- The default GHC version has been updated from 9.6 to 9.8.
`haskellPackages` also uses Stackage LTS 23 (instead of LTS 22) as a baseline.
We aim to remove the old GHC versions 8.10, 9.0 and 9.2 in the next release in accordance with [the new GHC deprecation policy](https://discourse.nixos.org/t/nixpkgs-ghc-deprecation-policy-user-feedback-necessary/64153).
- LLVM has been updated from LLVM 16 (on Darwin) and LLVM 18 (on other platforms) to LLVM 19.
This introduces some backwards‐incompatible changes; see the [upstream release notes](https://releases.llvm.org/) for details.