[checkbox group] Focus invalid checkbox

[atomiks]

Fixes #5200

PR #5218 is a smaller dependent follow-up that uses the input registry introduced here.

Changes

• Focuses the checkbox whose hidden input fails validation.
• Keeps input registration and focus targeting synchronized across disabled, unmounted, portaled, and reassociated checkboxes.
• Preserves validation mode boundaries when no eligible checkbox is mounted while still running custom validation at the configured boundary.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@5216
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@5216
  

commit: 21ae3bb

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+448B(+0.10%)	🔺+184B(+0.13%)

Details of bundle changes

Performance

Total duration: 1,227.58 ms -73.38 ms^(-5.6%) | Renders: 78 ⁽⁺⁰⁾ | Paint: 1,930.48 ms -94.03 ms^(-4.6%)

Test	Duration	Renders
Combobox type — 500 items, narrows to ~11 (type "Row 25")	33.17 ms ▼-13.90 ms(-29.5%)	17 (+0)
Combobox type — 500 items, all stay mounted (type "Row ")	28.27 ms ▼-8.39 ms(-22.9%)	11 (+0)

12 tests within noise — details

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[Copilot]

Pull request overview

This pull request fixes a form-focus bug in CheckboxGroup when used inside Field.Root, ensuring that invalid submissions focus the checkbox that actually fails native constraint validation (instead of always focusing the first checkbox in the group).

Changes:

• Track registered checkbox inputs (and their corresponding control elements) so focus can target the currently-invalid checkbox within a group.
• Update CheckboxGroup’s registered field control ref to dynamically resolve to the representative (invalid-first, else first enabled) checkbox control.
• Add Chromium-only regression tests covering invalid checkbox focus, unmount/disable scenarios, and parent-checkbox exclusion.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/react/src/internals/field-root-context/FieldRootContext.ts	Extends the default field validation context with getInputControl to support dynamic focus targeting.
packages/react/src/field/root/useFieldValidation.ts	Switches registered inputs tracking to a Map and adds getInputControl() to return the representative input’s control element.
packages/react/src/checkbox/root/CheckboxRoot.tsx	Registers each checkbox input with its control ref (excluding parent checkboxes) and removes group-level control ref registration.
packages/react/src/checkbox-group/CheckboxGroupContext.ts	Removes the now-unneeded registerControlRef from context.
packages/react/src/checkbox-group/CheckboxGroup.tsx	Registers a dynamic controlRef whose .current resolves to the representative checkbox control via validation state.
packages/react/src/checkbox-group/CheckboxGroup.test.tsx	Adds Chromium-only tests that reproduce and prevent regressions for focus targeting and representative updates.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.