Function default_exec_path 

pub fn default_exec_path() -> String

The default PATH for a fully-authorized (exec = Scope::All) confined child: the ambient $PATH when set and non-empty, else the conventional RootfsPolicy search dirs, joined with the platform separator.

The sandbox-host engine (HostShellTool, in agent-bridle-tool-shell) seeds this into the child so bare program names (grep/ls/find) resolve like the host shell would, instead of leaning on the shell’s fragile compiled _CS_PATH fallback. It is only meaningful — and only called — when exec is unrestricted, so seeding it grants nothing the caller’s exec authority does not already permit; env_clear still scrubs everything else. Mirrors the exec-search-dir precedence that anchors the L3 Execute allow-list (sandbox::exec_search_dirs); kept here so it constructs on every platform.