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

METR's 11-week review, conducted August 12 to October 29, 2026, with data Anthropic chose to share, found that Anthropic's capability trend on its AECI index has grown about 1.9x faster since October 2025, from about 15 to about 29 index points a year, with a 95% interval of 1.5x to 2.8x. METR reports that swapping the link function, which encodes assumptions about how benchmark tasks are spread by difficulty, yields results from 1.1x to 2.9x, and that most of these curves fit the data about equally well. METR says about 80% of the October 2026 speedup comes from AI itself as a judgment rather than a measurement, and that Anthropic redacted most of the evidence METR found most useful and cancelled one planned check midway.