Updated 23 Aug 2026: Preserves one useful factual gap from duplicate dossier #37: Assistants-era object retention/deletion semantics differ from Responses/Conversations state. Adds only a retention section, one key detail, one builder takeaway, and OpenAI's primary data-controls source; all existing shutdown/migration framing is otherwise preserved.
Key details
- OpenAI will remove the Assistants API on August 26, 2026.
- Developers were notified of the deprecation on August 26, 2025.
- OpenAI recommends the Responses API and Conversations API as replacements.
- Assistants map to Prompts, Threads to Conversations, Runs to Responses and Run Steps to Items.
- OpenAI says the Responses API has reached feature parity with Assistants and is the forward path for agent development.
- The migration changes state and execution concepts, not just endpoint names.
- Retention does not map one-to-one: undeleted Assistants-related objects can persist indefinitely, stored Responses state has a 30-day default retention period, and Conversations/items are retained until deleted.
What builders should take away
- Search production code, queues, cron jobs and background workers for Assistants API usage now; do not assume the only dependency is in the interactive app path.
- Create a migration matrix for Assistants→Prompts, Threads→Conversations and Runs→Responses so application-owned IDs and database relationships are deliberately remapped rather than improvised during deployment.
- Run end-to-end tests for tool calls, retries, streaming, file search and conversation persistence. A response that 'works' in a simple prompt test is not enough evidence that an agent workflow is equivalent.
- Ship the migration behind a feature flag or traffic split if the product is business-critical, then compare outputs and error rates before fully removing the Assistants path.
- Remove or quarantine code that silently falls back to Assistants after August 26; a dead fallback can mask migration defects during testing and then fail at the deadline.
- Review retention and deletion behavior for both Responses and Conversations during migration, especially if your product promises specific privacy, compliance or data-lifecycle guarantees.
What changed
OpenAI's Assistants API is scheduled to shut down on August 26, 2026, exactly one year after developers were notified of the deprecation. OpenAI directs developers to replace Assistants with Prompts, Threads with Conversations, Runs with Responses and Run Steps with generalized Items. The migration path also changes how applications manage state and tool-calling loops.
Why it matters
This is no longer a future deprecation: the shutdown is eleven days away as of August 15, 2026. Any production SaaS, internal tool or agent workflow that still depends on the Assistants API risks hard failure if it is not migrated in time. 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.
The deadline is fixed
OpenAI's deprecations page lists August 26, 2026 as the removal date for the Assistants API, with the Responses API and Conversations API as the recommended replacement. OpenAI originally notified developers on August 26, 2025.
The object model changes
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.
Retention semantics need a separate migration check
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.
The replacement API is also where newer capabilities live
OpenAI positions Responses as its forward path for agent development and documents access to newer capabilities such as MCP, computer use and deep research there. That makes the migration both a shutdown requirement and a platform-direction change: staying on Assistants means staying on an interface that will simply disappear.
Migration needs production-level validation
Teams should inventory every place an Assistant, Thread, Run or Run Step is 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.
What to watch next
- Whether OpenAI publishes any last-minute migration caveats or deadline changes before August 26.
- Operational reports from developers moving long-lived Threads and tool-heavy agents to Conversations and Responses.
- Whether any Assistants features behave differently enough after migration to require product-level changes rather than API-only changes.
Still unclear
- OpenAI's documentation says Responses has reached feature parity, but feature parity does not guarantee identical behaviour for every production workflow, particularly where applications depend on Assistants-specific orchestration assumptions.
Sources
Direct reading behind this dossier.
Deprecations | OpenAI API
OpenAI
primary
Official deprecation schedule listing the August 26, 2026 Assistants API shutdown and recommended replacements.
Assistants migration guide | OpenAI API
OpenAI
primary
Official mapping from Assistants, Threads, Runs and Run Steps to Prompts, Conversations, Responses and Items.
Data controls in the OpenAI platform
OpenAI API
primary
Current primary documentation for regional-processing examples, support matrix, eligibility, retention controls, scope and regional-processing pricing.