LykosAI/StabilityMatrix · error · FileNotFoundException

Default Python installation not found at

Error message

Default Python installation not found at {defaultInstallation.InstallPath}

What it means

PyRunner.Initialize (parameterless) resolves the default Python installation from the installation manager and validates it exists on disk before initializing the engine. If the default installation directory is missing, a FileNotFoundException naming the InstallPath is thrown.

Solutions

Ensure a Python runtime is installed via the installation manager (download shared runtime) before calling Initialize
Verify defaultInstallation.InstallPath exists; reinstall if missing
Catch FileNotFoundException and run environment setup/repair flow
Re-register a valid default installation

Example fix

// before
await pyRunner.Initialize(); // no runtime installed
// after
await installationManager.SetupSharedRuntimeAsync(defaultVersion);
await pyRunner.Initialize();

Defensive patterns

Strategy: validation

Validate before calling

var defaultInstallation = await installationManager.GetDefaultInstallationAsync();
if (!Directory.Exists(defaultInstallation.InstallPath))
    await installationManager.SetupSharedRuntimeAsync();

Try / catch

try
{
    await pyRunner.Initialize();
}
catch (FileNotFoundException ex)
{
    logger.LogError(ex, "Default Python install missing; setting up runtime");
    await installationManager.SetupSharedRuntimeAsync();
    await pyRunner.Initialize();
}

Prevention

Ensure first-run setup downloads the shared runtime before Python features are used
Check default installation existence at app startup
Repair/reinstall the runtime after partial data-directory deletes

When it happens

Trigger: Calling PyRunner.Initialize() when no default Python installation exists or its folder was deleted/moved after registration.

Common situations: First-run before any Python runtime was downloaded, user manually deleted the shared runtime folder, reset app data partially, failed upgrade left stale registration.

Understand the failure class

Background: "File not found" and ENOENT errors: why libraries can't find a file that should exist — this error's family across 50 libraries.

Related errors

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/dad70c108fbaa134. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Core/Python/PyRunner.cs:237

    }

    /// <summary>$
    /// Initializes the Python runtime using the embedded dll.
    /// Can be called with no effect after initialization.
    /// </summary>
    /// <exception cref="FileNotFoundException">Thrown if Python DLL not found.</exception>
    public async Task Initialize()
    {
        if (PythonEngine.IsInitialized)
            return;

        // Get the default installation
        var defaultInstallation = await installationManager
            .GetDefaultInstallationAsync()
            .ConfigureAwait(false);
        if (!defaultInstallation.Exists())
        {
            throw new FileNotFoundException(
                $"Default Python installation not found at {defaultInstallation.InstallPath}"
            );
        }

        currentInstallation = defaultInstallation;
        await InitializeWithInstallation(defaultInstallation).ConfigureAwait(false);
    }

    /// <summary>
    /// One-time setup for get-pip
    /// </summary>
    public async Task SetupPip(PyVersion? version = null)
    {
        // Use either the specified version or the current installation
        var installation =
            version != null
                ? await installationManager.GetInstallationAsync(version.Value).ConfigureAwait(false)
                : currentInstallation

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