Bedrock Agent encountered error "The server encountered an error processing the Lambda response. Check the Lambda response and retry the request"

The error you're encountering with your Bedrock Agent is due to issues with the Lambda response format. There are several problems with your current response structure that need to be fixed:

1. Your JSON structure has syntax errors - there's an extra "response" key nested inside another "response" key, and there are some malformed entries like "function"."function".

2. The response format doesn't match what Bedrock Agents expects.

Here's how to properly format your Lambda response:

{
"messageVersion": "1.0",
"response": {
"actionGroup": "AnalyzeACLLog",
"function": "AnalyzeACLLog",
"functionResponse": {
"responseState": "SUCCESS",
"responseBody": {
"text/plain": "User Hanako has access to \\test\\test\\test.txt with rights: READ, WRITE, EXECUTE, FULL CONTROL"
}
}
}
}

Key changes to note:

• Fixed the nested "response" structure
• Added the required "responseState" field with "SUCCESS" value
• Changed "TEXT" to the proper content type "text/plain"
• Simplified the body to be a string rather than a complex JSON object

If you want to maintain the structured data, you could use a JSON content type instead:

{
"messageVersion": "1.0",
"response": {
"actionGroup": "AnalyzeACLLog",
"function": "AnalyzeACLLog",
"functionResponse": {
"responseState": "SUCCESS",
"responseBody": {
"application/json": {
"user": "Hanako",
"accessiblePaths": [
{
"Path": "\\test\\test\\test.txt",
"Rights": "READ, WRITE, EXECUTE, FULL CONTROL"
}
],
"message": "Hanako access"
}
}
}
}
}

If you continue to experience issues, you might also need to check:

• Lambda permissions: Ensure your Bedrock Agent has permission to invoke the Lambda function
• Action group configuration: Make sure there are no hyphens in your action group name (use underscores instead)
• Response format: Verify that your Lambda is returning a properly formatted JSON response

For error handling, you can also use "responseState": "FAILURE" or "responseState": "REPROMPT" with appropriate messages when needed.
Sources
Bedrock Agent hidden error | AWS re:Post
Bedrock error "The server encountered an error processing the Lambda response. Check the Lambda response and retry the request" | AWS re:Post
Bedrock Agents - Powertools for AWS Lambda (TypeScript)