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csls

Migration

csls is a clean C# implementation. Protocol behavior is carried over as executable tests, then implemented with current Roslyn, StreamJsonRpc, System.CommandLine, and .NET hosting APIs. Old source layout, build machinery, and runtime assumptions are not copied into this repository.

The migration is capability based. A feature is complete when the server advertises it, its normal and failure behavior are covered over the real transport, and editor, CLI, or MCP integration uses that implementation. The server never advertises a placeholder capability.

Editor change

Section titled “Editor change”

Install csls, then replace the C# language-server command with:

Terminal window
csls lsp

Use csls as the configuration section. The csharp section is also read when an editor already emits it. Workspace roots, positions, and document versions remain standard LSP values, so editor-specific adapters are not required.

Run csls doctor from the workspace before changing an editor. It verifies SDK selection and loads the same Roslyn workspace used by the server. Then use csls sessions list after the editor starts to confirm that the live session is discoverable.

Behavior ledger

Section titled “Behavior ledger”

Ported behavior is tracked privately and expressed publicly through the feature tests and language-server reference. Protocol parity tests cover the expected result shapes. Additional tests cover current .NET features, Razor, file-based apps, multi-root workspaces, project file operations, Native AOT packaging, CLI control, MCP, and terminal editors.

$/csharp/debugInfo remains available for test synchronization and diagnosis. It reports current state rather than exposing implementation-specific objects.

Workspace differences

Section titled “Workspace differences”

The workspace is selected from the path sent by the client, not from the directory that happened to launch the editor. SDK projects honor global.json. File-based apps honor their directives. Legacy project evaluation uses an installed compatible Visual Studio, Build Tools, or Mono host when Roslyn requires one.

No state database is migrated. csls rebuilds Roslyn state from solutions, projects, source files, editor overlays, and current configuration each time a session starts.