On 6 October 2025, OpenAI unveiled Agent Builder at DevDay. A visual canvas where you drag boxes together and get an agent out the other end. Eight months later, on 3 June 2026, it was deprecated. It shuts down for good on 30 November 2026.
Nobody did anything wrong there. OpenAI decided the visual builder was not the path and pointed users at the Agents SDK instead. But if you built your order processing on that canvas in January, you spent the summer migrating instead of shipping. That is the part of the "how do I build an AI agent" question that almost nobody asks about in advance, and it is usually the part that decides whether the thing is still running in two years.
There are four honest routes to a working agent. They differ less in what they can do than in where they break. Here is what each one actually costs, where its ceiling sits, and which kind of company each one fits.
The Decision You Are Actually Making
Most comparisons start with features. That is the wrong end. Every platform on this list can call an API, read a document and write to a CRM. Feature lists converged eighteen months ago.
