diff --git a/dotnet/src/Client.cs b/dotnet/src/Client.cs
index 15b00ec79..225b893c6 100644
--- a/dotnet/src/Client.cs
+++ b/dotnet/src/Client.cs
@@ -997,11 +997,32 @@ private async Task VerifyProtocolVersionAsync(Connection connection, Cancellatio
     private static string? GetBundledCliPath(out string searchedPath)
     {
         var binaryName = OperatingSystem.IsWindows() ? "copilot.exe" : "copilot";
-        var rid = Path.GetFileName(System.Runtime.InteropServices.RuntimeInformation.RuntimeIdentifier);
+        // Always use portable RID (e.g., linux-x64) to match the build-time placement,
+        // since distro-specific RIDs (e.g., ubuntu.24.04-x64) are normalized at build time.
+        var rid = GetPortableRid()
+            ?? Path.GetFileName(System.Runtime.InteropServices.RuntimeInformation.RuntimeIdentifier);
         searchedPath = Path.Combine(AppContext.BaseDirectory, "runtimes", rid, "native", binaryName);
         return File.Exists(searchedPath) ? searchedPath : null;
     }
 
+    private static string? GetPortableRid()
+    {
+        string os;
+        if (OperatingSystem.IsWindows()) os = "win";
+        else if (OperatingSystem.IsLinux()) os = "linux";
+        else if (OperatingSystem.IsMacOS()) os = "osx";
+        else return null;
+
+        var arch = System.Runtime.InteropServices.RuntimeInformation.OSArchitecture switch
+        {
+            System.Runtime.InteropServices.Architecture.X64 => "x64",
+            System.Runtime.InteropServices.Architecture.Arm64 => "arm64",
+            _ => null,
+        };
+
+        return arch != null ? $"{os}-{arch}" : null;
+    }
+
     private static (string FileName, IEnumerable<string> Args) ResolveCliCommand(string cliPath, IEnumerable<string> args)
     {
         var isJsFile = cliPath.EndsWith(".js", StringComparison.OrdinalIgnoreCase);
diff --git a/dotnet/src/build/GitHub.Copilot.SDK.targets b/dotnet/src/build/GitHub.Copilot.SDK.targets
index 20afd8156..35b017662 100644
--- a/dotnet/src/build/GitHub.Copilot.SDK.targets
+++ b/dotnet/src/build/GitHub.Copilot.SDK.targets
@@ -3,17 +3,27 @@
   <!-- CopilotCliVersion is imported from GitHub.Copilot.SDK.props (generated at SDK build time, packaged alongside) -->
   <Import Project="$(MSBuildThisFileDirectory)GitHub.Copilot.SDK.props" Condition="'$(CopilotCliVersion)' == '' And Exists('$(MSBuildThisFileDirectory)GitHub.Copilot.SDK.props')" />
 
-  <!-- Resolve RID: use explicit RuntimeIdentifier, or infer from current machine -->
+  <!-- Resolve portable RID from explicit RuntimeIdentifier or build host -->
   <PropertyGroup>
-    <_CopilotRid Condition="'$(RuntimeIdentifier)' != ''">$(RuntimeIdentifier)</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Windows')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64'">win-x64</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Windows')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'Arm64'">win-arm64</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Linux')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64'">linux-x64</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('Linux')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'Arm64'">linux-arm64</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('OSX')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'X64'">osx-x64</_CopilotRid>
-    <_CopilotRid Condition="'$(_CopilotRid)' == '' And $([MSBuild]::IsOSPlatform('OSX')) And '$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture)' == 'Arm64'">osx-arm64</_CopilotRid>
+    <!-- Determine OS: from RID prefix if set, otherwise from build host -->
+    <_CopilotOs Condition="'$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.StartsWith('win'))">win</_CopilotOs>
+    <_CopilotOs Condition="'$(_CopilotOs)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.StartsWith('osx'))">osx</_CopilotOs>
+    <_CopilotOs Condition="'$(_CopilotOs)' == '' And '$(RuntimeIdentifier)' != ''">linux</_CopilotOs>
+
+    <!-- Determine arch: from RID suffix if set, otherwise from build host -->
+    <_CopilotArch Condition="'$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.EndsWith('-x64'))">x64</_CopilotArch>
+    <_CopilotArch Condition="'$(_CopilotArch)' == '' And '$(RuntimeIdentifier)' != '' And $(RuntimeIdentifier.EndsWith('-arm64'))">arm64</_CopilotArch>
+
+    <!-- When no RuntimeIdentifier is set, use the SDK's portable RID for the build host -->
+    <_CopilotRid Condition="'$(_CopilotOs)' != '' And '$(_CopilotArch)' != ''">$(_CopilotOs)-$(_CopilotArch)</_CopilotRid>
+    <_CopilotRid Condition="'$(_CopilotRid)' == '' And '$(RuntimeIdentifier)' == ''">$(NETCoreSdkPortableRuntimeIdentifier)</_CopilotRid>
   </PropertyGroup>
 
+  <!-- Fail if we couldn't determine a portable RID from the given RuntimeIdentifier -->
+  <Target Name="_ValidateCopilotRid" BeforeTargets="BeforeBuild" Condition="'$(RuntimeIdentifier)' != '' And '$(_CopilotRid)' == ''">
+    <Error Text="Could not determine a supported portable RID from RuntimeIdentifier '$(RuntimeIdentifier)'. Supported RIDs: win-x64, win-arm64, linux-x64, linux-arm64, osx-x64, osx-arm64." />
+  </Target>
+
   <!-- Map RID to platform name used in npm packages -->
   <PropertyGroup>
     <_CopilotPlatform Condition="'$(_CopilotRid)' == 'win-x64'">win32-x64</_CopilotPlatform>