PR 14875: headless Linux proof
Base: 1451e7cb23034d29774338608368a15d8845df36
Published candidate: 14699c500852f678f732f2df558fa27d525387ab

Real child-process handoff, isolated filesystem; actual Launcher and ServiceLauncherClient, minimal startup driver. No full HTTP server, systemd or launchd service was run.

BASELINE: actual main ServiceLauncherClient with real launcher IPC commits 1.0.0 -> 2.0.0, but custom-bin and PATH links remain at 1.5.0.

FRESH TRIAL: real launcher IPC committed 1.0.0 -> 2.0.0; both custom-bin and PATH links moved 1.5.0 -> 2.0.0 only after acknowledgement.
STORED COMMIT RESTART: actual child received committed history; both user pins remained at 1.5.0.
PASS: isolated filesystem, real child processes/IPC, actual Launcher and ServiceLauncherClient; no installed service or HTTP server used.


Regression experiments (production bytes restored):
- Disable reconciliation: pending trial fails, stored outcome passes.
- Remove only pending guard: pending trial passes, stored outcome fails.
- Before custom service environment fix: both new Linux/macOS service-definition cases fail.

Round 2 regressions: restoring the previous candidate produces three failures: both ordinary-CLI custom-directory retention scenarios and cleanup-defect startup. Fixed candidate passes all three; production bytes restored exactly.

Final focused suite:
note: You are running `vp test` as a Vite+ built-in command. If you meant to run the test npm script, use `vpr test` instead.

 RUN  v5.0.1 /home/ubuntu/wt/desktop-app-05


 Test Files  6 passed (6)
      Tests  79 passed (79)
   Start at  10:06:09
   Duration  10.53s (transform 58%, import 35%, tests 5%, setup 2%)

  Transform  transforming modules took 14.54s · 58% of tracked time, re-done on every run
             persist transforms across runs with fsModuleCache: true
             learn more: https://vitest.dev/guide/improving-performance#caching-between-reruns


Server-only typecheck, scoped lint, formatting and whitespace pass. One pre-existing unused-layer lint warning remains.

Current-candidate real process proof repeated after review fixes:
FRESH TRIAL: real launcher IPC committed 1.0.0 -> 2.0.0; both custom-bin and PATH links moved 1.5.0 -> 2.0.0 only after acknowledgement.
STORED COMMIT RESTART: actual child received committed history; both user pins remained at 1.5.0.
PASS: isolated filesystem, real child processes/IPC, actual Launcher and ServiceLauncherClient; no installed service or HTTP server used.

Limits: no installed systemd/launchd update, full HTTP server, native macOS/Windows/Electron/iOS/Android. Existing custom units without a stored directory still need local reinstall with T3CODE_INSTALL_BIN_DIR available. Stored directory survives later CLI status/reinstall/update; explicit replacement wins.

Published-head proof rerun:
FRESH TRIAL: real launcher IPC committed 1.0.0 -> 2.0.0; both custom-bin and PATH links moved 1.5.0 -> 2.0.0 only after acknowledgement.
STORED COMMIT RESTART: actual child received committed history; both user pins remained at 1.5.0.
PASS: isolated filesystem, real child processes/IPC, actual Launcher and ServiceLauncherClient; no installed service or HTTP server used.