[checkbox] Ignore focus while disabled

[atomiks]

Disabled Checkbox could still set focused field state when focus was moved to it programmatically.

Root cause

Checkbox handled focus without checking disabled, unlike the related Switch and Radio controls.

Changes

• Guarded Checkbox focus state updates while disabled.
• Added coverage for disabled Checkbox not setting data-focused.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@4998
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@4998
  

commit: ae06ac7

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+3B(0.00%)	🔺+3B(0.00%)

Details of bundle changes

Performance

Total duration: 1,315.51 ms +91.43 ms^(+7.5%) | Renders: 50 ⁽⁺⁰⁾ | Paint: 1,983.26 ms +155.27 ms^(+8.5%)

Test	Duration	Renders
Dialog mount (300 instances)	65.88 ms 🔺+17.19 ms(+35.3%)	1 (+0)
Popover mount (300 instances)	79.89 ms 🔺+13.87 ms(+21.0%)	1 (+0)

10 tests within noise — details

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[atomiks]

Code Review (GPT-5.5)

Approve ✅ This is a narrow bug fix that correctly blocks disabled Checkbox focus state without expanding the component’s behavior surface.

1. Bugs / Issues (None)

I didn’t find any blocking or non-blocking issues in the branch diff.

2. Root Cause & Patch Assessment

The fix addresses the root cause directly: Checkbox.Root previously set Field focus state on every root focus event, even when the checkbox was disabled. Guarding setFocused(true) behind !disabled matches the existing Switch pattern and prevents disabled controls from exposing data-focused through Field state after programmatic focus.

3. Test Coverage Assessment

The added regression test covers the reported disabled-focus case at the component/state-attribute level. I also ran:

pnpm test:jsdom CheckboxRoot --no-watch
pnpm test:chromium CheckboxRoot --no-watch
git diff --check upstream/master...HEAD

All passed. GitHub status checks for the PR head are green as well.