xAI and Cursor launch Grok 4.5, an Opus-class coding model

xAI is not trying to win the benchmark crown - it is trying to make the crown irrelevant. Grok 4.5 lists at $2 per million input tokens and $6 per million output tokens, roughly half of Anthropic's Opus 4.8 at $5/$25 and well under GPT-5.5 at $5/$30 ^[1]. The more aggressive claim is efficiency: xAI says Grok 4.5 spends 4.2x fewer tokens than Opus 4.8 to finish the same SWE Bench Pro tasks, averaging 15,954 output tokens versus 67,020 ^[1]. Because you pay per token, fewer tokens per task compounds with the lower per-token price.

The combined effect is a cost-per-task that independent trackers put far below rivals. On Snorkel AI's run across roughly 2,000 professional-work tasks, Grok 4.5 led on mean pass rate - 29% versus 22% for GPT 5.5 and 21% for Opus 4.8 ^[2]. Pair a top-tier result with the lowest price in the tier and the strategy becomes legible: get close enough on quality, then win decisively on the invoice ^[1].

The 'beats Opus' framing does not survive contact with the full benchmark sheet. Grok 4.5 leads on some tests - DeepSWE 1.0 at 62.0% versus Opus 4.8's 55.75%, and Snorkel's GDPval+ - but trails on others, including DeepSWE 1.1 (53% versus Opus's 59% and GPT-5.5's 67%) and SWE Bench Pro (64.7% versus Opus's 69.2%) ^[1]. Even the model that led Snorkel's test passed fewer than one in three criteria, a reminder that expert-level work is still unsolved ^[2].

There is also a credibility flag baked into the launch. Cursor disclosed that an earlier snapshot of its own codebase was accidentally included in Grok 4.5's training data, which would inflate any Cursor-specific benchmark; it says the data has been removed for future models ^[4]. Elon Musk's own framing is more measured than the marketing - he called Grok 4.5 roughly comparable to Opus 4.7, but much faster, not a benchmark champion ^[3]. The honest read is a model that is competitive rather than dominant, and cheap enough that the distinction may not matter to most buyers ^[1].

Grok 4.5's real advantage may be data, not compute. It is a mixture-of-experts model trained jointly with Cursor on trillions of tokens of developer-agent interaction data - the multi-file edits, debugging traces, and tool calls that happen inside a working coding assistant ^[4]. That corpus is something web-scraped text cannot replicate, and it explains the coding-and-agentic focus of the release.

It also explains the price tag. SpaceX agreed in June 2026 to acquire Cursor for roughly $60 billion in stock, days after the startup's IPO, with the deal expected to close in the third quarter ^[5]. The move folded a leading coding-assistant distribution channel and its proprietary interaction data into xAI's pipeline in one stroke. Training then ran across tens of thousands of NVIDIA GB300 GPUs with heavy investment in data filtering and deduplication ^[6]. The compute is table stakes; the Cursor data is the moat.

The launch-day reaction from practitioners split along a predictable line: enthusiasm about the economics, skepticism about the sourcing. On developer-heavy forums the price-to-performance ratio, not the raw capability, was the headline, with hands-on coders reporting that Grok 4.5 felt right up there with Opus and GPT-5.5 for real work while costing a fraction as much. Developer YouTube skewed toward live coding tests rather than spec recaps, with reviewers running the model in Cursor and Grok Build and treating vendor benchmarks warily after the contamination disclosure.

The dominant contrarian threads were about sustainability and timing. Many assumed the pricing is subsidized to buy market share and questioned how long such aggressive rates can hold. Others noted the model arrived barely a day ahead of an expected GPT-5.6 release and joked that it might stay competitive 'for one day,' reading the launch as timed for attention as much as readiness. And a persistent practical gripe cut through the hype: EU users were locked out at launch, with access promised for mid-July ^[6]. The through-line is that price pressure, not benchmark bragging rights, is what rivals now have to answer ^[1].