I was inspecting Claude Code for privacy reasons. Most devs give their harnesses ridiculous access. FS, shell, git, browser access, even computer use nowadays. That is the whole point. They need enough context to do useful work. That also means the client itself deserves scrutiny. If a coding agent can read your repo and run commands, the binary that ships it should be boring (ƒor example, pi harness) So I took a look at my local Claude Code (2.1.196) install. Inside the Claude Code binary, there is a function that changes the current date string inserted into the system prompt. The normal string looks like this: Claude Code can silently change two things: The apostrophe in Today's The date separator, from - to / Here is the relevant code, cleaned up from the minified bundle: This is prompt steganography, a technique used to hide data in plain sight. The visible sentence still reads like a normal date. The model and the user see something boring. The raw request contains a marker.…