Join Strings

Building a string from parts is the most common text operation in ComfyUI after "type a prompt": positive + style, filename_base + _final, seed + a suffix. ZeugJoinStr is the smallest possible tool for it - two strings and a delimiter in, one string out - and it does that one thing without dragging in a whole text-processing dependency.

What it is

ZeugJoinStr lives in the zeug → Transform menu. Three inputs: string_a, string_b, and delimiter (all STRING, all defaulting to empty). One output, string. The result is simply string_a + delimiter + string_b. Set the delimiter to " " and "cat" + "girl" becomes "cat girl"; leave it empty and you get "catgirl" - exactly as you'd expect.

When you'd reach for it

• Assembling prompts from parts, like a base subject plus a style tag or a quality suffix.
• Building filenames: "batch" + "_" + "portrait" → "batch_portrait", ready to feed a save node's name field (chain it after ZeugIntToStr if a part is a number).
• Concatenating labels for metadata or debug output.

If you only ever need to combine two strings, this is the node. The pack also ships ZeugJoinStrList for when you have an entire list of strings to fuse, so you don't need to reach for a heavyweight text pack either way.

How it works

The implementation is transparent: string_a + delimiter + string_b. No trimming, no smart spacing, no escaping. That's worth remembering in one specific case - an empty delimiter does not insert a space, so "cat" and "dog" with an empty delimiter gives "catdog". If you want a space or a newline between parts, put it in the delimiter yourself. This is the classic "why is my filename all one word" moment, and the answer is always the delimiter.

How to install it

Part of comfyui-zeug (German for "gear" or "stuff"), a small GPL-3.0 collection by Adrian Schubek:

• ComfyUI Manager: search zeug in the Custom Nodes Manager, install ComfyUI-Zeug.
• Manual:

cd ComfyUI/custom_nodes
git clone https://github.com/adrianschubek/comfyui-zeug

Restart ComfyUI. The pack declares zero dependencies and downloads no models - it only uses torch and ComfyUI's own modules. For a string utility, that's a better deal than most.

Common issues

There's not much to troubleshoot, but the usual suspects:

• Missing separators. The empty delimiter default means a lot of first-timers get concatenated strings and blame the node. Set the delimiter to a space, comma, or whatever fits the output - that's the whole trick.
• Type expectations. Both inputs must be STRING. If one side is an int (a seed, a frame number), ComfyUI may refuse the wire - convert it first with ZeugIntToStr. This node doesn't silently coerce.
• Multiline output. There's no multiline flag on the inputs; if you want newlines between parts, put \n in the delimiter, which works fine.

It won't format, pad, or prettify. It just joins - and sometimes "just joins" is exactly what you needed.