Claude Mythos 5.1

Provider

Statuspublic

AA Intelligence Indexn/a

Released2026-09-01

Context windown/a

Modalitiesn/a

API price $/1M (in / out)n/a

Speedn/a

AccessReleased September 1, 2026 alongside Fable 5.1 · availability varies by plan

The score shown is a WhichAI estimate from adjacent benchmarks, not an official measurement.

In one line

Shipped the same day as Fable 5.1 and aimed at technical and scientific work (52.6% on Terminal-Bench Science at launch). No index score published yet, so the figure here is an unmeasured estimate and this entry never enters a ranking.

Category scores (0-100) are WhichAI blended ratings: public category leaderboards plus editorial judgment. Guidance, not official measurements.

Alternatives worth a look

• Phi-4 (Microsoft) · AA 4.9Open weights · laptop-friendly
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• LFM2.5 (Liquid AI) · AA 8.3Open weights · edge/on-device

Artificial Analysis Intelligence Index, 2026 rebased scale (top models ~ 55-66). Snapshot: September 4, 2026 (BenchLM mirror), retrieved September 8, 2026. Specs and prices come from the OpenRouter public model list on the same date. Models nobody has measured carry no index score at all and never enter a ranking: where an estimate exists it is shown separately and labelled unmeasured. Context, price, modality and release dates come from the public OpenRouter model list (retrieved September 8, 2026) and vendor pages. Missing values are not published or not yet verified - shown as -. Sources are linked inside the app (Model guide and About > Methodology).