TLDR Tech / DevOps
How we found a bug in the hyper HTTP library
Cloudflare engineers spent six weeks tracking down a race condition in the hyper HTTP library that caused intermittent failures when processing larger images through their Workers Images binding, ultimately fixing it with just four lines of code that ensured the connection buffer fully flushed before shutdown. The bug, which silently truncated responses (returning only ~200 KB of an expected 3.3 MB image with a 200 status), only surfaced after a December 2025 architecture change that replaced their FL intermediary with faster Unix sockets, inadvertently exposing a timing issue where hyper would discard flush status checks and prematurely shut down connections when socket buffers filled.
Read the full story