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This stealth model was developed and operated by Unbiased, revealed to be Unbiased ParetoOpens in new tab. Prompts and completions for this model may have been retained by the provider but are not used for training; all other use is governed by the Stealth Model TermsOpens in new tab.

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Union Alpha

stealth/union-alpha

Union Alpha is a multimodal model built for research, coding, and agentic workflows, while delivering frontier-level performance across a broad range of general-purpose tasks.

Union Alpha was a stealth model, revealed to be ParetoOpens in new tab by Unbiased. OpenRouter routed requests to it and was not its developer, owner, or provider. Prompts and completions may be retained by the provider but are not used for training; all other use is governed by the Stealth Model TermsOpens in new tab. The free stealth period has ended; use Pareto at https://openrouter.ai/unbiased/paretoOpens in new tab.

Modalities
Context
262K
Released
Sep 16, 2026