VS Code: ArgumentOutOfRangeException when typing ignored preprocessor directive

[mm-jhn]

Version Used:

• VS Code 1.109.3
• C# extension 2.120.3
• C# Dev Kit 2.10.3

Steps to Reproduce:

1. Create a new document and set the language type to C#.
2. Type #:

Expected Behavior: No exception.

Actual Behavior:
Log output:

2026-02-20 14:12:05.722 [error] [textDocument/completion] [LanguageServerExtensionManager] Microsoft.CodeAnalysis.CSharp.Completion.Providers.KeywordCompletionProvider threw an exception. System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values. (Parameter 'position')
   at Microsoft.CodeAnalysis.Shared.Extensions.DocumentExtensions.ReuseExistingSpeculativeModelAsync(Document document, TextSpan span, CancellationToken cancellationToken)
   at Microsoft.CodeAnalysis.Completion.Utilities.CreateSyntaxContextWithExistingSpeculativeModelAsync(Document document, Int32 position, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/Completion/Utilities.cs:line 55
   at Microsoft.CodeAnalysis.Completion.Providers.AbstractKeywordCompletionProvider`1.RecommendCompletionItemsAsync(Document document, CompletionContext context, CancellationToken cancellationToken) in /_/src/Features/Core/Portable/Completion/Providers/AbstractKeywordCompletionProvider.cs:line 48
   at Microsoft.CodeAnalysis.Shared.Extensions.DocumentExtensions.GetUnionItemsFromDocumentAndLinkedDocumentsAsync[T](Document document, IEqualityComparer`1 comparer, Func`2 getItemsWorker) in /_/src/Features/Core/Portable/Shared/Extensions/DocumentExtensions.cs:line 64
   at Microsoft.CodeAnalysis.Completion.Providers.AbstractKeywordCompletionProvider`1.ProvideCompletionsAsync(CompletionContext context) in /_/src/Features/Core/Portable/Completion/Providers/AbstractKeywordCompletionProvider.cs:line 39
   at Microsoft.CodeAnalysis.Extensions.IExtensionManagerExtensions.PerformActionAsync(IExtensionManager extensionManager, Object extension, Func`1 function) in /_/src/Workspaces/Core/Portable/ExtensionManager/IExtensionManagerExtensions.cs:line 58

[mm-jhn]

OK, it doesn't appear to be related to the directive itself, I get many of these exceptions in the Output panel whenever I type code into the editor.