Real Money, Fake Models: Deceptive Model Claims in Shadow APIs

A systematic audit of 17 shadow APIs used in 187 academic papers reveals widespread deception, with performance divergence up to 47.21% and identity verification failures in 45.83% of tests. These third-party services claim to provide access to frontier LLMs like GPT-5 and Gemini-2.5 but deliver inconsistent outputs, undermining research validity and reproducibility.