# Inject Agent

Voice Agent

The `InjectAgentMessage` message is a JSON message you can send to immediately trigger an agent statement.

## Purpose

`InjectAgentMessage` lets your server put words in the agent's mouth mid-conversation. The optional `behavior` field controls how the message interacts with any ongoing user or agent turn: wait for silence, queue within the current turn, or interrupt the current turn.

## Fields

| Field      | Type   | Required | Description                                                                                                               |
| ---------- | ------ | -------- | ------------------------------------------------------------------------------------------------------------------------- |
| `type`     | string | Yes      | Must be `"InjectAgentMessage"`.                                                                                           |
| `message`  | string | Yes      | The statement the agent should say.                                                                                       |
| `behavior` | string | No       | How the injection interacts with the current turn: `"default"`, `"queue"`, or `"interrupt"`. Uses `"default"` if omitted. |

### `behavior` values

- **`default`**: the agent speaks only if neither the user nor the agent is mid-turn. If a turn is in progress, the server rejects the request and replies with [`InjectionRefused`](#injectionrefused). This matches the original `InjectAgentMessage` behavior.
- **`queue`**: the server appends the message after any `ConversationText` that is already queued, without interrupting the current agent turn or the in-flight think response. If nothing is queued, the agent speaks the message immediately.
- **`interrupt`**: the agent immediately speaks.
  - If the agent was already speaking, it interrupts any current speech and replaces it with the new message.
  - If the user is speaking, the agent interrupts with the new message. However, the user's continued speech triggers [`UserStartedSpeaking`](/guides/self-hosted-deployments-3-voice-agent-user-started-speaking), which quickly interrupts the agent, ensuring the conversation continues forward.

## Example Payloads

### `default`: wait for silence

**`JSON`**

```json JSON
{
  "type": "InjectAgentMessage",
  "behavior": "default",
  "message": "Are you still on the line?"
}
```

### `queue`: append after any current ConversationText

**`JSON`**

```json JSON
{
  "type": "InjectAgentMessage",
  "behavior": "queue",
  "message": "Thanks for your patience, the system is still loading."
}
```

### `interrupt`: replace the current agent speech

**`JSON`**

```json JSON
{
  "type": "InjectAgentMessage",
  "behavior": "interrupt",
  "message": "Sorry to cut in — let me correct that."
}
```

## Responses

The server sends an [`AgentAudioDone`](/guides/self-hosted-deployments-3-voice-agent-agent-audio-done) message after the last `InjectAgentMessage` is spoken.

**`JSON`**

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

### `InjectionRefused`

When `behavior` is `default` or `queue` and the request arrives while the _user_ is mid-turn, the server ignores the request and replies with `InjectionRefused`. If the _agent_ is mid-turn, the server returns `InjectionRefused` only when `behavior` is `default`. The `interrupt` behavior is never refused: the agent speaks even while the user or agent is mid-turn.

**`JSON`**

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

## Use Cases

Pick the `behavior` value that matches what you want to happen to the current turn.

### When to use `default`

Use `default` when the injection is only appropriate during silence and you would rather drop it than step on the conversation.

- Prompting the user to continue if they have been silent for a while ("Are you still on the line?").
- Optional nudges where being ignored is acceptable if the caller is already talking.

### When to use `queue`

Use `queue` when you want the agent to say something _after_ whatever it is currently saying, without stepping on it. This is the right choice for filler during function calls, where the model has already emitted pre-function narration and you want to extend it rather than replace it.

- Filling silence during a long-running function call ("One moment while I pull that up") without cutting off the model's current response.
- Chaining a follow-up sentence after the agent finishes its current turn ("...and I've also emailed you a copy.").
- Streaming progress updates from a backend job so the caller hears them in order.

### When to use `interrupt`

Use `interrupt` when the new message must take over immediately, even if it means cutting off the agent's current speech. Because the agent speaks regardless of whether the user is talking, reserve this for time-sensitive corrections and overrides.

- Correcting the agent mid-sentence when it is saying something wrong or outdated.
- Delivering an urgent update that should replace whatever the agent is currently saying.
- Overriding the current turn from a supervisor or backend system that has higher-priority information.

## 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)
- [Update Prompt](./self-hosted-deployments-3-voice-agent-update-prompt.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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