Failed to initialize language server - How to troubleshoot?

[bobfields]

How do I troubleshoot this? It seems to happen on a couple specific projects. Eclipse -clean, restart, copilot SSL, copilot workspace context does not make any difference. Something with the preferences seems to affect the copilot initialization. It works when I restart with a clean workspace with no preferences, but I really don't want to do that because I have extensive customizations for eclipse preferences. And I can't figure out which preferences are causing this problem. I'm on the current Eclipse and copilot plugin version, authenticating to github.com for copilot license initialization. Windows 11, Java 17 and 21. This is the only detail I have from the error logs:

!ENTRY com.microsoft.copilot.eclipse 4 0 2025-08-19 14:50:02.067
!MESSAGE [Error] Failed to start copilot language server.
!STACK 0
java.lang.IllegalStateException: Failed to start copilot language server.
	at com.microsoft.copilot.eclipse.ui.CopilotUi$1.run(CopilotUi.java:73)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

!ENTRY org.eclipse.core.jobs 4 2 2025-08-19 14:50:02.074
!MESSAGE An internal error occurred during: "Copilot initialization".
!STACK 0
java.lang.IllegalStateException: Failed to start copilot language server.
	at com.microsoft.copilot.eclipse.ui.CopilotUi$1.run(CopilotUi.java:73)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

!ENTRY com.microsoft.copilot.eclipse 1 0 2025-08-19 14:50:02.221
!MESSAGE [Info] Starting language server with binary lsp agent.

[jdneo]

Is there any more logs reported by copilot plugin for this session?

[bros-swissas]

That is from the Eclipse error log. There is also a dedicated log for "Copilot MCP".
In Eclipse go to the "Console" and there Press on the small "Computer" icon "Display Selected Console"
In that menu select "Copilot (MCP)". There you may get more details about what goes wrong. Good luck

[haubi]

Same problem here, on Linux.
Seems like a matter of timing around the execution of that com.microsoft.copilot.eclipse.ui.CopilotUi$1.run(),
or, therein, a missing explicit await or dependency on the language server startup:
When I manually, in a debugger, put a breakpoint in org.eclipse.core.internal.jobs.Worker.run(), and delay the execution of that com.microsoft.copilot.eclipse.ui.CopilotUi$1.run() compared to other jobs, so the language server really was started up first, that "Copilot initialization" seems to succeed in this instance of the Eclipse IDE.

[haubi]

And: There doesn't seem to be a Console for "Copilot (MCP)" at all.
Do I need to configure something to enable that Console?

[jdneo]

@haubi There should be some error logs in the Error Log view, could you pls check and maybe share a screenshot?

[haubi]

The message box is:

The Error Log view shows:

And the workspace .metadata/.log file contains:

!SESSION 2025-09-15 08:42:17.878 -----------------------------------------------
eclipse.buildId=4.35.0.I20250228-0140
java.version=21.0.7
java.vendor=Eclipse Adoptium
BootLoader constants: OS=linux, ARCH=x86_64, WS=gtk, NL=en
Command-line arguments:  -os linux -ws gtk -arch x86_64

!ENTRY com.microsoft.copilot.eclipse 4 0 2025-09-15 08:42:29.258
!MESSAGE [Error] Failed to start copilot language server.
!STACK 0
java.lang.IllegalStateException: Failed to start copilot language server.
        at com.microsoft.copilot.eclipse.ui.CopilotUi$1.run(CopilotUi.java:78)
        at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

!ENTRY org.eclipse.core.jobs 4 2 2025-09-15 08:42:29.265
!MESSAGE An internal error occurred during: "Copilot initialization".
!STACK 0
java.lang.IllegalStateException: Failed to start copilot language server.
        at com.microsoft.copilot.eclipse.ui.CopilotUi$1.run(CopilotUi.java:78)
        at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)

!ENTRY com.microsoft.copilot.eclipse 1 0 2025-09-15 08:42:29.273
!MESSAGE [Info] Starting language server with binary lsp agent.

!ENTRY com.microsoft.copilot.eclipse 1 0 2025-09-15 08:42:29.274
!MESSAGE [Info] Found native binary in fragment bundle: com.microsoft.copilot.eclipse.core.agent.linux.x64

!ENTRY com.microsoft.copilot.eclipse 1 0 2025-09-15 08:42:29.280
!MESSAGE [Info] Lsp agent started successfully.

!ENTRY org.eclipse.lsp4e 1 0 2025-09-15 08:42:30.941
!MESSAGE [Info] [lsp] GitHub Copilot Language Server 1.363.0 initialized

!ENTRY org.eclipse.ui 2 2 2025-09-15 08:44:05.048
!MESSAGE Invalid preference category path: org.eclipse.ease.preferences.global (bundle: org.eclipse.ease.lang.python.jython, page: org.eclipse.ease.lang.python.jython.libraryPrefPage)

!ENTRY org.eclipse.ui 2 2 2025-09-15 08:44:05.048
!MESSAGE Invalid preference category path: org.eclipse.wst.html.ui.preferences.web (bundle: org.eclipse.wst.jsdt.ui, page: org.eclipse.wst.jsdt.ui.preferences.JavaBasePreferencePage)

[haubi]

Meanwhile I've found https://github.com/orgs/community/discussions/151288#discussioncomment-14287359
which describes what I can reproduce on Linux:

• During initial workspace setup, the Chat view is not initialized yet, and the Language Server is started later on.
• Restarting Eclipse does not show the problem again, because Chat view is already registered for early loading, but
• closing the Chat view brings back the problem after Eclipse restart.

[jdneo]

Hi @haubi, thank you for reporting this.

I tried several times to reproduce the issue and do have success for one time.

I guess it's related with the race condition between the activation of core and ui plugin. (Though the ui will wait for the job from core completed, but it is not enough if the wait logic is called before core gets activates.)

I will work on a fix and release it to the nightly build channel once it's merged. Would it be possible for you help verify the fix once it's available? Thanks!

[jdneo]

@iloveeclipse Have you ever encountered this problem before?

I'm planing to add

// Explicitly activate the core bundle first
Bundle coreBundle = Platform.getBundle(CopilotCore.PLUGIN_ID);
if (coreBundle != null && coreBundle.getState() != Bundle.ACTIVE
        && coreBundle.getState() != Bundle.STARTING) {
    coreBundle.start(Bundle.START_TRANSIENT);
}

before

Job.getJobManager().join(CopilotCore.INIT_JOB_FAMILY, null);

In CopilotUi.start()

Does the change make sense from your point of view?

[iloveeclipse]

Does the change make sense from your point of view

Core bundle should be already automatically started if any of the classes from it are used by Copilot UI. So I would not add any manual "hacks" to start it.

[jdneo]

@bobfields @haubi Is the problem stably reproducible on your side?

[haubi]

It is stably reproducible when our own plugin is installed, but IIRC I've also seen it once with some vanilla upstream setup, although not stably reproducible there.

Maybe irrelevant, but what I've also discovered is a difference on which thread executes com.microsoft.copilot.eclipse.ui.CopilotUi.start() method, i.e. which thread does activate the com.microsoft.copilot.eclipse.ui bundle:

• from within thread main : seems to work (more likely),
• from within thread Worker-#: Executing the early startup extensions: seems to break (more likely)

However, I've no idea about the conditions for which thread is the first one to activate (need) some bundle.

[jdneo]

I paid attention to this issue recently. Though that it cannot be stably reproduced, but I did encounter it several times.

But I've no idea why it will happen.

Given that the MANIFEST.MF declares that UI requires core, will OSGi guarantee that the CopilotCore.start() will be executed before CopilotUi.start()? @iloveeclipse do you have any insight?

[iloveeclipse]

Given that the MANIFEST.MF declares that UI requires core, will OSGi guarantee that the CopilotCore.start() will be executed before CopilotUi.start()

The point is not about dependency (which is correct), but about class loading.
CopilotCore.start() will be executed before CopilotUi.start() if some of the classes from CopilotCore bundle would be used by any other bundle (e.g. UI plugin code executed on start() would refer to some core plugin API). (Another possibility would be to specify start level of core bundle, but this is not what you want to do in your code.)

[jdneo]

UI plugin code executed on start() would refer to some core plugin API

UI do refer some code from core

Is this what you mean?