Skin Beauty | Internal Preview Sink

If you found "Skin Beauty | Internal Preview Sink" while poking around in ComfyUI's developer mode, here's the honest summary: don't add it to a workflow, and don't feel bad about never using it. It's not a tool for you - it's the plumbing behind the real-time before/after preview on the pack's Process + Preview node.

What it actually is

It's a DEV_ONLY output node from the ComfyUI-SkinBeauty-CN pack, filed under the _internal/skinbeauty_cn category. Its job is to be a temporary output target for the exact-preview feature. When you turn on 实时精确预览 (real-time exact preview) on the processor, the pack's web extension builds a throwaway API prompt that clones just the processor node plus its necessary IMAGE, parameter, and MASK ancestors - nothing else, no save nodes, no video encoders - and injects this sink as the output. That's how ComfyUI runs a partial graph instead of your whole workflow every time you drag the comparison slider. The README is explicit that this sink "is not serialized into user workflows"; it exists only in the transient preview prompt.

Inputs and what it does

It takes exactly three inputs:

• before (IMAGE) and after (IMAGE) - the pre- and post-correction tensors.
• request_id (STRING) - a token used to match a preview request to its result, so stale results get discarded.

It has no outputs and isn't a normal node in the graph sense; it's an output node that emits UI-only data - it writes a metadata-free, display-scaled temporary PNG of each side for the canvas comparer and reports the request id. It never touches your real IMAGE output: the processor's 美白图像 socket stays full-resolution and full-fidelity regardless.

Why it's hidden

ComfyUI only shows DEV_ONLY nodes when developer mode is enabled, which is why this one doesn't clutter your node menu. If you see it in a dev-mode graph, it's either a live preview mid-run or the leftover of one - there's nothing to configure and nothing to install. The one scenario where it matters to you is if you're building workflows programmatically via the API and want to understand why preview prompts occasionally reference a node you never added. That's it. You can file this page under "things that work precisely because you don't have to think about them."