macOS: JDTLS java process shows “Not Responding” in Activity Monitor

Environment

• macOS version: 26.1
• Extension: Language Support for Java(TM) by Red Hat version: 1.50.0
• JDK used by JDTLS (java -version and/or ps command line): 21.0.9-macosx-aarch64
• ps -ef output

  502 17937 17590   0  6:19PM ??         7:25.31 /Users/<user>/.cursor/extensions/redhat.java-1.50.0-darwin-arm64/jre/21.0.9-macosx-aarch64/bin/java --add-modules=ALL-SYSTEM --add-opens java.base/java.util=ALL-UNNAMED --add-opens java.base/java.lang=ALL-UNNAMED --add-opens java.base/sun.nio.fs=ALL-UNNAMED -Declipse.application=org.eclipse.jdt.ls.core.id1 -Dosgi.bundles.defaultStartLevel=4 -Declipse.product=org.eclipse.jdt.ls.core.product -Djava.import.generatesMetadataFilesAtProjectRoot=false -DDetectVMInstallationsJob.disabled=true -Dfile.encoding=utf8 -XX:+UseParallelGC -XX:GCTimeRatio=4 -XX:AdaptiveSizePolicyWeight=90 -Dsun.zip.disableMemoryMapping=true -Xmx2G -Xms100m -Xlog:disable -javaagent:/Users/<user>/.cursor/extensions/redhat.java-1.50.0-darwin-arm64/lombok/lombok-1.18.39-4050.jar -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/Users/<user>/Library/Application Support/Cursor/User/workspaceStorage/b073665c2bc84ec3e79c32587934d14c/redhat.java -Daether.dependencyCollector.impl=bf -jar /Users/<user>/.cursor/extensions/redhat.java-1.50.0-darwin-arm64/server/plugins/org.eclipse.equinox.launcher_1.7.100.v20251111-0406.jar -configuration /Users/<user>/Library/Application Support/Cursor/User/globalStorage/redhat.java/1.50.0/config_mac -data /Users/<user>/Library/Application Support/Cursor/User/workspaceStorage/b073665c2bc84ec3e79c32587934d14c/redhat.java/jdt_ws --pipe=/private/var/folders/cp/bcjqx5q56h7gp_3kts42xglm0000gp/T/lsp-aa7656daf3ce78c3a57214fd2e50ecf6.sock

Repro / When it happens

• Project type: Maven/Gradle
• Steps leading to hang:
• Does it recover on its own? No

Observed

• Activity Monitor shows java (Not Responding) PID 17937 with low CPU

Attachments

• threadump of java process 17937.vscode-java-plugin.txt
• Cursor Output (Java) logs + Extension Host logs

Dec 24, 2025 6:19:17 PM org.apache.aries.spifly.BaseActivator log
INFO: Registered provider ch.qos.logback.classic.spi.LogbackServiceProvider of service org.slf4j.spi.SLF4JServiceProvider in bundle ch.qos.logback.classic
Dec 24, 2025 6:28:44 PM com.microsoft.java.debug.plugin.internal.JavaDebuggerServerPlugin start
INFO: Starting com.microsoft.java.debug.plugin
Dec 24, 2025 6:31:26 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 214
Dec 24, 2025 6:36:01 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 977
Dec 24, 2025 6:46:24 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 2084
Dec 24, 2025 6:47:47 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 2432
Dec 24, 2025 6:52:33 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 2883
Dec 24, 2025 8:28:39 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 4289
Dec 24, 2025 8:28:39 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 4286
Dec 24, 2025 8:28:39 PM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 4293
Dec 25, 2025 10:32:20 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 5863
Dec 25, 2025 10:42:54 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 6305
Dec 25, 2025 10:42:54 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 6307
Dec 25, 2025 10:42:54 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 6308
Dec 25, 2025 10:42:54 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 6309
Dec 25, 2025 10:42:54 AM org.eclipse.lsp4j.jsonrpc.RemoteEndpoint handleCancellation
WARNING: Unmatched cancel notification for request id 6310

Comienza con el volcado de hilos adjunto para el PID 17937 y los registros de Cursor Java y Extension Host; después, inspecciona cómo se inicia JDTLS en macOS con la configuración de Java 21 indicada. Reproduce el estado en el que no responde si es posible; se considera terminado cuando se haya identificado la causa y el proceso de JDTLS ya no se bloquee en las condiciones indicadas.