GPT-4.5 is no longer available in ChatGPT, including for custom GPTs.

Builders using custom GPTs need to move ChatGPT work off GPT-4.5 while API usage stays unchanged.

This is a ChatGPT-only retirement: existing GPT-4.5 conversations continue with GPT-5.5, and API behavior does not change.

• Aug 05, 2026OpenAI removed model selection copy naming GPT-5.6 Sol, Terra, and Luna.
• Aug 05, 2026Anthropic removed model card copy for Claude Fable 5 and Claude Mythos 5.
• Aug 05, 2026Google pricing page removed Gemini model navigation and Interactions API availability note

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