Set String Extra

Set String Extra is the most flexible member of the pack's extras family: it writes an arbitrary text key → value pair into the metadata "extras" that get embedded in the A1111 infotext when you save with Image Saver. Floats and ints get their own specialized nodes; this one accepts anything that fits in a string.

The float and int versions exist because numbers come back as typed values you can drive a workflow with. Strings are different: you'll reach for this node when the thing you want to persist is textual and you don't need it back as a number. The obvious use is provenance and notes - a model recipe, a batch label, a comment to your future self about why this pass used that setting. But there are real functional uses too: storing a tag list before caption writing, persisting a filename stem or a folder name, or writing a human-readable summary line into metadata that other tools can read without touching the workflow.

Inputs and outputs

• key - the parameter line key.
• value - the string to store. This is a plain text field; there's no template or variable expansion in here, so what you type is literally what gets saved.
• extras (optional) - the incoming extras bundle to merge into.

Output is the merged extras bundle, chainable with the other Set nodes and consumable by Image Info Context.

Because it's a free-form string, there's one extra responsibility on you: the value becomes a single parameter line in the infotext, so keep it line-friendly. Multi-line prose is legal but it'll make the metadata ugly and can confuse parsers downstream. A short label, not a diary entry.

How it fits the wider picture

Same machinery as the rest of the family - extras merge into image_info.extras (duplicate keys overwritten), Image Saver serializes them into the file, Image Reader rebuilds them on load, and the matching Get String Extra node returns your value as a string ready to wire anywhere a string is accepted (a filename builder, a caption node, a prompt field). The pack's Prompt Template node even does $key replacement against extras, so a string extra can be a slot in a template - write a value once, and every template that references $key picks it up.

Install

Standard pack install:

cd ComfyUI/custom_nodes
git clone https://github.com/kinorax/comfyui-info-prompt-toolkit.git
cd comfyui-info-prompt-toolkit
pip install -r requirements.txt

Or ComfyUI Manager → search "ComfyUI-Info-Prompt-Toolkit" → install → restart. No models, no extra dependencies.

Where people get burned

The recurring theme applies here hardest: extras only survive if a pack saver writes the file, and duplicate keys silently overwrite. With strings there's also no validation - a typo in a key means a silent dead entry, and a newline in a value can mangle the infotext format. If you're storing structured data, keep it to a single line and make the key count. And when you reload, remember you get a string out: if it's secretly a number you want to compute with, use the typed int/float extras instead, because the Get node won't convert it for you.