Gemini 3.8 Flash TTS takes 8,192 input tokens: splitting a long script
Gemini 3.8 Flash TTS lists 8,192 input tokens and 16,384 output tokens. Sume TTS takes 20,000 characters per job. Here is how to split a long script.
Gemini 3.8 Flash TTS lists an input limit of 8,192 tokens and an output limit of 16,384 tokens on its model page, so a long narration needs to be split into several requests. Sume TTS 1.0 accepts 1 to 20,000 characters per job and fails audio over 1,200 seconds.
The limits side by side
Older posts said Google named no text limit; the current model page now does.
| Item | Gemini 3.8 Flash TTS | Sume TTS 1.0 |
|---|---|---|
| Input | 8,192 tokens | 1 to 20,000 characters |
| Output | 16,384 tokens | Audio up to 1,200 s, else tts_duration_exceeded |
| Unit | Tokens | Characters |
Split on sentence boundaries
Tokens are not characters, so do not guess a character cutoff for Gemini. Count tokens with Google's tooling and leave headroom. Split at sentence or paragraph ends so each clip starts and stops naturally, and keep the same voice and style text on every request.
Google treats the text as a verbatim transcript, per the speech generation docs, so keep style direction in the style field rather than the text, or it may be read aloud in every chunk.
On Sume
A 20,000-character ceiling covers most ad and explainer scripts in one job. Beyond that, split the script and join the clips with timeline audio, which concatenates 1 to 20 parts for a flat $0.01 per job (timeline audio docs). That is a published limit, not a promise about how seams sound: listen to every join.
Sume does not split text for you. You choose the break points.
Sources
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Written by Sume