How to Set Up NVIDIA's Free Nemotron 3 Ultra Model for Zero-Cost Coding Agents
A step-by-step guide to using NVIDIA's open-source, 550B-parameter model with a free API tier for agentic coding workflows, eliminating costs for tools like Codex or Claude Code.
Practical Summary
This tutorial shows how to access and configure NVIDIA's Nemotron 3 Ultra model via OpenRouter's free tier and the 'opencode' tool. It provides a zero-cost alternative for running coding agents that require large context windows, suitable for testing and development, with clear steps and an honest discussion of limitations.
Why It Matters
For teams and individual developers, this workflow demonstrates a viable path to significantly reduce AI tool expenses by leveraging a free, powerful open-source model. It directly addresses cost optimization without sacrificing core functionality for coding tasks, though production use may require paid tiers due to rate limits.
Step 1: Obtain a Free API Key from OpenRouter
Visit the OpenRouter website and sign in with your Google or GitHub account. Navigate to the 'Keys' page and create a new API key. Copy this key for later use. The model 'nvidia/nemotron-3-ultra-550b-a55b:free' is available at $0 cost on OpenRouter's free tier, which is rate-limited and requires no credit card. An alternative is the NVIDIA developer program for free prototyping access.
Step 2: Install the 'opencode' Tool
Install the 'opencode' command-line tool using a one-liner command. Open your terminal and run: curl -fsSL https://t.co/N6ECx2J36W | bash. After installation, verify it by running: opencode --version.
Step 3: Connect OpenRouter to opencode
Launch 'opencode' in your terminal. Inside its text user interface (TUI), run the command: /connect. Search for 'OpenRouter' and paste the API key you obtained in Step 1. The key will be stored in ~/.local/share/opencode/auth.json.
Step 4: Select the Nemotron 3 Ultra Model
opencode often preloads many OpenRouter models. Run /models and select 'Nemotron 3 Ultra' from the list. If it doesn't appear, manually add it by editing the configuration file at ~/.config/opencode/opencode.json. Add the following JSON block and then restart opencode: { "model": "openrouter/nvidia/nemotron-3-ultra-550b-a55b:free", "provider": { "openrouter": { "models": { "nvidia/nemotron-3-ultra-550b-a55b:free": {} } } } }