CMK Preview Render

Most of the debugging advice for ComfyUI is "look at the pixels and figure it out". This node is the pack's answer to that, and it's a better answer than it sounds: instead of handing you the final image and letting you guess why it looks the way it does, it renders a stage's diagnostic payload as a labelled panel - intermediate images included - and shows it directly in the node.

Feed it one CMK_DIAGNOSTIC and it draws. That's the whole interface. CMK's modules emit a diagnostic output all over the place - detection results, mask composites, preprocessor hints, sampler state - and this is the screen you hang off them when something isn't behaving.

Inputs and what they do

diagnostic is the payload, a CMK_DIAGNOSTIC. Any node with a diagnostic output will do; that's where the panels' content comes from.

caption has three settings: Off, Standard, Details. They control how much text the panel carries - Off gives you the pictures only, Details gives you the full set of labels and the settings that produced the stage. There's a quirk worth knowing if you go reading the source: internally Standard is passed to the renderer under its older name, Summary. Same mode, historical name. Nothing you need to do about it, but it explains a label mismatch if you're diffing versions.

Output is an IMAGE - the rendered panel itself, as a normal tensor, so you can feed it wherever you want. The node is also flagged as an output node, which in ComfyUI means it always executes and won't be optimised away. Handy when you want a stage to render even if nothing consumes its result.

It's a Toolbox node, not a Developer one - CMK/Toolbox/Diagnostics, published in the pack's own catalogue with a preview and a description. So unlike the pipe plumbing, this is meant for you. It shows up in several of the pack's showcase workflows.

Where it earns its keep

Detailer and face modules are the obvious candidates. A detailer that pasted a rectangle seam onto a cheek, a mask that grabbed the wrong face, a detector that decided a shoulder was a nose - those are all stage-two problems where you'd normally be bisecting parameters blind. A rendered panel with the detection boxes and the mask composite right there tells you whether you're fixing the detector or the denoise in about four seconds.

The pack's own framing is honest about the ambition: it's a work tool, not documentation. When you actually use it, turn caption to Details - the settings in the captions are half the value, because they let you compare two runs from the images alone.

Installing the pack

ComfyUI Manager → search CMK Flow → install the entry from CMKFlow → restart ComfyUI.

git clone https://github.com/CMKFlow/cmk_nodes.git custom_nodes/cmk_nodes
python3 custom_nodes/cmk_nodes/scripts/install_cmk_requirements.py

Wait for CMK dependency check: OK. That helper locates the interpreter ComfyUI is really using and installs requirements.txt into it - on Desktop installs there may be a system Python, a standalone-env and a .venv, and installing into the wrong one is the usual reason a fresh CMK install appears inert. The pack imports all of its nodes together, so a broken dependency can take unrelated nodes down with it.

Updates are git -C custom_nodes/cmk_nodes pull --ff-only then the installer again. Weights aren't in the Python package; the resource checker (scripts/check_cmk_resources.py --models-root ...) will audit and optionally fetch what the bundled workflows expect.

One note on provenance, since this pack is young. It went open source in July 2026, announced by its author on r/comfyui as CMKFlow/cmk_nodes, with the stated goal being a modular pipeline that installs clean on a fresh ComfyUI without dragging in a chain of unrelated node packs. The Flip side of that ambition: the community footprint is small - a handful of posts, single-digit comment counts - so there isn't a decade of forum threads to lean on when something goes wrong. The author is responsive in those threads, which is worth more.

Requirements before you blame the node: Vue Nodes / Nodes 2.0 has to be enabled for CMK's dynamic nodes to render properly, and previews during sampler runs want Execution → Live preview method set to auto.

Two practical notes

The rendered panel gets saved as a PNG, so if you leave several of these in a graph you'll accumulate preview files in ComfyUI's temp storage. Not a problem, just don't be surprised by the directory.

And a diagnostic that renders as an empty or placeholder panel usually means you hung the render node off a module that didn't populate its diagnostic payload - check that the module you tapped actually ran, rather than assuming the renderer is broken.