diff --git a/scripts/pipeline.py b/scripts/pipeline.py
index 02c53735b..ab7dfdea1 100644
--- a/scripts/pipeline.py
+++ b/scripts/pipeline.py
@@ -603,6 +603,26 @@ def _refuse_unapplied_flags(
         args.source = "full"
 
 
+def _refuse_offline_without_caches(
+    parser: argparse.ArgumentParser, args: argparse.Namespace, platforms_dir: str = "platforms",
+) -> None:
+    """An offline run that builds packs needs the data directories cached.
+
+    On a fresh clone none is: --offline skips the refresh, and the run went
+    through the database, verify and every pack before failing at the end
+    of the build. Only an empty cache is refused here: with some cached, the
+    packs decide which ones they need and the build names the rest.
+    """
+    if not args.offline or args.skip_packs:
+        return
+    registry = load_data_dir_registry(platforms_dir)
+    if registry and not any(os.path.isdir(e.get("local_cache") or "") for e in registry.values()):
+        parser.error(
+            "no data directory is cached and --offline skips their refresh: run "
+            "python scripts/refresh_data_dirs.py once, or drop --offline"
+        )
+
+
 def _truth_steps(args: argparse.Namespace, results: dict) -> bool:
     """Steps 2c to 2e: truth model, its diff, the native export."""
     all_ok = True
@@ -723,6 +743,7 @@ def main() -> None:
     )
     args = parser.parse_args()
     _refuse_unapplied_flags(parser, args)
+    _refuse_offline_without_caches(parser, args)
     if not args.offline:
         # Read once and put in the environment every step inherits: the
         # scrapers and refresh_data_dirs went anonymous unless the user had
diff --git a/tests/test_tool_messages.py b/tests/test_tool_messages.py
index 436e05137..0293bad48 100644
--- a/tests/test_tool_messages.py
+++ b/tests/test_tool_messages.py
@@ -130,6 +130,34 @@ class TheGapHeadingAddsUp(unittest.TestCase):
         )
 
 
+class AnOfflineRunWithNoCacheStopsFirst(unittest.TestCase):
+    """On a fresh clone, pipeline.py --offline built every pack before saying
+    the data directories had never been fetched."""
+
+    def _args(self, **flags):
+        import argparse
+
+        return argparse.Namespace(**{"offline": True, "skip_packs": False, **flags})
+
+    def test_refused_before_any_step(self):
+        with tempfile.TemporaryDirectory(dir=REPO_ROOT / "tmp") as tmp:
+            cache = Path(tmp) / "cache"
+            (Path(tmp) / "_data_dirs.yml").write_text(
+                f"data_directories:\n  a:\n    local_cache: {cache}\n"
+            )
+            parser = mock.Mock()
+            pipeline._refuse_offline_without_caches(parser, self._args(), tmp)
+            self.assertIn("refresh_data_dirs.py", parser.error.call_args.args[0])
+            for args in (self._args(offline=False), self._args(skip_packs=True)):
+                parser = mock.Mock()
+                pipeline._refuse_offline_without_caches(parser, args, tmp)
+                parser.error.assert_not_called()
+            cache.mkdir()
+            parser = mock.Mock()
+            pipeline._refuse_offline_without_caches(parser, self._args(), tmp)
+            parser.error.assert_not_called()
+
+
 class TheTruthDiffShowsWhereAndAsksNothing(unittest.TestCase):
     """The markdown wrote `**Remove** hiscore.dat (phantom)` beside six
     `**Add** hiscore.dat`, none with a path, for files profiled cores read."""
diff --git a/wiki/tools.md b/wiki/tools.md
index e4a19bc10..1acea4c99 100644
--- a/wiki/tools.md
+++ b/wiki/tools.md
@@ -24,6 +24,10 @@ python scripts/pipeline.py --offline --include-archived  # include archived plat
 python scripts/pipeline.py --check-buildbot        # online run + buildbot freshness check
 ```
 
+`--offline` skips the data directory refresh, so on a fresh clone run
+`python scripts/refresh_data_dirs.py` once first. A run that builds packs with no
+data directory cached is refused before step 0.
+
 Pipeline steps:
 
 | Step | Description | Skipped by |