React Daily: Fixing Timing Bugs in Flight and Act
Two fixes from hamedrabah address subtle timing and ordering bugs in React internals—one in the Flight client's prop freezing, one in the test utilities' act queue—both triggered by re-entrant or out-of-order execution.
Duration: PT2M12S
Episode overview
This episode is a short developer briefing from React Daily.
It explains recent repository work in plain language.
- Show: React Daily
- Published: 2026-08-28T06:00:28Z
- Audio duration: PT2M12S
Transcript excerpt
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Good morning. It's August 28th, and today's React activity centers on one theme: getting execution order right when operations overlap.
Both pull requests today fix bugs that only surface when something happens out of sequence. In PR 37398, the Flight client was freezing an element's props before an outstanding reference had finished writing into that same object—so when the write finally landed, it hit a frozen target and threw. The fix, tied to…
PR 37397 hits a similar note in a different corner of the codebase: the test utilities' `act()` function. If `act()` gets re-entered while an outer call is still flushing, it could spin up a new queue even though the surrounding call still thinks it owns the original one. The old logic used scope depth to decide who…
The throughline here: both bugs came from code that assumed a strictly linear, non-overlapping sequence of operations, and both broke when that assumption failed—one with async reference resolution, one with nested synchronous calls. Neither is a new feature; they're hardening passes on internals that a lot of other…
What to remember: if you're debugging flaky prop-freezing errors in Flight, or tests that fail only when act…
That…
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