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

# MessageDeltaEvent

> A streamed chunk of agent output text.

## Properties

**aborted** `boolean` *required*

The message was aborted; discard any text accumulated for its `messageId`.

**chain** `Chain` *required*

Which conversation chain the message belongs to (`side` = sidechain, not the main transcript).

**messageId** `undefined | string` *required*

Correlation id of the streaming message the chunk belongs to.

**overwrite** `boolean` *required*

The chunk replaces the message's prior content instead of appending.

**text** `string` *required*

The new text in this chunk.

**type** `"message_delta"` *required*

**update** `SessionUpdate` *required*


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