diff --git a/app/src/components/BootCheckGate/BootCheckGate.tsx b/app/src/components/BootCheckGate/BootCheckGate.tsx
index 4f2eebc05..e1d62e34d 100644
--- a/app/src/components/BootCheckGate/BootCheckGate.tsx
+++ b/app/src/components/BootCheckGate/BootCheckGate.tsx
@@ -9,7 +9,6 @@
  * Visual language follows ServiceBlockingGate.tsx (bg-stone-950/80 overlay,
  * bg-stone-900 panel, ocean-500 / coral-500 semantics).
  */
-import { isTauri } from '@tauri-apps/api/core';
 import debug from 'debug';
 import { useCallback, useEffect, useRef, useState } from 'react';
 
@@ -29,6 +28,7 @@ import {
   storeCoreToken,
   storeRpcUrl,
 } from '../../utils/configPersistence';
+import { isTauri } from '../../utils/tauriCommands/common';
 
 const log = debug('boot-check');
 const logError = debug('boot-check:error');
diff --git a/app/src/components/settings/panels/DeveloperOptionsPanel.tsx b/app/src/components/settings/panels/DeveloperOptionsPanel.tsx
index 983f475e0..1de97f75b 100644
--- a/app/src/components/settings/panels/DeveloperOptionsPanel.tsx
+++ b/app/src/components/settings/panels/DeveloperOptionsPanel.tsx
@@ -1,9 +1,10 @@
-import { invoke, isTauri } from '@tauri-apps/api/core';
+import { invoke } from '@tauri-apps/api/core';
 import { useEffect, useState } from 'react';
 
 import { triggerSentryTestEvent } from '../../../services/analytics';
 import { useAppSelector } from '../../../store/hooks';
 import { APP_ENVIRONMENT } from '../../../utils/config';
+import { isTauri } from '../../../utils/tauriCommands/common';
 import SettingsHeader from '../components/SettingsHeader';
 import SettingsMenuItem from '../components/SettingsMenuItem';
 import { useSettingsNavigation } from '../hooks/useSettingsNavigation';
diff --git a/app/src/lib/nativeNotifications/tauriBridge.ts b/app/src/lib/nativeNotifications/tauriBridge.ts
index 8bd201d17..266dbb2d7 100644
--- a/app/src/lib/nativeNotifications/tauriBridge.ts
+++ b/app/src/lib/nativeNotifications/tauriBridge.ts
@@ -1,6 +1,8 @@
-import { invoke, isTauri } from '@tauri-apps/api/core';
+import { invoke } from '@tauri-apps/api/core';
 import debug from 'debug';
 
+import { isTauri } from '../../utils/tauriCommands/common';
+
 const log = debug('native-notifications:bridge');
 const errLog = debug('native-notifications:bridge:error');
 
diff --git a/app/src/lib/webviewNotifications/service.ts b/app/src/lib/webviewNotifications/service.ts
index 98b69913b..21ffe3b02 100644
--- a/app/src/lib/webviewNotifications/service.ts
+++ b/app/src/lib/webviewNotifications/service.ts
@@ -1,4 +1,3 @@
-import { isTauri } from '@tauri-apps/api/core';
 import { listen, type UnlistenFn } from '@tauri-apps/api/event';
 import debug from 'debug';
 
@@ -9,6 +8,7 @@ import {
   noteWebviewNotificationFired,
 } from '../../store/accountsSlice';
 import { addIntegrationNotification } from '../../store/notificationSlice';
+import { isTauri } from '../../utils/tauriCommands/common';
 import { WEBVIEW_NOTIFICATION_FIRED_EVENT, type WebviewNotificationFired } from './types';
 
 const log = debug('webview-notifications');
diff --git a/app/src/main.tsx b/app/src/main.tsx
index 51472bdd1..5b6d986e0 100644
--- a/app/src/main.tsx
+++ b/app/src/main.tsx
@@ -1,5 +1,4 @@
 // IMPORTANT: Polyfills must be imported FIRST
-import { isTauri as tauriRuntimeAvailable } from '@tauri-apps/api/core';
 import { getCurrentWindow } from '@tauri-apps/api/window';
 import React from 'react';
 import ReactDOM from 'react-dom/client';
@@ -16,6 +15,7 @@ import { primeActiveUserId } from './store/userScopedStorage';
 import { APP_VERSION } from './utils/config';
 import { setupDesktopDeepLinkListener } from './utils/desktopDeepLinkListener';
 import { getActiveUserIdFromCore } from './utils/tauriCommands';
+import { isTauri as tauriRuntimeAvailable } from './utils/tauriCommands/common';
 
 setStoreForApiClient(() => getCoreStateSnapshot().snapshot.sessionToken);
 
@@ -23,7 +23,10 @@ setStoreForApiClient(() => getCoreStateSnapshot().snapshot.sessionToken);
 // that lives OUTSIDE Tauri's runtime (the vendored tauri-cef can't render
 // transparent windowed-mode browsers). That webview can't read a Tauri
 // window label, so the Rust shell appends `?window=mascot` to the URL it
-// loads. Detect it before we touch any Tauri APIs.
+// loads. Detect it via the URL param so we can skip `getCurrentWindow()`
+// — which would either throw or trigger the CEF IPC-bootstrap gap that
+// `tauriRuntimeAvailable()` (= the hardened `isTauri()`) now guards
+// against by reading `window.__TAURI_INTERNALS__.invoke`.
 const urlWindowParam = (() => {
   try {
     return new URLSearchParams(window.location.search).get('window');
diff --git a/app/src/services/backendUrl.ts b/app/src/services/backendUrl.ts
index c17084aed..61f75c336 100644
--- a/app/src/services/backendUrl.ts
+++ b/app/src/services/backendUrl.ts
@@ -1,6 +1,5 @@
-import { isTauri as coreIsTauri } from '@tauri-apps/api/core';
-
 import { BACKEND_URL } from '../utils/config';
+import { isTauri as coreIsTauri } from '../utils/tauriCommands/common';
 import { callCoreRpc } from './coreRpcClient';
 
 let resolvedBackendUrl: string | null = null;
diff --git a/app/src/services/coreRpcClient.ts b/app/src/services/coreRpcClient.ts
index 0a27afe23..2e4ae79c3 100644
--- a/app/src/services/coreRpcClient.ts
+++ b/app/src/services/coreRpcClient.ts
@@ -1,10 +1,11 @@
-import { isTauri as coreIsTauri, invoke } from '@tauri-apps/api/core';
+import { invoke } from '@tauri-apps/api/core';
 import debug from 'debug';
 
 import { dispatchLocalAiMethod } from '../lib/ai/localCoreAiMemory';
 import { CORE_RPC_TIMEOUT_MS, CORE_RPC_URL } from '../utils/config';
 import { getStoredCoreToken, peekStoredRpcUrl } from '../utils/configPersistence';
 import { sanitizeError } from '../utils/sanitize';
+import { isTauri as coreIsTauri } from '../utils/tauriCommands/common';
 import { normalizeRpcMethod } from './rpcMethods';
 
 interface CoreRpcRelayRequest {
diff --git a/app/src/services/meetCallService.ts b/app/src/services/meetCallService.ts
index 1e9a2bcf0..69c0883ee 100644
--- a/app/src/services/meetCallService.ts
+++ b/app/src/services/meetCallService.ts
@@ -9,8 +9,9 @@
 //
 // Splitting it this way keeps platform-specific window code in the shell
 // while the validation rules live (and are tested) in the core.
-import { invoke, isTauri } from '@tauri-apps/api/core';
+import { invoke } from '@tauri-apps/api/core';
 
+import { isTauri } from '../utils/tauriCommands/common';
 import { callCoreRpc } from './coreRpcClient';
 
 export type MeetJoinCallInput = { meetUrl: string; displayName: string };
diff --git a/app/src/services/webviewAccountService.ts b/app/src/services/webviewAccountService.ts
index d4a6f24bd..0cb834559 100644
--- a/app/src/services/webviewAccountService.ts
+++ b/app/src/services/webviewAccountService.ts
@@ -1,5 +1,5 @@
 import * as Sentry from '@sentry/react';
-import { invoke, isTauri } from '@tauri-apps/api/core';
+import { invoke } from '@tauri-apps/api/core';
 import { listen, type UnlistenFn } from '@tauri-apps/api/event';
 import debug from 'debug';
 
@@ -13,6 +13,7 @@ import {
 import { addIntegrationNotification } from '../store/notificationSlice';
 import { fetchRespondQueue } from '../store/providerSurfaceSlice';
 import type { AccountProvider, IngestedMessage } from '../types/accounts';
+import { isTauri } from '../utils/tauriCommands/common';
 import { openhumanGetMeetSettings } from '../utils/tauriCommands/config';
 import { trackEvent } from './analytics';
 import { threadApi } from './api/threadApi';
@@ -25,6 +26,10 @@ const MEET_ORCHESTRATOR_MODEL = 'reasoning-v1';
 const log = debug('webview-accounts');
 const errLog = debug('webview-accounts:error');
 
+// Re-export the canonical Tauri guard so existing imports
+// `import { isTauri } from '.../webviewAccountService'` keep working.
+// The implementation lives in `utils/tauriCommands/common.ts` and accounts
+// for the CEF IPC injection race (see comment there).
 export { isTauri };
 
 /**
diff --git a/app/src/test/setup.ts b/app/src/test/setup.ts
index 11741f527..758fcc159 100644
--- a/app/src/test/setup.ts
+++ b/app/src/test/setup.ts
@@ -98,6 +98,17 @@ if (typeof Element !== 'undefined' && !Element.prototype.scrollIntoView) {
   Element.prototype.scrollIntoView = function () {};
 }
 
+// The hardened `isTauri()` (in `utils/tauriCommands/common.ts`) checks both
+// `coreIsTauri()` and `window.__TAURI_INTERNALS__.invoke`. Many existing test
+// files mock `@tauri-apps/api/core::isTauri` to `true` to exercise the
+// Tauri branch; without a matching IPC handle on `window` they would now
+// regress to the non-Tauri path. Seed a no-op handle once globally so the
+// IPC-readiness check passes by default. Tests that *want* the CEF gap
+// behaviour can `delete window.__TAURI_INTERNALS__` in a `beforeEach`.
+(
+  window as unknown as { __TAURI_INTERNALS__: { invoke: () => Promise<unknown> } }
+).__TAURI_INTERNALS__ = { invoke: vi.fn(() => Promise.resolve()) };
+
 // Mock Tauri APIs (not available in test env)
 vi.mock('@tauri-apps/api/core', () => ({ invoke: vi.fn(), isTauri: vi.fn(() => false) }));
 
@@ -223,6 +234,13 @@ if (!process.env.DEBUG_TESTS) {
 afterEach(() => {
   clearRequestLog();
   cleanup();
+  // Re-seed the IPC handle after any test that may have deleted it
+  // (e.g. tests exercising the CEF-gap branch of `isTauri()`). Without
+  // this, sibling tests in the same jsdom worker would silently regress
+  // to the non-Tauri path. Per graycyrus review on PR #1556.
+  (
+    window as unknown as { __TAURI_INTERNALS__: { invoke: () => Promise<unknown> } }
+  ).__TAURI_INTERNALS__ = { invoke: vi.fn(() => Promise.resolve()) };
 });
 afterAll(async () => {
   await stopMockServer();
diff --git a/app/src/utils/desktopDeepLinkListener.ts b/app/src/utils/desktopDeepLinkListener.ts
index 3a17c7e7c..443732f7b 100644
--- a/app/src/utils/desktopDeepLinkListener.ts
+++ b/app/src/utils/desktopDeepLinkListener.ts
@@ -1,5 +1,4 @@
 import * as Sentry from '@sentry/react';
-import { isTauri as coreIsTauri } from '@tauri-apps/api/core';
 import { getCurrentWindow } from '@tauri-apps/api/window';
 import { getCurrent, onOpenUrl } from '@tauri-apps/plugin-deep-link';
 
@@ -14,6 +13,7 @@ import { BILLING_DASHBOARD_URL } from './links';
 import { evaluateOAuthAppVersionGate } from './oauthAppVersionGate';
 import { openUrl } from './openUrl';
 import { storeSession } from './tauriCommands';
+import { isTauri as coreIsTauri } from './tauriCommands/common';
 
 const SESSION_TOKEN_UPDATED_EVENT = 'core-state:session-token-updated';
 
diff --git a/app/src/utils/oauthAppVersionGate.ts b/app/src/utils/oauthAppVersionGate.ts
index c5c1d9b52..dff36d7c5 100644
--- a/app/src/utils/oauthAppVersionGate.ts
+++ b/app/src/utils/oauthAppVersionGate.ts
@@ -1,8 +1,8 @@
 import { getVersion } from '@tauri-apps/api/app';
-import { isTauri } from '@tauri-apps/api/core';
 
 import { LATEST_APP_DOWNLOAD_URL, MINIMUM_SUPPORTED_APP_VERSION } from './config';
 import { isVersionAtLeast, parseSemverParts } from './semver';
+import { isTauri } from './tauriCommands/common';
 
 export type OAuthAppVersionGateResult =
   | { ok: true }
diff --git a/app/src/utils/openUrl.test.ts b/app/src/utils/openUrl.test.ts
index 0cd927eb5..a071b7a2b 100644
--- a/app/src/utils/openUrl.test.ts
+++ b/app/src/utils/openUrl.test.ts
@@ -11,7 +11,7 @@ const isTauriMock = vi.fn();
 const tauriOpenUrlMock = vi.fn();
 const addBreadcrumbMock = vi.fn();
 
-vi.mock('@tauri-apps/api/core', () => ({ isTauri: () => isTauriMock() }));
+vi.mock('./tauriCommands/common', () => ({ isTauri: () => isTauriMock() }));
 
 vi.mock('@tauri-apps/plugin-opener', () => ({ openUrl: (url: string) => tauriOpenUrlMock(url) }));
 
diff --git a/app/src/utils/openUrl.ts b/app/src/utils/openUrl.ts
index 286d97c8f..04541f082 100644
--- a/app/src/utils/openUrl.ts
+++ b/app/src/utils/openUrl.ts
@@ -1,7 +1,8 @@
 import * as Sentry from '@sentry/react';
-import { isTauri } from '@tauri-apps/api/core';
 import { openUrl as tauriOpenUrl } from '@tauri-apps/plugin-opener';
 
+import { isTauri } from './tauriCommands/common';
+
 const isHttpUrl = (url: string): boolean => /^https?:\/\//i.test(url);
 
 /**
diff --git a/app/src/utils/tauriCommands/common.test.ts b/app/src/utils/tauriCommands/common.test.ts
new file mode 100644
index 000000000..f339a2d0b
--- /dev/null
+++ b/app/src/utils/tauriCommands/common.test.ts
@@ -0,0 +1,92 @@
+/**
+ * Unit tests for `isTauri()` — the canonical Tauri-runtime guard used across
+ * `app/src/`. Beyond delegating to `@tauri-apps/api/core::isTauri()`, this
+ * wrapper also confirms that the IPC transport (`window.__TAURI_INTERNALS__
+ * .invoke`) is wired before reporting `true`.
+ *
+ * Why it matters: under CEF, `globalThis.isTauri` (which the underlying
+ * `coreIsTauri()` checks) is injected by the webview bootstrap BEFORE the
+ * `postMessage` IPC bridge is connected. An `invoke()` landing in that gap
+ * throws `TypeError: Cannot read properties of undefined (reading
+ * 'postMessage')` deep inside Tauri's `sendIpcMessage`, which surfaces as
+ * the OPENHUMAN-REACT-S Sentry issue (#1472 follow-up). All call sites that
+ * gate on `isTauri()` should now route through the non-Tauri branch during
+ * the gap instead of bursting into IPC.
+ */
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+
+import { isTauri } from './common';
+
+const coreIsTauriMock = vi.fn();
+
+vi.mock('@tauri-apps/api/core', () => ({ isTauri: () => coreIsTauriMock() }));
+
+describe('isTauri (tauriCommands/common)', () => {
+  // We mutate `window` to simulate Tauri-runtime bootstrap state across cases.
+  // Stash + restore so other tests in the suite (which share the jsdom global)
+  // see a pristine window.
+  let originalInternals: unknown;
+
+  beforeEach(() => {
+    coreIsTauriMock.mockReset();
+    originalInternals = (window as unknown as { __TAURI_INTERNALS__?: unknown })
+      .__TAURI_INTERNALS__;
+  });
+
+  afterEach(() => {
+    if (originalInternals === undefined) {
+      delete (window as unknown as { __TAURI_INTERNALS__?: unknown }).__TAURI_INTERNALS__;
+    } else {
+      (window as unknown as { __TAURI_INTERNALS__?: unknown }).__TAURI_INTERNALS__ =
+        originalInternals;
+    }
+  });
+
+  it('returns false when not running in Tauri at all (browser/Vitest)', () => {
+    coreIsTauriMock.mockReturnValue(false);
+    delete (window as unknown as { __TAURI_INTERNALS__?: unknown }).__TAURI_INTERNALS__;
+
+    expect(isTauri()).toBe(false);
+  });
+
+  it('returns true when both the runtime flag and the IPC `invoke` handle are present', () => {
+    coreIsTauriMock.mockReturnValue(true);
+    (window as unknown as { __TAURI_INTERNALS__?: { invoke: unknown } }).__TAURI_INTERNALS__ = {
+      invoke: () => Promise.resolve(),
+    };
+
+    expect(isTauri()).toBe(true);
+  });
+
+  // The OPENHUMAN-REACT-S regression: Tauri sets `globalThis.isTauri = true`
+  // (so the official check returns true) before CEF wires the IPC postMessage
+  // bridge. During that gap any unguarded `invoke(...)` blows up inside
+  // `sendIpcMessage` with the "Cannot read properties of undefined (reading
+  // 'postMessage')" TypeError. Our guard must short-circuit to `false` so
+  // call sites skip the IPC path instead of trusting the runtime flag alone.
+  it('returns false during the CEF gap when runtime flag is set but __TAURI_INTERNALS__ is missing', () => {
+    coreIsTauriMock.mockReturnValue(true);
+    delete (window as unknown as { __TAURI_INTERNALS__?: unknown }).__TAURI_INTERNALS__;
+
+    expect(isTauri()).toBe(false);
+  });
+
+  it('returns false during the partial-bootstrap gap when __TAURI_INTERNALS__ exists but `invoke` is not yet wired', () => {
+    coreIsTauriMock.mockReturnValue(true);
+    // Some CEF bootstrap stages set the object literal before the IPC handle
+    // is attached. Treat that as "not ready".
+    (window as unknown as { __TAURI_INTERNALS__?: Record<string, unknown> }).__TAURI_INTERNALS__ =
+      {};
+
+    expect(isTauri()).toBe(false);
+  });
+
+  it('returns false when __TAURI_INTERNALS__.invoke is present but not a function', () => {
+    coreIsTauriMock.mockReturnValue(true);
+    (window as unknown as { __TAURI_INTERNALS__?: { invoke: unknown } }).__TAURI_INTERNALS__ = {
+      invoke: 'not-a-function',
+    };
+
+    expect(isTauri()).toBe(false);
+  });
+});
diff --git a/app/src/utils/tauriCommands/common.ts b/app/src/utils/tauriCommands/common.ts
index 0572c2739..6115af3d4 100644
--- a/app/src/utils/tauriCommands/common.ts
+++ b/app/src/utils/tauriCommands/common.ts
@@ -2,11 +2,41 @@
  * Common utilities and types for Tauri Commands.
  */
 import { isTauri as coreIsTauri } from '@tauri-apps/api/core';
+import debug from 'debug';
 
-// Check if we're running in Tauri
+const log = debug('tauri:ipc-guard');
+
+/**
+ * True when the Tauri runtime is present AND the underlying IPC transport is
+ * wired. The official `coreIsTauri()` check (which reads `globalThis.isTauri`)
+ * is set early by Tauri's webview bootstrap, but on CEF `__TAURI_INTERNALS__`
+ * (and the `postMessage` bridge it dispatches through) is injected *after*
+ * `on_after_created` fires. An `invoke()` landing in that gap throws
+ * `TypeError: Cannot read properties of undefined (reading 'postMessage')`
+ * deep inside Tauri's `sendIpcMessage` — see OPENHUMAN-REACT-S / #1472.
+ *
+ * Callers that gate on `isTauri()` BEFORE invoking should therefore use this
+ * function; it returns `false` during the bootstrap gap so the call site
+ * takes the non-Tauri branch (skip / fallback) instead of synchronously
+ * throwing into a `new Promise` body where the rejection escapes the local
+ * try/catch and lands as an unhandled Sentry event.
+ */
 export const isTauri = (): boolean => {
-  // Tauri v2: prefer the official runtime check over window globals.
-  return coreIsTauri();
+  if (!coreIsTauri()) return false;
+  if (typeof window === 'undefined') return false;
+  // Narrow `window` access through a single optional chain so the check is
+  // resilient to either `__TAURI_INTERNALS__` being absent or `.invoke`
+  // being missing while the rest of the object is partially populated.
+  const internals = (window as unknown as { __TAURI_INTERNALS__?: { invoke?: unknown } })
+    .__TAURI_INTERNALS__;
+  if (typeof internals?.invoke !== 'function') {
+    // Bridge-missing branch: distinct from `!coreIsTauri()` (= not in Tauri
+    // at all). Logging here makes the CEF bootstrap gap observable in dev
+    // and is a no-op in production (debug namespace disabled by default).
+    log('isTauri() -> false: IPC bridge not wired (CEF bootstrap gap or non-Tauri)');
+    return false;
+  }
+  return true;
 };
 
 export interface CommandResponse<T> {