Grok 4.5: xAI Releases Cursor-Trained Coding Model at $2/M Input Tokens

xAI released Grok 4.5 yesterday - their first model trained on Cursor's massive developer interaction dataset. At $2/M input tokens (versus $5/M for Opus 4.8 and GPT 5.5), it's the cheapest frontier-tier coding model on the market. The Hacker News thread hit 672 points and 1,077 comments, with debate centering on whether the pricing is sustainable, whether developers will adopt it despite xAI's reputation, and how it stacks against established players.

What Grok 4.5 Brings#

The key differentiator is the training data. After xAI acquired Cursor earlier this year, they gained access to trillions of tokens of developer-AI interaction data - not just code, but the full workflow of how developers prompt, iterate, and refine with AI assistance.

From the Cursor blog:

Grok 4.5 represents Cursor's "most intelligent model and the first we've built for more than software engineering." It handles complex, long-running tasks across software engineering, data science, finance, legal work, and general computer-based problem-solving.

Pricing#

Model	Input	Output
Grok 4.5	$2/M	$6/M
Grok 4.5 Fast	$4/M	$18/M
GPT 5.5	$5/M	$30/M
Claude Opus 4.8	$5/M	$25/M
Claude Fable 5	$10/M	$50/M

Note: Grok 4.5 pricing doubles to $4/$12 for contexts over 200K tokens.

Benchmarks#

xAI claims Grok 4.5 performs at "around Opus 4.7 level" - roughly a generation behind current frontier but at 40% of the price. There's a caveat in the fine print: "Grok 4.5 has an advantage on CursorBench because an earlier snapshot of the Cursor codebase was accidentally included in training."

The model uses a mixture-of-experts architecture with 500K context (200K at base pricing).

What HN Is Saying#

The thread generated intense discussion across several themes.

The xAI Trust Problem#

Many commenters said they won't use Grok regardless of quality:

"Even without the politics, Elon has shown that he will weaponize his platforms against people/companies he personally doesn't like. Using Grok is therefore a supply chain risk and it's not nearly good enough to offset that risk."

Others pushed back on making technical decisions based on politics:

"Americans are 4% of the world's population, and even among those 4% at least half don't give a shit. The rest of us give even less of a shit, we don't have the luxury to be principled."

Pricing Skepticism#

The aggressive pricing raised questions about sustainability:

"Why would having more costs and less income allow them to pass savings on to the end user?"

Some theorized xAI has excess compute capacity from their massive GPU build-out that's sitting partially idle, letting them price aggressively to gain market share. Others noted xAI reported $2.5B in operating losses last quarter.

Cursor Integration#

The Grok Build CLI is now available for SuperGrok subscribers ($300/year), competing directly with Claude Code and Codex. Early users report it's "the fastest I've used in terms of responsiveness" but the model quality lagged until now.

With Grok 4.5 available in Cursor's harness, xAI finally has competitive infrastructure for agentic coding workflows.

The Composer 2.5 Comparison#

Several commenters noted that Cursor's existing Composer 2.5 model - which is much cheaper to run - handles most coding tasks well:

"Composer 2.5 is so underrated IMO. I built a really feature rich application, insanely complicated, close to 200k LOC since it came out and for the most part it ran like a champ."

The question is whether Grok 4.5's broader training makes it worth the cost premium over task-specific models.

Why This Matters#

Three things to watch:

1. Cursor data is a competitive moat. Training on real developer workflows - not just code, but the iterative prompting patterns of millions of users - produces models that understand how developers actually work. This is data that OpenAI and Anthropic don't have at this scale.

2. The price war continues. At $2/M input, Grok 4.5 undercuts every comparable model. If xAI can sustain this pricing (a big if given their burn rate), it puts pressure on Anthropic and OpenAI to respond.

3. Model routing gets more interesting. Many teams already route between models based on task complexity. A cheap, fast model for simple completions; an expensive reasoning model for complex tasks. Grok 4.5 slots into this matrix as "frontier-ish at Sonnet prices."

The Bigger Picture#

xAI's strategy is becoming clearer: use Cursor's distribution to capture developer workflows, train models on that data, and price aggressively to gain share. The Colossus 2 datacenter is training 5T and 10T parameter models that could extend this lead.

For developers evaluating Grok 4.5:

Try it for cost-sensitive agentic workflows where you'd otherwise use Sonnet
Don't expect Opus/Fable-tier reasoning - benchmark claims put it closer to Opus 4.7
Factor in the context pricing jump at 200K tokens
Consider the platform risk if you're concerned about xAI's corporate direction

The model is available now via xAI's API and through Cursor's desktop, web, and CLI interfaces.

Continue Reading#

Sources#

FAQ#

How much does Grok 4.5 cost?#

$2 per million input tokens, $6 per million output tokens for contexts under 200K. Pricing doubles for larger contexts.

How does Grok 4.5 compare to Claude Opus 4.8?#

xAI claims Grok 4.5 performs at "Opus 4.7 level" - roughly one generation behind Opus 4.8 - but at 40% of the cost.

Can I use Grok 4.5 in Cursor?#

Yes. Grok 4.5 is available in Cursor's desktop, web, iOS, and CLI interfaces for subscribers.

What makes Grok 4.5 different from other models?#

Training data. Grok 4.5 was trained on trillions of tokens from Cursor's user interaction dataset, capturing real developer-AI workflows rather than just static code.