xAI launches Grok 4 Fast, a multimodal model with a 2M context window and a unified architecture that combines reasoning and non-reasoning modes
Pushing the Frontier of Cost-Efficient Intelligence — We're thrilled to present Grok 4 Fast, our latest advancement in cost-efficient reasoning models.
xAI
Context & Ripple Effects
Grok 4 Fast extends xAI’s Grok 4 line after the company introduced a multimodal Grok 4 with faster reasoning and code capabilities in July 2025. It shifts the emphasis from adding model variants to making reasoning usable at lower cost across a much larger working context.
xAI gains a Grok offering that can process up to 2M tokens and handle multimodal inputs while combining reasoning and non-reasoning modes in one architecture.
Developers and enterprises evaluating Grok can target long-document or long-running workflows without selecting separate reasoning and standard model families for those tasks.
Second-order effects
Competing model providers face added pressure to pair long-context support with credible cost-efficient reasoning, rather than treating context-window size as a standalone specification.
Application builders may simplify model-routing logic where a unified model adequately serves both fast-response and deliberative tasks, although actual savings depend on the model’s pricing and performance in deployment.
Third-order effects
If unified architectures continue to improve, the market may increasingly compete on the economics of allocating reasoning and context per task—not simply on benchmark performance.
Large context windows could make persistent, document-heavy AI workflows more practical, raising the strategic value of Grok 4’s earlier multimodal and code capabilities alongside lower-cost inference.
The trend: Frontier-model vendors are turning context capacity and adaptive reasoning into cost-management features for production AI workloads.
xAI just released Grok-4 Fast (also known as mini), a strong model with a 2 million token context window, improved reasoning token efficiency and frontier search performance with very competitive pricing https://x.ai/... Pricing: $0.2 Input, $0.5 Output for both [image]
Grok 4 Fast is available now for all users in https://grok.com/, https://grok.x.com/, iOS and Android apps in Fast and Auto modes. All users, including free users, will have access to our latest model without restrictions, marking a significant step toward
Introducing Grok 4 Fast, a multimodal reasoning model with a 2M context window that sets a new standard for cost-efficient intelligence. Available for free on https://grok.com/, https://grok.x.com/, iOS and Android apps, and OpenRouter. https://x.ai/...
For a limited time, Grok 4 Fast will be available for FREE on OpenRouter and Vercel AI Gateway. Grok 4 Fast is also generally available via the xAI API, with pricing starting at $0.20 / 1M input tokens and $0.50 / 1M output tokens. https://console.x.ai/
Grok-4-fast shows strength in key categories: 🔸 Ranks #2 in Multi-Turn 🔸 Tied for #3 in Coding 🔸 Tied for #3 in Longer Query The competition just keeps heating up 🔥 Check out the full leaderboard details here: https://lmarena.ai/... [image]
🚨 Leaderboard Disrupted! Grok-4-fast by @xAI has arrived in the Arena, and it's shaking things up! ⚡️ 🏆 #1 on the Search Leaderboard Tested under the codename “menlo,” Grok-4-fast-search just rocketed to the top spot with the community. 💠 Tied for #8 on the Text Leaderboard [imag…
xAI has released Grok 4 Fast - breaking through our intelligence vs cost frontier by achieving Gemini 2.5 Pro level intelligence at a ~25X cheaper cost Intelligence: @xai shared with us pre-release access to Grok 4 Fast. In reasoning mode, the model scores an impressive 60 on [im…