fix(api): Differentiate between setup and processing errors

[RasheedAli-Shaik]

Improved error handling in the /api/input_task endpoint by distinguishing between failures during service initialization and errors that occur during task processing.

Previously, any exception was caught and returned as a 400 Bad Request. This was misleading, as a failure to initialize the kernel or agents is a server-side issue (5xx), not a client-side one (4xx).

The logic is now wrapped in separate try...except blocks. Failures during the setup phase will correctly return a 500 Internal Server Error, providing a more accurate and actionable error response for both the client and for system monitoring.

Purpose

• Solves Bug: Fixes a bug where server-side initialization failures in the /api/input_task endpoint were incorrectly reported to the client as a 400 Bad Request.
• Improves Correctness: Aligns the API with HTTP standards by returning a 500 Internal Server Error for server-side exceptions, providing clearer and more accurate error feedback.
• Enhances Debugging: Makes the system easier to debug for both client-side developers and operators by clearly distinguishing between a faulty client request (4xx) and a server failure (5xx).
• Increases Robustness: Adds a finally block to ensure external client connections are closed, preventing potential resource leaks during an error state.

Does this introduce a breaking change?

• Yes
• No

Note: This is marked as a breaking change because the HTTP status code for a specific failure scenario (service initialization failure) has changed from 400 to 500. This is a corrective change that improves the API's contract, but clients may need to adjust if they were improperly handling this server-side error as a client-side one.

PR Title Recommendation: fix!: api: Differentiate between setup and processing errors

How to Test

*  Get the code

git clone https://github.com/microsoft/Multi-Agent-Custom-Automation-Engine-Solution-Accelerator.git
cd Multi-Agent-Custom-Automation-Engine-Solution-Accelerator
git checkout <branch-name>

• Set up the backend environment as per the project's documentation (e.g., pip install -r requirements.txt).

• Test the code

  1. Test the success case:

     • Run the backend server with valid environment variable configurations.
     • Send a valid POST request to the /api/input_task endpoint.
     • Expected: Receive a 200 OK response with the plan details.

  2. Test the server-error case:

     • Stop the server.
     • Temporarily invalidate a required environment variable for service initialization (e.g., set AZURE_SEARCH_ENDPOINT to an invalid URL).
     • Restart the server.
     • Send the same valid POST request to /api/input_task.
     • Expected: Receive an HTTP 500 Internal Server Error with the detail: "Could not initialize services for your request.". This confirms the fix.

What to Check

Verify that the following are valid

• A standard, successful request to /api/input_task functions correctly and returns a 200 status.
• When a service initialization fails due to a bad configuration, the endpoint correctly returns a 500 status code, not 400.
• The error message for the 500 error is clear and does not expose internal implementation details.
• Errors that occur later in the process (e.g., a malformed plan or a rate-limiting error) still result in the appropriate 4xx status code.

Other Information

This change is a foundational fix for API stability and correctness. It ensures the service behaves predictably and follows established web standards for error reporting.

[RasheedAli-Shaik]

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