diff --git a/api/src/HttpCache/TagCollector.php b/api/src/HttpCache/TagCollector.php
index d1e1c84119..9f3ebbe224 100644
--- a/api/src/HttpCache/TagCollector.php
+++ b/api/src/HttpCache/TagCollector.php
@@ -8,6 +8,9 @@
 use ApiPlatform\Metadata\Operation;
 use ApiPlatform\Serializer\TagCollectorInterface;
 use App\Entity\HasId;
+use Doctrine\Common\Util\ClassUtils;
+use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\Mapping\AssociationMapping;
 
 /**
  * Collects cache tags during normalization.
@@ -17,7 +20,10 @@
 class TagCollector implements TagCollectorInterface {
     public const IRI_RELATION_DELIMITER = '#';
 
-    public function __construct(private ResponseTagger $responseTagger) {}
+    public function __construct(
+        private ResponseTagger $responseTagger,
+        private EntityManagerInterface $em
+    ) {}
 
     /**
      * Collect cache tags for cache invalidation.
@@ -37,7 +43,7 @@ public function collect(array $context = []): void {
         }
 
         if (isset($context['property_metadata'])) {
-            $this->addCacheTagsForRelation($context, $iri, $context['property_metadata']);
+            $this->addCacheTagsForRelation($object, $context, $iri, $context['property_metadata']);
 
             return;
         }
@@ -59,7 +65,7 @@ private function addCacheTagForResource(string $iri): void {
         $this->responseTagger->addTags([$iri]);
     }
 
-    private function addCacheTagsForRelation(array $context, string $iri, ApiProperty $propertyMetadata): void {
+    private function addCacheTagsForRelation(mixed $object, array $context, string $iri, ApiProperty $propertyMetadata): void {
         if (isset($propertyMetadata->getExtraProperties()['cacheDependencies'])) {
             foreach ($propertyMetadata->getExtraProperties()['cacheDependencies'] as $dependency) {
                 $cacheTag = $iri.PurgeHttpCacheListener::IRI_RELATION_DELIMITER.$dependency;
@@ -69,6 +75,13 @@ private function addCacheTagsForRelation(array $context, string $iri, ApiPropert
             return;
         }
 
+        $associationMappings = $this->em->getClassMetadata(ClassUtils::getClass($object))->getAssociationMappings();
+        $associationMapping = $associationMappings[$context['api_attribute']] ?? null;
+        // we have currently no use-case where we rely on a ManyToOne for tag invalidation
+        if ($associationMapping instanceof AssociationMapping && $associationMapping->isManyToOne()) {
+            return;
+        }
+
         $cacheTag = $iri.PurgeHttpCacheListener::IRI_RELATION_DELIMITER.$context['api_attribute'];
         $this->responseTagger->addTags([$cacheTag]);
     }
diff --git a/api/tests/HttpCache/TagCollectorTest.php b/api/tests/HttpCache/TagCollectorTest.php
index 254c468350..fa7ba99133 100644
--- a/api/tests/HttpCache/TagCollectorTest.php
+++ b/api/tests/HttpCache/TagCollectorTest.php
@@ -7,6 +7,8 @@
 use App\HttpCache\ResponseTagger;
 use App\HttpCache\TagCollector;
 use App\Tests\HttpCache\Entity\Dummy;
+use Doctrine\ORM\EntityManagerInterface;
+use Doctrine\ORM\Mapping\ClassMetadata;
 use PHPUnit\Framework\TestCase;
 use Prophecy\Argument;
 use Prophecy\PhpUnit\ProphecyTrait;
@@ -20,11 +22,17 @@ class TagCollectorTest extends TestCase {
 
     private TagCollectorInterface $tagCollector;
     private ObjectProphecy $responseTaggerProphecy;
+    private ObjectProphecy $em;
+    private ObjectProphecy $classMetadata;
 
     protected function setUp(): void {
         // given
         $this->responseTaggerProphecy = $this->prophesize(ResponseTagger::class);
-        $this->tagCollector = new TagCollector($this->responseTaggerProphecy->reveal());
+        $this->em = $this->prophesize(EntityManagerInterface::class);
+        $this->classMetadata = $this->prophesize(ClassMetadata::class);
+        $this->em->getClassMetadata(Argument::any())->willReturn($this->classMetadata);
+        $this->classMetadata->getAssociationMappings(Argument::any())->willReturn([]);
+        $this->tagCollector = new TagCollector($this->responseTaggerProphecy->reveal(), $this->em->reveal());
     }
 
     public function testNoTagForEmptyContext() {
diff --git a/e2e/specs/httpCache/activities.cy.js b/e2e/specs/httpCache/activities.cy.js
index b8572aced5..f990a71d2a 100644
--- a/e2e/specs/httpCache/activities.cy.js
+++ b/e2e/specs/httpCache/activities.cy.js
@@ -16,42 +16,48 @@ const collectionXKeys =
   /**
    * activitiy "Snowboardfahren"
    */
-  'a13fadc97610 a13fadc97610#scheduleEntries a13fadc97610#camp a13fadc97610#category a13fadc97610#progressLabel a13fadc97610#activityResponsibles a13fadc97610#rootContentNode ' +
+  'a13fadc97610 a13fadc97610#scheduleEntries a13fadc97610#activityResponsibles a13fadc97610#rootContentNode ' +
   /* embedded progress labels: */
-  'af92782262d7 af92782262d7#camp a13fadc97610#embeddedProgressLabel ' +
+  'af92782262d7 ' +
+  'a13fadc97610#embeddedProgressLabel ' +
   /* embedded schedule entries: */
   /* (the first schedule entry also includes the period id) */
-  '29c9e9a07d82 7fa4564a5d5d 29c9e9a07d82#period 29c9e9a07d82#activity 29c9e9a07d82#day ' +
-  'f08d69cae18a f08d69cae18a#period f08d69cae18a#activity f08d69cae18a#day ' +
-  '7e8086d94633 7e8086d94633#period 7e8086d94633#activity 7e8086d94633#day ' +
+  '29c9e9a07d82 7fa4564a5d5d 29c9e9a07d82#day ' +
+  'f08d69cae18a f08d69cae18a#day ' +
+  '7e8086d94633 7e8086d94633#day ' +
   'a13fadc97610#embeddedScheduleEntries ' +
   /* embedded activitiy responsibles: */
-  '06743ccfeedd 06743ccfeedd#activity 06743ccfeedd#campCollaboration ' +
-  '21bc6661c569 21bc6661c569#activity 21bc6661c569#campCollaboration ' +
-  'a13fadc97610#embeddedActivityResponsibles a13fadc97610#contentNodes ' +
+  '06743ccfeedd ' +
+  '21bc6661c569 ' +
+  'a13fadc97610#embeddedActivityResponsibles ' +
+  'a13fadc97610#contentNodes ' +
   /**
    * activity "Skifahren"
    */
-  'b29d387cc403 b29d387cc403#scheduleEntries b29d387cc403#camp b29d387cc403#category b29d387cc403#progressLabel b29d387cc403#activityResponsibles ' +
+  'b29d387cc403 b29d387cc403#scheduleEntries b29d387cc403#activityResponsibles b29d387cc403#rootContentNode ' +
   /* embedded progress labels: */
-  'b29d387cc403#rootContentNode b29d387cc403#embeddedProgressLabel ' +
+  'b29d387cc403#embeddedProgressLabel ' +
   /* embedded schedule entries: */
-  'e68f4e47517a e68f4e47517a#period e68f4e47517a#activity e68f4e47517a#day ' +
-  'f0883e931649 f0883e931649#period f0883e931649#activity f0883e931649#day ' +
-  'ee85308a97d1 ee85308a97d1#period ee85308a97d1#activity ee85308a97d1#day ' +
-  'f89a1501dbb6 f89a1501dbb6#period f89a1501dbb6#activity f89a1501dbb6#day ' +
+  'e68f4e47517a e68f4e47517a#day ' +
+  'f0883e931649 f0883e931649#day ' +
+  'ee85308a97d1 ee85308a97d1#day ' +
+  'f89a1501dbb6 f89a1501dbb6#day ' +
   /* embedded activitiy responsibles: */
   'b29d387cc403#embeddedScheduleEntries ' +
-  'a9a760e36fd8 a9a760e36fd8#activity a9a760e36fd8#campCollaboration b29d387cc403#embeddedActivityResponsibles ' +
+  'a9a760e36fd8 ' +
+  'b29d387cc403#embeddedActivityResponsibles ' +
   'b29d387cc403#contentNodes ' +
   /* collection URI (for detecting addition of new activities) */
   '/api/camps/70ca971c992f/activities'
 
 describe('cache test: /camps/{campId}/activities', () => {
+  beforeEach(() => {
+    cy.wrap(Cypress.session.clearAllSavedSessions())
+  })
+
   it('caches /camps/{campId}/activities separately for each login', () => {
     const uri = `/api/camps/${skilagerCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
@@ -75,7 +81,6 @@ describe('cache test: /camps/{campId}/activities', () => {
     const activityId = '3d1e5c91ceb2'
 
     // bring data into defined state
-    Cypress.session.clearAllSavedSessions()
     cy.login(bruceWayneUser)
     cy.apiPatch(`/api/activities/${activityId}`, {
       title: 'Breakfast',
@@ -105,7 +110,6 @@ describe('cache test: /camps/{campId}/activities', () => {
   it('invalidates /camps/{campId}/activities for new activity', () => {
     const uri = `/api/camps/${grgrCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -142,7 +146,6 @@ describe('cache test: /camps/{campId}/activities', () => {
   it('invalidates /camps/{campId}/activities when adding a scheduleEntry', () => {
     const uri = `/api/camps/${grgrCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -176,7 +179,6 @@ describe('cache test: /camps/{campId}/activities', () => {
     const progressLabelId = '82547049ea38'
 
     // bring data into defined state
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
     cy.apiPatch(`/api/activity_progress_labels/${progressLabelId}`, {
       title: 'Planned',
@@ -199,7 +201,6 @@ describe('cache test: /camps/{campId}/activities', () => {
   it('invalidates /camps/{campId}/activities when adding an activity responsible', () => {
     const uri = `/api/camps/${grgrCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -229,7 +230,6 @@ describe('cache test: /camps/{campId}/activities', () => {
   it('invalidates /camps/{campId}/activities when changing the period dates (moveScheduleEntries: true)', () => {
     const uri = `/api/camps/${grgrCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -262,7 +262,6 @@ describe('cache test: /camps/{campId}/activities', () => {
   it('invalidates /camps/{campId}/activities when changing the period dates (moveScheduleEntries: false)', () => {
     const uri = `/api/camps/${grgrCampId}/activities`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
diff --git a/e2e/specs/httpCache/categories.cy.js b/e2e/specs/httpCache/categories.cy.js
index 637960aba5..2981164128 100644
--- a/e2e/specs/httpCache/categories.cy.js
+++ b/e2e/specs/httpCache/categories.cy.js
@@ -13,21 +13,24 @@ const collectionXKeys =
   /* campCollaboration for bipiUser */
   'b0bdb7202a9d ' +
   /* Category ES */
-  'ebfd46a1c181 ebfd46a1c181#camp ebfd46a1c181#preferredContentTypes ebfd46a1c181#rootContentNode ebfd46a1c181#contentNodes ' +
+  'ebfd46a1c181 ebfd46a1c181#preferredContentTypes ebfd46a1c181#rootContentNode ebfd46a1c181#contentNodes ' +
   /* Category LA */
-  '1a869b162875 1a869b162875#camp 1a869b162875#preferredContentTypes 1a869b162875#rootContentNode 1a869b162875#contentNodes ' +
+  '1a869b162875 1a869b162875#preferredContentTypes 1a869b162875#rootContentNode 1a869b162875#contentNodes ' +
   /* Category LP */
-  'dfa531302823 dfa531302823#camp dfa531302823#preferredContentTypes dfa531302823#rootContentNode dfa531302823#contentNodes ' +
+  'dfa531302823 dfa531302823#preferredContentTypes dfa531302823#rootContentNode dfa531302823#contentNodes ' +
   /* Category LS */
-  'a023e85227ac a023e85227ac#camp a023e85227ac#preferredContentTypes a023e85227ac#rootContentNode a023e85227ac#contentNodes ' +
+  'a023e85227ac a023e85227ac#preferredContentTypes a023e85227ac#rootContentNode a023e85227ac#contentNodes ' +
   /* collection URI (for detecting addition of new categories) */
   '/api/camps/3c79b99ab424/categories'
 
 describe('cache test: /camps/{campId}/categories', () => {
+  beforeEach(() => {
+    cy.wrap(Cypress.session.clearAllSavedSessions())
+  })
+
   it('caches /camps/{campId}/categories separately for each login', () => {
     const uri = `/api/camps/${grgrCampId}/categories`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
@@ -50,7 +53,6 @@ describe('cache test: /camps/{campId}/categories', () => {
     const uri = `/api/camps/${loremIpsumCampId}/categories`
 
     // bring data into defined state
-    Cypress.session.clearAllSavedSessions()
     cy.login(bruceWayneUser)
     cy.apiPatch('/api/categories/c5e1bc565094', {
       name: 'old_name',
@@ -80,7 +82,6 @@ describe('cache test: /camps/{campId}/categories', () => {
   it('invalidates /camps/{campId}/categories for new category', () => {
     const uri = `/api/camps/${grgrCampId}/categories`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -111,7 +112,6 @@ describe('cache test: /camps/{campId}/categories', () => {
   })
 
   it('invalidates cached data when user leaves a camp', () => {
-    Cypress.session.clearAllSavedSessions()
     const uri = `/api/camps/${grgrCampId}/categories`
 
     cy.intercept('PATCH', '/api/camp_collaborations/**').as('camp_collaboration')
diff --git a/e2e/specs/httpCache/checklists.cy.js b/e2e/specs/httpCache/checklists.cy.js
index f0dd208a9b..a8515d6bde 100644
--- a/e2e/specs/httpCache/checklists.cy.js
+++ b/e2e/specs/httpCache/checklists.cy.js
@@ -5,15 +5,18 @@ const collectionXKeys =
   /* campCollaboration for bipiUser */
   '146c0608237f ' +
   /* checklist entry */
-  'ebbd0c61eb85 ebbd0c61eb85#camp ' +
+  'ebbd0c61eb85 ' +
   /* collection URI (for detecting addition of new checklists) */
   '/api/camps/5d28f99890bc/checklists'
 
 describe('cache test: /camps/checklists', () => {
+  beforeEach(() => {
+    cy.wrap(Cypress.session.clearAllSavedSessions())
+  })
+
   it('caches /camp/{campId}/checklists separately for each login', () => {
     const uri = `/api/camps/${basiskursCampId}/checklists`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
@@ -36,7 +39,6 @@ describe('cache test: /camps/checklists', () => {
     const uri = `/api/camps/${basiskursCampId}/checklists`
 
     // bring data into defined state
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
     cy.apiPatch('/api/checklists/ebbd0c61eb85', {
       name: 'Training targets',
@@ -62,7 +64,6 @@ describe('cache test: /camps/checklists', () => {
     () => {
       const uri = `/api/camps/${basiskursCampId}/checklists`
 
-      Cypress.session.clearAllSavedSessions()
       cy.login(bipiUser)
 
       // warm up cache
diff --git a/e2e/specs/httpCache/content-types.cy.js b/e2e/specs/httpCache/content-types.cy.js
index f39c708170..8e8c0b48b7 100644
--- a/e2e/specs/httpCache/content-types.cy.js
+++ b/e2e/specs/httpCache/content-types.cy.js
@@ -6,10 +6,13 @@ const collectionXKeys =
   'a4211c11211c c462edd869f3 5e2028c55ee4 a4211c112939 f17470519474 1a0f84e322c8 3ef17bd1df72 4f0c657fecef 44dcc7493c65 cfccaecd4bad 318e064ea0c9 /api/content_types'
 
 describe('cache test: /content-types', () => {
+  beforeEach(() => {
+    cy.wrap(Cypress.session.clearAllSavedSessions())
+  })
+
   it('caches collection separately for each login', () => {
     const uri = '/api/content_types'
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
@@ -32,7 +35,6 @@ describe('cache test: /content-types', () => {
     const contentTypeId = '318e064ea0c9'
     const uri = `/api/content_types/${contentTypeId}`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
diff --git a/e2e/specs/httpCache/scheduleEntries.cy.js b/e2e/specs/httpCache/scheduleEntries.cy.js
index 027d47bcd0..8eabf2d146 100644
--- a/e2e/specs/httpCache/scheduleEntries.cy.js
+++ b/e2e/specs/httpCache/scheduleEntries.cy.js
@@ -15,21 +15,24 @@ const collectionXKeys =
   '10d8f02ce5b4 ' +
   /* scheduleEntries + links */
   /* the first scheduleEntry also includes the period id 7fa4564a5d5d */
-  'e68f4e47517a 7fa4564a5d5d e68f4e47517a#period e68f4e47517a#activity e68f4e47517a#day ' +
-  'f0883e931649 f0883e931649#period f0883e931649#activity f0883e931649#day ' +
-  '29c9e9a07d82 29c9e9a07d82#period 29c9e9a07d82#activity 29c9e9a07d82#day ' +
-  'ee85308a97d1 ee85308a97d1#period ee85308a97d1#activity ee85308a97d1#day ' +
-  'f08d69cae18a f08d69cae18a#period f08d69cae18a#activity f08d69cae18a#day ' +
-  '7e8086d94633 7e8086d94633#period 7e8086d94633#activity 7e8086d94633#day ' +
-  'f89a1501dbb6 f89a1501dbb6#period f89a1501dbb6#activity f89a1501dbb6#day ' +
+  'e68f4e47517a 7fa4564a5d5d e68f4e47517a#day ' +
+  'f0883e931649 f0883e931649#day ' +
+  '29c9e9a07d82 29c9e9a07d82#day ' +
+  'ee85308a97d1 ee85308a97d1#day ' +
+  'f08d69cae18a f08d69cae18a#day ' +
+  '7e8086d94633 7e8086d94633#day ' +
+  'f89a1501dbb6 f89a1501dbb6#day ' +
   /* collection URI (for detecting addition of new schedule entries) */
   '/api/periods/7fa4564a5d5d/schedule_entries'
 
 describe('cache test: /periods/{periodId}/scheduleEntries', () => {
+  beforeEach(() => {
+    cy.wrap(Cypress.session.clearAllSavedSessions())
+  })
+
   it('caches /periods/{periodId}/schedule_entries separately for each login', () => {
     const uri = `/api/periods/${skilagerPeriodId}/schedule_entries`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // first request is a cache miss
@@ -53,7 +56,6 @@ describe('cache test: /periods/{periodId}/scheduleEntries', () => {
     const scheduleEntryId = '12f34c89ce11'
 
     // bring data into defined state
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
     cy.apiPatch(`/api/schedule_entries/${scheduleEntryId}`, {
       start: '2025-05-10T16:00:00+00:00',
@@ -83,7 +85,6 @@ describe('cache test: /periods/{periodId}/scheduleEntries', () => {
   it('invalidates /periods/{periodId}/schedule_entries for new scheduleEntry', () => {
     const uri = `/api/periods/${grgrPeriodId}/schedule_entries`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -117,7 +118,6 @@ describe('cache test: /periods/{periodId}/scheduleEntries', () => {
     const uri2 = `/api/periods/${harrySecondPeriodId}/schedule_entries`
     const scheduleEntryId = '9a4173c9bb73'
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
@@ -156,7 +156,6 @@ describe('cache test: /periods/{periodId}/scheduleEntries', () => {
   it('invalidates /periods/{periodId}/schedule_entries when changing the period dates', () => {
     const uri = `/api/periods/${grgrPeriodId}/schedule_entries`
 
-    Cypress.session.clearAllSavedSessions()
     cy.login(bipiUser)
 
     // warm up cache
diff --git a/e2e/support/commands.js b/e2e/support/commands.js
index c2172d82fb..f82fa53583 100644
--- a/e2e/support/commands.js
+++ b/e2e/support/commands.js
@@ -27,7 +27,9 @@
 import 'cypress-wait-until'
 
 Cypress.Commands.add('login', (identifier) => {
-  cy.session(identifier, () => {
+  const randomSessionId =
+    Date.now().toString(36) + Math.random().toString(36).substring(2)
+  cy.session(randomSessionId, () => {
     cy.request({
       method: 'POST',
       url: Cypress.env('API_ROOT_URL') + '/authentication_token',