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

# Events

> Subscribe to real-time events from the Synapse session

The core SDK is event-driven. After [starting a session](/ai-tools/synapse/core/quickstart#the-lifecycle), subscribe to events to receive streamed message chunks, tips, tool calls, and lifecycle signals. Drive your UI off these events.

## Subscribing

```ts theme={null}
import { SYNAPSE_REALTIME_EVENTS } from "@eka-care/medassist-core";

function onChunk(evt) {
  appendToCurrentMessage(evt.data.text);
}

// Register
sdk.on(SYNAPSE_REALTIME_EVENTS.MESSAGE_CHUNK, onChunk);

// Remove (pass the same function reference)
sdk.off(SYNAPSE_REALTIME_EVENTS.MESSAGE_CHUNK, onChunk);
```

<Warning>
  `off()` requires the **same function reference** you passed to `on()`. Inline arrow functions can't be removed — keep a reference if you need to unsubscribe.
</Warning>

## Event reference

Use the `SYNAPSE_REALTIME_EVENTS` enum — never hardcode the string values.

| Event              | Fires when                                                                                                      |
| ------------------ | --------------------------------------------------------------------------------------------------------------- |
| `CONNECTED`        | The session connects.                                                                                           |
| `DISCONNECTED`     | The connection drops. Payload carries a `DisconnectionReason`.                                                  |
| `PROGRESS_MESSAGE` | The agent emits an interim "working on it" status.                                                              |
| `MESSAGE_CHUNK`    | A streamed slice of the assistant's reply. Concatenate these.                                                   |
| `TIPS_MESSAGE`     | Suggested follow-up prompts (`data.tips`).                                                                      |
| `END_OF_STREAM`    | The current assistant message is complete.                                                                      |
| `ERROR`            | A stream or server error. See [error codes](/ai-tools/synapse/core/api-reference#synapse-realtime-error-codes). |
| `TOOL_CALL`        | The agent invokes a tool / asks for input. See [Tool calls](/ai-tools/synapse/core/tool-calls).                 |
| `TOOL_START`       | A tool begins executing.                                                                                        |
| `TOOL_END`         | A tool finishes executing.                                                                                      |
| `AUDIO_TRANSCRIPT` | A transcript of recorded audio. See [Voice & audio](/ai-tools/synapse/core/voice).                              |

## Event payload

Every listener receives a `SynapseRealTimeEventData` object:

```ts theme={null}
type SynapseRealTimeEventData = {
  data: {
    text?: string;     // message / chunk text
    tips?: string[];   // suggested follow-ups
    name?: string;     // tool or entity name
  } & Partial<ToolCallData>; // tool fields on TOOL_CALL events
  messageId?: string;
  timestamp?: number;
};
```

## Streaming a message

A single assistant reply arrives as many `MESSAGE_CHUNK` events followed by one `END_OF_STREAM`. Accumulate chunks, then finalize:

```ts theme={null}
let buffer = "";

sdk.on(SYNAPSE_REALTIME_EVENTS.MESSAGE_CHUNK, (evt) => {
  buffer += evt.data.text ?? "";
  renderStreaming(buffer);
});

sdk.on(SYNAPSE_REALTIME_EVENTS.END_OF_STREAM, (evt) => {
  commitMessage(buffer, evt.messageId);
  buffer = "";
});

sdk.on(SYNAPSE_REALTIME_EVENTS.PROGRESS_MESSAGE, (evt) => {
  showTypingIndicator(evt.data.text);
});
```

## Next steps

<Card title="Tool calls & elicitation" icon="hand-pointer" href="/ai-tools/synapse/core/tool-calls">
  Handle `TOOL_CALL` events — render inputs and send results back.
</Card>