Announced September 30, 2026, SynthID Bio guides amino-acid choices for sequences and fine-tunes part of AlphaFold 3 so coordinates carry a signature. DeepMind reported watermarked protein binders that still matched unmarked hit rate and binding affinity on VEGF-A, SARS-CoV-2 spike RBD, and PD-L1. The aim is a verification layer for DNA-synthesis screening and public databases, not an unbreakable seal — DeepMind lists deliberate tampering as an open problem.