On August 26, 2026 OpenAI turns off the Assistants API. /v1/assistants, /v1/threads, and /v1/threads/runs start returning errors that day. There's no grace period and no degraded mode, and OpenAI has said it won't ship a migration tool. Threads don't move over automatically either, so any conversation state you kept server-side is something you have to plan around, not port with a flag.
If your code still calls openai.beta.assistants or openai.beta.threads, this is the migration. Here's the mapping, the code changes, and how to make sure you didn't miss a call-site.
The concept swap
The new surface is the Responses API plus Conversations. Four things get renamed and, in one case, genuinely rethought:
Assistants API
