Dynamic Preview

Dynamic Preview is the debugging node you reach for when a wire isn't doing what you think. It's a pure viewer: plug anything into it - an image, a mask, a latent, a conditioning, a string, a number, a dict - and it shows you what's actually on that wire. Images and masks render as pictures in the node body; everything else renders as formatted text. No outputs at all. It's a dead end on purpose, and it's remarkably handy.

The situation it exists for: your conditioning is coming out wrong, or that tensor that was supposed to survive a subgraph came back empty, or you genuinely have no idea what type a dynamic node is producing mid-graph. Drag a wire into the preview, run, and look. In v1.7.1 it graduated out of its "Beta" label and now accepts any input type - earlier versions were image-only, which is how you know the text support is recent.

How it works

The backend inspects every connected input. Torch tensors that look like images or masks (by shape) get saved as temp PNGs and returned through the standard preview UI mechanism, so they show up as actual pictures. Everything else - conditioning lists, dicts, strings, numbers - is rendered to formatted text, with tensors shown as shape + dtype rather than a wall of numbers. Long text is capped at 2000 characters with a truncation note. The tabbed selector on the node body lets you flip between inputs, and the tab bar scrolls horizontally when it overflows the node width.

Inputs and outputs

• Any number of * inputs - up to 32, growing as you connect.
• No outputs. It's an output node (OUTPUT_NODE = True), which means it always executes and counts as a graph endpoint.

That last point matters: because it's an output node, having one in your graph forces a run to complete and shows the preview result in the UI. It's not free, but it's cheap.

Install

Manager → search "Tojioo Passthrough" → Install → restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/Tojioo/tojioo_passthrough.git

No models, no pip deps, prebuilt frontend bundle. Category: Tojioo Passthrough → Dynamic Nodes.

Common issues

Two things trip people up. First, previews write to ComfyUI's temp directory and show in the node - if you were expecting a file you can keep, this isn't a save node. Second, remember it's a viewer, not a passthrough: wire it in after the node you're inspecting, not between it and the next step, or you've broken the flow. If a tab shows truncated text, that's the 2000-character cap working as designed - the shape/dtype info you usually need is at the top anyway. The author pairs it with the Dynamic Bus in the example workflow, and honestly that's a great combination: bus in, preview on a few slots, instant visibility into what's actually riding the wire.