Welcome to Antithesis

What is Antithesis?

Antithesis is a tool for verifying complex distributed systems. It supplements or replaces your existing testing tools and lives alongside your normal CI workflow.

Antithesis works like an additional staging environment. When you deploy to Antithesis, we run multiple copies of your software in a simulation environment that’s much more hostile than prod. This quickly exposes the bugs in your software — even the most complicated, unlikely, and lethal ones. Essentially, it tests your software without you writing tests — which is vital if you’re going to keep up with AI writing code.

Unlike a conventional shared staging environment, you never have to babysit your system, compete for deployment locks, or worry about what’s changed under you since you last deployed.

And because Antithesis’ simulation is perfectly deterministic, you get perfect, effortless repro of any problems you find.

Who is Antithesis for?

Antithesis is primarily used by developers building stateful distributed systems, with coding agents or by hand. Antithesis offers an API, CLI, and agent skills which make it usable by any agent.

If you’re interested in testing program logic at the application level, we also offer Hegel, a universal property-based testing engine and family of libraries. Hegel is open source and available in many different languages.

If you’re interested in testing a web or terminal UI, we offer Bombadil, an open-source property-based testing tool.

We also offer agent skills for both Hegel and Bombadil.

What next?

If you’re new to Antithesis, having a clear mental model of how Antithesis works really helps, so we recommend reading that next. You may want to read these docs from start to finish, like a book, and, other than the reference docs, they’re written to be read that way.

Once you’re ready, contact us at support@antithesis.com or ask on our Discord to request a container registry and credentials.

Or, if you’re just exploring and want to see how this is going to fit your workflow, here’s a 5 minute video.