Rails AI Chat

A ChatGPT-style chat interface built with Rails 8 and the ruby_llm gem. Supports multiple LLM providers with real-time streaming responses.

Demo

You can it live in railschat.org.

Features

• Real-time streaming — Server-Sent Events (SSE) for token-by-token response streaming
• Multiple LLM providers — Gemini (free tier), OpenAI, and Mistral
• Bring Your Own Key (BYOK) — OpenAI and Mistral keys are stored in browser localStorage and sent per-request (never persisted server-side)
• Session-based isolation — Each browser session gets its own conversation history, no authentication required
• Model switching — Change models mid-conversation from the input area
• Markdown rendering — Assistant responses are rendered as rich markdown (headings, code blocks, lists, etc.)
• Dark mode — Automatic detection of system preference with dark/light theme support
• Copy to clipboard — One-click copying of assistant messages
• Retry messages — Regenerate the last assistant response
• Abort streaming — Cancel an in-progress response at any time
• Async chat titles — Conversation titles are generated automatically in the background
• Mobile friendly — Responsive master-detail layout

Tech Stack

• Ruby 3.3, Rails 8, SQLite
• Hotwire (Turbo + Stimulus)
• Tailwind CSS v4
• Propshaft, importmap-rails

Getting Started

Prerequisites

• Ruby 3.3+
• A Gemini API key (free tier)

Setup

git clone <repo-url>
cd rails_ai
bundle install
bin/rails db:setup

Create a .env file in the project root:

GEMINI_API_KEY=your_gemini_api_key_here

Run

bin/dev

This starts the Rails server and Tailwind CSS watcher via foreman.

Architecture

• Master-detail layout — Sidebar with conversation list + main chat area, both always visible
• SSE streaming — MessagesController#create uses ActionController::Live to stream LLM responses. The client reads via fetch + ReadableStream (not EventSource) to allow POST requests
• Stimulus controllers — chat_controller.js handles streaming and model switching; api_keys_controller.js manages BYOK key storage
• Session isolation — Conversations scoped by session[:visitor_id], assigned in ApplicationController

Acknowledgements

This software was made possible using open source software, so credits to the contributors of all the libraries in the Gemfile. Special thanks to the contributors of Ruby on Rails, Kamal and Ruby LLM.