OpenAI will remove o3 from ChatGPT on August 26 — do not confuse that with an API shutdown

Key facts: OpenAI will retire o3 from ChatGPT on August 26, 2026. That is 11 days from today. The company says the change applies to ChatGPT only: there is no announced API change. OpenAI’s current model documentation still lists o3 as an API model, while describing it as a reasoning model succeeded by GPT-5.

What is changing on August 26

OpenAI announced the o3 retirement on May 28 as part of its ChatGPT model cleanup. GPT-4.5 already left ChatGPT on June 27; o3 is the remaining scheduled removal. The notice describes a 90-day sunset and names August 26 as the endpoint. (Source: OpenAI Model Release Notes, updated 2026-08-13.)

The scope matters. The release notes say, “These changes apply to ChatGPT only; there are no changes to the API.” That means a production integration that calls o3 through the API is not being switched off by this announcement. Do not schedule an API migration solely because a ChatGPT model-picker option disappears. (Source: OpenAI ChatGPT Release Notes.)

What to do if your team uses o3 in ChatGPT

1. Preserve the workflows, not the old chats. Before August 26, save the system instructions, reference prompts, files, and evaluation examples behind any o3 workflow that people use repeatedly. A chat export is less useful than a repeatable test case.

2. Re-run the important work in GPT-5.6. OpenAI’s model documentation labels o3 a previous reasoning model and points to GPT-5 as its successor. For a ChatGPT workflow, use GPT-5.6 with a comparable reasoning setting, then compare output format, tool behavior, and factual claims against the saved examples. (Source: OpenAI Models documentation.)

3. Keep API and ChatGPT testing separate. A successful prompt in ChatGPT does not prove a production API migration. The ChatGPT retirement is a product-surface change; model IDs, rate limits, and API availability have their own release notes. Pin snapshots and run your API regression set before making a production change.

4. Do not present the removal as an outage. ChatGPT users who selected o3 need a replacement plan. API builders need to monitor the platform’s deprecation notices, but this notice is not one. Mixing those two messages creates avoidable emergency work.

Sources

• OpenAI Model Release Notes — Retiring OpenAI o3 and GPT-4.5
• OpenAI ChatGPT Release Notes
• OpenAI Models documentation

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