xAI · 2026-04-30 · major
Grok 4.3 — xAI's New Reasoning Flagship at $1.25/$2.50 per 1M Tokens, 1M-Token Context
xAI ships Grok 4.3 as its new most-capable model: 1M-token context, always-on reasoning, text+image input, and 37.5% cheaper input / 58.3% cheaper output than Grok 4.20. Artificial Analysis Intelligence Index puts it at 53, well above the reasoning-model median of 34.
xAI's new flagship reasoning model lands with a 1M-token window, image input, and lower per-token pricing than Grok 4.20.
Key specs
| Context window | 1M tokens |
|---|---|
| Price (input) | $1.25 / 1M tokens |
| Price (output) | $2.50 / 1M tokens |
| Aai intelligence index | 53 |
| Output speed | 199.1 tok/s |
What is it?
Grok 4.3 is xAI's latest reasoning model, billed by the company as its most intelligent and fastest. It accepts text and image inputs, returns text, and runs reasoning continuously — there is no toggle to disable or dial it down. The model rolled into the xAI API and Grok's apps on April 30, with developer documentation and pricing pages live on docs.x.ai.
How does it work?
The model serves a 1,000,000-token context window with no fixed output limit, with tiered pricing kicking in beyond 200k tokens per request. Reasoning is always active, and the agentic-loop optimizations give it a 321-point ELO jump on GDPval-AA versus the prior generation. Input is priced at $1.25 / 1M tokens and output at $2.50 / 1M, a 37.5% / 58.3% cut from Grok 4.20.
Why does it matter?
It is the largest closed-model context window among Western providers paired with frontier-adjacent intelligence at mid-tier prices. For agent workflows that burn tokens on long traces, the price drop is meaningful. For analysts comparing labs, the AAI score of 53 puts xAI between the cheap-and-fast tier and the GPT-5.5 / Opus 4.7 frontier.
Who is it for?
Agent builders, long-context users, anyone running heavy reasoning workloads on a budget.
Try it
curl https://api.x.ai/v1/chat/completions -H 'Authorization: Bearer $XAI_KEY' -d '{"model":"grok-4.3","messages":[{"role":"user","content":"hi"}]}'