[Connect-TCP WGLC] When is it okay to use Proxy-Status?

[ekinnear]

We say:

Proxies implementing this specification SHOULD include a "Proxy-Status" response header field [RFC9209] in any success or failure response (i.e., status codes 101, 2XX, 4XX, or 5XX) to support advanced client behaviors and diagnostics. Clients and proxies MUST NOT send trailer fields on "connect-tcp" streams.

Just out of curiosity, what about 100 Continue? Or 3xx responses?

[bemasc]

RFC 9209 doesn't address the applicability of Proxy-Status to 100 or 3xx responses, so I'm inclined to remain silent on that question here as well.

In my personal view:

• 3xx means "this endpoint isn't your proxy", so Proxy-Status is not applicable
• 100 means "all good but proxying hasn't started yet", so there's nothing to say about proxying yet.