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The Wire · Showcase

JEST ADDS ESM CONFIG SUPPORT, REACT NATIVE PATCHES SCHEDULER MEMORY CORRUPTION

By RepoJournal · Filed · About Meta

Jest now accepts jest.config.mts for ESM-first TypeScript projects [ref:5], while React Native ships critical fixes for a delegate teardown race condition that could crash bridgeless apps [ref:1].

The Jest team resolved a friction point for ESM workflows by adding support for the .mts TypeScript ESM extension in configuration files [3]. This closes a gap where .mts projects were forced to use .ts or .js configs, losing explicit ESM signaling independent of package.json. Over on React Native, two complementary patches landed to address a memory safety issue in the Scheduler: one introduces a defensive feature flag [2] while the other defers lambda execution to prevent use-after-free when the SchedulerDelegate is torn down between enqueue and execution [1]. This is particularly critical for bridgeless implementations where RuntimeScheduler_Modern runs lambdas asynchronously. React Native also added synchronous mount props override test coverage [4] to shore up Android behavior. Dependency updates are rolling through Jest's test infrastructure, including @eslint/markdown 8.0 [5] and eslint-plugin-jsdoc 62.0 [6], along with a documentation fix for v30 migration guidance [7].

Action items

References

  1. [1] Guard Scheduler deferred lambdas against delegate teardown (#56680) facebook/react-native
  2. [2] Add enableSchedulerDelegateInvalidation feature flag (#56678) facebook/react-native
  3. [3] Support jest.config.mts ↗ facebook/jest
  4. [4] Add test for synchronous mount props override behavior (#56663) facebook/react-native
  5. [5] chore(deps): update dependency @eslint/markdown to v8 ↗ facebook/jest
  6. [6] chore(deps): update dependency eslint-plugin-jsdoc to v62 ↗ facebook/jest
  7. [7] Fix link in v30 migration documentation (#16021) facebook/jest

FAQ

What changed in Meta on May 5, 2026?
Jest now accepts jest.config.mts for ESM-first TypeScript projects , while React Native ships critical fixes for a delegate teardown race condition that could crash bridgeless apps .
What should Meta teams do about it?
Apply React Native Scheduler fixes [ref:1][ref:2] to bridgeless implementations before next release • Upgrade Jest to next version with jest.config.mts support [ref:5] if using ESM-first TypeScript • Review eslint-plugin-jsdoc 62.0 breaking changes [ref:7] before updating CI
Which Meta repositories shipped on May 5, 2026?
facebook/react-native, facebook/jest

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