How to Use Union Alpha

Pick your path

Union Alpha runs on OpenRouter. Everything below starts from the same place: an OpenRouter account and an API key.

Step 0: Get an API key

Every method on this page needs the same key. You only do this once.

1. Sign up or log in at openrouter.ai.
2. Open Settings → API Keys.
3. Click Create API Key and copy the value — it starts with sk-or-v1-.

Keep the key out of your source code. Put it in an environment variable (OPENROUTER_API_KEY) or your editor's settings, not in a file you might commit.

Option 1: Chat with it in the browser

Fastest way to see what the model can do — no install, no key pasting.

1. Open the model page at openrouter.ai/stealth/union-alpha.
2. Use the chat entry on that page to start a conversation.
3. Pick stealth/union-alpha as the model if the picker does not already have it selected.

Good for testing prompts, checking whether it handles your language or domain vocabulary, and comparing answers against other models before you commit.

Option 2: Call it from your own code

Union Alpha uses OpenRouter's OpenAI-compatible endpoint, so any client that speaks the OpenAI chat-completions API works. Three values are all you need:

Code examples, the full parameter reference, and tool-calling details live on the Union Alpha API page — kept there so this page stays a setup guide rather than a second copy of it.

Option 3: Use it inside your coding agent

Two of the three setups below use OpenRouter as a built-in provider, which is the supported path. The third needs a caveat — read it before you spend time on it.

OpenCode (terminal and desktop)

1. Install OpenCode: curl -fsSL https://opencode.ai/install | bash (or npm install -g opencode-ai, or brew install anomalyco/tap/opencode).
2. In your project directory, start it with opencode, then run /connect and choose OpenRouter.
3. Paste your OpenRouter API key when prompted. Run opencode auth list to confirm it was stored.
4. If stealth/union-alpha is not in the model list yet, add it to your opencode.json (project root, or ~/.config/opencode/opencode.json for all projects):

{
  "$schema": "https://opencode.ai/config.json",
  "model": "openrouter/stealth/union-alpha",
  "provider": {
    "openrouter": {
      "models": {
        "stealth/union-alpha": {}
      }
    }
  }
}

OpenCode composes model IDs as provider/model, which is why the default-model line is prefixed with openrouter/ while the key in the models map is not. Restart OpenCode after editing the config — the provider catalog is read at startup. The desktop app and the terminal share the same config and credentials, so you only connect once.

Cline (VS Code extension)

1. Open Cline's settings from the gear icon in the Cline panel.
2. Set API Provider to OpenRouter.
3. Paste your OpenRouter API key into the OpenRouter API Key field. Leave "Use custom base URL" unchecked.
4. Open the Model dropdown and search for union alpha. If it is not listed, reload the Cline panel so it refetches OpenRouter's model catalog.

Claude Code

If you still want to try it, this is the supported OpenRouter wiring — swap in the Union Alpha model:

export OPENROUTER_API_KEY="sk-or-v1-..."
export ANTHROPIC_BASE_URL="https://openrouter.ai/api"
export ANTHROPIC_AUTH_TOKEN="$OPENROUTER_API_KEY"
export ANTHROPIC_API_KEY=""          # must be explicitly empty

# route a model class to Union Alpha (experimental)
export ANTHROPIC_DEFAULT_SONNET_MODEL="stealth/union-alpha"

1. Add the variables to your shell profile (~/.zshrc or ~/.bashrc) and reload it — otherwise you will keep testing the old environment.
2. If you were previously logged into Claude Code with an Anthropic account, run /logout once and relaunch, or the cached login will conflict with the gateway credentials.
3. Start claude in your project, then run /status to verify the auth token and base URL.

Two details that trip people up: the base URL must include the scheme and stop at /api (not /api/v1), and ANTHROPIC_AUTH_TOKEN must be defined after OPENROUTER_API_KEY in the same file, or it expands to an empty string and every request fails with an auth error.

Sending an image

Union Alpha takes image input alongside text. Pass it in the standard OpenAI-compatible content array — this works the same way through the API and through any client that supports multimodal input:

{
  "model": "stealth/union-alpha",
  "messages": [{
    "role": "user",
    "content": [
      { "type": "text", "text": "Describe what is wrong with this chart." },
      { "type": "image_url", "image_url": { "url": "https://example.com/chart.png" } }
    ]
  }]
}

Troubleshooting

FAQ

Next steps