Secure Chat

Secure Chat

A community backend that keeps everyone's DMs in readable plaintext is a breach waiting to happen. Storing readable private messages is the bad default Agora refuses to ship — so secure chat is genuinely end-to-end encrypted, and the server cannot read it.

Full design, threat model, schema, endpoints, and roadmap: docs/SECURE_CHAT.md.

A blind delivery service on MLS

Secure chat is built as a blind delivery service on MLS (RFC 9420) — the IETF messaging-layer-security standard, the same family of guarantees as Signal but designed for large, dynamic groups.

• The server is blind. It stores and relays only opaque ciphertext. It enforces who may post and the order of group changes, but never sees what — it learns social-graph + timing metadata only (the Signal-server model). All cryptography is client-side; the server depends on no crypto library.
• No AI in your DMs — on purpose. Secure chat runs no LLM moderation, embeddings, or semantic search. Those require reading content, which is exactly what we refuse to do. That trade is the point.
• A separate path and a separate process. It lives at /v7/:projectId/secure-chat/*, entirely apart from the Replyke-compatible plaintext chat (which is untouched), and runs as its own deployable service (@agora/secure-chat) with its /secure realtime namespace on engine.io path /secure-socket/. See Deployment (--profile secure-chat / --profile full).
• Your keys, your history. Keys live on the client. Two recovery paths — both opaque to the server — restore history onto a re-provisioned device: a passphrase-encrypted backup, and device-to-device history restore (a peer seals back-history into an ephemeral, targeted blob the server relays blindly). See apps/secure-chat/docs/RESTORE.md.
• The crypto stays swappable. All MLS lives behind a small SecureChatCrypto interface, so the concrete core (ts-mls vs OpenMLS-WASM) is a deferred, reversible choice — the server never changes.

Where the code lives

The blind relay (routes, socket, shapes) is the @agora/secure-chat app (apps/secure-chat/README.md). The client crypto packages live in the separate agora-sdk-plus repo (see Ecosystem); this repo only devDepends on the mock for tests.

Diagnostics

A secure-chat log correlator (apps/api/scripts/diag/) lifts the client-SDK and server log streams into one event schema for debugging realtime issues. Background and the longer-term harness plan: docs/SECURE-CHAT-DIAG-HARNESS.md.