Julian Schrittwieser
About Julian Schrittwieser
Julian Schrittwieser is a Member of Technical Staff at Anthropic, where he works on reinforcement learning and deep learning. He joined in October 2024 after about 10 years at Google DeepMind, where his last title was Principal Research Engineer.
At DeepMind he worked on AlphaGo, AlphaZero, MuZero, AlphaCode, AlphaTensor and AlphaProof, and he contributed to the Gemini models. He also developed OpenSpiel, a framework for reinforcement learning research in games. His MuZero paper was published in Nature.
He writes publicly about AI progress on his personal site. A September 2025 post argues that public discussion underestimates recent AI progress.
Public information about his angel investing is limited to company funding announcements that name him as a participating angel. No fund, syndicate or total number of investments has been published that we could find. The announcements we found cover 2026.
Preference Model raised a $16M seed round, which the Lounge deals desk dates to 2026-10. Press coverage says the round was led by Andreessen Horowitz, with SignalFire, South Park Commons, Scale Angel Group and researchers including Fei-Fei Li, Ian Goodfellow and Schrittwieser taking part. The company builds reinforcement learning environments for training AI systems, designed to resist reward hacking. It says it has built such environments for several frontier AI labs.
In January 2026, depthfirst raised a $40M Series A led by Accel. Schrittwieser was among the angel investors named in the round. depthfirst builds an agentic approach to software security.
The two public examples are in AI, one in reinforcement learning infrastructure for frontier labs and one in AI-driven security. His own research background is in reinforcement learning, self-play and code and math reasoning. He has not published a check size, preferred stage or geographic focus. Founders should not assume any of these from the two examples.
- Preference Model: builds reinforcement learning environments for training AI systems. He took part in its $16M seed round (2026-10 on the Lounge deals desk), led by Andreessen Horowitz.
- depthfirst: agentic software security company. He was a named angel in its $40M Series A, announced January 2026 and led by Accel.
Investing activity
Julian Schrittwieser appears in 1 AI deal tracked by the Lounge deals desk, rounds totalling $16M. The rounds are mostly Seed, with a median round size of $16M. The most recent is Preference Model (Seed, $16M, Oct 2026).
Julian Schrittwieser most often invests alongside Andreessen Horowitz, South Park Commons, Fei-Fei Li and Ian Goodfellow, and the companies they back on Lounge are mostly in AI.
Deals
Frequently asked questions about Julian Schrittwieser
Who is Julian Schrittwieser?
He is a Member of Technical Staff at Anthropic and a former Principal Research Engineer at Google DeepMind. He co-created AlphaZero and MuZero and worked on AlphaGo.
Has Julian Schrittwieser invested in Preference Model?
Yes. Press coverage of Preference Model's $16M seed round, led by Andreessen Horowitz, lists him among the participating researchers and angels.
What is Julian Schrittwieser's angel check size?
He has not published a check size. Any figure you see elsewhere is not confirmed by the sources we found.
What kinds of AI startups has Julian Schrittwieser backed?
Publicly named investments are Preference Model, which builds reinforcement learning environments, and depthfirst, which does agentic software security. Both are AI companies.
How can founders reach Julian Schrittwieser?
He is active on X as @Mononofu and has a personal site at julian.ac. He works full time at Anthropic, and he has not said whether he takes inbound pitches.
Is Julian Schrittwieser an angel investor?
Yes. Julian Schrittwieser invests personally as an angel.
What AI companies has Julian Schrittwieser invested in?
Julian Schrittwieser's AI investments include Preference Model. The 1 round on Lounge are listed on this page with amounts, dates and co-investors.
What stage does Julian Schrittwieser invest at?
In the rounds tracked on Lounge, Julian Schrittwieser has invested at Seed, with a median round of $16M.
Who does Julian Schrittwieser co-invest with?
Julian Schrittwieser's most frequent co-investors on Lounge are Andreessen Horowitz (1 deal), South Park Commons (1 deal), Fei-Fei Li (1 deal), Ian Goodfellow (1 deal) and SignalFire (1 deal).