a researcher discovered that anthropic's claude code silently embeds invisible unicode steganographic markers into system prompts when requests are routed through third-party api proxies. the undisclosed fingerprinting system includes a blocklist of chinese ai providers — deepseek, zhipu, baidu, alibaba — with no documentation accompanying the behavior. a major ai lab covertly classifying and fingerprinting usage by national origin of api intermediaries, without disclosure to users or developers, is structurally unusual regardless of stated intent.