In your project you probably will have many routes where you expect a tenant has been made current.
You can ensure that a current tenant has been set by applying the \Spatie\Multitenancy\Http\Middleware\NeedsTenant middleware on those routes.
We recommend registering this middleware in a group alongside \Spatie\Multitenancy\Http\Middleware\EnsureValidTenantSession, to also verify that the session is not being abused across multiple tenants.
With the middleware registered, you can use it in routes files (or in a route service provider).
// in a routes file
If the request does not have a "current" tenant for these routes, an Spatie\Multitenancy\Exceptions\NoCurrentTenant exception will be thrown. You can listen for that exception in the exception handler. You could set some kind of flash message and redirect to a login page there.