LykosAI/StabilityMatrix · error · ValidationException

No VAE Selected

Error message

No VAE Selected

What it means

Thrown in UnetModelCardViewModel.ApplyStep when building a UNet (e.g. SDXL/Flux/GGUF) checkpoint workflow and no VAE file is selected in the card. The workflow includes a VAELoader node that requires a VaeName, so a null SelectedVae aborts graph construction with this ValidationException.

Solutions

1. Select a VAE file in the VAE dropdown of the UNet model card (e.g. sdxl_vae.safetensors)
2. Download/import a VAE into the models/vae folder via Model Manager if none is installed
3. Re-point the preset to an installed VAE if the previously selected one was removed

Example fix

// before
await vm.ApplyStep(args); // SelectedVae null -> throws
// after
if (vm.SelectedVae is null) { throw new ValidationException("Pick a VAE in the model card first"); }
await vm.ApplyStep(args);

if (vm.SelectedVae is null)
    throw new ValidationException("Select a VAE in the UNet model card before generating");

bool hasVae = vm.SelectedVae is not null;

try { vm.ApplyStep(args); }
catch (ValidationException ex) when (ex.Message == "No VAE Selected") { /* surface VAE picker */ }

When it happens

Trigger: ApplyStep executed with SelectedVae == null at the point the ComfyNodeBuilder.VAELoader node is added (VaeName = SelectedVae?.RelativePath ?? throw).

Common situations: Fresh install or new model directory where no VAE has been downloaded/selected; user cleared the VAE dropdown; preset referencing a VAE that is no longer installed.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• Model not selected
• No VAE Selected
• Length cannot be null when latentType is Hunyuan
• Flux.2 VAE model not found
• Flux VAE model not found

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/98dc2fdf01505eea. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Avalonia/ViewModels/Inference/UnetModelCardViewModel.cs:70

        var dialog = DialogHelper.CreateMarkdownDialog(
            "Please select a model to continue.",
            "No Model Selected"
        );
        await dialog.ShowAsync();
        return false;
    }

    public void ApplyStep(ModuleApplyStepEventArgs e)
    {
        var checkpointLoader = e.Nodes.AddTypedNode(GetModelLoader(e, SelectedModel!, SelectedDType));
        e.Builder.Connections.Base.Model = checkpointLoader.Output;

        var vaeLoader = e.Nodes.AddTypedNode(
            new ComfyNodeBuilder.VAELoader
            {
                Name = e.Nodes.GetUniqueName(nameof(ComfyNodeBuilder.VAELoader)),
                VaeName = SelectedVae?.RelativePath ?? throw new ValidationException("No VAE Selected"),
            }
        );
        e.Builder.Connections.Base.VAE = vaeLoader.Output;

        // DualCLIPLoader (GGUF variant can also load .safetensors, so any gguf pick routes there)
        var clipName1 = SelectedClip1?.RelativePath ?? throw new ValidationException("No Clip1 Selected");
        var clipName2 = SelectedClip2?.RelativePath ?? throw new ValidationException("No Clip2 Selected");

        e.Builder.Connections.Base.Clip =
            SelectedClip1 is { IsGguf: true } || SelectedClip2 is { IsGguf: true }
                ? e
                    .Nodes.AddTypedNode(
                        new ComfyNodeBuilder.DualCLIPLoaderGGUF
                        {
                            Name = e.Nodes.GetUniqueName(nameof(ComfyNodeBuilder.DualCLIPLoaderGGUF)),
                            ClipName1 = clipName1,
                            ClipName2 = clipName2,
                            Type = "flux",

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