So you were writing your application as a fcgi-app, and (e.g.) Apache was bungling Auth headers? Can you expand on this? Curious about the technical detail of (I guess) PARAM records not actually giving you what you expect?
I just remember the auth headers never showing up in the $_SERVER global (it was a PHP app). This was what I was told was the issue. They made it sound like it was well-known.
[1]: https://httpd.apache.org/docs/2.4/en/mod/core.html#cgipassau...