OpenAI's Late-2026 API Deprecation Calendar: What Breaks and When

If any part of your stack calls OpenAI's Assistants API, the clock is short. It is being removed from the API entirely on August 26, 2026, according to OpenAI's official API deprecations page. Anything still routing through it after that date stops working, not degrades gracefully, stops.

Two more dates worth marking on the same calendar. Older GPT-5 and o3 model snapshots are being removed on December 11, 2026, which affects anyone who pinned a specific model version rather than pointing at a rolling alias, a common practice for teams that wanted reproducible behavior and are now facing a forced migration. And the Sora video-generation API specifically, separate from the consumer Sora app's earlier shutdown, is being discontinued September 24, 2026.

None of these are surprise cuts. OpenAI's deprecations page is live-updated and lists them with lead time. The risk is not that OpenAI is being opaque about the schedule, it is that teams treat a working integration as a solved problem and stop checking the deprecations page after initial launch, then find out about a removal when a production call starts failing rather than weeks earlier when there was time to migrate calmly.

If you have anything built on the Assistants API, that migration needs to start now, not in late August. If you're pinned to a specific GPT-5 or o3 snapshot, December gives more runway, but pinned versions have a way of getting forgotten until they break. And if Sora's API is part of a product pipeline, September 24 is the date that pipeline needs an alternative in place by.