diff --git a/Directory.Packages.props b/Directory.Packages.props
index 0bcf8caa25e8..c60ad21aa558 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -82,6 +82,7 @@
     <PackageVersion Include="Serilog.Sinks.Map" Version="2.0.0" />
     <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.12" />
     <PackageVersion Include="SixLabors.ImageSharp.Web" Version="3.2.0" />
+    <!-- When updating this version, also update templates/UmbracoExtension/Umbraco.Extension.csproj -->
     <PackageVersion Include="Swashbuckle.AspNetCore" Version="10.1.4" />
   </ItemGroup>
   <!-- Transitive pinned versions (only required because our direct dependencies have vulnerable versions of transitive dependencies) -->
diff --git a/templates/UmbracoExtension/Umbraco.Extension.csproj b/templates/UmbracoExtension/Umbraco.Extension.csproj
index 913e23ec0a9e..ae346b5db293 100644
--- a/templates/UmbracoExtension/Umbraco.Extension.csproj
+++ b/templates/UmbracoExtension/Umbraco.Extension.csproj
@@ -33,6 +33,19 @@
   <ItemGroup>
     <PackageReference Include="Umbraco.Cms.Api.Common" Version="UMBRACO_VERSION_FROM_TEMPLATE" />
     <PackageReference Include="Umbraco.Cms.Api.Management" Version="UMBRACO_VERSION_FROM_TEMPLATE" />
+
+    <!--
+      Swashbuckle is available transitively from the Umbraco packages above, but we take a direct
+      dependency here because extension code directly uses types from Swashbuckle (SwaggerGenOptions)
+      and Microsoft.OpenApi (OpenApiInfo). Without a direct reference, this project's Swashbuckle
+      version is determined solely by NuGet's transitive resolution, which can resolve to a different
+      version than the host site project (e.g. a newer patch). When that happens, the different
+      Microsoft.OpenApi versions (a transitive dependency of Swashbuckle) can conflict at runtime,
+      causing custom Swagger documents registered by the extension to fail to appear.
+      Most other transitive dependencies don't have this problem because extension code doesn't
+      use their types directly - only Swashbuckle/OpenApi types are referenced in the composer.
+    -->
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="10.1.4" />
     <PackageReference Include="Umbraco.Cms.Web.Common" Version="UMBRACO_VERSION_FROM_TEMPLATE" />
     <PackageReference Include="Umbraco.Cms.Web.Website" Version="UMBRACO_VERSION_FROM_TEMPLATE" />
   </ItemGroup>