Accept header modified/removed in request to service container

[michaelcaterisano]

Discussed in #11369

^{Originally posted by michaelcaterisano January 13, 2025}
I have a github action using the ubuntu-latest runner which runs an Apollo Router service container exposed on localhost:4001. I have a step that runs tests, which send http requests to Router at localhost:4001. The requests are making it, but Router is returning an error saying the Accept header has the incorrect value. I'm confident that the value is correct (I've tested it against a local instance of Router using the same image), and that other headers are making it to Router, because it returns different errors when I change other header values.

Is it possible that something related to the ubuntu-latest runner is modifying or removing the Accept header? Or perhaps docker's bridge network layer?