UnsupportedOperationException at startup when using JDK 26+

co.elastic.apm.agent.bci.IndyBootstrap#loadClassInBootstrap から始め、Byte Buddy の ClassInjector をどのように呼び出しているかを調査します。その経路を、参照されている OpenTelemetry の HelperInjector 実装と比較し、その後 JDK 26 以降でエージェントの起動を再現します。報告されている UnsupportedOperationException で起動が失敗しなくなり、一時的な system-property による workaround に依存しなくなれば完了です。

Initially reported in our forum.

2026-06-25 17:22:20,878 [main] ERROR co.elastic.apm.agent.bci.ElasticApmAgent - Exception occurred while applying instrumentation co.elastic.apm.agent.java_ldap.LdapClientInstrumentation
java.lang.RuntimeException: java.lang.UnsupportedOperationException: Could not access Unsafe class: As of Java 26, using Unsafe is disabled by default, set net.bytebuddy.safe to true if you want to use the JVM's internal unsafe API even though it will become unsupported in the future and should be replaced by injection using method handles: net.bytebuddy.dynamic.loading.ClassInjector$UsingLookup
        at co.elastic.apm.agent.bci.IndyBootstrap.getIndyBootstrapMethod(IndyBootstrap.java:240) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.getTransformer(ElasticApmAgent.java:486) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.applyAdvice(ElasticApmAgent.java:444) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.initAgentBuilder(ElasticApmAgent.java:365) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.initInstrumentation(ElasticApmAgent.java:290) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.initInstrumentation(ElasticApmAgent.java:179) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.ElasticApmAgent.initialize(ElasticApmAgent.java:165) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
        at java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
        at co.elastic.apm.agent.premain.AgentMain.loadAndInitializeAgent(AgentMain.java:157) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.premain.AgentMain.init(AgentMain.java:98) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.premain.AgentMain.premain(AgentMain.java:47) [elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[?:?]
        at java.lang.reflect.Method.invoke(Method.java:565) ~[?:?]
        at sun.instrument.InstrumentationImpl.loadClassAndStartAgent(InstrumentationImpl.java:544) [?:?]
        at sun.instrument.InstrumentationImpl.loadClassAndCallPremain(InstrumentationImpl.java:556) [?:?]
Caused by: java.lang.UnsupportedOperationException: Could not access Unsafe class: As of Java 26, using Unsafe is disabled by default, set net.bytebuddy.safe to true if you want to use the JVM's internal unsafe API even though it will become unsupported in the future and should be replaced by injection using method handles: net.bytebuddy.dynamic.loading.ClassInjector$UsingLookup
        at net.bytebuddy.dynamic.loading.ClassInjector$UsingUnsafe$Dispatcher$Unavailable.initialize(ClassInjector.java:2206) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at net.bytebuddy.dynamic.loading.ClassInjector$UsingUnsafe.injectRaw(ClassInjector.java:1907) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at net.bytebuddy.dynamic.loading.ClassInjector$AbstractBase.injectRaw(ClassInjector.java:202) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.IndyBootstrap.loadClassInBootstrap(IndyBootstrap.java:310) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.IndyBootstrap.initIndyBootstrap(IndyBootstrap.java:268) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        at co.elastic.apm.agent.bci.IndyBootstrap.getIndyBootstrapMethod(IndyBootstrap.java:234) ~[elastic-apm-agent-1.56.1-SNAPSHOT.jar:1.56.1-SNAPSHOT]
        ... 15 more

I think we need to modify the call to ClassInjector inco.elastic.apm.agent.bci.IndyBootstrap#loadClassInBootstrap method to implement something close to what is being done in upstream otel in https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/31188f0f8190356f8b943c81a0c8c51e9a45e6c4/muzzle/src/main/java/io/opentelemetry/javaagent/tooling/HelperInjector.java#L391

As reference, here is the PR that mainly contributed to the current version (where Unsafe usages were being removed) : https://github.com/open-telemetry/opentelemetry-java-instrumentation/pull/14855

The temporary workaround is to set net.bytebuddy.safe = false in Java system properties by adding the -Dnet.bytebuddy.safe=false JVM command line argument.