Who contributed to Meta on August 15, 2026?

5 developers shipped this update, including acdlite, Alex Hunt, Nycollas, SimenB, and MahinAnowar.

What were the notable Meta updates?

[flags] Enable enableParallelTransitions, Add idle frame support to Performance timeline (#57952), and Promote fuseboxFrameRecordingEnabled to canary (#57953).

REACT FLIPS PARALLEL TRANSITIONS BY DEFAULT, JEST FIXES ESM NAMESPACE COLLISIONS

By RepoJournal · Filed 06:59 UTC on August 15, 2026 · About Meta

5 people shipped this

SimenB @SimenB 3 cited

Alex Hunt @huntie 2 cited

acdlite @acdlite 1 cited

Nycollas @nduaarte 1 cited

MahinAnowar @MahinAnowar 1 cited

Parallel transitions move from experimental to standard across React and React Native, while Jest patches critical bugs in module resolution and test serialization.

React shipped the enableParallelTransitions flag enabled by default in OSS and canary builds [1], reversing an earlier experimental gate and rolling out to all forks except Meta's www infrastructure, which remains gated. This unlocks non-blocking state updates across the stack. Over in React Native, the team added idle frame spans to the Performance timeline to capture vsync gaps in DevTools [2], with frame recording promoted to canary [3], while also fixing a critical Hermes bytecode version mismatch in SwiftPM Release builds that was crashing apps on launch [4]. Jest landed three high-impact fixes: a namespace collision where `import * as a from 'fs'` and `import * as b from 'node:fs'` were treated as separate modules instead of one unified namespace [5], resolution of the `module-sync` export condition so packages exposing ESM-loadable-via-require entries now resolve correctly [7], and BigInt serialization in test titles [6]. Pretty-format also addressed a supply chain risk by moving react-is aliases into the @jest scope after unrelated npm accounts claimed the old alias names [8].

Action items

→ Test parallel transitions in dev builds and plan rollout to production facebook/react [plan]
→ Update Jest if you use `module-sync` export conditions or BigInt in test parameters facebook/jest [plan]
→ Apply Hermes SwiftPM fix immediately if building React Native with Release configuration facebook/react-native [immediate]
→ Monitor idle frame spans in DevTools for performance regressions facebook/react-native [monitor]

References

[1] [flags] Enable enableParallelTransitions ↗ facebook/react
[2] Add idle frame support to Performance timeline (#57952) facebook/react-native
[3] Promote fuseboxFrameRecordingEnabled to canary (#57953) facebook/react-native
[4] Fix Hermes bytecode version mismatch in SwiftPM Release builds (#57928) facebook/react-native
[5] fix(jest-runtime): give `fs` and `node:fs` one ESM namespace ↗ facebook/jest
[6] fix(jest-each): serialize bigint values in `%j` titles ↗ facebook/jest
[7] feat(jest-runtime): resolve the `module-sync` export condition ↗ facebook/jest
[8] fix(pretty-format): move the react-is aliases into the `@jest` scope ↗ facebook/jest

Quick answers

What shipped in Meta on August 15, 2026?: Parallel transitions move from experimental to standard across React and React Native, while Jest patches critical bugs in module resolution and test serialization. In total, 9 commits and 7 pull requests landed.
Who contributed to Meta on August 15, 2026?: 5 developers shipped this update, including acdlite, Alex Hunt, Nycollas, SimenB, and MahinAnowar.
What were the notable Meta updates?: [flags] Enable enableParallelTransitions, Add idle frame support to Performance timeline (#57952), and Promote fuseboxFrameRecordingEnabled to canary (#57953).

JEST FIXES ES MODULE RESOLVER LOADING

Jest can now load custom resolvers written as ES modules, closing a gap that forced developers back to CommonJS workarounds.

javascript 2 shipped

Meta Aug 14

REACT FIXES EVENT LISTENER BUG, JEST PATCHES CACHE CORRUPTION

React shipped a critical fix for `{once: true}` event listeners that were firing multiple times on Fragment children, while Jest plugged two separate cache and source map bugs that corrupted test output.

javascript 26 shipped

Meta Aug 13

REACT FIXES EVENT LISTENER LEAK, JEST DITCHES SOURCE-MAP-SUPPORT

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javascript 18 shipped

Meta Aug 12

REACT FRAGMENT FIXES LAND ACROSS THE STACK

jackpope shipped four critical Fragment corrections to React that fix event dispatch, document positioning, and nested traversal bugs that would break production apps using createRoot(document).

javascript 33 shipped

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