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

# Events

> Documentation for the events used in the Agent User Interaction Protocol SDK

# Events

The Agent User Interaction Protocol SDK uses a streaming event-based
architecture. Events are the fundamental units of communication between agents
and the frontend. This section documents the event types and their properties.

## EventType Enum

The `EventType` enum defines all possible event types in the system:

```typescript theme={null}
enum EventType {
  TEXT_MESSAGE_START = "TEXT_MESSAGE_START",
  TEXT_MESSAGE_CONTENT = "TEXT_MESSAGE_CONTENT",
  TEXT_MESSAGE_END = "TEXT_MESSAGE_END",
  TOOL_CALL_START = "TOOL_CALL_START",
  TOOL_CALL_ARGS = "TOOL_CALL_ARGS",
  TOOL_CALL_END = "TOOL_CALL_END",
  STATE_SNAPSHOT = "STATE_SNAPSHOT",
  STATE_DELTA = "STATE_DELTA",
  MESSAGES_SNAPSHOT = "MESSAGES_SNAPSHOT",
  RAW = "RAW",
  CUSTOM = "CUSTOM",
  RUN_STARTED = "RUN_STARTED",
  RUN_FINISHED = "RUN_FINISHED",
  RUN_ERROR = "RUN_ERROR",
  STEP_STARTED = "STEP_STARTED",
  STEP_FINISHED = "STEP_FINISHED",
}
```

## BaseEvent

All events inherit from the `BaseEvent` type, which provides common properties
shared across all event types.

```typescript theme={null}
type BaseEvent = {
  type: EventType // Discriminator field
  timestamp?: number
  rawEvent?: any
}
```

| Property    | Type                | Description                                           |
| ----------- | ------------------- | ----------------------------------------------------- |
| `type`      | `EventType`         | The type of event (discriminator field for the union) |
| `timestamp` | `number` (optional) | Timestamp when the event was created                  |
| `rawEvent`  | `any` (optional)    | Original event data if this event was transformed     |

## Lifecycle Events

These events represent the lifecycle of an agent run.

### RunStartedEvent

Signals the start of an agent run.

```typescript theme={null}
type RunStartedEvent = BaseEvent & {
  type: EventType.RUN_STARTED
  threadId: string
  runId: string
}
```

| Property   | Type     | Description                   |
| ---------- | -------- | ----------------------------- |
| `threadId` | `string` | ID of the conversation thread |
| `runId`    | `string` | ID of the agent run           |

### RunFinishedEvent

Signals the successful completion of an agent run.

```typescript theme={null}
type RunFinishedEvent = BaseEvent & {
  type: EventType.RUN_FINISHED
  threadId: string
  runId: string
}
```

| Property   | Type     | Description                   |
| ---------- | -------- | ----------------------------- |
| `threadId` | `string` | ID of the conversation thread |
| `runId`    | `string` | ID of the agent run           |

### RunErrorEvent

Signals an error during an agent run.

```typescript theme={null}
type RunErrorEvent = BaseEvent & {
  type: EventType.RUN_ERROR
  message: string
  code?: string
}
```

| Property  | Type                | Description   |
| --------- | ------------------- | ------------- |
| `message` | `string`            | Error message |
| `code`    | `string` (optional) | Error code    |

### StepStartedEvent

Signals the start of a step within an agent run.

```typescript theme={null}
type StepStartedEvent = BaseEvent & {
  type: EventType.STEP_STARTED
  stepName: string
}
```

| Property   | Type     | Description      |
| ---------- | -------- | ---------------- |
| `stepName` | `string` | Name of the step |

### StepFinishedEvent

Signals the completion of a step within an agent run.

```typescript theme={null}
type StepFinishedEvent = BaseEvent & {
  type: EventType.STEP_FINISHED
  stepName: string
}
```

| Property   | Type     | Description      |
| ---------- | -------- | ---------------- |
| `stepName` | `string` | Name of the step |

## Text Message Events

These events represent the lifecycle of text messages in a conversation.

### TextMessageStartEvent

Signals the start of a text message.

```typescript theme={null}
type TextMessageStartEvent = BaseEvent & {
  type: EventType.TEXT_MESSAGE_START
  messageId: string
  role: "assistant"
}
```

| Property    | Type          | Description                       |
| ----------- | ------------- | --------------------------------- |
| `messageId` | `string`      | Unique identifier for the message |
| `role`      | `"assistant"` | Role is always "assistant"        |

### TextMessageContentEvent

Represents a chunk of content in a streaming text message.

```typescript theme={null}
type TextMessageContentEvent = BaseEvent & {
  type: EventType.TEXT_MESSAGE_CONTENT
  messageId: string
  delta: string // Non-empty string
}
```

| Property    | Type     | Description                               |
| ----------- | -------- | ----------------------------------------- |
| `messageId` | `string` | Matches the ID from TextMessageStartEvent |
| `delta`     | `string` | Text content chunk (non-empty)            |

### TextMessageEndEvent

Signals the end of a text message.

```typescript theme={null}
type TextMessageEndEvent = BaseEvent & {
  type: EventType.TEXT_MESSAGE_END
  messageId: string
}
```

| Property    | Type     | Description                               |
| ----------- | -------- | ----------------------------------------- |
| `messageId` | `string` | Matches the ID from TextMessageStartEvent |

## Tool Call Events

These events represent the lifecycle of tool calls made by agents.

### ToolCallStartEvent

Signals the start of a tool call.

```typescript theme={null}
type ToolCallStartEvent = BaseEvent & {
  type: EventType.TOOL_CALL_START
  toolCallId: string
  toolCallName: string
  parentMessageId?: string
}
```

| Property          | Type                | Description                         |
| ----------------- | ------------------- | ----------------------------------- |
| `toolCallId`      | `string`            | Unique identifier for the tool call |
| `toolCallName`    | `string`            | Name of the tool being called       |
| `parentMessageId` | `string` (optional) | ID of the parent message            |

### ToolCallArgsEvent

Represents a chunk of argument data for a tool call.

```typescript theme={null}
type ToolCallArgsEvent = BaseEvent & {
  type: EventType.TOOL_CALL_ARGS
  toolCallId: string
  delta: string
}
```

| Property     | Type     | Description                            |
| ------------ | -------- | -------------------------------------- |
| `toolCallId` | `string` | Matches the ID from ToolCallStartEvent |
| `delta`      | `string` | Argument data chunk                    |

### ToolCallEndEvent

Signals the end of a tool call.

```typescript theme={null}
type ToolCallEndEvent = BaseEvent & {
  type: EventType.TOOL_CALL_END
  toolCallId: string
}
```

| Property     | Type     | Description                            |
| ------------ | -------- | -------------------------------------- |
| `toolCallId` | `string` | Matches the ID from ToolCallStartEvent |

## State Management Events

These events are used to manage agent state.

### StateSnapshotEvent

Provides a complete snapshot of an agent's state.

```typescript theme={null}
type StateSnapshotEvent = BaseEvent & {
  type: EventType.STATE_SNAPSHOT
  snapshot: any // StateSchema
}
```

| Property   | Type  | Description             |
| ---------- | ----- | ----------------------- |
| `snapshot` | `any` | Complete state snapshot |

### StateDeltaEvent

Provides a partial update to an agent's state using JSON Patch.

```typescript theme={null}
type StateDeltaEvent = BaseEvent & {
  type: EventType.STATE_DELTA
  delta: any[] // JSON Patch operations (RFC 6902)
}
```

| Property | Type    | Description                    |
| -------- | ------- | ------------------------------ |
| `delta`  | `any[]` | Array of JSON Patch operations |

### MessagesSnapshotEvent

Provides a snapshot of all messages in a conversation.

```typescript theme={null}
type MessagesSnapshotEvent = BaseEvent & {
  type: EventType.MESSAGES_SNAPSHOT
  messages: Message[]
}
```

| Property   | Type        | Description              |
| ---------- | ----------- | ------------------------ |
| `messages` | `Message[]` | Array of message objects |

## Special Events

### RawEvent

Used to pass through events from external systems.

```typescript theme={null}
type RawEvent = BaseEvent & {
  type: EventType.RAW
  event: any
  source?: string
}
```

| Property | Type                | Description         |
| -------- | ------------------- | ------------------- |
| `event`  | `any`               | Original event data |
| `source` | `string` (optional) | Source of the event |

### CustomEvent

Used for application-specific custom events.

```typescript theme={null}
type CustomEvent = BaseEvent & {
  type: EventType.CUSTOM
  name: string
  value: any
}
```

| Property | Type     | Description                     |
| -------- | -------- | ------------------------------- |
| `name`   | `string` | Name of the custom event        |
| `value`  | `any`    | Value associated with the event |

## Event Schemas

The SDK uses Zod schemas to validate events:

```typescript theme={null}
const EventSchemas = z.discriminatedUnion("type", [
  TextMessageStartEventSchema,
  TextMessageContentEventSchema,
  TextMessageEndEventSchema,
  ToolCallStartEventSchema,
  ToolCallArgsEventSchema,
  ToolCallEndEventSchema,
  StateSnapshotEventSchema,
  StateDeltaEventSchema,
  MessagesSnapshotEventSchema,
  RawEventSchema,
  CustomEventSchema,
  RunStartedEventSchema,
  RunFinishedEventSchema,
  RunErrorEventSchema,
  StepStartedEventSchema,
  StepFinishedEventSchema,
])
```

This allows for runtime validation of events and provides TypeScript type
inference.