Claude Code Is Steganographically Marking Requests

Claude Code contains steganographic markers embedded in the system prompt's date string that encode information about the user's location, API configuration, and whether they're using known AI labs or Chinese corporate domains. The marker uses subtle character substitutions—different Unicode apostrophe variants and date format changes (dashes to slashes)—that are visually imperceptible but detectable by the model, allowing Anthropic to track whether requests are coming from specific regions or organizations without user knowledge.