diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 15b5e6876..a27b0612d 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,13 +57,12 @@ jobs:
         uses: actions/setup-dotnet@26b0ec14cb23fa6904739307f278c14f94c95bf1 # v5
         with:
           global-json-file: global.json
-          cache: true
-          cache-dependency-path: |
-            **/Directory.Packages.props
-            **/*.csproj
-            **/*.fsproj
-            **/packages.lock.json
-            **/nuget.config
+          # No Actions NuGet cache on the self-hosted runner: ~/.nuget/packages already persists on
+          # the runner's local disk between jobs, so the cache is redundant. Worse, any change to a
+          # dependency file (e.g. a Directory.Packages.props version bump) misses the key and forces a
+          # post-job tar+upload of the accumulated multi-GB global packages folder (~17 min at ~5 MB/s),
+          # which serializes the whole PR behind one cache-save step. Restore stays fast from local disk.
+          cache: false
 
       - name: Setup Node.js
         uses: actions/setup-node@48b55a011bda9f5d6aeb4c2d9c7362e8dae4041e # v6
diff --git a/Directory.Packages.props b/Directory.Packages.props
index f9cb6ce66..ff9e10220 100644
--- a/Directory.Packages.props
+++ b/Directory.Packages.props
@@ -74,7 +74,7 @@
          the contrib donation goes through its ~6-month review (see [[dual-target-otel-shipping]]).
          When #4424 merges these PackageReference rows swap to the upstream id — type identities
          preserved, so consumer code keeps compiling. -->
-    <PackageVersion Include="Qyl.OpenTelemetry.AutoInstrumentation" Version="3.1.0"/>
+    <PackageVersion Include="Qyl.OpenTelemetry.AutoInstrumentation" Version="3.1.2"/>
     <PackageVersion Include="Qyl.OpenTelemetry.SemanticConventions" Version="3.1.0"/>
     <PackageVersion Include="Qyl.OpenTelemetry.SemanticConventions.Incubating" Version="3.1.0"/>
     <!-- C# API contract types emitted from @ancplua/qyl-api-schema. -->
diff --git a/internal/qyl.instrumentation.generators/GeneratorPipelineHelpers.cs b/internal/qyl.instrumentation.generators/GeneratorPipelineHelpers.cs
index f2ce0c709..688f82750 100644
--- a/internal/qyl.instrumentation.generators/GeneratorPipelineHelpers.cs
+++ b/internal/qyl.instrumentation.generators/GeneratorPipelineHelpers.cs
@@ -9,10 +9,18 @@ internal static class GeneratorPipelineHelpers
     public const string QylServiceDefaultsTypeName = "Qyl.Instrumentation.QylServiceDefaults";
     public const string WebApplicationBuilderTypeName = "Microsoft.AspNetCore.Builder.WebApplicationBuilder";
     public const string WebApplicationTypeName = "Microsoft.AspNetCore.Builder.WebApplication";
+    public const string QylInterceptedAspNetCoreTypeName = "Qyl.OpenTelemetry.AutoInstrumentation.QylInterceptedAspNetCore";
 
     public static bool IsQylRuntimeReferenced(Compilation compilation, CancellationToken _) =>
         compilation.GetTypeByMetadataName(QylServiceDefaultsTypeName) is not null;
 
+    // When Qyl.OpenTelemetry.AutoInstrumentation is referenced, our Build() interceptor routes the
+    // build through its QylInterceptedAspNetCore.Build wrapper (which adds the OTel middleware) so a
+    // single interceptor owns the call site. The consumer sets the package's opt-out property so the
+    // OTel generator yields Build() to us — otherwise the two interceptors would collide (CS9153).
+    public static bool IsOtelAutoInstrumentationReferenced(Compilation compilation, CancellationToken _) =>
+        compilation.GetTypeByMetadataName(QylInterceptedAspNetCoreTypeName) is not null;
+
     public static bool IsPipelineEnabled(AnalyzerConfigOptionsProvider options, string propertyName) =>
         !options.GlobalOptions.TryGetValue($"build_property.{propertyName}", out var value)
         || !string.Equals(value, "false", StringComparison.OrdinalIgnoreCase);
diff --git a/internal/qyl.instrumentation.generators/ServiceDefaultsSourceGenerator.cs b/internal/qyl.instrumentation.generators/ServiceDefaultsSourceGenerator.cs
index b98b11e63..577eab655 100644
--- a/internal/qyl.instrumentation.generators/ServiceDefaultsSourceGenerator.cs
+++ b/internal/qyl.instrumentation.generators/ServiceDefaultsSourceGenerator.cs
@@ -46,6 +46,10 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
             .Select(GeneratorPipelineHelpers.IsQylRuntimeReferenced)
             .WithTrackingName(PipelineStage.QylRuntimeCheck);
 
+        var otelAutoInstrumentationAvailable = context.CompilationProvider
+            .Select(GeneratorPipelineHelpers.IsOtelAutoInstrumentationReferenced)
+            .WithTrackingName(PipelineStage.OtelAutoInstrumentationCheck);
+
         var builderCallSites = context.SyntaxProvider
             .CreateSyntaxProvider(CouldBeBuildInvocation, ExtractBuilderCallSite)
             .WhereNotNull()
@@ -53,7 +57,9 @@ public void Initialize(IncrementalGeneratorInitializationContext context)
 
         var builderInput = builderCallSites.CollectAsEquatableArray()
             .Combine(runtimeAvailable)
-            .Select(static (input, _) => new BuilderInterceptorInput(input.Left, input.Right));
+            .Combine(otelAutoInstrumentationAvailable)
+            .Select(static (input, _) =>
+                new BuilderInterceptorInput(input.Left.Left, input.Left.Right, input.Right));
 
         context.RegisterSourceOutput(builderInput, EmitBuilderInterceptors);
     }
@@ -96,11 +102,15 @@ private static void EmitBuilderInterceptors(SourceProductionContext context, Bui
         if (!input.QylRuntimeAvailable)
             return;
 
-        var source = GenerateBuilderInterceptorSource(input.CallSites.AsImmutableArray());
+        var source = GenerateBuilderInterceptorSource(
+            input.CallSites.AsImmutableArray(),
+            input.OtelAutoInstrumentationAvailable);
         context.AddSource(BuilderInterceptorsFile, SourceText.From(source, Encoding.UTF8));
     }
 
-    private static string GenerateBuilderInterceptorSource(ImmutableArray<BuilderCallSite> callSites)
+    private static string GenerateBuilderInterceptorSource(
+        ImmutableArray<BuilderCallSite> callSites,
+        bool otelAutoInstrumentationAvailable)
     {
         var sb = new StringBuilder();
 
@@ -114,7 +124,7 @@ private static string GenerateBuilderInterceptorSource(ImmutableArray<BuilderCal
         foreach (var callSite in callSites.OrderBy(static c => c.SortKey, StringComparer.Ordinal))
         {
             if (callSite.Kind is BuilderCallKind.Build)
-                AppendBuildInterceptorMethod(sb, callSite, index);
+                AppendBuildInterceptorMethod(sb, callSite, index, otelAutoInstrumentationAvailable);
             index++;
         }
 
@@ -122,11 +132,23 @@ private static string GenerateBuilderInterceptorSource(ImmutableArray<BuilderCal
         return sb.ToString();
     }
 
-    private static void AppendBuildInterceptorMethod(StringBuilder sb, BuilderCallSite callSite, int index)
+    private static void AppendBuildInterceptorMethod(
+        StringBuilder sb,
+        BuilderCallSite callSite,
+        int index,
+        bool otelAutoInstrumentationAvailable)
     {
         var displayLocation = callSite.Location.GetDisplayLocation();
         var interceptAttribute = callSite.Location.GetInterceptsLocationAttributeSyntax();
 
+        // When Qyl.OpenTelemetry.AutoInstrumentation is referenced, route the build through its
+        // QylInterceptedAspNetCore.Build wrapper (build + OTel middleware) so this stays the single
+        // interceptor on the call site. The consumer opts the OTel generator out of Build() so the
+        // two do not collide (CS9153). Without the package, build the host directly.
+        var buildExpression = otelAutoInstrumentationAvailable
+            ? $"global::{GeneratorPipelineHelpers.QylInterceptedAspNetCoreTypeName}.Build(builder)"
+            : "builder.Build()";
+
         sb.AppendLine($$"""
                                 // Intercepted call at {{displayLocation}}
                                 {{interceptAttribute}}
@@ -137,7 +159,7 @@ private static void AppendBuildInterceptorMethod(StringBuilder sb, BuilderCallSi
                                     global::Qyl.Instrumentation.Generators.QylGeneratedRegistry.RegisterQylHostedServices(builder.Services);
                                     global::Qyl.Instrumentation.Generators.QylGeneratedRegistry.RegisterQylServices(builder.Services);
                                     global::Qyl.Instrumentation.Generators.QylGeneratedRegistry.RegisterQylHealthChecks(builder.Services);
-                                    var app = builder.Build();
+                                    var app = {{buildExpression}};
                                     app.MapQylDefaultEndpoints();
                                     return app;
                                 }
@@ -147,10 +169,12 @@ private static void AppendBuildInterceptorMethod(StringBuilder sb, BuilderCallSi
     private static class PipelineStage
     {
         public const string QylRuntimeCheck = nameof(QylRuntimeCheck);
+        public const string OtelAutoInstrumentationCheck = nameof(OtelAutoInstrumentationCheck);
         public const string BuilderCallSitesDiscovered = nameof(BuilderCallSitesDiscovered);
     }
 
     private readonly record struct BuilderInterceptorInput(
         EquatableArray<BuilderCallSite> CallSites,
-        bool QylRuntimeAvailable);
+        bool QylRuntimeAvailable,
+        bool OtelAutoInstrumentationAvailable);
 }
diff --git a/services/qyl.collector/qyl.collector.csproj b/services/qyl.collector/qyl.collector.csproj
index 9c7e8333c..6e3e55ddc 100644
--- a/services/qyl.collector/qyl.collector.csproj
+++ b/services/qyl.collector/qyl.collector.csproj
@@ -8,6 +8,11 @@
     <PublishTrimmed>false</PublishTrimmed>
     <IsAotCompatible>false</IsAotCompatible>
     <InterceptorsNamespaces>$(InterceptorsNamespaces);Qyl.Instrumentation.Generators</InterceptorsNamespaces>
+    <!-- qyl.collector runs two interceptor generators that both target WebApplicationBuilder.Build():
+         ServiceDefaults (DI/health/endpoints) and Qyl.OpenTelemetry.AutoInstrumentation (OTel middleware).
+         C# forbids two interceptors per call site (CS9153), so hand Build() to ServiceDefaults — which
+         composes QylInterceptedAspNetCore.Build — and opt the OTel generator out of intercepting Build(). -->
+    <QylAutoInstrumentationInterceptWebApplicationBuilderBuild>false</QylAutoInstrumentationInterceptWebApplicationBuilderBuild>
     <QylDatabase>false</QylDatabase>
   </PropertyGroup>