OpenAI's GPT-6 Sol and Luna arrive at half the price of GPT-5.6

OpenAI released GPT-6 Sol (gpt-6-sol) and GPT-6 Luna (gpt-6-luna) in its API on September 22, 2026. Its announcement says API prices for both are 50% lower than GPT-5.6’s promotional pricing. A week later, on September 29, OpenAI added GPT-6.1 Sol (gpt-6.1-sol) at the same base price as GPT-6 Sol.

What they cost

Standard prices per 1M tokens for prompts up to 272K tokens, from OpenAI’s pricing page on October 18, 2026:

Model	Input	Cached input	Output
GPT-6.1 Sol	$2.00	$0.10	$10.00
GPT-6 Sol	$2.00	$0.20	$10.00
GPT-6 Luna	$0.10	$0.01	$0.50
GPT-5.6 Sol	$4.00	$0.40	$20.00
GPT-5.6 Luna	$0.20	$0.02	$1.20

The GPT-5.6 Sol price above is itself a promotion that OpenAI says runs at least through November 21, 2026. Prompts over 272K input tokens are billed at 2x input and 1.5x output for the whole request. Batch and Flex cost half; Fast mode costs double.

GPT-6.1 Sol halves the cached-input rate of GPT-6 Sol, from $0.20 to $0.10, so apps that reuse long prompts pay less on it. OpenAI describes it as a model for complex coding and professional work at a lower cost than GPT-6 Astra.

Specs

Both GPT-6 models take text and images and return text. Each has a 1,050,000-token context window and up to 128,000 output tokens. The knowledge cutoff is April 20, 2026 for Sol and May 18, 2026 for Luna. Reasoning effort runs from none to max, with medium as the default.

Where else they run

The announcement says both models rolled out the same day in ChatGPT Work and Codex for Plus, Pro, Business, Enterprise and Edu users, and that Free and Go users could try Luna in the desktop app.

What to do

If you still call GPT-5.6 Sol or Luna, the GPT-6 versions cost less per token. Test them on your own prompts first, and compare total cost per task, since reasoning models can use different amounts of output tokens.