GPT-5.6 Sol vs Terra vs Luna: Which Tier Should You Ship?
OpenAI's GPT-5.6 family splits into Sol ($5/$30), Terra ($2.50/$15), and Luna ($1/$6) per million tokens, and the bare gpt-5.6 alias quietly routes to the priciest tier. This guide maps workloads to tiers by the cost of a wrong answer, not by spec sheets. It also shows when raising reasoning effort on a cheaper tier beats upgrading, and how 90% cache-read discounts shrink Sol's premium. For PMs, the takeaway is that tier routing is now a margin decision that needs a named owner.