Could you let me know what the character limit is for OpenAI instructions?

Hi everyone,

I’ve been working with OpenAI’s custom instructions feature and had a quick question I couldn’t find a clear answer to:

What is the exact character (or token) limit for the instruction fields (e.g., “How would you like ChatGPT to respond?”)?

I tried inputting detailed prompts, but I’m not sure where the cut-off is or if there’s a recommended maximum length for optimal performance. If anyone has official documentation or personal experience with this, I’d really appreciate your insight.

Thanks in advance!

스크린샷 2025-04-23 114052

maybe 256,000 characters. here is documentation link.

https://platform.openai.com/docs/api-reference/assistants/modifyAssistant