Prompt Builder 🔀

The README pitches this one as "LEGO for prompts," and that's about right - you snap together a prefix, some content, and a suffix into one prompt. It's the simplest of the pack's assembly nodes: three text boxes, joined in order. Where it earns its keep over a plain concatenate is the second output, which hands the middle back to you untouched.

Prompt Builder is part of WildPromptor by 1038lab (also the author of the ComfyUI-RMBG masking pack).

How it works

You put a fixed opener in prefix (your quality tags, a style anchor, whatever you always want in front), the variable part in content, and a closer in suffix. The node concatenates prefix + content + suffix into a finished prompt. That's the mechanism. Nothing magic - but the split into three named regions makes intent obvious and easy to rewire.

The inputs and outputs that matter

All three inputs - prefix, content, suffix - are optional multiline text. Fill what you need.

There are two outputs, and the second is the reason to use this node:

• prompt - a STRING list: the full prefix + content + suffix, ready for a CLIP Text Encode
• content_only - a single STRING carrying just the middle, unwrapped

That content_only passthrough is the useful trick. Say you've wrapped a generated subject in a fixed quality prefix/suffix for image generation, but you also want to feed the bare subject somewhere else - a filename, a caption, a second prompt with different framing. Instead of rebuilding it, you tap content_only. It keeps the raw middle available without you maintaining it in two places.

When you'd reach for it vs. Prompt Concat

Prompt Concat is the many-slot mixer for stitching several list-node fragments together. Prompt Builder is the two-bookend wrapper for a single content stream you want framed. Different jobs. If all you're doing is "always put these tags before and after whatever I'm generating," Builder is the cleaner, smaller node - and you get the unwrapped copy for free.

A structural aside worth keeping in mind: the prefix→content→suffix shape lines up with how modern encoders like a prompt organized - a stable frame around a variable core. Just keep each region lean; a bloated prefix of quality words does little on current models and eats attention on LLM-encoded ones.

Installing it

ComfyUI Manager: search ComfyUI-WildPromptor, install, restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/1038lab/ComfyUI-WildPromptor

then restart. It's under 🧪AILab/🧿WildPromptor. No downloads needed.

Common issues

• Output has odd spacing where regions meet - the node joins your text as given; add or trim trailing spaces/commas in the boxes so the seam reads cleanly.
• I wanted just the middle and got the whole thing - you grabbed the wrong output. prompt is the wrapped version; content_only is the bare middle.
• prompt is a list but my downstream wants a single string - that's expected for batch flows; if you need a scalar, pull from content_only or route through a node that collapses the list.