OpenAI has begun rolling out its newest AI model, GPT-4.5, to users on its ChatGPT Plus tier.

In a series of posts on X, OpenAI said that the rollout will take “1-3 days,” and that it expects rate limits to change. GPT-4.5 launched first for subscribers to OpenAI’s $200-a-month ChatGPT Pro plan last week.

“We’d like to give everyone with access to GPT-4.5 a sizable rate limit, but we expect rate limits to change as we learn more about demand,” the company wrote in a post.

GPT-4.5 is OpenAI’s largest AI model yet, trained using more computing power and data than any of the company’s previous releases. But it’s not necessarily OpenAI’s best. On several AI benchmarks, GPT-4.5 falls short of newer AI “reasoning” models from Chinese AI company DeepSeek, Anthropic, and OpenAI itself.

GPT-4.5 is also very expensive to run, OpenAI admits — so expensive that the company says it’s evaluating whether to continue serving GPT-4.5 in its API in the long term. Perhaps as a result, GPT-4.5 is far and away OpenAI’s priciest model in its API. The company is charging $75 per million tokens (~750,000 words) fed into the model and $150 per million tokens generated by the model, which is 30x the input cost and 15x the output cost of OpenAI’s workhorse GPT-4o model.

All that being said, OpenAI claims that GPT-4.5’s increased size has given it “a deeper world knowledge” and “higher emotional intelligence.” GPT-4.5 hallucinates less frequently than most models, as well, according to OpenAI — which in theory means it should be less likely to make stuff up.

GPT-4.5 is also very persuasive. One of OpenAI’s internal benchmarks found that the model is particularly good at convincing another AI to give it cash.