Your chat server should be able to talk to everyone else's chat server: Synapse is the reference homeserver for the Matrix network, hosting your users, rooms, and message history on infrastructure you control while federating openly with thousands of other servers. People keep their own identity on your domain and still message friends, colleagues, and communities elsewhere, because rooms are shared across servers instead of locked inside one company's silo. Any Matrix client works against it, from Element on phones and desktops to a shelf of community clients, and end-to-end encrypted conversations stay readable only by their participants. Bridges and application services wire the network into Slack, Discord, Telegram, IRC, and other systems, so existing conversations can move across gradually instead of in one painful migration weekend. Single sign-on through SAML or OpenID Connect folds chat accounts into the identity provider your organization already runs, and guests, registration controls, and rate limits stay in your hands. Media uploads, message history, and user data live in your PostgreSQL database and your file storage, with retention and federation policies set per room or for the whole server. When one process is no longer enough, worker processes split the load, Prometheus metrics show where it goes, and the admin API handles accounts, rooms, and moderation programmatically. Running on a dedicated VPS on RepoCloud with guaranteed CPU, RAM, and SSD, full root SSH access, and a browser serial console. AGPL-3.0 licensed.