Random Prompt ♾️Mixlab

You've got a list of options - thirty types of playground equipment, say - and you want the model to riff through them without you hand-editing the prompt each run. RandomPrompt takes a list, randomly picks from it, and drops the pick into a fixed template. It's the quick way to spin up variety, or to generate a whole batch of themed prompts in one shot.

How it works

You give it two blocks of text. The mutable_prompt is your pool of options, one per line. The immutable_prompt is the fixed scaffolding that every prompt shares - style, format, quality tags - with a placeholder (the pack uses backticks, ``) marking where the random pick gets slotted in. Each run, the node samples from your pool and fills the template. Change the seed and you get different picks; it's the same mechanism as any randomizer, just aimed at prompt text.

Look at the defaults and it clicks: the mutable list is playground equipment ("Swing", "Slide", "Sandbox"...), and the immutable is `sticker, Cartoon, - so you get "sticker, Cartoon, Swing", "sticker, Cartoon, Slide", and so on. Same style, rotating subject.

The inputs that matter

• mutable_prompt - your options, one per line. This is the pool it draws from.
• immutable_prompt - the constant wrapper. Put your shared style/quality here and mark the insertion point with the backtick placeholder.
• max_count - how many prompts to produce (up to 1000). This is what makes it a batch generator, not a single-pick node - set it to 9 and you get nine prompts out.
• random_sample - enable shuffles/picks randomly; disable walks the list in order instead, which is what you want when you'd rather cover every option deterministically than gamble.
• seed (optional) - locks the randomness. Same seed, same set of prompts, so you can reproduce a batch you liked.

Output is a STRING list - a batch of finished prompts. Feed it into whatever consumes a list of prompts (a batch prompt setup, or one at a time into your encoder).

Installing it

Get the pack via ComfyUI Manager (search mixlab, install comfyui-mixlab-nodes, restart), or clone it:

cd ComfyUI/custom_nodes
git clone https://github.com/shadowcz007/comfyui-mixlab-nodes

then install requirements and restart. No model download for this one - it's pure text wrangling.

Common snags

• Nothing gets swapped in. You dropped the placeholder from immutable_prompt. The node needs the backtick marker to know where the random pick goes; without it you just get the fixed text repeated.
• Same prompt every time. Either random_sample is disable, or your seed is fixed and your pool is tiny. Enable random sampling and vary the seed.
• Fewer prompts than expected. max_count caps the output. Also, with random_sample on, picks can repeat - it samples, it doesn't guarantee unique coverage. If you want every option exactly once, use disable to walk the list in order.
• This node pairs naturally with Mixlab's batch-prompt / workflow-to-app features, which is where the "generate 9 variations and render them all" pattern really pays off.