diff --git a/scripts/install.sh b/scripts/install.sh
index d735c6d75b..e24e6537b6 100755
--- a/scripts/install.sh
+++ b/scripts/install.sh
@@ -2307,6 +2307,16 @@ install_desktop() {
     log_info "Installing desktop workspace dependencies (includes Electron ~150MB, 1-3min)..."
     ( cd "$INSTALL_DIR" && npm ci ) || ( cd "$INSTALL_DIR" && npm install ) || {
         log_error "Desktop workspace npm install failed"
+        # Common cause: a previous 'sudo npm'/'sudo npx' left root-owned files in
+        # ~/.npm, so this non-root install can't write the shared cache. npm hides
+        # it behind a confusing EEXIST / "File exists" message while the real errno
+        # is EACCES (-13). Point the user at the fix instead of a raw npm trace.
+        log_info "If the errors above mention EACCES / 'permission denied' / EEXIST while"
+        log_info "writing the npm cache, your ~/.npm likely holds root-owned files from an"
+        log_info "earlier 'sudo npm' or 'sudo npx'. Reclaim ownership and retry:"
+        log_info "  sudo chown -R \"\$(id -un)\" ~/.npm && npm cache verify"
+        log_info "Then re-run this installer, or build manually:"
+        log_info "  cd \"$INSTALL_DIR\" && npm ci && cd apps/desktop && npm run pack"
         return 1
     }
     log_success "Desktop workspace dependencies installed"