I run a small EU-based game whose scenes are generated through the Generative
Language API (paid tier, gemini-2.5-flash-lite today, migrating to
gemini-3.1-flash-lite in October). Under the EU AI Act, Article 50(2), I have to
mark AI-generated text in machine-readable form — unless I can rely on the model
provider’s own marking solution (Commission guidelines C(2026) 5054, point 74).
I could not find a definitive statement on whether API text output is watermarked:
- The SynthID overview mentions text watermarking only for "the Gemini app and
web experience" (deepmind.google/technologies/synthid)
- The developer docs present SynthID Text as a logits processor you apply to
your own model’s generation pipeline, not as an API property
(ai.google.dev/responsible/docs/safeguards/synthid)
- The Gemini 2.5 Flash-Lite model card does not mention watermarking at all
- The published verification routes (uploading content to Gemini chat, the
SynthID Detector portal) accept image, video and audio only — no text
(deepmind.google/models/synthid)
- An earlier answer in this forum said Google does not offer a public API to
detect text watermarks
I also inspected a live generateContent response — headers and JSON body carry
no provenance metadata, so my question is about the generated text itself.
My questions:
1. Is text returned by the API for these models SynthID-watermarked, or marked
with any machine-readable provenance signal? Is that documented anywhere I
can cite? Does the behaviour differ between the 2.5 and 3.1 model families?
2. If it IS watermarked: what detection route exists for a downstream provider,
or for people exposed to the content?
3. If it is NOT: is native text watermarking for the API planned?
A definitive answer either way — ideally from Google staff with a pointer to
official documentation — would help every developer here who has to write an
Article 50(2) compliance file. Thank you!