`navigator.webdriver` afaik, but I think there's a couple more, I did some research on it a few months ago. If using Playwright/Puppeteer, they also have a few special things injected that you have to strip.
Ah right, there are stealth plugins to remediate these types of hints I believe.
What model did you use to build this? I recently looked in to building something similar and got refusals.
I built the POC by hand (just had like 3 things it could do: scroll, click, type), and then Codex used my established patterns to make it slightly more general and cleaned it up.