Deep Agents Showcase

A full-stack chat application that showcases LangChain Deep Agents with a FastAPI backend and a React frontend built with assistant-ui. The backend streams responses over SSE; the frontend provides a chat UI with tool calls, reasoning, and file previews.

What's in this repo

• apps/api — FastAPI service that runs a Deep Agent (OpenAI), exposes /api/chat and /api/chat/stream, and streams via Server-Sent Events.
• apps/web — Vite + React app using assistant-ui’s LocalRuntime and a custom streaming adapter for the API.

Tech stack

Layer	Stack
Backend	Python 3.11+, FastAPI, LangChain, Deep Agents, OpenAI
Frontend	React 18, Vite 7, TypeScript, Tailwind CSS, assistant-ui
Tooling	pnpm (workspace), uv (Python), Docker Compose

Prerequisites

• Python 3.11+ (and uv recommended)
• Node.js 20+
• pnpm (npm install -g pnpm)
• OpenAI API key (for the agent)

Setup

1. Clone and install dependencies

git clone https://github.com/bodanLabs/deepagents-showcase.git
cd deepagents-showcase

2. Backend (API)

cd apps/api

Create environment file from the example and add your OpenAI key:

cp .env.example .env

Edit apps/api/.env and set at least:

• OPENAI_API_KEY — your OpenAI API key (required)
• OPENAI_MODEL — e.g. openai:gpt-4o-mini (optional, has default)
• CORS_ORIGINS — e.g. http://localhost:5173 for local web dev

Create a virtual environment and install the API:

uv venv
source .venv/bin/activate   # Windows: .venv\Scripts\activate
uv pip install -e ".[dev]"

Run the API:

uvicorn app.main:app --reload --host 0.0.0.0 --port 8000

API will be at http://localhost:8000. Health check: http://localhost:8000/health.

3. Frontend (Web)

In a new terminal, from the repo root:

pnpm install
pnpm dev:web

Or from the web app directory:

cd apps/web
pnpm install
pnpm dev

App will be at http://localhost:5173. Ensure the API is running and that CORS_ORIGINS in apps/api/.env includes http://localhost:5173.

Optional: copy apps/web/.env.example to apps/web/.env if you need to change the API URL (e.g. for a different host/port).

---

Running with Docker

From the repo root, create apps/api/.env as above (Docker Compose uses it), then:

docker-compose up --build

• API: http://localhost:8000
• Web: http://localhost:5173

The web container is built with the API URL pointing at the API service.

Environment variables

Backend (apps/api/.env)

Variable	Description	Example
OPENAI_API_KEY	OpenAI API key (required)	sk-...
OPENAI_MODEL	Model used by the agent	openai:gpt-4o-mini
CORS_ORIGINS	Allowed origins (comma-separated)	http://localhost:5173
LOG_LEVEL	Logging level	INFO

Frontend (apps/web/.env)

Optional. Use if the API is not at http://localhost:8000 (e.g. different port or host). See apps/web/.env.example.

Project structure

deepagents-showcase/
├── apps/
│   ├── api/                 # FastAPI + Deep Agents
│   │   ├── app/
│   │   │   ├── core/        # config, logging
│   │   │   ├── schemas/     # request/response models
│   │   │   └── services/    # chat, agent
│   │   ├── tests/
│   │   ├── .env.example
│   │   └── pyproject.toml
│   └── web/                 # Vite + React + assistant-ui
│       ├── src/
│       │   ├── components/  # assistant-ui components
│       │   ├── lib/         # SSE/streaming adapter
│       │   └── runtime/     # LocalRuntimeProvider
│       ├── .env.example
│       └── package.json
├── docker-compose.yml
├── package.json             # pnpm workspace root
└── README.md