Release 3.21.5 (2026-07-08)

• Based on upstream Nix 2.34.8.

Binary cache performance improvements

This release includes a number of async rewrites from upstream Nix that make querying missing paths much faster. PR: DeterminateSystems/nix-src#514

Remote store performance improvements

Registering temporary roots on remote stores (e.g. when doing nix copy to a remote store over ssh-ng) is now much faster. PR: DeterminateSystems/nix-src#538

Computing closures (e.g. nix-store -qR) is now much faster on high-latency ssh-ng stores. PR: DeterminateSystems/nix-src#539

Parallel evaluation performance improvements

This release delivers a number of performance improvements to parallel evaluation.

PRs: DeterminateSystems/nix-src#531, DeterminateSystems/nix-src#535, DeterminateSystems/nix-src#536, DeterminateSystems/nix-src#537, DeterminateSystems/nix-src#546

Miscellaneous improvements

• nix search now prints the total number of derivations, in addition to the number of matching derivations. PR: DeterminateSystems/nix-src#532

Bug fixes and other changes

• Allow local networking in libmicrohttpd and functional tests by @lilyinstarlight in DeterminateSystems/nix-src#518
• Don't ignore substitution failures for BasicDerivation inputSrcs by @edolstra in DeterminateSystems/nix-src#520
• Sync with upstream 2.34-maintenance by @edolstra in DeterminateSystems/nix-src#521
• fixup: make binary cache nuclear option more general by @cole-h in DeterminateSystems/nix-src#524
• NarInfoDiskCache: Support arbitrary nix-cache-info fields by @edolstra in DeterminateSystems/nix-src#525
• ci: update DSP on releases by @cole-h in DeterminateSystems/nix-src#526
• Add some calls to addTempRoot() by @edolstra in DeterminateSystems/nix-src#527
• flake.lock: Update by @edolstra in DeterminateSystems/nix-src#529

New Contributors

• @lilyinstarlight made their first contribution in DeterminateSystems/nix-src#518

Full Changelog: v3.21.2...v3.21.5