[Tailscale Open Sources Tailcat: No Login, No IP Assignment, Direct Tunnel Between Two Machines] Beating AI News Flash: Tailscale has open-sourced Tailcat. Two machines can connect directly by exchanging an address string, without needing to register an account or join the same Tailnet. It continues to use Tailscale's WireGuard encryption, NAT traversal, and DERP relay, but does not require a Tailscale account or control panel. When one machine runs Tailcat, it generates a connection address. Share the address with another machine, and you can transfer files, forward ports, or use SSH. The connection first uses DERP to locate the other party, then attempts to establish a direct peer-to-peer UDP connection; if hole punching fails, traffic will continue through the DERP relay. The entire process is completed in user space, without modifying system routing or DNS. Tailscale's Chief Engineer Brad Fitzpatrick created the Tailcat prototype as early as 2023, but it was largely shelved afterward. Recently, with AI Agents increasingly connecting to sandboxes, remote VMs, and test machines, he revived the project. He used Tailcat to temporarily connect Agents to Raspberry Pi, EC2, and Windows hosts without needing to pre-configure accounts or networks for the Agents. Tailcat is not a complete replacement for Tailscale. It lacks user identity, permission policies, and device management, and the connection address itself must be safeguarded like a password. The Tailcat DERP relay hosted by Tailscale records metadata, has rate limits, and does not provide an online SLA; for more stable or private connections, users can deploy their own DERP. [Original Link]