xAI Open-Sources Grok Build: A Review
Simon Willison · rss · 2026-07-16
xAI has open-sourced the Grok Build repository. The author took the opportunity to review the implementation details of this coding agent and the previously controversial data upload issue.
Key takeaways include:
- It was previously discovered that running grok-build could upload an entire directory to xAI's Google Cloud bucket. Some users even reported that their SSH keys, password manager databases, documents, and photos were siphoned off.
- Following massive community backlash, xAI first disabled the upload feature and later open-sourced the entire Grok Build codebase under the Apache 2.0 license.
- The codebase is massive; SLOCCount estimates roughly 844,530 lines of Rust, with only about 3% appearing to be vendored code.
- Implementation details highlighted include: separated system and sub-agent prompts, a Mermaid terminal renderer, and a suite of tools mimicking Codex / OpenCode.
- Remnants of the GCS upload logic are still visible in the code, though the feature itself has been disabled.
Overall, this serves as a comprehensive case study combining a coding agent product, a privacy controversy, and an open-source review.
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