OpenAI shuts down Assistants API, pushes Responses-based agents

OpenAI officially retired the Assistants API on August 26, 2026. Developers must move from managed persistent threads to the stateless Responses and Conversations APIs, with file_search and vector stores as the new RAG path.

• Assistants API was shut down on August 26, 2026
• Persistent threads replaced by Conversations API
• file_search with vector stores is the new RAG tool
• No automatic migration for old threads