Atrium — Team chat, refined.

Everything a team needs

Fast where it matters,
quiet where it doesn't.

The full chat surface — without the noise, and without a fleet of services underneath.

Channels, threads & DMs

Public & private channels, group DMs, threads, reactions, pins, saved items — starred and muted views of it all.

Ada Lovelace11:57

Welcome to Atrium — flat surfaces, hairline borders, one indigo accent. Try @grace mentions.

🔥 2🎉 1

1 reply →

Grace Hopper11:58

The new design system is so quiet. It is just content.

Ada is typing…

Apps & agents

Bot tokens, incoming webhooks, slash commands, and HMAC-signed events. Build bots and agents on the same API users get.

Search that finds

Full-text search with filters, highlighted snippets, and jump-to-message.

Mac desktop app

A native-window shell with dock badges and notifications — pointed at any Atrium server you like.

Security by default

Reviewed, tested, and documented — hardened before it was ever public.

A platform, not just a product

Build apps on the
same surface.

Everything the client can do, your code can do. No separate “app platform” — one API, one token model.

✓Bot tokens call the entire REST API, scoped to their workspace.
✓Incoming webhooks post from anything with curl — CI, alerts, cron.
✓Slash commands with signed callbacks, in-channel or ephemeral.
✓Events API — messages, reactions, mentions, delivered HMAC-signed with retries.
✓Agents welcome — the realtime socket accepts bot tokens too.

zsh — deploy-bot

# post from your deploy pipeline
$ curl -X POST https://chat.example.com/hooks/$TOKEN \
    -H 'Content-Type: application/json' \
    -d '{"text":"Deploy to prod finished ✅"}'

# or drive the API as a bot
$ curl https://chat.example.com/api/v1/channels/$CH/messages \
    -H "Authorization: Bearer xatb-…" \
    -d '{"text":"bot speaking"}'
201 ✓ delivered

Slack Connect, but yours

Federated by design.

Every Atrium server is sovereign. Connect two of them with a single-use invite code, and workspaces can share channels and DM across the wire — signed, rate-limited, and revocable.

acme.example.com Sovereign

partner.example.com Sovereign

HMAC-signed relay · single-use invite · revocable at either end

Shared channels

One channel, two servers. Messages relay both ways with per-server identity intact.

External DMs

Message people on federated servers directly — no shared account, no shared database.

Revocable trust

Either side can sever the link at any time. Signing keys rotate; history stays local.

Deploy

One box. One process. One file.

Atrium ships as a single Node process with SQLite built in. No Postgres, no Redis, no SMTP, no build step. A €5 VPS and a domain is the whole bill.

Get a box

Any 1 vCPU / 1 GB VPS, or a container host. Ubuntu 24.04 works out of the gate.

Point a domain

One A record. Caddy issues TLS automatically — federation requires it.

Run it

docker compose up -d or npm install && npm start. Migrations run at boot.

Set it up

Open the URL: setup wizard, then create a workspace or join with an invite link.

ssh root@your-box

$ git clone https://github.com/atrium/atrium && cd atrium
$ npm install && npm start
✓ migrations applied — sqlite at ./data/atrium.db
✓ atrium listening on https://chat.example.com
— that's it. no database server, no build step.

✓What you need

Node ≥ 22.5 or Docker · persistent disk for ./data · TLS for public use · a domain (or a free PaaS subdomain)

✕What you don't

~~Database server~~ · ~~SMTP / email provider~~ · ~~object storage~~ · ~~build tooling~~ · ~~license server~~

Fast where it matters,quiet where it doesn't.