[mq] [skip ddci] working branch - merge d3aa838 on top of master at 7b903a5

{"baseBranch":"master","baseCommit":"7b903a53644abc39f55b2fb21283546ae9801f35","createdAt":"2026-09-21T07:23:33.429202Z","headSha":"d3aa838407b30d29431bd51066b5927b893c6562","id":"566a9b8c-b170-46b9-81b0-d8f742c50826","priority":"200","pullRequestNumber":"12545","queuedAt":"2026-09-21T07:23:33.427783Z","retryAttempt":"1","status":"STATUS_QUEUED"}

Author: gh-worker-dd-mergequeue-cf854d[bot]

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/agent/DebuggerTransformer.java

@@ -1,6 +1,7 @@
 package com.datadog.debugger.agent;
 
 import static com.datadog.debugger.instrumentation.ASMHelper.getLineNumbers;
+import static com.datadog.debugger.util.DebuggerInternalPackages.isDebuggerInternalClass;
 import static java.util.Collections.singletonList;
 import static java.util.stream.Collectors.toList;
 
@@ -99,18 +100,6 @@ public class DebuggerTransformer implements ClassFileTransformer {
   private static final boolean JAVA_AT_LEAST_17_0_20 =
       JavaVirtualMachine.isJavaVersionAtLeast(17, 0, 20);
   public static Path DUMP_PATH = Paths.get(SystemProperties.get(JAVA_IO_TMPDIR), "debugger");
-  private static final String[] SKIPPED_PACKAGES =
-      new String[] {
-        "com/datadog/debugger/agent/",
-        "com/datadog/debugger/codeorigin/",
-        "com/datadog/debugger/exception/",
-        "com/datadog/debugger/instrumentation/",
-        "com/datadog/debugger/probe/",
-        "com/datadog/debugger/sink/",
-        "com/datadog/debugger/symbol/",
-        "com/datadog/debugger/uploader/",
-        "com/datadog/debugger/util/"
-      };
 
   private final Config config;
   private final TransformerDefinitionMatcher definitionMatcher;
@@ -389,17 +378,10 @@ private boolean skipInstrumentation(String classFilePath) {
       // in case of anonymous classes
       return true;
     }
-    if (classFilePath.startsWith("com/datadog/debugger/")) {
-      // skip classes/packages that are part of debugger agent to avoid
-      // LinkageError: attempted duplicate class definition
-      // while retransforming a class used by instrumentation
-      for (int i = 0; i < SKIPPED_PACKAGES.length; i++) {
-        if (classFilePath.startsWith(SKIPPED_PACKAGES[i])) {
-          return true;
-        }
-      }
-    }
-    return false;
+    // skip classes/packages that are part of debugger agent to avoid
+    // LinkageError: attempted duplicate class definition
+    // while retransforming a class used by instrumentation
+    return isDebuggerInternalClass(classFilePath);
   }
 
   private byte[] transformTheWorld(

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/symbol/SymbolExtractionTransformer.java

@@ -1,5 +1,7 @@
 package com.datadog.debugger.symbol;
 
+import static com.datadog.debugger.util.DebuggerInternalPackages.isDebuggerInternalClass;
+
 import datadog.trace.bootstrap.debugger.DebuggerContext.ClassNameFilter;
 import datadog.trace.util.Strings;
 import java.lang.instrument.ClassFileTransformer;
@@ -31,8 +33,8 @@ public byte[] transform(
       return null;
     }
     try {
-      if (className.startsWith("com/datadog/debugger/symbol/")) {
-        // Don't parse our own classes to avoid duplicate class definition
+      if (isDebuggerInternalClass(className)) {
+        // Don't parse debugger-internal classes to avoid duplicate class definition
         return null;
       }
       if (classNameFiltering.isExcluded(Strings.getClassName(className))) {

dd-java-agent/agent-debugger/src/main/java/com/datadog/debugger/util/DebuggerInternalPackages.java

@@ -0,0 +1,33 @@
+package com.datadog.debugger.util;
+
+/** Identifies class files belonging to the debugger's own internal packages. */
+public class DebuggerInternalPackages {
+  private static final String[] SKIPPED_PACKAGES = {
+    "com/datadog/debugger/agent/",
+    "com/datadog/debugger/codeorigin/",
+    "com/datadog/debugger/exception/",
+    "com/datadog/debugger/instrumentation/",
+    "com/datadog/debugger/probe/",
+    "com/datadog/debugger/sink/",
+    "com/datadog/debugger/symbol/",
+    "com/datadog/debugger/uploader/",
+    "com/datadog/debugger/util/"
+  };
+
+  /**
+   * @param classFilePath slash-separated class file path (e.g. "com/datadog/debugger/agent/Foo")
+   * @return true if the class belongs to a debugger-internal package that must never be
+   *     re-transformed/parsed, to avoid a re-entrant LinkageError while it is being loaded.
+   */
+  public static boolean isDebuggerInternalClass(String classFilePath) {
+    if (classFilePath == null || !classFilePath.startsWith("com/datadog/debugger/")) {
+      return false;
+    }
+    for (String pkg : SKIPPED_PACKAGES) {
+      if (classFilePath.startsWith(pkg)) {
+        return true;
+      }
+    }
+    return false;
+  }
+}

dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/symbol/SymbolExtractionTransformerTest.java

@@ -8,6 +8,8 @@
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.when;
 import static utils.InstrumentationTestHelper.compileAndLoadClass;
 
@@ -19,6 +21,7 @@
 import java.io.File;
 import java.io.IOException;
 import java.lang.instrument.ClassFileTransformer;
+import java.lang.instrument.IllegalClassFormatException;
 import java.lang.instrument.Instrumentation;
 import java.net.URISyntaxException;
 import java.net.URL;
@@ -1077,6 +1080,22 @@ public void filterOutClassesFromExcludedPackages() throws IOException, URISyntax
             .anyMatch(scope -> scope.getName().equals(CLASS_NAME)));
   }
 
+  @Test
+  public void skipDebuggerInternalClasses() throws IllegalClassFormatException {
+    // Regression test for: DatadogClassLoader attempted duplicate class definition for
+    // com.datadog.debugger.instrumentation.Types (LinkageError). SymbolExtractionTransformer
+    // must never parse debugger-internal classes, since doing so while such a class is still
+    // being loaded/defined can trigger a re-entrant load of the same class on the same thread.
+    ClassNameFiltering classNameFiltering = new ClassNameFiltering(Collections.emptySet());
+    SymbolAggregator symbolAggregator = mock(SymbolAggregator.class);
+    currentTransformer = new SymbolExtractionTransformer(symbolAggregator, classNameFiltering);
+    byte[] classfileBuffer = new byte[0];
+    assertNull(
+        currentTransformer.transform(
+            null, "com/datadog/debugger/instrumentation/Types", null, null, classfileBuffer));
+    verifyNoInteractions(symbolAggregator);
+  }
+
   @Test
   @DisabledIf(
       value = "datadog.environment.JavaVirtualMachine#isJ9",

dd-java-agent/agent-debugger/src/test/java/com/datadog/debugger/util/DebuggerInternalPackagesTest.java

@@ -0,0 +1,39 @@
+package com.datadog.debugger.util;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class DebuggerInternalPackagesTest {
+
+  @Test
+  public void nullIsNotDebuggerInternal() {
+    assertFalse(DebuggerInternalPackages.isDebuggerInternalClass(null));
+  }
+
+  @Test
+  public void applicationClassIsNotDebuggerInternal() {
+    assertFalse(DebuggerInternalPackages.isDebuggerInternalClass("com/example/app/MyClass"));
+  }
+
+  @Test
+  public void debuggerInstrumentationPackageIsInternal() {
+    assertTrue(
+        DebuggerInternalPackages.isDebuggerInternalClass(
+            "com/datadog/debugger/instrumentation/Types"));
+  }
+
+  @Test
+  public void debuggerSymbolPackageIsInternal() {
+    assertTrue(
+        DebuggerInternalPackages.isDebuggerInternalClass(
+            "com/datadog/debugger/symbol/SymbolAggregator"));
+  }
+
+  @Test
+  public void debuggerPackageOutsideSkippedListIsNotInternal() {
+    assertFalse(
+        DebuggerInternalPackages.isDebuggerInternalClass("com/datadog/debugger/el/Something"));
+  }
+}