# Versioning

> How the API and the realtime protocol change, and what Kheelona promises not to break.

Source: https://docs.voice.kheelona.com/policies/versioning/

Kheelona Voice has two versioned surfaces. Both are at version 1.

| Surface | Version | Where you see it |
|---|---|---|
| The REST API | `v1` | The path: `/v1/sessions`. |
| The realtime protocol | `kheelona.v1` | The WebSocket subprotocol: `kheelona.v1`. |

## What is not a breaking change

Kheelona may add these at any time, without a new version:

- new endpoints, and new optional request fields;
- new fields in responses and in realtime events;
- new event types;
- new error codes;
- new voices, languages and options.

**Your client must ignore what it does not know:** unknown fields, unknown event types and unknown error codes. Treat an
unknown error code by its HTTP status and its `fatal` flag. The other direction is strict: `POST /v1/sessions` refuses
fields it does not know, so send only documented fields. See [Errors and retries](https://docs.voice.kheelona.com/guides/errors-and-retries.md).

## What is a breaking change

Removing or renaming anything, or changing what something means, is a breaking change. It only ever ships as a new
version: `v2` for the API, `kheelona.v2` for the protocol.

## How long the old version lasts

When a new version arrives, both versions are supported side by side for **at least six months**. The
[changelog](https://docs.voice.kheelona.com/policies/changelog.md) announces it.

## The browser SDK

The browser SDK has its own version number, in the file name of the package you received (`kheelona-voice-<version>.tgz`). It follows semantic versioning. See the [browser SDK guide](https://docs.voice.kheelona.com/guides/browser-sdk.md#sdk-version).