diff --git a/README.md b/README.md
index 6c7cef1..d5a6f36 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,9 @@ Nim implementation of the e2e reliability protocol.
 ## Quick start
 
 ```bash
+# Initialize vendored dependencies (run once after clone)
+nix run '.#setup'
+
 # Build the shared library
 nix build '.?submodules=1#libsds'
 
diff --git a/flake.nix b/flake.nix
index b2a930b..e090e5c 100644
--- a/flake.nix
+++ b/flake.nix
@@ -71,8 +71,17 @@
         default = pkgsFor.${system}.callPackage ./nix/shell.nix {};
       });
 
-      # nix run '.#clean' — garbage-collect the Nix store
       apps = forAllSystems (system: {
+        # nix run '.#setup' — initialize git submodules (run once after clone)
+        setup = {
+          type = "app";
+          program = toString (pkgsFor.${system}.writeShellScript "nix-setup" ''
+            echo "Initializing git submodules..."
+            git submodule update --init --recursive
+            echo "Done. You can now run: nix build '.?submodules=1#libsds'"
+          '');
+        };
+        # nix run '.#clean' — garbage-collect the Nix store
         clean = {
           type = "app";
           program = toString (pkgsFor.${system}.writeShellScript "nix-clean" ''