I never use the sidebar in macOS Safari and always keep it closed. However, since I updated to Safari 18 on macOS 14.7, I've been seeing new Safari windows open with the sidebar open. This is driving me crazy! It doesn't happen every time, though. It's seemingly random, which makes the issue extremely difficult to diagnose. It frequently happens when I open a URL from another app, such as Mail, Mona, or my own Link Unshortener.
In Safari General Settings, Safari opens with a new private window, new windows open with an empty page, and new tabs open with an empty Page.
Is anyone else seeing this issue? If so, please let me know via Mastodon or email. I want to get this on Apple's radar, without actually using Apple's Radar, which is a black hole.