diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentRepository.java b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentRepository.java
index 071f2276..1cfe26f6 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentRepository.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentRepository.java
@@ -57,6 +57,7 @@ public interface DocumentRepository extends JpaRepository<Document, UUID>, JpaSp
     @EntityGraph("Document.full")
     List<Document> findByReceiversId(UUID receiverId);
 
+
     // Callers access only doc.getTags() to mutate the set — receivers/sender not touched; no graph needed.
     List<Document> findByTags_Id(UUID tagId);
 
diff --git a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
index faa74367..6ce9ba6e 100644
--- a/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
+++ b/backend/src/main/java/org/raddatz/familienarchiv/document/DocumentService.java
@@ -1034,7 +1034,25 @@ public class DocumentService {
     }
 
     public DocumentSearchResult searchDocumentsByPersonId(UUID personId, LocalDate from, LocalDate to, Pageable pageable) {
-        throw new UnsupportedOperationException("Implemented in Task 12 — findBySenderOrReceiver JPQL");
+        Person person = personService.getById(personId);
+        Specification<Document> spec = buildPersonSpec(person, from, to);
+        Page<Document> page = documentRepository.findAll(spec, pageable);
+        List<DocumentListItem> items = enrichItems(page.getContent(), null);
+        return DocumentSearchResult.paged(items, pageable, page.getTotalElements());
+    }
+
+    private Specification<Document> buildPersonSpec(Person person, LocalDate from, LocalDate to) {
+        return (root, query, cb) -> {
+            if (query != null) query.distinct(true);
+            var receiversJoin = root.join("receivers", jakarta.persistence.criteria.JoinType.LEFT);
+            var senderPredicate = cb.equal(root.get("sender"), person);
+            var receiverPredicate = cb.equal(receiversJoin, person);
+            var personPredicate = cb.or(senderPredicate, receiverPredicate);
+            var predicates = new java.util.ArrayList<>(java.util.List.of(personPredicate));
+            if (from != null) predicates.add(cb.greaterThanOrEqualTo(root.get("documentDate"), from));
+            if (to != null) predicates.add(cb.lessThanOrEqualTo(root.get("documentDate"), to));
+            return cb.and(predicates.toArray(new jakarta.persistence.criteria.Predicate[0]));
+        };
     }
 
     public long getIncompleteCount() {
diff --git a/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentRepositoryTest.java b/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentRepositoryTest.java
index 234abbd8..eff82466 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentRepositoryTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/document/DocumentRepositoryTest.java
@@ -624,4 +624,88 @@ class DocumentRepositoryTest {
                 .reviewed(reviewed)
                 .build();
     }
+
+    // ─── searchDocumentsByPersonId (via Specification) ───────────────────────
+
+    private Page<Document> searchByPerson(Person person, LocalDate from, LocalDate to) {
+        Specification<Document> spec = (root, query, cb) -> {
+            if (query != null) query.distinct(true);
+            var receiversJoin = root.join("receivers", jakarta.persistence.criteria.JoinType.LEFT);
+            var personPredicate = cb.or(
+                    cb.equal(root.get("sender"), person),
+                    cb.equal(receiversJoin, person));
+            var predicates = new java.util.ArrayList<>(java.util.List.of(personPredicate));
+            if (from != null) predicates.add(cb.greaterThanOrEqualTo(root.get("documentDate"), from));
+            if (to != null) predicates.add(cb.lessThanOrEqualTo(root.get("documentDate"), to));
+            return cb.and(predicates.toArray(new jakarta.persistence.criteria.Predicate[0]));
+        };
+        return documentRepository.findAll(spec, PageRequest.of(0, 10));
+    }
+
+    @Test
+    void searchByPersonSpec_returnsDocument_whenPersonIsSender() {
+        Person person = personRepository.save(Person.builder().lastName("Raddatz").build());
+        Document doc = documentRepository.save(Document.builder()
+                .title("Senderbrief").originalFilename("sender.pdf")
+                .status(DocumentStatus.UPLOADED).sender(person).build());
+
+        Page<Document> result = searchByPerson(person, null, null);
+
+        assertThat(result.getContent()).extracting(Document::getId).containsExactly(doc.getId());
+    }
+
+    @Test
+    void searchByPersonSpec_returnsDocument_whenPersonIsReceiver() {
+        Person person = personRepository.save(Person.builder().lastName("Raddatz").build());
+        Document doc = documentRepository.save(Document.builder()
+                .title("Empfängerbrief").originalFilename("receiver.pdf")
+                .status(DocumentStatus.UPLOADED)
+                .receivers(new java.util.HashSet<>(List.of(person))).build());
+
+        Page<Document> result = searchByPerson(person, null, null);
+
+        assertThat(result.getContent()).extracting(Document::getId).containsExactly(doc.getId());
+    }
+
+    @Test
+    void searchByPersonSpec_returnsDocumentOnce_whenPersonIsBothSenderAndReceiver() {
+        Person person = personRepository.save(Person.builder().lastName("Raddatz").build());
+        Document doc = documentRepository.save(Document.builder()
+                .title("SenderEmpfänger").originalFilename("both.pdf")
+                .status(DocumentStatus.UPLOADED).sender(person)
+                .receivers(new java.util.HashSet<>(List.of(person))).build());
+
+        Page<Document> result = searchByPerson(person, null, null);
+
+        assertThat(result.getContent()).hasSize(1);
+        assertThat(result.getContent().get(0).getId()).isEqualTo(doc.getId());
+    }
+
+    @Test
+    void searchByPersonSpec_excludesDocuments_outsideDateRange() {
+        Person person = personRepository.save(Person.builder().lastName("Raddatz").build());
+        Document inside = documentRepository.save(Document.builder()
+                .title("Innen").originalFilename("inside.pdf").status(DocumentStatus.UPLOADED)
+                .sender(person).documentDate(LocalDate.of(1918, 6, 15)).build());
+        documentRepository.save(Document.builder()
+                .title("Außen").originalFilename("outside.pdf").status(DocumentStatus.UPLOADED)
+                .sender(person).documentDate(LocalDate.of(1920, 1, 1)).build());
+
+        Page<Document> result = searchByPerson(person, LocalDate.of(1914, 1, 1), LocalDate.of(1918, 12, 31));
+
+        assertThat(result.getContent()).extracting(Document::getId).containsExactly(inside.getId());
+    }
+
+    @Test
+    void searchByPersonSpec_returnsEmpty_whenNoMatchingDocuments() {
+        Person person = personRepository.save(Person.builder().lastName("Raddatz").build());
+        Person other = personRepository.save(Person.builder().lastName("Braun").build());
+        documentRepository.save(Document.builder()
+                .title("Fremder Brief").originalFilename("other.pdf")
+                .status(DocumentStatus.UPLOADED).sender(other).build());
+
+        Page<Document> result = searchByPerson(person, null, null);
+
+        assertThat(result.getContent()).isEmpty();
+    }
 }