diff --git a/.changeset/web-binding-cookie-only.md b/.changeset/web-binding-cookie-only.md
new file mode 100644
index 0000000..31db541
--- /dev/null
+++ b/.changeset/web-binding-cookie-only.md
@@ -0,0 +1,5 @@
+---
+'@seamless-auth/react': minor
+---
+
+`AuthProvider` is cookie transport only. Its `transport` prop no longer accepts `mode` or `tokenStorage`, and passing `mode: 'bearer'` throws, so in a browser the tokens stay with the server adapter in `httpOnly` cookies and a script on the page can never read them. `basePath`, `fetch` and `trustedOrigins` are unchanged. Native apps that need bearer transport use `@seamless-auth/react-native`, which is unaffected. No first-party template, the admin console or RoxTarget used bearer mode from `@seamless-auth/react`.
diff --git a/packages/react/README.md b/packages/react/README.md
index c0afaf9..b1e896c 100644
--- a/packages/react/README.md
+++ b/packages/react/README.md
@@ -318,25 +318,24 @@ Custom UIs get the same default through `useAuthClient()`, and can still overrid
 
 Everything that differs between a browser and another platform sits behind a port on
 `AuthProvider`. A web application configures nothing; the browser implementations are the
-defaults. A binding for another platform (React Native is the first) supplies its own:
+defaults. A port can be swapped, for example to drive the passkey ceremonies yourself:
 
 ```tsx
 <AuthProvider
   apiHost={apiHost}
-  transport={{ mode: 'bearer', tokenStorage: keystoreTokenStorage }}
-  ports={{ passkeys: nativePasskeys, oauthRedirect: inAppBrowserRedirect }}
+  transport={{ basePath: '/identity', trustedOrigins: ['https://data.example.com'] }}
+  ports={{ passkeys: customPasskeys }}
 >
   <App />
 </AuthProvider>
 ```
 
-- `transport` selects how the session travels. Cookie transport, the default, is the browser
-  contract: the server adapter holds the tokens in `httpOnly` cookies and the client never sees
-  them. Bearer transport is the native contract: the client holds the auth API's own tokens,
-  presents the one a route needs in `Authorization`, stores the pair a sign-in returns through
-  `tokenStorage`, and refreshes once through `POST /auth/refresh` when a request answers 401. At
-  most one refresh is in flight at a time, because the auth API treats a replayed refresh token as
-  theft and revokes the chain.
+- `transport` sets where the adapter is mounted (`basePath`, default `/auth`), the `fetch` to use,
+  and the extra origins `authorizedFetch` may reach (`trustedOrigins`). It is always cookie
+  transport: the server adapter holds the tokens in `httpOnly` cookies and the browser never sees
+  them, so a script on the page can ride the session but not read it. Passing `mode: 'bearer'`
+  throws. Native apps that need bearer transport, where the client holds the tokens in a keystore,
+  use `@seamless-auth/react-native`.
 - `ports.passkeys` runs the WebAuthn ceremonies (`create`, `get`, and the two support checks).
   `usePasskeySupport()` and every passkey flow go through it.
 - `ports.oauthRedirect` opens the provider. The browser navigates away and the callback route
diff --git a/packages/react/src/AuthProvider.tsx b/packages/react/src/AuthProvider.tsx
index eb2c19e..19947cb 100644
--- a/packages/react/src/AuthProvider.tsx
+++ b/packages/react/src/AuthProvider.tsx
@@ -130,10 +130,13 @@ interface AuthProviderProps {
    */
   magicLinkRedirectUri?: string;
   /**
-   * How the session travels to the server adapter. Defaults to cookie
-   * transport, which is what a browser application wants.
+   * Where the adapter is mounted, the fetch to use, and the extra origins
+   * `authorizedFetch` may reach. Always cookie transport: the server adapter
+   * holds the tokens and the browser only HttpOnly cookies, so a script on the
+   * page can ride the session but never read it. Bearer transport is for
+   * native apps, through `@seamless-auth/react-native`.
    */
-  transport?: Omit<TransportOptions, 'apiHost'>;
+  transport?: Omit<TransportOptions, 'apiHost' | 'mode' | 'tokenStorage'>;
   /** Platform ports. Each one left out falls back to the browser's. */
   ports?: Partial<AuthPorts>;
   /**
@@ -166,22 +169,24 @@ export const AuthProvider: React.FC<AuthProviderProps> = ({
     [providedPorts?.passkeys, providedPorts?.oauthRedirect]
   );
 
-  const {
-    mode,
-    basePath,
-    tokenStorage,
-    fetch: fetchImpl,
-    trustedOrigins,
-  } = transport ?? {};
+  // The type no longer offers bearer, but a JavaScript caller can still pass it,
+  // and quietly switching it to cookies would hide that their tokens were never
+  // where they thought.
+  if ((transport as { mode?: unknown } | undefined)?.mode === 'bearer') {
+    throw new TypeError(
+      '@seamless-auth/react is cookie transport only, so the browser never holds the tokens. Use @seamless-auth/react-native for bearer transport in a native app.'
+    );
+  }
+
+  const { basePath, fetch: fetchImpl, trustedOrigins } = transport ?? {};
   // An inline array is a new value on every render, so it is compared by content.
   const trustedOriginsKey = trustedOrigins ? JSON.stringify(trustedOrigins) : undefined;
   const stableTransport = useMemo(
     () =>
       transport
         ? {
-            mode,
+            mode: 'cookie' as const,
             basePath,
-            tokenStorage,
             fetch: fetchImpl,
             trustedOrigins: trustedOriginsKey
               ? (JSON.parse(trustedOriginsKey) as string[])
@@ -189,7 +194,7 @@ export const AuthProvider: React.FC<AuthProviderProps> = ({
           }
         : undefined,
     // eslint-disable-next-line react-hooks/exhaustive-deps -- `transport` itself is deliberately not a dependency
-    [mode, basePath, tokenStorage, fetchImpl, trustedOriginsKey]
+    [basePath, fetchImpl, trustedOriginsKey]
   );
 
   // Seeds the store like a `useState` initialiser. A server component hands over
diff --git a/packages/react/tests/authProvider.test.tsx b/packages/react/tests/authProvider.test.tsx
index 2c2c75f..2a60213 100644
--- a/packages/react/tests/authProvider.test.tsx
+++ b/packages/react/tests/authProvider.test.tsx
@@ -511,13 +511,8 @@ describe('AuthProvider', () => {
       expect(typeof (seen[0] as { login: unknown }).login).toBe('function');
     });
 
-    it('passes transport and passkey ports through to the client', async () => {
+    it('passes transport options and passkey ports through to the client, as cookie transport', async () => {
       mockFetchWithAuthImpl.mockResolvedValue(signedIn());
-      const tokenStorage = {
-        get: jest.fn(async () => null),
-        set: jest.fn(async () => undefined),
-        remove: jest.fn(async () => undefined),
-      };
       const passkeys = {
         isSupported: () => true,
         isPlatformAuthenticatorAvailable: async () => true,
@@ -535,7 +530,7 @@ describe('AuthProvider', () => {
         render(
           <AuthProvider
             apiHost={apiHost}
-            transport={{ mode: 'bearer', tokenStorage }}
+            transport={{ basePath: '/identity' }}
             ports={{ passkeys }}
           >
             <Probe />
@@ -544,18 +539,39 @@ describe('AuthProvider', () => {
       });
 
       expect(createFetchTransport).toHaveBeenCalledWith(
-        expect.objectContaining({ authHost: apiHost, mode: 'bearer', tokenStorage })
+        expect.objectContaining({
+          authHost: apiHost,
+          mode: 'cookie',
+          basePath: '/identity',
+        })
+      );
+      expect(createFetchTransport).not.toHaveBeenCalledWith(
+        expect.objectContaining({ tokenStorage: expect.anything() })
       );
       expect((ports as { passkeys: unknown }).passkeys).toBe(passkeys);
     });
 
+    // The browser binding keeps tokens out of page script. A JavaScript caller
+    // can still pass bearer, and quietly using cookies instead would hide that.
+    it('refuses bearer transport', () => {
+      const spy = jest.spyOn(console, 'error').mockImplementation(() => undefined);
+
+      expect(() =>
+        render(
+          <AuthProvider
+            apiHost={apiHost}
+            transport={{ mode: 'bearer' } as unknown as { basePath?: string }}
+          >
+            <Consumer />
+          </AuthProvider>
+        )
+      ).toThrow(/cookie transport only/);
+
+      spy.mockRestore();
+    });
+
     it('keeps one session across re-renders that pass fresh but equal prop objects', async () => {
       mockFetchWithAuthImpl.mockResolvedValue(signedIn());
-      const tokenStorage = {
-        get: jest.fn(async () => null),
-        set: jest.fn(async () => undefined),
-        remove: jest.fn(async () => undefined),
-      };
       const passkeys = {
         isSupported: () => true,
         isPlatformAuthenticatorAvailable: async () => true,
@@ -567,8 +583,6 @@ describe('AuthProvider', () => {
         <AuthProvider
           apiHost={apiHost}
           transport={{
-            mode: 'bearer',
-            tokenStorage,
             trustedOrigins: ['https://data.example.com'],
           }}
           ports={{ passkeys }}
diff --git a/scripts/check-react-dist.mjs b/scripts/check-react-dist.mjs
index 7b530b7..ccaad3b 100644
--- a/scripts/check-react-dist.mjs
+++ b/scripts/check-react-dist.mjs
@@ -45,6 +45,13 @@ for (const file of await emittedModules(dist)) {
   }
 }
 
+for (const file of await emittedModules(dist)) {
+  // The browser binding is cookie transport only; bearer belongs to react-native.
+  if (/mode:\s*["']bearer["']/.test(await readFile(file, 'utf8'))) {
+    failures.push(`${path.relative(dist, file)} configures bearer transport`);
+  }
+}
+
 const reachableFromIndex = await staticImports(path.join(dist, 'index.js'));
 if (reachableFromIndex.has('react-router-dom')) {
   failures.push(