← Model indexMODEL PROFILE / grok-4-fast

xAI / current

Grok 4 Fast

xAI's fast Grok 4 tier with a very large reasoning context window.

Context2M
ModalityText · Image
AccessAPI
ReasoningConfigurable

Where it fits.

Combines Grok 4 reasoning depth with a two-million-token context aimed at speed-sensitive long-document work. A Grok 4 variant pairing configurable reasoning with a two-million-token context, positioned between the flagship 4.3 tier and lighter utility models.

02

Core capabilities

  • 2M-token context for long reasoning sessions
  • Configurable reasoning effort
  • Optional server-side Web and X search
  • Function calling and structured outputs
03

Best-fit workflows

  • Long-document Q&A
  • Real-time information tasks
  • Cost-sensitive reasoning
04 / OPERATIONS

From evaluation
to production.

Deployment notes

Use for long inputs where latency still matters. Keep search opt-in per workflow, validate citations, and test recall at several context positions before trusting full-window fills.

Watch before choosing

Search-enabled answers need citation displays and defenses against untrusted retrieved content. Very large contexts do not guarantee uniform recall; retrieval and positional probes remain necessary.

05

Family & versions

Specifications and positioning checked against provider documentation.

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