Merge remote-tracking branch 'origin/main' into feat/issue-837-relationship-edit-dates

# Conflicts:
#	.specify/rtm.md

backend/src/main/java/org/raddatz/familienarchiv/tag/RootTag.java

@@ -0,0 +1,13 @@
+package org.raddatz.familienarchiv.tag;
+
+import java.util.UUID;
+
+/**
+ * The root-ancestor view of a tag: its id, display name, and color token.
+ * Colors are stored only on root tags, so {@code color} is the authoritative token
+ * (one of {@link TagService#ALLOWED_TAG_COLORS}) or {@code null} when the root has none.
+ * Returned by {@link TagService#resolveRootTags} for read surfaces (the timeline chip,
+ * later the Thema buckets) that need a tag's theme without the entity graph.
+ */
+public record RootTag(UUID id, String name, String color) {
+}

backend/src/main/java/org/raddatz/familienarchiv/tag/TagService.java

@@ -175,6 +175,59 @@ public class TagService {
         });
     }
 
+    /**
+     * Resolves each given tag to its root ancestor, returning a {@link RootTag} (id, name, color
+     * token) keyed by the input tag's id. A root tag maps to itself; a child is walked to the
+     * ancestor with no parent via {@link TagRepository#findAncestorIds} (one CTE per distinct
+     * non-root tag, memoized) plus a single batched {@code findAllById}, so a timeline of many
+     * letters sharing few tags costs O(distinct tags) queries, never O(letters). The color comes
+     * from the resolved root's stored token (null when the root has none). Safe on detached tags.
+     */
+    public Map<UUID, RootTag> resolveRootTags(Collection<Tag> tags) {
+        if (tags == null || tags.isEmpty()) return Map.of();
+
+        Map<UUID, Tag> distinct = new LinkedHashMap<>();
+        for (Tag tag : tags) {
+            if (tag != null && tag.getId() != null) distinct.putIfAbsent(tag.getId(), tag);
+        }
+
+        Map<UUID, List<UUID>> ancestorIdsByTagId = new HashMap<>();
+        Set<UUID> idsToLoad = new HashSet<>();
+        for (Tag tag : distinct.values()) {
+            if (tag.getParentId() == null) continue;
+            List<UUID> ancestorIds = tagRepository.findAncestorIds(tag.getId());
+            ancestorIdsByTagId.put(tag.getId(), ancestorIds);
+            idsToLoad.addAll(ancestorIds);
+        }
+
+        Map<UUID, Tag> ancestorsById = idsToLoad.isEmpty() ? Map.of()
+                : tagRepository.findAllById(idsToLoad).stream()
+                        .collect(Collectors.toMap(Tag::getId, t -> t));
+
+        Map<UUID, RootTag> result = new HashMap<>();
+        for (Tag tag : distinct.values()) {
+            Tag root = resolveRoot(tag, ancestorIdsByTagId.get(tag.getId()), ancestorsById);
+            result.put(tag.getId(), new RootTag(root.getId(), root.getName(), root.getColor()));
+        }
+        return result;
+    }
+
+    private Tag resolveRoot(Tag tag, List<UUID> ancestorIds, Map<UUID, Tag> ancestorsById) {
+        if (tag.getParentId() == null) return tag;
+        if (ancestorIds != null) {
+            for (UUID ancestorId : ancestorIds) {
+                Tag ancestor = ancestorsById.get(ancestorId);
+                if (ancestor != null && ancestor.getParentId() == null) return ancestor;
+            }
+        }
+        // No null-parent ancestor surfaced — the parent is orphaned or the chain is deeper than the
+        // findAncestorIds CTE's depth guard. Fall back to the tag as its own root, but surface it:
+        // a silently mislabeled root would otherwise be invisible. UUIDs only (no tag names logged).
+        log.warn("Tag {} has parent {} but no root surfaced from its ancestry; "
+                + "treating it as its own root.", tag.getId(), tag.getParentId());
+        return tag;
+    }
+
     /**
      * For each tag name, returns the set of that tag's ID plus all descendant IDs.
      * Used by DocumentService to expand selected filter tags before applying AND/OR logic.

backend/src/main/java/org/raddatz/familienarchiv/timeline/TimelineEntryDTO.java

@@ -21,6 +21,13 @@ import java.util.UUID;
  * <p><b>Type field:</b> {@code null} for {@link Kind#LETTER} entries; frontend must not render
  * an event-type badge for letters.
  *
+ * <p><b>Root-tag fields ({@code rootTagId}/{@code rootTagName}/{@code rootTagColor}):</b> the
+ * letter's primary root tag — the root ancestor of its alphabetically-first assigned tag (#835).
+ * All three are {@code null} for non-{@link Kind#LETTER} entries and for letters with no tags;
+ * {@code rootTagColor} is additionally {@code null} when the resolved root carries no color token.
+ * They are deliberately NOT {@code @Schema(requiredMode = REQUIRED)} so the generated TypeScript
+ * types stay optional.
+ *
  * <p>Callers of {@code TimelineEventService.assembleDerivedEvents()} must independently enforce
  * {@code READ_ALL} authorization before invoking that method (see ADR-043).
  */
@@ -37,6 +44,9 @@ public record TimelineEntryDTO(
         UUID eventId,
         UUID documentId,
         List<UUID> linkedPersonIds,
-        DerivedEventType derivedType
+        DerivedEventType derivedType,
+        UUID rootTagId,
+        String rootTagName,
+        String rootTagColor
 ) {
 }

backend/src/main/java/org/raddatz/familienarchiv/timeline/TimelineEventService.java

@@ -266,7 +266,8 @@ public class TimelineEventService {
                         Kind.EVENT, p.getBirthDatePrecision(), true, "", "",
                         p.getBirthDate(), null,
                         p.getDisplayName(), EventType.PERSONAL,
-                        null, null, List.of(p.getId()), DerivedEventType.BIRTH))
+                        null, null, List.of(p.getId()), DerivedEventType.BIRTH,
+                        null, null, null))
                 .toList();
     }
 
@@ -277,7 +278,8 @@ public class TimelineEventService {
                         Kind.EVENT, p.getDeathDatePrecision(), true, "", "",
                         p.getDeathDate(), null,
                         p.getDisplayName(), EventType.PERSONAL,
-                        null, null, List.of(p.getId()), DerivedEventType.DEATH))
+                        null, null, List.of(p.getId()), DerivedEventType.DEATH,
+                        null, null, null))
                 .toList();
     }
 
@@ -301,7 +303,8 @@ public class TimelineEventService {
                         title, EventType.PERSONAL,
                         null, null,
                         List.of(r.getPerson().getId(), r.getRelatedPerson().getId()),
-                        DerivedEventType.MARRIAGE));
+                        DerivedEventType.MARRIAGE,
+                        null, null, null));
             }
         }
         return result;

backend/src/main/java/org/raddatz/familienarchiv/timeline/TimelineService.java

@@ -10,12 +10,16 @@ import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.exception.ErrorCode;
 import org.raddatz.familienarchiv.person.Person;
 import org.raddatz.familienarchiv.person.PersonService;
+import org.raddatz.familienarchiv.tag.RootTag;
+import org.raddatz.familienarchiv.tag.Tag;
+import org.raddatz.familienarchiv.tag.TagService;
 
 import org.springframework.stereotype.Service;
 import org.springframework.transaction.annotation.Transactional;
 
 import java.util.ArrayList;
 import java.util.Comparator;
+import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
@@ -52,6 +56,7 @@ public class TimelineService {
     private final TimelineEventService timelineEventService;
     private final DocumentService documentService;
     private final PersonService personService;
+    private final TagService tagService;
 
     /**
      * Assembles the timeline for the given filter. All filters are ANDed.
@@ -95,11 +100,15 @@ public class TimelineService {
         }
 
         // ── letters ─────────────────────────────────────────────────────────
-        List<Document> docs = fetchDocuments(filter.personId());
-        for (Document doc : docs) {
+        List<Document> letters = new ArrayList<>();
+        for (Document doc : fetchDocuments(filter.personId())) {
             if (!passesLetterGenerationFilter(doc, genPersonIds)) continue;
             if (!passesYearFilter(doc.getDocumentDate(), doc.getMetaDatePrecision(), filter)) continue;
-            entries.add(mapDocument(doc));
+            letters.add(doc);
+        }
+        Map<UUID, RootTag> rootByDocId = resolveLetterRootTags(letters);
+        for (Document doc : letters) {
+            entries.add(mapDocument(doc, rootByDocId));
         }
 
         return bucket(entries);
@@ -217,11 +226,15 @@ public class TimelineService {
                 ev.getId(),
                 null,
                 personIds,
+                null,
+                null,
+                null,
                 null
         );
     }
 
-    private TimelineEntryDTO mapDocument(Document doc) {
+    private TimelineEntryDTO mapDocument(Document doc, Map<UUID, RootTag> rootByDocId) {
+        RootTag root = rootByDocId.get(doc.getId());
         return new TimelineEntryDTO(
                 Kind.LETTER,
                 doc.getMetaDatePrecision(),
@@ -235,10 +248,47 @@ public class TimelineService {
                 null,
                 doc.getId(),
                 List.of(),
-                null
+                null,
+                root == null ? null : root.id(),
+                root == null ? null : root.name(),
+                root == null ? null : root.color()
         );
     }
 
+    /**
+     * Resolves each letter's primary root tag in one batched pass, keyed by document id — no
+     * per-letter N+1: each letter contributes only its alphabetically-first assigned tag (#835),
+     * so the {@code min()} scan over a letter's tag set runs exactly once here (not again at map
+     * time), and {@link TagService#resolveRootTags} memoizes the ancestry walk per distinct tag.
+     */
+    private Map<UUID, RootTag> resolveLetterRootTags(List<Document> letters) {
+        Map<UUID, Tag> primaryByDocId = new LinkedHashMap<>();
+        for (Document doc : letters) {
+            Tag primary = primaryTag(doc);
+            if (primary != null) primaryByDocId.put(doc.getId(), primary);
+        }
+        if (primaryByDocId.isEmpty()) return Map.of();
+
+        Map<UUID, RootTag> rootByTagId =
+                tagService.resolveRootTags(new ArrayList<>(primaryByDocId.values()));
+        Map<UUID, RootTag> rootByDocId = new HashMap<>();
+        primaryByDocId.forEach((docId, primary) -> {
+            RootTag root = rootByTagId.get(primary.getId());
+            if (root != null) rootByDocId.put(docId, root);
+        });
+        return rootByDocId;
+    }
+
+    /** A letter's primary tag: the alphabetically-first of its assigned tags by name (#835). */
+    private static Tag primaryTag(Document doc) {
+        Set<Tag> tags = doc.getTags();
+        if (tags == null || tags.isEmpty()) return null;
+        return tags.stream()
+                .filter(t -> t.getName() != null)
+                .min(Comparator.comparing(Tag::getName))
+                .orElse(null);
+    }
+
     private String resolveSenderName(Document doc) {
         if (doc.getSender() != null) return doc.getSender().getDisplayName();
         String text = doc.getSenderText();

backend/src/test/java/org/raddatz/familienarchiv/tag/TagServiceIntegrationTest.java

@@ -0,0 +1,61 @@
+package org.raddatz.familienarchiv.tag;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.raddatz.familienarchiv.PostgresContainerConfig;
+import org.raddatz.familienarchiv.config.FlywayConfig;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.data.jpa.test.autoconfigure.DataJpaTest;
+import org.springframework.boot.jdbc.test.autoconfigure.AutoConfigureTestDatabase;
+import org.springframework.context.annotation.Import;
+
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Real-Postgres proof that {@link TagService#resolveRootTags} walks a persisted tag chain to its
+ * true root through the recursive-CTE {@link TagRepository#findAncestorIds}. The CTE cannot run on
+ * H2, so this uses {@code postgres:16-alpine} via Testcontainers. Exhaustive case coverage lives in
+ * {@link TagServiceTest} (mocked); this pins the DB-dependent ancestry walk (issue #835, REQ-003/004).
+ */
+@DataJpaTest
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+@Import({PostgresContainerConfig.class, FlywayConfig.class})
+class TagServiceIntegrationTest {
+
+    @Autowired private TagRepository tagRepository;
+    private TagService tagService;
+
+    @BeforeEach
+    void setUp() {
+        tagService = new TagService(tagRepository);
+    }
+
+    private Tag tag(String name, String color, UUID parentId) {
+        return tagRepository.save(Tag.builder().name(name).color(color).parentId(parentId).build());
+    }
+
+    @Test
+    void resolveRootTags_walksPersistedChainToRoot_withRootColor() {
+        // leaf → mid → root resolves to the root's (id, name, color) via the real recursive CTE.
+        Tag root = tag("Krieg", "sienna", null);
+        Tag mid = tag("Feldpost", null, root.getId());
+        Tag leaf = tag("Briefe von der Front", null, mid.getId());
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(leaf));
+
+        assertThat(result.get(leaf.getId())).isEqualTo(new RootTag(root.getId(), "Krieg", "sienna"));
+    }
+
+    @Test
+    void resolveRootTags_returnsRootItself_forPersistedRoot() {
+        Tag root = tag("Weihnachten", "amber", null);
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(root));
+
+        assertThat(result.get(root.getId())).isEqualTo(new RootTag(root.getId(), "Weihnachten", "amber"));
+    }
+}

backend/src/test/java/org/raddatz/familienarchiv/tag/TagServiceTest.java

@@ -12,6 +12,7 @@ import org.raddatz.familienarchiv.tag.Tag;
 import org.raddatz.familienarchiv.tag.TagRepository;
 
 import java.util.List;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.UUID;
@@ -450,6 +451,74 @@ class TagServiceTest {
         assertThat(child2.getColor()).isEqualTo("sienna");
     }
 
+    // ─── resolveRootTags ───────────────────────────────────────────────────────
+
+    @Test
+    void resolveRootTags_returnsTagItself_whenTagIsRoot() {
+        // REQ-003/004: a root tag (no parent) is its own primary root — no ancestry walk, no load.
+        Tag root = Tag.builder().id(UUID.randomUUID()).name("Krieg").color("sienna").build();
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(root));
+
+        assertThat(result.get(root.getId())).isEqualTo(new RootTag(root.getId(), "Krieg", "sienna"));
+        verify(tagRepository, never()).findAncestorIds(any());
+        verify(tagRepository, never()).findAllById(any());
+    }
+
+    @Test
+    void resolveRootTags_walksChildToRoot_withRootColor() {
+        // REQ-003/004: a nested child resolves to its root's id/name/color via one CTE + one batch.
+        UUID rootId = UUID.randomUUID();
+        UUID midId = UUID.randomUUID();
+        Tag rootTag = Tag.builder().id(rootId).name("Krieg").color("sienna").build();
+        Tag mid = Tag.builder().id(midId).name("Feldpost").parentId(rootId).build();
+        Tag child = Tag.builder().id(UUID.randomUUID()).name("Briefe von der Front").parentId(midId).build();
+        when(tagRepository.findAncestorIds(child.getId())).thenReturn(List.of(midId, rootId));
+        when(tagRepository.findAllById(Set.of(midId, rootId))).thenReturn(List.of(mid, rootTag));
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(child));
+
+        assertThat(result.get(child.getId())).isEqualTo(new RootTag(rootId, "Krieg", "sienna"));
+    }
+
+    @Test
+    void resolveRootTags_memoizesPerDistinctTag_noNPlusOne() {
+        // REQ-004: two letters sharing one tag id ⇒ a single findAncestorIds + a single batch load.
+        UUID rootId = UUID.randomUUID();
+        UUID childId = UUID.randomUUID();
+        Tag rootTag = Tag.builder().id(rootId).name("Krieg").color("sienna").build();
+        Tag childA = Tag.builder().id(childId).name("Front").parentId(rootId).build();
+        Tag childB = Tag.builder().id(childId).name("Front").parentId(rootId).build();
+        when(tagRepository.findAncestorIds(childId)).thenReturn(List.of(rootId));
+        when(tagRepository.findAllById(Set.of(rootId))).thenReturn(List.of(rootTag));
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(childA, childB));
+
+        assertThat(result.get(childId)).isEqualTo(new RootTag(rootId, "Krieg", "sienna"));
+        verify(tagRepository, times(1)).findAncestorIds(childId);
+        verify(tagRepository, times(1)).findAllById(any());
+    }
+
+    @Test
+    void resolveRootTags_returnsNullColor_whenRootHasNoColor() {
+        // REQ-007: a colorless root yields RootTag.color() == null (frontend renders a neutral chip).
+        UUID rootId = UUID.randomUUID();
+        Tag rootTag = Tag.builder().id(rootId).name("Allgemein").build();
+        Tag child = Tag.builder().id(UUID.randomUUID()).name("Notiz").parentId(rootId).build();
+        when(tagRepository.findAncestorIds(child.getId())).thenReturn(List.of(rootId));
+        when(tagRepository.findAllById(Set.of(rootId))).thenReturn(List.of(rootTag));
+
+        Map<UUID, RootTag> result = tagService.resolveRootTags(List.of(child));
+
+        assertThat(result.get(child.getId())).isEqualTo(new RootTag(rootId, "Allgemein", null));
+    }
+
+    @Test
+    void resolveRootTags_returnsEmptyMap_forEmptyInput() {
+        assertThat(tagService.resolveRootTags(List.of())).isEmpty();
+        verify(tagRepository, never()).findAncestorIds(any());
+    }
+
     // ─── mergeTags ────────────────────────────────────────────────────────────
 
     @Test

backend/src/test/java/org/raddatz/familienarchiv/timeline/TimelineServiceTest.java

@@ -11,13 +11,19 @@ import org.raddatz.familienarchiv.document.DocumentService;
 import org.raddatz.familienarchiv.exception.DomainException;
 import org.raddatz.familienarchiv.person.Person;
 import org.raddatz.familienarchiv.person.PersonService;
+import org.raddatz.familienarchiv.tag.RootTag;
+import org.raddatz.familienarchiv.tag.Tag;
+import org.raddatz.familienarchiv.tag.TagService;
 
 import java.time.LocalDate;
+import java.util.HashSet;
 import java.util.List;
+import java.util.Map;
 import java.util.Set;
 import java.util.UUID;
 
 import static org.assertj.core.api.Assertions.*;
+import static org.mockito.ArgumentMatchers.anyList;
 import static org.mockito.Mockito.*;
 
 @ExtendWith(MockitoExtension.class)
@@ -27,6 +33,7 @@ class TimelineServiceTest {
     @Mock TimelineEventService timelineEventService;
     @Mock DocumentService documentService;
     @Mock PersonService personService;
+    @Mock TagService tagService;
 
     @InjectMocks TimelineService timelineService;
 
@@ -61,9 +68,11 @@ class TimelineServiceTest {
         UUID id1 = UUID.fromString("00000000-0000-0000-0000-000000000001");
         UUID id2 = UUID.fromString("00000000-0000-0000-0000-000000000002");
         var e1 = new TimelineEntryDTO(Kind.LETTER, DatePrecision.DAY, false, "", "",
-                LocalDate.of(1914, 7, 28), null, "Same Title", null, null, id1, List.of(), null);
+                LocalDate.of(1914, 7, 28), null, "Same Title", null, null, id1, List.of(), null,
+                null, null, null);
         var e2 = new TimelineEntryDTO(Kind.LETTER, DatePrecision.DAY, false, "", "",
-                LocalDate.of(1914, 7, 28), null, "Same Title", null, null, id2, List.of(), null);
+                LocalDate.of(1914, 7, 28), null, "Same Title", null, null, id2, List.of(), null,
+                null, null, null);
 
         var sorted = List.of(e2, e1).stream()
                 .sorted(TimelineService.WITHIN_BAND_ORDER)
@@ -423,13 +432,98 @@ class TimelineServiceTest {
 
     // ─── Helpers ─────────────────────────────────────────────────────────────
 
+    // ─── root-tag chip enrichment (#835) ─────────────────────────────────────
+
+    @Test
+    void letter_with_tags_carries_its_primary_root_tag() {
+        // REQ-003/006: the primary tag is the root ancestor of the alphabetically-first
+        // assigned tag ("Briefe von der Front" < "Zeitung"), resolved to root "Krieg".
+        UUID kriegId = UUID.randomUUID();
+        Tag front = Tag.builder().id(UUID.randomUUID()).name("Briefe von der Front").parentId(kriegId).build();
+        Tag zeitung = Tag.builder().id(UUID.randomUUID()).name("Zeitung").build();
+        Document doc = docWithTags(LocalDate.of(1916, 5, 1), DatePrecision.MONTH, front, zeitung);
+        when(eventRepository.findAll()).thenReturn(List.of());
+        when(timelineEventService.assembleDerivedEvents()).thenReturn(List.of());
+        when(documentService.getAllForTimeline()).thenReturn(List.of(doc));
+        when(tagService.resolveRootTags(anyList()))
+                .thenReturn(Map.of(front.getId(), new RootTag(kriegId, "Krieg", "sienna")));
+
+        TimelineEntryDTO entry = onlyLetterEntry(timelineService.assemble(noFilters()));
+
+        assertThat(entry.rootTagId()).isEqualTo(kriegId);
+        assertThat(entry.rootTagName()).isEqualTo("Krieg");
+        assertThat(entry.rootTagColor()).isEqualTo("sienna");
+    }
+
+    @Test
+    void untagged_letter_has_no_root_tag_fields() {
+        // REQ-005: a letter with no tags carries null id/name/color — and never hits TagService.
+        Document doc = docWithDate(LocalDate.of(1909, 3, 1), DatePrecision.MONTH);
+        when(eventRepository.findAll()).thenReturn(List.of());
+        when(timelineEventService.assembleDerivedEvents()).thenReturn(List.of());
+        when(documentService.getAllForTimeline()).thenReturn(List.of(doc));
+
+        TimelineEntryDTO entry = onlyLetterEntry(timelineService.assemble(noFilters()));
+
+        assertThat(entry.rootTagId()).isNull();
+        assertThat(entry.rootTagName()).isNull();
+        assertThat(entry.rootTagColor()).isNull();
+        verify(tagService, never()).resolveRootTags(anyList());
+    }
+
+    @Test
+    void letter_primary_root_without_color_yields_null_color() {
+        // REQ-007: a colorless root → rootTagColor null, id+name still present (neutral chip).
+        UUID rootId = UUID.randomUUID();
+        Tag allgemein = Tag.builder().id(rootId).name("Allgemein").build();
+        Document doc = docWithTags(LocalDate.of(1910, 2, 1), DatePrecision.MONTH, allgemein);
+        when(eventRepository.findAll()).thenReturn(List.of());
+        when(timelineEventService.assembleDerivedEvents()).thenReturn(List.of());
+        when(documentService.getAllForTimeline()).thenReturn(List.of(doc));
+        when(tagService.resolveRootTags(anyList()))
+                .thenReturn(Map.of(rootId, new RootTag(rootId, "Allgemein", null)));
+
+        TimelineEntryDTO entry = onlyLetterEntry(timelineService.assemble(noFilters()));
+
+        assertThat(entry.rootTagId()).isEqualTo(rootId);
+        assertThat(entry.rootTagName()).isEqualTo("Allgemein");
+        assertThat(entry.rootTagColor()).isNull();
+    }
+
+    @Test
+    void root_tags_resolved_in_a_single_batched_pass() {
+        // REQ-004: many letters → exactly one resolveRootTags call (no per-letter N+1).
+        UUID kriegId = UUID.randomUUID();
+        Tag krieg = Tag.builder().id(kriegId).name("Krieg").color("sienna").build();
+        Tag weihnachten = Tag.builder().id(UUID.randomUUID()).name("Weihnachten").color("amber").build();
+        Document a = docWithTags(LocalDate.of(1915, 1, 1), DatePrecision.YEAR, krieg);
+        Document b = docWithTags(LocalDate.of(1916, 12, 1), DatePrecision.MONTH, weihnachten);
+        Document c = docWithTags(LocalDate.of(1917, 1, 1), DatePrecision.YEAR, krieg);
+        when(eventRepository.findAll()).thenReturn(List.of());
+        when(timelineEventService.assembleDerivedEvents()).thenReturn(List.of());
+        when(documentService.getAllForTimeline()).thenReturn(List.of(a, b, c));
+        when(tagService.resolveRootTags(anyList())).thenReturn(Map.of(
+                kriegId, new RootTag(kriegId, "Krieg", "sienna"),
+                weihnachten.getId(), new RootTag(weihnachten.getId(), "Weihnachten", "amber")));
+
+        timelineService.assemble(noFilters());
+
+        verify(tagService, times(1)).resolveRootTags(anyList());
+    }
+
+    private static TimelineEntryDTO onlyLetterEntry(TimelineDTO result) {
+        assertThat(result.years()).hasSize(1);
+        return result.years().get(0).entries().get(0);
+    }
+
     private static TimelineFilter noFilters() {
         return new TimelineFilter(null, null, null, null, null);
     }
 
     private static TimelineEntryDTO letter(LocalDate date, DatePrecision precision, String title) {
         return new TimelineEntryDTO(Kind.LETTER, precision, false, "", "",
-                date, null, title, null, null, UUID.randomUUID(), List.of(), null);
+                date, null, title, null, null, UUID.randomUUID(), List.of(), null,
+                null, null, null);
     }
 
     private static Document docWithDate(LocalDate date, DatePrecision precision) {
@@ -437,6 +531,12 @@ class TimelineServiceTest {
                 .metaDatePrecision(precision).documentDate(date).build();
     }
 
+    private static Document docWithTags(LocalDate date, DatePrecision precision, Tag... tags) {
+        return Document.builder().id(UUID.randomUUID()).title("Brief")
+                .metaDatePrecision(precision).documentDate(date)
+                .tags(new HashSet<>(Set.of(tags))).build();
+    }
+
     private static Document docWithDate(LocalDate date, DatePrecision precision, String title) {
         return Document.builder().id(UUID.randomUUID()).title(title)
                 .metaDatePrecision(precision).documentDate(date).build();