I was poking around in my ~/.cache/ folder using OmniDiskSweeper：https://www.omnigroup.com/more when I spotted something interesting. The OpenAI Codex desktop app (since rebranded：https://help.openai.com/en/articles/20001276-moving-to-the-new-chatgpt-desktop-app to just ChatGPT) has 1.7GB of stuff in there in a folder called codex-primary-runtime , including a full Python installation, a full Node.js installation, and native binaries for Poppler：https://poppler.freedesktop.org, git, and the LibreOffice：https://en.wikipedia.org/wiki/LibreOffice open source office suite (which forked from OpenOffice.org in 2010):

Screenshot of a macOS disk usage app window in column view, titled "/Users/simon/.cache - 442.1 GB". First column: 356.8 GB huggingface, 82.5 GB uv, 1.7 GB codex-runtimes (selected), 609.0 MB datasette-sqlite, 298.8 MB rod. Second column: 1.7 GB codex-primary-runtime (selected). Third column: 1.7 GB dependencies (selected), 6.3 MB plugins, 4.1 kB runtime.json. Fourth column: 771.0 MB native (selected), 446.4 MB node, 440.6 MB python, 28.7 kB bin. Fifth column: 429.7 MB libreoffice-headless (selected), 187.9 MB poppler, 148.1 MB git, 4.7 MB libheif, 679.9 kB jxrlib.

The ~/.cache/codex-runtimes/codex-primary-runtime/plugins/openai-primary-runtime/plugins/documents folder includes skills which tell Codex how to find and use those binaries.

This is a note by Simon Willison, posted on 1st September 2026：/2026/Sep/1/.

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