The Codex desktop app keeps 1.7GB of tools on disk, LibreOffice included

On September 1, 2026, Simon Willison reported that the OpenAI Codex desktop app, since rebranded to ChatGPT, keeps 1.7GB of files in a cache folder named codex-primary-runtime. He found it while looking through his cache with a disk usage tool, which is to say it was never announced. What it holds explains more than its size does.

What is in the folder

The runtime is not a model or a set of weights. It is an ordinary local toolchain, of the sort you would install by hand to process documents on your own machine.

• A full Python installation and a full Node.js installation.
• Native binaries for Poppler, which reads and converts PDF files, and for git.
• The LibreOffice office suite, which opens and converts word processor, spreadsheet and presentation formats.

Why it is there

A folder inside the same runtime, under the documents plugin, contains skills that tell Codex how to find and use those binaries. That is the part that turns a disk observation into a capability one. An agent that ships LibreOffice and Poppler alongside instructions for calling them is being set up to open, convert and write office documents and PDFs locally. It does not need to upload them somewhere and wait for a service to answer.

This suggests two practical consequences. Document conversion in the app does not require the file to leave the machine, which matters for anyone whose documents are not supposed to travel. And the cost is 1.7GB of disk per installation, sitting in a cache folder where nobody thinks to look. Neither is a problem, but both are the kind of thing worth knowing before an agent is rolled out across a fleet of laptops.