sveltejs/kit@2.43.3 throws on formSubmit

What is affected?

Component, Accessibility

Description

The following svelte/kit code

<form method="get" action="/api">
  <md-filled-button type="submit">Submit</md-filled-button>
</form>

throws an error: Uncaught TypeError: Failed to construct 'FormData': The specified element is not a submit button.

This diff is "responsible", the issue is that the controller/formSubmitter adds the md-button as the submitter

Reproduction

<form method="get" action="/api">
  <md-filled-button type="submit">Submit</md-filled-button>
</form>

StackBlitz

Workaround

<md-filled-button type="submit" onclick="{(e) => { e.preventDefault(); e.target.form.requestSubmit(); }}">Submit</md-filled-button>

Is this a regression?

No or unsure. This never worked, or I haven't tried before.

Affected versions

2.4.0

Browser/OS/Node environment

Browser: Firefox/143.0
Os: Widows 11
Node version: v22.13.1
Npm version: 10.9.2

should be a general issue on every Browser/version

Start with the linked StackBlitz reproduction and inspect internal/controller/form-submitter.ts, especially the controller behavior identified in the report. Compare the SvelteKit formSubmit behavior with the md-filled-button submitter interaction. Done means the provided form can submit without the reported FormData TypeError in the affected browser scenarios.