Chat Completions: not dead yet
OpenAI said it will continue to support Chat Completions, its most widely adopted API, and add new models to it, even though it is now subsumed within the Responses API. If developers don’t use built-in tools they can continue to use the Chat Completions API, but if they require built-in tools, especially for newer integrations, the Responses API should be the preferred choice, the company said.
As for the Assistants API, OpenAI’s plan is to include every tool and feature into it along with the Responses API, before phasing it out in mid-2026. When it formally announces the API’s deprecation, it said, it “will provide a clear migration guide from the Assistants API to the Responses API that allows developers to preserve all their data and migrate their applications.”
What is OpenAI’s Agents SDK?
The open source Agents software development kit (SDK) is an upgraded version of Swarm, an experimental SDK that OpenAI released last year to help developers orchestrate agentic workflows. Despite Swarm’s experimental status, OpenAI said several enterprises have already adopted it.