Why OpenAI co-founder and the world's most famous AI researcher just joined Anthropic

Andrej Karpathy joined Anthropic on 19 May 2026. Most people read it as an OpenAI story — he co-founded the lab, left twice, and landed at the rival.

That's not what this is. Eight weeks before he made the call, Karpathy built a 630-line Python script that ran 300 experiments on his own code in two days and found improvements he'd missed after months of hand-optimizing.

He called it "the final boss battle." Anthropic then offered him the mandate to run that exact loop at the most consequential scale in the industry: using Claude to accelerate its own pre-training research.

In this episode of In The Loop, I'm tracing what actually changed Karpathy's mind — from calling AI agents "terrible" in October 2025 to joining the lab pushing recursive self-improvement six months later.

I cover autoresearch, what it found, and why Dario Amodei's quote about the AI-assistance multiplier is the most important thing said in frontier AI right now.

⏭️ Episode highlights

(01:15) – Karpathy calls AI agents "terrible" in Oct 2025

(02:30) – What changed: coding agents that basically work now

(03:30) – 700 experiments, two days, 11% faster training

(05:00) – What pre-training is and why it costs hundreds of millions

(06:15) – AlphaEvolve and Codex: every lab running the same loop

(07:10) – Dario Amodei: the multiplier going from 5% to 40%

(08:20) – The METR study: experienced devs were 19% slower

🔗 Links & resources

• Andrej Karpathy, X post announcing Anthropic hire, 19 May 2026 — https://x.com/karpathy
• GitHub: karpathy/autoresearch — https://github.com/karpathy/autoresearch
• Andrej Karpathy on Dwarkesh Patel podcast, October 2025 — https://dwarkesh.com
• Dario Amodei on Dwarkesh Patel podcast, "We are near the end of the exponential", February 2026 — https://dwarkesh.com/p/dario-amodei-2

Episode transcript with more resources on the Mindset AI blog

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