DeepSeek releases R1, an open-weight reasoning model

The Chinese laboratory DeepSeek released R1 on 20 January 2025, an open-weight model trained with reinforcement learning to work through problems step by step. It matched OpenAI’s o1 on several benchmarks at a small fraction of the reported training and inference cost.

Why it mattered It put in question whether frontier work required the compute budgets American laboratories were spending, and set off the market selloff of 27 January.