OpenAI updated its GPT-Live voice model on July 31 to embed Google DeepMind's SynthID watermarking into all audio generated through ChatGPT Voice and the OpenAI API, and simultaneously opened a verification API that lets any developer or organization run automated provenance checks against incoming audio files. The update arrives one day before EU AI Act Article 50 transparency obligations take effect across all 27 member states. The watermark is invisible and inaudible, and any third party can now query whether it is there. OpenAI's public verification tool can detect OpenAI provenance signals in supported audio files, and API access for verification allows developers and organizations to incorporate provenance checks into their own workflows. The update builds on OpenAI's image watermarking rollout from May 19, when every image generated by ChatGPT, Codex, and the OpenAI API began carrying both a C2PA manifest and a SynthID watermark. For voice output, SynthID operates in the spectrogram, converting the audio waveform into a time-frequency representation, encoding a watermark pattern using psychoacoustic masking principles, and reconstructing the waveform. The watermark survives MP3 compression, including aggressive 128 kbps encoding, speed and pitch shifts, and the "analog hole" of playing digital audio through a speaker and re-recording it through a microphone.