OpenAI retired GPT-4.5 in ChatGPT, including custom GPTs, with existing conversations continuing on GPT-5.5.

The migration path is inside ChatGPT: old GPT-4.5 conversations continue on GPT-5.5, while API access is unchanged.

This sits next to the prior retirement notice and only changes ChatGPT, not API builds on OpenAI.

• Jun 27, 2026OpenAI modelcard diff removed API docs navigation content.
• Jun 27, 2026Anthropic removed model-card text covering Claude Fable 5 and Claude Mythos 5.
• Jun 26, 2026Anthropic modelcard removed model overview content for Claude Fable 5 and Mythos 5

This is the world we build in. It moves this fast. We move with it.