'As we describe below, we were able to confidently determine that the acceleration was not due to an acceleration in the rate of growth of training compute.'

'The acceleration in late 2025 was likely influenced by non-AI factors. We investigated a variety of factors which could have contributed to the observed acceleration in late 2025, but details of many of these factors have been redacted.

We guess that a majority (perhaps ≈80%) of the current (October 2026) acceleration is due to AI. This judgment is given with substantial uncertainty, but is based on a variety of lines of evidence on contributions from AI and other causes. We believe AI’s contribution has grown relatively more important over time, and do not think the other factors we investigated would explain the sustained acceleration. The evidence of speedup from the usage of AI we describe below also seems compatible with a large contribution.'

'Our more detailed estimates for the cumulative and instantaneous effects of AI on Anthropic’s rate of progress in AECI, and at various stages of the model training pipeline, were redacted.'