Llama 3.1 8B Prompt Enhancer

Half the "why is my output garbage" posts on r/comfyui are really "why is my prompt garbage." This node is Runware's answer: a Llama 3.1 8B running in the cloud that takes your rough idea and returns an expanded, better-written version. It's not a model node - it's a text utility that sits upstream of one. Write "cat astronaut on a bike, cinematic," get back something with lighting, lens, mood, and composition details worth feeding to a real generator.

The output is plain text (STRING), which is exactly why it's useful: wire it straight into the positivePrompt of any other node in this pack - Krea, LTX, Kling, whatever - or into a local model's prompt. It runs as a promptEnhance task on Runware's cloud, so it needs the same API key as everything else, and each call is a (tiny) charge.

How it works

The node builds a request for model AIR runware:llama-3-1-8b@prompt-enhancer and sends it over REST through the runware-sdk, then returns the enhanced text as a single text output. Inputs are minimal:

• prompt - required, the raw idea. Multiline, so paste whatever you've got.
• promptMaxLength + promptMaxLength_value - a gated control, off by default. Flip it on to cap the enhanced prompt's length; the value defaults to 12 (words, roughly - think "keep it short").
• promptVersions - how many variations to generate, default 1. Ask for a couple if you want options to choose between.

Where it fits

The cleanest workflow is a three-node chain: this node → your generator. It's also a nice way to normalize prompts before batch work, so every generation in a series shares the same descriptive texture instead of whatever you typed at 2am. If you're testing, remember promptVersions multiplies the API calls, and the node's printed cost line will remind you.

Installing it

Part of the Runware/ComfyUI-Runware pack, installed once for every node:

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

Restart, then set your key in ComfyUI Settings → Runware API key, via RUNWARE_API_KEY, or with runware auth login.

Where people get burned

Expecting it to understand your niche. Llama 3.1 8B is a good general enhancer, not a style oracle - if you're doing a highly specific art style or character, feed it enough context in the raw prompt or it'll polish the vagueness into fancier vagueness. Also don't leave promptVersions at 10 by reflex; each version is a separate call, and on a cloud service "separate call" means "separate line item."