git bisect works remarkably well on monorepos like Nixpkgs, where a commit hash lets you build software exactly as it was at a given point in time with complete dependencies. I bisected[0] 15K commits overnight to pinpoint when exactly a Haskell package failed, and sure enough the culprit was a glibc update from 2.31 to 2.32.

[0] https://github.com/NixOS/nixpkgs/issues/107358