Action Prompt provides a dead simple way to way to organize, preview, and render prompts within a Ruby on Rails App. Because this leverages the ApplicationController, you're able to leverage all the bells an whistles

This draws heavy inspiration from ActionMailer::Preview.

As LLMs have become ubiquitous in web applications, we've that prompts intended for Claude or GPT have become scattered throughout our codebase or buried within objects. Often, these prompts were built inline through string manipulation. Our thinking was two-fold, 1) Let's come up with a simple pattern for organizing and rendering these prompts, and 2) Let's make them easy to review.

Install the gem with gem "action_prompt".

1. Create a template for organizing your prompts located at your app/prompts. For example, you might create app/prompts/hello_world.text.erb and give it the following content:

   You are a helpful assistant who replies with, "<%= @message >"
   

2. Create a preview class. These live in test/prompts and they inherit from ActionPrompt::Preview. For example, you might create tests/prompts/hello_world_preview.rb and give it the following context:

   class HelloWorldPreview < ActionPrompt::Preview
    def example_prompt
      render "hello_world", locals: {message: "Hello, world!"}
    end
   end

3. Next, start up your rails server (rails s) and navigate to http://localhost:3000/action_prompt/previews. You'll see a list of your prompts that resembles the following:

   

   You can now preview your prompts.

1. Assume you've followed step one above, and you have a prompt located at app/prompts/hello_world.text.erb.

2. You can now render this anywhere in your codebase with the following:

   ActionPrompt::Renderer.new.render("hello_world", locals: {message: "Now we're cooking"})
   # You are a helpful assistant who replies with, "Now we're cooking"

Under the hood, ActionPrompt is leveraging the app's ApplicationController. That means you can use the full magic of ActionView which includes

• Rendering partials.
• Rendering json with Jbuilder
• Using route helpers, i.e. posts_url
• ...and more!

The gem is available as open source under the terms of the MIT License.