diff --git a/modules/home/emacs/default.nix b/modules/home/emacs/default.nix
index 3dea69e..7f7f561 100644
--- a/modules/home/emacs/default.nix
+++ b/modules/home/emacs/default.nix
@@ -10,7 +10,10 @@
     emacs-pgtk = pkgs.emacs-pgtk.pkgs.withPackages(epkgs: with epkgs; [
       helix
       jjdescription
+      nix-ts-mode
       treemacs
+      treesit-auto
+      treesit-grammars.with-all-grammars
       vc-jj
     ]);
   in {
diff --git a/modules/home/emacs/init.el b/modules/home/emacs/init.el
index 08b9fe4..7a98b82 100644
--- a/modules/home/emacs/init.el
+++ b/modules/home/emacs/init.el
@@ -3,6 +3,7 @@
 (add-to-list 'load-path (expand-file-name "lisp" user-emacs-directory))
 
 (require 'init-helix)
+(require 'init-treesit)
 
 (with-eval-after-load 'treemacs
   (add-hook 'treemacs-mode-hook (lambda () (helix-normal-mode -1)))
diff --git a/modules/home/emacs/lisp/init-treesit.el b/modules/home/emacs/lisp/init-treesit.el
new file mode 100644
index 0000000..b35e78e
--- /dev/null
+++ b/modules/home/emacs/lisp/init-treesit.el
@@ -0,0 +1,15 @@
+;;; init-treesit.el --- Tree-sitter-based syntax highlighting -*- lexical-binding: t; -*-
+
+;; Grammars are provided by Nix via `treesit-grammars.with-all-grammars';
+;; don't let treesit-auto try to fetch and compile them at runtime.
+(setq treesit-auto-install nil)
+
+(require 'treesit-auto)
+(global-treesit-auto-mode)
+
+;; Nix isn't a built-in tree-sitter mode, so `treesit-auto' doesn't know
+;; about it. Wire it up explicitly.
+(add-to-list 'auto-mode-alist '("\\.nix\\'" . nix-ts-mode))
+
+(provide 'init-treesit)
+;;; init-treesit.el ends here