The GHC update has finally reached the master branch and the nixos-unstable channel. Feel free to report regressions that affect you on the Nixpkgs issue tracker.
We are already accruing fixes in the subsequent haskell-updates PRs and I plan on raising regressions compared to NixOS 25.05 when ZHF for 25.11 is announced. Some leads can be found here and here.
I also want to thank everyone who contributed to this update (this list is reconstructed for the Git history, DM me if I’ve missed anyone):
- The rest of the Haskell team: @wolfgangwalther & @maralorn.
- @emily heroically backported a bunch of GHC changes so that we can keep a decent number of GHC versions around without having to maintain almost half a decade old LLVM versions.
- Marc Scholten, @maralorn, Mikka Tammi, Alexandre Esteves, @ulysses4ever, @TeofilC, @gador, @marcin-serwin and @wrvsrx contributed fixes.
- @trofi diagnosed and fixed several eval issues.
Also of course, thanks to the staging team, the Stackage maintainers and Hackage trustees.
I’m still not happy with the time it took to deliver this update. Part of this was the extra delay due to the staging workflow (we finalized our branch on 2025-09-25, staging-next was merged on 2025-10-05). I’m still not happy with the development time of 1.5-2 months, but it is a big improvement compared to the update to 9.8 which took almost 4 months. We’ve been discussing changes that could reduce both of these factors which we’ll hopefully start implementing soon.
I am (once again) disappointed by the disparity between outside contributions and the Haskell team. Seeing a disparity here is only natural, though I am concerned by the magnitude (2 people account for ~80% of the commits relating to this update). I’ve found having to fix regressions especially frustrating when the packages in question have maintainer(s) listed that had been notified for well over a month, but never so much as responded. I am entertaining a theory that this is related to our notification mechanism being prone to getting lost among irrelevant GitHub notifications, so maybe some changes are in order there.