Feature: Support React Compiler without requiring useMemo for machine factories

Context

With React 19 and React Compiler, manual memoization via useMemo and useCallback is no longer recommended - the compiler automatically optimizes re-renders. However, @xstate/react's useActor hook compares logic.config by reference, which means machines created via factory functions (like setup().createMachine()) must still be wrapped in useMemo to prevent infinite re-render loops.

The Problem

When using a factory function to create a machine with dynamic config (e.g., passing wagmi config):

// This causes an infinite loop without useMemo
function MyComponent() {
  const config = useConfig();
  const machine = createMyMachine(config); // New reference each render
  const [state] = useActor(machine); // useActor detects "new" machine → setCurrent → re-render → loop
}

The workaround requires explicit memoization:

function MyComponent() {
  const config = useConfig();
  // Must memoize to prevent infinite loop
  const machine = useMemo(() => createMyMachine(config), [config]);
  const [state] = useActor(machine);
}

This works, but conflicts with React Compiler's philosophy of automatic memoization.

Proposed Solution

Consider one of these approaches:

1. Deep equality check on machine config - Instead of reference equality on logic.config, use a deep comparison or hash of the relevant config properties.

2. Stable machine identity hook - Provide a useStableMachine or similar that handles the memoization internally based on a user-provided dependency array.

3. Document React Compiler compatibility - If this is intentional behavior, clearly document that useMemo is still required for factory-created machines even with React Compiler.

Environment

• XState v5
• @xstate/react
• React 19 with React Compiler

Related Issues

• #1101 - "Allow useMachine to accept a new machine between renders" (closed 2020)
• #913 - "Why useConstant?" (closed 2019)