diff --git a/users/crumb/programs/emacs/init.el b/users/crumb/programs/emacs/init.el
index 40403e4..7645798 100755
--- a/users/crumb/programs/emacs/init.el
+++ b/users/crumb/programs/emacs/init.el
@@ -61,4 +61,5 @@
 (require 'syd-scratch)
 (require 'syd-smartparens)
 (require 'syd-tramp)
+(require 'syd-tooling)
 (require 'syd-ui)
diff --git a/users/crumb/programs/emacs/lib/syd-prelude.el b/users/crumb/programs/emacs/lib/syd-prelude.el
index 8b4cd81..ff7e997 100644
--- a/users/crumb/programs/emacs/lib/syd-prelude.el
+++ b/users/crumb/programs/emacs/lib/syd-prelude.el
@@ -4,6 +4,10 @@
 
 (require 'syd-constants)
 
+(use-package dash)
+
+(require 'dash)
+
 (cl-defmacro syd-define-stub
     (name &key (desc "implement me!") interactive)
   (let ((todo (format "%s: TODO: %s" name desc)))
@@ -130,4 +134,35 @@ form."
            (prog1 (progn ,@body)
              (message ""))))))
 
+(defun syd--parse-defadvice-args (arg-list)
+  "Parses the docstring and keywords provided to `syd-defadvice'."
+  (let (docstring
+        advice)
+    (when (stringp (car-safe arg-list))
+      (setq docstring (pop arg-list)))
+    (while (and (length> arg-list 2)
+                (keywordp (car arg-list)))
+      (let ((how (pop arg-list))
+            (sym (pop arg-list)))
+        (push (cons how sym) advice)))
+    ;; What's left of `arg-list' is the body of the defun.
+    (list docstring advice arg-list)))
+
+(defmacro syd-defadvice (name params &rest args)
+  "Define a function and add it as advice."
+  (declare (indent defun))
+  (-let (((docstring advice body) (syd--parse-defadvice-args args)))
+    `(progn (defun ,name ,params
+              ,@(-some-> docstring list)
+              ,@body)
+            ,@(-map (lambda (arg)
+                      (-let (((how . sym) arg))
+                        `(advice-add ,sym ,how #',name)))
+                    advice))))
+
+(syd-defadvice syd-lsp-install-server-a ()
+  :override #'lsp-install-server
+  (user-error (concat "Ignoring a call to `lsp-install-server'"
+                      " — tell the caller to use Nix!")))
+
 (provide 'syd-prelude)
diff --git a/users/crumb/programs/emacs/modules/lang/syd-lang-nix.el b/users/crumb/programs/emacs/modules/lang/syd-lang-nix.el
new file mode 100644
index 0000000..ea4763d
--- /dev/null
+++ b/users/crumb/programs/emacs/modules/lang/syd-lang-nix.el
@@ -0,0 +1,8 @@
+;;; syd-lang-nix.el -*- lexical-binding: t; -*-
+
+(use-package nix-mode
+  :mode "\\.nix\\'"
+  :config
+  (add-hook 'nix-mode-hook #'lsp))
+
+(provide 'syd-lang-nix)
diff --git a/users/crumb/programs/emacs/modules/syd-lang.el b/users/crumb/programs/emacs/modules/syd-lang.el
index 0bcf987..0b30dac 100644
--- a/users/crumb/programs/emacs/modules/syd-lang.el
+++ b/users/crumb/programs/emacs/modules/syd-lang.el
@@ -2,5 +2,6 @@
              (file-name-concat user-emacs-directory "modules" "lang"))
 
 (require 'syd-lang-emacs-lisp)
+(require 'syd-lang-nix)
 
 (provide 'syd-lang)
diff --git a/users/crumb/programs/emacs/modules/syd-tooling.el b/users/crumb/programs/emacs/modules/syd-tooling.el
new file mode 100644
index 0000000..fa7fda9
--- /dev/null
+++ b/users/crumb/programs/emacs/modules/syd-tooling.el
@@ -0,0 +1,30 @@
+;;; syd-tooling.el -*- lexical-binding: t; -*-
+
+(use-package lsp-mode
+  :init
+  ;; We'll bind things ourselves.
+  (setq lsp-keymap-prefix nil)
+  ;; Keep state out of my config dir.
+  (setq lsp-session-file (file-name-concat syd-data-dir "lsp-session")
+        ;; We disable `lsp-install-server', but I don't want this to be nil.
+        lsp-server-install-dir (file-name-concat syd-data-dir "lsp"))
+  ;; Disable features that have great potential to be slow.  LSPs tend to be
+  ;; quite slow compared to non-LSP equivalents.
+  (setq lsp-enable-folding nil
+        lsp-enable-text-document-color nil)
+  ;; Reduce unexpected modifications to code
+  (setq lsp-enable-on-type-formatting nil)
+  ;; Make breadcrumbs opt-in; they're redundant with the modeline and imenu
+  (setq lsp-headerline-breadcrumb-enable nil)
+  :hook (lsp-mode . lsp-enable-which-key-integration)
+  :commands lsp
+  :config
+  (syd-defadvice syd-lsp-install-server-a ()
+    "Override and disbale `lsp-install-server'"
+    :override #'lsp-install-server
+    (user-error (concat "Ignoring a call to `lsp-install-server'"
+                        " — tell the caller to use Nix!")))
+  (set-popup-rule! (rx line-start "*lsp-" (or "help" "install"))
+    :size 0.35 :quit t :select nil))
+
+(provide 'syd-tooling)