How to handle "101 Switching Protocols in H2 or H3"

Howdy Folks,

The "101 Switching Protocols" upgrade mechanism is not supported in HTTP/2
or HTTP/3 according to RFC 9113:

HTTP/2 does not support the 101 (Switching Protocols) informational status
code (Section 15.2.2 of [HTTP]).


and RFC 9114:

HTTP/3 does not support the HTTP Upgrade mechanism (Section 7.8 of [HTTP])
or the 101 (Switching Protocols) informational status code (Section 15.2.2
of [HTTP]).


However, it wasn't immediately clear to me what an endpoint should do if it
receives such a response code. I'm guessing this should be considered a
stream error, but maybe there is an argument that this response code should
be propagated to the next hop. Thoughts?

Cheers,

Ryan