Apply `server.fs` access controls consistently to module fetching performed through development-environment transports. Custom environment transports must be denied access to modules outside `server.fs.allow` by default. The browser-facing WebSocket transport must not expose module fetching at all, even for allowed files. Preserve trusted server-side flows: `ssrLoadModule` and in-process server module runners must continue to load modules normally, without broadening access for custom transports.