Union Alpha vs Xiaomi MiMo-V2.5
Both are Alpha-line stealth models, but MiMo-V2.5 has been revealed as Xiaomi's model and is paid; Union Alpha is still anonymous and free, with a smaller context window but image input.
Quick verdict
Pick Union Alpha while it is free and when image input matters. Pick MiMo-V2.5 when you want the larger 1M context with a disclosed vendor — and remember it was once the free stealth model of the line.
Side-by-side comparison
| Field | Union Alpha | Xiaomi MiMo-V2.5 |
|---|---|---|
| Provider | Undisclosed (stealth) | Xiaomi |
| Context window | 262K tokens | 1.05M tokens |
| Input / 1M | $0 | $0.140 |
| Output / 1M | $0 | $0.280 |
| Modalities | Text, Vision | Text, Vision, Audio, Video |
| Best for | Agents, Long Context, Multimodal, Free | Long Context, Budget, Multimodal |
Cost estimates
| Workload | Input | Output | Union Alpha | Xiaomi MiMo-V2.5 |
|---|---|---|---|---|
| Quick test | 20,000 | 5,000 | $0 | $0.004 |
| Product chat month | 500,000 | 125,000 | $0 | $0.105 |
| Document batch | 5,000,000 | 1,000,000 | $0 | $0.980 |
Estimates use list input/output prices and exclude cache discounts, provider surcharges and tool fees.
Choose Union Alpha if
- ✓You want the current free window and can tolerate an anonymous endpoint
- ✓You are sending images alongside text
- ✓You are comparing the Alpha line and want to test all three
Choose Xiaomi MiMo-V2.5 if
- ✓You need a 1M-token window rather than 256K
- ✓You need a vendor with a name, terms and published data handling
- ✓You need pricing and availability you can commit to
FAQ
Is Union Alpha cheaper than Xiaomi MiMo-V2.5?
Union Alpha costs $0 input and $0 output per 1M tokens. Xiaomi MiMo-V2.5 costs $0.140 input and $0.280 output per 1M tokens.
Which model has the larger context window?
Union Alpha offers 262K tokens; Xiaomi MiMo-V2.5 offers 1.05M tokens. Provider-specific limits can vary by route.
Which one should I choose?
Pick Union Alpha while it is free and when image input matters. Pick MiMo-V2.5 when you want the larger 1M context with a disclosed vendor — and remember it was once the free stealth model of the line.
Pricing and context data are based on a 2026-09-17 snapshot. Provider limits and pricing can change; verify on OpenRouter before production.