sonic-latest or sonic-3-6: which Sume TTS id for repeatable narration

Pin the version if a series must match

Use sonic-3.6 (or another concrete id) when episodes must sound alike. sonic-latest is documented in the catalog as an alias for sonic-3.6, the provider's current stable Sonic release, not a dated snapshot. If that alias moves to a newer release, a request that said sonic-latest yesterday can produce a different sound tomorrow.

All five ids in the TTS Router cost the same: 38 micros list per character, 20,000 characters max, so the pin costs nothing extra.

What the catalog says about each id

A repeatable-series rule

Keep the model id, voice selector, language and speed in your own config and send them on every request. After a job completes, the job record echoes these values, with null for settings you did not send (Jobs and results). Compare the record from episode one with later ones to catch drift.

If an alias is the only thing you changed and the sound changed, the alias moved. Re-run the old line on the pinned id to confirm.

Cost check

A 6,000-character episode costs 6,000 x 0.00475 = 28.5 cents, rounded up to 29 cents, on any of the five ids. Twelve episodes are 12 x 29 = 348 cents, or $3.48.

Upgrading deliberately

When a newer concrete Sonic id appears in the catalog, treat the move as a content change. Generate your standard test paragraph on the old and new ids, listen to both, and only then switch the pinned id in your config. Keep the old take as a reference so you can show what changed.

The catalog lists older concrete releases too, sonic-3.5 and sonic-3, so a series started on one of them can stay on it as long as it is listed.

Why the preview channel needs care

sonic-preview is a provider beta. Output and availability can change without notice, so it is a poor choice for anything that must be reproducible. The catalog also says pro voice clones are incompatible with it, and those requests fail with voice_model_mismatch rather than falling back. If you use a clone, pin a concrete stable id and test one line before queuing a long script.