Azure Functions - dotnet exited with code

Question

Azure Functions - dotnet exited with code

link 0

In .NET10 isolated mode (EP1) function prints errors:

2026-01-26T07:06:34   [Error]   Starting worker process failed
2026-01-26T07:06:34   [Error]   Failed to start language worker process for runtime: dotnet-isolated. workerId:9c4cb7ac-a946-46b1-9c4d-accd80be154f
2026-01-26T07:06:34   [Information]   Reading functions metadata (Custom)
2026-01-26T07:06:34   [Information]   0 functions found (Custom)
2026-01-26T07:06:34   [Information]   0 functions loaded
2026-01-26T07:06:34   [Information]   You must install or update .NET to run this application.
2026-01-26T07:06:34   [Information]   App: /home/site/wwwroot/**.dll
2026-01-26T07:06:34   [Information]   Architecture: x64
2026-01-26T07:06:34   [Information]   Framework: 'Microsoft.NETCore.App', version '8.0.0' (x64)
2026-01-26T07:06:34   [Information]   .NET location: /usr/share/dotnet/
2026-01-26T07:06:34   [Information]   The following frameworks were found:
2026-01-26T07:06:34   [Information]     10.0.0 at [/usr/share/dotnet/shared/Microsoft.NETCore.App]
2026-01-26T07:06:34   [Information]   Learn more:
2026-01-26T07:06:34   [Error]   https://aka.ms/dotnet/app-launch-failed
2026-01-26T07:06:34   [Information]   To install missing framework, download:
2026-01-26T07:06:34   [Information]   https://aka.ms/dotnet-core-applaunch?framework=Microsoft.NETCore.App&framework_version=8.0.0&arch=x64&rid=linux-x64&os=ubuntu.24.04
2026-01-26T07:06:34   [Information]   Starting Host (HostId=***, InstanceId=50a370c7-82ef-4f76-9a59-0c84665cef60, Version=4.1045.200.2, ProcessId=27, AppDomainId=1, InDebugMode=False, InDiagnosticMode=False, FunctionsExtensionVersion=~4)
2026-01-26T07:06:34   [Information]   Loading functions metadata
2026-01-26T07:06:34   [Error]   Language Worker Process exited. Pid=68.

Function was upgraded according to recomendations

Looks like container image does not have .NET 8 installed which is required by host. source is .azurefunctions/function.deps.json (produced by dotnet publish)

"runtimeTarget": {
    "name": ".NETCoreApp,Version=v8.0",
    "signature": ""
  },

Pravallika KV 16,700 Reputation points Microsoft External Staff Moderator

2026-01-26T08:18:40.5066667+00:00
Hi link,

Thanks for reaching out to Microsoft Q&A.

The specific error messages indicate that the language worker process for the runtime is unable to start, likely because .NET 8 is not installed in the container image.

Here's a breakdown of what you can do to resolve this:

Check Docker Image: If you're using a custom Docker container, you'll need to ensure that the image includes .NET 8. You can modify your Dockerfile to install the necessary .NET SDK when building the image.

Installation Command: Follow the link provided in the error message to install .NET 8: Install .NET 8.

Framework Targeting: Make sure your function’s project file correctly targets the .NET Core App version. It seems to be targeting .NET Core 8.0, which should match what you have available in your environment.

Updating Dependencies: Update any related dependencies in your project to ensure compatibility with .NET 8.

Correct Environment Settings: Ensure your environment variables and function app settings in Azure are correctly configured to point to the right framework version.

Consult Logs: Check the logs in Application Insights if they are enabled, or else see the Azure portal logs related to your Function App for any additional errors that can give you clues on what's happening.

Hope this helps!
link 0 Reputation points

2026-01-26T09:41:11.6633333+00:00
Hi! Thanks for reply!

We don't use custom container image

Function seems to be properly is configurated at Azure side (shows proper framework, function runtime versions)

Application is fully targeted to Net10, no mention of .NET8 in code at all. Only in .azurefunctions/function.deps.json

2 answers

Your answer

Pravallika KV 16,700 Reputation points Microsoft External Staff Moderator

2026-01-26T08:18:40.5066667+00:00

Hi link,

Thanks for reaching out to Microsoft Q&A.

The specific error messages indicate that the language worker process for the runtime is unable to start, likely because .NET 8 is not installed in the container image.

Here's a breakdown of what you can do to resolve this:

Check Docker Image: If you're using a custom Docker container, you'll need to ensure that the image includes .NET 8. You can modify your Dockerfile to install the necessary .NET SDK when building the image.

Installation Command: Follow the link provided in the error message to install .NET 8: Install .NET 8.

Framework Targeting: Make sure your function’s project file correctly targets the .NET Core App version. It seems to be targeting .NET Core 8.0, which should match what you have available in your environment.

Updating Dependencies: Update any related dependencies in your project to ensure compatibility with .NET 8.

Correct Environment Settings: Ensure your environment variables and function app settings in Azure are correctly configured to point to the right framework version.

Consult Logs: Check the logs in Application Insights if they are enabled, or else see the Azure portal logs related to your Function App for any additional errors that can give you clues on what's happening.

Hope this helps!
link 0 Reputation points

2026-01-26T09:41:11.6633333+00:00

Hi! Thanks for reply!

We don't use custom container image

Function seems to be properly is configurated at Azure side (shows proper framework, function runtime versions)

Application is fully targeted to Net10, no mention of .NET8 in code at all. Only in .azurefunctions/function.deps.json

Answer 1

Hi link,

Thanks for reaching out to Microsoft Q&A.

Even though the Function App is configured for .NET 10 isolated (EP1) and the project targets net10.0, the Azure Functions runtime still requires .NET 8 at startup.

You must install or update .NET to run this application.
Framework: 'Microsoft.NETCore.App', version '8.0.0'
The frameworks found: 10.0.0

The dependency on .NET 8 comes from .azurefunctions/function.deps.json, which is generated by Azure Functions tooling, not by the application project itself.

Even with a net10.0 target, the Functions host / worker bootstrap logic still emits:

"runtimeTarget": {   "name": ".NETCoreApp,Version=v8.0" }

As a result, the worker process fails to start, and the host reports:

0 functions found Failed to start language worker process for runtime: dotnet-isolated

Azure Functions v4 host is still based on .NET 8
“.NET 10 isolated (EP1)” is preview-only and incomplete
The host does not roll forward from .NET 8 =>.NET 10
Portal runtime settings do not override the generated deps file

Resolution:

Target net8.0

Deploy normally

<TargetFramework>net8.0</TargetFramework>

Hope this helps!

If the resolution was helpful, kindly take a moment to click on and click on Yes for was this answer helpful. And, if you have any further query do let us know.

Answer 2

Seems your Function App is targetting .NET 8?

And the error is most likely because .NET 8 isn't available in your Azure Functions hosting environment.

Since you aren't using Docker, you will need to make a Self-contained deployment which is publish the app with the runtime bundled. This increases deployment size. But it makes sure runtime goes along with your app.

So something like,

- task: UseDotNet@2
  displayName: Install .NET 8.0.x
  inputs:
    packageType: 'sdk'
    version: '8.0.x'

- task: DotNetCoreCLI@2
  displayName: Publish
  inputs:
    command: 'publish'
    publishWebProjects: false
    projects: |
      $(System.DefaultWorkingDirectory)/<YourProject>.csproj
    arguments: --output $(System.DefaultWorkingDirectory)/publish_output --configuration Release --self-contained true --runtime linux-x64

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Azure Functions - dotnet exited with code

2 answers

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