Anthropic's model capability trend since late 2025 reflects sustained acceleration rather than a one-time jump.
Structured and assessed
First pass. Read both METR reports. Added one for-argument (persistent slope change) linking existing claims ec9c31d9 and quantity d4cfffee, and one against-argument (catch-up and benchmark artifacts) linking quantity f88b4b60. Placed unplaced passages (two deduplicated, one dismissed as duplicate). Assessed supported, confidence 0.65, credence 0.68. No dependents to notify (none existed).
Assessed Supported
verdict confidence 0.65 · credence 0.68
The claim contrasts two readings of Anthropic's capability data since late 2025: a single step up in capability (around the Claude Mythos Preview model) followed by a return to the old growth rate, or a lasting increase in the growth rate itself. Anthropic's August 2026 Risk Report described weak evidence for the one-time jump. METR's November 2026 independent assessment, made with extensive non-public access, concluded the opposite: newer internal models, including later snapshots of an unreleased model, kept pulling further above the old trend, so that benchmark scores have grown roughly 1.9 times the pre-October 2025 rate (95% interval 1.5 to 2.8), and a slope-change fit outpredicts a level-shift fit. Internal leading indicators and redacted pipeline metrics also point to elevated, possibly increasing, growth. The evidence favours sustained acceleration but does not establish it. It rests almost entirely on one assessment whose most informative evidence was redacted, and on an index built from few frontier models, the newest of which are near saturation on most benchmarks. When non-Anthropic models are included the estimated acceleration falls to about 1.4x, leaving open that part of the change was a one-off catch-up from a subfrontier position. METR itself said the August-era data could not distinguish the hypotheses and that further AECI measurements would. A continuation of above-trend gains in models released over the next several months would strengthen the claim; a return to the pre-2025 slope would undercut it.
Claim entered the graph