diff --git a/lib/composer/composer/autoload_classmap.php b/lib/composer/composer/autoload_classmap.php
index 6a9a458507cce..b817fcef17792 100644
--- a/lib/composer/composer/autoload_classmap.php
+++ b/lib/composer/composer/autoload_classmap.php
@@ -1072,10 +1072,12 @@
     'OCP\\TaskProcessing\\TaskTypes\\TextToTextSummary' => $baseDir . '/lib/public/TaskProcessing/TaskTypes/TextToTextSummary.php',
     'OCP\\TaskProcessing\\TaskTypes\\TextToTextTopics' => $baseDir . '/lib/public/TaskProcessing/TaskTypes/TextToTextTopics.php',
     'OCP\\TaskProcessing\\TaskTypes\\TextToTextTranslate' => $baseDir . '/lib/public/TaskProcessing/TaskTypes/TextToTextTranslate.php',
+    'OCP\\Teams\\ITeamActivityResourceProvider' => $baseDir . '/lib/public/Teams/ITeamActivityResourceProvider.php',
     'OCP\\Teams\\ITeamFolderProvider' => $baseDir . '/lib/public/Teams/ITeamFolderProvider.php',
     'OCP\\Teams\\ITeamManager' => $baseDir . '/lib/public/Teams/ITeamManager.php',
     'OCP\\Teams\\ITeamResourceProvider' => $baseDir . '/lib/public/Teams/ITeamResourceProvider.php',
     'OCP\\Teams\\Team' => $baseDir . '/lib/public/Teams/Team.php',
+    'OCP\\Teams\\TeamActivityScope' => $baseDir . '/lib/public/Teams/TeamActivityScope.php',
     'OCP\\Teams\\TeamFolder' => $baseDir . '/lib/public/Teams/TeamFolder.php',
     'OCP\\Teams\\TeamResource' => $baseDir . '/lib/public/Teams/TeamResource.php',
     'OCP\\Template' => $baseDir . '/lib/public/Template.php',
diff --git a/lib/composer/composer/autoload_static.php b/lib/composer/composer/autoload_static.php
index fabed32790e47..9ccf019fe3810 100644
--- a/lib/composer/composer/autoload_static.php
+++ b/lib/composer/composer/autoload_static.php
@@ -1118,10 +1118,12 @@ class ComposerStaticInit749170dad3f5e7f9ca158f5a9f04f6a2
         'OCP\\TaskProcessing\\TaskTypes\\TextToTextSummary' => __DIR__ . '/../../..' . '/lib/public/TaskProcessing/TaskTypes/TextToTextSummary.php',
         'OCP\\TaskProcessing\\TaskTypes\\TextToTextTopics' => __DIR__ . '/../../..' . '/lib/public/TaskProcessing/TaskTypes/TextToTextTopics.php',
         'OCP\\TaskProcessing\\TaskTypes\\TextToTextTranslate' => __DIR__ . '/../../..' . '/lib/public/TaskProcessing/TaskTypes/TextToTextTranslate.php',
+        'OCP\\Teams\\ITeamActivityResourceProvider' => __DIR__ . '/../../..' . '/lib/public/Teams/ITeamActivityResourceProvider.php',
         'OCP\\Teams\\ITeamFolderProvider' => __DIR__ . '/../../..' . '/lib/public/Teams/ITeamFolderProvider.php',
         'OCP\\Teams\\ITeamManager' => __DIR__ . '/../../..' . '/lib/public/Teams/ITeamManager.php',
         'OCP\\Teams\\ITeamResourceProvider' => __DIR__ . '/../../..' . '/lib/public/Teams/ITeamResourceProvider.php',
         'OCP\\Teams\\Team' => __DIR__ . '/../../..' . '/lib/public/Teams/Team.php',
+        'OCP\\Teams\\TeamActivityScope' => __DIR__ . '/../../..' . '/lib/public/Teams/TeamActivityScope.php',
         'OCP\\Teams\\TeamFolder' => __DIR__ . '/../../..' . '/lib/public/Teams/TeamFolder.php',
         'OCP\\Teams\\TeamResource' => __DIR__ . '/../../..' . '/lib/public/Teams/TeamResource.php',
         'OCP\\Template' => __DIR__ . '/../../..' . '/lib/public/Template.php',
diff --git a/lib/public/Teams/ITeamActivityResourceProvider.php b/lib/public/Teams/ITeamActivityResourceProvider.php
new file mode 100644
index 0000000000000..cc24c4e25e299
--- /dev/null
+++ b/lib/public/Teams/ITeamActivityResourceProvider.php
@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Teams;
+
+use OCP\AppFramework\Attribute\Implementable;
+
+/**
+ * An optional Team resource provider capability for Team Activity.
+ *
+ * @since 36.0.0
+ */
+#[Implementable(since: '36.0.0')]
+interface ITeamActivityResourceProvider extends ITeamResourceProvider {
+	/**
+	 * Resolve Team resources into Activity objects visible to the current user.
+	 *
+	 * @param list<TeamResource> $resources Resources from this provider shared with the Team
+	 * @param string $userId The user the activity scopes are resolved for
+	 * @return list<TeamActivityScope>
+	 * @since 36.0.0
+	 */
+	public function getActivityScopes(array $resources, string $userId): array;
+}
diff --git a/lib/public/Teams/TeamActivityScope.php b/lib/public/Teams/TeamActivityScope.php
new file mode 100644
index 0000000000000..296b0d3be7096
--- /dev/null
+++ b/lib/public/Teams/TeamActivityScope.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCP\Teams;
+
+use OCP\AppFramework\Attribute\Consumable;
+
+/**
+ * A set of Activity objects belonging to Team resources.
+ *
+ * @since 36.0.0
+ */
+#[Consumable(since: '36.0.0')]
+final readonly class TeamActivityScope {
+	/** @var list<positive-int> */
+	private array $objectIds;
+
+	/**
+	 * @param list<positive-int> $objectIds
+	 * @param non-empty-string $objectType
+	 * @since 36.0.0
+	 */
+	public function __construct(
+		private string $objectType,
+		array $objectIds,
+	) {
+		$this->objectIds = array_values(array_unique($objectIds));
+	}
+
+	/**
+	 * @return non-empty-string
+	 * @since 36.0.0
+	 */
+	public function getObjectType(): string {
+		return $this->objectType;
+	}
+
+	/**
+	 * @return list<positive-int>
+	 * @since 36.0.0
+	 */
+	public function getObjectIds(): array {
+		return $this->objectIds;
+	}
+}
diff --git a/lib/public/Teams/TeamFolder.php b/lib/public/Teams/TeamFolder.php
index 30f6c85f2f196..afd366460a8af 100644
--- a/lib/public/Teams/TeamFolder.php
+++ b/lib/public/Teams/TeamFolder.php
@@ -25,6 +25,7 @@ public function __construct(
 		private int $id,
 		private string $mountPoint,
 		private ?int $quota = null,
+		private ?int $rootFileId = null,
 	) {
 	}
 
@@ -53,7 +54,16 @@ public function getQuota(): ?int {
 	}
 
 	/**
-	 * @return array{id: int, quota: int|null, mountPoint: string}
+	 * Return the filecache ID of the folder's root, when exposed by the provider.
+	 *
+	 * @since 36.0.0
+	 */
+	public function getRootFileId(): ?int {
+		return $this->rootFileId;
+	}
+
+	/**
+	 * @return array{id: int, quota: int|null, mountPoint: string, rootFileId: int|null}
 	 * @since 35.0.0
 	 */
 	#[\Override]
@@ -62,6 +72,7 @@ public function jsonSerialize(): array {
 			'id' => $this->id,
 			'quota' => $this->quota,
 			'mountPoint' => $this->mountPoint,
+			'rootFileId' => $this->rootFileId,
 		];
 	}
 }
diff --git a/tests/lib/Teams/TeamActivityScopeTest.php b/tests/lib/Teams/TeamActivityScopeTest.php
new file mode 100644
index 0000000000000..ec5a519210ded
--- /dev/null
+++ b/tests/lib/Teams/TeamActivityScopeTest.php
@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace Test\Teams;
+
+use OCP\AppFramework\Attribute\Consumable;
+use OCP\AppFramework\Attribute\Implementable;
+use OCP\Teams\ITeamActivityResourceProvider;
+use OCP\Teams\TeamActivityScope;
+use Test\TestCase;
+
+class TeamActivityScopeTest extends TestCase {
+	public function testGettersReturnConstructorValues(): void {
+		$scope = new TeamActivityScope('files', [1, 2, 3]);
+
+		$this->assertSame('files', $scope->getObjectType());
+		$this->assertSame([1, 2, 3], $scope->getObjectIds());
+	}
+
+	public function testDeduplicatesObjectIds(): void {
+		$scope = new TeamActivityScope('files', [1, 2, 2, 3, 1]);
+
+		$this->assertSame([1, 2, 3], $scope->getObjectIds());
+	}
+
+	public function testAllowsEmptyObjectIds(): void {
+		$scope = new TeamActivityScope('files', []);
+
+		$this->assertSame([], $scope->getObjectIds());
+	}
+
+	public function testReturnedObjectIdsDoNotMutateScope(): void {
+		$scope = new TeamActivityScope('files', [1, 2, 3]);
+		$objectIds = $scope->getObjectIds();
+		$objectIds[] = 4;
+
+		$this->assertSame([1, 2, 3], $scope->getObjectIds());
+	}
+
+	public function testScopeIsFinalAndReadonly(): void {
+		$class = new \ReflectionClass(TeamActivityScope::class);
+
+		$this->assertTrue($class->isFinal());
+		$this->assertTrue($class->isReadOnly());
+	}
+
+	public function testScopeIsConsumable(): void {
+		$class = new \ReflectionClass(TeamActivityScope::class);
+		$attributes = $class->getAttributes(Consumable::class);
+
+		$this->assertCount(1, $attributes);
+		$this->assertSame('36.0.0', $attributes[0]->newInstance()->getSince());
+	}
+
+	public function testProviderIsImplementable(): void {
+		$class = new \ReflectionClass(ITeamActivityResourceProvider::class);
+		$attributes = $class->getAttributes(Implementable::class);
+
+		$this->assertCount(1, $attributes);
+		$this->assertSame('36.0.0', $attributes[0]->newInstance()->getSince());
+	}
+}
diff --git a/tests/lib/Teams/TeamFolderTest.php b/tests/lib/Teams/TeamFolderTest.php
index bc062b98d61e2..11349695e6620 100644
--- a/tests/lib/Teams/TeamFolderTest.php
+++ b/tests/lib/Teams/TeamFolderTest.php
@@ -19,13 +19,21 @@ public function testSerializesFolderIdentity(): void {
 		$this->assertSame(42, $folder->getId());
 		$this->assertSame('Engineering', $folder->getMountPoint());
 		$this->assertNull($folder->getQuota());
-		$this->assertSame(['id' => 42, 'quota' => null, 'mountPoint' => 'Engineering'], $folder->jsonSerialize());
+		$this->assertNull($folder->getRootFileId());
+		$this->assertSame(['id' => 42, 'quota' => null, 'mountPoint' => 'Engineering', 'rootFileId' => null], $folder->jsonSerialize());
 	}
 
 	public function testSerializesFolderQuota(): void {
 		$folder = new TeamFolder(42, 'Engineering', 1024);
 
 		$this->assertSame(1024, $folder->getQuota());
-		$this->assertSame(['id' => 42, 'quota' => 1024, 'mountPoint' => 'Engineering'], $folder->jsonSerialize());
+		$this->assertSame(['id' => 42, 'quota' => 1024, 'mountPoint' => 'Engineering', 'rootFileId' => null], $folder->jsonSerialize());
+	}
+
+	public function testSerializesFolderRootFileId(): void {
+		$folder = new TeamFolder(42, 'Engineering', 1024, 1337);
+
+		$this->assertSame(1337, $folder->getRootFileId());
+		$this->assertSame(['id' => 42, 'quota' => 1024, 'mountPoint' => 'Engineering', 'rootFileId' => 1337], $folder->jsonSerialize());
 	}
 }