Function gate 

pub async fn gate(request: Request, next: Next) -> Response

Refuse anything that did not come from this launch.

Wired by the native host as the outermost layer:

router.layer(axum::middleware::from_fn(rahti_native::gate))

Wired only when security.loopbackToken is on, which is why there is no runtime switch here — a project that turned it off does not have this layer in its router at all, rather than having a layer that decides it does not apply.