feat(ButtonGroup): remove support for sx

[joshblack]

Closes #6761

Changelog

New

Changed

Removed

• Remove support for sx from ButtonGroup

Rollout strategy

• Major release; if selected, include a written rollout or migration plan

This component has no sx usage in github-ui and can be safely merged in ✅

[changeset-bot]

🦋 Changeset detected

Latest commit: 844f8b5

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

This PR includes changesets to release 2 packages

Name	Type
@primer/react	Major
@primer/styled-react	Major

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[Copilot]

Pull Request Overview

This PR removes the deprecated sx prop from the ButtonGroup component as part of the ongoing migration away from the styled-components system to CSS modules. The change includes updating the component's TypeScript interface, replacing the internal BoxWithFallback wrapper with a polymorphic base component, and migrating existing sx usage in stories to standard CSS properties.

Key changes:

• Removes sx prop support from ButtonGroup component interface
• Replaces BoxWithFallback with polymorphic component pattern using as prop
• Updates development stories to use inline styles instead of sx prop

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
packages/react/src/ButtonGroup/ButtonGroup.tsx	Removes sx prop, replaces BoxWithFallback with polymorphic component pattern
packages/react/src/ButtonGroup/ButtonGroup.docs.json	Removes deprecated sx prop from component documentation
packages/react/src/ButtonGroup/ButtonGroup.dev.stories.tsx	Migrates sx usage to inline styles and removes SxProp story
.changeset/light-colts-burn.md	Adds changeset entry for major version bump

[Copilot]

The as prop is destructured but not included in the ButtonGroupProps type definition. This creates a mismatch between the component's actual interface and its declared props type, which could confuse consumers and break TypeScript IntelliSense.

[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github depends on. If you are GitHub staff, we recommend testing these changes with github/github using the integration workflow. Thanks!

[github-actions]

size-limit report 📦

Path	Size
packages/react/dist/browser.esm.js	88.55 KB (-0.11% 🔽)
packages/react/dist/browser.umd.js	88.76 KB (+0.04% 🔺)

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/2668

[primer-integration]

🟢 ci completed with status success.

[github-actions]

👋 Hi, there are new commits since the last successful integration test. We recommend running the integration workflow once more, unless you are sure the new changes do not affect github/github. Thanks!