February 2026
Line
- History Management API: You can add or replace the history provided to your agent, for example, to summarize a long conversation.
- Custom User Events: You can send bidirectional custom events between your client and the agent. You could use this, for example, if you have a web application with UI interactions.
- Uninterruptible Messages: You can set messages as uninterruptible. A common use case is a legal disclaimer at the beginning of a call.
- End Tool Call Improvements: The default end call tool call is more conservative to prevent calls from ending prematurely.
API
- Increased reliability of API connections
Client libraries
- cartesia-python v3.0.0 (Feb 9). See full details in cartesia-python releases.
Playground
- Shipped a new TTS page
- Shipped a new Voice Creation page
- Shipped a new Agents page
Voice changes
- Voice Library: 39 new voices across 21 locales
January 2026
API
- Regionalization — Calls routed to US, EU, APAC by origin.
- Parameterized outbound calls — Docs
- Pronunciation dictionaries — Docs
Model changes
- Sonic-3 model versioning scheme introduced
- New preview track:
sonic-3-latest(continuous updates for early access and feedback). - Stable track:
sonic-3always points to the most recent stable release. - Immutable dated snapshots:
sonic-3-YYYY-MM-DDnever change. - Details: Continuous updates and model snapshots
- New preview track:
- Promotion to stable checkpoint:
sonic-3-2026-01-12- Included improvements: consistent speed & volume, custom IPA pronunciations with stronger adherence, Hindi prosody improvements, Korean prosody/intonation improvements.
Voice changes
- Featured Voices launched — Curated set of 30+ best-performing voices (e.g. Cathy, Henry).
- Voice Library — December: 25 new voices across 6 languages.
- Voice Library — January: 9 Spanish voices (Mexican, Colombian, Castilian).
Playground
- Voice library usability improvements (test with your own scripts, call an agent per voice).
- One-click Report Issue on TTS Playground.
- Mini voice picker (recently used + saved) on TTS page.
- PVC UI + reliability (loading skeletons, error messages, better behavior with large datasets and silence).
Line
- Line SDK v0.2 — Repo. Improved DX, long-running tool-call handling, committed turns, better turn-taking and transcription.