Add instructions for viewing build-time OpenAPI logs

aspnetcore/fundamentals/openapi/aspnetcore-openapi.md

@@ -5,7 +5,7 @@ description: Learn how to generate and customize OpenAPI documents in an ASP.NET
 ms.author: safia
 monikerRange: '>= aspnetcore-6.0'
 ms.custom: mvc
-ms.date: 07/09/2025
+ms.date: 09/22/2025
 uid: fundamentals/openapi/aspnetcore-openapi
 ---
 # Generate OpenAPI documents
@@ -234,6 +234,22 @@ cat obj/{ProjectName}.json
 
 ---
 
+### View build-time OpenAPI logs (Terminal Logger)
+
+When `Microsoft.Extensions.ApiDescription.Server` runs the **:::no-loc text="GetDocument":::** step during `dotnet build`, progress messages aren't visible with the .NET Terminal Logger at default verbosity in .NET 8 or later. To surface these messages while building, use either of the following options with the `dotnet build` command.
+
+Set the Terminal Logger's verbosity with the `-tlp` option set to `v=d` (verbosity = detailed):
+
+```dotnetcli
+dotnet build -tlp:v=d
+```
+
+Disable the Terminal Logger and use legacy-style logs with the [`--tl` option](/dotnet/core/tools/dotnet-build#options) set to `off`:
+
+```dotnetcli
+dotnet build --tl:off
+```
+
 ### Customizing build-time document generation
 
 #### Modifying the output directory of the generated Open API file