diff --git a/tests/test_observation_metadata_invariants.py b/tests/test_observation_metadata_invariants.py
new file mode 100644
index 000000000..f7bdef32d
--- /dev/null
+++ b/tests/test_observation_metadata_invariants.py
@@ -0,0 +1,18 @@
+import pytest
+
+def sanitize_metadata(meta: dict) -> dict:
+    if not isinstance(meta, dict):
+        return {}
+    cleaned = {}
+    for k, v in meta.items():
+        if isinstance(k, str) and k.strip():
+            cleaned[k.strip()] = v
+    return cleaned
+
+def test_sanitize_metadata_valid():
+    data = {"env": "prod", "  version ": "1.2.0", "active": True}
+    assert sanitize_metadata(data) == {"env": "prod", "version": "1.2.0", "active": True}
+
+def test_sanitize_metadata_empty_keys():
+    data = {"": "val", "   ": "val2", "valid": 100}
+    assert sanitize_metadata(data) == {"valid": 100}