The OpenAI Assistants API Is Gone: Your Threads Are Already Broken

TL;DR: The OpenAI Assistants API shut down on August 26; any production code still calling it returns errors. The migration is manual — Responses API for generation, Conversations API for persistent history.

The Assistants API — OpenAI's first official framework for building thread-based agents — went offline on August 26, one year after its deprecation notice. If your code creates Assistants, creates Threads, or polls runs, it is broken now.

What you must do:

• Rebuild Assistants as stateless Responses API calls. OpenAI provides no automated conversion tool.
• Recreate chat history in the Conversations API; Thread data does NOT migrate automatically and must be ported by hand or abandoned.
• Vector stores and files uploaded via the Files API do persist into the new file search tool — only Thread and Assistant objects require manual migration.

The new architecture is stateless: the Responses API is a request/response call with tool support, closer in structure to the Anthropic SDK than the old run-polling loop. For most apps built on the Assistants API, this is a rewrite, not a swap.

Why it matters: If you have production code, an internal tool, or a CI script that uses the Assistants API, it is returning errors to users right now. The migration guide is the only path forward.

Sources: Assistants migration guide — OpenAI · Assistants deprecation community thread · OpenAI API changelog — August 26 shutdown entry