Introducing Grok 4.5

Summary

Cursor and SpaceXAI are releasing Grok 4.5, a mixture-of-experts model designed for long-running computer tasks beyond software engineering, including data science, finance, and legal work. It was trained jointly on trillions of tokens of Cursor data, alongside high-quality STEM tasks, research papers, and other knowledge work, then improved with reinforcement learning in realistic environments where it must investigate, use tools, recover from mistakes, and verify results. A distributed agent system built and refined these training environments at scale, using engineers’ problem definitions and verification methods. Grok 4.5 is available in Cursor’s desktop, web, iOS, CLI, and SDK products, with individual and team plans receiving significant usage and double usage during the first week; base pricing is $2 per million input tokens and $6 per million output tokens. Cursor notes that an accidental training-data inclusion gives the model an advantage on CursorBench.

Takeaways

1. 1

   New safeguards were added to reflect Grok 4.5’s cybersecurity capabilities.

2. 2

   Grok 4.5 and Composer 2.5 are different model weight classes; Composer 2.5 remains available, and new models of its size are planned.

3. 3

   An earlier Cursor codebase snapshot was accidentally included in training, giving Grok 4.5 an advantage on CursorBench. The exact impact is unclear, and the data has been removed for future models.