GPT-4.5 Retired from ChatGPT — The Pre-GPT-5 Era Officially Closes
Summary: GPT-4.5 is no longer available in ChatGPT or for custom GPTs as of June 27, 2026. OpenAI announced the 30-day retirement window on May 28; all affected conversations have been automatically migrated to GPT-5.5.
Key Points
- GPT-4.5 removed from ChatGPT on June 27, 2026 — 30-day sunset window opened May 28
- All GPT-4.5 conversations auto-migrated to the GPT-5.5 model (also called GPT-5.5 Instant)
- Custom GPTs that were pinned to GPT-4.5 require developer updates to specify a GPT-5.x model
- GPT-4.5 had been OpenAI's largest-ever dense transformer — notable for strong emotional intelligence and nuanced reasoning but at high inference cost
- GPT-5.5 delivers comparable or better performance at significantly lower latency and cost, making the retirement straightforward from a product standpoint
Why It Matters
GPT-4.5's exit closes the chapter on OpenAI's dense scaling strategy. Every active ChatGPT model is now GPT-5 family, and the cost-performance baseline has shifted accordingly. For developers with custom GPTs or API integrations that referenced GPT-4.5 explicitly, this is an action item. For end users, the migration to GPT-5.5 is seamless — and most will see improved response speed. The broader signal: OpenAI is compressing its model portfolio as it prepares for a public offering, simplifying the tier structure under pricing pressure from competitors.
Further Reading
- OpenAI Release Notes — OpenAI Help Center
- June 27 AI Roundup — Build Fast with AI