CTest interactive debug mode

October 26, 2026

CTest –interactive-debug-mode is particularly useful on Windows to enable/disable debug dumps and error popup modal windows, especially for missing DLL errors. By default this feature is enabled. This default behavior to have interactive debug mode “on” can make problems with modal popups hanging on automated systems like CI or agentic workflows where user interaction is not desired or possible.

To avoid this, one can explicitly disable interactive debug mode by option

ctest --interactive-debug-mode=0

An even better approach is to make CMakePresets.json explicitly set the interactive debug mode for CTest invocation with preset or workflow with "interactiveDebugging": false thats inherited for all CTest preset execution like:

{
  "version": 6,

"testPresets": [
{
  "name": "default",
  "configurePreset": "default",
  "output": {
    "outputOnFailure": true,
    "verbosity": "verbose"
  },
  "execution": {
    "interactiveDebugging": false,
    "noTestsAction": "error",
    "scheduleRandom": true,
    "stopOnFailure": false
  }
}
]
}

In agentic instruction files like CMAKE.instructions.md or similar, consider adding a line like:

CTest on Windows should be run with option --interactive-debug-mode=0 to prevent modal popups from interrupting automated workflows.

NOTE: CTest environment variable CTEST_INTERACTIVE_DEBUG_MODE is read-only and has no effect on setting the interactive debug mode. The mode must be controlled via the --interactive-debug-mode command-line option when invoking CTest.