[iamnbutler]

• ace serve now records its port in $ACE_HOME/host.port, and refuses to start while another host still answers on that port with the same home. The refusal names that host, its PID and its command. A stale file, or a port now held by a different home, doesn't block.
• With this home's host running, ace archive, unarchive, delete and kill go through its gateway, like the app, so the channel's terminals close. Without a running host they act on the catalog directly, as before.

Map: ^891, ^776 (ace-map).

Smoke-tested from this lane on loopback hosts with their own home:

• A host on 4443, then ace serve --port 4444 on the same home: refused with "… is already served by a command-line Ace host (PID …) on port 4443".
• With sleep running in a terminal in each of three channels, ace archive, ace kill and ace delete each ended their own channel's shell. ace unarchive worked too.
• With the host stopped, ace archive still archived. Restarts on 4443 and then 4444 over the stale host.port both started.

Built in Ace

No: Claude Code (the ace2-90 fix-train session) wrote and smoke-tested this through headless hosts, Playwright and the CLI. See #5.