diff --git a/backend/services/operating_context.py b/backend/services/operating_context.py
index 1743bcd..e122ce3 100644
--- a/backend/services/operating_context.py
+++ b/backend/services/operating_context.py
@@ -47,16 +47,29 @@ def _load_ui_profile_from_db(archetype_key: str) -> Optional[dict[str, Any]]:
         conn.close()
 
 
-def _resolve_ui_profile(archetype_key: str) -> dict[str, Any]:
-    db_profile = _load_ui_profile_from_db(archetype_key)
-    if db_profile:
-        return db_profile
+def _seed_ui_profile(archetype_key: str) -> dict[str, Any]:
     seed_profile = get_ui_profile_json(archetype_key)
     if seed_profile:
         return seed_profile
     return resolve_ui_profile(archetype_key)
 
 
+def _resolve_ui_profile(archetype_key: str) -> dict[str, Any]:
+    seed_profile = _seed_ui_profile(archetype_key)
+    db_profile = _load_ui_profile_from_db(archetype_key)
+    if not db_profile:
+        return seed_profile
+
+    merged = {**seed_profile, **db_profile}
+    if not (merged.get("omCapabilities") or merged.get("dataSlices")):
+        seed_slices = seed_profile.get("dataSlices") or []
+        merged["dataSlices"] = list(seed_slices)
+        merged["omCapabilities"] = list(
+            seed_profile.get("omCapabilities") or seed_slices
+        )
+    return merged
+
+
 def _resolve_om_capabilities(ui_profile: dict[str, Any]) -> frozenset[str]:
     caps = ui_profile.get("omCapabilities") or ui_profile.get("dataSlices") or []
     return frozenset(caps)
diff --git a/backend/tests/test_ap23a_operating_context.py b/backend/tests/test_ap23a_operating_context.py
index 7c9bc94..4b3c922 100644
--- a/backend/tests/test_ap23a_operating_context.py
+++ b/backend/tests/test_ap23a_operating_context.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from auth import AUTH_HEADER
+from services import operating_context as operating_context_service
 from tests.factories import provision_user_in_tenant
 from tests.test_initiatives_actions import _auth, _create_initiative, _login
 
@@ -182,3 +183,19 @@ def test_operating_context_not_found(client):
         headers=_auth(token),
     )
     assert res.status_code == 404
+
+
+def test_resolve_ui_profile_merges_seed_slices_when_db_partial(monkeypatch):
+    monkeypatch.setattr(
+        operating_context_service,
+        "_load_ui_profile_from_db",
+        lambda _key: {
+            "planOutlineKeys": ["profile", "inbox", "sprint", "gates"],
+            "planDefaultRoute": "/plan/inbox",
+        },
+    )
+    profile = operating_context_service._resolve_ui_profile("initiative.product")
+    assert profile["planOutlineKeys"] == ["profile", "inbox", "sprint", "gates"]
+    assert "backlog" in profile["dataSlices"]
+    assert "work_cycles" in profile["dataSlices"]
+    assert profile["omCapabilities"]
diff --git a/frontend/src/context/InitiativeOperationsContext.jsx b/frontend/src/context/InitiativeOperationsContext.jsx
index 0f423c4..c2f7d12 100644
--- a/frontend/src/context/InitiativeOperationsContext.jsx
+++ b/frontend/src/context/InitiativeOperationsContext.jsx
@@ -7,6 +7,7 @@ import {
   useState,
 } from 'react'
 import { useParams } from 'react-router-dom'
+import { resolveEffectiveDataSlices } from '../registry/resolveOperatingProfile.js'
 import {
   getInitiative,
   getInitiativeSteeringSnapshot,
@@ -190,7 +191,7 @@ export function InitiativeOperationsProvider({ children, initiativeId: initiativ
         setOperatingContext(opContext)
       }
 
-      const omSlices = canReadOm ? opContext?.data_slices || [] : []
+      const omSlices = canReadOm ? resolveEffectiveDataSlices(opContext) : []
       const keysToLoad = sliceKeys || ['initiative', ...omSlices]
 
       if (keysToLoad.includes('steering_snapshot')) {
@@ -1030,7 +1031,7 @@ export function InitiativeOperationsProvider({ children, initiativeId: initiativ
     steeringSnapshotError,
     steeringMethods,
     operatingContext,
-    dataSlices: operatingContext?.data_slices || [],
+    dataSlices: resolveEffectiveDataSlices(operatingContext),
     uiFeatures,
     steeringElements,
     operatingProfile,
diff --git a/frontend/src/registry/resolveOperatingProfile.js b/frontend/src/registry/resolveOperatingProfile.js
index 9cb7501..671d40b 100644
--- a/frontend/src/registry/resolveOperatingProfile.js
+++ b/frontend/src/registry/resolveOperatingProfile.js
@@ -48,6 +48,23 @@ const EMPTY_PROFILE = {
   steeringElements: [],
 }
 
+/**
+ * API data_slices haben Vorrang; leeres Array gilt als „fehlend“ (JS-Truthy-Falle).
+ * @param {OperatingContextResponse | null | undefined} context
+ * @returns {string[]}
+ */
+export function resolveEffectiveDataSlices(context) {
+  const apiSlices = context?.data_slices
+  if (Array.isArray(apiSlices) && apiSlices.length > 0) {
+    return apiSlices
+  }
+  const profileSlices = context?.ui_profile?.dataSlices
+  if (Array.isArray(profileSlices) && profileSlices.length > 0) {
+    return profileSlices
+  }
+  return Array.isArray(apiSlices) ? apiSlices : []
+}
+
 function resolveUiFeatures(context, profileFeatures) {
   if (context?.ui_features && Object.keys(context.ui_features).length) {
     return { ...(context.ui_features || {}) }
@@ -85,7 +102,7 @@ export function resolveOperatingProfile(context, options = {}) {
         profile.controlDefaultRoute || EMPTY_PROFILE.controlDefaultRoute,
       planOutlineKeys: profile.planOutlineKeys ?? null,
       workNavKeys: profile.workNavKeys ?? null,
-      dataSlices: context.data_slices || profile.dataSlices || [],
+      dataSlices: resolveEffectiveDataSlices(context),
       uiFeatures: resolveUiFeatures(context, profile.uiFeatures),
       steeringElements: resolveSteeringElements(context),
     }
@@ -98,7 +115,7 @@ export function resolveOperatingProfile(context, options = {}) {
   })
   return {
     ...fallback,
-    dataSlices: context?.data_slices || [],
+    dataSlices: resolveEffectiveDataSlices(context),
     uiFeatures: resolveUiFeatures(context, {}),
     steeringElements: resolveSteeringElements(context),
   }
diff --git a/frontend/src/registry/resolveOperatingProfile.test.js b/frontend/src/registry/resolveOperatingProfile.test.js
index af1fa1a..805f07f 100644
--- a/frontend/src/registry/resolveOperatingProfile.test.js
+++ b/frontend/src/registry/resolveOperatingProfile.test.js
@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'vitest'
 import {
   isRouteAllowedForProfile,
+  resolveEffectiveDataSlices,
   resolveOperatingProfile,
   resolveOperatingProfileFromInput,
   resolveRedirectForDisallowedRoute,
@@ -83,6 +84,26 @@ describe('resolveOperatingProfile', () => {
     expect(isRouteAllowedForProfile('/plan/sprint', input)).toBe(true)
   })
 
+  it('leeres data_slices fällt auf ui_profile.dataSlices zurück', () => {
+    const context = {
+      ...PRODUCT_CONTEXT,
+      data_slices: [],
+      ui_profile: {
+        ...PRODUCT_CONTEXT.ui_profile,
+        dataSlices: ['backlog', 'roadmap', 'work_cycles', 'actions'],
+      },
+    }
+    expect(resolveEffectiveDataSlices(context)).toEqual([
+      'backlog',
+      'roadmap',
+      'work_cycles',
+      'actions',
+    ])
+    expect(isRouteAllowedForProfile('/plan/inbox', { operatingContext: context })).toBe(true)
+    expect(isRouteAllowedForProfile('/plan/gates', { operatingContext: context })).toBe(true)
+    expect(isRouteAllowedForProfile('/plan/sprint', { operatingContext: context })).toBe(true)
+  })
+
   it('liefert uiFeatures aus Methoden-Vertrag (API)', () => {
     const profile = resolveOperatingProfile(PRODUCT_CONTEXT)
     expect(profile.uiFeatures.continuousProductWorkMode).toBe(true)