GPT-4o Is Officially Retired: The Complete Developer Migration Guide (April 2026)

GPT-4o is gone. As of March 31, 2026, OpenAI shut down GPT-4o API access entirely — and the final Enterprise and Business Custom GPT access terminates on April 3, 2026. That is today. If your production code is still calling gpt-4o-2024-08-06 or chat...