OpenAI Assistants API
OpenAI's stateful agent API, shut down on 26 August 2026
Overview
The Assistants API was OpenAI's managed agent interface, with persistent threads, a code interpreter, file retrieval and function calling. OpenAI gave a year's notice in August 2025 and shut it down on 26 August 2026. Its replacement is the Responses API with the Conversations API, and the Azure OpenAI version was retired in favour of Microsoft Foundry Agents.
Pricing
Pricing shown for reference only. These figures reflect RECATOOLS research as of 14 Oct 2026 and may be out of date or incomplete. This is not financial or purchasing advice — always confirm the current price on the provider’s official website before making any decision.
Use cases
What you can produce with OpenAI Assistants API
- A dated record of the API's shutdown on 26 August 2026, after notice given on 26 August 2025
- OpenAI's migration map: assistants to prompts, threads to conversations, runs to responses, run steps to items
- A pointer to the Responses API and Conversations API as the official replacements
- A pointer to Microsoft Foundry Agents for Azure OpenAI Assistants users
- A summary of what the API offered: managed threads, code interpreter, file retrieval and function calling
The Assistants API is gone. OpenAI shut it down on 26 August 2026 after a year's notice, and its old endpoints no longer answer. In its day it was a quick way to ship a stateful assistant, because threads, retrieval and a code interpreter came managed.
Anyone still holding code against it should follow OpenAI's migration guide to the Responses and Conversations APIs, and Azure customers should move to Microsoft Foundry Agents. Expect real rework: prompts live in the dashboard and your own code now runs the tool loop. This page is kept as a dated status record.
What we found
The Assistants API was OpenAI's first managed agent interface. It appeared in OpenAI's API changelog on 6 November 2023, alongside GPT-4 Turbo and DALL·E 3 in the API, and bundled persistent threads, a code interpreter, file retrieval and function calling, so a developer could build a stateful assistant without writing their own session store or vector search. A v2 beta followed in April 2024, and the v1 beta was switched off on 18 December 2024.
Its replacement was signalled early. When OpenAI released the Responses API in March 2025, its changelog said every Assistants feature would move there, with a sunset expected in 2026. The Conversations API, for long-running state, arrived in August 2025, and on 26 August 2025 OpenAI's deprecations page gave developers a year's notice. The API shut down on 26 August 2026. OpenAI's migration guide now opens by saying it is no longer available. When we probed it on 14 October 2026, the old /v1/assistants and /v1/threads routes returned "not found" rather than asking for a key, which suggests they were removed rather than locked.
Moving off it is a re-architecture, not a renamed endpoint. OpenAI maps assistants to prompts, threads to conversations, runs to responses and run steps to items. Prompts can only be created in the dashboard, and the application code now owns the tool-calling loop, history pruning and retries that runs used to manage. Teams with history stored in threads have data to move as well as code to rewrite.
Microsoft followed the same path. Its documentation for the Azure OpenAI version now says the Assistants API is retired and points customers to the Microsoft Foundry Agents service, so Azure did not extend the old interface beyond OpenAI's date.
Nothing here can be bought or called any more. This page stays as a dated record of what the API did, when it ended and where its users were sent.
Compiled by RECATOOLS from public sources: vendor documentation and pricing, code repositories and published reporting.
About this listing
This entry was compiled from publicly available data including OpenAI Assistants API's official website, press releases, documentation, and reputable third-party publications. RECATOOLS is not affiliated with OpenAI Assistants API unless explicitly stated.
Third-party AI tools update their pricing, features, availability, and policies frequently. Information here may be outdated by the time you read this — we make reasonable efforts to keep listings current, but cannot guarantee absolute accuracy.
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