OpenAI published model guidance for GPT-5.6, including Sol, Terra, Luna, migration tips, model settings, and practical prompting rules.
The official Model guidance page covers GPT-5.6, migration, prompting, pro mode, and tool-calling patterns.
The useful part is not just the new model names. The guide is basically a migration checklist: which GPT-5.6 variant to pick, how to set reasoning, when to use pro mode, and how to stop carrying old prompt baggage into newer models.
What changed
The plain `gpt-5.6` alias routes to `gpt-5.6-sol`, the flagship model.
`gpt-5.6-terra` is the middle option: strong performance with a lower price target.
`gpt-5.6-luna` is meant for efficient, high-volume workloads.
Migration should be tested like tuning, not treated as a simple model-name replacement.
Prompting notes to steal
The big advice is simple: start smaller. Old system prompts often contain rules that newer models already handle by default. Keep the behavior that matters, remove repeated generic instructions, and add examples only when an eval shows a real gap.
