feat: enhance Windows MCP command quoting and add tests for cmd metacharacters

Author: qorzj

src/mcp/mcp-client.ts

@@ -427,7 +427,7 @@ export function createMcpSpawnSpec(
       // On Windows, shell: true lets cmd.exe resolve the command via PATHEXT
       // (npx -> npx.cmd, etc.). Join command and args into a single string
       // with empty spawn args to avoid Node 24 DEP0190.
-      // Only quote arguments that contain spaces or double-quotes to prevent
+      // Only quote arguments that need protection from cmd.exe to prevent
       // double-wrapping by Node.js's own shell quoting.
       command: [command, ...args].map(quoteWindowsArgIfNeeded).join(" "),
       args: [],
@@ -444,7 +444,7 @@ export function createMcpSpawnSpec(
 }
 
 function quoteWindowsArgIfNeeded(arg: string): string {
-  if (arg.includes(" ") || arg.includes('"')) {
+  if (/[\s"&|<>^()]/.test(arg)) {
     return `"${arg.replace(/(\\*)"/g, '$1$1\\"').replace(/\\+$/g, "$&$&")}"`;
   }
   return arg;

src/tests/mcp-client.test.ts

@@ -1,6 +1,9 @@
 import { test } from "node:test";
 import assert from "node:assert/strict";
-import { createMcpSpawnSpec } from "../mcp/mcp-client";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import path from "node:path";
+import { McpClient, createMcpSpawnSpec } from "../mcp/mcp-client";
 
 test("createMcpSpawnSpec keeps non-Windows MCP launches shell-free", () => {
   assert.deepEqual(createMcpSpawnSpec("npx", ["-y", "@playwright/mcp@latest"], "darwin"), {
@@ -32,3 +35,76 @@ test("createMcpSpawnSpec quotes Windows command paths and arguments", () => {
   );
   assert.deepEqual(spec.args, []);
 });
+
+test("createMcpSpawnSpec quotes Windows args with cmd metacharacters", () => {
+  const spec = createMcpSpawnSpec(
+    "npx",
+    [
+      "-y",
+      "some-mcp",
+      "--url=https://example.test?a=1&b=2",
+      "--pipe=a|b",
+      "--redirect=<in>out",
+      "--caret=^value",
+      "--group=(value)",
+    ],
+    "win32"
+  );
+
+  assert.equal(
+    spec.command,
+    [
+      "npx",
+      "-y",
+      "some-mcp",
+      '"--url=https://example.test?a=1&b=2"',
+      '"--pipe=a|b"',
+      '"--redirect=<in>out"',
+      '"--caret=^value"',
+      '"--group=(value)"',
+    ].join(" ")
+  );
+  assert.deepEqual(spec.args, []);
+});
+
+test("McpClient starts a PATH-resolved cmd MCP server on Windows", { skip: process.platform !== "win32" }, async () => {
+  const serverDir = mkdtempSync(path.join(tmpdir(), "deepcode-mcp-probe-"));
+  const originalPath = process.env.PATH;
+
+  writeFileSync(path.join(serverDir, "mcp-probe.cmd"), '@echo off\r\nnode "%~dp0mcp-probe-server.cjs"\r\n');
+  writeFileSync(
+    path.join(serverDir, "mcp-probe-server.cjs"),
+    [
+      'const readline = require("node:readline");',
+      "const rl = readline.createInterface({ input: process.stdin });",
+      "function send(message) { process.stdout.write(`${JSON.stringify(message)}\\n`); }",
+      'rl.on("line", (line) => {',
+      "  const request = JSON.parse(line);",
+      '  if (request.method === "initialize") {',
+      '    send({ jsonrpc: "2.0", id: request.id, result: { protocolVersion: "2025-03-26", capabilities: {}, serverInfo: { name: "probe", version: "1.0.0" } } });',
+      "    return;",
+      "  }",
+      '  if (request.method === "tools/list") {',
+      '    send({ jsonrpc: "2.0", id: request.id, result: { tools: [{ name: "probe_tool", inputSchema: { type: "object", properties: {} } }] } });',
+      "    return;",
+      "  }",
+      "});",
+    ].join("\n")
+  );
+
+  process.env.PATH = `${serverDir}${path.delimiter}${originalPath ?? ""}`;
+  const client = new McpClient("probe", "mcp-probe", []);
+
+  try {
+    await client.connect(5_000);
+    const tools = await client.listTools(5_000);
+    assert.deepEqual(
+      tools.map((tool) => tool.name),
+      ["probe_tool"]
+    );
+  } finally {
+    client.disconnect();
+    process.env.PATH = originalPath;
+    rmSync(serverDir, { recursive: true, force: true });
+  }
+});