`dotnet new sln` is not using templates from the right version

[333fred]

Describe the bug

I have the following SDKs installed:

8.0.120 [/home/fred/.local/share/dnvm/dn/sdk]
8.0.414 [/home/fred/.local/share/dnvm/dn/sdk]
9.0.306 [/home/fred/.local/share/dnvm/dn/sdk]
10.0.100 [/home/fred/.local/share/dnvm/dn/sdk]

When running dotnet new sln, logs indicate that the templates being used are from the 9.0.306 SDK, not the 10.0.100 SDK.

To Reproduce

1. Install both 9.0.xxx and 10.0.xxx versions of the SDK.
2. Run dotnet new sln -v diag

Expected: dirname.slnx is created.
Actual: dirname.sln is created.

The diag output is below.

Further technical details

details of dotnet --info

[I]at 15:20:29 in /tmp/test via .NET 10.0.100
➜ dotnet --info
.NET SDK:
 Version:           10.0.100
 Commit:            b0f34d51fc
 Workload version:  10.0.100-manifests.4c0ca8ba
 MSBuild version:   18.0.2+b0f34d51f

Runtime Environment:
 OS Name:     ubuntu
 OS Version:  24.04
 OS Platform: Linux
 RID:         linux-x64
 Base Path:   /home/fred/.local/share/dnvm/dn/sdk/10.0.100/

.NET workloads installed:
There are no installed workloads to display.
Configured to use workload sets when installing new manifests.
No workload sets are installed. Run "dotnet workload restore" to install a workload set.

Host:
  Version:      10.0.0
  Architecture: x64
  Commit:       b0f34d51fc

.NET SDKs installed:
  8.0.120 [/home/fred/.local/share/dnvm/dn/sdk]
  8.0.414 [/home/fred/.local/share/dnvm/dn/sdk]
  9.0.306 [/home/fred/.local/share/dnvm/dn/sdk]
  10.0.100 [/home/fred/.local/share/dnvm/dn/sdk]

.NET runtimes installed:
  Microsoft.AspNetCore.App 8.0.20 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 9.0.10 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.AspNetCore.App]
  Microsoft.AspNetCore.App 10.0.0 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 8.0.20 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 9.0.10 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.NETCore.App]
  Microsoft.NETCore.App 10.0.0 [/home/fred/.local/share/dnvm/dn/shared/Microsoft.NETCore.App]

Other architectures found:
  None

Environment variables:
  DOTNET_ROOT                              [/home/fred/.local/share/dnvm/dn]

global.json file:
  /tmp/test/global.json

Learn more:
  https://aka.ms/dotnet/info

Download .NET:
  https://aka.ms/dotnet/download

[I]at 15:20:33 in /tmp/test via .NET 10.0.100
➜ dotnet new sln -v diag
[2025-11-11 15:20:42.350] [Debug] [Template Engine] => [Execute]: Execute started
[2025-11-11 15:20:42.412] [Debug] [Microsoft.TemplateEngine.Edge.TemplateConstraintManager] => [Execute]: Found 5 constraints factories, initializing.
[2025-11-11 15:20:42.412] [Debug] [Microsoft.TemplateEngine.Edge.TemplateConstraintManager] => [Execute]: Found 5 constraints factories, initializing.
[2025-11-11 15:20:42.413] [Debug] [MSBuildEvaluator] => [Execute]: Output directory is: /tmp/test.
[2025-11-11 15:20:42.413] [Debug] [MSBuildEvaluator] => [Execute]: Project full path is: <null>.
[2025-11-11 15:20:42.414] [Debug] [MSBuildEvaluator] => [Execute]: Found project files: .
[2025-11-11 15:20:42.414] [Debug] [MSBuildEvaluator] => [Execute]: No project found.
[2025-11-11 15:20:42.422] [Debug] [Template Engine] => [Execute] => [Template from config /home/fred/.local/share/dnvm/dn/templates/9.0.10/microsoft.dotnet.common.itemtemplates.9.0.306.nupkg/content/Solution/.template.config/template.json]: Template from config /home/fred/.local/share/dnvm/dn/templates/9.0.10/microsoft.dotnet.common.itemtemplates.9.0.306.nupkg/content/Solution/.template.config/template.json started
[2025-11-11 15:20:42.436] [Debug] [Template Engine] => [Execute] => [Template from config /home/fred/.local/share/dnvm/dn/templates/9.0.10/microsoft.dotnet.common.itemtemplates.9.0.306.nupkg/content/Solution/.template.config/template.json]: Template from config /home/fred/.local/share/dnvm/dn/templates/9.0.10/microsoft.dotnet.common.itemtemplates.9.0.306.nupkg/content/Solution/.template.config/template.json finished, took 13 ms
[2025-11-11 15:20:42.436] [Debug] [Template Engine] => [Execute]: Found template 'Solution File' (Microsoft.Standard.QuickStarts.Solution)
[2025-11-11 15:20:42.436] [Debug] [Microsoft.TemplateEngine.Edge.Template.TemplateCreator] => [Execute] => [Template content generation]: Template content generation started
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}identity' was assigned to value 'test'.
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}safe_name' was assigned to value 'test'.
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}lower_safe_name' was assigned to value 'test'.
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}safe_namespace' was assigned to value 'test'.
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}lower_safe_namespace' was assigned to value 'test'.
[2025-11-11 15:20:42.456] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'Format{-VALUE-FORMS-}identity' was assigned to value 'sln'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}identity' was assigned to value 'test'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}safe_name' was assigned to value 'test'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}lower_safe_name' was assigned to value 'test'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}safe_namespace' was assigned to value 'test'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'name{-VALUE-FORMS-}lower_safe_namespace' was assigned to value 'test'.
[2025-11-11 15:20:42.466] [Debug] [Template Engine] => [Execute] => [Template content generation]: [JoinMacro]: Variable 'Format{-VALUE-FORMS-}identity' was assigned to value 'sln'.
[2025-11-11 15:20:42.469] [Debug] [Microsoft.TemplateEngine.Edge.Template.TemplateCreator] => [Execute] => [Template content generation]: Template content generation finished, took 32 ms
The template "Solution File" was created successfully.

[2025-11-11 15:20:42.470] [Debug] [Template Engine] => [Execute]: Execute finished, took 121 ms

[baronfel]

We checked that the default was correct in the templates (it was) and that the precedence value of the 10.x template was higher than other versions (it was). This leads me to believe that the 10.0 template didn't parse the CLI tokens and so was discarded by the template engine as a valid possibility. That would be very confusing to me if it were the case.

[Youssef1313]

@baronfel I think the issue is different.

The 10.0 sln template isn't considered at all during template cache calculation. Most likey due to:

https://github.com/dotnet/templating/blob/661031c86b8feadd89d3defdd6dc38bddda993b2/src/Microsoft.TemplateEngine.Edge/Settings/TemplateCache.cs#L57

I bet that we end up with a "sorted" output where 9 is > 10 (because 9 > 1). And because "last" wins, we prefer the 9 template.

[Youssef1313]

I don't know where the guarantee of this being sorted is, but looks like this path (which decides if the cache is up-to-date or not, I think) already relies on this basic alphabetical sorting?

[Youssef1313]

Affects dotnet new globaljson as well, as we added a new --test-runner option that's not found :)

[marcpopMSFT]

@MiYanni Please prioritize this as we'd probably want this in for the December release.

[MiYanni]

@Youssef1313 So, this line you pointed to, it does sort them alphabetical:

But the actual key order is correct:

So, I just gotta dig how we might end up with the wrong order somewhere. There is a unit test I can tweak to try to debug/figure it out. There's one below it that includes priority, but I don't think that relates to the problem here.