Commandlets and headless CI

Choose headless execution

Use UnrealEditor-Cmd.exe for commandlets and unattended automation. Quote the .uproject and output paths. Capture stdout/stderr, process exit code, engine version, project revision, and report artifacts.

Verified 5.8 examples:

UnrealEditor-Cmd.exe Project.uproject -run=DataValidation

UnrealEditor-Cmd.exe Project.uproject -run=pythonscript -script="C:\Path\job.py"

UnrealEditor-Cmd.exe Project.uproject \
  -ExecCmds="Automation RunTest Project.Suite;Quit" \
  -ReportExportPath="C:\Reports\Automation"

Use -ExecutePythonScript="..." instead when the job needs the full editor and default startup level loaded. The Python commandlet does not load a level automatically; load the required level explicitly through LevelEditorSubsystem.

CI contract

Each job must define:

• required plugins and build target;
• isolated workspace and writable Derived Data/Intermediate/Saved paths;
• timeout and hung-process policy;
• exact success/failure exit conditions;
• machine-readable report location;
• artifact retention for logs, screenshots, and diffs.

Never parse only a “completed” log line. Fail when the process exits nonzero, the report is absent or malformed, tests fail, validation errors occur, or the expected output count differs.

High-risk commandlets

ResavePackages, redirector cleanup, mass import, and migration rewrite many packages. Run on a clean branch/workspace, narrow scope when supported, dry-run through discovery first, and inspect the resulting diff. Epic's documented redirector cleanup example uses ResavePackages with -fixupredirects; source-control flags can automatically check out files, so do not add them without deliberate authorization.

Determinism

Sort inputs, avoid current selection/editor UI state, seed random operations, use stable output paths, and make retries idempotent. Record the command line with secrets removed.