Get started

Install

Prerequisite: Codex CLI. On macOS and Linux, also use Bash, curl and tar.

macOS and Linux:

curl -fsSL https://raw.githubusercontent.com/thomas-fazzari/roslyn-codex-lsp/master/install.sh | bash

Windows x64, in PowerShell:

& ([scriptblock]::Create((Invoke-RestMethod https://raw.githubusercontent.com/thomas-fazzari/roslyn-codex-lsp/master/install.ps1)))

The installer downloads the latest stable release, verifies its SHA-256 checksum and registers roslyn globally in Codex. Before making changes, it asks for an installation directory and offers an optional skill for C# diagnostics, navigation and edits. The skill comes from master, independently of the binary version. Files are stored in $XDG_DATA_HOME/roslyn-codex-lsp, or ~/.local/share/roslyn-codex-lsp when unset. Windows uses %LOCALAPPDATA%\roslyn-codex-lsp. Run the same command to update the bridge and skill.

Releases target macOS x64 and ARM64, Linux x64 and ARM64 with glibc, and Windows x64.

Use --version vX.Y.Z to select a release, or --yes for unattended installation. When piping the shell installer, pass options through bash -s -- --yes. PowerShell accepts -Version vX.Y.Z and -Yes. Use --no-skill or -NoSkill to skip skill installation.

Language server

The installer offers to install the official Roslyn language server. This optional step requires the .NET 10 SDK to run dotnet tool install. Roslyn itself uses the .NET 10 runtime. The native bridge has no .NET runtime requirement.

If Roslyn is already installed, choose its executable during setup or pass --server /path/to/roslyn-language-server (-Server in PowerShell). The installer then skips the .NET SDK check and server installation.

Your C# project can target a different .NET version. Keep its required SDK and workloads installed, including any SDK pinned in its global.json.

Use it

Restore your C# solution with dotnet restore, then open a new Codex session in that project. In the CLI, use /mcp to check that roslyn is connected.

Use the Roslyn MCP to report diagnostics for a C# file, find definitions and
implementations, then preview a rename and a suggested fix. Do not apply changes.

Approve the tool call if prompted. The bridge uses the session's working directory as its workspace. Save editor changes before requesting diagnostics.

Configuration

Codex stores the global registration in ~/.codex/config.toml, or under CODEX_HOME when set. A project-level .codex/config.toml can override it. See Codex MCP configuration for client settings and tool approvals.

Roslyn loads the solution on the first language request. For large projects, set tool_timeout_sec = 200 under [mcp_servers.roslyn].

Bridge argument	Default
--workspace	Current working directory
--server	roslyn-language-server on PATH
--startup-timeout	120 seconds
--request-timeout	60 seconds

Timeout arguments accept 1 to 600 seconds. Keep Codex's tool timeout above the startup and request timeout sum when increasing these limits.

Remove

Run codex mcp remove roslyn, then delete the installation directory and optional skill directory printed by the installer.