diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.spec.tsx b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.spec.tsx
index 4a9a9ccf..7b7b5514 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.spec.tsx
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.spec.tsx
@@ -23,12 +23,12 @@ import {
   createMockWebAuthnRegistrationAction,
   externalBrowserFlowActionTitle,
   webAuthnAnyDeviceActionTitle,
-  webAuthnPlatformOnlyAnyDeviceActionTitle,
   webAuthnRegistrationActionTitle,
 } from '../../../util/tests/mocks';
 import { HaapiStepperActionsUI } from '../../../ui/actions/HaapiStepperActionsUI';
 import { HaapiStepperClientOperationUI } from './HaapiStepperClientOperationUI';
-import { WebAuthnRegistrationAttachmentKind } from '../../stepper/haapi-stepper.types';
+import type { HaapiStepperStep } from '../../stepper/haapi-stepper.types';
+import { useHaapiStepper } from '../../stepper/HaapiStepperHook';
 import { useIsWebAuthnPlatformAuthenticatorAvailable } from './operations/webauthn/useIsWebAuthnPlatformAuthenticatorAvailable';
 
 const PLATFORM_TITLE = 'Built-in';
@@ -38,7 +38,6 @@ const CROSS_PLATFORM_TITLE = 'Security key';
 const CROSS_PLATFORM_DESCRIPTION =
   'A security key, such as a portable key attached through USB or wirelessly through NFC.';
 const CROSS_PLATFORM_ICON_VIEW_BOX = '0 0 49 72.6';
-const REGISTER_VIEW_NAME = 'authenticator/webauthn/register/get';
 const MESSAGE_PREFIX = 'authenticator.webauthn.register.view.';
 const VIEW_DATA_MESSAGES = {
   [`${MESSAGE_PREFIX}button.platform`]: PLATFORM_TITLE,
@@ -51,11 +50,25 @@ vi.mock('./operations/webauthn/useIsWebAuthnPlatformAuthenticatorAvailable', ()
   useIsWebAuthnPlatformAuthenticatorAvailable: vi.fn(() => undefined),
 }));
 
+// The attachment card resolves its copy from the current step's viewData messages via
+// `useHaapiStepper`; tests drive that copy through the mocked hook.
+vi.mock('../../stepper/HaapiStepperHook', () => ({ useHaapiStepper: vi.fn() }));
+
+const mockCurrentStepMessages = (messages?: Record<string, string>) =>
+  vi.mocked(useHaapiStepper).mockReturnValue({
+    currentStep: (messages ? { metadata: { viewData: { messages } } } : null) as HaapiStepperStep | null,
+  } as ReturnType<typeof useHaapiStepper>);
+
 describe('HaapiStepperClientOperationUI', () => {
   let user: ReturnType<typeof userEvent.setup>;
 
   beforeEach(() => {
     user = userEvent.setup();
+    mockCurrentStepMessages(VIEW_DATA_MESSAGES);
+  });
+
+  afterEach(() => {
+    vi.mocked(useHaapiStepper).mockReset();
   });
 
   describe('Default rendering', () => {
@@ -113,26 +126,23 @@ describe('HaapiStepperClientOperationUI', () => {
       expect(screen.getByRole('button', { name: webAuthnRegistrationActionTitle })).toBeDisabled();
     });
 
-    it('disables a platform-only any-device registration when no platform authenticator is available', () => {
-      vi.stubGlobal('PublicKeyCredential', stubPublicKeyCredential());
-      vi.mocked(useIsWebAuthnPlatformAuthenticatorAvailable).mockReturnValue(false);
-      const action = createMockWebAuthnPlatformOnlyAnyDeviceAction();
+    it('renders a default button (not a card) for passkeys-mode registration', () => {
+      const action = createMockWebAuthnRegistrationAction();
 
       render(<HaapiStepperClientOperationUI action={action} onAction={vi.fn()} />);
 
-      expect(screen.getByRole('button', { name: webAuthnPlatformOnlyAnyDeviceActionTitle })).toBeDisabled();
+      expect(screen.queryByTestId('webauthn-registration-attachment-card')).not.toBeInTheDocument();
+      expect(screen.getByRole('button', { name: webAuthnRegistrationActionTitle })).toBeInTheDocument();
     });
 
-    it('renders one button per credential option for any-device-mode with both options, suffixing the original title', () => {
-      const action = createMockWebAuthnAnyDeviceBothOptionsAction();
-      const step = createMockStep(HAAPI_STEPS.AUTHENTICATION, { actions: [action] });
+    it('disables a platform-only any-device registration when no platform authenticator is available', () => {
+      vi.stubGlobal('PublicKeyCredential', stubPublicKeyCredential());
+      vi.mocked(useIsWebAuthnPlatformAuthenticatorAvailable).mockReturnValue(false);
+      const action = createMockWebAuthnPlatformOnlyAnyDeviceAction();
 
-      render(<HaapiStepperActionsUI actions={step.dataHelpers.actions?.all} onAction={vi.fn()} />);
+      render(<HaapiStepperClientOperationUI action={action} onAction={vi.fn()} />);
 
-      expect(screen.getByRole('button', { name: `${webAuthnAnyDeviceActionTitle} (Built-in)` })).toBeInTheDocument();
-      expect(
-        screen.getByRole('button', { name: `${webAuthnAnyDeviceActionTitle} (Security key)` })
-      ).toBeInTheDocument();
+      expect(screen.getByTestId('webauthn-registration-attachment-card')).toBeDisabled();
     });
 
     describe('WebAuthn registration attachment card (any device mode (platform/cross-platform))', () => {
@@ -140,7 +150,6 @@ describe('HaapiStepperClientOperationUI', () => {
         {
           name: 'platform',
           makeAction: createMockWebAuthnPlatformOnlyAnyDeviceAction,
-          kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
           title: PLATFORM_TITLE,
           description: PLATFORM_DESCRIPTION,
           iconViewBox: PLATFORM_ICON_VIEW_BOX,
@@ -148,17 +157,14 @@ describe('HaapiStepperClientOperationUI', () => {
         {
           name: 'cross-platform',
           makeAction: createMockWebAuthnCrossPlatformOnlyAnyDeviceAction,
-          kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM,
           title: CROSS_PLATFORM_TITLE,
           description: CROSS_PLATFORM_DESCRIPTION,
           iconViewBox: CROSS_PLATFORM_ICON_VIEW_BOX,
         },
       ])(
         'renders the $name attachment option as a card (title, description and matching icon)',
-        ({ makeAction, kind, title, description, iconViewBox }) => {
-          const action = { ...makeAction(), webauthn: { registrationAttachment: { kind, title, description } } };
-
-          const { container } = render(<HaapiStepperClientOperationUI action={action} onAction={vi.fn()} />);
+        ({ makeAction, title, description, iconViewBox }) => {
+          const { container } = render(<HaapiStepperClientOperationUI action={makeAction()} onAction={vi.fn()} />);
 
           expect(screen.getByTestId('webauthn-registration-attachment-card')).toBeInTheDocument();
           expect(screen.getByText(title)).toBeInTheDocument();
@@ -170,10 +176,9 @@ describe('HaapiStepperClientOperationUI', () => {
         }
       );
 
-      it('renders one card per option when a both-options any-device registration supplies messages', () => {
+      it('renders one card per option for a both-options any-device registration', () => {
         const step = createMockStep(HAAPI_STEPS.REGISTRATION, {
           actions: [createMockWebAuthnAnyDeviceBothOptionsAction()],
-          metadata: { viewName: REGISTER_VIEW_NAME, viewData: { messages: VIEW_DATA_MESSAGES } },
         });
 
         render(<HaapiStepperActionsUI actions={step.dataHelpers.actions?.all} onAction={vi.fn()} />);
@@ -184,6 +189,7 @@ describe('HaapiStepperClientOperationUI', () => {
       });
 
       it('renders the cards with the split action titles as fallback when the step carries no messages', () => {
+        mockCurrentStepMessages(undefined);
         const step = createMockStep(HAAPI_STEPS.REGISTRATION, {
           actions: [createMockWebAuthnAnyDeviceBothOptionsAction()],
         });
@@ -197,16 +203,6 @@ describe('HaapiStepperClientOperationUI', () => {
         expect(cards[0].querySelector('.haapi-stepper-webauthn-registration-attachment-description')).toBeNull();
         expect(cards[1].querySelector('.haapi-stepper-webauthn-registration-attachment-description')).toBeNull();
       });
-
-      it('renders the default button (no card) when the action carries no webauthn data', () => {
-        render(
-          <HaapiStepperClientOperationUI action={createMockWebAuthnPlatformOnlyAnyDeviceAction()} onAction={vi.fn()} />
-        );
-
-        expect(screen.queryByTestId('webauthn-registration-attachment-card')).not.toBeInTheDocument();
-        expect(screen.getByTestId('client-operation-action')).toBeInTheDocument();
-        expect(screen.getByRole('button', { name: webAuthnPlatformOnlyAnyDeviceActionTitle })).toBeInTheDocument();
-      });
     });
   });
 });
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.tsx b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.tsx
index ade371ec..8a6302ba 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.tsx
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/HaapiStepperClientOperationUI.tsx
@@ -11,6 +11,7 @@
 
 import { HaapiStepperClientOperationAction, HaapiStepperFormAction } from '../../stepper/haapi-stepper.types';
 import { HaapiStepperWebAuthnRegistrationAttachmentCard } from './operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard';
+import { isAnyDeviceWebAuthnRegistrationClientOperation } from './operations/webauthn';
 import { useIsClientOperationAvailable } from './useIsClientOperationAvailable';
 
 interface HaapiStepperClientOperationUIProps {
@@ -46,10 +47,10 @@ interface HaapiStepperClientOperationUIProps {
 export function HaapiStepperClientOperationUI({ action, onAction }: HaapiStepperClientOperationUIProps) {
   const isAvailable = useIsClientOperationAvailable(action);
 
-  if (action.webauthn?.registrationAttachment) {
+  if (isAnyDeviceWebAuthnRegistrationClientOperation(action)) {
     return (
       <HaapiStepperWebAuthnRegistrationAttachmentCard
-        registrationAttachment={action.webauthn.registrationAttachment}
+        action={action}
         disabled={!isAvailable}
         onClick={() => onAction(action)}
       />
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.spec.tsx b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.spec.tsx
index e17570dd..0b46122d 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.spec.tsx
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.spec.tsx
@@ -11,63 +11,72 @@
 
 import { render, screen } from '@testing-library/react';
 import userEvent from '@testing-library/user-event';
-import { describe, expect, it, vi } from 'vitest';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
 
 import {
   createMockWebAuthnCrossPlatformOnlyAnyDeviceAction,
   createMockWebAuthnPlatformOnlyAnyDeviceAction,
+  webAuthnPlatformOnlyAnyDeviceActionTitle,
 } from '../../../../../util/tests/mocks';
 import { HaapiStepperWebAuthnRegistrationAttachmentCard } from './HaapiStepperWebAuthnRegistrationAttachmentCard';
-import { WebAuthnRegistrationAttachmentKind } from '../../../../stepper/haapi-stepper.types';
+import { useHaapiStepper } from '../../../../stepper/HaapiStepperHook';
+import type { HaapiStepperStep } from '../../../../stepper/haapi-stepper.types';
+
+vi.mock('../../../../stepper/HaapiStepperHook', () => ({ useHaapiStepper: vi.fn() }));
 
 const PLATFORM_ICON_VIEW_BOX = '0 0 64.2 83.9';
 const CROSS_PLATFORM_ICON_VIEW_BOX = '0 0 49 72.6';
+const PREFIX = 'authenticator.webauthn.register.view.';
+const PLATFORM_TITLE = 'Built-in';
+const PLATFORM_DESCRIPTION = 'A non-removable built-in device.';
+const CROSS_PLATFORM_TITLE = 'Security key';
+
+// The card resolves its copy from the current step's viewData messages via `useHaapiStepper`.
+const mockCurrentStepMessages = (messages?: Record<string, string>) =>
+  vi.mocked(useHaapiStepper).mockReturnValue({
+    currentStep: (messages ? { metadata: { viewData: { messages } } } : null) as HaapiStepperStep | null,
+  } as ReturnType<typeof useHaapiStepper>);
+
+// Safe default so a test that forgets to configure the hook gets a clear assertion
+// failure rather than an opaque "cannot destructure currentStep" crash.
+beforeEach(() => mockCurrentStepMessages(undefined));
+
+afterEach(() => vi.mocked(useHaapiStepper).mockReset());
 
 describe('HaapiStepperWebAuthnRegistrationAttachmentCard', () => {
-  it('renders the title, description and matching icon resolved in the action webauthn data', () => {
-    const action = {
-      ...createMockWebAuthnPlatformOnlyAnyDeviceAction(),
-      webauthn: {
-        registrationAttachment: {
-          kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
-          title: 'Built-in',
-          description: 'A non-removable built-in device.',
-        },
-      },
-    };
+  it("renders the title, description and matching icon from the step's data", () => {
+    mockCurrentStepMessages({
+      [`${PREFIX}button.platform`]: PLATFORM_TITLE,
+      [`${PREFIX}authenticator-attachment.platform`]: PLATFORM_DESCRIPTION,
+    });
 
     const { container } = render(
       <HaapiStepperWebAuthnRegistrationAttachmentCard
-        registrationAttachment={action.webauthn.registrationAttachment}
+        action={createMockWebAuthnPlatformOnlyAnyDeviceAction()}
         onClick={vi.fn()}
       />
     );
 
-    expect(screen.getByText('Built-in')).toBeInTheDocument();
-    expect(screen.getByText('A non-removable built-in device.')).toBeInTheDocument();
+    expect(screen.getByText(PLATFORM_TITLE)).toBeInTheDocument();
+    expect(screen.getByText(PLATFORM_DESCRIPTION)).toBeInTheDocument();
     expect(container.querySelector('.haapi-stepper-webauthn-registration-attachment-icon svg')).toHaveAttribute(
       'viewBox',
       PLATFORM_ICON_VIEW_BOX
     );
   });
 
-  it('omits the description when the webauthn data has none, still rendering the icon', () => {
-    const action = {
-      ...createMockWebAuthnCrossPlatformOnlyAnyDeviceAction(),
-      webauthn: {
-        registrationAttachment: { kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM, title: 'Security key' },
-      },
-    };
+  it('omits the description when the step has no description message, still rendering the icon', () => {
+    mockCurrentStepMessages({ [`${PREFIX}button.cross-platform`]: CROSS_PLATFORM_TITLE });
 
     const { container } = render(
       <HaapiStepperWebAuthnRegistrationAttachmentCard
-        registrationAttachment={action.webauthn.registrationAttachment}
+        action={createMockWebAuthnCrossPlatformOnlyAnyDeviceAction()}
         onClick={vi.fn()}
       />
     );
 
     const card = screen.getByTestId('webauthn-registration-attachment-card');
-    expect(screen.getByText('Security key')).toBeInTheDocument();
+    expect(screen.getByText(CROSS_PLATFORM_TITLE)).toBeInTheDocument();
     expect(card.querySelector('.haapi-stepper-webauthn-registration-attachment-description')).toBeNull();
     expect(container.querySelector('.haapi-stepper-webauthn-registration-attachment-icon svg')).toHaveAttribute(
       'viewBox',
@@ -75,17 +84,27 @@ describe('HaapiStepperWebAuthnRegistrationAttachmentCard', () => {
     );
   });
 
+  it('falls back to the action title when the step carries no view-data', () => {
+    mockCurrentStepMessages(undefined);
+
+    render(
+      <HaapiStepperWebAuthnRegistrationAttachmentCard
+        action={createMockWebAuthnPlatformOnlyAnyDeviceAction()}
+        onClick={vi.fn()}
+      />
+    );
+
+    expect(screen.getByText(webAuthnPlatformOnlyAnyDeviceActionTitle)).toBeInTheDocument();
+  });
+
   it('calls onClick when the card is clicked', async () => {
     const user = userEvent.setup();
     const onClick = vi.fn();
-    const action = {
-      ...createMockWebAuthnPlatformOnlyAnyDeviceAction(),
-      webauthn: { registrationAttachment: { kind: WebAuthnRegistrationAttachmentKind.PLATFORM, title: 'Built-in' } },
-    };
+    mockCurrentStepMessages(undefined);
 
     render(
       <HaapiStepperWebAuthnRegistrationAttachmentCard
-        registrationAttachment={action.webauthn.registrationAttachment}
+        action={createMockWebAuthnPlatformOnlyAnyDeviceAction()}
         onClick={onClick}
       />
     );
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.tsx b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.tsx
index dd7f16b9..888bc549 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.tsx
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/HaapiStepperWebAuthnRegistrationAttachmentCard.tsx
@@ -9,12 +9,14 @@
  * For further information, please contact Curity AB.
  */
 
-import { HaapiStepperWebAuthnRegistrationAttachment } from '../../../../stepper/haapi-stepper.types';
+import { HaapiStepperWebAuthnAnyDeviceRegistrationAction } from '../../../../stepper/haapi-stepper.types';
+import { useHaapiStepper } from '../../../../stepper/HaapiStepperHook';
+import { getAnyDeviceWebAuthnRegistrationAttachment } from './webauthn-registration-attachment';
 import { REGISTRATION_ATTACHMENT_ICON } from './webauthn-registration-attachment-icon-map';
 
 export interface HaapiStepperWebAuthnRegistrationAttachmentCardProps {
   /** The (split) any-device `webauthn-registration` action this option advances the flow with. */
-  registrationAttachment: HaapiStepperWebAuthnRegistrationAttachment;
+  action: HaapiStepperWebAuthnAnyDeviceRegistrationAction;
   /** Disables the card (e.g. when the required authenticator capability is unavailable). */
   disabled?: boolean;
   onClick: () => void;
@@ -24,14 +26,18 @@ export interface HaapiStepperWebAuthnRegistrationAttachmentCardProps {
  * A single WebAuthn registration attachment-selection option, rendered as a clickable card
  * (icon + bold title + description).
  *
- * Exported so consumers building a custom WebAuthn registration UI can reuse it.
+ * Must be rendered within `HaapiStepper`, for the current active step's action.
  */
 export const HaapiStepperWebAuthnRegistrationAttachmentCard = ({
-  registrationAttachment,
+  action,
   disabled,
   onClick,
 }: HaapiStepperWebAuthnRegistrationAttachmentCardProps) => {
-  const { kind, title, description } = registrationAttachment;
+  const { currentStep } = useHaapiStepper();
+  const { kind, title, description } = getAnyDeviceWebAuthnRegistrationAttachment(
+    action,
+    currentStep?.metadata?.viewData?.messages
+  );
 
   return (
     <button
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/utils.ts b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/utils.ts
index a9b6d519..acac1424 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/utils.ts
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/utils.ts
@@ -141,11 +141,10 @@ export function isAnyDeviceWebAuthnRegistrationAction(
 /**
  * Any-device `webauthn-registration` client operation — the only registration case that offers a
  * platform vs cross-platform attachment choice (passkeys mode collapses them into a single option).
- * This is exactly the case the built-in attachment-selection card is rendered for.
  */
-export function isAnyDeviceWebAuthnRegistrationClientOperation(
-  action: HaapiAction
-): action is HaapiWebAuthnAnyDeviceRegistrationAction {
+export function isAnyDeviceWebAuthnRegistrationClientOperation<T extends HaapiAction>(
+  action: T
+): action is T & HaapiWebAuthnAnyDeviceRegistrationAction {
   return isWebAuthnRegistrationClientOperation(action) && isAnyDeviceWebAuthnRegistrationAction(action);
 }
 
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.spec.ts b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.spec.ts
new file mode 100644
index 00000000..f58e885a
--- /dev/null
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.spec.ts
@@ -0,0 +1,72 @@
+/*
+ * Copyright (C) 2026 Curity AB. All rights reserved.
+ *
+ * The contents of this file are the property of Curity AB.
+ * You may not copy or use this file, in either source code
+ * or executable form, except in compliance with terms
+ * set by Curity AB.
+ *
+ * For further information, please contact Curity AB.
+ */
+
+import { describe, expect, it } from 'vitest';
+
+import {
+  createMockWebAuthnCrossPlatformOnlyAnyDeviceAction,
+  createMockWebAuthnPlatformOnlyAnyDeviceAction,
+  webAuthnPlatformOnlyAnyDeviceActionTitle,
+} from '../../../../../util/tests/mocks';
+import { WebAuthnRegistrationAttachmentKind } from '../../../../stepper/haapi-stepper.types';
+import { getAnyDeviceWebAuthnRegistrationAttachment } from './webauthn-registration-attachment';
+
+const PREFIX = 'authenticator.webauthn.register.view.';
+const PLATFORM_TITLE = 'Built-in';
+const PLATFORM_DESCRIPTION = 'A non-removable built-in device.';
+const CROSS_PLATFORM_TITLE = 'Security key';
+const CROSS_PLATFORM_DESCRIPTION = 'A security key.';
+const VIEW_DATA_MESSAGES = {
+  [`${PREFIX}button.platform`]: PLATFORM_TITLE,
+  [`${PREFIX}button.cross-platform`]: CROSS_PLATFORM_TITLE,
+  [`${PREFIX}authenticator-attachment.platform`]: PLATFORM_DESCRIPTION,
+  [`${PREFIX}authenticator-attachment.cross-platform`]: CROSS_PLATFORM_DESCRIPTION,
+};
+
+describe('getAnyDeviceWebAuthnRegistrationAttachment', () => {
+  it('resolves the platform kind, localized title and description from the view-data messages', () => {
+    const result = getAnyDeviceWebAuthnRegistrationAttachment(createMockWebAuthnPlatformOnlyAnyDeviceAction(), {
+      ...VIEW_DATA_MESSAGES,
+      'authenticator.webauthn.register.page.title': 'Register a device',
+    });
+
+    expect(result).toEqual({
+      kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
+      title: PLATFORM_TITLE,
+      description: PLATFORM_DESCRIPTION,
+    });
+  });
+
+  it('resolves the cross-platform copy for a cross-platform action', () => {
+    const result = getAnyDeviceWebAuthnRegistrationAttachment(
+      createMockWebAuthnCrossPlatformOnlyAnyDeviceAction(),
+      VIEW_DATA_MESSAGES
+    );
+
+    expect(result).toEqual({
+      kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM,
+      title: CROSS_PLATFORM_TITLE,
+      description: CROSS_PLATFORM_DESCRIPTION,
+    });
+  });
+
+  it('falls back to the action title and omits the description when there are no messages', () => {
+    const result = getAnyDeviceWebAuthnRegistrationAttachment(
+      createMockWebAuthnPlatformOnlyAnyDeviceAction(),
+      undefined
+    );
+
+    expect(result).toEqual({
+      kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
+      title: webAuthnPlatformOnlyAnyDeviceActionTitle,
+    });
+  });
+});
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.ts b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.ts
similarity index 68%
rename from src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.ts
rename to src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.ts
index 887be272..6f99401a 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.ts
+++ b/src/haapi-react-sdk/haapi-stepper/feature/actions/client-operation/operations/webauthn/webauthn-registration-attachment.ts
@@ -9,22 +9,24 @@
  * For further information, please contact Curity AB.
  */
 
-import { HaapiWebAuthnAnyDeviceRegistrationAction } from '../../../data-access/types/haapi-action.types';
-import { HaapiStepperWebAuthnData, WebAuthnRegistrationAttachmentKind } from '../haapi-stepper.types';
-import { getWebAuthnRegistrationAttachmentKind } from '../../actions/client-operation/operations/webauthn';
+import { HaapiWebAuthnAnyDeviceRegistrationAction } from '../../../../../data-access/types/haapi-action.types';
+import {
+  HaapiStepperWebAuthnRegistrationAttachment,
+  WebAuthnRegistrationAttachmentKind,
+} from '../../../../stepper/haapi-stepper.types';
+import { getWebAuthnRegistrationAttachmentKind } from './utils';
 
 /**
- * Builds the `webauthn` data of a (split) any-device `webauthn-registration` action — its
- * `registrationAttachment`:
+ * Builds the registration attachment of a (split) any-device `webauthn-registration` action:
  *
  *  - `kind` — the attachment the action carries, derived from its `model.arguments`.
  *  - `title` / `description` — the attachment option copy looked up from `metadata.viewData.messages`,
  *    with the action title as the `title` fallback.
  */
-export function getWebAuthnData(
+export function getAnyDeviceWebAuthnRegistrationAttachment(
   action: HaapiWebAuthnAnyDeviceRegistrationAction,
   viewDataMessages?: Record<string, string>
-): HaapiStepperWebAuthnData {
+): HaapiStepperWebAuthnRegistrationAttachment {
   // The exact keys the webauthn authenticator uses for the attachment-selection copy.
   const attachmentKey = (property: 'button' | 'authenticator-attachment', kind: WebAuthnRegistrationAttachmentKind) =>
     `authenticator.webauthn.register.view.${property}.${kind}`;
@@ -34,10 +36,8 @@ export function getWebAuthnData(
   const description = viewDataMessages?.[attachmentKey('authenticator-attachment', kind)];
 
   return {
-    registrationAttachment: {
-      kind,
-      ...(title !== undefined && { title }),
-      ...(description !== undefined && { description }),
-    },
+    kind,
+    ...(title !== undefined && { title }),
+    ...(description !== undefined && { description }),
   };
 }
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.spec.ts b/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.spec.ts
deleted file mode 100644
index a52d1940..00000000
--- a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.spec.ts
+++ /dev/null
@@ -1,94 +0,0 @@
-/*
- * Copyright (C) 2026 Curity AB. All rights reserved.
- *
- * The contents of this file are the property of Curity AB.
- * You may not copy or use this file, in either source code
- * or executable form, except in compliance with terms
- * set by Curity AB.
- *
- * For further information, please contact Curity AB.
- */
-
-import { describe, expect, it } from 'vitest';
-
-import { HAAPI_STEPS } from '../../../data-access/types/haapi-step.types';
-import {
-  createMockExternalBrowserFlowAction,
-  createMockStep,
-  createMockWebAuthnAnyDeviceBothOptionsAction,
-  webAuthnAnyDeviceActionTitle,
-} from '../../../util/tests/mocks';
-import { WebAuthnRegistrationAttachmentKind } from '../haapi-stepper.types';
-
-const REGISTER_VIEW_NAME = 'authenticator/webauthn/register/get';
-const MESSAGE_PREFIX = 'authenticator.webauthn.register.view.';
-const VIEW_DATA_MESSAGES = {
-  [`${MESSAGE_PREFIX}button.platform`]: 'Built-in',
-  [`${MESSAGE_PREFIX}button.cross-platform`]: 'Security key',
-  [`${MESSAGE_PREFIX}authenticator-attachment.platform`]: 'A non-removable built-in device.',
-  [`${MESSAGE_PREFIX}authenticator-attachment.cross-platform`]: 'A security key.',
-};
-
-describe('formatNextStepData — webauthn data', () => {
-  it('adds the resolved webauthn data to the split webauthn client-operation actions', () => {
-    const step = createMockStep(HAAPI_STEPS.REGISTRATION, {
-      actions: [createMockWebAuthnAnyDeviceBothOptionsAction()],
-      metadata: {
-        viewName: REGISTER_VIEW_NAME,
-        viewData: {
-          messages: { ...VIEW_DATA_MESSAGES, 'authenticator.webauthn.register.page.title': 'Register a device' },
-        },
-      },
-    });
-
-    const clientOperations = step.dataHelpers.actions?.clientOperation ?? [];
-
-    expect(clientOperations).toHaveLength(2);
-    expect(clientOperations[0].webauthn).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
-        title: 'Built-in',
-        description: 'A non-removable built-in device.',
-      },
-    });
-    expect(clientOperations[1].webauthn).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM,
-        title: 'Security key',
-        description: 'A security key.',
-      },
-    });
-  });
-
-  it('falls back to the split action titles when the step carries no viewData', () => {
-    const step = createMockStep(HAAPI_STEPS.REGISTRATION, {
-      actions: [createMockWebAuthnAnyDeviceBothOptionsAction()],
-      metadata: { viewName: REGISTER_VIEW_NAME },
-    });
-
-    const clientOperations = step.dataHelpers.actions?.clientOperation ?? [];
-
-    expect(clientOperations).toHaveLength(2);
-    expect(clientOperations[0].webauthn).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
-        title: `${webAuthnAnyDeviceActionTitle} (Built-in)`,
-      },
-    });
-    expect(clientOperations[1].webauthn).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM,
-        title: `${webAuthnAnyDeviceActionTitle} (Security key)`,
-      },
-    });
-  });
-
-  it('does not add webauthn data to other client operations', () => {
-    const step = createMockStep(HAAPI_STEPS.AUTHENTICATION, {
-      actions: [createMockExternalBrowserFlowAction()],
-      metadata: { viewName: REGISTER_VIEW_NAME, viewData: { messages: VIEW_DATA_MESSAGES } },
-    });
-
-    expect(step.dataHelpers.actions?.clientOperation[0].webauthn).toBeUndefined();
-  });
-});
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.ts b/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.ts
index a909b3f1..9a516c11 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.ts
+++ b/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/format-next-step-data.ts
@@ -29,11 +29,9 @@ import {
   HaapiStepperUserMessage,
 } from '../haapi-stepper.types';
 import {
-  isAnyDeviceWebAuthnRegistrationClientOperation,
   isWebAuthnRegistrationClientOperation,
   splitWebAuthnRegistrationAction,
 } from '../../actions/client-operation/operations/webauthn';
-import { getWebAuthnData } from './webauthn-data';
 
 export function formatNextStepData<T extends HaapiActionStep | HaapiCompletedStep | HaapiStepperStep>(
   step: T
@@ -99,16 +97,6 @@ function addActionDataHelpers(
     };
   }
 
-  if (
-    actionWithDataHelpers.subtype === HAAPI_ACTION_TYPES.CLIENT_OPERATION &&
-    isAnyDeviceWebAuthnRegistrationClientOperation(actionWithDataHelpers)
-  ) {
-    return {
-      ...actionWithDataHelpers,
-      webauthn: getWebAuthnData(actionWithDataHelpers, step.metadata?.viewData?.messages),
-    };
-  }
-
   return { ...action, ...actionWithDataHelpers };
 }
 
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.spec.ts b/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.spec.ts
deleted file mode 100644
index 3eaf88b4..00000000
--- a/src/haapi-react-sdk/haapi-stepper/feature/stepper/data-formatters/webauthn-data.spec.ts
+++ /dev/null
@@ -1,68 +0,0 @@
-/*
- * Copyright (C) 2026 Curity AB. All rights reserved.
- *
- * The contents of this file are the property of Curity AB.
- * You may not copy or use this file, in either source code
- * or executable form, except in compliance with terms
- * set by Curity AB.
- *
- * For further information, please contact Curity AB.
- */
-
-import { describe, expect, it } from 'vitest';
-
-import {
-  createMockWebAuthnCrossPlatformOnlyAnyDeviceAction,
-  createMockWebAuthnPlatformOnlyAnyDeviceAction,
-  webAuthnPlatformOnlyAnyDeviceActionTitle,
-} from '../../../util/tests/mocks';
-import { WebAuthnRegistrationAttachmentKind } from '../haapi-stepper.types';
-import { getWebAuthnData } from './webauthn-data';
-
-const MESSAGE_PREFIX = 'authenticator.webauthn.register.view.';
-const VIEW_DATA_MESSAGES = {
-  [`${MESSAGE_PREFIX}button.platform`]: 'Built-in',
-  [`${MESSAGE_PREFIX}button.cross-platform`]: 'Security key',
-  [`${MESSAGE_PREFIX}authenticator-attachment.platform`]: 'A non-removable built-in device.',
-  [`${MESSAGE_PREFIX}authenticator-attachment.cross-platform`]: 'A security key.',
-};
-
-describe('getWebAuthnData', () => {
-  it('resolves the kind, localized title and description, and the attachment messages (keys untouched)', () => {
-    const result = getWebAuthnData(createMockWebAuthnPlatformOnlyAnyDeviceAction(), {
-      ...VIEW_DATA_MESSAGES,
-      'authenticator.webauthn.register.page.title': 'Register a device',
-    });
-
-    expect(result).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
-        title: 'Built-in',
-        description: 'A non-removable built-in device.',
-      },
-    });
-  });
-
-  it('resolves the cross-platform copy for a cross-platform action', () => {
-    const result = getWebAuthnData(createMockWebAuthnCrossPlatformOnlyAnyDeviceAction(), VIEW_DATA_MESSAGES);
-
-    expect(result).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.CROSS_PLATFORM,
-        title: 'Security key',
-        description: 'A security key.',
-      },
-    });
-  });
-
-  it('falls back to the action title when there are no messages', () => {
-    const result = getWebAuthnData(createMockWebAuthnPlatformOnlyAnyDeviceAction(), undefined);
-
-    expect(result).toEqual({
-      registrationAttachment: {
-        kind: WebAuthnRegistrationAttachmentKind.PLATFORM,
-        title: webAuthnPlatformOnlyAnyDeviceActionTitle,
-      },
-    });
-  });
-});
diff --git a/src/haapi-react-sdk/haapi-stepper/feature/stepper/haapi-stepper.types.ts b/src/haapi-react-sdk/haapi-stepper/feature/stepper/haapi-stepper.types.ts
index 0ba82bcc..4c16052c 100644
--- a/src/haapi-react-sdk/haapi-stepper/feature/stepper/haapi-stepper.types.ts
+++ b/src/haapi-react-sdk/haapi-stepper/feature/stepper/haapi-stepper.types.ts
@@ -138,18 +138,7 @@ export type HaapiStepperSelectorAction = Omit<HaapiSelectorAction, 'model'> &
     };
   };
 export type HaapiStepperClientOperationAction = HaapiClientOperationAction &
-  HaapiStepperDataHelpersDetails<HAAPI_STEPPER_ELEMENT_TYPES.ACTION, HAAPI_ACTION_TYPES.CLIENT_OPERATION> & {
-    /**
-     * WebAuthn data resolved during step-data formatting. Present only on any-device
-     * `webauthn-registration` actions.
-     */
-    webauthn?: HaapiStepperWebAuthnData;
-  };
-
-/** WebAuthn data resolved during step-data formatting for an any-device registration action. */
-export interface HaapiStepperWebAuthnData {
-  registrationAttachment: HaapiStepperWebAuthnRegistrationAttachment;
-}
+  HaapiStepperDataHelpersDetails<HAAPI_STEPPER_ELEMENT_TYPES.ACTION, HAAPI_ACTION_TYPES.CLIENT_OPERATION>;
 
 /** The registration attachment option a (split) any-device `webauthn-registration` action carries. */
 export interface HaapiStepperWebAuthnRegistrationAttachment {