Replace native spawn with cross-spawn for improved cross-platform compatibility

package.json

@@ -48,6 +48,7 @@
   "dependencies": {
     "content-type": "^1.0.5",
     "cors": "^2.8.5",
+    "cross-spawn": "^7.0.3",
     "eventsource": "^3.0.2",
     "express": "^5.0.1",
     "express-rate-limit": "^7.5.0",

src/client/cross-spawn.test.ts

@@ -0,0 +1,112 @@
+import { StdioClientTransport } from "./stdio.js";
+import spawn from "cross-spawn";
+
+// mock cross-spawn
+jest.mock("cross-spawn");
+const mockSpawn = spawn as jest.MockedFunction<typeof spawn>;
+
+describe("StdioClientTransport using cross-spawn", () => {
+  beforeEach(() => {
+    // mock cross-spawn's return value
+    mockSpawn.mockImplementation(() => {
+      const mockProcess = {
+        on: jest.fn((event: string, callback: Function) => {
+          if (event === "spawn") {
+            callback();
+          }
+          return mockProcess;
+        }),
+        stdin: {
+          on: jest.fn(),
+          write: jest.fn().mockReturnValue(true)
+        },
+        stdout: {
+          on: jest.fn()
+        },
+        stderr: null
+      };
+      return mockProcess as any;
+    });
+  });
+
+  afterEach(() => {
+    jest.clearAllMocks();
+  });
+
+  test("should call cross-spawn correctly", async () => {
+    const transport = new StdioClientTransport({
+      command: "test-command",
+      args: ["arg1", "arg2"]
+    });
+    
+    await transport.start();
+    
+    // verify spawn is called correctly
+    expect(mockSpawn).toHaveBeenCalledWith(
+      "test-command",
+      ["arg1", "arg2"],
+      expect.objectContaining({
+        shell: false
+      })
+    );
+  });
+
+  test("should pass environment variables correctly", async () => {
+    const customEnv = { TEST_VAR: "test-value" };
+    const transport = new StdioClientTransport({
+      command: "test-command",
+      env: customEnv
+    });
+    
+    await transport.start();
+    
+    // verify environment variables are passed correctly
+    expect(mockSpawn).toHaveBeenCalledWith(
+      "test-command",
+      [],
+      expect.objectContaining({
+        env: customEnv
+      })
+    );
+  });
+
+  test("should send messages correctly", async () => {
+    const transport = new StdioClientTransport({
+      command: "test-command"
+    });
+    
+    // get the mock process object
+    const mockProcess = {
+      on: jest.fn((event, callback) => {
+        if (event === "spawn") {
+          callback();
+        }
+        return mockProcess;
+      }),
+      stdin: {
+        on: jest.fn(),
+        write: jest.fn().mockReturnValue(true),
+        once: jest.fn()
+      },
+      stdout: {
+        on: jest.fn()
+      },
+      stderr: null
+    };
+    
+    mockSpawn.mockReturnValue(mockProcess as any);
+    
+    await transport.start();
+    
+    const message = {
+      jsonrpc: "2.0",
+      id: "test-id",
+      method: "test-method"
+    };
+    
+    await transport.send(message);
+    
+    // verify message is sent correctly
+    expect(mockProcess.stdin.write).toHaveBeenCalled();
+  });
+});

src/client/stdio.ts

@@ -1,4 +1,5 @@
-import { ChildProcess, IOType, spawn } from "node:child_process";
+import { ChildProcess, IOType } from "node:child_process";
+import spawn from "cross-spawn";
 import process from "node:process";
 import { Stream } from "node:stream";
 import { ReadBuffer, serializeMessage } from "../shared/stdio.js";