Grok Build is xAI's terminal-based coding agent, separate from the Grok chatbot. As of August 2026 it offers two selectable coding engines: xAI's own Grok 4.5, launched July 8, 2026, and Cursor's Composer 2.5, added after SpaceX agreed to acquire Cursor's parent company for $60 billion.
Summary: If you're picking Grok Build for coding, know that xAI's pending $60 billion purchase of Cursor means you're actually choosing between two separate engines under one name: xAI's own Grok 4.5, or Cursor's Composer 2.5. Neither company has published a head-to-head benchmark between them.
SpaceX agreed to pay $60 billion in stock for the AI coding startup Cursor in June 2026, and by August xAI's own terminal coding tool, Grok Build, was running on the very model it had just bought.
The deal, reported by Forbes and TechCrunch on June 16, 2026, folds Cursor's parent company into xAI, the AI division SpaceX built around Elon Musk's Grok brand. Three weeks earlier, Cursor had marketed its Composer 2.5 model as exclusive to its own products. By early June it was selectable inside Grok Build for paying subscribers, sitting next to xAI's own coding model. For a developer trying to work out what "Grok" actually buys before paying for it, the answer just got more complicated. Not less.
The timeline matters more than the headline. In April 2026, the two companies signed a conditional deal: pay $10 billion for ongoing collaboration, or acquire the smaller firm outright for $60 billion. Cursor was, at the same time, raising a separate $2 billion round at a $50 billion valuation of its own. The buyer exercised the buyout option on June 16, 2026, an all-stock transaction both outlets reported at $60 billion, on a schedule that points to a close before October.
Cursor's own changelog dates Composer 2.5 to May 18, 2026. It is a mixture-of-experts model built on Moonshot AI's open Kimi K2.5 checkpoint, with 85% of its compute spent on additional reinforcement-learning training, and trained on 25 times more synthetic tasks than its predecessor. Published numbers put it at 79.8% on SWE-Bench Multilingual and 69.3% on Terminal-Bench 2.0, priced from $0.50 per million input tokens. At launch, the company described it as exclusive to its own IDE, CLI and web product.
That did not hold for long. A bug report filed against an unrelated open-source coding tool on June 9, 2026 shows a paying subscriber confirming the model had shipped inside Grok Build, weeks before the acquisition was even announced. It now sits next to Grok 4.5, the coding-focused model xAI trained itself, which would not publicly launch for another month, on July 8. Two engines, one product, roughly six weeks apart.
Subscribers get a benchmark-leading coding model bundled into a plan they already pay for, without a separate bill from a second company. xAI gets to point at someone else's coding results as if they were its own, without training the model itself or publishing a comparable number through its own developer API.
The acquired company's investors and staff land an outcome ten billion dollars richer than the valuation of the funding round they were independently pursuing weeks earlier. That is not a small gap for a firm founded in 2022.
There is a real product case for offering both engines, too. A developer working across a large repository can pick whichever one handles that specific job better, the same way Cursor's Composer 2.5 already lets users choose between several base models inside one editor, long before any of this consolidation started.
Nobody in this deal loses money. The people who lose something are developers who picked Grok because it was supposed to be one thing. It no longer is.
Grok Build now ships two internally competing coding engines with no published benchmark comparing them on the same suite, under the same conditions, on the same day. You are left choosing between the cheaper in-house option and the one with better published scores, on faith, until someone runs the comparison themselves.
It also complicates the pitch against Claude Code and other single-model coding tools. That competing pitch has always been simple: one lab, one model, one roadmap. This one now runs two roadmaps under a single name, bought weeks apart, priced differently, and benchmarked on different test suites by two separate teams.
The obvious rebuttal: offering a choice of models inside one coding tool is standard practice, not a confession. Several rival editors already do it. Nobody accuses a router of not knowing what it is for.
That comparison does not quite hold here. Those tools never claimed to be a foundation-model company. A menu of third-party options is exactly what an orchestration layer is supposed to offer.
The brand at the center of this story has spent years building a public identity around being a frontier model itself, not a router in front of one. A model company's own flagship developer tool quietly stepping away from its own model by default is a different kind of signal than a router adding an option nobody expected it to have.
The acquisition is due to close by the end of the third quarter, according to both outlets that broke the story. Watch what happens to the acquired model's name after that date, not before.
If it gets retired and folded into future releases under the parent brand, this was an integration step, and the two-engine period was temporary. If it keeps shipping under its own name into 2027, alongside a next flagship release several outlets already expect in beta by then, the split is a deliberate strategy for the brand: one name, two stacks, sold as flexibility rather than confusion.
Nobody outside the two companies involved has published a benchmark table with both models side by side. Until one exists, the honest answer to "which should I use" is to test both against your own repository, because neither team that built them has told you which one wins.
Grok Build is xAI's terminal-native coding agent, a separate product from the consumer Grok chatbot and from Grok's general chat models. It is built for writing and editing code inside a real repository rather than open-ended conversation. As of mid-2026 it offers more than one underlying model rather than a single fixed engine.
SpaceX, which built its AI division around xAI, agreed on June 16, 2026 to acquire Cursor's parent company Anysphere for $60 billion, following a conditional April 2026 agreement. Composer 2.5 began appearing inside Grok Build for SuperGrok subscribers in early June 2026, weeks before the acquisition was formally announced. xAI has not stated on the record whether it is the default engine or an optional one.
SpaceX agreed to an all-stock deal valued at $60 billion for Anysphere, Cursor's parent company, announced June 16, 2026, according to Forbes and TechCrunch. The transaction is expected to close in the third quarter of 2026. Cursor had separately been raising a $2 billion round at a $50 billion valuation around the same time.
Cursor reports Composer 2.5 scoring 79.8% on SWE-Bench Multilingual and 69.3% on Terminal-Bench 2.0. xAI has not published Grok 4.5 on the same benchmarks, and no independent test compares the two models under identical conditions. Until that exists, the honest answer is to test both against your own codebase rather than trust either company's number alone.
Cursor's own pricing lists Composer 2.5 from $0.50 per million input tokens through Cursor directly. Access through Grok Build instead runs on a SuperGrok or X Premium+ subscription rather than a separate Cursor account, based on the June 2026 rollout. xAI has not published a standalone per-token price for Composer 2.5 inside Grok Build itself.
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