OpenAI's GPT-6.1 Sol launch

OpenAI released GPT-6.1 Sol on September 29, 2026 at DevDay, priced at one-fifth of GPT-6 Astra with a 95% cache read discount on cached reads. The model slots below GPT-6 Astra and above GPT-6 Luna in the GPT-6 family, released one week after GPT-6 Sol and 26 days after GPT-6 Astra. Sam Altman described it as 'an absolute workhorse' delivering 'near Astra intelligence.' Standard input and output token rates remain unchanged from GPT-6 Sol, but cached reads cost less and the tool-calling contract changed. Tool calling is supported only through the Responses API, and ChatGPT Chat access was not yet available at announcement. OpenAI also launched an Ultrafast service tier delivering up to approximately 300 tokens per second across GPT-6-class models at 6x the corresponding model's standard rate, available immediately for GPT-6 Astra and expected for GPT-6.1 Sol within days of announcement. Safety evaluations show GPT-6.1 Sol outperforms earlier Sol models on most health and safety benchmarks while trailing GPT-6 Astra on exploit capability.