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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.

independent security research, developer community