neowin[.]net/news/mozilla-under-fire-for-firefox-ai-bloat-that-blows-up-cpu-and-drains-battery/
tomshardware[.]com/tech-industry/artificial-intelligence/new-local-ai-integration-into-firefox-spurs-complaints-of-cpu-going-nuts-chip-and-power-spikes-plague-new-version-141-x
You may or may not see it as Mozilla's doing a progressive rollout per Tom's. The new AI-enhanced tab groups feature uses local AI, and hits device performance HARD according to reports.
To turn it off open a new tab and enter about:config . Accept the risk warning, and enter browser.ml.chat.enabled in the search box. Turn the feature off. Next, search for browser.tabs.groups.smart.enabled and turn it off.
Per Neowin:
You can also hide the chatbot from the sidebar in Settings or Firefox Labs, but it might pop back up after updates.