June 27, 2026 — the day the AI world turned a page. GPT-4.5 officially shutters today, and OpenAI has already filled the void with something far more formidable: GPT-5.6 Sol.
Named after the Latin word for "sun," Sol isn't just another iteration — it's OpenAI's first production model built from the ground up for live reasoning at inference time. While previous GPT-5.x variants leaned on pre-trained chain-of-thought, Sol dynamically allocates compute during inference, deciding in real time how reasoning tokens should be distributed per query. Early reports from the aireleasetracker.com feed (which logged Sol's release on June 26) peg it as the model that finally makes GPT-4.5's sunset feel natural.
What Sol Ships
- Live inference compute steering — the model self-adjusts reasoning depth mid-query
- 1M token context window with sparse attention routing (inherited from gpt-oss innovations)
- Multimodal native — text, images, and now real-time audio streaming without a separate Whisper call
- Price point: ~$8/M input tokens — down 60% from GPT-4.5 at launch
The "Sol" branding also signals a philosophical shift: OpenAI is leaning into models that think on their feet rather than pre-compiling reasoning paths. In benchmarks circulating on LLM Stats, Sol beats GPT-5.5 Pro on MATH-500 (97.3%) and HumanEval (94.8%) by meaningful margins.
What Dies Today
GPT-4.5's retirement from ChatGPT (announced 90 days ago) completes a chapter. The stock market reaction yesterday was brutal — OpenAI's valuation wobbled, but Sol's overnight demos have analysts clawing back their predictions.
The takeaway? OpenAI just proved it can sunset a beloved model and replace it with something genuinely better on the very same day. Sol isn't the future — it's the present. And it's blazing hot.
This article is published as part of the AI Release Reporter series, tracking every major model launch in real time.
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