OpenAI raised ChatGPT custom instructions from 1,500 to 5,000 characters.

Release notes also cover ChatGPT Work, powered by GPT-5.6, which pulls context from a team's connected tools. The character limit is the quietly significant one. 1,500 characters is a summary. 5,000 is roughly where a persistent instruction block can carry real style specifications and hard constraints rather than gestures at them. If you've been trimming your custom instructions to fit, go rewrite them at full length. And then read the CLAUDE.md length finding below before you fill all 5,000.