Grok 4.3, the xAI model in numbers

What you need to know

Grok 4.3 is a language model from xAI, released on April 17, 2026. That makes it 6 months old as of October 22, 2026. Its weights are not published, so it only runs remotely, through the xAI API or partner hosts (30 listed on models.dev). It has a reasoning mode: it can "think" before answering, which helps with multi-step problems but uses more tokens, and therefore more money.

We file it under mid-range models (34 models in this category on the site).

Benchmark results

According to results published by Epoch AI (checked on October 22, 2026), Grok 4.3 has a capability index of 76.8 out of 100, computed on 3 benchmarks from our basket.

With only 3 benchmarks reported, it does not enter the public ranking, which requires at least 4 results, so its index should be read as partial.

• GPQA Diamond (PhD-level science questions): 88.8% — the best tracked model, Gemini 4 Argon, reaches 96.4%
• OTIS Mock AIME (competition mathematics problems): 93.3% — the best tracked model, GPT-5.5 Pro, reaches 100%
• FrontierMath (very hard research-level mathematics): 42.8% — the best tracked model, GPT-6 Astra, reaches 93.7%

What it can do

Its context window reaches 1,000,000 tokens, roughly 1,500 pages of text at 500 words per page: enough to load a whole book or a mid-sized codebase. A single answer can run to 30,000 tokens.

It accepts as input: text, image and PDF.

It can call tools (functions, APIs) and return structured JSON output, which makes it a possible foundation for an AI agent.

What it costs

Grok 4.3 costs $1.25 per million input tokens and $2.5 per million output tokens (median of 30 providers, checked on October 22, 2026).

In practice, an agent task that reads 20,000 tokens and writes 2,000 costs about $0.03, or $30 for 1,000 such tasks.

That is 1.8 times cheaper than the median output price of mid-range models ($4.38).

To estimate your own budget, use the agent cost calculator.

When to choose it

Given its category, Grok 4.3 is mainly aimed at a balance between quality and cost, for everyday uses that do not justify a frontier model.

Its very large context window makes it worth considering for analysing large sets of documents in a single request.

Before adopting it, test it on your own examples: benchmarks measure standard tasks, not your job.

Comparable models

In the same category, the models closest to Grok 4.3 are:

• Claude Opus 4.6 (Anthropic, index 76.7)
• Gemini 3.5 Flash (Google DeepMind, index 76)
• GPT-5.1 (OpenAI, index 75.8)
• GPT-5 (OpenAI, index 75.3)