First party cookies "disappearing"

I'm seeing my first party cookies "disappear" on a couple of sites right now, prematurely logging me out:

• https://news.ycombinator.com
• a lemmy instance (https://infosec.pub if it matters)

I'm not running any extensions. I'm not clearing anything on purpose. Single (default) profile.

Normal settings on each site are enabled:

My cookies to not magically disappear.

0.99.126-rc (WebKit 618.1.2)

Sonoma (14)