Nix Sandbox

Run commands or tools in an isolated nix-shell sandbox without modifying the system. Use this skill whenever a needed tool or package isn't in PATH, the user says 'without installing' or 'don't touch my system', or you'd otherwise suggest nix-shell or nix run. Trigger automatically on 'command not found' errors, Python ModuleNotFoundError, Node 'Cannot find module', Ruby LoadError, or any time you would otherwise run or suggest pip install / pip3 install / gem install / npm install -g for a tool (not a project library). The skill handles platform detection and constructs the correct sandbox invocation for macOS (sandbox-exec) or Linux (bwrap) automatically.