OpenAI debuts GPT-4.5, its biggest model yet

Axios

03-03-2025

OpenAI on Thursday released an early version of GPT-4.5, a significant update to the large language model underlying ChatGPT that OpenAI says will be better at recognizing patterns and drawing connections.
Why it matters: The release marks the next evolution of OpenAI's flagship model lineage that has been an industry front-runner since the start of the generative-AI boom.
Driving the news: This is OpenAI's largest model yet — though the company declined to offer details about its size or the computing resources it took to train it.
GPT-4.5 should hallucinate less, follow instructions better and deliver interactions that feel more natural.
The "research preview" version of GPT 4.5 that was released Thursday supports real-time search and image and file uploads but not voice mode, video or screen sharing.
GPT-4.5 will be made available starting today for subscribers of the $200-per-month ChatGPT Pro and next week for other paid subscribers, including the $20-per-month ChatGPT Plus service. It's also being made available to those who pay to use OpenAI's API.
Yes, but: OpenAI noted that because it is a larger model, GPT-4.5 is more expensive to deliver.
"GPT‑4.5 is a very large and compute-intensive model, making it more expensive⁠ than and not a replacement for GPT‑4o," it said.
What they're saying: OpenAI CEO Sam Altman wrote in a post on X, "Good news: it is the first model that feels like talking to a thoughtful person to me... this isn't a reasoning model and won't crush benchmarks. It's a different kind of intelligence and there's a magic to it I haven't felt before."
Between the lines: Until last year, much of the progress in large language models came from increasing the size of the underlying model and the amount of data used to train it.
But that approach, known as "unsupervised learning" or "pretraining," has begun to offer diminishing returns. So the focus has switched to "reasoning" — that is, letting models take more time and use more computing resources at the time of a query to deliver a better answer.
GPT-4.5 represents OpenAI's first major move in some time at improving its AI using the former approach, scaling up the pretraining phase.
OpenAI says the result is that GPT-4.5 has more and broader world knowledge and should have increased reliability.
What they're saying: "We're sharing GPT‑4.5 as a research preview to better understand its strengths and limitations," OpenAI said in a blog post. "We're still exploring what it's capable of and are eager to see how people use it in ways we might not have expected."
What's next: OpenAI hinted it will add reasoning improvements on top of GPT-4.5.
The company's "roadmap" announcement earlier this month, pointing the way toward the eventual release of GPT-5, called 4.5 "our last non-chain-of-thought model."
"We believe reasoning will be a core capability of future models, and that the two approaches to scaling — pre-training and reasoning — will complement each other," OpenAI said. "As models like GPT‑4.5 become smarter and more knowledgeable through pre-training, they will serve as an even stronger foundation for reasoning and tool-using agents."