LykosAI/StabilityMatrix · error · ValidationException

Length cannot be null when latentType is Hunyuan

Error message

Length cannot be null when latentType is Hunyuan

What it means

ComfyNodeBuilderExtensions.SetupEmptyLatentSource builds a ComfyUI latent node for the requested latentType. The Hunyuan branch (EmptyHunyuanLatentVideo) requires a frame Length, which has no default; if the caller supplies null length, the builder throws ValidationException stating that Length is mandatory when latentType is Hunyuan.

Solutions

1. Pass an explicit positive length (frame count) when latentType is Hunyuan.
2. Add a guard in the calling workflow to require a frame count for Hunyuan before invoking.
3. Default length to a sensible value (e.g. 1 or the workflow's frame count) when null for Hunyuan.

Example fix

// before
var latent = builder.SetupEmptyLatentSource(latentType, width, height, batchSize, length: null);

// after
var frames = latentType == LatentType.Hunyuan ? (length ?? 25) : null;
var latent = builder.SetupEmptyLatentSource(latentType, width, height, batchSize, length: frames);

if (latentType == LatentType.Hunyuan && length is null or <= 0)
    throw new InvalidOperationException("Provide a frame length for Hunyuan latents.");

try
{
    var latent = builder.SetupEmptyLatentSource(latentType, w, h, batch, length);
}
catch (ValidationException ex)
{
    notifier.ShowError(ex.Message);
}

When it happens

Trigger: Calling SetupEmptyLatentSource with latentType = Hunyuan and length = null (or omitting the length argument), e.g. when generating image latents instead of video.

Common situations: Code paths shared between standard image generation (no length needed) and Hunyuan video generation (length required) that forget to set a frame count; UI defaults not wired for Hunyuan workflows.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• Prompt extensions not installed
• No ImageSource
• Model not selected
• No VAE Selected
• No Clip1 Selected

AI-assisted analysis of LykosAI/StabilityMatrix@af93d6ef57 (2026-09-12). Data as JSON: /api/errors/87562e7645953ed7. Report an issue: GitHub.

Appendix: source

Thrown at StabilityMatrix.Avalonia/Extensions/ComfyNodeBuilderExtensions.cs:70

                    {
                        Name = builder.Nodes.GetUniqueName(nameof(ComfyNodeBuilder.EmptyFlux2LatentImage)),
                        BatchSize = batchSize,
                        Height = height,
                        Width = width,
                    }
                )
                .Output,
            LatentType.Hunyuan => builder
                .Nodes.AddTypedNode(
                    new ComfyNodeBuilder.EmptyHunyuanLatentVideo
                    {
                        Name = builder.Nodes.GetUniqueName(nameof(ComfyNodeBuilder.EmptyHunyuanLatentVideo)),
                        BatchSize = batchSize,
                        Height = height,
                        Width = width,
                        Length =
                            length
                            ?? throw new ValidationException(
                                "Length cannot be null when latentType is Hunyuan"
                            ),
                    }
                )
                .Output,
            _ => throw new ArgumentOutOfRangeException(nameof(latentType), latentType, null),
        };

        builder.Connections.Primary = primaryNodeConnection;
        builder.Connections.PrimarySize = new Size(width, height);

        // If batch index is selected, add a LatentFromBatch
        if (batchIndex is not null)
        {
            builder.Connections.Primary = builder
                .Nodes.AddTypedNode(
                    new ComfyNodeBuilder.LatentFromBatch
                    {

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