diff --git a/frontend/src/lib/demo.ts b/frontend/src/lib/demo.ts
index 09edbff85..a73bc34e3 100644
--- a/frontend/src/lib/demo.ts
+++ b/frontend/src/lib/demo.ts
@@ -464,6 +464,19 @@ export function createDemoClient(): ParseableClient {
     const missing = names.filter((name) => !Object.hasOwn(roles, name));
     if (missing.length) fail(`Roles do not exist: ${missing.join(', ')}`);
   }
+  // Demo roles can only hold admin, editor, reader, writer or ingestor, so
+  // the built-in `super-admin` is the only protected role.
+  function rejectProtectedRoles(names: string[]) {
+    if (names.includes('super-admin')) fail('Role is protected');
+  }
+  // Like the backend, role additions report protected roles before unknown
+  // ones, and API keys and user creation the other way round. `super-admin`
+  // exists on the backend but not in the demo's role map.
+  function assignableRoles(names: string[], { protectedFirst = false } = {}) {
+    if (protectedFirst) rejectProtectedRoles(names);
+    knownRoles(names.filter((name) => name !== 'super-admin'));
+    rejectProtectedRoles(names);
+  }
   function named(name: string, kind: 'user' | 'role') {
     const error = validateName(name, kind);
     if (error) fail(error);
@@ -613,7 +626,7 @@ export function createDemoClient(): ParseableClient {
       await ready();
       if (username === 'admin') fail('Cannot call this API for root admin user');
       named(username, 'user');
-      knownRoles(assigned);
+      assignableRoles(assigned);
       if (!assigned.length) fail('User cannot be created without a role');
       if (
         users.some(
@@ -641,7 +654,7 @@ export function createDemoClient(): ParseableClient {
     async addUserRoles(id, assigned) {
       await ready();
       const user = findUser(id, true);
-      knownRoles(assigned);
+      assignableRoles(assigned, { protectedFirst: true });
       if (user.oidc && !user.oidc.legacy)
         user.oidc.manualRoles = [...new Set([...(user.oidc.manualRoles ?? []), ...assigned])];
       else user.assigned = [...new Set([...user.assigned, ...assigned])];
@@ -678,7 +691,7 @@ export function createDemoClient(): ParseableClient {
     },
     async createApiKey(keyName, assigned, ttlSeconds) {
       await ready();
-      knownRoles(assigned);
+      assignableRoles(assigned);
       if (
         ttlSeconds != null &&
         (!Number.isInteger(ttlSeconds) || ttlSeconds < 1800 || ttlSeconds > 7776000)
diff --git a/frontend/src/lib/demoTeam.test.ts b/frontend/src/lib/demoTeam.test.ts
index e6478b595..5bdb0165e 100644
--- a/frontend/src/lib/demoTeam.test.ts
+++ b/frontend/src/lib/demoTeam.test.ts
@@ -95,6 +95,79 @@ describe('per-client Team demo', () => {
     }
     expect(await client.listUsers()).toEqual(users);
   });
+  describe.each([
+    { assigned: ['super-admin'] },
+    { assigned: ['analysts', 'super-admin'] },
+    { assigned: ['super-admin', 'analysts'] },
+  ])('protected role grants: $assigned', ({ assigned }) => {
+    it('rejects API-key creation without changing the key inventory', async () => {
+      const client = createDemoClient();
+      const keys = await client.listApiKeys();
+      await expect(client.createApiKey('protected-key', assigned)).rejects.toMatchObject({
+        status: 400,
+        message: 'Role is protected',
+      });
+      expect(await client.listApiKeys()).toEqual(keys);
+    });
+    it('rejects user creation without changing users', async () => {
+      const client = createDemoClient();
+      const users = await client.listUsers();
+      await expect(client.createUser('protected-user', assigned)).rejects.toMatchObject({
+        status: 400,
+        message: 'Role is protected',
+      });
+      expect(await client.listUsers()).toEqual(users);
+    });
+    it.each(['analyst', 'https://issuer.example/sso-user'])(
+      'rejects role additions to %s without changing role sources',
+      async (id) => {
+        const client = createDemoClient();
+        const sources = await client.userRoleSources(id);
+        await expect(client.addUserRoles(id, assigned)).rejects.toMatchObject({
+          status: 400,
+          message: 'Role is protected',
+        });
+        expect(await client.userRoleSources(id)).toEqual(sources);
+      },
+    );
+  });
+  it.each(['constructor', 'toString', '__proto__'])(
+    'rejects the inherited property name %s as an unknown role',
+    async (name) => {
+      const client = createDemoClient();
+      const unknown = { status: 400, message: `Roles do not exist: ${name}` };
+      await expect(client.createApiKey('inherited-key', [name])).rejects.toMatchObject(unknown);
+      await expect(client.createUser('inherited-user', [name])).rejects.toMatchObject(unknown);
+      await expect(client.addUserRoles('analyst', [name])).rejects.toMatchObject(unknown);
+    },
+  );
+  // Like the backend: API keys and user creation report unknown roles first,
+  // while role additions report protected roles first.
+  it('orders unknown and protected role errors like the backend', async () => {
+    const client = createDemoClient();
+    const assigned = ['nope', 'super-admin'];
+    const unknown = { status: 400, message: 'Roles do not exist: nope' };
+    await expect(client.createApiKey('mixed-key', assigned)).rejects.toMatchObject(unknown);
+    await expect(client.createUser('mixed-user', assigned)).rejects.toMatchObject(unknown);
+    await expect(client.addUserRoles('analyst', assigned)).rejects.toMatchObject({
+      status: 400,
+      message: 'Role is protected',
+    });
+  });
+  it('allows ordinary admin roles for API keys and user grants', async () => {
+    const client = createDemoClient();
+    expect((await client.createApiKey('admin-key', ['administrators'])).roles).toEqual([
+      'administrators',
+    ]);
+    await client.createUser('admin-user', ['administrators']);
+    await client.addUserRoles('analyst', ['administrators']);
+    for (const id of ['admin-user', 'analyst']) {
+      expect((await client.userRoleSources(id)).roles.administrators).toEqual({
+        actions: [{ privilege: 'admin' }],
+        roleType: 'user',
+      });
+    }
+  });
   it('preserves provider overlap, removes manual grants and reconciles the fallback', async () => {
     const client = createDemoClient();
     const oauth = (await client.listUsers()).find((user) => user.method === 'oauth')!;