GPT-6.1 Sol lowers cached-input cost as OpenAI updates its workhorse

OpenAI introduced GPT-6.1 Sol on 29 September, a week after the Sol and Luna expansion. The release page listed access for Plus, Pro, Business, Enterprise and Edu users in ChatGPT Work and Codex, alongside the API. It was not initially available in Chat. The announcement framed the upgrade around coding, computer use and professional work; the capability comparisons were OpenAI’s own evaluations.

The published API rates were $2 per million input tokens, $10 per million output tokens and $0.10 per million cached input tokens. OpenAI said the cached-input rate was half that of GPT-6 Sol. That distinction matters for applications reusing context, but the discount applies to qualifying cached input, not every token in a request. Output and uncached input remain separate charges. Reported benchmark costs also depended on task and reasoning settings. The release added a lower-cost way to reuse context; it did not establish a universal cost per completed job.