Prompt Template

This node has an "Amazon Bedrock" repo as its home, but the name is a lie - it doesn't call any API, needs no AWS account, and works the moment ComfyUI loads. It's a string templating node, and it's genuinely useful if you build the same kind of prompt over and over.

What it does

You give it two strings: a prompt and a prompt_template. It replaces the literal placeholders {prompt} and [prompt] in the template with your prompt, and hands back the finished string. The entire implementation is two str.replace calls - there is no magic, no LLM, no model download.

So instead of retyping a wall of quality boilerplate every time, you keep a template like:

cinematic lighting, 85mm lens, shallow depth of field,
{prompt}, highly detailed, sharp focus

and wire a subject prompt into it. This matters more than it sounds: the Bedrock pack's own example workflow uses prompt templating to wrap a raw idea before sending it to an image model, and prompt structure genuinely changes results on modern models (see the KB's prompt-engineering essay - on LLM-encoded models your prompt is an instruction, and how you structure it is most of the game).

Why you'd reach for it

• Standardize a style block across a whole workflow without editing ten nodes.
• Add the same negative-ish instructions or camera framing to every generation.
• Compose an LLM-refined prompt (from the pack's Claude/Nova nodes) with your raw input before it hits an image model.

The output STRING wires into anything that takes a string - a Nova Canvas node, a Stability node, a checkpoint loader's positive prompt, whatever.

The inputs that matter

Only two, both multiline:

• prompt - the thing that varies between runs.
• prompt_template - the thing that stays the same, with {prompt} or [prompt] where the variable goes.

Both are required. If your template has no placeholder, you get the template back verbatim - check for a typo before wondering why nothing changed.

Installing it

You're installing the whole Bedrock pack to get a five-line utility, which is fair enough because the pack is small and has no heavy dependencies:

cd ComfyUI/custom_nodes
git clone https://github.com/aws-samples/comfyui-llm-node-for-amazon-bedrock.git
pip install -r comfyui-llm-node-for-amazon-bedrock/requirements.txt

Restart ComfyUI, or install via ComfyUI Manager by searching "Amazon Bedrock".

Gotchas

• Replacement is exact and case-sensitive: {Prompt} won't match {prompt}.
• It replaces all occurrences, not just the first - fine here, surprising if your template mentions {prompt} in prose.
• There's no escaping mechanism. If you want a literal {prompt} in the output, you're out of luck; nobody's building that edge case into this.

If you need two variables in one template, this pack ships the sibling node "Prompt Template with Two Inputs" for exactly that.