News › GPT-6.1 Sol now available

GPT-6.1 Sol now available

Model launch · 2026-09-30

OpenAI released GPT-6.1 Sol on September 29, and it is available on OneFast as gpt-6.1-sol.

Call it through the endpoint your code already uses:

  • Chat Completions (/v1/chat/completions)
  • Responses (/v1/responses) — including Codex CLI

Because OneFast uses one API key for every model, you can compare GPT-6.1 Sol with Claude Sonnet 5.5, Gemini or open-source models such as DeepSeek V4.1-Flash and Kimi K3 by changing only the model field.

Prompt caching is supported and billed at the cache price. See the model catalog for the live price and Responses API for usage.