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Document DOTNET_Thread_DefaultStackSize environment variable and runtimeconfig.json property for .NET 10 #49657

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Document DOTNET_Thread_DefaultStackSize environment variable and runtimeconfig.json property for .NET 10 #49657

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57fe00b
Document DOTNET_Thread_DefaultStackSize environment variable
agocke Nov 7, 2025
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Initial plan
Copilot Nov 7, 2025
6379675
Fix markdown linting issues in threading.md
Copilot Nov 7, 2025
25a138b
Remove placeholder ellipses from threading.md
Copilot Nov 7, 2025
db3f8b3
Add DOTNET_Thread_DefaultStackSize section to existing content
Copilot Nov 7, 2025
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Improve examples with platform-specific commands
Copilot Nov 7, 2025
e6af8ed
Match section format with other threading config sections
Copilot Nov 7, 2025
a888838
Clarify hex format and main thread behavior
Copilot Nov 7, 2025
9ea89da
Clarify hexadecimal format wording
Copilot Nov 7, 2025
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Add runtimeconfig.json property and examples
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Update version to .NET 10
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39 changes: 39 additions & 0 deletions docs/core/runtime-config/threading.md
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title: Threading config settings
description: Learn about the settings that configure threading for .NET apps.
ms.date: 11/04/2021
ai-usage: ai-assisted
---
# Runtime configuration options for threading
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@agocke agocke Nov 7, 2025

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@copilot keep all the old content, just add the new at the bottom

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Copilot AI Nov 7, 2025

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Fixed in commit db3f8b3. Restored all original content and added the new DOTNET_Thread_DefaultStackSize section at the bottom.


Expand Down Expand Up @@ -265,3 +266,41 @@ Project file:

</Project>
```

## Default stack size for new threads

- Configures the default stack size for threads created by <xref:System.Threading.Thread> and other APIs that don't specify an explicit stack size. The value is specified as a hexadecimal number representing bytes. This setting doesn't affect the main application thread.
- If not specified, the default stack size is determined by the operating system.

| | Setting name | Values | Version introduced |
| - | - | - | - |
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@agocke agocke Nov 7, 2025

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@copilot This is only available on all platforms starting in .NET 10

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Fixed in commit 4892484. Updated both the runtimeconfig.json property and environment variable to show ".NET 10" as the version introduced.

| **runtimeconfig.json** | `System.Threading.DefaultStackSize` | A hexadecimal integer value representing stack size in bytes. | .NET 10 |
| **MSBuild property** | N/A | N/A | N/A |
| **Environment variable** | `DOTNET_Thread_DefaultStackSize` | A hexadecimal integer value representing stack size in bytes. | .NET 10 |

### Examples

*runtimeconfig.json* file:

```json
{
"runtimeOptions": {
"configProperties": {
"System.Threading.DefaultStackSize": "0x100000"
}
}
}
```

*runtimeconfig.template.json* file:

```json
{
"configProperties": {
"System.Threading.DefaultStackSize": "0x100000"
}
}
```

> [!NOTE]
> This setting doesn't affect threads that explicitly specify a stack size at creation.