Head to head
Claude Sonnet 5 vs GPT-5.6 Terra
Which is better, Claude Sonnet 5 or GPT-5.6 Terra?
GPT-5.6 Terra finishes ahead of Claude Sonnet 5 on the index, 83.6 to 82.5. It is the stronger of the two on Craft, while Claude Sonnet 5 still leads on Speed. Both are scored on the same rubric, in the same week, and neither placing is sponsored.
Updated
Claude Sonnet 5
33 of 73
82.5
Sonnet 5.5 costs exactly the same and is far stronger. There is little reason to stay.
GPT-5.6 Terra
27 of 73
83.6
The sensible middle of the summer line-up, now squeezed out by GPT-6.1 Sol.
The four scores, side by side
| Score | Claude Sonnet 5 | GPT-5.6 Terra | Difference |
|---|---|---|---|
| Craft | 82 | 85 | +3 |
| Speed | 88 | 84 | +4 |
| Control | 89 | 88 | +1 |
| Value | 76 | 76 | — |
| Index score | 82.5 | 83.6 | +1.1 |
Which to pick
Pick GPT-5.6 Terra unless Speed is what decides it for you, which is exactly where Claude Sonnet 5 is the better answer.
Claude Sonnet 5
Sonnet 5 was the coding workhorse of the summer, and it still applies patches that compile and holds up over long tool-calling chains. Sonnet 5.5 now costs exactly the same per token and scores far higher on the Artificial Analysis index, so the only reason to stay is a pipeline you have tuned carefully and do not want to re-test. Anthropic lists it as a legacy model.
Where it shines
- Reliable tool calling over long chains
- Follows a repository's existing conventions
- Well understood after months of heavy production use
GPT-5.6 Terra
Terra was the balanced member of the GPT-5.6 family: quick enough for product work, strong enough for most reasoning, and supported by every framework. GPT-6 has no Terra, and GPT-6.1 Sol now costs the same for input and less for output while scoring far higher, which leaves Terra little reason to exist for new work. It remains active on the API, and its price was cut by a fifth at the end of July.
Where it shines
- Every framework ships an adapter for it
- Million-token context at a mid-tier price
- Predictable structured output in production