ComfyUI Live Sampler Preview

A lightweight ComfyUI custom node that displays a live preview source anywhere on the canvas. Select a sampler or KJ Nodes' Model Preview Override, or use Auto to follow the best active preview, including sources inside subgraphs.

The node is a frontend-only receiver. It does not connect to the workflow, execute a model, alter generation, send data over the network, or use additional VRAM beyond the browser surface used to display the received frame.

Live Sampler Preview is a display custom node that you place wherever you want to see a live sampling preview on the workflow canvas. It does not need to be connected to the sampler or preview override. The node's preview source dropdown lists compatible sources detected in the current workflow.

Features

• Place a live sampling preview anywhere in the workflow without adding connections.
• Follow the best active preview automatically or select a source manually.
• Find compatible sources in the root workflow and nested subgraphs.
• Mirror ComfyUI's built-in sampler preview canvas.
• Mirror the optional animated latent-preview canvas from ComfyUI-VideoHelperSuite.
• Receive KJ Nodes' Model Preview Override stream directly, including its VAE/tiny-VAE JPEG, animated WebP, and MP4 previews.
• No Python packages, models, or build step required for this custom node.

Install

From the ComfyUI/custom_nodes directory, run:

git clone https://github.com/sabi3293043/ComfyUI-LiveSamplerPreview.git

Restart ComfyUI, then hard-refresh the browser page. ZIP and Pinokio instructions are in the full installation guide.

This project is not yet listed in the ComfyUI Registry. Until it is registered, use Git or the ZIP installation method instead of searching for it in the new ComfyUI Manager.

Setup

Built-in sampler previews

1. Open Settings (gear icon).
2. Open Execution.
3. Set Live preview method to Latent2RGB (recommended for the easiest setup) or another method other than None.
4. Add utils > preview > Live Sampler Preview.
5. Choose a detected sampler from preview source, or leave Auto (best active preview) selected.
6. Queue the workflow.

KJ Model Preview Override

1. Place KJ Nodes' Model Preview Override in the model path that feeds your sampler.
2. Configure its VAE or tiny-VAE preview options normally.
3. Add Live Sampler Preview anywhere in the root graph.
4. In preview source, select the entry labeled KJ VAE preview, or leave Auto selected.
5. Queue the workflow. The receiver displays the exact dedicated stream produced by Model Preview Override, even when that node is inside a subgraph.

The ComfyUI global live-preview method does not need to supply the KJ stream. However, it is still required when you want the receiver to fall back to a regular sampler preview.

For TAESD, command-line setup, Video Helper Suite animation, and troubleshooting, see the configuration guide.

How it works

For normal samplers, the receiver mirrors the preview surface already rendered on the sampler node. For Model Preview Override, it subscribes to KJ Nodes' dedicated kj_preview_override event and decodes its browser payload directly. It does not run another VAE decode.

The receiver prefers sources in this order when Auto is selected:

1. The newest active KJ Model Preview Override stream.
2. The active sampler preview.
3. Any available compatible sampler preview.

Compatibility and limitations

• Designed for the modern ComfyUI frontend.
• Works with core KSampler nodes and many custom sampler-like nodes that expose sampling inputs/outputs or a supported preview surface.
• Direct KJ integration requires a KJ Nodes version that includes Model Preview Override and the kj_preview_override frontend event.
• A custom sampler that never creates a visible preview cannot be mirrored unless it provides a supported dedicated event.
• A preview is an in-progress approximation, not the final full-VAE output.
• Select a source explicitly when several sources execute at once and you do not want Auto's priority order.

Updating

Run this inside the installed custom-node folder, then restart ComfyUI:

git pull

Support

Before reporting a problem, work through Troubleshooting. If it still fails, open a GitHub issue with your ComfyUI version, browser, source node type, and a screenshot of the receiver.

License

MIT