diff --git a/Makefile b/Makefile
index ca69504..9940bed 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: all build test gui gui-dev gui-dist gui-deb gui-win gui-win-docker help clean
+.PHONY: all build test gui gui-dev gui-dist gui-deb gui-win gui-win-docker help clean gui-test
 
 # ModelRouter - single-binary gateway + optional Electron desktop GUI (embedded core)
 export BINARY
@@ -65,6 +65,13 @@ gui-dist-dir:
 test:
 	go test ./...
 
+# Desktop shell unit tests (no Electron needed): plugin-tree seeding/migration.
+# These guard the two things that silently break the desktop build:
+#   - plugin_dir missing from an embedded profile  -> channels plugin invisible
+#   - bundled plugin files never refreshed         -> old channels.lua survives upgrades
+gui-test:
+	@cd $(GUI_DIR) && node --test plugin-sync.test.js
+
 clean:
 	rm -rf $(BUILD_DIR) cmd/build cmd/gui/dist cmd/gui/build/gui-dist cmd/gui/bin
 
@@ -75,6 +82,7 @@ help:
 	@echo "  make gui        run desktop GUI (dev)"
 	@echo "  make gui-dev    run GUI with devtools"
 	@echo "  make gui-dist   build deb + rpm + AppImage (linux)"
+	@echo "  make gui-test   desktop shell unit tests (plugin tree seeding)"
 	@echo "  make gui-deb    build deb only"
 	@echo "  make gui-win    build Windows nsis (needs host mingw + wine)"
 	@echo "  make gui-win-docker  build Windows nsis all-in-docker (no host mingw needed)"
diff --git a/cmd/gui/main.js b/cmd/gui/main.js
index abc6ea9..94dc370 100644
--- a/cmd/gui/main.js
+++ b/cmd/gui/main.js
@@ -18,6 +18,7 @@ const http = require("http");
 const os = require("os");
 const crypto = require("crypto");
 const { spawn, execFileSync } = require("child_process");
+const pluginSync = require("./plugin-sync");
 
 const LOG_FILE = path.join(app.getPath("userData"), "gui.log");
 function log(msg) {
@@ -40,6 +41,13 @@ console.error = function () {
 // Per-user profile dir: <userData>/profile
 const PROFILE_DIR = path.join(app.getPath("userData"), "profile");
 const CONFIG_FILE = path.join(PROFILE_DIR, "config.yaml");
+// Plugin tree for the embedded core. The core deliberately does NOT default
+// plugin_dir (an operator opts in), so the desktop build must set it — without
+// it the whole plugin system stays off and the channels plugin (multi-platform
+// account login + credential vault + auto check-in) is invisible in the WebUI.
+// Seeding is the core's job (SeedBundled fills MISSING files only), so a user's
+// edited copy always wins.
+const PLUGINS_DIR = path.join(PROFILE_DIR, "plugins");
 // Packaged: extraResource at process.resourcesPath/bin (outside asar, spawnable).
 // Dev:   cmd/gui/bin, populated by prepare-core.js.
 const CORE_EXE = path.join(
@@ -216,6 +224,9 @@ function writeDefaultEmbeddedConfig() {
     "listen: 127.0.0.1:" + (settings.port || DEFAULT_PORT),
     "default_model: AUTO",
     "adapter_dir: " + JSON.stringify(path.join(PROFILE_DIR, "adapters")),
+    // Plugin tree: channels/billing/quota/usage ship inside the core binary and
+    // are seeded into this dir on first start. Omitting it disables plugins.
+    "plugin_dir: " + JSON.stringify(PLUGINS_DIR),
     "runtime_file: " + JSON.stringify(path.join(PROFILE_DIR, "runtime.json")),
     "",
     // Admin key as a plain `keys` entry (no seed flag) so the web UI never
@@ -268,6 +279,9 @@ function startCore() {
   // ensure profile dir + config + local adapters exist
   fs.mkdirSync(PROFILE_DIR, { recursive: true });
   if (!fs.existsSync(CONFIG_FILE)) writeDefaultEmbeddedConfig();
+  pluginSync.ensurePluginDirConfigured(CONFIG_FILE, PLUGINS_DIR, log);
+  fs.mkdirSync(PLUGINS_DIR, { recursive: true });
+  pluginSync.syncBundledPluginsOnUpgrade(PROFILE_DIR, PLUGINS_DIR, app.getVersion(), log);
 
   coreProc = spawn(CORE_EXE, ["-config", CONFIG_FILE], {
     cwd: PROFILE_DIR,
@@ -622,10 +636,55 @@ function createWindow() {
     },
   });
   mainWindow.loadFile(path.join(__dirname, "renderer", "index.html"));
+  // External links ALWAYS go to the user's default browser, never an in-app
+  // window. Three paths have to be covered, and missing any one of them is why
+  // "click the login link and nothing happens / the app navigates away" shows up:
+  //   1. window.open / target=_blank            -> setWindowOpenHandler
+  //   2. top-level navigation (same-tab click)  -> will-navigate
+  //   3. navigation inside the WebUI <iframe>   -> will-frame-navigate
+  // The embedded core's own origin (and file:// for the shell) must keep
+  // working, otherwise the WebUI and plugin pages stop loading.
+  const isInternal = (url) =>
+    !url ||
+    url === "about:blank" ||
+    url.startsWith("file://") ||
+    url.startsWith(embeddedBaseUrl()) ||
+    url.startsWith("devtools://");
+  const openExternally = (url) => {
+    if (url && (url.startsWith("http://") || url.startsWith("https://"))) {
+      log("[gui] open in default browser: " + url);
+      shell.openExternal(url);
+    }
+  };
   mainWindow.webContents.setWindowOpenHandler(({ url }) => {
-    if (url && url.startsWith("http")) shell.openExternal(url);
+    if (!isInternal(url)) openExternally(url);
     return { action: "deny" };
   });
+  mainWindow.webContents.on("will-navigate", (e, url) => {
+    if (isInternal(url)) return;
+    e.preventDefault();
+    openExternally(url);
+  });
+  // iframe navigations (the WebUI content area and the plugin pages inside it).
+  // The channels plugin renders its server-side login browser (noVNC) in an
+  // iframe on a LOOPBACK port, so loopback MUST stay in-app — blocking it would
+  // break VNC login. Everything non-loopback is external: open the default
+  // browser instead of silently replacing the gateway UI with a third-party page.
+  const isLoopback = (url) => {
+    try {
+      const h = new URL(url).hostname;
+      return h === "127.0.0.1" || h === "localhost" || h === "[::1]";
+    } catch (e) {
+      return false;
+    }
+  };
+  if (mainWindow.webContents.on) {
+    mainWindow.webContents.on("will-frame-navigate", (e) => {
+      if (isInternal(e.url) || isLoopback(e.url)) return;
+      e.preventDefault();
+      openExternally(e.url);
+    });
+  }
   // Silent start: `--silent` CLI flag or settings.silentStart keeps the app
   // in the tray without showing the window (Clash-Verge style). First run
   // always shows the window so the user sees the dashboard.
diff --git a/cmd/gui/package-lock.json b/cmd/gui/package-lock.json
index d6b1a6e..6823784 100644
--- a/cmd/gui/package-lock.json
+++ b/cmd/gui/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "modelrouter-gui",
-  "version": "1.9.3",
+  "version": "2.0.42",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "modelrouter-gui",
-      "version": "1.9.3",
+      "version": "2.0.42",
       "license": "Proprietary",
       "devDependencies": {
         "electron": "^33.0.0",
diff --git a/cmd/gui/package.json b/cmd/gui/package.json
index b972789..e9017e8 100644
--- a/cmd/gui/package.json
+++ b/cmd/gui/package.json
@@ -1,6 +1,6 @@
 {
   "name": "modelrouter-gui",
-  "version": "1.9.7",
+  "version": "2.0.42",
   "description": "ModelRouter Desktop — embedded ModelRouter core with tray",
   "author": "ModelRouter",
   "main": "main.js",
@@ -81,6 +81,7 @@
     },
     "files": [
       "main.js",
+      "plugin-sync.js",
       "preload.js",
       "renderer/**/*",
       "build/**/*",
@@ -89,4 +90,4 @@
     "asar": true
   },
   "homepage": "https://gitcode.com/JianFeeeee/ModelRouter"
-}
+}
\ No newline at end of file
diff --git a/cmd/gui/plugin-sync.js b/cmd/gui/plugin-sync.js
new file mode 100644
index 0000000..c9b2318
--- /dev/null
+++ b/cmd/gui/plugin-sync.js
@@ -0,0 +1,82 @@
+// Plugin-tree maintenance for the embedded core (no Electron imports, so this
+// is unit-testable with plain node).
+//
+// Two problems this solves, both invisible from the gateway side:
+//   1. The core deliberately does NOT default `plugin_dir` (an operator opts
+//      in). A desktop profile without it runs with ZERO plugins — the channels
+//      plugin (account login, credential vault, auto check-in) never appears.
+//   2. The core seeds bundled plugins only when the file is ABSENT, so a
+//      desktop upgrade would keep the user's old channels.lua forever and
+//      silently skip every channel fix. On version change the shell must drop
+//      the built-in files so the new binary reseeds them.
+const fs = require("fs");
+const path = require("path");
+
+const BUILTIN_PLUGINS = ["billing.lua", "channels.lua", "quota.lua", "usage.lua"];
+
+// ensurePluginDirConfigured back-fills `plugin_dir` into an existing config.
+// Appending a top-level YAML key is safe for the shapes this file can have
+// (flat mapping + a keys list). Returns "added" | "present" | "absent" | "error".
+function ensurePluginDirConfigured(configFile, pluginsDir, log) {
+  try {
+    if (!fs.existsSync(configFile)) return "absent";
+    const cur = fs.readFileSync(configFile, "utf-8");
+    if (/^\s*plugin_dir\s*:/m.test(cur)) return "present";
+    fs.writeFileSync(
+      configFile,
+      cur.replace(/\s*$/, "") +
+        "\n# added by ModelRouter Desktop: enables the plugin tree (channels etc.)\n" +
+        "plugin_dir: " + JSON.stringify(pluginsDir) + "\n",
+      "utf-8",
+    );
+    if (log) log("[gui] plugin_dir back-filled into " + configFile);
+    return "added";
+  } catch (e) {
+    if (log) log("[gui] ensurePluginDirConfigured failed: " + e.message);
+    return "error";
+  }
+}
+
+// syncBundledPluginsOnUpgrade drops built-in plugin files when the app version
+// changed, so the core reseeds them from the binary it shipped with. Returns
+// { changed, dropped:[...], kept: "prev-<ver>" }.
+function syncBundledPluginsOnUpgrade(profileDir, pluginsDir, version, log) {
+  const stamp = path.join(profileDir, ".plugin-seed-version");
+  let have = "";
+  try {
+    have = fs.readFileSync(stamp, "utf-8").trim();
+  } catch (e) {
+    /* first run */
+  }
+  if (have === version) return { changed: false, dropped: [] };
+  const dropped = [];
+  for (const name of BUILTIN_PLUGINS) {
+    const f = path.join(pluginsDir, name);
+    if (!fs.existsSync(f)) continue;
+    try {
+      if (have) fs.renameSync(f, f + ".prev-" + have);
+      else fs.unlinkSync(f);
+      dropped.push(name);
+    } catch (e) {
+      if (log) log("[gui] drop builtin plugin " + name + " failed: " + e.message);
+    }
+  }
+  try {
+    fs.writeFileSync(stamp, version + "\n", "utf-8");
+  } catch (e) {
+    if (log) log("[gui] write plugin seed stamp failed: " + e.message);
+  }
+  if (dropped.length && log) {
+    log(
+      "[gui] plugins refreshed for " + version + " (" + dropped.length +
+        " builtin file(s) reseeded by core)",
+    );
+  }
+  return { changed: true, dropped, kept: have ? "prev-" + have : "" };
+}
+
+module.exports = {
+  BUILTIN_PLUGINS,
+  ensurePluginDirConfigured,
+  syncBundledPluginsOnUpgrade,
+};
diff --git a/cmd/gui/plugin-sync.test.js b/cmd/gui/plugin-sync.test.js
new file mode 100644
index 0000000..e3d3c86
--- /dev/null
+++ b/cmd/gui/plugin-sync.test.js
@@ -0,0 +1,80 @@
+// Unit tests for the desktop plugin-tree maintenance (plain node, no Electron).
+// Run: node --test cmd/gui/plugin-sync.test.js
+const test = require("node:test");
+const assert = require("node:assert");
+const fs = require("fs");
+const os = require("os");
+const path = require("path");
+const { BUILTIN_PLUGINS, ensurePluginDirConfigured, syncBundledPluginsOnUpgrade } = require("./plugin-sync");
+
+const tmp = () => fs.mkdtempSync(path.join(os.tmpdir(), "plugin-sync-"));
+
+test("back-fills plugin_dir into an existing profile without it", () => {
+  const dir = tmp();
+  const cfg = path.join(dir, "config.yaml");
+  fs.writeFileSync(cfg, 'listen: 127.0.0.1:8787\ndefault_model: AUTO\nkeys:\n  - key: k\n    role: admin\n');
+  const plugins = path.join(dir, "plugins");
+  assert.equal(ensurePluginDirConfigured(cfg, plugins, null), "added");
+  const out = fs.readFileSync(cfg, "utf-8");
+  assert.match(out, /^plugin_dir: "/m);
+  assert.ok(out.includes(plugins.replace(/\\/g, "\\\\")) || out.includes(plugins), "path written");
+  // the rest of the profile must survive untouched
+  assert.match(out, /^listen: 127\.0\.0\.1:8787$/m);
+  assert.match(out, /^  - key: k$/m);
+});
+
+test("leaves a profile that already sets plugin_dir alone", () => {
+  const dir = tmp();
+  const cfg = path.join(dir, "config.yaml");
+  const orig = 'plugin_dir: "/custom/plugins"\nlisten: ":1"\n';
+  fs.writeFileSync(cfg, orig);
+  assert.equal(ensurePluginDirConfigured(cfg, "/whatever", null), "present");
+  assert.equal(fs.readFileSync(cfg, "utf-8"), orig);
+});
+
+test("missing config is not created by the back-fill", () => {
+  const dir = tmp();
+  const cfg = path.join(dir, "config.yaml");
+  assert.equal(ensurePluginDirConfigured(cfg, path.join(dir, "p"), null), "absent");
+  assert.equal(fs.existsSync(cfg), false);
+});
+
+test("upgrade drops builtin plugins (keeping a backup) but not user plugins", () => {
+  const dir = tmp();
+  const plugins = path.join(dir, "plugins");
+  fs.mkdirSync(plugins, { recursive: true });
+  for (const f of BUILTIN_PLUGINS) fs.writeFileSync(path.join(plugins, f), "OLD");
+  fs.writeFileSync(path.join(plugins, "my-own.lua"), "MINE");
+  fs.writeFileSync(path.join(dir, ".plugin-seed-version"), "1.0.0\n");
+
+  const r = syncBundledPluginsOnUpgrade(dir, plugins, "2.0.42", null);
+  assert.equal(r.changed, true);
+  assert.deepEqual(r.dropped.sort(), [...BUILTIN_PLUGINS].sort());
+  for (const f of BUILTIN_PLUGINS) {
+    assert.equal(fs.existsSync(path.join(plugins, f)), false, f + " dropped");
+    assert.equal(fs.readFileSync(path.join(plugins, f + ".prev-1.0.0"), "utf-8"), "OLD");
+  }
+  assert.equal(fs.readFileSync(path.join(plugins, "my-own.lua"), "utf-8"), "MINE");
+  assert.equal(fs.readFileSync(path.join(dir, ".plugin-seed-version"), "utf-8").trim(), "2.0.42");
+});
+
+test("same version is a no-op (nothing dropped)", () => {
+  const dir = tmp();
+  const plugins = path.join(dir, "plugins");
+  fs.mkdirSync(plugins, { recursive: true });
+  fs.writeFileSync(path.join(plugins, "channels.lua"), "CURRENT");
+  fs.writeFileSync(path.join(dir, ".plugin-seed-version"), "2.0.42\n");
+  const r = syncBundledPluginsOnUpgrade(dir, plugins, "2.0.42", null);
+  assert.equal(r.changed, false);
+  assert.equal(fs.readFileSync(path.join(plugins, "channels.lua"), "utf-8"), "CURRENT");
+});
+
+test("first run on a fresh profile just stamps the version", () => {
+  const dir = tmp();
+  const plugins = path.join(dir, "plugins");
+  fs.mkdirSync(plugins, { recursive: true });
+  const r = syncBundledPluginsOnUpgrade(dir, plugins, "2.0.42", null);
+  assert.equal(r.changed, true);
+  assert.deepEqual(r.dropped, []);
+  assert.equal(fs.existsSync(path.join(dir, ".plugin-seed-version")), true);
+});