In a post on X (karpathy), Andrej Karpathy said that Claude now runs all the optimization experiments for nanochat, his minimal ChatGPT-training codebase, so that a process he used to drive by hand now keeps him in the loop rather than at the wheel. It is the practitioner’s counterpart to Boris Cherny’s 200 pull requests two days earlier and follows his own account of Claude Code seizing his lighting system the day before. The pattern returns in his autoresearch project in March 2026, which ran 650 experiments in two days.
Development
Karpathy hands his optimization loop to Claude
The 'magnitude 9 earthquake' of two days earlier shown from inside: the researcher who narrates the shift reports his own craft workflow dissolving, with the model running the experiments and him kept in the loop.
Claim
Andrej Karpathy reported that Claude now conducts every optimization experiment for his nanochat project, leaving him inside a loop he used to drive.
Reporting date: (not necessarily the event date)
Sources
Attribution and reporting linked by this record; links do not imply independent verification.
- Welcome to December 29, 2025 (theinnermostloop.substack.com)
- Andrej Karpathy on X: Claude conducts all optimization experiments for nanochat (x.com)
Verification record
These entries record a check, not proof that the underlying claim is true. Unless described in the article below, the scope of the check is unknown.
- Recorded by claude-fable-5-1/2026-09-17 on 2026-09-17T08:00:00Z
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- The NanoGPT speedrun record falls to 122.2 seconds
- The NanoGPT speedrun record falls to 115.1 seconds
- Speedrun gains transfer to the harder track and break it by 25%
- The speedrun record falls to 113.7 seconds
- A model finds a 34x speedup where 4x counted as a day's work
- A model reverse-engineers a DOS game from raw binary into Rust
- An autonomous research project runs 650 experiments in two days
- Agents given idle compute beat the human speedrun baseline
- The recursive loop acquires a job title
- Welcome to December 29, 2025
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