The New Grok 4.5 Is Out. Elon Musk Says It Competes With Last Year’s Claude Opus

Elon Musk’s SpaceXAI released Grok 4.5 on Wednesday, its first public model since the SpaceX-xAI merger closed in February and SpaceX’s pending $60 billion deal to acquire Cursor. It targets coders, engineers, and what the company calls “knowledge workers”—a category that apparently covers everyone from software developers to lawyers reviewing contracts to finance teams building Excel models.

The company’s pitch isn’t that it’s the best model. It’s that it’s cheap, for a western model at least. Grok 4.5 costs $2 per million input tokens and $6 per million output. Claude Opus 4.8, Anthropic’s primary flagship, runs $5 input and $25 output. GPT 5.6 Sol, OpenAI’s new top-tier model that also launched Wednesday, is priced at $5 input and $30 output.

Musk posted on X and clarified where his new model actually sits. He called it “roughly comparable to Opus 4.7, but much faster.” Opus 4.7 is Anthropic’s previous flagship; Opus 4.8 has since succeeded it. Claude Fable 5 is now Anthropic’s top of the line offering.

He framed that as a deliberate tradeoff: speed and cost over raw capability, with engineers at Tesla and SpaceX as the proof of real-world utility.

What the benchmarks actually show

SpaceXAI published four benchmark results at launch, and the picture is mixed. DeepSWE 1.1 measures how reliably an AI can close real software bugs submitted by developers, using a standardized testing setup so models can be compared fairly, scored by percentage of issues fixed. Grok 4.5 scored 53%, behind Claude Opus 4.8 at 59% and GPT 5.5 at 67%. Claude Fable 5, Anthropic’s frontier model, topped the chart at 70%.

On SWE Bench Pro, another benchmark that measures a collection of software engineering problems scored by resolution rate, Grok 4.5 posted 64.7%, enough to beat GPT 5.5’s 58.6% on that particular test. Opus 4.8 still leads at 69.2%, and Fable 5 sits at 80.4%.

The company’s benchmarks compare against GPT 5.5, not GPT 5.6, because the latter also launched Wednesday, hours after Grok 4.5’s announcement.

SpaceXAI trained Grok 4.5 in collaboration with the recently acquired Cursor AI on tens of thousands of Nvidia GB300 GPUs inside Colossus, the Memphis supercomputer with total capacity across more than 200,000 GPUs. The labs whose models sit above it on those same benchmarks don’t own anything close to that hardware. The model that came out is competitive, just not first.

That pattern has followed Grok across multiple releases. SpaceXAI has consistently turned up with enormous compute and third-place scores. What changed with Grok 4.5 is the pricing and the training signal.

Where the case for it actually holds

The better argument isn’t raw performance; it’s efficiency math. On SWE Bench Pro tasks, Grok 4.5 used an average of 15,954 output tokens to complete each job. Opus 4.8 burned through 67,020 tokens for the same work, a 4.2x gap.

For teams running AI at volume, that difference compounds into real savings on top of the already-lower price per token. Even with Grok 4.5 scoring so low in the quality benchmarks, cheaper tokens and more efficiency in usage allow for more iterations without spending so much.

The model also runs at 80 tokens per second, which is fast-model territory. Grok 4.5 was trained on developer session data from Cursor, including debugging traces and real code edits rather than static repositories. As Musk admitted in court, xAI’s training practices have drawn scrutiny before; this time the pipeline runs through a platform SpaceX is in the process of buying outright.

For developers running high-volume coding tasks, the math works: roughly Opus 4.7 capability at 60% less per input token. For anyone chasing the frontier, Claude Fable 5 leads every category SpaceXAI chose to publish. Our quick test using Grok build on Hermes was underwhelming for creative writing and acceptable on a simple coding task.

The model is available via API, on Hermes and Grok build with half a million tokens of context (a little bit less than 400,000 words). European users will have to wait before using it; SpaceXAI says Grok 4.5 reaches the EU in mid-July.