The request
“Subject Header.” — short ask, clear need. It also showed up in the feature megathread. Default dated subjects were fine for some people and wrong for others who wanted a personal cue in the inbox.
What shipped
On August 28, 2025 you could customize the email subject when composing a capsule.
Follow-up questions
Comments asked about editing subjects on already-sent capsules and about how much schedule metadata appears in the delivered mail. Those are adjacent product decisions; the core ship was giving composers control at send time.