OpenAI cuts GPT-5.6 Luna and Terra API prices and adds Fast mode to Sol

OpenAI cut API prices for two GPT-5.6 models, with Luna down 80% to $0.20 per million input tokens and $1.20 per million output tokens. Terra drops 20% to $2 input and $12 output per million tokens. GPT-5.6 Sol gains a Fast mode in the API that offers up to 2.5x the speed for 2x the price at the same intelligence level.