If you just saw "The new GPT-5.6 family: Luna, Terra, Sol" and were about to scroll, stop at the part that actually changes your next move. If you mostly use chatbots and are only now tracking AI tools, this is the kind of detail that can waste budget and attention while looking harmless.
gpt-5.6 is not a neutral default. If you skip the specific version name, you are buying Sol. [C002]
The docs frame it as "The new GPT-5.6 family: Luna, Terra, Sol." [C001] OpenAI's model guidance also says the plain gpt-5.6 alias routes to Sol, so the short, safe-looking name is already a cost choice.
And it is not a small cost choice. On OpenAI's July 9, 2026 pricing page, Sol is $5 input / $30 output per 1M tokens. Luna is $1 / $6. Terra is $2.50 / $15. Same family label, very different bill.
This is not a never-use-Sol argument. If the task is hard, Sol may be the right buy. The mistake is drifting into the flagship on cheap, repetitive, or high-volume work just because the name looked generic.
That is my filter for whether an update matters: not how many features it adds, but whether it changes your next decision. GPT-5.6 does. Name the model on purpose, and share this with the person who still types the family name and moves on. Boundary: this is about OpenAI API docs and pricing checked July 13, 2026, not ChatGPT app routing.