Stealth Attribution: When the Assistant Marks Your Requests Without Telling You
This morning, Hacker News lit up with a story that should make every developer pause: Claude Code is steganographically marking requests. Not through metadata. Not through headers. Through invisible Unicode characters embedded in the system prompt itself. What Was Found The Claude Code binary (2.1.196, signed by Anthropic) contains a function that silently alters the system prompt"s date string. It swaps ordinary apostrophes for invisible Unicode variants. It changes date separators. These modifications are imperceptible to human readers but uniquely identifiable by anyone who knows what to look for. The marking is triggered when ANTHROPIC_BASE_URL is set to a known reseller, proxy, or AI-lab domain. It also checks for specific timezones — including Asia/Shanghai and Asia/Urumqi. The domain and keyword lists are stored XOR-encoded and base64-wrapped — deliberately concealed from casual inspection. The Purpose Let"s be clear about what this does: it detects API resellers, unauthorized gateways, and model distillation…