What causes "Unexpected torch verification output: {verificationOutput}" in LykosAI/StabilityMatrix?

Re-run the torch install with a clean environment so the verification script's stdout contains only the JSON object (check python/pip is on PATH and the venv is intact).

LykosAI/StabilityMatrix · error · InvalidOperationException

Unexpected torch verification output

Error message

Unexpected torch verification output: {verificationOutput}

What it means

VerifyWindowsNativeTorchInstallAsync runs a Python one-liner that prints a JSON object describing the installed torch build (torch/torchvision versions, hip, cuda availability). If the raw output contains no parseable JSON object (TryExtractJsonObject returns null/whitespace), the helper treats the verification as uninterpretable and throws this InvalidOperationException. It exists so an install is never silently accepted when the probe output is garbled.

Solutions

Re-run the torch install with a clean environment so the verification script's stdout contains only the JSON object (check python/pip is on PATH and the venv is intact).
Look at the raw verificationOutput in the exception message to see what actually was printed and fix the underlying probe failure (e.g. missing torch, DLL load error).
Retry the install of the ROCm torch wheels so the package is present before verification runs.
Update the app, as newer versions may harden the JSON extraction against noisy output.

Example fix

// before: verification output polluted by warnings
"WARNING: ...\n{\"torch\":\"2.3.0+rocm5.7\"}"
// after: ensure the probe prints only JSON, e.g. run with warnings suppressed
python -W ignore -c "import json,torch;print(json.dumps({'torch':torch.__version__,...}))"

Defensive patterns

Strategy: validation

Validate before calling

var json = TryExtractJsonObject(verificationOutput);
if (string.IsNullOrWhiteSpace(json)) throw new InvalidOperationException($"No JSON in torch verification output: {verificationOutput}");

Type guard

static bool LooksLikeJsonObject(string? s) =>
    !string.IsNullOrWhiteSpace(s) && s.TrimStart().StartsWith('{') && s.TrimEnd().EndsWith('}');

Try / catch

try { await helper.InstallWindowsNativeTorchAsync(...); }
catch (InvalidOperationException ex) when (ex.Message.Contains("Unexpected torch verification output"))
{
    logger.Warning(ex, "Torch verification output unparseable; inspecting environment");
    // surface raw output, repair python env, retry
}

Prevention

Keep the probe's stdout pure JSON: suppress warnings or route them to stderr.
Verify the Python/venv and torch import work before invoking install+verify.
Log the raw verification output whenever verification fails.
Pin torch/torchvision versions so probes behave deterministically.

When it happens

Trigger: InstallWindowsNativeTorchAsync -> VerifyWindowsNativeTorchInstallAsync when the embedded Python verification snippet prints anything other than a JSON object (extra banner text, warning lines, crash tracebacks, or empty/stderr-only output) so TryExtractJsonObject cannot isolate a JSON object.

Common situations: A broken or mismatched Python/venv environment prints import errors or pip warnings into the output; a GPU driver or ROCm runtime emits warning text before the JSON; torch failed to import and the process wrote a traceback instead of the expected JSON; output encoding or console buffering corrupts the JSON.

Related errors

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/c56b31fbec8cddd0. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Core/Services/Rocm/RocmPackageHelper.cs:449

            throw new InvalidOperationException("torch was not installed after Windows ROCm setup.");
        }

        var verificationResult = await venvRunner
            .Run(
                "-c \"import json, torch; print(json.dumps({'version': torch.__version__, 'hip': torch.version.hip, 'cuda': torch.cuda.is_available()}))\""
            )
            .ConfigureAwait(false);

        var verificationOutput = (verificationResult.StandardOutput ?? string.Empty).Trim();
        if (string.IsNullOrWhiteSpace(verificationOutput))
        {
            throw new InvalidOperationException("Torch verification produced no output.");
        }

        var verificationJson = TryExtractJsonObject(verificationOutput);
        if (string.IsNullOrWhiteSpace(verificationJson))
        {
            throw new InvalidOperationException(
                $"Unexpected torch verification output: {verificationOutput}"
            );
        }

        JsonDocument verificationDocument;
        try
        {
            verificationDocument = JsonDocument.Parse(verificationJson);
        }
        catch (Exception exception)
        {
            throw new InvalidOperationException(
                $"Unexpected torch verification output: {verificationOutput}",
                exception
            );
        }

        using (verificationDocument)

View on GitHub (pinned to af93d6ef57)