Nix mode

Lem has a built-in Nix mode.

It does syntax highlighting and automatic indentation.

Since December, 2025, Nix mode got tree-sitter support and enhanced, context-aware indentation.

It has declarative indentation support using tree-sitter indent queries (indents.scm) with Helix-style @indent/@outdent captures.

Nix mode’s LSP, based on oxalica/nil, is disabled by default. You can find its default configuration in extensions/nix-mode/lsp-config.lisp.