diff --git a/backend/src/test/java/org/raddatz/familienarchiv/repository/MigrationIntegrationTest.java b/backend/src/test/java/org/raddatz/familienarchiv/repository/MigrationIntegrationTest.java
new file mode 100644
index 00000000..7fb3c406
--- /dev/null
+++ b/backend/src/test/java/org/raddatz/familienarchiv/repository/MigrationIntegrationTest.java
@@ -0,0 +1,136 @@
+package org.raddatz.familienarchiv.repository;
+
+import jakarta.persistence.EntityManager;
+import org.junit.jupiter.api.Test;
+import org.raddatz.familienarchiv.PostgresContainerConfig;
+import org.raddatz.familienarchiv.config.FlywayConfig;
+import org.raddatz.familienarchiv.model.Document;
+import org.raddatz.familienarchiv.model.DocumentStatus;
+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 org.springframework.dao.DataIntegrityViolationException;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.transaction.annotation.Propagation;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.util.UUID;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+/**
+ * Integration tests that verify DB-level constraints introduced in the OCR pipeline migrations
+ * are actually enforced by PostgreSQL. These tests exercise constraints that cannot be verified
+ * by unit tests alone.
+ */
+@DataJpaTest
+@AutoConfigureTestDatabase(replace = AutoConfigureTestDatabase.Replace.NONE)
+@Import({PostgresContainerConfig.class, FlywayConfig.class})
+class MigrationIntegrationTest {
+
+    @Autowired JdbcTemplate jdbc;
+    @Autowired DocumentRepository documentRepository;
+    @Autowired EntityManager em;
+
+    // ─── V23: chk_annotation_polygon_quad CHECK constraint ───────────────────
+
+    @Test
+    void v23_polygonCheckConstraint_rejectsNonQuadrilateral() {
+        UUID docId = createDocument();
+
+        // A 3-point polygon violates chk_annotation_polygon_quad (must be exactly 4 points or NULL)
+        assertThatThrownBy(() ->
+                jdbc.update(
+                        """
+                        INSERT INTO document_annotations
+                            (id, document_id, page_number, x, y, width, height, color, polygon)
+                        VALUES (gen_random_uuid(), ?, 1, 0.1, 0.1, 0.5, 0.1, '#00C7B1',
+                                '[[0.1,0.1],[0.9,0.1],[0.9,0.2]]'::jsonb)
+                        """,
+                        docId)
+        ).isInstanceOf(DataIntegrityViolationException.class);
+    }
+
+    @Test
+    void v23_polygonCheckConstraint_allowsNullPolygon() {
+        UUID docId = createDocument();
+
+        int rows = jdbc.update(
+                """
+                INSERT INTO document_annotations
+                    (id, document_id, page_number, x, y, width, height, color, polygon)
+                VALUES (gen_random_uuid(), ?, 1, 0.1, 0.1, 0.5, 0.1, '#00C7B1', NULL)
+                """,
+                docId);
+
+        assertThat(rows).isEqualTo(1);
+    }
+
+    @Test
+    void v23_polygonCheckConstraint_allowsQuadrilateral() {
+        UUID docId = createDocument();
+
+        int rows = jdbc.update(
+                """
+                INSERT INTO document_annotations
+                    (id, document_id, page_number, x, y, width, height, color, polygon)
+                VALUES (gen_random_uuid(), ?, 1, 0.1, 0.1, 0.5, 0.1, '#00C7B1',
+                        '[[0.1,0.1],[0.9,0.1],[0.9,0.2],[0.1,0.2]]'::jsonb)
+                """,
+                docId);
+
+        assertThat(rows).isEqualTo(1);
+    }
+
+    // ─── V30: idx_ocr_training_runs_one_running partial unique index ──────────
+
+    @Test
+    @Transactional(propagation = Propagation.NOT_SUPPORTED)
+    void v30_partialUniqueIndex_preventsTwoRunningTrainingRuns() {
+        jdbc.update("""
+                INSERT INTO ocr_training_runs (id, status, block_count, document_count, model_name)
+                VALUES (gen_random_uuid(), 'RUNNING', 10, 2, 'kurrent_v1')
+                """);
+
+        // A second RUNNING row violates the partial unique index
+        assertThatThrownBy(() ->
+                jdbc.update("""
+                        INSERT INTO ocr_training_runs (id, status, block_count, document_count, model_name)
+                        VALUES (gen_random_uuid(), 'RUNNING', 5, 1, 'kurrent_v1')
+                        """)
+        ).isInstanceOf(DataIntegrityViolationException.class);
+
+        // Clean up — runs outside the DataJpaTest transaction, so must be explicit
+        jdbc.update("DELETE FROM ocr_training_runs WHERE status = 'RUNNING'");
+    }
+
+    @Test
+    void v30_partialUniqueIndex_allowsMultipleDoneRuns() {
+        int rows1 = jdbc.update("""
+                INSERT INTO ocr_training_runs (id, status, block_count, document_count, model_name)
+                VALUES (gen_random_uuid(), 'DONE', 10, 2, 'kurrent_v1')
+                """);
+        int rows2 = jdbc.update("""
+                INSERT INTO ocr_training_runs (id, status, block_count, document_count, model_name)
+                VALUES (gen_random_uuid(), 'DONE', 15, 3, 'kurrent_v2')
+                """);
+
+        assertThat(rows1).isEqualTo(1);
+        assertThat(rows2).isEqualTo(1);
+    }
+
+    // ─── helpers ─────────────────────────────────────────────────────────────
+
+    private UUID createDocument() {
+        Document doc = documentRepository.save(Document.builder()
+                .title("Testdokument")
+                .originalFilename("test.pdf")
+                .status(DocumentStatus.UPLOADED)
+                .build());
+        // Flush so the row is visible to subsequent JdbcTemplate queries within the same transaction
+        em.flush();
+        return doc.getId();
+    }
+}