Open-source .NET language server for C# and F#. Full Roslyn IntelliSense, diagnostics, refactoring, and NuGet management in VS Code, Zed, Neovim, and every LSP-compatible editor. 2026-06-09T21:57:22Z https://sharplsp.dev/ SharpLsp Team https://sharplsp.dev/blog/introducing-sharplsp/ 2026-03-20T00:00:00Z 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SharpLsp is an open-source, editor-agnostic Language Server for C# and F# — built in Rust, powered by Roslyn and FSharp.Compiler.Service. No licenses. No lock-in. Every editor.

https://sharplsp.dev/blog/why-fsharp-is-first-class-in-sharplsp/ 2026-04-26T00:00:00Z 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SharpLsp treats F# as a first-class .NET language because the F# community, compiler, tooling stack, and production success stories deserve tooling that is designed for F# from day one.

https://sharplsp.dev/blog/pull-diagnostics-without-phantom-errors/ 2026-04-27T00:00:00Z https://sharplsp.dev/%3Cp%3EDiagnostics%20are%20the%20developer%20feedback%20loop.%20The%20Problems%20panel%20is%20the%20place%20developers%20look%20to%20understand%20whether%20their%20code%20is%20correct.%20If%20it%20shows%20errors%20that%20do%20not%20exist,%20developers%20start%20ignoring%20it.%20If%20it%20misses%20errors%20that%20will%20break%20the%20build,%20developers%20get%20surprised%20in%20CI.%20Both%20failure%20modes%20destroy%20trust%20in%20the%20tooling.%3C/p%3E%3Cp%3ESharpLsp's%20diagnostic%20architecture%20has%20a%20single%20goal:%20%3Cstrong%3Eaccuracy%3C/strong%3E.%20Every%20error%20the%20compiler%20or%20an%20analyzer%20would%20report%20must%20appear%20in%20the%20editor.%20Every%20error%20that%20would%20not%20appear%20in%20a%20real%20build%20must%20be%20absent.%20The%20Problems%20panel%20should%20reflect%20exactly%20what%20%3Ccode%3Edotnet%20build%3C/code%3E%20would%20tell%20you%20%E2%80%94%20no%20more,%20no%20less.%3C/p%3E%3Cp%3EThat%20sounds%20simple.%20In%20practice%20it%20requires%20careful%20engineering%20around%20workspace%20lifecycle,%20the%20LSP%20protocol,%20and%20how%20Roslyn's%20analysis%20pipeline%20works.%3C/p%3E%3Ch2%20id=%22what-real-errors-look-like-in-roslyn%22%20tabindex=%22-1%22%3E%3Ca%20class=%22header-anchor%22%20href=%22#what-real-errors-look-like-in-roslyn%22%3EWhat%20"Real"%20Errors%20Look%20Like%20in%20Roslyn%3C/a%3E%3C/h2%3E%3Cp%3EThe%20%3Ca%20href=%22https://learn.microsoft.com/en-us/dotnet/csharp/roslyn-sdk/%22%3E.NET%20Compiler%20Platform%20(Roslyn)%3C/a%3E%20produces%20two%20broad%20categories%20of%20diagnostics,%20each%20with%20distinct%20prefixes%20and%20severity%20behaviors.%3C/p%3E%3Cp%3E%3Cstrong%3ECompiler%20diagnostics%3C/strong%3E%20carry%20a%20%3Ccode%3ECS%3C/code%3E%20prefix%20for%20C#%20and%20an%20%3Ccode%3EFS%3C/code%3E%20prefix%20for%20F#.%20These%20are%20the%20errors%20and%20warnings%20produced%20by%20the%20language%20compiler%20itself%20%E2%80%94%20type%20errors,%20missing%20members,%20syntax%20violations,%20unreachable%20code.%20A%20%3Ccode%3ECS0246%3C/code%3E%20means%20a%20type%20name%20could%20not%20be%20resolved.%20A%20%3Ccode%3ECS0019%3C/code%3E%20means%20an%20operator%20cannot%20be%20applied%20to%20the%20operand%20types.%20These%20diagnostics%20are%20authoritative:%20they%20reflect%20what%20the%20compiler%20knows%20about%20your%20code%20after%20full%20semantic%20analysis.%3C/p%3E%3Cp%3E%3Cstrong%3ERoslyn%20analyzer%20diagnostics%3C/strong%3E%20carry%20%3Ccode%3ECA%3C/code%3E%20(code%20quality)%20or%20%3Ccode%3EIDE%3C/code%3E%20(code%20style)%20prefixes%20and%20are%20documented%20in%20the%20%3Ca%20href=%22https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/overview%22%3E.NET%20code%20analysis%20overview%3C/a%3E.%20As%20Microsoft's%20documentation%20states:%3C/p%3E%3Cblockquote%3E%3Cp%3E"Code%20analysis%20violations%20appear%20with%20the%20prefix%20'CA'%20or%20'IDE'%20to%20differentiate%20them%20from%20compiler%20errors."%3C/p%3E%3C/blockquote%3E%3Cp%3EAnalyzer%20diagnostics%20are%20%3Ca%20href=%22https://learn.microsoft.com/en-us/dotnet/fundamentals/code-analysis/overview#enable-additional-rules%22%3Econfigurable%20in%20severity%3C/a%3E%20%E2%80%94%20they%20can%20be%20suggestions,%20warnings,%20or%20errors.%20When%20a%20team%20sets%20an%20analyzer%20rule%20to%20%3Ccode%3Eerror%3C/code%3E%20severity%20%E2%80%94%20via%20%3Ccode%3E.editorconfig%3C/code%3E,%20a%20%3Ccode%3E<TreatWarningsAsErrors>%3C/code%3E%20property,%20or%20a%20%3Ccode%3E<AnalysisMode>%3C/code%3E%20configuration%20%E2%80%94%20those%20diagnostics%20will%20fail%20the%20build.%20They%20are%20not%20optional%20noise.%20They%20are%20build-blocking%20errors.%20SharpLsp%20must%20surface%20them%20with%20the%20same%20prominence%20as%20%3Ccode%3ECS%3C/code%3E%20errors,%20because%20from%20the%20project's%20perspective%20they%20are%20equivalent.%3C/p%3E%3Cp%3EThird-party%20analyzer%20packages%20%E2%80%94%20%3Ca%20href=%22https://www.nuget.org/packages/StyleCop.Analyzers/%22%3EStyleCop%3C/a%3E,%20%3Ca%20href=%22https://www.nuget.org/packages/Roslynator.Analyzers/%22%3ERoslynator%3C/a%3E,%20%3Ca%20href=%22https://www.nuget.org/packages/Meziantou.Analyzer/%22%3EMeziantou.Analyzer%3C/a%3E,%20%3Ca%20href=%22https://www.nuget.org/packages/SonarAnalyzer.CSharp/%22%3ESonarAnalyzer%3C/a%3E%20%E2%80%94%20slot%20into%20the%20same%20pipeline.%20Their%20diagnostics%20are%20processed%20by%20Roslyn's%20%3Ccode%3EDiagnosticAnalyzer%3C/code%3E%20infrastructure%20and%20reported%20with%20the%20same%20severity%20model.%20SharpLsp%20does%20not%20treat%20these%20as%20second-class.%20If%20a%20StyleCop%20rule%20is%20configured%20as%20an%20error%20in%20your%20project,%20it%20appears%20as%20an%20error%20in%20the%20Problems%20panel,%20because%20it%20would%20appear%20as%20an%20error%20in%20your%20build.%3C/p%3E%3Ch2%20id=%22the-source-of-false-errors%22%20tabindex=%22-1%22%3E%3Ca%20class=%22header-anchor%22%20href=%22#the-source-of-false-errors%22%3EThe%20Source%20of%20False%20Errors%3C/a%3E%3C/h2%3E%3C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SharpLsp uses LSP 3.17 pull diagnostics to deliver solution-wide error accuracy — showing every real Roslyn and analyzer error, and nothing that isn't real.

https://sharplsp.dev/blog/editor-agnostic-dotnet-lsp/ 2026-04-28T00:00:00Z 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SharpLsp is building an open-source .NET LSP for C# and F# so language tooling can work across VS Code, Zed, Neovim, Helix, Emacs, Rider, and more.