# SendMessageContentBlockStartEvent
<a name="API_SendMessageContentBlockStartEvent"></a>

Event emitted when a new content block starts

## Contents
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 ** id **   <a name="devopsagent-Type-SendMessageContentBlockStartEvent-id"></a>
Block identifier  
Type: String  
Required: No

 ** index **   <a name="devopsagent-Type-SendMessageContentBlockStartEvent-index"></a>
Zero-based index of the content block  
Type: Integer  
Required: No

 ** parentId **   <a name="devopsagent-Type-SendMessageContentBlockStartEvent-parentId"></a>
Optional parent block ID for nested content blocks (e.g. subagent tool calls)  
Type: String  
Required: No

 ** sequenceNumber **   <a name="devopsagent-Type-SendMessageContentBlockStartEvent-sequenceNumber"></a>
Event sequence number  
Type: Integer  
Required: No

 ** type **   <a name="devopsagent-Type-SendMessageContentBlockStartEvent-type"></a>
The type of content in this block  
Type: String  
Required: No

## See Also
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For more information about using this API in one of the language-specific AWS SDKs, see the following:
+  [AWS SDK for C\+\+](https://docs.aws.amazon.com/goto/SdkForCpp/devops-agent-2026-01-01/SendMessageContentBlockStartEvent) 
+  [AWS SDK for Java V2](https://docs.aws.amazon.com/goto/SdkForJavaV2/devops-agent-2026-01-01/SendMessageContentBlockStartEvent) 
+  [AWS SDK for Ruby V3](https://docs.aws.amazon.com/goto/SdkForRubyV3/devops-agent-2026-01-01/SendMessageContentBlockStartEvent)