Nebu

Nebu (named after the Nebuchadnezzar, the ship of the free from The Matrix) is an enterprise chat server that implements the Matrix Client-Server API. Standard Matrix clients (Element, Cinny, FluffyChat and others) work out of the box without any modifications.

Nebu is built for organizations that require full data sovereignty: on-premise deployment, no vendor lock-in, no telemetry, and no federation overhead.

Architecture: Two runtime components - a single Elixir/OTP application (Matrix API, media gateway and Admin UI as the module namespaces Nebu.Matrix/Media/Admin; Room GenServers via Horde, Session Manager via ETS, Presence, Event Dispatcher) and PostgreSQL as an append-only event log. No Go, no Redis, no NATS, no Kafka.

Security and Compliance: OIDC-only authentication (Keycloak, Azure AD, Google Workspace, Dex), Ed25519 message signatures for authenticity and non-repudiation, audit logging, legal export, and four-eyes principle for privileged access.

Implemented Matrix Scope: Login, logout, sync, send, messages, createRoom, join, typing, receipts, profile, presence, media upload/download/thumbnail, key stubs (E2EE suppression). Intentionally excluded: federation, identity server, E2EE (by design).

Tech Stack: Elixir/OTP 1.19+ (Bandit, Plug, Phoenix LiveView), PostgreSQL 16+, Docker.