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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 Sonnet 5.5GPT-5.6 Terra

Next to Claude Sonnet 5.5

Presets

Claude Sonnet 5.5

193182–205

WeightsClosed

ReleasedSep 2026

Price in / out$2.0 / $10

Context1M

Core tests taken3 of 8

GPT-5.6 Terra

178167–189

WeightsClosed

ReleasedJul 2026

Price in / out$2.0 / $12

Context1.05M

Core tests taken4 of 8

Claude Sonnet 5.5 leads GPT-5.6 Terra by 15 points, ahead on 3 of 3 shared core tests, at a similar price.

Test by testindependent results · Epoch AI

Claude Sonnet 5.5GPT-5.6 Terra

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.