React's Standalone startTransition API Enables Concurrent Scheduling Outside Components

React exports a standalone startTransition function that schedules low-priority state updates without requiring component scope or hooks. Unlike useTransition, which must be called inside a React component, the standalone API can be used in third-party stores, synchronous callbacks, and non-component modules. The key trade-off is that startTransition does not return an isPending flag, meaning loading state indicators must still be handled via useTransition inside components. Developers can combine both approaches — using startTransition in store logic and useTransition in components — to achieve concurrent scheduling across the entire application. This prevents rendering jank caused by blocking state updates in code that sits outside the React component tree.