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The Wire · Showcase

JEST FIXES CJS-FROM-ESM INTEROP, REACT NATIVE STABILIZES VIRTUALIZEDLIST

By RepoJournal · Filed · About Meta

Jest shipped three critical fixes for CommonJS-to-ESM module interop that align behavior with Node.js, while React Native re-enabled a flaky VirtualizedList test and fixed out-of-order events on Android Fabric.

Jest's runtime layer was leaking `__esModule` unwrapping into CJS imports of ESM modules, breaking interop expectations [1]. The team also fixed function module.exports handling for named exports [2] and added long-overdue support for custom runner configuration via tuple format [7]—reporters got this years ago, runners finally caught up. On the React Native side, VirtualizedList's "retains batch render region" test was unstable under React 19's timer semantics and now passes reliably [3]. Android Fabric developers will want the out-of-order event fix [4], which addresses buffering behavior when EventEmitterWrapper hasn't mounted yet. The 0.86.0-rc.0 changelog is live [5] and Hermes bumped to 250829098.0.13 [6], bringing the latest compiler optimizations.

Action items

References

  1. [1] fix(jest-runtime): align CJS-from-ESM default with Node, drop `__esModule` unwrapping ↗ facebook/jest
  2. [2] fix(jest-runtime): handle function module.exports for CJS-from-ESM named exports ↗ facebook/jest
  3. [3] Re-enabled VirtualizedList "retains batch render region when an item is appended" test (#56653) facebook/react-native
  4. [4] Fix Fabric out-of-order event delivery on Android facebook/react-native
  5. [5] Add changelog for v0.86.0-rc.0 (#56711) facebook/react-native
  6. [6] Bump Hermes V1 to latest stable 250829098.0.13 (#56728) facebook/react-native
  7. [7] feat: allow custom runner configuration options (tuple format) ↗ facebook/jest

FAQ

What changed in Meta on May 9, 2026?
Jest shipped three critical fixes for CommonJS-to-ESM module interop that align behavior with Node.js, while React Native re-enabled a flaky VirtualizedList test and fixed out-of-order events on Android Fabric.
What should Meta teams do about it?
Review Jest CJS-from-ESM fixes before upgrading to next release • Test React Native 0.86.0-rc.0 for VirtualizedList stability in your apps • If using Fabric on Android with buffered events, backport event delivery fix
Which Meta repositories shipped on May 9, 2026?
facebook/jest, facebook/react-native

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