OpenAI launches cheaper GPT-6 Sol and Luna models

OpenAI released two new models on Tuesday, September 22, 2026, positioning GPT-6 Sol and GPT-6 Luna as faster, cheaper tiers of its GPT-6 lineup that carry over capabilities from the flagship GPT-6 Astra, which launched earlier in September. The new models are priced at half the promotional rates of their GPT-5.6 predecessors. GPT-6 Sol costs $2 per million input tokens and $10 per million output tokens, down from $4 and $20. GPT-6 Luna costs $0.10 per million input tokens and $0.50 per million output tokens, down from $0.20 and $1.20. OpenAI attributed the lower prices to improvements in caching and inference, saying it is passing those savings on to users and customers. OpenAI said it trained Sol and Luna using methods similar to those used for Astra, bringing advances in reasoning, factuality, coding, computer use and alignment to faster, more affordable models. The company claims GPT-6 Sol makes about half as many factual errors as GPT-5.6 Sol on an internal factuality evaluation based on deidentified real-world conversations.