Language Support for Java fails to initialize: command 'sts.java.addClasspathListener' already exists

[soumichel]

Describe the bug
Language Support for Java never finishes loading in VS Code. The Java status remains in an infinite loading state, and the Java language server client reports that it could not create a connection to the server.

The following error is displayed on every startup:
Language Support for Java client: couldn't create connection to server.
Error: command 'sts.java.addClasspathListener' already exists

The issue was first observed with Java extension version 1.56.0 and persists after updating to version 1.57.2026090408.

To Reproduce

1. Start Visual Studio Code with both Language Support for Java by Red Hat and Spring Boot Tools enabled.
2. Open a Maven-based Spring Boot Java workspace.
3. Wait for Language Support for Java to initialize.
4. Observe that the Java loading status never completes.
5. Observe the notification reporting:
   Language Support for Java client: couldn't create connection to server.
   Error: command 'sts.java.addClasspathListener' already exists

I have run Java: Clean Java Language Server Workspace with restart and deletion numerous times. The workspace is recreated, but the error and infinite loading state persist.

JDT Language Server log
The following initialization and error cycle is repeated multiple times:
!ENTRY org.eclipse.jdt.ls.core 1 0 2026-09-10 02:53:14.677
!MESSAGE >> initialize
!ENTRY org.eclipse.jdt.ls.core 1 0 2026-09-10 02:53:14.678
!MESSAGE Initializing JDT Language Server (Standard)

Version: 1.62.0-SNAPSHOT (OSGi 1.62.0.202609040812)
Git Commit: 126afcd - Upversion to 1.62.0

!ENTRY org.eclipse.jdt.ls.core 1 0 2026-09-10 02:53:14.738
!MESSAGE Importers: GradleBuildServerProjectImporter, GradleProjectImporter, MavenProjectImporter, EclipseProjectImporter, InvisibleProjectImporter
!ENTRY org.eclipse.jdt.ls.core 1 0 2026-09-10 02:53:14.824
!MESSAGE Progressive import: reporting 1 new project(s)
!ENTRY org.eclipse.jdt.ls.core 1 0 2026-09-10 02:53:14.827
!MESSAGE Workspace initialized in 98ms
!ENTRY org.eclipse.jdt.ls.core 4 0 2026-09-10 02:53:16.795
!MESSAGE org.eclipse.lsp4j.jsonrpc.ResponseErrorException: Unhandled method workspace/executeClientCommand
!STACK 0
java.util.concurrent.CompletionException: org.eclipse.lsp4j.jsonrpc.ResponseErrorException: Unhandled method workspace/executeClientCommand
at java.base/java.util.concurrent.CompletableFuture.reportJoin(Unknown Source)
at java.base/java.util.concurrent.CompletableFuture.join(Unknown Source)
at org.eclipse.jdt.ls.core.internal.JavaClientConnection.executeClientCommand(JavaClientConnection.java:89)
at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer.synchronizeBundles(JDTLanguageServer.java:464)
at org.eclipse.jdt.ls.core.internal.handlers.JDTLanguageServer$2.run(JDTLanguageServer.java:324)
at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
Caused by: org.eclipse.lsp4j.jsonrpc.ResponseErrorException: Unhandled method workspace/executeClientCommand
at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.handleResponse(RemoteEndpoint.java:214)
at org.eclipse.lsp4j.jsonrpc.RemoteEndpoint.consume(RemoteEndpoint.java:198)
at org.eclipse.jdt.ls.core.internal.ParentProcessWatcher.lambda$1(ParentProcessWatcher.java:86)
at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.handleMessage(StreamMessageProducer.java:189)
at org.eclipse.lsp4j.jsonrpc.json.StreamMessageProducer.listen(StreamMessageProducer.java:97)
at org.eclipse.lsp4j.jsonrpc.json.ConcurrentMessageProcessor.run(ConcurrentMessageProcessor.java:97)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source)
at java.base/java.util.concurrent.FutureTask.run(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.base/java.lang.Thread.run(Unknown Source)

Expected behavior
Language Support for Java should connect to the Java language server successfully, register its commands only once, and finish loading the Maven project without an infinite loading state.

Environment

• Operating System: Windows 11 x64
• JDK version: Oracle JDK 25.0.4.1+1 LTS
• Visual Studio Code version: 1.137.0 (commit 645f29cc3176500b4b5762ba887cf2a7f0ffdf2c)
• Java extension version: 1.57.2026090408 (win32-x64)
• Spring Boot Tools version: 2.4.0
• Project type: Private Maven-based Spring Boot project using Spring Boot 4.0.8 and Java 25

Additional Information
The affected project is private, so I cannot attach it. I have not yet isolated a minimal reproducible project.

The JDT Language Server log also repeatedly contains the following error during initialization:
org.eclipse.lsp4j.jsonrpc.ResponseErrorException: Unhandled method workspace/executeClientCommand

The stack trace points to JDTLanguageServer.synchronizeBundles.
Spring Boot Tools is installed and enabled. The sts.java.addClasspathListener command name suggests that the failure may involve the Spring Tools integration, but this is only a hypothesis; I have not confirmed the root cause.

[wenytang-ms]

Thanks for the report. This is a duplicate of #4501 and has been fixed by #4503.

Version 1.57.2026090408 does not include the fix yet. As a workaround, set:

"java.transport": "stdio"

Then reload the VS Code window. The fix will be included in the next pre-release build.