Gemini TTS stateless voice keys expire in 7 days: Sume saved voices

Gemini 3.8 Flash TTS lets you design or replicate a voice, and the speech guide says projects can store up to 200 voices when you use stateful storage, while stateless voice keys expire in 7 days. If you plan a series, that expiry is the thing to design around. A Sume voice is saved in the workspace and reused through its voice id.

What the vendor page says

The Gemini API speech guide lists gemini-3.8-flash-tts and gemini-3.8-flash-lite-tts. Both support voice design and voice replication. It states a maximum of 200 voices per project with stateful storage, and that stateless keys expire in 7 days. It is a limit worth reading before you build a show around a designed voice.

We make no claim here about how to use those keys. The point is only that the two storage modes have different lifetimes, and a series needs the longer one.

How a Sume voice is stored

A voice made with voices_create, by description or by clone, is a row in Assets, then Voices, in the workspace. Each ready row has a voi_ id, a slug, a sample_url, and a cartesia_voice_id. That last value is what you pass as voice.id to Sume TTS.

The workspace owns the row, and teammates can use it.

Pin it for a series

For a show with many episodes, record these three things once, then reuse them.

• The voice's cartesia_voice_id.
• The generation_config you settled on: speed 0.6 to 1.5, volume 0.5 to 2, and an emotion string.
• The language code the voice was tuned for.

What this does not give you

Sume's voices are Cartesia Sonic 3.6 voices. They are not Gemini voices, and a Gemini-designed voice does not move to Sume as an id. If you want the Gemini sound, you would clone from a recording of it through voices_create with an https audio_url, and that clone is a new Sume voice with its own id. Check the rights on any recording before you clone it.

If your series is already in Gemini and works, you do not have to move. The comparison matters when the expiry or the project cap becomes a constraint on how you run it.

A practical rule

Treat any voice that only exists as a temporary key as disposable, and treat a saved voice as an asset. For a series, create the voice once, play its sample, and write its id into your episode template. Then an expiry date is no longer part of your production schedule.

Check the vendor page again before you commit; limits like these change as models move out of preview.