Claude Code for Visual Studio

A Visual Studio 2022 extension that implements the Claude Code IDE protocol — the same one the official Claude Code for VS Code extension uses — so the claude CLI can connect to Visual Studio and drive inline diffs, selection sharing, diagnostics lookup, and file navigation.

What it does

• Starts a local MCP server on 127.0.0.1:<random port> (WebSocket, JSON-RPC 2.0, MCP 2024-11-05).
• Writes a discovery lock file at %USERPROFILE%\.claude\ide\<port>.lock so claude /ide discovers "Visual Studio 2022" automatically.
• Exposes 11 MCP tools: get_workspace_folders, get_open_editors, get_current_selection, get_latest_selection, get_diagnostics, check_document_dirty, open_file, save_document, close_tab, close_all_diff_tabs, and the blocking open_diff that shows a native VS diff and waits for Accept/Reject.
• Emits selection_changed and at_mentioned notifications so Claude sees editor selections in real time.
• Ships a tool window showing server status and a one-click "Start Claude in terminal" button that pre-wires the env vars.

Requirements

• Visual Studio 2022 (17.0+) — Community, Professional, or Enterprise
• Visual Studio SDK workload (install via the VS Installer → "Visual Studio extension development")
• .NET Framework 4.7.2 targeting pack
• Claude Code CLI installed and on PATH (npm i -g @anthropic-ai/claude-code)

Build

1. Open ClaudeCodeVS.sln in Visual Studio 2022.
2. First build restores NuGet packages: Microsoft.VisualStudio.SDK, Microsoft.VSSDK.BuildTools, Newtonsoft.Json.
3. Press F5 — this launches the Visual Studio Experimental Instance with the extension loaded.
4. The packaged VSIX lands in src\ClaudeCodeVS\bin\Debug\ClaudeCodeVS.vsix. Double-click to install into your normal Visual Studio.

Verify end-to-end

1. In the Experimental Instance, open any solution.
2. Open View → Other Windows → Claude Code (or Tools → Open Claude Code Panel). The panel shows Running + a port number.
3. Confirm %USERPROFILE%\.claude\ide\<port>.lock exists and contains JSON with "ideName": "Visual Studio 2022", "transport": "ws", and an authToken.
4. In an external terminal, run claude. Then inside the chat: /ide. It should list Visual Studio 2022 and connect without an auth error.
5. Ask Claude: "list the files I have open" → it should invoke get_open_editors and return your tabs.
6. Select a block of code in the editor, press Ctrl+Alt+K → Claude receives at_mentioned with the selection.
7. Ask Claude to edit a file → a diff view opens. Press Ctrl+Alt+Y (Accept) to write the change, or Ctrl+Alt+N (Reject) to discard it.
8. Close Visual Studio → confirm the lock file is deleted.

Architecture

VsixPackage (AsyncPackage)
 ├─ IdeServices ───── DTE2, IVsTextManager, IVsDifferenceService, SVsErrorList
 ├─ SelectionTracker  IVsTextManagerEvents → debounced selection_changed
 ├─ DiffCoordinator   IVsDifferenceService.OpenComparisonWindow2 + TaskCompletionSource
 ├─ LockFileManager   ~/.claude/ide/<port>.lock (atomic write, sweep stale)
 ├─ McpWebSocketServer HttpListener → AcceptWebSocketAsync on 127.0.0.1:<10000..65535>
 │                     x-claude-code-ide-authorization header → AuthToken.ConstantTimeEquals
 ├─ JsonRpcDispatcher initialize, tools/list, tools/call, ping
 └─ ToolRegistry → 11 MCP tools under Protocol/Tools/

Security notes

• The server only binds to 127.0.0.1, so it is unreachable from other machines.
• Each VS session generates a fresh 48-byte random authToken (base64url). Connections without the x-claude-code-ide-authorization header are rejected with HTTP 401.
• Token comparison uses a constant-time check to prevent timing attacks (see CVE-2025-52882).
• The lock file is readable only by the user's profile (NTFS default ACLs).

Key files

• src/ClaudeCodeVS/VsixPackage.cs — entry point; starts server, writes lockfile, registers commands.
• src/ClaudeCodeVS/Protocol/McpWebSocketServer.cs — WebSocket server + auth.
• src/ClaudeCodeVS/Protocol/JsonRpcDispatcher.cs — MCP handshake + routing.
• src/ClaudeCodeVS/Protocol/Tools/ — 11 MCP tool handlers.
• src/ClaudeCodeVS/Ide/DiffCoordinator.cs — blocking open_diff implementation.
• src/ClaudeCodeVS/ClaudeCodePackage.vsct — menus + key bindings.

References

• Protocol reverse-engineering reference: https://github.com/coder/claudecode.nvim
• MCP specification: https://modelcontextprotocol.io/specification/2024-11-05
• Visual Studio SDK: https://learn.microsoft.com/en-us/visualstudio/extensibility/

License

MIT — see LICENSE.txt.