When trying to use Claude, I'm often getting:

"error in process sentinel: Multibyte text in HTTP request: POST /v1/messages HTTP/1.1
MIME-Version: 1.0
Connection: keep-alive
Host: api.anthropic.com
Accept-encoding: gzip
Accept: /
User-Agent: URL/Emacs Emacs/30.1 (OpenStep; aarch64-apple-darwin24.3.0)
Content-Type: application/json"

Seems that this appears every time there is a non-standard symbol like Ω, ∞, etc.
The same symbols work without problem with the openai api.

Changelog seems to suggest that in the past the same error was also present with the openai api, but got fixed by you since then.