OpenAI launches GPT-6 Sol at half the price of GPT-5.6 Sol
Both new API models undercut their GPT-5.6 namesakes on every listed token rate, though GPT-5.6 Sol’s current rate is itself a promotional price due to run at least until 21 November
- Cached input costs 10% of the standard input rate: $0.20 per million tokens for Sol and $0.01 for Luna.
- Batch and Flex processing are priced at half of standard rates, and fast mode at twice.
- Regional processing adds a 10% premium where available, and EU data residency is available only with standard processing.
- On 25 September OpenAI fixed an image encoding bug that had degraded image understanding in both models.
Teams running production workloads on GPT-5.6 should plan a move, but on their own evaluations rather than the price sheet. A cheaper model only saves money if it holds quality on the organization’s own prompts, so rerun test suites, especially anything using images, before switching. Check the long-prompt surcharge against real context sizes, and ask suppliers who quoted on old token rates whether the saving reaches the invoice.
OpenAI released GPT-6 Sol and GPT-6 Luna in its application programming interface (API) on 22 September 2026. Sol, which OpenAI says is built for complex coding and agentic workflows, costs $2 (£1.51) per million input tokens and $10 (£7.55) per million output tokens at standard rates, according to the API changelog.
That is half the $4 (£3.02) input and $20 (£15.10) output that GPT-5.6 Sol has cost since 21 August, when OpenAI cut its input rate by 20% and its output rate by 33%. That lower rate is itself promotional, and OpenAI says it runs at least through 21 November.
Luna, which OpenAI describes as its most efficient model for focused, high-volume tasks, costs $0.10 (£0.08) input and $0.50 (£0.38) output, against $0.20 and $1.20 for GPT-5.6 Luna. Both new models have a 1.05 million-token context window and return up to 128,000 tokens. Prompts of more than 272,000 input tokens are charged at twice the input rate and 1.5 times the output rate.
Sources
- OpenAI, API changelog, entries for 21 August, 22 September and 25 September 2026. https://developers.openai.com/api/docs/changelog
- OpenAI, “GPT-6 Sol”, API model documentation, accessed 26 September 2026. https://developers.openai.com/api/docs/models/gpt-6-sol
- OpenAI, “GPT-6 Luna”, API model documentation, accessed 26 September 2026. https://developers.openai.com/api/docs/models/gpt-6-luna
- OpenAI, “GPT-5.6 Sol”, API model documentation, accessed 26 September 2026. https://developers.openai.com/api/docs/models/gpt-5.6-sol
- OpenAI, “GPT-5.6 Luna”, API model documentation, accessed 26 September 2026. https://developers.openai.com/api/docs/models/gpt-5.6-luna
