The new owner's plan is...to sunset the paid product immediately and give customers access to tooling to be able to continue generating SDKs on their own. From Stainless's post:

    As we focus on Claude Platform capabilities and connecting agents to APIs, we’ll be winding down all hosted Stainless products, including our SDK generator. Starting today, new signups, projects, and SDKs will not be available.

    If you’re a Stainless customer, visit app.stainless.com/transition for help transitioning from Stainless-managed products to other options. As always, you own the SDKs you’ve generated to date, and have full rights to modify and extend them however you wish.