Grok 4.5: xAI's Real-Time Mixture-of-Experts Model

What is Grok 4.5?

Grok 4.5 is a model from xAI with a 500,000 token context window. xAI's published documentation covers its context limit and pricing but does not state a parameter count, an architecture, or a release date, so this guide does not assert any of them. Pricing is tiered by prompt length: $2 input and $6 output per million tokens below 200k tokens, doubling to $4 and $12 at or above that threshold. (AIblogly analysis: that doubling matters more than it first looks - a long-context workload crosses into the higher tier for the whole request, not just the tokens past 200k.)

What xAI Does Not Publish

Earlier versions of this guide described Grok 4.5 as built on "a 1.5-trillion-parameter mixture-of-experts architecture" with "native real-time access to the web and X" and consumer access "through X Premium+ subscriptions". None of that is stated in xAI's model or pricing documentation, so all three claims have been removed rather than repeated. xAI's documentation covers context window and API pricing only.

Capabilities and Context

Grok 4.5 has a 500,000 token context window - large enough for substantial codebases and long documents, though a quarter of Claude Opus 5's or GPT-5.6's 1M-class windows. Beyond context length and pricing, xAI's public documentation does not detail specific capabilities such as tool use, vision, or agentic features for this model, so this guide does not assert them.

Ideal Use Cases

Based on what xAI actually publishes - a 500k context window at $2/$6 (or $4/$12 above 200k tokens) per million tokens - Grok 4.5 is a reasonable fit for cost-sensitive workloads that do not need the largest context windows on this list. (AIblogly analysis: without vendor-confirmed capability claims beyond pricing and context, we cannot responsibly recommend it over competitors for any specific task the way the other guides in this series can.)

Limitations

The clearest limitation is what is not published: no parameter count, no stated architecture, no capability list beyond context window and price. It ranks 35th on LMArena at 1470, in the middle of the models covered on this site. As a closed model, self-hosting and weight inspection are not available. Standard verification practices for factual and safety-critical outputs apply, as with any language model.

Grok 4.5 vs Competitors

On price, Grok 4.5 undercuts Claude Opus 5 and GPT-5.6 Sol: $2/$6 per million tokens under 200k, against $5/$25 and $5/$30 respectively. On LMArena it ranks 35th at 1470 - below Gemini 3.1 Pro (14th), Claude Opus 5 (7th) and GPT-5.6 Sol (16th), but above DeepSeek V4-Pro (52nd) and Mistral Large 3 (125th). (AIblogly analysis: it sits in the middle of this list on both price and ranking - cheaper than the top three, pricier and higher-ranked than the two open-weight options.)

Official Resources