useTransition pending state synchronization during interrupted renders

Concurrent Rendering State Management

React 18 introduces the useTransition hook to mark state updates as non-urgent, allowing the UI to remain responsive while a new version of the tree is prepared in memory. This mechanism relies on the isPending flag to signal to the user that a transition is occurring.

Interruptibility and State Consistency

In scenarios where a high-priority event (such as a keystroke) interrupts a long-running transition render, React may discard the interrupted render and start over. There is uncertainty regarding the exact timing of the isPending state transition when multiple concurrent updates are queued or interrupted rapidly.

• How does React handle the isPending boolean when a transition is interrupted by a higher-priority update before the initial render completes?
• Does the pending state persist across the interruption, or is it reset and re-triggered for the subsequent render attempt?