LykosAI/StabilityMatrix · error · InvalidOperationException

Torch is not installed in the virtual environment.

Error message

Torch is not installed in the virtual environment.

What it means

InstallNunchakuStep.ExecuteAsync queries the package's venv for torch metadata to pick a matching Nunchaku wheel; if torch is not installed, torchInfo is null and InvalidOperationException is thrown.

Solutions

1. Install torch into the package venv before running the Nunchaku step
2. Reinstall/repair the package so its venv includes torch
3. Verify with pip list inside the venv that torch is present before installing Nunchaku

Example fix

// before
await nunchakuStep.ExecuteAsync();
// after
if (await venv.GetPipPackageInfo("torch") is null) await torchInstallStep.ExecuteAsync();
await nunchakuStep.ExecuteAsync();

var torch = await venv.GetPipPackageInfo("torch");
if (torch is null) await installTorchAsync(venv);

try { await step.ExecuteAsync(progress); } catch (InvalidOperationException ex) when (ex.Message.Contains("Torch")) { await installTorchAsync(venv); await step.ExecuteAsync(progress); }

When it happens

Trigger: Running the Nunchaku install step on a package venv where torch was never installed or was uninstalled, so pip query returns no torch package.

Common situations: Fresh package installs where torch install failed or was skipped; users who removed torch to save disk space; broken venvs.

Understand the failure class

Background: "not installed", "pip install", "required for": how missing-dependency errors surface across open-source libraries — this error's family across 34 libraries.

Related errors

• No compatible torch version found in the virtual…
• ComfyUI venv was not found at
• Windows ROCm bitsandbytes is only supported on Python 3.12.x
• Failed to start Forge Classic install process
• pyvenv.cfg is UTF-16 encoded; expected UTF-8/ASCII

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/f6281e7e3dac0ef6. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Core/Models/PackageModification/InstallNunchakuStep.cs:60

            venvDir,
            workingDirectory: WorkingDirectory,
            environmentVariables: EnvironmentVariables
        );

        var torchInfo = await venvRunner.PipShow("torch").ConfigureAwait(false);
        var shortPythonVersionString = pyVersion.Minor switch
        {
            10 => "cp310",
            11 => "cp311",
            12 => "cp312",
            13 => "cp313",
            _ => throw new ArgumentOutOfRangeException("Invalid Python version"),
        };
        var platform = Compat.IsWindows ? "win_amd64" : "linux_x86_64";

        if (torchInfo is null)
        {
            throw new InvalidOperationException("Torch is not installed in the virtual environment.");
        }

        var torchVersion = torchInfo.Version switch
        {
            var v when v.StartsWith("2.7") => "2.7",
            var v when v.StartsWith("2.8") => "2.8",
            var v when v.StartsWith("2.9") => "2.9",
            var v when v.StartsWith("2.10") => "2.10",
            _ => throw new InvalidOperationException(
                "No compatible torch version found in the virtual environment."
            ),
        };

        var downloadUrl =
            $"https://github.com/nunchaku-tech/nunchaku/releases/download/v1.0.2/nunchaku-1.0.2+torch{torchVersion}-{shortPythonVersionString}-{shortPythonVersionString}-{platform}.whl";
        progress?.Report(
            new ProgressReport(-1f, message: "Installing Nunchaku backend", isIndeterminate: true)
        );

View on GitHub (pinned to af93d6ef57)