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

Bắt đầu với thread dump đính kèm cho PID 17937 và các log của Cursor Java và Extension Host, sau đó kiểm tra cách JDTLS được khởi chạy trên macOS với cấu hình Java 21 đã được báo cáo. Nếu có thể, hãy tái hiện trạng thái không phản hồi; công việc được xem là hoàn tất khi đã xác định được nguyên nhân và tiến trình JDTLS không còn bị treo trong các điều kiện đã báo cáo.