Steps to reproduce

Steps:

1. Open this link to live example: https://codesandbox.io/p/sandbox/pedantic-germain-nc325h
2. Click the Native Button - this triggers the expected Alert
3. Click the MUI Button - this has the same "formAction" as the Native button, but does not trigger the expected alert

Current behavior

The formAction property on a Button is being treated as a string prop.

Expected behavior

The formAction property should support an action using a (formData: FormData): void signature

Context

Use React 19 Form Actions

Your environment

  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.

Search keywords: formAction does not support React 19 FormData methods