diff --git a/frontend/src/lib/generated/api.ts b/frontend/src/lib/generated/api.ts
index 3a858315..e2cb6a0e 100644
--- a/frontend/src/lib/generated/api.ts
+++ b/frontend/src/lib/generated/api.ts
@@ -2038,6 +2038,7 @@ export interface components {
             /** Format: date-time */
             happenedAt: string;
             youMentioned: boolean;
+            youParticipated: boolean;
             /** Format: int32 */
             count: number;
             /** Format: date-time */
diff --git a/frontend/src/routes/chronik/feedFilters.test.ts b/frontend/src/routes/chronik/feedFilters.test.ts
new file mode 100644
index 00000000..391d2140
--- /dev/null
+++ b/frontend/src/routes/chronik/feedFilters.test.ts
@@ -0,0 +1,94 @@
+import { describe, expect, it } from 'vitest';
+import { filterFeed } from './feedFilters';
+import type { components } from '$lib/generated/api';
+
+type Item = components['schemas']['ActivityFeedItemDTO'];
+
+function makeItem(overrides: Partial<Item> = {}): Item {
+	return {
+		kind: 'FILE_UPLOADED',
+		documentId: 'd1',
+		documentTitle: 'Brief A',
+		happenedAt: '2026-04-20T10:00:00Z',
+		youMentioned: false,
+		youParticipated: false,
+		count: 1,
+		actor: null,
+		happenedAtUntil: null,
+		...overrides
+	};
+}
+
+describe('filterFeed', () => {
+	describe('alle', () => {
+		it('returns all items regardless of kind', () => {
+			const items = [
+				makeItem({ kind: 'FILE_UPLOADED' }),
+				makeItem({ kind: 'COMMENT_ADDED' }),
+				makeItem({ kind: 'MENTION_CREATED' })
+			];
+			expect(filterFeed(items, 'alle')).toHaveLength(3);
+		});
+	});
+
+	describe('fuer-dich', () => {
+		it('includes MENTION_CREATED items', () => {
+			const items = [makeItem({ kind: 'MENTION_CREATED' })];
+			expect(filterFeed(items, 'fuer-dich')).toHaveLength(1);
+		});
+
+		it('includes items where youMentioned is true', () => {
+			const items = [makeItem({ kind: 'COMMENT_ADDED', youMentioned: true })];
+			expect(filterFeed(items, 'fuer-dich')).toHaveLength(1);
+		});
+
+		it('includes items where youParticipated is true', () => {
+			const items = [makeItem({ kind: 'COMMENT_ADDED', youParticipated: true })];
+			expect(filterFeed(items, 'fuer-dich')).toHaveLength(1);
+		});
+
+		it('excludes FILE_UPLOADED with no participation', () => {
+			const items = [makeItem({ kind: 'FILE_UPLOADED' })];
+			expect(filterFeed(items, 'fuer-dich')).toHaveLength(0);
+		});
+
+		it('excludes COMMENT_ADDED with no mention and no participation', () => {
+			const items = [makeItem({ kind: 'COMMENT_ADDED' })];
+			expect(filterFeed(items, 'fuer-dich')).toHaveLength(0);
+		});
+	});
+
+	describe('hochgeladen', () => {
+		it('includes only FILE_UPLOADED items', () => {
+			const items = [
+				makeItem({ kind: 'FILE_UPLOADED' }),
+				makeItem({ kind: 'COMMENT_ADDED', youParticipated: true })
+			];
+			expect(filterFeed(items, 'hochgeladen')).toHaveLength(1);
+			expect(filterFeed(items, 'hochgeladen')[0].kind).toBe('FILE_UPLOADED');
+		});
+	});
+
+	describe('transkription', () => {
+		it('includes TEXT_SAVED, BLOCK_REVIEWED, ANNOTATION_CREATED', () => {
+			const items = [
+				makeItem({ kind: 'TEXT_SAVED' }),
+				makeItem({ kind: 'BLOCK_REVIEWED' }),
+				makeItem({ kind: 'ANNOTATION_CREATED' }),
+				makeItem({ kind: 'FILE_UPLOADED' })
+			];
+			expect(filterFeed(items, 'transkription')).toHaveLength(3);
+		});
+	});
+
+	describe('kommentare', () => {
+		it('includes COMMENT_ADDED and MENTION_CREATED', () => {
+			const items = [
+				makeItem({ kind: 'COMMENT_ADDED' }),
+				makeItem({ kind: 'MENTION_CREATED' }),
+				makeItem({ kind: 'FILE_UPLOADED' })
+			];
+			expect(filterFeed(items, 'kommentare')).toHaveLength(2);
+		});
+	});
+});
diff --git a/frontend/src/routes/chronik/feedFilters.ts b/frontend/src/routes/chronik/feedFilters.ts
new file mode 100644
index 00000000..ab66b5ab
--- /dev/null
+++ b/frontend/src/routes/chronik/feedFilters.ts
@@ -0,0 +1,27 @@
+import type { components } from '$lib/generated/api';
+import type { FilterValue } from './+page.server';
+
+type ActivityFeedItemDTO = components['schemas']['ActivityFeedItemDTO'];
+
+export function filterFeed(
+	items: ActivityFeedItemDTO[],
+	filter: FilterValue
+): ActivityFeedItemDTO[] {
+	switch (filter) {
+		case 'alle':
+			return items;
+		case 'fuer-dich':
+			return items.filter(
+				(i) => i.kind === 'MENTION_CREATED' || i.youMentioned || i.youParticipated
+			);
+		case 'hochgeladen':
+			return items.filter((i) => i.kind === 'FILE_UPLOADED');
+		case 'transkription':
+			return items.filter(
+				(i) =>
+					i.kind === 'TEXT_SAVED' || i.kind === 'BLOCK_REVIEWED' || i.kind === 'ANNOTATION_CREATED'
+			);
+		case 'kommentare':
+			return items.filter((i) => i.kind === 'COMMENT_ADDED' || i.kind === 'MENTION_CREATED');
+	}
+}