[alexcarpenter]

Description

Mosaic primitives now take the reading direction for keyboard navigation from React context, as Base UI does, instead of reading the nearest [dir] attribute.

• New headless DirectionProvider and useDirection() in primitives/direction-provider. direction is 'ltr' | 'rtl' and defaults to 'ltr'. useDirection() returns 'ltr' when no provider is mounted.
• MosaicProvider gets a direction prop and renders DirectionProvider from it. The prop is explicit rather than derived from localization.locale. Layout follows the page's dir, so keyboard direction should follow the value the host sets there, not the locale.
• Tabs, segmented control, OTP and tag input now use useDirection(). Tabs and segmented control used to read dir only on focus, so they now pick up a direction change while focused. readingDirectionKeys(direction) moves from tag input into the provider module so OTP can use it too.
• Nested menus now pass rtl to useListNavigation, so in RTL ArrowLeft opens a submenu and ArrowRight closes it. Before this, they always used LTR keys.
• primitives/utils/dom.ts still reads computed direction for wheel/scroll delta math, which isn't keyboard direction (Base UI also keeps computed style for scrollbar hit testing).
• Swingset's StoryMosaicProvider passes the RTL toggle's value to MosaicProvider. This is typechecked but hasn't been exercised in the browser.

This replaces #10419. The Table primitive (#10414) will switch to useDirection() once both land.

Checklist

• pnpm test runs as expected.
• pnpm build runs as expected.
• (If applicable) JSDoc comments have been added or updated for any package exports
• (If applicable) Documentation has been updated

Type of change

• 🐛 Bug fix
• 🌟 New feature
• 🔨 Breaking change
• 📖 Refactoring / dependency upgrade / documentation
• other:

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Project	Deployment	Actions	Updated
clerk-js-sandbox	Ready	Preview	Oct 25, 2026 11:49pm UTC
swingset	Ready	Preview	Oct 25, 2026 11:49pm UTC

[changeset-bot]

🦋 Changeset detected

Latest commit: f5f5dde

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@clerk/mosaic	Patch
@clerk/swingset	Patch

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commit: f5f5dde