diff --git a/AGENTS.md b/AGENTS.md
index 5a7ed1c..e57d3ed 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -58,3 +58,7 @@ This file provides guidelines for AI coding agents operating within this reposit
 ## ⚠️ Critical Warnings
 
 - **NEVER RUN `nix-env`** - This can break your Nix environment. Use `nix-shell`, `nix develop`, or declarative approaches instead.
+
+## ⚠️ Critical Warnings
+
+- **NEVER RUN `nix-env`** - This can break your Nix environment. Use `nix-shell`, `nix develop`, or declarative approaches instead.
diff --git a/Makefile b/Makefile
index 0a0fbfd..22510b6 100644
--- a/Makefile
+++ b/Makefile
@@ -59,9 +59,9 @@ flash-usb: build-usb
 	sync
 	@echo "✅ USB drive ready!"
 
-test-usb: 
+test-usb:
 	@echo "🧪 Testing USB environment in QEMU..."
-	qemu-system-x86_64 \
+	nix develop --command qemu-system-x86_64 \
 		-cdrom $(ISO_FILE) \
 		-m 2048 \
 		-enable-kvm \
diff --git a/flake.nix b/flake.nix
index 7af1443..78268df 100644
--- a/flake.nix
+++ b/flake.nix
@@ -65,6 +65,7 @@
           markdownlint-cli
           jq
           nixpkgs-fmt
+          qemu
         ];
       };