[BUG] Unable to utilize streamable-http when hosted in Azure App Service via Docker Container

[jcbartle]

Describe the bug

Maybe this is a known issue, but I can't find any documentation which states this.

I'm unable to successfully host the Azure MCP Server in Azure App Service (using a container) and connect to it using streamable-http.

I'm currently using the popular LibreChat open source project to interact with this (and several other) MCP servers. All other MCP servers work; only Azure MCP Server is giving me this issue.

Each time I try to invoke the Azure MCP Server, I get this error message:

Connection failed: Streamable HTTP error: Error POSTing to endpoint: {"error":{"code":-32001,"message":"Session not found"},"id":"","jsonrpc":"2.0"}

This error does not occur if I run the container locally via Docker Desktop with all the same environment variables.

This error also does not occur if I make a standard HTTP POST request to the Azure App Service endpoint using Invoke-WebRequest in PowerShell - those requests are successful.

The only difference I see between hosting locally and hosting in Azure App Service is in the log stream output.

HOSTING LOCALLY (anonymized):

info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: ModelContextProtocol.Server.McpServer[570385771]
      Server (Azure MCP Server 2.0.0-beta.19) method 'initialize' request handler called.
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 POST http://localhost:8080/ - 200 - text/event-stream 3167.1417ms
info: ModelContextProtocol.Server.McpServer[1867955179]
      Server (Azure MCP Server 2.0.0-beta.19), Client (@librechat/api-client 1.2.3) method 'initialize' request handler completed in 12.5028ms.
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 POST http://localhost:8080/ - application/json 54
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10242: Security token: '[PII of type 'Microsoft.IdentityModel.JsonWebTokens.JsonWebToken' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]' has a valid signature.
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10239: Lifetime of the token is valid.
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10234: Audience Validated.Audience: 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10245: Creating claims identity from the validated token: '[PII of type 'Microsoft.IdentityModel.JsonWebTokens.JsonWebToken' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]'.
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 POST http://localhost:8080/ - 202 0 - 5.9406ms

HOSTING IN AZURE APP SERVICE (anonymized):

info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Http.Result.JsonResult[1]
      Setting HTTP status code 404.
info: Microsoft.AspNetCore.Http.Result.JsonResult[3]
      Writing value of type 'JsonRpcError' as Json.
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 POST http://app-mcp-server.azurewebsites.net/ - 404 - application/json;+charset=utf-8 1.2365ms
info: Microsoft.AspNetCore.Hosting.Diagnostics[1]
      Request starting HTTP/1.1 POST http://app-mcp-server.azurewebsites.net/ - application/json 170
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10242: Security token: '[PII of type 'Microsoft.IdentityModel.JsonWebTokens.JsonWebToken' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]' has a valid signature.
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10239: Lifetime of the token is valid.
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10234: Audience Validated.Audience: 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'
info: Microsoft.IdentityModel.LoggingExtensions.IdentityLoggerAdapter[0]
      IDX10245: Creating claims identity from the validated token: '[PII of type 'Microsoft.IdentityModel.JsonWebTokens.JsonWebToken' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]'.
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[0]
      Executing endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: ModelContextProtocol.Server.McpServer[570385771]
      Server (Azure MCP Server 2.0.0-beta.19) method 'initialize' request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
      Server (Azure MCP Server 2.0.0-beta.19), Client (@librechat/api-client 1.2.3) method 'initialize' request handler completed in 0.1322ms.
info: Microsoft.AspNetCore.Routing.EndpointMiddleware[1]
      Executed endpoint 'MCP Streamable HTTP | HTTP: POST /'
info: Microsoft.AspNetCore.Hosting.Diagnostics[2]
      Request finished HTTP/1.1 POST http://app-mcp-server.azurewebsites.net/ - 200 - text/event-stream 1.0742ms

You can see the 404 error in the latter output when the initial streamable HTTP POST event occurs. Not sure if this is the actual cause or not.

This isn't an auth issue (or doesn't seem to be). Here are the LibreChat logs for OAuth to the Azure App Service-hosted MCP server:

info: [MCP][User: xxxxxxxxxxxxxxxxxxxxxxxx][AzureMCPServer] Establishing new connection
info: [MCP][AzureMCPServer][xxxxxxxxxxxxxxxxxxxxxxxx] Loaded OAuth tokens
info: [MCP][User: xxxxxxxxxxxxxxxxxxxxxxxx][AzureMCPServer] Creating streamable-http transport: https://app-mcp-server.azurewebsites.net/
info: [MCP][User: xxxxxxxxxxxxxxxxxxxxxxxx][AzureMCPServer] Connection successfully established
info: [MCP OAuth] Successfully reconnected AzureMCPServer for user xxxxxxxxxxxxxxxxxxxxxxxx

Expected behavior

MCP server connects and can be queried.

Actual behavior

Connection throws this error:

Connection failed: Streamable HTTP error: Error POSTing to endpoint: {"error":{"code":-32001,"message":"Session not found"},"id":"","jsonrpc":"2.0"}

Reproduction Steps

I think documenting all the steps to set up both Azure MCP Server in Azure App Service and configuring Entra ID and configuring local LibreChat deployment is more than I can reasonably enter here. If the details under the problem description are not enough, please let me know, and I'll provide any missing details.

Environment

• Azure App Service
• Windows 11
• PowerShell 7.5.4
• Latest LibreChat repo
• Azure MCP Server container image version 2.0.0-beta.19-amd64

[saibhaskerraju]

Hello @jcbartle ,

I am also waiting for official instructions on how to host Azure MCP to App Service or Container Apps, however I found two articles that might help you

https://github.com/Azure-Samples/azmcp-foundry-aca-mi?tab=readme-ov-file
https://learn.microsoft.com/en-us/azure/developer/azure-mcp-server/how-to/deploy-remote-mcp-server-microsoft-foundry

is it possible for you to share the docker compose with env variables that you used to run locally? I am kind of stuck there.

[jcbartle]

Evening, @saibhaskerraju. Thanks for the links. I have been through those (and every other resource I've been able to find).

I don't use Docker Compose, but here is the anonymized command you can run to test locally (obviously adjust depending on which tool you want to surface):

docker run --rm -it -p 8080:8080 -e ASPNETCORE_ENVIRONMENT=Dev -e ASPNETCORE_URLS=http://+:8080 -e AZURE_MCP_DANGEROUSLY_DISABLE_HTTPS_REDIRECTION=true -e AZURE_MCP_COLLECT_TELEMETRY=false -e AzureAd__Instance=https://login.microsoftonline.com/ -e AzureAd__TenantId=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx -e AzureAd__ClientId=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx -e AZURE_TENANT_ID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx -e AZURE_CLIENT_ID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx -e AZURE_CLIENT_SECRET=secret_value mcr.microsoft.com/azure-sdk/azure-mcp:2.0.0-beta.19-amd64 --transport http --outgoing-auth-strategy UseHostingEnvironmentIdentity --mode single --read-only --tool search_knowledge_base_retrieve

[saibhaskerraju]

Thanks @jcbartle , I will try this. please reply here in case you get any info regarding this

I dont think Azure MCP is ready for SSE. @joshfree , can you please assist us here?

we both are looking to host Azure MCP either on App service or Function apps and are willing to consume it in an agent.

[jcbartle]

Hello, @anuchandy. I wanted to check on this issue. I've updated to the latest container image (2.0.0-beta.23-amd64), and I'm still seeing the same issues. Again, works just fine running locally, but I can't get the same config to work when running in Azure App Service. Hoping I'm just missing something simple.

Thanks!

[anuchandy]

Hi @jcbartle, wanted to point you to the azd templates we have here. While these deploy to ACA rather than App Service, they show how to set up the supported Entra auth configuration and the various environment variables needed