LykosAI/StabilityMatrix · error · InvalidOperationException

Flux Kontext UNET model not found

Error message

Flux Kontext UNET model not found

What it means

FluxKontextModelManager.SelectModels searches clientManager.UnetModels for a locally installed Flux Kontext checkpoint (filename containing 'flux1-dev-kontext' or 'flux-kontext'). If none is present with a Local file, it throws this InvalidOperationException because the Kontext workflow cannot be assembled.

Solutions

1. Download a Flux Kontext UNET (e.g. flux1-dev-kontext_dev.safetensors) into the diffusion_models folder and refresh the index
2. Rename/move the existing file so its name contains 'flux-kontext' in a scanned folder
3. Catch InvalidOperationException and prompt the user with a one-click download of the Kontext UNET

Example fix

// before
var models = fluxKontextModelManager.SelectModels();
// after
if (!clientManager.UnetModels.Any(m => m.Local != null && m.FileName.Contains("flux-kontext", StringComparison.OrdinalIgnoreCase)))
{
    throw new UserDownloadableError("Flux Kontext UNET is not installed. Download it first.");
}
var models = fluxKontextModelManager.SelectModels();

var unet = clientManager.UnetModels.FirstOrDefault(m => m.Local != null
    && (m.FileName.Contains("flux1-dev-kontext", StringComparison.OrdinalIgnoreCase)
        || m.FileName.Contains("flux-kontext", StringComparison.OrdinalIgnoreCase)));
if (unet is null) throw new UserDownloadableError("Flux Kontext UNET is not installed.");

bool HasLocalKontextUnet(IEnumerable<HybridModelFile> models) => models.Any(m => m.Local != null && m.FileName.Contains("flux-kontext", StringComparison.OrdinalIgnoreCase));

try
{
    var models = fluxKontextModelManager.SelectModels();
}
catch (InvalidOperationException ex) when (ex.Message.Contains("Kontext UNET model not found"))
{
    // trigger Kontext UNET download flow
}

When it happens

Trigger: Calling SelectModels when no UnetModels entry has Local != null and a filename containing 'flux1-dev-kontext' or 'flux-kontext' (case-insensitive) — the Kontext UNET was never downloaded or isn't indexed.

Common situations: User runs the Kontext workflow before downloading flux1-dev-kontext_dev.safetensors; model in a folder not scanned by ComfyUI; file renamed so the substring match fails.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Flux.2 Klein UNET model not found
• Flux.2 VAE model not found
• Klein 9B requires the qwen_3_8b text encoder, which isn't…
• Klein 4B requires the qwen_3_4b text encoder, which isn't…
• Flux VAE model not found

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/131cc330e2db80da. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Avalonia/Services/FluxKontextModelManager.cs:173

                _ => model.FileName,
            };
            yield return name;
        }
    }

    /// <summary>
    /// Select the best available models for Flux Kontext (only selects LOCAL models)
    /// </summary>
    internal FluxKontextWorkflowBuilder.SelectedModels SelectModels(IInferenceClientManager clientManager)
    {
        var unetModel =
            clientManager.UnetModels.FirstOrDefault(m =>
                m.Local != null
                && (
                    m.FileName.Contains("flux1-dev-kontext", StringComparison.OrdinalIgnoreCase)
                    || m.FileName.Contains("flux-kontext", StringComparison.OrdinalIgnoreCase)
                )
            ) ?? throw new InvalidOperationException("Flux Kontext UNET model not found");

        var vaeModel =
            clientManager.VaeModels.FirstOrDefault(m =>
                m.Local != null && m.FileName.Equals("ae.safetensors", StringComparison.OrdinalIgnoreCase)
            ) ?? throw new InvalidOperationException("Flux VAE model not found");

        var clip1Model =
            clientManager.ClipModels.FirstOrDefault(m =>
                m.Local != null && m.FileName.Contains("clip_l", StringComparison.OrdinalIgnoreCase)
            ) ?? throw new InvalidOperationException("CLIP-L model not found");

        var clip2Model =
            clientManager.ClipModels.FirstOrDefault(m =>
                m.Local != null
                && (
                    m.FileName.Contains("t5xxl", StringComparison.OrdinalIgnoreCase)
                    || m.FileName.Contains("t5-xxl", StringComparison.OrdinalIgnoreCase)
                )

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