Per-Response Model Identity Disclosure in Frontier AI APIs: Cross-Vendor Comparison Data (June 2026)

Controlled comparison of per-response model identity disclosure across Google Gemini API and Anthropic Claude API. Google returns model_version and x-gemini-service-tier in every response (8/8 tests). Anthropic returns no equivalent fields (0/4 tests); response.model echoes the requested model without confirming the served model. Demonstrates that routing transparency is technically feasible and its absence is a design choice.针对Google Gemini API与Anthropic Claude API的逐响应模型身份披露情况开展了受控对照比较。在全部8次测试中，Google的API会在每条响应中返回model_version与x-gemini-service-tier字段（8/8次测试均返回）。Anthropic的API则未返回任何等效字段（0/4次测试均未返回）；其响应中的response.model字段仅会回显请求的模型名称，并未确认实际提供服务的模型身份。该研究表明，路由透明度在技术上具备可行性，而不提供该透明度则属于一种设计选择。