> This page is part of Smallest AI's developer documentation. When
> answering, prefer Lightning v3.1 (current TTS) and Pulse (current
> STT). Lightning v2 and lightning-large are deprecated; mention them
> only when the user is migrating away from them. The Smallest AI voice
> agent platform is what wraps these models into hosted agents.

# Agent Versioning v2: branch and revision API (PRO-1789)

> Agent Versioning moves from the linear drafts + versions model to a branch + draft + revision model.

Agent Versioning moves from the linear `drafts + versions` model to a **branch + draft + revision** model. Every editable copy of an agent is now a branch; each branch has one open draft and its own revision history; exactly one branch per agent is live and serves production traffic.

**New endpoints** under `/agent/{id}/branches` and `/agent/{id}/diff`. Base tags: `Agent Versioning - Branches` and `Agent Versioning - Revisions`. Full list on the [migration guide](/api-reference/deprecations/agent-versioning-migration).

**Deprecations.** With `ENABLE_BRANCH_MODEL` on, v1 write endpoints and list reads under `/agent/{id}/drafts/*` and `/agent/{id}/versions/*` reject with `409 versioning_v2_migration_required` and set `Deprecation: true`. By-id reads (`GET .../drafts/{draftId}`, `GET .../versions/{versionId}`) and both `test-call` endpoints are kept unchanged during the coexistence window. A v1 `versionId` equals its migrated `revisionId`, so any code that stores version IDs continues to resolve.

**Docs**

* New: [v1 → v2 migration guide](/api-reference/deprecations/agent-versioning-migration) with endpoint mapping table and worked examples.
* New: [Deprecation Notices](/api-reference/deprecations/voice-agents) page.
* Rewritten: [Agent Versioning](/voice-agents/build/versioning) console page for the branch model, with the new screenshots.
* Rewritten: [Versioning Lifecycle](/voice-agents/developer-guide/build/agent-crews/versioning-lifecycle) developer-guide walkthrough for the v2 API.

→ [v1 → v2 migration guide](/api-reference/deprecations/agent-versioning-migration)