Corus is out of preview: what changed

Two weeks ago Corus, our frontier model, became available to everyone. Today it is officially out of the preview window — and the interesting changes are the ones the preview taught us, not the ones we planned.

What the preview changed

Fair-use limits were rebalanced. The initial limits were calibrated for the workload we expected: long research sessions. Real use was different. Legitimate research use — people running long, careful sessions — hit limits faster than we intended, while some very short heavy users were barely constrained. We rebalanced toward what the work actually looks like, and the incident is logged on the status page. The rule is now simpler: limits are generous for research-shaped use, and the emphasis is on keeping the model available rather than rationing it.

The evaluation report is now published. We had planned to publish it this week anyway; the preview made the timing feel less optional. The report includes what we tested, what we found, and what we did not test — including the findings from the public red-teaming round that ran during the preview.

What did not change

Corus is still free for everyone. There is no paywall, no premium tier, and no plan to add one. The fair-use limits are not a business model; they are a capacity question, and the answer to capacity is the same at Curos as it always is: serve more efficiently (see our efficiency work), and keep the most expensive model for the work that needs it.

What you told us

The preview surfaced two patterns we are acting on. People use Corus for genuinely long research more than we modeled, and they want to trust it more — the “was this verified?” question came up constantly. Both are now product work: the first is capacity and limits; the second is our honesty work, which is the direction the whole family is moving.

Corus is out of preview. The limits are fixed, the report is out, and the model is still free. That last sentence is the one we most want to keep true.

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