diff --git a/nix/scripts/build-root.sh b/nix/scripts/build-root.sh
index 0a8240e..2fba0a7 100644
--- a/nix/scripts/build-root.sh
+++ b/nix/scripts/build-root.sh
@@ -73,6 +73,14 @@ openclaw_cleanup_output_build_root() {
   openclaw_cleanup_output_pnpm_store
 
   case "$build_root" in
-    "$out"/*) rm -rf "$build_root" ;;
+    "$out"/*)
+      if [ -n "${NIX_BUILD_TOP:-}" ] && [ -d "$NIX_BUILD_TOP" ]; then
+        discard="$NIX_BUILD_TOP/.openclaw-build-root-discard-$$"
+        if mv "$build_root" "$discard" 2>/dev/null; then
+          return 0
+        fi
+      fi
+      rm -rf "$build_root"
+      ;;
   esac
 }
diff --git a/nix/scripts/gateway-install.sh b/nix/scripts/gateway-install.sh
index e3d26b5..712d256 100755
--- a/nix/scripts/gateway-install.sh
+++ b/nix/scripts/gateway-install.sh
@@ -140,8 +140,8 @@ fi
 
 log_step "validate node_modules symlinks" check_no_broken_symlinks "$out/lib/openclaw/node_modules"
 
-bash -e -c '. "$STDENV_SETUP"; makeWrapper "$NODE_BIN" "$out/bin/openclaw" --add-flags "$out/lib/openclaw/dist/index.js" --set-default OPENCLAW_NIX_MODE "1"'
+log_step "wrap openclaw" bash -e -c '. "$STDENV_SETUP"; makeWrapper "$NODE_BIN" "$out/bin/openclaw" --add-flags "$out/lib/openclaw/dist/index.js" --set-default OPENCLAW_NIX_MODE "1"'
 
 if [ -n "${OPENCLAW_BUILD_ROOT_SH:-}" ]; then
-  openclaw_cleanup_output_build_root
+  log_step "discard build root" openclaw_cleanup_output_build_root
 fi