What version of this package are you using?
2.6.2

What operating system, Node.js, and npm version?
MacOS Sonoma
node 20.11.0
npm 10.2.4
next 14.2.7

What happened?
Format function does not exist in the AppDirI18nProvider client-side (under config.interpolation.format), so no formatting occurs for client components. A hydration error also occurs because the formatter function exists and works when component is first server rendered, but then does not work when client rendered - which is the end result.

My specific example is a date formatter as seen in the screenshot below:

When checking the AppDirI18nProvider in the dev console:

What did you expect to happen?
When using App Router, the interpolation.format function exists in the AppDirI18nProvider in the browser and format function works for client components.

The format function already exists when using page router (as seen in image below). We want the same function for app router.