Which of the changes in https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/oauthclient-php/+log/refs/heads/master since v2.2.0 has fixed the warnings you're getting? Can you give an example of the warnings?

PHP 8.4 now does this complaint in 2.2.0 version, which is now fixed in master/main:
Deprecated: MediaWiki\OAuthClient\Client::__construct(): Implicitly marking parameter $logger as nullable is deprecated, the explicit nullable type must be used instead in .../vendor/mediawiki/oauthclient/src/Client.php on line 77

Deprecated: MediaWiki\OAuthClient\Client::makeOAuthCall(): Implicitly marking parameter $postFields as nullable is deprecated, the explicit nullable type must be used .../vendor/mediawiki/oauthclient/src/Client.php on line 246

Deprecated: MediaWiki\OAuthClient\Client::makeCurlCall(): Implicitly marking parameter $postFields as nullable is deprecated, the explicit nullable type must be used .../vendor/mediawiki/oauthclient/src/Client.php on line 302

I guess those were fixed by rMOAC93cf9e642fb1: build: Updating mediawiki/mediawiki-codesniffer to 45.0.0 which phpcbf'd some parameter declarations.

Yeah. I just need a new version number. I really dislike having composer ask for "the latest and greatest, good luck"

Change #1167208 had a related patch set uploaded (by D3r1ck01; author: Derick Alangi):

[mediawiki/oauthclient-php@master] Prepare to tag version 3.0.0

https://gerrit.wikimedia.org/r/1167208

Change #1167208 merged by jenkins-bot:

[mediawiki/oauthclient-php@master] Prepare to tag version 2.3.0

https://gerrit.wikimedia.org/r/1167208

Thank you @Tgr for reviewing. The 2.3.0 tag has been pushed. @AManWithNoPlan, let us know if the new tag resolves the issue(s) you reported. Thanks!

That fixed the errors/warnings.