CLU endpoint call returns 404 and bot variable clu_result is not defined during Switch step

Question

CLU endpoint call returns 404 and bot variable clu_result is not defined during Switch step

Suma Nalluri 0

Screenshot 2025-11-19 153028.png

I am integrating a Custom Conversational Language Understanding (CLU) model with my Azure Health Bot scenario. The bot is supposed to capture the user’s query, send it to CLU, store the response in clu_result, and then route the flow using a Switch based on clu_result.result.prediction.topIntent.

However, the CLU call is consistently failing, and the bot trace shows two critical errors:

“Call for LU model failed. AxiosError: Request failed with status code 404.”

“clu_result is not defined.”

Because the CLU call fails with a 404 error, the clu_result variable is never created, so the Switch step also fails.

I have already confirmed the following settings in the Language Understanding action:

Endpoint matches the CLU resource (from Azure portal → Keys & Endpoint).

Subscription Key is correct.

Project Name is exactly “healthbot”.

Deployment Name is exactly “health_bot_deployment”.

API Version is set to 2023-04-01, which matches the CLU documentation.

Input utterance is set to the prompt variable “freeText”.

Despite these being correct, the bot still cannot reach the CLU model and continues to return a 404 response, preventing the scenario from functioning.

I need assistance identifying why the bot cannot reach the CLU endpoint and resolving the 404 + undefined variable issue so that the CLU prediction can be retrieved successfully.I am integrating a Custom Conversational Language Understanding (CLU) model with my Azure Health Bot scenario. The bot is supposed to capture the user’s query, send it to CLU, store the response in clu_result, and then route the flow using a Switch based on clu_result.result.prediction.topIntent.

However, the CLU call is consistently failing, and the bot trace shows two critical errors:

“Call for LU model failed. AxiosError: Request failed with status code 404.”

“clu_result is not defined.”

Because the CLU call fails with a 404 error, the clu_result variable is never created, so the Switch step also fails.

I have already confirmed the following settings in the Language Understanding action:

Endpoint matches the CLU resource (from Azure portal → Keys & Endpoint).

Subscription Key is correct.

Project Name is exactly “healthbot”.

Deployment Name is exactly “health_bot_deployment”.

API Version is set to 2023-04-01, which matches the CLU documentation.

Input utterance is set to the prompt variable “freeText”.

Despite these being correct, the bot still cannot reach the CLU model and continues to return a 404 response, preventing the scenario from functioning.

I need assistance identifying why the bot cannot reach the CLU endpoint and resolving the 404 + undefined variable issue so that the CLU prediction can be retrieved successfully.

Sridhar M 2,675 Reputation points Microsoft External Staff Moderator

2025-11-18T20:33:50.41+00:00
Hi Suma Nalluri

Welcome to Microsoft Q&A and Thank you for reaching out.

The error means the Language Understanding node never executed successfully, so the variable clu_result was never created. Common causes include:

Incorrect variable mapping

The output variable name in the LU node must exactly match what you reference later (case-sensitive).

If you reference clu_result.result.prediction.topIntent, ensure the LU node output is clu_result.

LU node not triggered

If the LU node is conditional or disconnected in the scenario flow, it won’t run.

Check the scenario graph to confirm the LU node is linked and reachable from the prompt step.

Failed API call to CLU endpoint

Even if the configuration looks correct, Health Bot will skip variable creation if the CLU call fails.

Causes: wrong endpoint URL, invalid key, incorrect project/deployment name, or mismatched API version.

Timeout or empty response

If CLU returns an empty or malformed response, Health Bot does not create the variable.

1. Validate CLU Node Configuration

In the LU node:

Endpoint: Should be https://<region>.api.cognitive.microsoft.com/language/:analyze-conversations?projectName=<project>&deploymentName=<deployment>&api-version=2022-10-01-preview (or latest supported version).

Subscription Key: Matches the Azure Language resource key.

Project & Deployment Names: Exactly as in Language Studio.

API Version: Use the version supported by Health Bot (check Azure Health Bot CLU integration guide).

2. Check Variable Mapping

In the LU node settings:

Output variable name must be clu_result (or whatever you reference later).

Input text should be mapped to freeText or the variable holding user input.

Add Error Handling

If clu_result exists → Switch on clu_result.result.prediction.topIntent Else → Fallback message: “Sorry, I couldn’t understand that.”

This prevents runtime crashes if CLU fails

Test CLU Endpoint Independently

curl -X POST "https://<region>.api.cognitive.microsoft.com/language/:analyze-conversations?projectName=<project>&deploymentName=<deployment>&api-version=2022-10-01-preview" \ -H "Ocp-Apim-Subscription-Key: <your-key>" \ -H "Content-Type: application/json" \ -d '{"kind":"Conversation","analysisInput":{"conversationItem":{"id":"1","text":"What is the dosage for aspirin?","modality":"text","language":"en","participantId":"1"}},"parameters":{"projectName":"<project>","deploymentName":"<deployment>","stringIndexType":"

Enable Debug Logging

In Health Bot scenario editor:

Turn on Trace and check if the LU node shows “Call for LU model failed.”

If yes, inspect the error details (often authentication or endpoint mismatch)

Reference:

https://learn.microsoft.com/en-us/azure/ai-services/language-service/conversational-language-understanding/how-to/quickstart-multi-turn-conversations?wt.mc_id=knowledgesearch_inproduct_azure-cxp-community-insider#configure-roles,-permissions,-and-settings

https://learn.microsoft.com/en-us/azure/machine-learning/how-to-debug-parallel-run-step?view=azureml-api-1

https://learn.microsoft.com/en-us/azure/machine-learning/how-to-configure-cli?view=azureml-api-2&tabs=public

I Hope this helps. Do let me know if you have any further queries.

Thank you!
Sridhar M 2,675 Reputation points Microsoft External Staff Moderator

2025-11-19T18:19:55.56+00:00

Hi Suma Nalluri

Did you get any chance to review the above response. Thank you!
Sridhar M 2,675 Reputation points Microsoft External Staff Moderator

2025-11-20T18:07:54.0366667+00:00
Hi Suma Nalluri

please follow the steps

Check the Endpoint and Region

Ensure you are using the correct Language resource endpoint. It should match the region where your CLU project is deployed.

Example:

https://<your-resource-name>.cognitiveservices.azure.com

or the regional vanity URL:

https://language.cognitive.azure.com

Mismatch between endpoint region and project deployment will cause errors.

Validate API Version

CLU runtime calls require the correct api-version in the URL:

POST /language/:analyze-conversations?api-version=<version>

Use the latest GA version from Azure documentation. An incorrect or missing version often results in 404 or 400 errors.

Confirm Authentication

Use the Language resource subscription key, not a Speech or OpenAI key. Add this header:

Ocp-Apim-Subscription-Key: <your-key>

If you see 401 Unauthorized, the key is wrong or missing. Rotate keys if needed.

Verify Project Status

Your CLU project must be:

Trained successfully (no failed runs).

Deployed to an active deployment name (e.g., prod or staging). Runtime calls fail if the project is not published or deployment name is incorrect.

5.Correct Request Body

Example JSON:

{ "kind": "Conversation", "analysisInput": { "conversationItem": { "id": "1", "text": "Bonjour, je veux annuler ma réservation", "language": "fr" } }, "parameters": { "projectName": "<your-project>", "deploymentName": "<your-deployment>", "verbose": true } }

404: Wrong path, API version, or project/deployment name.

Networking and CORS

If public access is disabled or IP restrictions apply, browser calls will fail. Use a backend proxy to keep keys secure and avoid CORS issues.

Checklist

Endpoint matches resource region.

Correct api-version.

Valid subscription key.

Project trained and deployed.

Request body schema correct.

Networking allows access.
Suma Nalluri 0 Reputation points

2025-11-20T23:23:02.9033333+00:00

Hi Sridhar M,

Thanks for the guidance. I have followed every step you listed — verified the endpoint, region, API version, subscription key, project name, deployment name, and confirmed the CLU project is trained and deployed correctly.

Even after rechecking everything, the Health Bot LU step is still returning 404, and clu_result is still not being created. I’m not sure why this is happening because all configurations appear correct on my side.

Thank you.

1 answer

Your answer

Sridhar M 2,675 Reputation points Microsoft External Staff Moderator

2025-11-19T18:19:55.56+00:00

Hi Suma Nalluri

Did you get any chance to review the above response. Thank you!
Sridhar M 2,675 Reputation points Microsoft External Staff Moderator

2025-11-20T18:07:54.0366667+00:00

Hi Suma Nalluri

please follow the steps

Check the Endpoint and Region

Ensure you are using the correct Language resource endpoint. It should match the region where your CLU project is deployed.

Example:

https://<your-resource-name>.cognitiveservices.azure.com

or the regional vanity URL:

https://language.cognitive.azure.com

Mismatch between endpoint region and project deployment will cause errors.

Validate API Version

CLU runtime calls require the correct api-version in the URL:

POST /language/:analyze-conversations?api-version=<version>

Use the latest GA version from Azure documentation. An incorrect or missing version often results in 404 or 400 errors.

Confirm Authentication

Use the Language resource subscription key, not a Speech or OpenAI key. Add this header:

Ocp-Apim-Subscription-Key: <your-key>

If you see 401 Unauthorized, the key is wrong or missing. Rotate keys if needed.

Verify Project Status

Your CLU project must be:

Trained successfully (no failed runs).

Deployed to an active deployment name (e.g., prod or staging). Runtime calls fail if the project is not published or deployment name is incorrect.

5.Correct Request Body

Example JSON:

{ "kind": "Conversation", "analysisInput": { "conversationItem": { "id": "1", "text": "Bonjour, je veux annuler ma réservation", "language": "fr" } }, "parameters": { "projectName": "<your-project>", "deploymentName": "<your-deployment>", "verbose": true } }

404: Wrong path, API version, or project/deployment name.

Networking and CORS

If public access is disabled or IP restrictions apply, browser calls will fail. Use a backend proxy to keep keys secure and avoid CORS issues.

Checklist

Endpoint matches resource region.

Correct api-version.

Valid subscription key.

Project trained and deployed.

Request body schema correct.

Networking allows access.
Suma Nalluri 0 Reputation points

2025-11-20T23:23:02.9033333+00:00

Hi Sridhar M,

Thanks for the guidance. I have followed every step you listed — verified the endpoint, region, API version, subscription key, project name, deployment name, and confirmed the CLU project is trained and deployed correctly.

Even after rechecking everything, the Health Bot LU step is still returning 404, and clu_result is still not being created. I’m not sure why this is happening because all configurations appear correct on my side.

Thank you.

Answer 1

Hi, I’m still facing the same 404 error, and I also wanted to mention another issue I’m running into: the bot shows clu_result is not defined even though the CLU call and variables are configured.

Here’s everything I’ve tried so far:

I verified all my CLU configuration settings inside the bot.

I changed the CLU endpoint URL multiple times and tested different URL formats.

I even used the exact Prediction URL from Language Studio, but it still returns a 404 every time.

I double-checked the project name, deployment name, region, and both keys.

I deleted and re-added the variables to make sure there were no typos.

Even after all of that, the bot continues to show the same 404 error, and the expression clu_result is not defined also appears, even though it is already referenced in the CLU action step.

I’m not sure what else I can try at this point. Since I’ve tested multiple endpoints, confirmed the configuration, and revalidated all variables, it seems like something else is causing both the 404 and the variable definition issue.

Could you please let me know if there are any additional troubleshooting steps, hidden configuration requirements, or known backend issues that could cause this behavior? Any guidance would be greatly appreciated.

Thank you.

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CLU endpoint call returns 404 and bot variable clu_result is not defined during Switch step

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