> ## Documentation Index
> Fetch the complete documentation index at: https://docs.synheart.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# 4. Install the runtime

> Install the on-device HSI runtime required by Synheart Core

The **Synheart Runtime** is the native engine that performs on-device human-state inference. The Synheart Core SDK loads it across the native bridge at startup, so it must be installed in your project before you initialize Core.

<Note>
  The runtime is **required for Synheart Core**. Standalone use of `synheart_wear`, `synheart_behavior`, or `synheart_session` does not require the runtime — see [Quickstart](/quickstart) for the standalone tracks.
</Note>

## Install

From your project root:

```bash theme={null}
synheart install runtime
```

This:

* Downloads the runtime artifact for your project's platforms.
* Writes a `synheart.lock` file pinning the exact versions.
* Places the native binaries where the Core SDK expects them.

## Channels and versions

```bash theme={null}
# Install from the latest channel (default)
synheart install runtime --channel latest

# Install a specific version (versions are v-prefixed)
synheart install runtime --version v1.2.3

# Restrict to a single platform
synheart install runtime --platform ios       # ios | android
```

<Note>
  `latest` is the channel in use today. Runtime artifacts are published per native target — use `--platform ios` or `--platform android`.
</Note>

## Reproducible installs

After the first install, commit `synheart.lock` to your repo. Anyone else on the project (and CI) installs the same versions with:

```bash theme={null}
synheart sync
```

## Inspect environment

```bash theme={null}
synheart env
synheart env --format json
```

Prints install paths, runtime version, and detected project type.

## Next

<Card title="Build your first integration" icon="rocket" href="/quickstart">
  Initialize Synheart Core and start receiving HSI updates.
</Card>