diff --git a/backend/src/test/java/org/raddatz/familienarchiv/service/OcrTrainingServiceTest.java b/backend/src/test/java/org/raddatz/familienarchiv/service/OcrTrainingServiceTest.java
index 7d83188f..1d1e47e9 100644
--- a/backend/src/test/java/org/raddatz/familienarchiv/service/OcrTrainingServiceTest.java
+++ b/backend/src/test/java/org/raddatz/familienarchiv/service/OcrTrainingServiceTest.java
@@ -146,6 +146,90 @@ class OcrTrainingServiceTest {
                 run.getStatus() == TrainingStatus.FAILED && run.getErrorMessage() != null));
     }
 
+    // ─── triggerSegTraining ───────────────────────────────────────────────────
+
+    @Test
+    void triggerSegTraining_throws409_whenRunningRunExists() {
+        when(runRepository.findFirstByStatus(TrainingStatus.RUNNING))
+                .thenReturn(Optional.of(OcrTrainingRun.builder()
+                        .id(UUID.randomUUID()).status(TrainingStatus.RUNNING)
+                        .blockCount(5).documentCount(2).modelName("blla").build()));
+
+        assertThatThrownBy(() -> service.triggerSegTraining(null))
+                .isInstanceOf(DomainException.class)
+                .extracting("status")
+                .satisfies(s -> assertThat(s.toString()).contains("409"));
+    }
+
+    @Test
+    void triggerSegTraining_throws422_whenFewerThan5Segments() {
+        when(runRepository.findFirstByStatus(TrainingStatus.RUNNING)).thenReturn(Optional.empty());
+        when(segExportService.querySegmentationBlocks()).thenReturn(List.of(
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(UUID.randomUUID()).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(UUID.randomUUID()).build()
+        ));
+
+        assertThatThrownBy(() -> service.triggerSegTraining(null))
+                .isInstanceOf(DomainException.class);
+    }
+
+    @Test
+    void triggerSegTraining_createsRunWithBlla_andMarksDoneWithCer() throws Exception {
+        when(runRepository.findFirstByStatus(TrainingStatus.RUNNING)).thenReturn(Optional.empty());
+
+        UUID docA = UUID.randomUUID();
+        UUID docB = UUID.randomUUID();
+        List<TranscriptionBlock> segs = List.of(
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docB).build()
+        );
+        when(segExportService.querySegmentationBlocks()).thenReturn(segs);
+        when(segExportService.exportToZip()).thenReturn(out -> {});
+        when(ocrClient.segtrainModel(any())).thenReturn(new OcrClient.TrainingResult(null, 0.92, 0.08, 5));
+
+        OcrTrainingRun saved = OcrTrainingRun.builder()
+                .id(UUID.randomUUID()).status(TrainingStatus.RUNNING)
+                .blockCount(5).documentCount(2).modelName("blla").build();
+        when(runRepository.save(any())).thenReturn(saved);
+
+        service.triggerSegTraining(null);
+
+        verify(runRepository, atLeastOnce()).save(argThat(run ->
+                run.getStatus() == TrainingStatus.DONE
+                        && "blla".equals(run.getModelName())
+                        && run.getCer() != null));
+    }
+
+    @Test
+    void triggerSegTraining_marksRunFailed_whenOcrClientThrows() throws Exception {
+        when(runRepository.findFirstByStatus(TrainingStatus.RUNNING)).thenReturn(Optional.empty());
+
+        UUID docA = UUID.randomUUID();
+        List<TranscriptionBlock> segs = List.of(
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build(),
+                TranscriptionBlock.builder().id(UUID.randomUUID()).documentId(docA).build()
+        );
+        when(segExportService.querySegmentationBlocks()).thenReturn(segs);
+        when(segExportService.exportToZip()).thenReturn(out -> {});
+        when(ocrClient.segtrainModel(any())).thenThrow(new RuntimeException("seg timeout"));
+
+        OcrTrainingRun saved = OcrTrainingRun.builder()
+                .id(UUID.randomUUID()).status(TrainingStatus.RUNNING)
+                .blockCount(5).documentCount(1).modelName("blla").build();
+        when(runRepository.save(any())).thenReturn(saved);
+
+        service.triggerSegTraining(null);
+
+        verify(runRepository, atLeastOnce()).save(argThat(run ->
+                run.getStatus() == TrainingStatus.FAILED && run.getErrorMessage() != null));
+    }
+
     // ─── Orphan recovery ──────────────────────────────────────────────────────
 
     @Test