| Issue | Cause | Fix |
|---|---|---|
| No Lambda logs | API route or stage incorrect | Confirm correct URL and deployment |
| Annotated image empty | Lambda returned error, not image | Log in Lambda, check response size |
| Truncated File Read | Incomplete image sent | Validate full base64 image |
| SageMaker 500 error | Model crashed | Check CloudWatch logs for traceback |
| curl works, Python fails | Incorrect headers or data format | Match curl: use data=image_bytes |
- API Gateway: Enable Access Logs.
- Lambda: View logs in
/aws/lambda/{function-name}. - SageMaker: Logs in
/aws/sagemaker/Endpoints/{endpoint-name}.