Active Agent

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Getting Started ​

Build AI agents with Rails in minutes. This guide covers installation, configuration, and creating your first agent.

Prerequisites ​

  • Ruby 3.0+
  • Rails 7.0+
  • API key for your chosen provider (OpenAI, Anthropic, Ollama, or RubyLLM)

Installation ​

Add activeagent and your provider gem:

bash
bundle add activeagent

Add your provider gem:

bash
bundle add openai
bash
bundle add anthropic
bash
bundle add openai  # Ollama uses OpenAI-compatible API
bash
bundle add openai  # OpenRouter uses OpenAI-compatible API
bash
bundle add ruby_llm --version "~> 1.0"  # Unified API for 15+ providers

Run the install generator:

bash
rails generate active_agent:install

This creates:

  • config/active_agent.yml - Provider configuration
  • app/agents/application_agent.rb - Base agent class

Configuration ​

Configure your provider in config/active_agent.yml:

yaml
openai:
  service: "OpenAI"
  access_token: <%= ENV['OPENAI_API_KEY'] %>
  model: "gpt-4o-mini"

See Configuration for environment-specific settings, multiple providers, and advanced options.

Quick Start ​

Test your setup with direct generation:

ruby
response = ApplicationAgent.prompt(message: "Hello, world!").generate_now
puts response.message
# => "Hello! How can I help you today?"

This is perfect for testing your setup or quick experiments. For production apps, define custom agents with actions (shown below).

Your First Agent ​

Generate an Agent ​

Create an agent with the Rails generator:

bash
rails generate active_agent:agent SupportAgent help

This creates:

  • app/agents/support_agent.rb - Agent class with actions
  • app/views/agents/support/help.text.erb - View template

Define the Agent ​

The generated agent defines actions as public methods:

ruby
class SupportAgent < ApplicationAgent
  def help
    @message = params[:message]
    @user_id = params[:user_id]
    prompt
  end
end

Create a message template at app/views/agents/support/help.text.erb:

erb
Help Request from User <%= @user_id %>
=====================================

The user needs assistance with: <%= @message %>

Please provide a helpful response.

Use Your Agent ​

ruby
response = SupportAgent.with(
  user_id: 123,
  message: "How do I reset my password?"
).help.generate_now

puts response.message
# => "To reset your password, follow these steps..."

Core Concepts ​

Three Invocation Patterns ​

ActiveAgent supports three ways to invoke agents:

1. Direct (testing/prototyping):

ruby
ApplicationAgent.prompt(message: "Hello").generate_now

2. Parameterized (pass data to actions):

ruby
SupportAgent.with(user_id: 123, message: "Need help").help.generate_now

3. Action-based (production pattern):

ruby
class SupportAgent < ApplicationAgent
  def help
    prompt(message: "User #{params[:user_id]} needs: #{params[:message]}")
  end
end

Instructions ​

Guide agent behavior with system instructions. Define them three ways:

In generate_with configuration:

ruby
class ApplicationAgent < ActiveAgent::Base
  generate_with :openai, instructions: "You are a helpful assistant."
end

In an instructions.text template:

erb
You are a support agent helping users with their questions.
Be concise, friendly, and provide clear solutions.

Inline in the action:

ruby
def help
  prompt(instructions: "Answer the user's question clearly and briefly")
end

See Instructions for complete details.

Execution ​

Generate responses synchronously or asynchronously:

ruby
# Synchronous
response = agent.generate_now
puts response.message

# Asynchronous (via Active Job)
agent.generate_later(wait: 5.minutes)

See Generation for background jobs, callbacks, and response objects.

Next Steps ​

Core Features:

  • Agents - Actions, callbacks, concerns, streaming
  • Messages - Images, documents, conversation history
  • Tools - Function calling and MCP integration
  • Structured Output - Parse JSON with schemas
  • Embeddings - Vector generation for semantic search
  • Providers - OpenAI, Anthropic, Ollama, OpenRouter, RubyLLM

Framework: