From a3d6f96a45d25d52169a5833b5c650a58eb05660 Mon Sep 17 00:00:00 2001
From: shanevcantwell <153727980+shanevcantwell@users.noreply.github.com>
Date: Wed, 25 Feb 2026 23:00:13 -0700
Subject: [PATCH] fix: skip remote URIs when resolving MCP server cwd

When the extension runs in the Local Extension Host on Windows while
connected to a remote workspace (SSH, Dev Container, etc.),
getWorkspaceDirs() returns vscode-remote:// URIs. These cannot be used
as a cwd for child_process.spawn(), causing "spawn cmd.exe ENOENT"
when starting MCP stdio servers.

Fall back to the user's home directory for non-file:// URIs so the
spawn has a valid local working directory.

Fixes #10842

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 core/context/mcp/MCPConnection.ts        |  8 ++++++++
 core/context/mcp/MCPConnection.vitest.ts | 11 +++++++++++
 2 files changed, 19 insertions(+)

diff --git a/core/context/mcp/MCPConnection.ts b/core/context/mcp/MCPConnection.ts
index f1199066f2..d25e9f6a0e 100644
--- a/core/context/mcp/MCPConnection.ts
+++ b/core/context/mcp/MCPConnection.ts
@@ -1,5 +1,6 @@
 import { Client } from "@modelcontextprotocol/sdk/client/index.js";
 import { Transport } from "@modelcontextprotocol/sdk/shared/transport.js";
+import { homedir } from "os";
 import { fileURLToPath } from "url";
 
 import {
@@ -476,6 +477,13 @@ Org-level secrets can only be used for MCP by Background Agents (https://docs.co
         if (resolved.startsWith("file://")) {
           return fileURLToPath(resolved);
         }
+        // Remote URIs (e.g. vscode-remote://ssh-remote+host/path) cannot be
+        // used as a local cwd for child_process.spawn(). When the extension
+        // runs in the Local Extension Host on Windows while connected to a
+        // remote workspace, fall back to the user's home directory.
+        if (resolved.includes("://")) {
+          return homedir();
+        }
         return resolved;
       }
       return resolved;
diff --git a/core/context/mcp/MCPConnection.vitest.ts b/core/context/mcp/MCPConnection.vitest.ts
index 7920a9a1dd..adb4b9c549 100644
--- a/core/context/mcp/MCPConnection.vitest.ts
+++ b/core/context/mcp/MCPConnection.vitest.ts
@@ -175,6 +175,17 @@ describe("MCPConnection", () => {
       );
       expect(mockResolve).toHaveBeenCalledWith("src", ide);
     });
+
+    it("should fall back to homedir for remote URIs that cannot be used as local cwd", async () => {
+      const ide = {} as any;
+      vi.spyOn(ideUtils, "resolveRelativePathInDir").mockResolvedValue(
+        "vscode-remote://ssh-remote+192.168.137.2/home/user/project",
+      );
+      const conn = new MCPConnection(baseOptions, { ide });
+
+      const { homedir } = require("os");
+      await expect((conn as any).resolveCwd("src")).resolves.toBe(homedir());
+    });
   });
 
   describe("connectClient", () => {