OpenAI’s Assistants API has shut down

OpenAI’s Assistants API reached its scheduled shutdown on August 26, 2026, exactly one year after developers were notified of the deprecation. OpenAI’s deprecation policy defines shutdown or sunset as the point when a model or endpoint is no longer accessible, and its current deprecations table lists the Assistants API removal date as August 26 with Responses and Conversations as the recommended replacements. The migration path replaces Assistants with Prompts, Threads with Conversations, Runs with Responses and Run Steps with generalized Items, while also changing how applications manage state and tool-calling loops.

This is now an operational failure boundary rather than a future deadline. Any production SaaS, internal tool or agent workflow that still depends on Assistants endpoints must migrate rather than plan to migrate. The replacement is not purely a renamed endpoint; state management and execution concepts differ enough that teams should test behavioural equivalence, tool calls and persistence rather than treating the change as a mechanical URL swap.

OpenAI’s deprecations page lists August 26, 2026 as the removal date for the Assistants API and defines shutdown or sunset as the point when the endpoint is no longer accessible. Responses API and Conversations API remain the recommended replacements.

The migration guide maps Assistants to Prompts, Threads to Conversations, Runs to Responses and Run Steps to Items. Responses accept input items and return output items; Conversations hold state across interactions. Tool-call loops are managed explicitly, so applications that relied on Run semantics need to re-check their orchestration logic.

OpenAI's current data-controls documentation says Assistants-related objects such as Assistants, Threads, Messages, Runs and Vector Stores retain application state until deleted; objects related to the Assistants API are removed from OpenAI's servers 30 days after deletion, while undeleted objects can remain indefinitely. Responses application state has a 30-day retention period by default when stored, while Conversations and conversation items are retained until deleted. Teams with privacy, compliance or contractual data-lifecycle promises should therefore verify deletion and retention behavior explicitly rather than assuming the replacement APIs inherit Assistants semantics.

OpenAI positions Responses as its forward path for agent development and documents access to capabilities such as MCP, computer use and deep research there. With Assistants retired, the strategic direction and the operational requirement now point to the same API family.

Teams should inventory every place an Assistant, Thread, Run or Run Step was created or read, then test persistence, retries, streaming, tool execution and file-search behaviour under the replacement APIs. The highest-risk integrations are those where Assistants state is deeply coupled to application-level user or job records.