That has never been made available even to limited customers as far as reporting goes. Currently available ultrafast on GPT-6 Astra and GPT-6.1 Sol are all using Nvidia for good reason [0].
The fact that Cerebras, which has a willing and major customer like OpenAI begging at their heels to deploy on their hardware, now posts about a 2.8T open weight model says a lot.
[0] https://blogs.nvidia.com/blog/gpus-openai-gpt-6-astra-ultraf...
You can get 6.1 sol on ultrafast.
For some reason though on openrouter the tps of 6.1 sol ultrafast is usually lower than opus 5.5 fast. Is there readings off as surely cerebras hardware is faster than low user density nvidia still?
https://openrouter.ai/openai/gpt-6.1-sol
GPT-6.1 Sol Ultrafast also uses Nvidia hardware, not Cerebras, just far better provisioned vs how they usually provide inference allowing for higher throughput.
"Much better provisioned" might be overselling it. Mainly they are just serving very few customers per Nvidia GPU, which is an expensive solution to the problem.
So then how is OpenAI using Cerebras? Or are they not?
Or, from a different perspective: who is using Cerebras for what purpose?
Jane Street bought up all of the Cerebras x OpenAI compute I believe. Couldn't find a great source, this tweet has a good few replies citing other sources as well https://x.com/cryptopunk7213/status/2106834536868856223
Oh that would make a lot of sense, basically supply limited.