Interactive Playground

Run a real agent in your browser — no local install, no cloning, no CLI setup. Powered by StackBlitz WebContainers, which runs Node.js entirely in-browser.

Quick setup

Edit .env directly in the editor

Each playground has a .env file open in the editor. Replace your_gemini_key_here with your actual key, then click the terminal restart button (↺).

Get a free Gemini API key at ai.google.dev — no credit card required.

Provider	Free tier?	.env variable
Google Gemini ← recommended	✅ Yes — generous free tier	GOOGLE_API_KEY
Anthropic Claude	❌ Pay-as-you-go	ANTHROPIC_API_KEY
OpenAI	❌ Pay-as-you-go	OPENAI_API_KEY
Local Ollama	✅ Free	PROVIDER=ollama + OLLAMA_ENDPOINT (HTTPS tunnel — see below)

Note

Why not Secrets? The embedded iframe hides the Stackblitz Secrets panel. Editing .env directly in the editor is the reliable alternative — keys stay in your browser session only.

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Scenarios

Hello Agent

The simplest possible agent. One question, one answer. Start here to see the core API in action.

Set QUESTION in Secrets to ask anything you like.

Tool Integration

Agent with built-in tools. The agent uses code-execute and scratchpad-write — tools that run inside the WebContainer sandbox. No extra API keys needed.

Set TASK in Secrets to give the agent a custom challenge.

Strategy Demo

Two strategies, same task. See how reactive and plan-execute-reflect differ in steps, tokens, and style. Set STRATEGY_B to try tree-of-thought, reflexion, or adaptive.

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Using local Ollama

Caution

http://localhost:11434 does NOT work in the embed. The StackBlitz WebContainer routes localhost to its own sandbox, not your machine — and a plain LAN IP is blocked as mixed content on this HTTPS page. The only way to reach your local Ollama from the hosted playground is an HTTPS tunnel (Chrome only). Bare localhost works solely if you clone this repo and run the scenario on your own machine, outside the browser sandbox.

1. Start Ollama with CORS open (it must accept the tunnel origin):

   Mac/Linux:

   OLLAMA_ORIGINS=* ollama serve

   Windows:

   set OLLAMA_ORIGINS=* && ollama serve

2. Pull a model if you haven’t already:

   ollama pull llama3.2

3. Expose Ollama over HTTPS with a tunnel:

   cloudflared tunnel --url http://localhost:11434
   # or:  ngrok http 11434

   Copy the https://… URL it prints.

4. In the .env tab, set:

   PROVIDER        = ollama
   OLLAMA_ENDPOINT = https://YOUR-TUNNEL.trycloudflare.com
   MODEL           = llama3.2

5. Click the terminal restart button (↺) to re-run with the new env vars.

Note

This tunnel hop is the gap the v0.12 browser-extension Ollama bridge will close. Until then, the zero-setup path is a cloud key (Gemini free tier).