Shared-home CLI reproduction | AFTER
Linux x86_64; built CLI; fresh synthetic HOME; no copied database.
Host A: isolated PID + network + UTS namespaces; hostname evidence-host-a.
Host B: normal PID/network namespace; same home files.
Server A is live; recorded PID=1, port=39555, hostname=evidence-host-a.
Local PID 1 exists; server A loopback is unreachable from host B.

$ t3 pair --base-dir "$HOME/.t3"
[21:51:06.891] ERROR (#2): ServerOnOtherMachineError: The T3 Code server recorded in $HOME/.t3/userdata/server-runtime.json runs on evidence-host-a, which shares this T3 home.
Run `t3 pair` on evidence-host-a, or start a server on this machine with a separate T3 home (--base-dir).
    at file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:9273:46
    at pair.discoverPairTarget (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:9408:24)
    at pair.discoverPairTarget (definition) (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:9247:28)
[exit 1]

$ t3 serve --base-dir "$HOME/.t3" --port 39556
[21:51:07.546] ERROR (#2): ServerAlreadyRunningError: A T3 Code server on evidence-host-a already owns $HOME/.t3/userdata, which this machine shares. Stop it on evidence-host-a, or use a separate T3 home and pair with it, then retry. No server was stopped. server-owner.sqlite is the ownership lock; do not delete it while a server is running.
    at Object.<anonymous> (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9040:47)
    at acquireServerOwnership.nameOwner (file://<checkout>/apps/server/dist/Schema-znhrSbG8.mjs:11072:28)
    at acquireServerOwnership.nameOwner (definition) (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9037:294)
    at acquireServerOwnership (file://<checkout>/apps/server/dist/server-CasZJMfH.mjs:53088:27)
    at acquireServerOwnership (definition) (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9001:32)
    at server.runServerCommand (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:10304:363)
    at server.runServerCommand (definition) (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:10275:26)
[exit 78]

$ t3 up --base-dir "$HOME/.t3-hostB" --yes --headless

ERROR
  The T3 Code service in this home serves $HOME/.t3, not $HOME/.t3-hostB, and its server runs on evidence-host-a, which shares this home. Change that service from evidence-host-a: uninstalling it here would also remove it there.
[exit 1]
Synthetic unit unchanged: True. No uninstall executed.

$ t3 __service-launcher (same shared T3 home)
[21:51:08.474] ERROR (#2): ServerAlreadyRunningError: A T3 Code server on evidence-host-a already owns $HOME/.t3/userdata, which this machine shares. Stop it on evidence-host-a, or use a separate T3 home and pair with it, then retry. No server was stopped. server-owner.sqlite is the ownership lock; do not delete it while a server is running.
    at Object.<anonymous> (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9040:47)
    at acquireServerOwnership.nameOwner (file://<checkout>/apps/server/dist/Schema-znhrSbG8.mjs:11072:28)
    at acquireServerOwnership.nameOwner (definition) (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9037:294)
    at acquireServerOwnership (file://<checkout>/apps/server/dist/server-CasZJMfH.mjs:53088:27)
    at acquireServerOwnership (definition) (file://<checkout>/apps/server/dist/relayTracing-BoTww0rd.mjs:9001:32)
    at server.runServerCommand (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:10304:363)
    at server.runServerCommand (definition) (file://<checkout>/apps/server/dist/binCli-CvGyPKRu.mjs:10275:26)
[service-launcher] A T3 Code server on evidence-host-a owns this T3 home, which this machine shares. Stop it on evidence-host-a, then restart this service.
[capture driver stopped the process it started]
Server A still alive after all commands: True.