A username is a signed claim with an expiry and a home node id, taken first come first served through the PKI node, mirrored on every node, with mirrors rejecting anything that is not append-only.

It is the one global thing in the system, and it is built so that no one can rewrite it.

A username maps to an identity public key. The map is a global, append only log. A ledger copied to everyone.

To take a name, you sign a claim. It carries an expiry, and the id of your home server.

Names are first come, first served. That needs consensus, so one node, the PKI node, confirms each claim.

The log is mirrored on every Peergos node. Mirrors reject any update that is not append only.

Mirrors do not just notice a rewrite. They refuse it. Like a key transparency log, a public record of keys, but used as the source of truth.

Check yourself. What does a mirror do with an update that changes an old mapping?