What is OpenAI GPT-4.5 Turbo?
"GPT-4.5 Turbo" was a name used in late 2023 speculation and leaked documentation about OpenAI's next model release. Rumors suggested it would carry a knowledge cutoff into April 2023 (versus GPT-4's September 2021 cutoff) and an expanded 256k token context window, large enough to process several hundred pages of text in a single prompt. These rumors were never confirmed by OpenAI, and no model was ever released under the "GPT-4.5 Turbo" name. When OpenAI's next major model arrived in 2024, it was released as GPT-4o ("Omni"), with a different feature set than what had been rumored.
What features were rumored for GPT-4.5 Turbo?
Speculation at the time pointed to several possible improvements over GPT-4:
- Updated knowledge base — a training cutoff extending into April 2023.
- Larger context window — a rumored 256k token limit, far beyond GPT-4's original 8,192 tokens.
- Lower cost — expectations that input and output tokens would be priced below GPT-4 rates.
- Multimodal capabilities — speculation about image generation and text-to-speech support.
- Customizable chatbots — expectations around user-configurable assistant personas.
None of these specifications were ever confirmed for a model called "GPT-4.5 Turbo." Some of these directions did surface in models OpenAI actually shipped, including GPT-4 Turbo and GPT-4o.
Why did GPT-4.5 Turbo never materialize?
OpenAI never issued an official announcement, API preview, or release confirming a model named GPT-4.5 Turbo. The name appears to have originated from unverified sources and community speculation rather than an OpenAI statement. Instead, OpenAI's subsequent major release was GPT-4o, which introduced native multimodal input across text, audio, and images.
Historical Klu benchmark snapshot (November 2023)
In early exploratory evaluations conducted by Klu on 60k–256k input tokens dealing with pre-release 1106 snapshots (then referred to colloquially in leaks as GPT-4.5 Turbo / 1106-preview), Klu evaluated fact retrieval across context depths without intermediate libraries:
Historical context: This evaluation tested pre-release 1106 snapshots before OpenAI officially standardized on the GPT-4 Turbo and GPT-4o naming conventions.
How can developers access GPT-4o today?
Since GPT-4.5 Turbo was never released, there is nothing to access under that name. Existing workloads built on GPT-4o can continue passing gpt-4o as the model name in API requests. For new projects, consult OpenAI's official current model guidance to choose the right model.