Antithesis: Deterministic Simulation Testing Platform for Financial and Crypto Systems.

Antithesis, a deterministic simulation testing platform, is rethinking how software has been tested for the last 80 years. The startup uses a controlled simulation to run customer systems, injecting hardware failures, network glitches, and timing issues to see how software behaves. Antithesis is used by organizations such as quantitative trading giant Jane Street, the Ethereum network, and MongoDB. The company raised a $105 million Series A in December 2025, led by Jane Street and Amplify Venture Partners.