Two New Minds for Your Team: Fable 5.1 and GPT-6 Astra

An AI employee is only as good as the thinking behind it. This week, the thinking got a serious upgrade: Fable 5.1 and GPT-6 Astra, the two most capable thinking powers we have ever offered, are now available to every AgentTeams employee.

If you have read our take on matching thinking power to the work, you know where this is going. These are not upgrades you switch on everywhere. They are the principal engineers of your AI team: you assign them where the work is genuinely hard, and you keep the fast, efficient minds on the work that repeats all day.

Fable 5.1: a new class of deep thinker

Fable 5.1 is the strongest mind on the platform, full stop. It belongs to a new generation that sits above anything we offered before, and it shows in exactly the places you would hope: long, messy documents that need genuine understanding rather than skimming. Multi-step analysis where the third step depends on getting the first two right. Judgment calls with real consequences, where a confident wrong answer costs far more than a slow right one.

Give it to the employee who reviews contracts, reconciles numbers that refuse to match, or untangles the support case that five people already gave up on. For everything else, Opus 5, the new default, is now quietly better than what your team ran on last week, and Sonnet 5 joins as the quick, capable everyday choice. Your employees moved up a generation without you touching anything.

GPT-6 Astra: the newest generation, included in your plan

Teams that run their AI employees through a ChatGPT plan get the same kind of jump. GPT-6 Astra is the newest generation on that side, included in every paid ChatGPT plan, and it becomes the natural pick for demanding work. Alongside it, GPT-5.6 Sol arrives as the deepest reasoner of the previous generation, now available on both Pro and Team plans.

This is one of the quiet advantages of how AgentTeams is built: your employees are not welded to one mind or one vendor. When a better one appears, on either side, it shows up in the picker and your team can start using it the same day.

Assign them like you would assign people

Every employee has a thinking power setting on their profile, under Settings. Changing it takes one click and applies from the next conversation onward. The pattern that works: pick one employee whose work is genuinely hard, move them to Fable 5.1 or GPT-6 Astra, and compare a week of output against the week before. Then decide with evidence.

The rest of your team does not need to change. That is the whole point: the right mind for each job, not the biggest mind for every job.