fix: put otel incubator api on the bootstrap classpath

braintrust-java-agent/build.gradle

@@ -96,10 +96,9 @@ configurations {
 
   // Bootstrap libraries — unshaded, added to bootstrap classpath at runtime via
   // Instrumentation.appendToBootstrapClassLoaderSearch(). Includes:
-  //   - OTel API (Tracer, Span, Context, etc.)
-  //   - OTel SDK (SdkTracerProvider, SpanProcessor, etc.)
-  //   - OTel SDK autoconfigure (AutoConfiguredOpenTelemetrySdk)
-  //   - OTel SDK autoconfigure SPI (AutoConfigurationCustomizerProvider)
+  //   - OTel API (Tracer, Span, Context, etc.) and incubator API
+  // The API's no-op implementations must be able to load the incubator types.
+  // The SDK and autoconfigure remain isolated in BraintrustClassLoader.
   bootstrapLibs
 
   // Agent internals (ByteBuddy, OTLP exporter, OkHttp, instrumentation code)
@@ -110,8 +109,10 @@ configurations {
 dependencies {
   bootstrap project(':braintrust-java-agent:bootstrap')
 
-  // OTel API + SDK + autoconfigure on bootstrap classpath
+  // Keep both APIs visible to bootstrap-loaded OTel no-op factories. Otherwise the
+  // isolated ExtendedSdkTracer casts a non-extended no-op builder during shutdown.
   bootstrapLibs "io.opentelemetry:opentelemetry-api:${otelVersion}"
+  bootstrapLibs "io.opentelemetry:opentelemetry-api-incubator:${otelVersion}-alpha"
 
   internal project(path: ':braintrust-java-agent:internal', configuration: 'shadow')
 
@@ -151,7 +152,7 @@ jar {
     exclude 'META-INF/maven/**'
   }
 
-  // 2) Include bootstrap libraries as normal .class files (OTel API + SDK + autoconfigure)
+  // 2) Include bootstrap libraries as normal .class files (OTel API + incubator API)
   from(provider { configurations.bootstrapLibs.collect { zipTree(it) } }) {
     exclude 'META-INF/**'
   }

braintrust-java-agent/internal/build.gradle

@@ -26,11 +26,10 @@ dependencies {
   // ByteBuddy for bytecode manipulation — bundled as .classdata in BraintrustClassLoader
   implementation "net.bytebuddy:byte-buddy:${byteBuddyVersion}"
 
-  // OTel API on the bootstrap classpath at runtime so we compile against them but do NOT bundle them.
+  // Both OTel APIs are on bootstrap at runtime and excluded from the shadow JAR below.
   compileOnly "io.opentelemetry:opentelemetry-api:${otelVersion}"
+  compileOnly "io.opentelemetry:opentelemetry-api-incubator:${otelVersion}-alpha"
   // OTel SDK + autoconfigure engine — bundled into BraintrustClassLoader.
-  // These are no longer on the bootstrap classpath.
-  implementation "io.opentelemetry:opentelemetry-api-incubator:${otelVersion}-alpha"
   implementation "io.opentelemetry:opentelemetry-sdk:${otelVersion}"
   implementation "io.opentelemetry:opentelemetry-sdk-extension-autoconfigure:${otelVersion}"
   implementation "io.opentelemetry:opentelemetry-sdk-extension-autoconfigure-spi:${otelVersion}"

braintrust-java-agent/src/test/java/dev/braintrust/system/AgentBootstrapTest.java

@@ -7,6 +7,8 @@
 import io.opentelemetry.api.GlobalOpenTelemetry;
 import io.opentelemetry.api.trace.Span;
 import io.opentelemetry.api.trace.Tracer;
+import io.opentelemetry.api.trace.TracerProvider;
+import io.opentelemetry.context.Context;
 import java.io.File;
 import java.util.HashSet;
 import java.util.List;
@@ -221,6 +223,43 @@ void otelAutoconfigureProducesRealTracer() {
                 "Expected a real (recording) span, not a propagated/noop span");
     }
 
+    @Test
+    void tracerAfterShutdownPreservesParentWithoutRecording() throws Exception {
+        // Load the SDK through the actual agent loader, not the application classpath.
+        // A flat classpath hides the API/incubator visibility mismatch from issue #184.
+        var providerClass =
+                BraintrustBridge.getAgentClassLoader()
+                        .loadClass("io.opentelemetry.sdk.trace.SdkTracerProvider");
+        var builder = providerClass.getMethod("builder").invoke(null);
+        var provider = (TracerProvider) builder.getClass().getMethod("build").invoke(builder);
+        var close = providerClass.getMethod("close");
+        boolean closed = false;
+        try {
+            Tracer tracer = provider.get("shutdown-regression");
+            Span parent = tracer.spanBuilder("before-shutdown").setNoParent().startSpan();
+            assertTrue(parent.isRecording());
+            var parentContext = Context.root().with(parent);
+            parent.end();
+
+            close.invoke(provider);
+            closed = true;
+
+            Span child = tracer.spanBuilder("after-shutdown").setParent(parentContext).startSpan();
+            assertFalse(child.isRecording());
+            assertEquals(parent.getSpanContext(), child.getSpanContext());
+            child.end();
+
+            Span root = tracer.spanBuilder("after-shutdown-root").setNoParent().startSpan();
+            assertFalse(root.isRecording());
+            assertFalse(root.getSpanContext().isValid());
+            root.end();
+        } finally {
+            if (!closed) {
+                close.invoke(provider);
+            }
+        }
+    }
+
     private static boolean startsWithAny(String str, List<String> prefixes) {
         for (String prefix : prefixes) {
             if (str.startsWith(prefix)) {