Up to four models

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Side by side on the same independent tests, with price and context. The link in your address bar shares this exact comparison.

Claude Opus 5.5Claude Fable 5.1

Next to Claude Opus 5.5

Presets

Claude Opus 5.5

200188–211

WeightsClosed

ReleasedSep 2026

Price in / out$4.0 / $20

Context1M

Core tests taken4 of 8

Claude Fable 5.1

192181–203

WeightsClosed

ReleasedSep 2026

Price in / out$10 / $50

Context1M

Core tests taken4 of 8

Claude Opus 5.5 leads Claude Fable 5.1 by 8 points, ahead on 3 of 3 shared core tests, and costs 2.5× less.

Test by testindependent results · Epoch AI

Claude Opus 5.5Claude Fable 5.1

Only tests that at least two of these models have taken. Bold rows are the core tests shown on every profile; all of these results inform the index score. Task length (METR) is listed below the chart because it is a duration, not a percentage.