How do I stop internal system messages from showing in chat

Most internal or tool messages only appear when verbose or reasoning is enabled for that session.
Fix in the chat where you see it:
/verbose off
/reasoning off
If it is still noisy, check the session settings in the Control UI and set verbose to inherit. Also confirm you are not using a bot profile with verboseDefault set to on in config.
Docs: Thinking and verbose, Security.