Frequent error popup for on-save format in Eclipse EE 2025-09 (4.37.0).

After upgrading to Eclipse EE 2025-09 (4.37.0) on Windows, while editing Java files I'm frequently getting an error popup when I save. In "Preferences > Java > Editor > Save Actions" I have the following configured, which has been working for years and years:

```
[X] Perform the selected actions on save
[X] Format source code
( ) Format all lines
(*) Format edited lines
```

Nothing else is checked here. (Note that I'm using a custom formatting definition, i.e. which things to format and how.)

Two errors occur in the log, the second immediately after the first. (Irrelevant details redacted.)

```
eclipse.buildId=4.37.0.20250905-1455
java.version=21.0.8
java.vendor=Eclipse Adoptium
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Framework arguments: -product org.eclipse.epp.package.jee.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product

org.eclipse.jdt.ui
Error
Thu Sep 18 … 2025
Problems occurred when invoking code from plug-in: "org.eclipse.jdt.ui".

java.lang.RuntimeException: Error formating ….java
at org.eclipse.jdt.internal.ui.fix.CodeFormatCleanUp.createFix(CodeFormatCleanUp.java:74)
at org.eclipse.jdt.internal.corext.fix.CleanUpRefactoring.calculateChange(CleanUpRefactoring.java:792)
at org.eclipse.jdt.internal.corext.fix.CleanUpPostSaveListener.saved(CleanUpPostSaveListener.java:389)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider$4.run(CompilationUnitDocumentProvider.java:1610)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:47)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider.notifyPostSaveListeners(CompilationUnitDocumentProvider.java:1604)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider.commitWorkingCopy(CompilationUnitDocumentProvider.java:1388)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider$3.execute(CompilationUnitDocumentProvider.java:1463)
at org.eclipse.ui.editors.text.TextFileDocumentProvider$DocumentProviderOperation.run(TextFileDocumentProvider.java:133)
at org.eclipse.ui.actions.WorkspaceModifyDelegatingOperation.execute(WorkspaceModifyDelegatingOperation.java:71)
at org.eclipse.ui.actions.WorkspaceModifyOperation.lambda$0(WorkspaceModifyOperation.java:112)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2505)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2533)
at org.eclipse.ui.actions.WorkspaceModifyOperation.run(WorkspaceModifyOperation.java:131)
at org.eclipse.ui.internal.editors.text.WorkspaceOperationRunner.run(WorkspaceOperationRunner.java:76)
at org.eclipse.ui.internal.editors.text.WorkspaceOperationRunner.run(WorkspaceOperationRunner.java:66)
at org.eclipse.ui.editors.text.TextFileDocumentProvider.executeOperation(TextFileDocumentProvider.java:461)
at org.eclipse.ui.editors.text.TextFileDocumentProvider.saveDocument(TextFileDocumentProvider.java:783)
at org.eclipse.ui.texteditor.AbstractTextEditor.performSave(AbstractTextEditor.java:5020)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.performSave(CompilationUnitEditor.java:1262)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.doSave(CompilationUnitEditor.java:1316)
at org.eclipse.ui.texteditor.AbstractTextEditor$TextEditorSavable.doSave(AbstractTextEditor.java:7260)
at org.eclipse.ui.Saveable.doSave(Saveable.java:213)
at org.eclipse.ui.internal.SaveableHelper.doSaveModel(SaveableHelper.java:317)
at org.eclipse.ui.internal.SaveableHelper.lambda$1(SaveableHelper.java:195)
at org.eclipse.ui.internal.SaveableHelper.lambda$3(SaveableHelper.java:261)
at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:433)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:353)
at org.eclipse.ui.internal.WorkbenchWindow.lambda$7(WorkbenchWindow.java:2335)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:67)
at org.eclipse.ui.internal.WorkbenchWindow.run(WorkbenchWindow.java:2332)
at org.eclipse.ui.internal.SaveableHelper.runProgressMonitorOperation(SaveableHelper.java:268)
at org.eclipse.ui.internal.SaveableHelper.saveModels(SaveableHelper.java:206)
at org.eclipse.ui.internal.SaveableHelper.savePart(SaveableHelper.java:150)
at org.eclipse.ui.internal.WorkbenchPage.saveSaveable(WorkbenchPage.java:3819)
at org.eclipse.ui.internal.WorkbenchPage.saveEditor(WorkbenchPage.java:3832)
at org.eclipse.ui.internal.handlers.SaveHandler.execute(SaveHandler.java:81)
at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:277)
at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:98)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:58)
at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:305)
at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:237)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:174)
at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:165)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:488)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:485)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:204)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.executeCommand(KeyBindingDispatcher.java:320)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.press(KeyBindingDispatcher.java:581)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.processKeyEvent(KeyBindingDispatcher.java:662)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.filterKeySequenceBindings(KeyBindingDispatcher.java:451)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher$KeyDownFilter.handleEvent(KeyBindingDispatcher.java:104)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
at org.eclipse.swt.widgets.Display.filterEvent(Display.java:1340)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1213)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1238)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1223)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1265)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1261)
at org.eclipse.swt.widgets.Widget.wmChar(Widget.java:1748)
at org.eclipse.swt.widgets.Control.WM_CHAR(Control.java:4908)
at org.eclipse.swt.widgets.Canvas.WM_CHAR(Canvas.java:341)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4785)
at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:336)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:5130)
at org.eclipse.swt.internal.win32.OS.DispatchMessage(Native Method)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3746)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1151)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1042)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:678)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:583)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:185)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:219)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:149)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:115)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:467)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:298)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:627)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:575)
at org.eclipse.equinox.launcher.Main.run(Main.java:1431)
Caused by: java.lang.StringIndexOutOfBoundsException: Index -1 out of bounds for length 147
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
at java.base/java.lang.String.checkIndex(String.java:4832)
at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:46)
at java.base/java.lang.String.charAt(String.java:1555)
at org.eclipse.jdt.internal.formatter.TokenManager.countLineBreaksBetween(TokenManager.java:244)
at org.eclipse.jdt.internal.formatter.linewrap.WrapPreparator.applyBreaksOutsideRegions(WrapPreparator.java:1459)
at org.eclipse.jdt.internal.formatter.linewrap.WrapPreparator.finishUp(WrapPreparator.java:1393)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.prepareWraps(DefaultCodeFormatter.java:437)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.prepareFormattedCode(DefaultCodeFormatter.java:231)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.format(DefaultCodeFormatter.java:185)
at org.eclipse.jdt.internal.corext.util.CodeFormatterUtil.reformat(CodeFormatterUtil.java:396)
at org.eclipse.jdt.internal.corext.fix.CodeFormatFix.createCleanUp(CodeFormatFix.java:81)
at org.eclipse.jdt.internal.ui.fix.CodeFormatCleanUp.createFix(CodeFormatCleanUp.java:65)
... 87 more
```

```
eclipse.buildId=4.37.0.20250905-1455
java.version=21.0.8
java.vendor=Eclipse Adoptium
BootLoader constants: OS=win32, ARCH=x86_64, WS=win32, NL=en_US
Framework arguments: -product org.eclipse.epp.package.jee.product
Command-line arguments: -os win32 -ws win32 -arch x86_64 -product org.eclipse.epp.package.jee.product

org.eclipse.jdt.ui
Error
Thu Sep 18 … 2025
The save participant 'org.eclipse.jdt.ui.postsavelistener.cleanup' caused an exception: java.lang.RuntimeException: Error formating ….java

java.lang.RuntimeException: Error formating ….java
at org.eclipse.jdt.internal.ui.fix.CodeFormatCleanUp.createFix(CodeFormatCleanUp.java:74)
at org.eclipse.jdt.internal.corext.fix.CleanUpRefactoring.calculateChange(CleanUpRefactoring.java:792)
at org.eclipse.jdt.internal.corext.fix.CleanUpPostSaveListener.saved(CleanUpPostSaveListener.java:389)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider$4.run(CompilationUnitDocumentProvider.java:1610)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:47)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider.notifyPostSaveListeners(CompilationUnitDocumentProvider.java:1604)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider.commitWorkingCopy(CompilationUnitDocumentProvider.java:1388)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitDocumentProvider$3.execute(CompilationUnitDocumentProvider.java:1463)
at org.eclipse.ui.editors.text.TextFileDocumentProvider$DocumentProviderOperation.run(TextFileDocumentProvider.java:133)
at org.eclipse.ui.actions.WorkspaceModifyDelegatingOperation.execute(WorkspaceModifyDelegatingOperation.java:71)
at org.eclipse.ui.actions.WorkspaceModifyOperation.lambda$0(WorkspaceModifyOperation.java:112)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2505)
at org.eclipse.core.internal.resources.Workspace.run(Workspace.java:2533)
at org.eclipse.ui.actions.WorkspaceModifyOperation.run(WorkspaceModifyOperation.java:131)
at org.eclipse.ui.internal.editors.text.WorkspaceOperationRunner.run(WorkspaceOperationRunner.java:76)
at org.eclipse.ui.internal.editors.text.WorkspaceOperationRunner.run(WorkspaceOperationRunner.java:66)
at org.eclipse.ui.editors.text.TextFileDocumentProvider.executeOperation(TextFileDocumentProvider.java:461)
at org.eclipse.ui.editors.text.TextFileDocumentProvider.saveDocument(TextFileDocumentProvider.java:783)
at org.eclipse.ui.texteditor.AbstractTextEditor.performSave(AbstractTextEditor.java:5020)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.performSave(CompilationUnitEditor.java:1262)
at org.eclipse.jdt.internal.ui.javaeditor.CompilationUnitEditor.doSave(CompilationUnitEditor.java:1316)
at org.eclipse.ui.texteditor.AbstractTextEditor$TextEditorSavable.doSave(AbstractTextEditor.java:7260)
at org.eclipse.ui.Saveable.doSave(Saveable.java:213)
at org.eclipse.ui.internal.SaveableHelper.doSaveModel(SaveableHelper.java:317)
at org.eclipse.ui.internal.SaveableHelper.lambda$1(SaveableHelper.java:195)
at org.eclipse.ui.internal.SaveableHelper.lambda$3(SaveableHelper.java:261)
at org.eclipse.jface.operation.ModalContext.runInCurrentThread(ModalContext.java:433)
at org.eclipse.jface.operation.ModalContext.run(ModalContext.java:353)
at org.eclipse.ui.internal.WorkbenchWindow.lambda$7(WorkbenchWindow.java:2335)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:67)
at org.eclipse.ui.internal.WorkbenchWindow.run(WorkbenchWindow.java:2332)
at org.eclipse.ui.internal.SaveableHelper.runProgressMonitorOperation(SaveableHelper.java:268)
at org.eclipse.ui.internal.SaveableHelper.saveModels(SaveableHelper.java:206)
at org.eclipse.ui.internal.SaveableHelper.savePart(SaveableHelper.java:150)
at org.eclipse.ui.internal.WorkbenchPage.saveSaveable(WorkbenchPage.java:3819)
at org.eclipse.ui.internal.WorkbenchPage.saveEditor(WorkbenchPage.java:3832)
at org.eclipse.ui.internal.handlers.SaveHandler.execute(SaveHandler.java:81)
at org.eclipse.ui.internal.handlers.HandlerProxy.execute(HandlerProxy.java:277)
at org.eclipse.ui.internal.handlers.E4HandlerProxy.execute(E4HandlerProxy.java:98)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:58)
at org.eclipse.e4.core.internal.di.InjectorImpl.invokeUsingClass(InjectorImpl.java:305)
at org.eclipse.e4.core.internal.di.InjectorImpl.invoke(InjectorImpl.java:237)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.invoke(ContextInjectionFactory.java:174)
at org.eclipse.e4.core.commands.internal.HandlerServiceHandler.execute(HandlerServiceHandler.java:165)
at org.eclipse.core.commands.Command.executeWithChecks(Command.java:488)
at org.eclipse.core.commands.ParameterizedCommand.executeWithChecks(ParameterizedCommand.java:485)
at org.eclipse.e4.core.commands.internal.HandlerServiceImpl.executeHandler(HandlerServiceImpl.java:204)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.executeCommand(KeyBindingDispatcher.java:320)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.press(KeyBindingDispatcher.java:581)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.processKeyEvent(KeyBindingDispatcher.java:662)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher.filterKeySequenceBindings(KeyBindingDispatcher.java:451)
at org.eclipse.e4.ui.bindings.keys.KeyBindingDispatcher$KeyDownFilter.handleEvent(KeyBindingDispatcher.java:104)
at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
at org.eclipse.swt.widgets.Display.filterEvent(Display.java:1340)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1213)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1238)
at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1223)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1265)
at org.eclipse.swt.widgets.Widget.sendKeyEvent(Widget.java:1261)
at org.eclipse.swt.widgets.Widget.wmChar(Widget.java:1748)
at org.eclipse.swt.widgets.Control.WM_CHAR(Control.java:4908)
at org.eclipse.swt.widgets.Canvas.WM_CHAR(Canvas.java:341)
at org.eclipse.swt.widgets.Control.windowProc(Control.java:4785)
at org.eclipse.swt.widgets.Canvas.windowProc(Canvas.java:336)
at org.eclipse.swt.widgets.Display.windowProc(Display.java:5130)
at org.eclipse.swt.internal.win32.OS.DispatchMessage(Native Method)
at org.eclipse.swt.widgets.Display.readAndDispatch(Display.java:3746)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$5.run(PartRenderingEngine.java:1151)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:1042)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:153)
at org.eclipse.ui.internal.Workbench.lambda$3(Workbench.java:678)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:339)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:583)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:173)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:185)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:219)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:149)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:115)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:467)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:298)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:627)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:575)
at org.eclipse.equinox.launcher.Main.run(Main.java:1431)
Caused by: java.lang.StringIndexOutOfBoundsException: Index -1 out of bounds for length 147
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:55)
at java.base/jdk.internal.util.Preconditions$1.apply(Preconditions.java:52)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:213)
at java.base/jdk.internal.util.Preconditions$4.apply(Preconditions.java:210)
at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:98)
at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
at java.base/java.lang.String.checkIndex(String.java:4832)
at java.base/java.lang.StringLatin1.charAt(StringLatin1.java:46)
at java.base/java.lang.String.charAt(String.java:1555)
at org.eclipse.jdt.internal.formatter.TokenManager.countLineBreaksBetween(TokenManager.java:244)
at org.eclipse.jdt.internal.formatter.linewrap.WrapPreparator.applyBreaksOutsideRegions(WrapPreparator.java:1459)
at org.eclipse.jdt.internal.formatter.linewrap.WrapPreparator.finishUp(WrapPreparator.java:1393)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.prepareWraps(DefaultCodeFormatter.java:437)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.prepareFormattedCode(DefaultCodeFormatter.java:231)
at org.eclipse.jdt.internal.formatter.DefaultCodeFormatter.format(DefaultCodeFormatter.java:185)
at org.eclipse.jdt.internal.corext.util.CodeFormatterUtil.reformat(CodeFormatterUtil.java:396)
at org.eclipse.jdt.internal.corext.fix.CodeFormatFix.createCleanUp(CodeFormatFix.java:81)
at org.eclipse.jdt.internal.ui.fix.CodeFormatCleanUp.createFix(CodeFormatCleanUp.java:65)
... 87 more
```

On the face of the stack trace, I would guess there's a bug in `TokenManager.countLineBreaksBetween()`. Has this been modified since v2025-06?

Start by reproducing the save-time failure with Java files, the custom formatter, and the configured Save Actions. Trace the stack from org.eclipse.jdt.internal.ui.fix.CodeFormatCleanUp through CodeFormatterUtil to TokenManager.countLineBreaksBetween and WrapPreparator. Done means the same save scenario no longer raises the formatting exception.

Written by the indexing model from the issue text.