Companion
A productivity app for privacy-minded developers, with end-to-end encryption and your own AI agents.
Companion is the app for flexible thoughts, for privacy-minded developers. It’s one calm workspace where your notes, tasks, and habits live together, and AI is always a message away.
What it does
Notes, tasks, and habits, linked together into a graph you can explore
Your calendars beside your work, with two-way sync for iCloud, Google, Fastmail, or any CalDAV server
Chat with your own AI agent, like Claude Code, Codex, or Ollama, and have it turn a conversation into real notes and tasks. There’s no AI subscription, and nothing is inferred on Companion’s servers.
Offline-first, with no account needed until you want your work on more than one device
End-to-end encrypted sync, through Companion Cloud or a sync server you host yourself
How it’s built
Companion’s business logic is written once, in Go, and shared by every client: it’s compiled to WebAssembly for the web, and runs natively on desktop and mobile. The interface is written once too, in React Native, and runs on the web with React Native Web.
The sync server is a single Go binary, so hosting your own is as simple as running one container.
Where to get it
Companion runs in any browser at web.companionapp.cloud, and as a desktop app on the Mac. Windows, Linux, iOS, and Android apps are on the way.
It’s open source, too. Browse the code on GitHub.