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Grok 3 Fast Beta

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Grok 3 Fast Beta is the speed-optimized variant of xAI's Grok 3 model. It delivers lower latency inference while keeping the same Grok 3 training foundation, with a context window of 131.1K tokens.

Tool Use
index.ts
import { streamText } from 'ai'


const result = streamText({
  model: 'xai/grok-3-fast',
  prompt: 'Why is the sky blue?'
})

What To Consider When Choosing a Provider

  • Configuration: Grok 3 Fast Beta trades some reasoning depth for lower latency. Benchmark against the full Grok 3 on your specific task to determine whether the speed gain justifies any quality difference.
  • Configuration: For chat interfaces, coding assistants, and agent loops where sub-second responsiveness matters, Grok 3 Fast Beta is typically the right starting point in the Grok 3 family.
  • Zero Data Retention: AI Gateway does not currently support Zero Data Retention for this model. See the documentation for models that support ZDR.
  • Authentication: AI Gateway authenticates requests using an API key or OIDC token. You do not need to manage provider credentials directly.

When to Use Grok 3 Fast Beta

Best For

  • Interactive chat applications: Response latency directly impacts user engagement and satisfaction
  • Coding assistants and IDE integrations: That require fast completions during active development workflows
  • Agentic tool-calling loops: Each step needs to complete quickly to keep total workflow time reasonable
  • Real-time content generation: For applications that stream responses to users as they are produced
  • Production APIs: Serving end users who expect near-instant responses

Consider Alternatives When

  • Maximum reasoning depth required: For complex math, science, or multi-step analysis, use the full Grok 3 model
  • Cost is the primary constraint: When tasks are straightforward enough for a smaller model, Grok 3 Mini or Grok 3 Mini Fast may suffice
  • Hard reasoning tasks: Grok 4 models report higher scores than Grok 3 Fast on difficult benchmarks
  • Simple text classification or extraction: Even Grok 3 Mini Fast would be overprovisioned

Conclusion

Grok 3 Fast Beta occupies the practical middle ground in the Grok 3 family: fast enough for interactive applications, capable enough for serious reasoning tasks. It's the default choice for production workloads that need both quality and responsiveness from an xAI model.

Frequently Asked Questions

  • How much faster is Grok 3 Fast Beta compared to Grok 3?

    Grok 3 Fast Beta is optimized for lower latency inference. The exact speed improvement depends on prompt complexity and output length, but it's designed for interactive use cases where the full Grok 3 may feel too slow.

  • Does Grok 3 Fast Beta have the same context window as Grok 3?

    Yes, both share a context window of 131.1K tokens.

  • When should I choose Grok 3 Fast Beta over Grok 3 Mini?

    Grok 3 Fast Beta retains more of the full Grok 3 reasoning capability, while Grok 3 Mini is a smaller, more cost-efficient model. Choose Grok 3 Fast Beta when task quality is important but you also need low latency.

  • What does Grok 3 Fast Beta cost?

    This page lists the current rates. Multiple providers can serve Grok 3 Fast Beta, so AI Gateway surfaces live pricing rather than a single fixed figure.

  • How do I authenticate with Grok 3 Fast Beta through Vercel AI Gateway?

    Use your Vercel AI Gateway API key with xai/grok-3-fast as the model identifier. No separate xAI account is needed for gateway-managed access.

  • Is Grok 3 Fast Beta suitable for streaming responses?

    Yes. Grok 3 Fast Beta's speed optimization makes it well-suited for streaming responses in chat interfaces and real-time applications.

  • Does Vercel AI Gateway support Zero Data Retention for Grok 3 Fast Beta?

    Zero Data Retention is not currently available for this model. ZDR on AI Gateway applies to direct gateway requests; BYOK flows aren't covered. See https://vercel.com/docs/ai-gateway/capabilities/zdr for details.