# InvokeHarnessStreamOutput
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The streaming events returned by a harness invocation.

## Contents
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 ** contentBlockDelta **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-contentBlockDelta"></a>
A delta update to the current content block.  
Type: [HarnessContentBlockDeltaEvent](API_HarnessContentBlockDeltaEvent.md) object  
Required: No

 ** contentBlockStart **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-contentBlockStart"></a>
Indicates the start of a new content block.  
Type: [HarnessContentBlockStartEvent](API_HarnessContentBlockStartEvent.md) object  
Required: No

 ** contentBlockStop **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-contentBlockStop"></a>
Indicates the end of the current content block.  
Type: [HarnessContentBlockStopEvent](API_HarnessContentBlockStopEvent.md) object  
Required: No

 ** hookEvent **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-hookEvent"></a>
A lifecycle hook event emitted when a configured hook runs.  
Type: [HarnessHookEvent](API_HarnessHookEvent.md) object  
Required: No

 ** internalServerException **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-internalServerException"></a>
The exception that occurs when the service encounters an unexpected internal error. This is a temporary condition that will resolve itself with retries. We recommend implementing exponential backoff retry logic in your application.  
Type: Exception  
HTTP Status Code: 500  
Required: No

 ** messageStart **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-messageStart"></a>
Indicates the start of a new message from the agent.  
Type: [HarnessMessageStartEvent](API_HarnessMessageStartEvent.md) object  
Required: No

 ** messageStop **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-messageStop"></a>
Indicates the end of the current message.  
Type: [HarnessMessageStopEvent](API_HarnessMessageStopEvent.md) object  
Required: No

 ** metadata **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-metadata"></a>
Token usage and latency metrics for the invocation.  
Type: [HarnessMetadataEvent](API_HarnessMetadataEvent.md) object  
Required: No

 ** runtimeClientError **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-runtimeClientError"></a>
An error returned by the runtime container during agent execution.  
Type: Exception  
HTTP Status Code: 424  
Required: No

 ** validationException **   <a name="BedrockAgentCore-Type-InvokeHarnessStreamOutput-validationException"></a>
The exception that occurs when the input fails to satisfy the constraints specified by the service. Check the error message for details about which input parameter is invalid and correct your request.  
Type: Exception  
HTTP Status Code: 400  
Required: No

## See Also
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For more information about using this API in one of the language-specific Amazon SDKs, see the following:
+  [Amazon SDK for C\+\+](https://docs.amazonaws.cn/goto/SdkForCpp/bedrock-agentcore-2024-02-28/InvokeHarnessStreamOutput) 
+  [Amazon SDK for Java V2](https://docs.amazonaws.cn/goto/SdkForJavaV2/bedrock-agentcore-2024-02-28/InvokeHarnessStreamOutput) 
+  [Amazon SDK for Ruby V3](https://docs.amazonaws.cn/goto/SdkForRubyV3/bedrock-agentcore-2024-02-28/InvokeHarnessStreamOutput)