OpenAI expands GPT-6 lineup with cheaper Sol and Luna models


People visit an OpenAI booth at Moscone Center during the Dreamforce 2026 technology summit in San Francisco, California, US, September 17, 2026. REUTERS/Carlos Barria

Sept 22 (Reuters) - OpenAI on ⁠Tuesday expanded its GPT-6 AI lineup with two models ⁠priced at half the promotional rates of their predecessors, ‌while offering some of the capabilities of its flagship Astra.

The launch of low-cost GPT-6 Sol and GPT-6 Luna follows the rollout of GPT-6 Astra, a ​faster model for handling more tasks ⁠than previous iterations, earlier this ⁠month.

This comes as AI companies focus on reducing the cost ⁠of ‌running increasingly capable models.

GPT-6 Sol will cost $2 per million input tokens and $10 per million output tokens, down 50% ⁠from GPT-5.6 Sol's promotional prices, while GPT-6 Luna ​will cost $0.10 ‌per million input tokens and $0.50 per million output tokens.

OpenAI has ⁠also cautioned ​that Astra can sometimes attempt to evade human monitoring, as it faces growing scrutiny over the behavior of its AI agents, including ⁠incidents in which they accessed other ​companies' systems.

While Astra would remain its most capable model for demanding projects, GPT-6 Sol and Luna were designed to offer lower-cost options ⁠for professional work, coding, automation and computer-use tasks, the company said.

OpenAI said it has trained Sol and Luna using methods similar to those used for Astra, including improvements in reasoning, factual ​reliability, coding, computer use and alignment.

"Improvements ⁠in caching and inference let us serve these models at lower ​cost, and we're passing those savings ‌directly on to users and customers," ​it said.

(Reporting by Harshita Mary Varghese in Bengaluru and Deepa Seetharaman in San Francisco; Editing by Shilpi Majumdar)

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