diff --git a/backend/apps/ifc_validation/tasks/task_runner.py b/backend/apps/ifc_validation/tasks/task_runner.py
index 46f8f6a7..84fa8cd9 100644
--- a/backend/apps/ifc_validation/tasks/task_runner.py
+++ b/backend/apps/ifc_validation/tasks/task_runner.py
@@ -5,6 +5,9 @@
 from celery import shared_task, chain, chord, group
 from celery.exceptions import SoftTimeLimitExceeded
 
+from django.db.models import F, Value
+from django.db.models.functions import Least
+
 from core.redis_lock import acquire_user_lock, LockError
 from core.utils import log_execution
 
@@ -192,11 +195,6 @@ def validation_subtask_runner(self, *args, **kwargs):
         else: # for testing, we're not instantiating a model
             invalid_blockers = []
         
-        # update progress
-        increment = config.increment
-        request.progress = min(request.progress + increment, 100)
-        request.save()
-
         # run or skip
         if not invalid_blockers:
             task.mark_as_initiated()
@@ -224,12 +222,19 @@ def validation_subtask_runner(self, *args, **kwargs):
                 logger.exception(f"Processing failed in task {task_type}: {err}")
                 return
             
-        # Handle skipped tasks              
+        # Handle skipped tasks
         else:
             reason = f"Skipped due to fail in blocking tasks: {', '.join(invalid_blockers)}"
             logger.debug(reason)
             task.mark_as_skipped(reason)
-            
+
+        # Advance progress only after the work is done, so a request never shows
+        # 100% while a long-running task (e.g. instance completion) is still running.
+        # Failed tasks returned early above. Atomic: parallel tasks increment together.
+        ValidationRequest.objects.filter(pk=id).update(
+            progress=Least(F("progress") + config.increment, Value(100))
+        )
+
     validation_subtask_runner.__doc__ = f"Validation task for {task_type} generated by the task_factory func."    
     return validation_subtask_runner
 
diff --git a/backend/apps/ifc_validation/tests/tests_progress_update.py b/backend/apps/ifc_validation/tests/tests_progress_update.py
new file mode 100644
index 00000000..0aa91cf9
--- /dev/null
+++ b/backend/apps/ifc_validation/tests/tests_progress_update.py
@@ -0,0 +1,102 @@
+from contextlib import contextmanager
+from unittest import mock
+
+from django.test import TransactionTestCase
+from django.contrib.auth.models import User
+
+from apps.ifc_validation_models.models import (
+    ValidationRequest,
+    ValidationTask,
+    set_user_context,
+)
+
+from ..tasks.configs import task_registry
+from ..tasks import schema_validation_subtask
+import apps.ifc_validation.tasks.task_runner as task_runner
+
+
+@contextmanager
+def _noop_lock(*args, **kwargs):
+    # Replaces the redis-backed user task lock so these tests stay hermetic.
+    yield None
+
+
+@mock.patch.object(task_runner, "acquire_user_lock", _noop_lock)
+class ProgressUpdateTaskTestCase(TransactionTestCase):
+    """Progress must advance only after a subtask's work finishes, so a request
+    never reports 100% while a task is still running."""
+
+    TASK_TYPE = ValidationTask.Type.SCHEMA  # increment = 10
+
+    def setUp(self):
+        user, _ = User.objects.get_or_create(
+            id=1, defaults={"username": "SYSTEM", "is_active": True}
+        )
+        set_user_context(user)
+        self.config = task_registry[self.TASK_TYPE]
+        self.increment = self.config.increment
+
+    def _make_request(self, progress=0):
+        request = ValidationRequest.objects.create(
+            file_name="valid_file.ifc", file="valid_file.ifc", size=280
+        )
+        request.mark_as_initiated()  # progress -> 0
+        if progress:
+            ValidationRequest.objects.filter(pk=request.id).update(progress=progress)
+        return request
+
+    def _run(self, request):
+        schema_validation_subtask(
+            prev_result={"is_valid": True, "reason": "test"},
+            id=request.id,
+            file_name=request.file_name,
+        )
+
+    def test_progress_advances_only_after_task_work_completes(self):
+        request = self._make_request()
+        seen = {}
+
+        def fake_check(context):
+            seen["during_check"] = ValidationRequest.objects.get(pk=request.id).progress
+            return context
+
+        def fake_process(context):
+            seen["during_process"] = ValidationRequest.objects.get(pk=request.id).progress
+            return "ok"
+
+        with mock.patch.object(self.config, "check_program", side_effect=fake_check), \
+             mock.patch.object(self.config, "process_results", side_effect=fake_process):
+            self._run(request)
+
+        # During the task body, progress must not have advanced (the bug: it was
+        # bumped before the work ran).
+        self.assertEqual(seen["during_check"], 0)
+        self.assertEqual(seen["during_process"], 0)
+
+        # It advances by the increment only after the task finishes.
+        request.refresh_from_db()
+        self.assertEqual(request.progress, self.increment)
+
+    def test_progress_is_clamped_to_100(self):
+        request = self._make_request(progress=95)  # 95 + 10 would overflow to 105
+
+        with mock.patch.object(self.config, "check_program", return_value=None), \
+             mock.patch.object(self.config, "process_results", return_value="ok"):
+            self._run(request)
+
+        request.refresh_from_db()
+        self.assertEqual(request.progress, 100)
+
+    def test_failed_task_does_not_advance_progress(self):
+        request = self._make_request()
+
+        with mock.patch.object(self.config, "check_program", side_effect=RuntimeError("boom")):
+            self._run(request)
+
+        request.refresh_from_db()
+        self.assertEqual(request.progress, 0)
+
+        task = ValidationTask.objects.filter(
+            request_id=request.id, type=self.TASK_TYPE
+        ).first()
+        self.assertEqual(task.status, ValidationTask.Status.FAILED)