Widget for a number field get a string as value

[sthenault]

Prerequisites

• I have searched the existing issues
• I understand that providing a SSCCE example is tremendously useful to the maintainers.
• I have read the documentation
• Ideally, I'm providing a sample JSFiddle, Codesandbox.io or preferably a shared playground link demonstrating the issue.

What theme are you using?

mui

Version

6.8

Current Behavior

We've a custom widget for a number field which breaks since 6.8 because its value prop is given as a string instead of a number as it was up to 6.7.

It appears this occurs on browser with eg. french locale setup (actually language with decimal separator != '.')

Expected Behavior

get value as a number as before.

Steps To Reproduce

• define a custom widget for some number field
• setup your browser's locale to "french"
• check the type of the value prop given to your widget

Environment

- OS: debian trixie
- Node: 24.20
- npm: 11.19

Anything else?

No response

[nickgros]

Proposed fix in #5243