◎ Radiance Debug Probe

Every ComfyUI user has had the moment: the output is black, or NaN, or the values are all clipped to 1.0, and you have no idea where in the chain it happened. Radiance Debug Probe is the node you splice in to find out. It accepts any data type - an image, a string, a conditioning, a list, whatever - logs what it finds to the console, and passes the data through completely unchanged. You break the graph, probe it, and the graph doesn't know you touched it.

This is one of those genuinely useful plumbing nodes that barely exists in other packs, and it's the right idea for a pack that's selling you on a 32-bit float pipeline - because "my HDR values got destroyed somewhere" is exactly the kind of bug a probe like this was made to catch.

What it reports

The data input is a wildcard (*), so it adapts to whatever you connect. On a tensor it logs shape, value range, and dtype - the three things you need to know whether your image is still float32 with values above 1.0 or got clamped to 8-bit along the way. On a string it logs the value; on lists and dicts it logs the length and structure. That dtype/range readout is the killer feature for Radiance specifically, because the community's main complaint about this pack is that some nodes quietly collapse to 8-bit precision mid-pipeline - a probe at the end of each stage makes those collapses visible.

The controls

Three, and they're all convenience:

• label - a tag printed in the log line so you can tell your probes apart when you've got five of them in one graph. Name them after the wire they're on ("after_vae", "pre_grade").
• enabled - turn logging off without deleting the node from the graph. Nice when a probe's served its purpose but you don't want to rewire.
• log_level - INFO, DEBUG, or WARNING. INFO is default; pick WARNING if you're probing in a noisy workflow and want the output to stand out.

Outputs

Two: data - the input, passed through bit-for-bit unchanged, so the probe never alters your result (verify by wiring it in and out and diffing; it's a pass-through) - and probe_report, a human-readable diagnostic string. That second output is the sleeper feature: wire it to a text preview node and you get the diagnostic in the UI instead of having to dig through the terminal. For people who run ComfyUI from a desktop app and never look at a console, that's the difference between useful and forgettable.

The honest take

It's a debug tool, so its value scales with how much you debug. If you're on the happy path of stock workflows, you may never touch it. But the first time an HDR pipeline goes wrong - or any pipeline goes wrong, really - it beats guessing. Combined with the fact that the pack's own documentation is thin (a stated community complaint), a probe you can trust is a better companion than a wiki you can't.

Install

Part of fxtdstudios/radiance. Manager search "Radiance", or:

cd ComfyUI/custom_nodes
git clone https://github.com/fxtdstudios/radiance.git
cd radiance
pip install -r requirements_linux.txt   # or windows/mac_silicon

Restart after. The dependency set is heavy (OpenEXR, OpenColorIO, colour-science, transformers) and makes first boot slow; Linux needs libopenexr-dev before pip. If Manager's security level blocks the install, the README's manual-clone path is the workaround.