TIL: FediBuzz sends both :authority AND Host headers in HTTP/2 requests. old nginx rejects this as "duplicate". Both are kinda wrong - HTTP/2 replaced Host with :authority, but nginx shouldn't reject matching values. Fixed by upgrading nginx to 1.29+

Devlog: FediBuzz relay returned 400 errors. Root cause: nginx 1.18 + HTTP/2 + hyper/reqwest sent duplicate Host/:authority headers. Fixed by upgrading to nginx 1.29.4 which handles HTTP/2 headers correctly (fix from Aug 2025). #fediverse #activitypub #devlog