Change the text to speech model and voice, and tune how quickly the agent starts talking.
The Speak section controls text to speech (TTS): the voice your agent uses and
how quickly it starts talking. For how Listen, Think, and Speak fit together,
see the Execution Layer overview.
Open your project and go to the Speak section. Open the TTS model
dropdown and pick a model, then pick a Voice for it. As with Listen, the
dropdown separates SLNG models, hosted in your region, from BYOK,
models you reach with your own provider key.
Pick the TTS model first, then a voice that belongs to it.
Prefer a model from the SLNG models tab to synthesize in your region. To
use the BYOK tab, register your provider key first; see
Bring your own key.
Send the whole models object. A PATCH replaces it as a unit rather than
merging fields, so set the model with tts and the voice with tts_voice
and keep the other model fields as they are.
Prefer a model under the slng/ prefix (slng/fish/tts:s2.1-pro) to
synthesize in your region. A bare provider/model uses the provider’s model
through SLNG; add your own key (BYOK) to run it on your account. See
Choose a model route.
Each TTS model has its own set of voices, so pick the model first, then a voice
that belongs to it. For the models and voices a region and language allow, see
Which models are available.
models.tts_kwargs passes options through to the synthesis provider. In the
dashboard it lives under Advanced settings on the Speak section, in the
Overrides · JSON box. The same block holds the TTS timeout covered under
Keep Speak reliable.
Advanced settings on the Speak section: a TTS timeout and a JSON box for provider overrides.
The keys are specific to the model you picked, not to SLNG. For example, the Fish
models, such as the default slng/fish/tts:s2.1-pro, take a latency mode that
trades startup speed against audio quality (balanced by default). Send overrides
inside the whole models object, since a PATCH replaces it as a unit:
To find the options a model accepts, see that provider’s synthesis API reference.
SLNG applies a few limits: up to 128 keys, 64 KiB in total, and it rejects keys
that would carry credentials or change routing (api_key, base_url, headers,
model, and similar). Overrides apply to the primary TTS model, not to its
fallbacks.
Repeated lines such as greetings and confirmations are served from a cache
instead of being synthesized again, which cuts cost and latency. Caching is on by
default (tts_cache_enabled). For how it works and how to turn it off, see
TTS caching.
The TTS step can fall back to another model and has its own per-turn timeout
(models.fallbacks.tts, models.tts_first_audio_timeout_s). These work the same
way across all three sections. See
Reliability.
