This is more of a question than a request to implement a feature.

How possible is it to send a 103 response with a Link header before sending the main response back to the browser?

From what I understand once a response sends something the state of that response is “sent”.

Motivation

HTTP/2 Server Push has been killed off and removed from Chrome. https://groups.google.com/a/chromium.org/g/blink-dev/c/K3rYLvmQUBY/m/vOWBKZGoAQAJ

The focus instead is on Early Hints, which allows the server to send a preliminary response back to the browser which has a Link header followed by what resources the browser can download while it waits. Then followed by the final response.

This isn’t supported fully in browsers yet but there’s experiments happening to see if it’s worth pursuing.

Is this something frameworks can implement or does there need to be changes at Node level?

Spec:
https://httpwg.org/specs/rfc8297.html

https://chromium.googlesource.com/chromium/src/+/master/docs/early-hints.md

https://www.fastly.com/blog/beyond-server-push-experimenting-with-the-103-early-hints-status-code