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Term

Grok 4

Grok 4 is xAI's reasoning model from July 2025 — text and image input, 256k context, trained via reinforcement learning on the 200,000-GPU Colossus cluster.

Grok 4 — explained in more detail

Grok 4 launched in July 2025 from xAI and is the company’s first reasoning model to lean on its in-house Colossus training cluster with 200,000 GPUs for reinforcement learning. It accepts text and images as input, returns text and operates with a 256,000-token context window. The Grok 4 Heavy variant was the first model to score 50% on Humanity’s Last Exam, a top-tier academic benchmark.

Where it fits

On the Artificial Analysis Intelligence Index, Grok 4 scores 42 — above average for its price tier (median 34). API pricing at launch: $3.00 per 1M input tokens, $15.00 per 1M output tokens. In April 2026, Grok 4.3 replaced the model as the default offering — with a 1M context, native video input and input prices roughly 40% lower.

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