[Tracking]: Babel 8 support

[Sidnioulz]

Problem statement

There has been a major update of Babel, with breaking changes across multiple API endpoints we use.

Most of the ecosystem is not yet compatible with Babel 8, and so we must navigate version conflicts on top of breaking changes.

Milestones

M1: version compatibility in Webpack sandboxes

Owner: @Sidnioulz
Complete by: 2026-06-26

• Ensure our sandboxes work with Babel 7 and 8
• Fix up bugfixes config injection when Babel 8 is detected
• Provide escape hatch for users when Babel version detection fails to avoid injecting bugfixes

M2: nextjs-webpack framework usage of Babel

Our nextjs framework uses a lot of Babel packages as direct dependencies.

Owner: ???
Complete by: @date

• Switch the framework to Babel 8 at some point when it is widely adopted
• OR - prebundle Babel so we don't cause version conflicts
• OR - find a way to support both versions (lots of code to change if we do this)

M3: react-docgen

react-docgen fails to compile args if we force it to resolve Babel to v8 (which we need in sandboxes for Babel 8 to work).

Owner: ???
Complete by: @date

• Wait for react-docgen to support Babel 8 before we can claim Babel 8 support

[Stanzilla]

I hit the react-docgen blocker from this tracker while testing a Babel 8 override and opened reactjs/react-docgen#1103. It fixes the synchronous loadPartialConfig call plus default parser plugins removed in Babel 8, with regression coverage for the public parse() API while retaining Babel 7 defaults.