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Tailcat is a command line tool from Tailscale that sends text and files between two machines using Tailscale's WireGuard-based encryption and NAT traversal, without the Tailscale control plane. The receiving side prints an address; the sender passes that address to tailcat. The tool also serves SSH, files, web servers, and forwarded ports, and ships as a Go library and a WebAssembly build.
Tailscale used SQLite as its primary database starting in 2022. From August 2025, backups upload to S3 began showing corruption, occurring 19 times over six months, each time forcing a control plane process to stop for repair or restore. Recent code changes were ruled out. Tailscale signed a support contract with SQLite developers and built a transaction log pipeline, which helped lead the SQLite team to a bug latent in the database for 16 years.