Fly.io has introduced an SSH feature for its platform, which enables users to pop a shell on their applications hosted on the provider. The new feature is built using 6PN and Hallpass, with authentication handled by SSH client certificates. Additionally, user-mode TCP/IP WireGuard has been implemented to allow SSH into instances without installing WireGuard. This development aims to provide users with more flexibility and control over their applications hosted on Fly.io.