It’s a limited release beta feature not available to all. You can try to activate it by doing: /model sonnet[1m] And it accepts it but the at the next API c

It’s a limited release beta feature not available to all. You can try to activate it by doing: /model sonnet[1m] And it accepts it but the at the next API call it may fail and say “this beta model is not available with your subscription”. I haven’t gotten access yet. One of the nice things about Codex (GPT-5) is the supposed 400k token context (although performance starts to deteriorate when you get to 80% context usage).