diff --git a/dynamic.nix b/dynamic.nix
index 5d2728c..a8b00f2 100644
--- a/dynamic.nix
+++ b/dynamic.nix
@@ -135,7 +135,24 @@ pkgs.mkShell {
       )
       ++ attrValues haskell-tools
       ++ optionals withGHCTooling (
-        with pkgs; [ python3 automake autoconf alex happy git libffi.dev ]
+        # `pkgs.alex` and `pkgs.happy` from nixpkgs are built with a different
+        # GHC than the shell's `compiler` (currently ghc-9.10.3 in nixpkgs
+        # haskellPackages), and their library outputs anchor that foreign GHC
+        # in the closure (~2.15 GB on Darwin). Use haskell.nix's `tool` builder
+        # — same pattern as cross-js.nix and cross-windows.nix — to build them
+        # with the shell's `compiler-nix-name`, so library outputs reference
+        # the GHC that's already in the closure rather than dragging in a
+        # second one. `gitMinimal` swaps out heavyweight git (saves ~150 MB
+        # of perl-modules + git-doc that aren't used inside the shell).
+        with pkgs; [
+          python3
+          automake
+          autoconf
+          (tool "alex")
+          (tool "happy")
+          gitMinimal
+          libffi.dev
+        ]
       )
     ;
 
diff --git a/tool-map.nix b/tool-map.nix
index 1a3a152..14fe6c7 100644
--- a/tool-map.nix
+++ b/tool-map.nix
@@ -43,8 +43,11 @@ compiler-nix-name: tool: {
       cabalProject = __readFile (src + "/cabal.project");
       configureArgs = "--disable-benchmarks --disable-tests";
   };
-  happy = { version = "1.20.1.1"; inherit cabalProjectLocal; };
-  alex = { version = "3.2.7.3"; inherit cabalProjectLocal; };
+  # happy/alex don't need head.hackage (they're standard mainline packages and
+  # build cleanly from regular hackage). Dropping `inherit cabalProjectLocal`
+  # also avoids depending on the head.hackage SHA pin going stale.
+  happy = { version = "2.1.7"; };
+  alex = { version = "3.5.4.0"; };
   cabal = rec {
     src = self.inputs.cabal;
     # We use the cabal.boostrap.project file, as we don't