The `history-substring-search-up` and `history-substring-search-down` widgets are not bound by default. You'll probably want to add them to `ZSH_AUTOSUGGEST_CLEAR_WIDGETS` so that the suggestion will be cleared when you start searching through history:
```sh
# Add history-substring-search-* widgets to list of widgets that clear the autosuggestion
If you have a problem, please search through [the list of issues on GitHub](https://github.com/zsh-users/zsh-autosuggestions/issues) to see if someone else has already reported it.