Release 3.11.0 (2025-09-03)

What's Changed

Parallel evaluation

The following commands are now able to evaluate Nix expressions in parallel:

  • nix search
  • nix flake check
  • nix flake show
  • nix eval --json

This is currently in developer preview, and we'll be turning it on for more users in the coming weeks. If you would like to try it right away, specify eval-cores in your /etc/nix/nix.custom.conf:

eval-cores = 0 # Evaluate across all cores

Further, we introduced a new builtin: builtins.parallel. This new builtin allows users to explicitly parallelize evaluation within a Nix expression.

Using this new builtin requires turning on an additional experimental feature:

extra-experimental-features = parallel-eval

Please note that this new builtin is subject to change semantics or even go away during the developer preview.

PR: DeterminateSystems/nix-src#125

Full Changelog: v3.10.1...v3.11.0