Terrain Builder from the official DayZ Tools Steam installation cannot start on Windows 11. The failure happens before any project is opened; no Terrain Builder process or new application log appears.

Observed file product version: 1.31.0.164046. Steam App ID: 830640. Steam build observed during verification on 19 October 2026: 25460346.

The DayZ Tools launcher reports: "Une stratégie de contrôle d’application a bloqué ce fichier" (An application control policy has blocked this file).

Windows CodeIntegrity Operational event 3077 identifies policy VerifiedAndReputableDesktop (Smart App Control), GUID {0283ac0f-fff1-49ae-ada1-8a933130cad6}, status 0xc0e90002. Requested signing level 2; validated signing level 1. The executable has no Authenticode signature according to the local signature check.

Executable SHA256 (flat file): 36817FB3879F7C94462CE6D3ACD1CDEFABED09FBF51F0FF3C5BF0E976021C957.

Steam’s official file-integrity verification completed successfully on 19 October 2026: all 684 files validated. Reinstalling DayZ Tools produced the identical executable hash and the normal launcher attempt still received the application-control denial.

Actual result: Windows application-control policy blocks execution before Terrain Builder initialization.

Please investigate Smart App Control compatibility and provide a correctly signed/trusted official release or another supported remedy that does not require globally disabling Windows protection. These observations do not independently establish whether the block is a false positive.

1. Install or update DayZ Tools through Steam.

2. Launch DayZ Tools normally through Steam.

3. Click Terrain Builder.

4. Observe that no Terrain Builder window starts and the launcher logs the application-control denial.

The official Terrain Builder application should start in a supported Windows 11 security configuration.