# Update Prompt

Voice Agent

The `UpdatePrompt` message is a JSON message that you can use to update the system prompt of the agent.

## Purpose

The `UpdatePrompt` message is a JSON message that allows you to update the system prompt of the agent. `UpdatePrompt` will add to – not replace – the current prompt. This flexibility enables real-time adjustments to the agent's behavior, ensuring a more dynamic and responsive interaction tailored to the evolving needs of the conversation.

Prompt length is limited to 25,000 characters for managed LLMs and unlimited for BYO LLMs.

## Example Payloads

To send the `UpdatePrompt` message, you need to send the following JSON message to the server:

**`JSON`**

```json JSON
{
  "type": "UpdatePrompt",
  "prompt": "" // The new system prompt
}
```

Upon receiving the `UpdatePrompt` message, the server will process all remaining audio data and return a [`PromptUpdated`](/guides/self-hosted-deployments-3-voice-agent-acknowledgements#promptupdated) message.

**`JSON`**

```json JSON
{
    "type": "PromptUpdated"
}
```

## Related pages

- [Inputs: Client Messages](./self-hosted-deployments-3-voice-agent-inputs.md)
- [Settings](./self-hosted-deployments-3-voice-agent-settings.md)
- [Update Listen](./self-hosted-deployments-3-voice-agent-update-listen.md)
- [Update Think](./self-hosted-deployments-3-voice-agent-update-think.md)
- [Update Speak](./self-hosted-deployments-3-voice-agent-update-speak.md)
- [Inject Agent](./self-hosted-deployments-3-voice-agent-inject-agent-message.md)
- [Inject User](./self-hosted-deployments-3-voice-agent-inject-user-message.md)
- [Force End Turn](./self-hosted-deployments-3-voice-agent-force-end-turn.md)
- [Agent Keep Alive](./self-hosted-deployments-3-agent-keep-alive.md)

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