Your prompt will be processed by a meta-model and routed to one of dozens of models (see below), optimizing for the best possible output. To see which model was used, visit [Activity](/activity), or read the `model` attribute of the respon…
Model details →Auto Router vs xAI: Grok 4 Fast
Auto Router wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
Grok 4 Fast is xAI's latest multimodal model with SOTA cost-efficiency and a 2M token context window. It comes in two flavors: non-reasoning and reasoning. Read more about the model on xAI's [news post](http://x.ai/news/grok-4-fast). Reaso…
Model details →Side-by-side comparison
| Capability | Auto Router | xAI: Grok 4 Fast | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 2M | 2M | Tie |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $-1000000.00 | $0.20 | 🏆 Auto Router |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $-1000000.00 | $0.50 | 🏆 Auto Router |
| 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 | Yes | Tie |
Frequently asked questions
Is Auto Router better than xAI: Grok 4 Fast?
Auto Router wins on 2 of 6 axes — pricing and capability skew in its favour for most workloads.
What's the price difference between Auto Router and xAI: Grok 4 Fast?
Input: $-1000000.00 vs $0.20 per 1M tokens. Output: $-1000000.00 vs $0.50 per 1M tokens.
What context windows do Auto Router and xAI: Grok 4 Fast support?
Auto Router supports up to 2M tokens. xAI: Grok 4 Fast supports up to 2M tokens.
Do both Auto Router and xAI: Grok 4 Fast support tool calling?
Auto Router: yes. xAI: Grok 4 Fast: yes.