Model · xAI

Grok 4 Fast

Cost-efficient Grok 4 family with 2M context and reasoning/non-reasoning modes.

Pricing

Model Overview

Tracked token-pricing fields for this model family. Empty pricing fields stay hidden until the source publishes them.

Surface

Input and output modalities, enabled feature flags, strengths, and tradeoffs.

Model capabilities
Attribute	Values
Modalities	textimage to text
Capabilities	reasoningwebSearchimageInputbatchSupportpromptCachingfunctionCallingstructuredOutputs
Strengths	Huge context window, Cheap Grok tier
Tradeoffs	Still evolving quickly

References

Canonical launch, documentation, pricing, and release-note URLs.

Official model links
Reference	URL
Intro	https://docs.x.ai/developers/models
Docs	https://docs.x.ai/developers/models
Pricing	https://docs.x.ai/developers/models
Release note	https://docs.x.ai/docs/release-notes

Coverage

Reported benchmark families, versions, scores, sources, and notes.

Benchmark coverage
Benchmark	Version	Score	Date	Source	Notes

Lifecycle

Lifecycle transitions and release timeline for this model family.

Release history
Release	Alias	Lifecycle	Release Date	Deprecation	Shutdown	Summary
Grok 4 Fast	grok-4-fast	Active	Jan 10, 2026	—	—	Current published model family snapshot.

Surfaces

Provider-specific hosting, context, pricing notes, feature differences, and provider-status context.

Host coverage
Host	Type	Context	Pricing Note	Differences
xAI API	first-party	2.0M	Reference access to Grok 4 families.	Structured outputs; Image input

Migration

Documented migration summary, successor families, and known breaking changes.

Migration guidance
Topic	Details
Summary	Fast-tier alternative to Grok 4.20 beta for budget-sensitive workloads.
Replacement models	grok-4-20-beta

Timeline

Cataloged model-family updates and source references.

Change events
Date	Type	Title	Description	Source
Jan 10, 2026	family_added	Grok 4 Fast published	Initial public model family launch.	Grok 4 Fast release notes

From xAI