frontend/src/lib/timeline/YearBand.svelte

@@ -43,26 +43,53 @@ type Row =
 	| { t: 'event'; entry: TimelineEntryDTO }
 	| { t: 'letter'; entry: TimelineEntryDTO; side: 'left' | 'right' }
 	| { t: 'strip' }
-	| { t: 'bucket'; bucket: LetterBucketModel };
+	| { t: 'bucket'; bucket: LetterBucketModel; nested: boolean };
 
 const letters = $derived(year.entries.filter((e) => e.kind === 'LETTER'));
 const dense = $derived(isDense(letters.length));
-const grouped = $derived(groupingMode !== 'date');
 const bucketMode = $derived(groupingMode === 'thema' ? 'thema' : 'event');
 
 const rows = $derived.by<Row[]>(() => {
 	const out: Row[] = [];
-	if (grouped) {
-		// Events stay on the axis, identical to Datum mode (REQ-001); only the loose
-		// letters re-bundle into per-year buckets below them (REQ-003/004).
+
+	// Ereignis: events stay on the axis (REQ-001); each curated event's letters nest directly
+	// beneath its pill — the pill IS the header, so the title is never repeated. A cluster whose
+	// pill lives in another year band (or was filtered out) keeps its own header here, and the
+	// unlinked letters fall to the single "Weitere Briefe" bucket (REQ-003/006/019).
+	if (groupingMode === 'event') {
+		const buckets = bucketLetters(letters, 'event', eventLookup);
+		const hasPill = (bucketKey: string) =>
+			year.entries.some((e) => e.kind === 'EVENT' && `event:${e.eventId}` === bucketKey);
+		// Each pill renders, then its same-year cluster nests directly beneath it (no header).
 		for (const entry of year.entries) {
-			if (entry.kind === 'EVENT') out.push({ t: 'event', entry });
+			if (entry.kind !== 'EVENT') continue;
+			out.push({ t: 'event', entry });
+			const bucket = entry.eventId
+				? buckets.find((b) => b.kind === 'event' && b.key === `event:${entry.eventId}`)
+				: undefined;
+			if (bucket) out.push({ t: 'bucket', bucket, nested: true });
 		}
-		for (const bucket of bucketLetters(letters, bucketMode, eventLookup)) {
-			out.push({ t: 'bucket', bucket });
+		// Clusters whose pill is in another band keep their header; then the fallback, last.
+		for (const bucket of buckets) {
+			if (bucket.kind === 'fallback' || !hasPill(bucket.key)) {
+				out.push({ t: 'bucket', bucket, nested: false });
+			}
 		}
 		return out;
 	}
+
+	// Thema: events stay on the axis (REQ-001); loose letters re-bundle into per-year root-tag
+	// buckets below them (REQ-004) — no axis pill exists for a tag, so every bucket keeps a header.
+	if (groupingMode === 'thema') {
+		for (const entry of year.entries) {
+			if (entry.kind === 'EVENT') out.push({ t: 'event', entry });
+		}
+		for (const bucket of bucketLetters(letters, 'thema', eventLookup)) {
+			out.push({ t: 'bucket', bucket, nested: false });
+		}
+		return out;
+	}
+
 	let stripInserted = false;
 	let letterIndex = 0;
 	for (const entry of year.entries) {
@@ -110,7 +137,7 @@ function rowKey(row: Row): string {
 					<LetterCard entry={row.entry} />
 				</div>
 			{:else if row.t === 'bucket'}
-				<LetterBucket bucket={row.bucket} mode={bucketMode} />
+				<LetterBucket bucket={row.bucket} mode={bucketMode} year={year.year} nested={row.nested} />
 			{:else}
 				<YearLetterStrip letters={letters} year={year.year} />
 			{/if}

frontend/src/lib/timeline/YearBand.svelte.spec.ts

@@ -221,4 +221,43 @@ describe('YearBand — grouping modes (#827)', () => {
 		const chip = document.querySelector('[data-testid="bucket-header-chip"]');
 		expect(chip?.textContent).toContain('Krieg');
 	});
+
+	it('nests an event cluster under its pill in the same year without repeating the title (#827)', () => {
+		const pill = makeEntry({
+			kind: 'EVENT',
+			type: 'PERSONAL',
+			derived: false,
+			eventId: 'e1',
+			title: 'Ein gewaltiger Stadtbrand',
+			eventDate: '1916-07-06',
+			senderName: '',
+			receiverName: '',
+			documentId: undefined
+		});
+		const letter = makeEntry({ documentId: 'a', linkedEventId: 'e1', eventDate: '1916-07-06' });
+		render(YearBand, {
+			year: makeYear(1916, [pill, letter]),
+			groupingMode: 'event',
+			eventLookup: new Map([['e1', 'Ein gewaltiger Stadtbrand']])
+		});
+		// the title appears exactly once — on the axis pill, NOT also as a bucket header
+		const occurrences =
+			(document.body.textContent ?? '').split('Ein gewaltiger Stadtbrand').length - 1;
+		expect(occurrences).toBe(1);
+		// the letter is still clustered (nested under the pill) as the event-letter card
+		expect(document.querySelector('[data-testid="letter-bucket"]')).not.toBeNull();
+		expect(document.querySelector('a.lcard.ev')).not.toBeNull();
+	});
+
+	it('keeps a header on an event cluster whose pill is in another year (#827)', () => {
+		// the letter links to e1, but e1's pill lives in a different band — so the cluster
+		// keeps its own header here (no pill nearby to duplicate).
+		const letter = makeEntry({ documentId: 'a', linkedEventId: 'e1', eventDate: '1917-02-01' });
+		render(YearBand, {
+			year: makeYear(1917, [letter]),
+			groupingMode: 'event',
+			eventLookup: new Map([['e1', 'Briefe von der Front']])
+		});
+		expect(document.body.textContent).toContain('Briefe von der Front');
+	});
 });