GPT-4.5 Dies in 4 Days, o3 Next — and Claude Opus 4.8 Just Became the King of AI

June 23, 2026 — If you're still using GPT-4.5 in ChatGPT, you've got exactly 4 days left. OpenAI pulled the trigger on one of the most aggressive model retirements in its history, confirming GPT-4.5 will vanish from ChatGPT on June 27, 2026 after a 30-day sunset period. The reasoning powerhouse o3 follows on August 26.

The chapter that changed AI is officially closing.

The Retirement Rundown

OpenAI's model release notes quietly updated to show:

• GPT-4.5 → Retired June 27 (this Saturday). No more ChatGPT access.
• OpenAI o3 → Retired August 26 (90-day sunset).
• GPT-4o → Already retired for most users in April.
• GPT-5.5 Instant → Already the default replacement — faster, cheaper, better.

The message is clear: OpenAI is clearing the decks ahead of what many suspect is an IPO push and the rollout of whatever comes after GPT-5.5.

Meanwhile, the Crown Has a New Owner

While OpenAI retires its legends, the leaderboard war just flipped. Claude Opus 4.8 from Anthropic hit 61.4 on the Artificial Analysis Intelligence Index on May 28 — the first model ever to break 60 — and took the global #1 spot.

On SWE-Bench, Claude Opus 4.8 scores 88.6% vs GPT-5.5's 82.6%. On the LMSys-style composite index, Claude Fable 5 still leads at 100/100 across 357 models. Anthropic is executing ruthlessly.

The rankings as of June 2026:

Model	Score	Strength
Claude Opus 4.8	61.4 (AAII) 🔥	Coding, reasoning
Claude Fable 5	100/100 (LMSys)	General chat
GPT-5.5 Instant	82.6% (SWE-Bench)	Speed, API
Gemini 3.2 Pro	Top 3	Multimodal
Nemotron 3 Ultra	Best open-weight	Open source

What This Means

OpenAI retiring GPT-4.5 and o3 in the same breath isn't just housekeeping — it's a strategy shift. GPT-5.5 Instant is the new workhorse, and whatever is cooking (GPT-6? Orion?) will inherit the throne.

But for now, the crown belongs to Anthropic. Claude Opus 4.8 is the smartest model money can buy — and it's not particularly close.

The AI era has a new king. Long live the king.

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Tags: ai, machinelearning, llm, anthropic

Cover: AI concept art generated with GPT-Image-2