METR's 1.9x AI R&D speedup at Anthropic, and why it ranges from 1.1x to 2.9x

METR, an independent evaluator, published an 11-week assessment concluding that capability progress at Anthropic has run about 1.9x faster since October 2025 (95% interval 1.5x to 2.8x), measured with an internal version of Epoch's capabilities index. The figure depends on a modeling assumption: alternative link functions give 1.1x to 2.9x, and the data fits most about equally well. METR's roughly 80% attribution to AI is a judgment, and Anthropic redacted much of the key evidence, so outside checks are limited.