fix(mcp): support custom Chrome user data dirs

__tests__/mcp-installer.spec.ts

@@ -1,16 +1,180 @@
 import { spawnSync } from "node:child_process";
+import fs from "node:fs";
+import os from "node:os";
 import path from "node:path";
-import { describe, expect, it } from "vitest";
+import { afterEach, beforeAll, describe, expect, it } from "vitest";
+
+const INSTALLER = path.resolve("mcp/install-host.js");
+const EXTENSION_ID = "idkjhjggpffolpidfkikidcokdkdaogg";
+const sandboxes: string[] = [];
+
+function createSandbox(): string {
+  const sandbox = fs.mkdtempSync(path.join(os.tmpdir(), "xswitch-mcp-test-"));
+  sandboxes.push(sandbox);
+  return sandbox;
+}
+
+function runInstaller(
+  args: string[],
+  environment: Record<string, string>
+) {
+  return spawnSync(process.execPath, [INSTALLER, ...args], {
+    encoding: "utf8",
+    env: {
+      ...process.env,
+      XSWITCH_MCP_MANIFEST_PATH: "",
+      XSWITCH_MCP_USER_DATA_DIR: "",
+      ...environment,
+    },
+  });
+}
 
 describe("XSwitch MCP installer", () => {
-  it("requires an explicit extension ID instead of using a stale default", () => {
+  beforeAll(() => {
     const result = spawnSync(
-      process.execPath,
-      [path.resolve("mcp/install-host.js"), "install"],
+      process.platform === "win32" ? "npm.cmd" : "npm",
+      ["--prefix", "mcp", "run", "build"],
       { encoding: "utf8" }
     );
+    expect(result.status, result.stderr).toBe(0);
+  });
+
+  afterEach(() => {
+    for (const sandbox of sandboxes.splice(0)) {
+      fs.rmSync(sandbox, { recursive: true, force: true });
+    }
+  });
+
+  it("requires an explicit extension ID instead of using a stale default", () => {
+    const result = spawnSync(process.execPath, [INSTALLER, "install"], {
+      encoding: "utf8",
+    });
 
     expect(result.status).toBe(1);
     expect(result.stderr).toContain("--extension-id is required for install");
   });
+
+  it("installs and uninstalls inside a custom user data directory", () => {
+    const sandbox = createSandbox();
+    const installDirectory = path.join(sandbox, "runtime install");
+    const userDataDirectory = path.join(sandbox, "Chrome Debug");
+    const manifestPath = path.join(
+      userDataDirectory,
+      "NativeMessagingHosts",
+      "com.xswitch.mcp.json"
+    );
+
+    const install = runInstaller(
+      [
+        "install",
+        "--extension-id",
+        EXTENSION_ID,
+        "--user-data-dir",
+        userDataDirectory,
+      ],
+      { XSWITCH_MCP_INSTALL_DIR: installDirectory }
+    );
+
+    expect(install.status, install.stderr).toBe(0);
+    expect(install.stdout).toContain(manifestPath);
+    const manifest = JSON.parse(fs.readFileSync(manifestPath, "utf8"));
+    expect(manifest.path).toBe(path.join(installDirectory, "native-host"));
+    expect(manifest.allowed_origins).toEqual([
+      `chrome-extension://${EXTENSION_ID}/`,
+    ]);
+
+    const uninstall = runInstaller(
+      ["uninstall", "--user-data-dir", userDataDirectory],
+      { XSWITCH_MCP_INSTALL_DIR: installDirectory }
+    );
+
+    expect(uninstall.status, uninstall.stderr).toBe(0);
+    expect(fs.existsSync(manifestPath)).toBe(false);
+  });
+
+  it("supports the --user-data-dir=<path> form", () => {
+    const sandbox = createSandbox();
+    const installDirectory = path.join(sandbox, "install");
+    const userDataDirectory = path.join(sandbox, "Chrome Debug");
+    const manifestPath = path.join(
+      userDataDirectory,
+      "NativeMessagingHosts",
+      "com.xswitch.mcp.json"
+    );
+
+    const result = runInstaller(
+      [
+        "install",
+        "--extension-id",
+        EXTENSION_ID,
+        `--user-data-dir=${userDataDirectory}`,
+      ],
+      { XSWITCH_MCP_INSTALL_DIR: installDirectory }
+    );
+
+    expect(result.status, result.stderr).toBe(0);
+    expect(fs.existsSync(manifestPath)).toBe(true);
+  });
+
+  it("supports XSWITCH_MCP_USER_DATA_DIR for automation", () => {
+    const sandbox = createSandbox();
+    const installDirectory = path.join(sandbox, "install");
+    const userDataDirectory = path.join(sandbox, "Automated Chrome");
+    const manifestPath = path.join(
+      userDataDirectory,
+      "NativeMessagingHosts",
+      "com.xswitch.mcp.json"
+    );
+
+    const result = runInstaller(["install", "--extension-id", EXTENSION_ID], {
+      XSWITCH_MCP_INSTALL_DIR: installDirectory,
+      XSWITCH_MCP_USER_DATA_DIR: userDataDirectory,
+    });
+
+    expect(result.status, result.stderr).toBe(0);
+    expect(fs.existsSync(manifestPath)).toBe(true);
+  });
+
+  it("gives the exact manifest path override highest precedence", () => {
+    const sandbox = createSandbox();
+    const installDirectory = path.join(sandbox, "install");
+    const userDataDirectory = path.join(sandbox, "Chrome Debug");
+    const manifestPath = path.join(sandbox, "exact", "host.json");
+    const userDataManifestPath = path.join(
+      userDataDirectory,
+      "NativeMessagingHosts",
+      "com.xswitch.mcp.json"
+    );
+
+    const result = runInstaller(
+      [
+        "install",
+        "--extension-id",
+        EXTENSION_ID,
+        "--user-data-dir",
+        userDataDirectory,
+      ],
+      {
+        XSWITCH_MCP_INSTALL_DIR: installDirectory,
+        XSWITCH_MCP_MANIFEST_PATH: manifestPath,
+      }
+    );
+
+    expect(result.status, result.stderr).toBe(0);
+    expect(fs.existsSync(manifestPath)).toBe(true);
+    expect(fs.existsSync(userDataManifestPath)).toBe(false);
+  });
+
+  it("rejects an empty --user-data-dir value", () => {
+    const sandbox = createSandbox();
+    const result = runInstaller(
+      ["install", "--extension-id", EXTENSION_ID, "--user-data-dir="],
+      { XSWITCH_MCP_INSTALL_DIR: path.join(sandbox, "install") }
+    );
+
+    expect(result.status).toBe(1);
+    expect(result.stderr).toContain(
+      "--user-data-dir requires a non-empty path"
+    );
+  });
 });

mcp/README.md

@@ -9,6 +9,25 @@ npx --yes xswitch-mcp install --extension-id <your-extension-id>
 The installer copies a self-contained runtime to `~/.xswitch/runtime` and registers
 the Native Messaging host for Chrome. A source checkout is not required.
 
+If Chrome is launched with a custom `--user-data-dir`, pass the same directory to
+the installer. Chrome looks for per-user Native Messaging manifests inside that
+data directory rather than its default application support directory.
+
+```bash
+npx --yes xswitch-mcp install \
+  --extension-id <your-extension-id> \
+  --user-data-dir "/path/to/chrome-user-data"
+```
+
+The manifest is written to
+`<user-data-dir>/NativeMessagingHosts/com.xswitch.mcp.json`. Pass the user data
+root itself, not a profile directory such as `Default` or `Profile 1`.
+
+For automation, `XSWITCH_MCP_USER_DATA_DIR` provides the same setting.
+`XSWITCH_MCP_MANIFEST_PATH` remains available as an exact manifest path override
+and takes precedence over both the CLI option and the user data directory
+environment variable.
+
 Every write creates a local snapshot in the XSwitch extension first. Failed writes
 are rolled back automatically, and MCP clients can list or restore the 10 most
 recent snapshots with `list_xswitch_backups` and `restore_xswitch_backup`.
@@ -18,3 +37,6 @@ To remove the Chrome registration:
 ```bash
 npx --yes xswitch-mcp uninstall
 ```
+
+Use the same `--user-data-dir` option when removing a registration from a custom
+browser data directory.

mcp/install-host.js

@@ -16,6 +16,7 @@ function parseArgs(argv) {
   const options = {
     browser: "chrome",
     extensionId: undefined,
+    userDataDir: undefined,
     uninstall: false,
   };
   for (let index = 0; index < argv.length; index += 1) {
@@ -24,17 +25,22 @@ function parseArgs(argv) {
     if (arg === "uninstall") options.uninstall = true;
     else if (arg === "--browser") options.browser = argv[++index];
     else if (arg === "--extension-id") options.extensionId = argv[++index];
-    else if (arg === "--uninstall") options.uninstall = true;
+    else if (arg === "--user-data-dir") options.userDataDir = argv[++index];
+    else if (arg.startsWith("--user-data-dir=")) {
+      options.userDataDir = arg.slice("--user-data-dir=".length);
+    } else if (arg === "--uninstall") options.uninstall = true;
     else if (arg === "--help" || arg === "-h") {
       console.log(`Usage: xswitch-mcp install [options]
 
 Options:
   --browser chrome|chromium|edge  Browser to register (default: chrome)
   --extension-id <id>            Installed extension ID (required for install)
+  --user-data-dir <path>         Custom browser --user-data-dir
   --uninstall                    Remove the native host registration
 
 Examples:
   npx --yes xswitch-mcp install --extension-id <extension-id>
+  npx --yes xswitch-mcp install --extension-id <extension-id> --user-data-dir <path>
   npx --yes xswitch-mcp uninstall`);
       process.exit(0);
     } else throw new Error(`Unknown argument: ${arg}`);
@@ -48,12 +54,24 @@ Examples:
   if (options.extensionId && !/^[a-p]{32}$/.test(options.extensionId)) {
     throw new Error("extension-id must be a 32-character Chrome extension ID");
   }
+  if (options.userDataDir !== undefined && !options.userDataDir) {
+    throw new Error("--user-data-dir requires a non-empty path");
+  }
   return options;
 }
 
-function manifestLocation(browser) {
+function manifestLocation(browser, userDataDir) {
   if (process.env.XSWITCH_MCP_MANIFEST_PATH) {
-    return process.env.XSWITCH_MCP_MANIFEST_PATH;
+    return path.resolve(process.env.XSWITCH_MCP_MANIFEST_PATH);
+  }
+  const customUserDataDirectory =
+    userDataDir || process.env.XSWITCH_MCP_USER_DATA_DIR;
+  if (customUserDataDirectory) {
+    return path.join(
+      path.resolve(customUserDataDirectory),
+      "NativeMessagingHosts",
+      `${HOST_NAME}.json`
+    );
   }
   if (process.platform === "darwin") {
     const folders = {
@@ -126,7 +144,7 @@ function installRuntime() {
 }
 
 const options = parseArgs(process.argv.slice(2));
-const manifestPath = manifestLocation(options.browser);
+const manifestPath = manifestLocation(options.browser, options.userDataDir);
 
 if (options.uninstall) {
   if (fs.existsSync(manifestPath)) fs.unlinkSync(manifestPath);

mcp/package.json

@@ -1,6 +1,6 @@
 {
   "name": "xswitch-mcp",
-  "version": "0.2.3",
+  "version": "0.3.1",
   "description": "Local MCP bridge for configuring XSwitch rules with AI clients",
   "type": "module",
   "license": "MIT",