fix: preserve concurrent teacher decisions when model scoring fails

backend/wisegrade/scoring.py

@@ -387,13 +387,17 @@ def _run_project(batch_id, project_id, session_factory, client_factory, embedder
             except Exception as exc:
                 db.rollback()
                 score = db.scalar(select(CriterionScore).where(CriterionScore.batch_id == batch.id,
-                                  CriterionScore.project_id == project.id, CriterionScore.criterion_id == criterion["criterion_id"]))
+                                  CriterionScore.project_id == project.id, CriterionScore.criterion_id == criterion["criterion_id"])
+                                  .with_for_update().execution_options(populate_existing=True))
                 if not score:
                     score = CriterionScore(batch_id=batch.id, project_id=project.id, criterion_id=criterion["criterion_id"])
                     db.add(score)
-                score.status, score.error = STATUS_FAILED, str(exc)[:500]
-                db.commit()
-                failures += 1
+                # A teacher may have committed a decision while the request was in
+                # flight. The exception path must honour it just like success does.
+                if score.status != STATUS_REVIEWED and score.teacher_score is None:
+                    score.status, score.error = STATUS_FAILED, str(exc)[:500]
+                    db.commit()
+                    failures += 1
             db.execute(update(ScoringBatch).where(ScoringBatch.id == batch_id).values(progress_done=ScoringBatch.progress_done + 1))
             db.commit()
     return failures, reviews