OpenAI adds Ultrafast mode for GPT-6 Astra
OpenAI added Ultrafast mode for GPT-6 Astra in the Responses API. API customers can use the ultrafast service tier to reduce the time between generated output tokens, subject to rate limits.
Models: GPT-6 Astra
Source: OpenAI API changelog, checked Sep 29, 2026. Summarized from the provider’s announcement.