diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index b20dc35..891b621 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -27,4 +27,12 @@ jobs:
         run: dotnet build .\AudioQualityEnhancer.slnx -c Release
 
       - name: Test
-        run: dotnet test .\AudioQualityEnhancer.slnx -c Release --no-build
+        run: dotnet test .\AudioQualityEnhancer.slnx -c Release --no-build --collect:"XPlat Code Coverage" --results-directory TestResults
+
+      - name: Upload coverage
+        if: always()
+        uses: actions/upload-artifact@v6
+        with:
+          name: coverage
+          path: TestResults\**\coverage.cobertura.xml
+          if-no-files-found: error
diff --git a/AudioQualityEnhancer.Tests/AudioQualityEnhancer.Tests.csproj b/AudioQualityEnhancer.Tests/AudioQualityEnhancer.Tests.csproj
index 8b931f9..916e5df 100644
--- a/AudioQualityEnhancer.Tests/AudioQualityEnhancer.Tests.csproj
+++ b/AudioQualityEnhancer.Tests/AudioQualityEnhancer.Tests.csproj
@@ -1,9 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
+  <!-- Shared settings live in Directory.Build.props. -->
   <PropertyGroup>
-    <TargetFramework>net10.0-windows</TargetFramework>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
     <IsPackable>false</IsPackable>
   </PropertyGroup>
 
diff --git a/AudioQualityEnhancer.csproj b/AudioQualityEnhancer.csproj
index b280f31..2224e11 100644
--- a/AudioQualityEnhancer.csproj
+++ b/AudioQualityEnhancer.csproj
@@ -1,12 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
 
+  <!-- Shared settings live in Directory.Build.props. -->
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
-    <TargetFramework>net10.0-windows</TargetFramework>
-    <Nullable>enable</Nullable>
-    <ImplicitUsings>enable</ImplicitUsings>
-    <AnalysisLevel>latest</AnalysisLevel>
-    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <UseWPF>true</UseWPF>
     <UseWindowsForms>true</UseWindowsForms>
@@ -14,10 +10,6 @@
     <Version>0.17.0</Version>
   </PropertyGroup>
 
-  <PropertyGroup Condition="'$(Configuration)' == 'Release'">
-    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
-  </PropertyGroup>
-
   <ItemGroup>
     <Compile Remove="AudioQualityEnhancer.Tests\**\*" />
     <Compile Remove="Temp\**\*" />
diff --git a/Directory.Build.props b/Directory.Build.props
new file mode 100644
index 0000000..bdabe66
--- /dev/null
+++ b/Directory.Build.props
@@ -0,0 +1,25 @@
+<Project>
+
+  <PropertyGroup>
+    <TargetFramework>net10.0-windows</TargetFramework>
+    <Nullable>enable</Nullable>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <AnalysisLevel>latest</AnalysisLevel>
+    <EnforceCodeStyleInBuild>true</EnforceCodeStyleInBuild>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <!--
+      Warnings are errors in every configuration, not only in Release. The build used to
+      accept them locally and reject them in CI, so a warning was found after the push
+      instead of before it. Both projects are warning free, so this costs nothing today.
+
+      AnalysisMode is deliberately left at its default. Raising it to Recommended surfaces
+      about 300 analyzer warnings and All about 1100, mostly CA1305, CA1822, CA2007 and
+      CA1515. That is a cleanup of its own and must not be smuggled in through a build
+      file, where it would simply block every later change.
+    -->
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+
+</Project>
diff --git a/global.json b/global.json
new file mode 100644
index 0000000..512142d
--- /dev/null
+++ b/global.json
@@ -0,0 +1,6 @@
+{
+  "sdk": {
+    "version": "10.0.100",
+    "rollForward": "latestFeature"
+  }
+}