SpaceX and Cursor Launch Their First Jointly Built AI Model: Grok 4.5

The option was exercised on June 16, 2026. SpaceX announced via an official post on X that it had "exercised the option to acquire @cursor_ai in an all-stock transaction with the goal of building the world's most useful AI models."^BT This all-stock deal valued the four-year-old startup at $60 billion, making it the largest acquisition of a venture-backed company in history.^PT The acquisition was announced just days after SpaceX’s historic debut on the Nasdaq, and the deal is expected to close in the third quarter of 2026, pending regulatory approvals.^TCW

The Jointly Built Model: Grok 4.5's Technical Basis

On June 28, 2026, Elon Musk confirmed the specifics of the jointly trained model. Grok 4.5 is based on xAI's 1.5-trillion-parameter V9 foundation model, with Cursor's developer data added through supplemental training.^BM The model is currently in private beta at SpaceX and Tesla, with early internal evaluations showing performance "close to, perhaps exceeding Opus."^M

The infrastructure behind the model is equally significant. SpaceX has been using its Colossus supercomputer cluster as the compute backbone for the joint training effort.^A Cursor’s contribution includes its proprietary coding model Composer and the rich dataset of developer interactions from its AI-powered code editor.^BA

SpaceX’s official statement on June 16 made the deployment plan clear: "For the past few months, SpaceXAI has been jointly training a model with Cursor, which will be released in Cursor and Grok Build soon."^B This confirms the model will ship in both products, rather than being exclusive to one. Grok Build is xAI’s terminal-based coding agent, which launched between May 14 and May 25, 2026, making it the fourth AI lab to offer a dedicated CLI coding agent after Claude Code, Codex, and Google's Gemini/Antigravity.^T

Competitive Positioning in the AI Coding Market

The deal and the resulting model place SpaceX/xAI directly in the AI development-tools and coding-agent market. The April Reuters report described this as a profitable sector SpaceX was aiming to expand into.^D

Cursor brings an established AI-powered code editor with a large developer user base, a developer workflow platform, and its proprietary Composer coding model.^TA The strongest documented strategic advantages in the provided sources are access to SpaceX’s Colossus compute infrastructure and the use of Cursor data in supplemental training for Grok 4.5.^BA

Furthermore, even before the formal acquisition, xAI added Cursor’s Composer 2.5 model to Grok Build on June 1, 2026. This model scores 79.8% on SWE-bench Multilingual, compared to Grok Build's native model which scored ~70.8% on SWE-bench Verified.^T This move immediately improved xAI's competitive standing in AI-powered coding benchmarks.

Key Uncertainty: The Public Launch Date

While the model is real and in use, the exact public launch date remains uncertain. SpaceX said "soon" on June 16.^B Grok 4.5 itself is described as a private beta model at SpaceX and Tesla, not a generally available public product for paying developers, who still use Grok 4.3 on v8-small.^BM No provided source confirms a specific Wednesday launch date for a consumer-available jointly trained model.

Summary of Key Facts