Fix: Return 400 for template validation errors instead of 500 - #18
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Template rendering errors (e.g., 'Unexpected message role', malformed chat history) are client validation errors and should return HTTP 400 Bad Request, not 500 Internal Server Error. Previously, these errors were propagated as generic anyhow::Error, which ErrorMessage::from_anyhow() mapped to 500. This fix explicitly converts template errors to DynamoError::InvalidArgument, which the HTTP layer correctly maps to 400. Fixes incorrect status codes for errors like: - 'Unexpected message role' (in tool_use context) - Invalid chat message structure - Template parameter validation failures Before: HTTP 500 'Internal server error: Failed to generate completions...' After: HTTP 400 'Failed to apply prompt template: ...'
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Pull request overview
This PR adjusts the LLM request preprocessing path so prompt-template rendering/validation failures are surfaced as DynamoError with ErrorType::InvalidArgument, allowing the OpenAI HTTP layer to correctly return HTTP 400 (Bad Request) instead of HTTP 500 (Internal Server Error) for client-caused template issues.
Changes:
- Convert
apply_template()failures intoErrorType::InvalidArgumentat the preprocessing call site to drive 400 responses. - Update the returned error message to include template-application context for client-facing errors.
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| let _nvtx = dynamo_nvtx_range!("preprocess.template"); | ||
| self.apply_template(request) | ||
| .with_context(|| "Failed to apply prompt template")? | ||
| .map_err(|e| { |
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com> Signed-off-by: dengkliu92 <dengke.liu@datadoghq.com>
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Template rendering errors (e.g., 'Unexpected message role', malformed chat history) are client validation errors and should return HTTP 400 Bad Request, not 500 Internal Server Error.
Previously, these errors were propagated as generic anyhow::Error, which ErrorMessage::from_anyhow() mapped to 500. This fix explicitly converts template errors to DynamoError::InvalidArgument, which the HTTP layer correctly maps to 400.
Fixes incorrect status codes for errors like:
Before: HTTP 500 'Internal server error: Failed to generate completions...'
After: HTTP 400 'Failed to apply prompt template: ...'