nanochat is Karpathy’s open repository for training and running a small ChatGPT-like model end to end; its own tagline is ‘the best ChatGPT that $100 can buy’. It enters this corpus on 29 December 2025 as the project whose optimization experiments Claude now conducts, the object of the loop rather than an agent in it, a pattern that returns in his later autoresearch project, which ran 650 experiments in two days.
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nanochat
Andrej Karpathy's minimal, end-to-end codebase for training and serving a small ChatGPT-style model, the project whose optimization loop he handed to Claude.
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- Welcome to December 29, 2025 (theinnermostloop.substack.com)
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