diff --git a/scripts/pipeline.py b/scripts/pipeline.py
index 88b06cf7..56d101a0 100644
--- a/scripts/pipeline.py
+++ b/scripts/pipeline.py
@@ -46,8 +46,10 @@ from common import (
     artifact_lock,
     hold_artifact_lock,
     list_registered_platforms,
+    load_data_dir_registry,
     truth_target_dir,
 )
+from refresh_data_dirs import hold_data_dirs
 
 
 def run(cmd: list[str], label: str) -> tuple[bool, str]:
@@ -478,6 +480,14 @@ def main() -> None:
 
     all_ok = _truth_steps(args, results) and all_ok
 
+    # Every step from here reads the data directory trees: verify, the packs,
+    # the manifests and the integrity check. Held shared until the run ends,
+    # a refresh from another session waits instead of swapping a tree
+    # between the packs and the manifests, which would then describe two
+    # revisions of it. Taken after step 2, whose own refresh needs them
+    # exclusive.
+    hold_data_dirs(held, load_data_dir_registry("platforms"))
+
     # Step 3: Verify
     verify_cmd = [sys.executable, "scripts/verify.py", "--all", "--strict"]
     if args.include_archived:
diff --git a/tests/test_artifact_lock.py b/tests/test_artifact_lock.py
index abd4173c..748b109e 100644
--- a/tests/test_artifact_lock.py
+++ b/tests/test_artifact_lock.py
@@ -207,5 +207,19 @@ class HeldLockTest(unittest.TestCase):
         self.assertIn("hold_artifact_lock(args.output_dir)", source)
 
 
+class PipelineHoldsTheDataTrees(unittest.TestCase):
+    """The pipeline held dist/ for the whole run but not the data directory
+    trees: a refresh from another session could swap one between the packs
+    and the manifests, which then described two revisions of it."""
+
+    def test_the_trees_are_held_after_the_refresh_and_before_verify(self):
+        source = (Path(__file__).resolve().parents[1] / "scripts" / "pipeline.py").read_text()
+        refresh = source.index('"scripts/refresh_data_dirs.py"')
+        hold = source.index("hold_data_dirs(held,")
+        verify = source.index('"scripts/verify.py", "--all"')
+        self.assertLess(refresh, hold)
+        self.assertLess(hold, verify)
+
+
 if __name__ == "__main__":
     unittest.main()