Concat String (Single) 📅🅕🅝

Concat String (Single) does exactly one thing: it takes string_a, appends string_b, and hands back the result. That's the whole node. It's the sort of thing you'd normally do with a text editor, which makes it easy to dismiss - but inside a graph it earns its keep, because it lets you assemble the keyframe text that the FizzNodes schedulers chew on.

What it's actually for

The FizzNodes prompt and value schedulers take one big text blob in the "frame" : "prompt" format. When that text needs to be partially dynamic - a fixed prefix that changes, a suffix you want to swap between runs, a filename or wildcard that comes from another node - Concat String (Single) is the seam. Build one half somewhere else in the graph, keep the other half static, and concatenate them into the scheduler's text input. Since both inputs are forced to be wired (forceInput), it's designed for graph plumbing, not for typing in the UI.

There's a sibling - String Concatenate in the same pack - that joins up to seven strings into a full keyframe schedule with frame numbers. This one is dumber and smaller: literally string_a + string_b, no frames, no formatting. If you're building a schedule string piece by piece, String Concatenate is usually the better tool. Reach for this one when you just need to glue two arbitrary strings together without the keyframe scaffolding.

The trivial mechanics

The output STRING is the concatenation, with no separator inserted - "foo" and "bar" becomes "foobar". If you want a space or a comma between them, you have to include it yourself (trailing space on string_a or a leading one on string_b). That's the one "gotcha," and it's not much of one.

Install

cd ComfyUI/custom_nodes && git clone https://github.com/FizzleDorf/ComfyUI_FizzNodes.git
cd ComfyUI_FizzNodes && pip install -r requirements.txt

Or install "FizzNodes" through ComfyUI Manager and restart. It ships with the pack, no extra dependencies beyond the usual numpy/pandas/numexpr, and it does nothing to your VRAM. If you've got ComfyUI's own text-concat options installed already you might not need this one at all - but if FizzNodes is in your pack list anyway and you're mid-graph, it's the zero-effort option.