521), so consider naming it: "remain mounted with the inert attribute".

7. Missing test coverage:

   • Limit change while toasts are mid-ending (current "limit" test uses only starting toasts).
   • Timer-elapsed callback path for clearTimer (covers Finding 1).
   • Focus guard with limit > 0 and all visible toasts ending (only limit=0 covered).
   • syncProviderProps early-return reference stability.

8. Limited flag not cleared on ending toasts — store.ts:69-83
applyLimited skips ending toasts entirely, whereas the old addToast reset limited: false on every toast. Almost certainly benign (toast is on its way out), but no test pins this transition down.

Strengths

• applyLimited cleanly deduplicates three previously-divergent code paths and is reference-stable to avoid extra re-renders.
• syncProviderProps correctly uses useIsoLayoutEffect per AGENTS.md with the right dep array and an early-return for unchanged values.
• The hasActiveToasts check (replacing toasts.length === 1) genuinely fixes a corner case where ending-only toasts left hovering/focused stuck true.
• The 5 timer pausing unit tests in store.test.ts enumerate failure modes in DAMP style — each test clearly documents the bug it pins down.
• Public docs accurately reflect the new behavior (data-limited ↔ inert attribute is correctly wired up).
• F6 focus-guard skip correctly falls back to restoreFocusToPrevElement when no toast can receive focus.
• Tests follow project conventions (vitest + jest-dom only, it.skipIf used correctly, no chai/sinon).

Recommended Action

1. (Optional but cheap) Centralize the areTimersPaused reset into a single helper called from both scheduleTimer/resumeTimers inline callbacks (Finding 1).
2. Add the missing post-cancel touchmove assertion (Finding 3).
3. Decide intent on handleDocumentPointerDown/handleKeyDown resume paths (Finding 2) and either gate them or add a comment.
4. Consider the docs/comment polish (Findings 5, 6).
5. Test gaps (Finding 7) are nice-to-haves — current coverage is already strong for the fixes shipped.