What changed
xAI shipped Grok 4.5 on Wednesday 2026-07-08, its first model built specifically for coding and agentic tasks 1. It exposes an OpenAI-compatible API surface under the reference grok-4.5, documented at docs.x.ai/developers/grok-4-5 3, priced at $2 per million input tokens and $6 per million output tokens 1 and running at roughly 80 tokens per second 3. It is live now through Grok Build, Cursor on every plan, the SpaceXAI console, and OpenRouter 12. Musk called it “an Opus-class model, but faster, more token-efficient and lower cost” 1. That is his framing. The measured results are the interesting part.
The benchmark split
Every benchmark xAI published is self-reported, and there are exactly four. Against Opus 4.8 they land 2-2, and Claude Fable 5 leads all four 2.
| Benchmark (xAI self-reported 2) | Grok 4.5 | Opus 4.8 |
|---|---|---|
| DeepSWE 1.0 | 62.0 | 55.75 |
| DeepSWE 1.1 | 53 | 59 |
| Terminal-Bench 2.1 | 83.3 | 78.9 |
| SWE-Bench Pro | 64.7 | 69.2 |
Grok 4.5 wins DeepSWE 1.0 and Terminal-Bench 2.1, loses DeepSWE 1.1 and SWE-Bench Pro 2. It ranks 4th on the Artificial Analysis Intelligence Index, above every open-weight and Gemini model 3. “Opus-class” survives as a fair label for the tier; it does not survive as “beats Opus”.
The data flywheel
What will still matter in a year is the training data, more than any benchmark line. xAI says it folded real Cursor developer session data, debugging traces, multi-file diffs, and user corrections, into supplemental training 2. That is developer-session exhaust from a live agentic-coding product, tuned on the actual shape of the work rather than a generic code corpus. It is xAI’s own phrasing, not something I can independently verify, but if it holds it is the advantage a competitor cannot cheaply copy: you need a product like Cursor feeding you before you can train on it.
Impact on your team
If you are a non-EU team already in Cursor, grok-4.5 is worth a trial as a cheaper agentic default at $2/$6 per million tokens 1, but treat it as a price-performance play: re-baseline it on your own agent eval suite, because the four numbers that sell it are self-reported and split 2-2 2. If you are in the EU, there is nothing to do yet but wait for the mid-July window 1. The one thing to ignore is the “Opus-class” adjective taken as a verdict; the split, and your own traces, are the numbers that matter.