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Documentation Index

Fetch the complete documentation index at: https://docs.cartesia.ai/llms.txt

Use this file to discover all available pages before exploring further.

Sonic 3.5 is a streaming TTS model, with high naturalness, accurate transcript following, and industry-leading latency. Key Features:
  • 42 languages supported, including English, Hindi, Spanish, French, German, Japanese, Hebrew, and more
  • Natural, expressive speech with strong pacing and emotional expression for conversational and support-style transcripts
  • Clean audio quality across all languages and voices
  • Natural alphanumeric handling — confirmation codes, order numbers, phone numbers, IDs, and emails sound natural without preprocessing, in every supported language
  • Accurate English pronunciation in context, including heteronyms like read, bass, and bow

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Voice selection

Choosing voices that work best for your use case is key to getting the best performance out of Sonic 3.5. The recommendations below are starting points carried over from Sonic 3 — they work as-is on Sonic 3.5. We’ll be publishing 3.5-specific picks in the coming weeks.
  • For voice agents: We’ve found stable, realistic voices work better for voice agents. Example American English voices include Katie (ID: f786b574-daa5-4673-aa0c-cbe3e8534c02) and Jameson (ID: a5136bf9-224c-4d76-b823-52bd5efcffcc).
For more information and recommendations, see Choosing a Voice.

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Language support

Sonic 3.5 supports the following languages:
English (en)French (fr)German (de)Spanish (es)
Portuguese (pt)Chinese (zh)Japanese (ja)Hindi (hi)
Italian (it)Korean (ko)Dutch (nl)Polish (pl)
Russian (ru)Swedish (sv)Turkish (tr)Tagalog (tl)
Bulgarian (bg)Romanian (ro)Arabic (ar)Czech (cs)
Greek (el)Finnish (fi)Croatian (hr)Malay (ms)
Slovak (sk)Danish (da)Tamil (ta)Ukrainian (uk)
Hungarian (hu)Norwegian (no)Vietnamese (vi)Bengali (bn)
Thai (th)Hebrew (he)Georgian (ka)Indonesian (id)
Telugu (te)Gujarati (gu)Kannada (kn)Malayalam (ml)
Marathi (mr)Punjabi (pa)

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Selecting a Model

SnapshotRelease DateLanguagesStatus
sonic-3.5-2026-05-04May 4, 2026en, de, es, fr, ja, pt, zh, hi, ko, it, nl, pl, ru, sv, tr, tl, bg, ro, ar, cs, el, fi, hr, ms, sk, da, ta, uk, hu, no, vi, bn, th, he, ka, id, te, gu, kn, ml, mr, paStable
the latest stable snapshot of the model When making API calls, you can specify either: 
# Use the base model
# (automatically routes to the latest stable snapshot)
model_id = "sonic-3.5"

# Or specify a particular snapshot for consistency
model_id = "sonic-3.5-2026-05-04"

# Try the latest (beta) model (can be 'hot swapped')
model_id = "sonic-latest"

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Continuous updates and model snapshots

All models have a base model name (e.g. sonic-3.5) and a dated snapshot (e.g. sonic-3.5-2026-05-04). Using the base model will automatically keep you up to date with the most recent stable snapshot of that model. If pinning a specific version is important for your use case, we recommend using the dated version. For testing our latest capabilities, we recommend using sonic-latest, which is a non-snapshotted version. sonic-latest can be updated with no notice, and is not recommended for production. To summarize:
Model IDModel update behaviorRecommended for
sonic-3.5-YYYY-MM-DDSnapshotted, will never changeCustomers who want to run internal evals before any updates
sonic-3.5Will be updated to point to the most recent stable snapshotCustomers who want stable releases, but want to be up-to-date with the recent capabilities
sonic-latestWill always be updated to our latest beta releasesTesting purposes

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Switching from Sonic 3?

If you’re already using Sonic 3, see Migrating from Sonic 3 to Sonic 3.5 for what’s new and what to know before you switch.

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Older Models

For information on sonic-3, sonic-2, sonic-turbo, and sonic, see our page on Older Models.