diff --git a/packages/client/ui-conversation/tests/skeleton.client.spec.tsx b/packages/client/ui-conversation/tests/skeleton.client.spec.tsx
index 2db2db153b..c88ffd6b5b 100644
--- a/packages/client/ui-conversation/tests/skeleton.client.spec.tsx
+++ b/packages/client/ui-conversation/tests/skeleton.client.spec.tsx
@@ -266,7 +266,12 @@ describe('Hero chrome', () => {
     expect(view.getByText('Preview')).toBeTruthy()
     expect(renderSlot).toHaveBeenCalledOnce()
     expect(renderSlot.mock.calls[0]?.[0]).toBe('conversation.hero.brand.mark')
-    expect(renderSlot.mock.calls[0]?.[1]).toEqual({ size: 34 })
+    const brandMarkOwner = renderSlot.mock.calls[0]?.[1]
+    if (brandMarkOwner === undefined || !('size' in brandMarkOwner) || !('className' in brandMarkOwner)) {
+      throw new Error('hero brand-mark owner must provide size and className')
+    }
+    expect(brandMarkOwner.size).toBe(34)
+    expect(brandMarkOwner.className).toBeTypeOf('string')
     expect(renderSlot.mock.calls[0]?.[2]?.fallback).toBeTruthy()
   })
 })
diff --git a/packages/extensions/cordis-client-runner/src/client/slot-catalog.ts b/packages/extensions/cordis-client-runner/src/client/slot-catalog.ts
index 36888b00c6..90e7434f3c 100644
--- a/packages/extensions/cordis-client-runner/src/client/slot-catalog.ts
+++ b/packages/extensions/cordis-client-runner/src/client/slot-catalog.ts
@@ -491,7 +491,7 @@ export const CLIENT_SLOT_API: readonly ClientSlotEntry[] = [
     doc: 'Brand mark leading the blank-session headline. Declared by this\npackage\'s `conversation` entry; the shell supplies a fish fallback.',
     registerOptions: [],
     ownerProps: [
-      '/** Geometry supplied to the blank-session brand-mark occupant. */\nexport interface HeroBrandMarkOwnerProps {\n  /** Requested square edge in pixels. */\n  size: number\n}',
+      '/** Presentation props supplied to the blank-session brand-mark occupant. */\nexport interface HeroBrandMarkOwnerProps {\n  /** Requested square edge in pixels. */\n  size: number\n  /** Host CSS class for preserving the default hero mark color and hover motion. */\n  className?: string | undefined\n}',
     ],
     ownerPropsReferences: [],
     standardProps: [