GPT-5-Nano is the smallest and fastest variant in the GPT-5 system, optimized for developer tools, rapid interactions, and ultra-low latency environments. While limited in reasoning depth compared to its larger...
Model details →OpenAI: GPT-5 Nano vs Union Alpha
OpenAI: GPT-5 Nano and Union Alpha are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
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 is a stealth model....
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5 Nano | Union Alpha | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 400K | 262K | 🏆 OpenAI: GPT-5 Nano |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $0.05 | $0.00 | 🏆 Union Alpha |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $0.40 | $0.00 | 🏆 Union Alpha |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | Yes | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | Yes | — | 🏆 OpenAI: GPT-5 Nano |
Frequently asked questions
Is OpenAI: GPT-5 Nano better than Union Alpha?
OpenAI: GPT-5 Nano and Union Alpha are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
What's the price difference between OpenAI: GPT-5 Nano and Union Alpha?
Input: $0.05 vs $0.00 per 1M tokens. Output: $0.40 vs $0.00 per 1M tokens.
What context windows do OpenAI: GPT-5 Nano and Union Alpha support?
OpenAI: GPT-5 Nano supports up to 400K tokens. Union Alpha supports up to 262K tokens.
Do both OpenAI: GPT-5 Nano and Union Alpha support tool calling?
OpenAI: GPT-5 Nano: yes. Union Alpha: yes.