openui-forge-elixir

OpenUI Forge — Elixir

Build generative UI apps with a React frontend + Elixir Phoenix backend. Streams OpenAI API responses directly to the browser as SSE using Plug.Conn.send_chunked/2 and the Req HTTP client's streaming :into collector.

Activation Triggers

• "openui elixir", "openui phoenix", "openui elixir backend"
• "generative ui elixir", "elixir streaming ui backend", "phoenix sse openui"

Prerequisites

• Node.js >= 22 (24 LTS recommended) + React >= 18.3.1 (19+ recommended) (frontend)
• Elixir >= 1.15 with Erlang/OTP 25+ (Phoenix 1.8 baseline)
• Phoenix ~> 1.8 (current stable; 1.8.8 as of June 2026)
• OPENAI_API_KEY environment variable set

Quick Start

1. Create the React frontend and install OpenUI deps:

npm install @openuidev/react-ui @openuidev/react-headless @openuidev/react-lang lucide-react zod

1. Generate the system prompt into the Phoenix app's priv/:

npx @openuidev/cli generate ./src/lib/library.ts --out backend/priv/system-prompt.txt

1. Create the Phoenix backend (see Full Code below)
2. Run: mix deps.get && mix phx.server on :4000, frontend on :3000

Full Code

Backend: backend/mix.exs (deps)

defp deps do
  [
    {:phoenix, "~> 1.8.0"},
    {:bandit, "~> 1.0"},      # HTTP server (Phoenix 1.8 default)
    {:jason, "~> 1.4"},       # JSON encode/decode
    {:req, "~> 0.6"},         # HTTP client with streaming :into (v0.6.2+)
    {:cors_plug, "~> 3.0"}    # explicit-origin CORS
  ]
end

Backend: load the system prompt once at startup

Read priv/system-prompt.txt a single time and cache it in :persistent_term. Call OpenuiBackend.load_system_prompt!/0 from your Application.start/2 callback before the endpoint child starts.

# lib/openui_backend.ex
defmodule OpenuiBackend do
  @key {__MODULE__, :system_prompt}

  def load_system_prompt! do
    path = Application.app_dir(:openui_backend, "priv/system-prompt.txt")

    case File.read(path) do
      {:ok, contents} ->
        :persistent_term.put(@key, contents)
        :ok

      {:error, reason} ->
        raise "failed to read #{path}: #{:file.format_error(reason)}"
    end
  end

  def system_prompt, do: :persistent_term.get(@key)
end