GPT-5.6-Terra vs. GPT-5.5

[merefield]

Suspect the latter (judging by the token prices) but I’ve been having great results with Terra.

And it depends what you are doing.

See this discussion:

Introducing GPT-5.6 series: Sol, Terra and Luna. Coming July 9 10am PT

Surely the big story here is just how good Terra and Luna are on higher reasoning levels - why use Sol for agentic coding? It just seems to escalate cost dramatically for little or no gain. This demonstrates how the smaller models capabilities also appear to scale well with test-time compute - impressive!