OpenAI Assistants API shuts down August 26 — 75 days to migrate to the Responses API

OpenAI's Assistants API — /v1/assistants, /v1/threads, and all related endpoints — goes permanently offline on August 26, 2026. That's approximately 75 days from today. OpenAI has stated explicitly that there is no extension option, and Azure OpenAI retires it on the same date.

Why the deadline is hard. The deprecation notice went out August 26, 2025, giving teams one full year of runway. The Responses API has been stable since March 2025, and OpenAI has progressively ported Assistants capabilities — threads, file search, code interpreter — into it over the past year. Teams that haven't started migrating are now in the final quarter of that window.

The migration shape. The Responses API uses a simpler input/output model: send input items, get output items back, without the stateful Thread and Run management overhead. For persistent conversation context, the Conversations API covers that pattern. OpenAI provides a migration guide with conceptual mapping and code samples.

What the Responses API adds that makes migration worth doing, not just required. Native MCP tool calls — call any MCP server directly without custom tool definitions. Built-in deep research capability. Structured outputs with json_schema. Improved streaming performance. computer_use_preview. None of these are available in the Assistants path; staying on the old API means staying without them.

Audit checklist. Search your codebase for: /v1/assistants, /v1/threads, AssistantEventHandler, client.beta.assistants, openai.AssistantFile. Each hit is a migration scope item. Azure OpenAI teams: same August 26 date, no separate extension.

Sources: OpenAI community: Assistants API deprecation, OpenAI migration guide, Syntackle: migration overview, ClonePartner: step-by-step guide