Union Alpha: how to use the free 262K-token model (step by step)
A free model with 262K context showed up in OpenCode and nobody claims it. The step by step to use it today: install, sign in, pick the model, send your prompt.
Read in Portuguese →A free model with 262K tokens of context showed up in OpenCode this week. Zero cost, image input, tool calling. And nobody signs their name to it. The stated window is one week, starting September 16, 2026.
Before the step by step, the minimum context that changes your decision to use it or not: the price is genuinely zero. The OpenRouter entry lists 262,144 tokens, text and image input, tool calling, and 0 on both input and output. The team behind it confirms a zero retention policy and that usage does not draw from OpenCode's Go plan. Zen's own docs list the free models that do use your data during their trial period; Union Alpha is not on that list.
Step by step
The model runs inside OpenCode, the open source coding agent that accepts any provider. Four steps.
1. Install OpenCode. Straight from the terminal, one of the official commands:
curl -fsSL https://opencode.ai/install | bash
If you prefer a desktop app, download it at opencode.ai, or use npm i -g opencode-ai, brew install anomalyco/tap/opencode.
2. Open the app and sign in to your OpenCode account. That account is the gateway every model goes through.
3. Pick Union Alpha from the model list.
4. Send your prompt. Install, open it, pick Union Alpha, and you're set. The model itself bills at zero, and your usage does not touch the Go plan.
What could change your mind
The window is short and explicitly stated: OpenCode wrote "free for the next week" on September 16. There is no official deadline beyond that sentence, and stealth models tend to disappear without notice when the test ends.
An anonymous author is not idle curiosity. Without knowing who built the model, you do not know where your data sits, how long the model will exist, or who to complain to when an answer comes back wrong. The current package promises zero retention, which is a comfort for testing and not a contract for production.
Where to check
- OpenCode Zen docs, where the model is listed: https://opencode.ai/docs/zen
- Model entry on OpenRouter: https://openrouter.ai/stealth/union-alpha
- Free window announcement: https://x.com/opencode/status/2100236430890991782
- Original Cloudflare description (capture from September 16, 2026): https://web.archive.org/web/20260917005232/https://developers.cloudflare.com/ai/models/stealth/union-alpha/