Diagnostic client isolation prerequisite on the board

On 2026-09-23 the coordinator ran the committed tests/vglite/check_root_trial_credentials.py --user shell as root through the reserved board console, using the installed Python 3.14.7. The source was 141b6aa, integrated as 5628a18; its companion tools/vglite-root-scene-trial.py was copied alongside it under /run. The transfer’s MD5 matched on the board. Installed system and boot ID are recorded in docs/evidence/final-shell-image/installed-status.txt.

Actual test output reports success. The transient system-manager client ran as UID 1000, GID 995, with NoNewPrivs=1 and zero effective capabilities. Actual socket peer credentials matched. It connected to the shared Unix socket but was denied access to root-private IPC, a regular-file GPU fixture and the root test process’s held fixture descriptor through /proc. The client exited zero; its runtime was 747ms. The final cleanup’s unit-not-loaded message follows --collect removing the already-completed transient unit and was not a test failure.

This test opened no DRM or VG-Lite device, launched no compositor and did not stop the normal shell. shell and seatd remained active afterwards. It closes only the diagnostic harness’s real multi-UID credential prerequisite, which the unprivileged development host could not exercise. Actual GPU access, GPU rendering/cache correctness, panel output, diagnostic-session restoration, and normal-service compositor-only access remain UNVERIFIED.