java.lang.IllegalArgumentException: Argument for @NotNull parameter 'fileType' of com/intellij/ide/highlighter/HighlighterFactory.createHighlighter must not be null

We are GitHub Copilot for JetBrains plugin team. And our cx meet with a blank toolWindow issue. The error stack shows there might be a NPE problem, and we check that content in contentManager.addContent(content) is not null. The error stack is listed below. Could you pls help to find the root cause, thank you.

- IDE & OS Versions:
JetBrains Rider 2024.3.6
Build #RD-243.25659.34, built on February 26, 2025
Subscription is active until April 12, 2025.
Runtime version: 21.0.6+8-b631.39 amd64 (JCEF 122.1.9)
VM: OpenJDK 64-Bit Server VM by JetBrains s.r.o.
Toolkit: sun.awt.windows.WToolkit
Windows 11.0
.NET Core v8.0.11 x64 (Server GC)
GC: G1 Young Generation, G1 Concurrent GC, G1 Old Generation
Memory: 4052M
Cores: 20
Registry:
ide.experimental.ui=true
llm.show.ai.promotion.window.on.start=false
Non-Bundled Plugins:
com.jetbrains.rider.android (243.25659.34)
com.github.copilot (1.5.39-243)

Error stack:

java.lang.IllegalArgumentException: Argument for @NotNull parameter 'fileType' of com/intellij/ide/highlighter/HighlighterFactory.createHighlighter must not be null
	at com.intellij.ide.highlighter.HighlighterFactory.$$$reportNull$$$0(HighlighterFactory.java)
	at com.intellij.ide.highlighter.HighlighterFactory.createHighlighter(HighlighterFactory.java)
	at com.intellij.ui.LanguageTextField.createEditor(LanguageTextField.java:119)
	at com.intellij.ui.EditorTextFieldProviderImpl$MyEditorTextField.createEditor(EditorTextFieldProviderImpl.java:35)
	at com.intellij.ui.EditorTextField.initEditorInner(EditorTextField.java:551)
	at com.intellij.ui.EditorTextField.initEditor(EditorTextField.java:536)
	at com.intellij.ui.EditorTextField.getEditor(EditorTextField.java:986)
	at com.intellij.ui.EditorTextField.getPreferredSize(EditorTextField.java:888)
	at java.desktop/java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:724)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at com.github.copilot.chat.message.codeblock.CodeBlockPanel$codeBlockDisplayPanel$1.getPreferredSize(CodeBlockPanel.kt:53)
	at java.desktop/javax.swing.OverlayLayout.checkRequests(OverlayLayout.java:269)
	at java.desktop/javax.swing.OverlayLayout.preferredLayoutSize(OverlayLayout.java:140)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at java.desktop/java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:724)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at org.jdesktop.swingx.VerticalLayout.preferredLayoutSize(VerticalLayout.java:80)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at org.jdesktop.swingx.VerticalLayout.preferredLayoutSize(VerticalLayout.java:80)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at java.desktop/java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:724)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at java.desktop/java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:724)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at java.desktop/java.awt.BorderLayout.preferredLayoutSize(BorderLayout.java:724)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at java.desktop/java.awt.GridBagLayout.GetLayoutInfo(GridBagLayout.java:1111)
	at java.desktop/java.awt.GridBagLayout.getLayoutInfo(GridBagLayout.java:906)
	at java.desktop/java.awt.GridBagLayout.preferredLayoutSize(GridBagLayout.java:726)
	at java.desktop/java.awt.Container.preferredSize(Container.java:1826)
	at java.desktop/java.awt.Container.getPreferredSize(Container.java:1810)
	at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1732)
	at com.intellij.ui.components.JBScrollPane$Layout.layoutContainer(JBScrollPane.java:573)
	at java.desktop/java.awt.Container.layout(Container.java:1541)
	at java.desktop/java.awt.Container.doLayout(Container.java:1530)
	at java.desktop/java.awt.Container.validateTree(Container.java:1725)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validateTree(Container.java:1734)
	at java.desktop/java.awt.Container.validate(Container.java:1660)
	at java.desktop/javax.swing.RepaintManager$3.run(RepaintManager.java:762)
	at java.desktop/javax.swing.RepaintManager$3.run(RepaintManager.java:760)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.desktop/javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:759)
	at java.desktop/javax.swing.RepaintManager$ProcessingRunnable.run(RepaintManager.java:1920)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:781)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:728)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:722)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:750)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.kt:696)
	at com.intellij.ide.IdeEventQueue._dispatchEvent$lambda$16(IdeEventQueue.kt:590)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.runWithoutImplicitRead(AnyThreadWriteThreadingSupport.kt:117)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.kt:590)
	at com.intellij.ide.IdeEventQueue.access$_dispatchEvent(IdeEventQueue.kt:73)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1$1.compute(IdeEventQueue.kt:357)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1$1.compute(IdeEventQueue.kt:356)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:843)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1.invoke(IdeEventQueue.kt:356)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1.invoke(IdeEventQueue.kt:351)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke$lambda$0(IdeEventQueue.kt:1035)
	at com.intellij.openapi.application.WriteIntentReadAction.lambda$run$0(WriteIntentReadAction.java:24)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.runWriteIntentReadAction(AnyThreadWriteThreadingSupport.kt:84)
	at com.intellij.openapi.application.impl.ApplicationImpl.runWriteIntentReadAction(ApplicationImpl.java:910)
	at com.intellij.openapi.application.WriteIntentReadAction.compute(WriteIntentReadAction.java:55)
	at com.intellij.openapi.application.WriteIntentReadAction.run(WriteIntentReadAction.java:23)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke(IdeEventQueue.kt:1035)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke(IdeEventQueue.kt:1035)
	at com.intellij.ide.IdeEventQueueKt.performActivity$lambda$1(IdeEventQueue.kt:1036)
	at com.intellij.openapi.application.TransactionGuardImpl.performActivity(TransactionGuardImpl.java:106)
	at com.intellij.ide.IdeEventQueueKt.performActivity(IdeEventQueue.kt:1036)
	at com.intellij.ide.IdeEventQueue.dispatchEvent$lambda$10(IdeEventQueue.kt:351)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.kt:389)
	at com.intellij.ide.IdeEventQueue.attachClientIdIfNeeded$lambda$27(IdeEventQueue.kt:864)
	at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:318)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:781)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:728)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:722)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:87)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:750)
	at com.intellij.ide.IdeEventQueue.defaultDispatchEvent(IdeEventQueue.kt:696)
	at com.intellij.ide.IdeEventQueue._dispatchEvent$lambda$16(IdeEventQueue.kt:590)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.runWithoutImplicitRead(AnyThreadWriteThreadingSupport.kt:117)
	at com.intellij.ide.IdeEventQueue._dispatchEvent(IdeEventQueue.kt:590)
	at com.intellij.ide.IdeEventQueue.access$_dispatchEvent(IdeEventQueue.kt:73)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1$1.compute(IdeEventQueue.kt:357)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1$1.compute(IdeEventQueue.kt:356)
	at com.intellij.openapi.progress.impl.CoreProgressManager.computePrioritized(CoreProgressManager.java:843)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1.invoke(IdeEventQueue.kt:356)
	at com.intellij.ide.IdeEventQueue$dispatchEvent$processEventRunnable$1$1$1.invoke(IdeEventQueue.kt:351)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke$lambda$0(IdeEventQueue.kt:1035)
	at com.intellij.openapi.application.WriteIntentReadAction.lambda$run$0(WriteIntentReadAction.java:24)
	at com.intellij.openapi.application.impl.AnyThreadWriteThreadingSupport.runWriteIntentReadAction(AnyThreadWriteThreadingSupport.kt:84)
	at com.intellij.openapi.application.impl.ApplicationImpl.runWriteIntentReadAction(ApplicationImpl.java:910)
	at com.intellij.openapi.application.WriteIntentReadAction.compute(WriteIntentReadAction.java:55)
	at com.intellij.openapi.application.WriteIntentReadAction.run(WriteIntentReadAction.java:23)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke(IdeEventQueue.kt:1035)
	at com.intellij.ide.IdeEventQueueKt$performActivity$runnableWithWIL$1.invoke(IdeEventQueue.kt:1035)
	at com.intellij.ide.IdeEventQueueKt.performActivity$lambda$1(IdeEventQueue.kt:1036)
	at com.intellij.openapi.application.TransactionGuardImpl.performActivity(TransactionGuardImpl.java:106)
	at com.intellij.ide.IdeEventQueueKt.performActivity(IdeEventQueue.kt:1036)
	at com.intellij.ide.IdeEventQueue.dispatchEvent$lambda$10(IdeEventQueue.kt:351)
	at com.intellij.ide.IdeEventQueue.dispatchEvent(IdeEventQueue.kt:397)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:207)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
	at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
	at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
	at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:92)

Similar issue in YouTrack: GitHub Copilot Chat crash : LLM-16123
We have detailed idea.log if anything else need

Hi, could you please build a small reproducer example? It is rather hard to help you having only stacktrace

Hi, we found another similar issue in https://youtrack.jetbrains.com/issue/LLM-16123/GitHub-Copilot-Chat-crash, see comments here, there might be some bugs in internal API.

Besides, we are asking customers for more info about code block, any details will let you know.
One customer use Groovy, and another use ASCII, more details in Chat window blank/won't come up · Issue #6 · microsoft/copilot-intellij-feedback · GitHub