PR #24943 runtime verification
Head: 36a1d193d4818754d114550c905a9edb56d12440
Real Node T3 server processes, isolated data directories.
External boundary: controlled tailscale CLI with persisted Serve JSON and a local HTTPS reverse proxy.
This does not prove real-daemon behavior or the Electron UI.

A environmentId ac3e0a32-813c-4e7b-acb7-24b8a1401b39
after A {"/keep/":{"Text":"other app"},"/":{"Proxy":"http://127.0.0.1:24501"}}
B environmentId 40f1fb46-3808-469d-815c-ade9c416dc71
after B {"/keep/":{"Text":"other app"},"/":{"Proxy":"http://127.0.0.1:24501"}}
desktop A endpoints [{"httpBaseUrl":"https://localhost:24443/","status":"available"}]
desktop B endpoints [{"httpBaseUrl":"https://localhost:24443/","status":"unavailable"}]
shared URL environmentId ac3e0a32-813c-4e7b-acb7-24b8a1401b39
after B clean exit {"/keep/":{"Text":"other app"},"/":{"Proxy":"http://127.0.0.1:24501"}}
C environmentId 38c68a3a-1151-451a-8124-959312082507
after stale recovery {"/keep/":{"Text":"other app"},"/":{"Proxy":"http://127.0.0.1:24503"}}
after C clean exit {"/keep/":{"Text":"other app"}}
keep handler response other app

Regression checks via Blacksmith:
Current main Serve calls: 4 failures / 8 passes in tailscale.test.ts (new safety case included).
Original PR + safety regression cases: 2 failures / 11 passes.
Ambiguous hostname regression before fix: 1 failure / 12 passes.
Final check:changed: format, lint, both knip checks, GraphQL validation, 4 package typechecks and 37 tests in 4 files passed.

Known limits: simultaneous start race (no CLI compare-and-swap); live Tailscale daemon; macOS/Windows; Electron Tailscale toggle. Pair and dev-runner intentionally retain existing behavior.