New Stealth Coding Model Union Alpha Is Free on OpenCode and OpenRouter
Union Alpha appeared on OpenRouter and OpenCode on 16 September 2026 as an anonymous stealth coding model, free during a preview of roughly one week. The verified specification reads 262,144 tokens of context, 131,072 tokens of maximum output, text and image input, and tool calling limited to auto mode. OpenCode’s documentation claims a zero-retention policy while OpenRouter’s disclaimer says prompts may be retained, a contradiction on the same model. OpenCode’s routing table places Union Alpha on the Anthropic Messages API surface alongside eleven Claude models and four Qwen models, which narrows the field of possible builders without naming one.
