OpenAI introduced [GPT 4.5](https://openai.com/index/introducing-gpt-4-5/). It's not clear yet what the tokenizer used for it is but when that's known, updates need to be made to TikToken Tokenizer. [System Card](https://cdn.openai.com/gpt-4-5-system-card.pdf) Related to issue: openai/tiktoken#385