diff --git a/parser/portable.py b/parser/portable.py
index 41398ac..2ca17f4 100644
--- a/parser/portable.py
+++ b/parser/portable.py
@@ -43,3 +43,34 @@ def attach_portable_aliases(idl: dict, path: Path) -> dict:
         "count": len(pairs),
     }
     return idl
+
+
+def classify_backing_sqlfn(idl: dict) -> dict:
+    """Mark the bounding-box topological BACKING ``@sqlfn`` tags.
+
+    MobilityDB backs the five topological operators (~=/@>/<@/-|-/&&) with a SHARED C
+    ``@sqlfn`` tag named ``<op>_bbox`` (same_bbox, contains_bbox, contained_bbox,
+    overlaps_bbox, adjacent_bbox). That tag is NEVER emitted as a ``CREATE FUNCTION`` —
+    the deployed, user-facing SQL name is the operator's bare portable alias
+    (same/contains/…). The raw ``sqlfn`` is therefore a backing name, not a public one;
+    a binding that registers it leaks a function MobilityDB does not expose. Flag those
+    records with ``sqlfnBackingOnly`` + the ``publicSqlName`` (the bare alias) so every
+    binding uniformly registers the bare name + operator and drops the ``_bbox`` tag.
+
+    Not a heuristic: grounded in two catalog-native facts — the ``_bbox`` shared-backing
+    convention AND the operator→bareName map. ``publicSqlName`` is always defined because
+    every ``_bbox`` sqlfn carries one of the five topological operators.
+
+    MUST run AFTER ``attach_sqlfn_map`` (sqlfn/sqlop) AND ``attach_portable_aliases``
+    (byOperator) — it reads all three.
+    """
+    by_operator = (idl.get("portableAliases") or {}).get("byOperator") or {}
+    if not by_operator:
+        return idl
+    for f in idl.get("functions", []):
+        sqlfn = f.get("sqlfn") or ""
+        op = f.get("sqlop") or ""
+        if sqlfn.endswith("_bbox") and op in by_operator:
+            f["sqlfnBackingOnly"] = True
+            f["publicSqlName"] = by_operator[op]
+    return idl
diff --git a/run.py b/run.py
index 5b55452..49d70ef 100644
--- a/run.py
+++ b/run.py
@@ -4,7 +4,7 @@
 from pathlib import Path
 
 from parser.parser import parse_all_headers, merge_meta
-from parser.portable import attach_portable_aliases
+from parser.portable import attach_portable_aliases, classify_backing_sqlfn
 from parser.covering import attach_temporal_covering
 from parser.typerecover import recover_collapsed_types
 from parser.header_types import reconcile
@@ -110,6 +110,15 @@ def main():
             for _lo, spellings in case_bad:
                 print(f"        {' vs '.join(spellings)}", file=sys.stderr)
 
+        # Now that both the @sqlfn/@sqlop map (step 4) and the portable bare-name map
+        # (step 3) are attached, classify the shared bbox-topological BACKING tags
+        # (same_bbox/contains_bbox/…) so bindings register the bare public name, not the
+        # catalog-only backing tag.
+        idl = classify_backing_sqlfn(idl)
+        nbo = sum(1 for f in idl.get("functions", []) if f.get("sqlfnBackingOnly"))
+        print(f"      Flagged {nbo} bbox-topological backing @sqlfn tag(s) "
+              f"(sqlfnBackingOnly)", file=sys.stderr)
+
     # 5. Attach the doxygen module group (@ingroup) from the vendored source, so
     #    bindings organize their generated surface like the reference manual.
     if MEOS_SRC.exists():
diff --git a/tests/test_portable.py b/tests/test_portable.py
index 5eef798..860346c 100644
--- a/tests/test_portable.py
+++ b/tests/test_portable.py
@@ -13,7 +13,7 @@
 ROOT = Path(__file__).resolve().parents[1]
 sys.path.insert(0, str(ROOT))
 
-from parser.portable import attach_portable_aliases
+from parser.portable import attach_portable_aliases, classify_backing_sqlfn
 
 MAP = ROOT / "meta" / "portable-aliases.json"
 SCHEMA = ROOT / "meta" / "portable-aliases.schema.json"
@@ -120,6 +120,34 @@ def test_missing_file_is_noop(self):
         idl = attach_portable_aliases({"x": 1}, ROOT / "nope.json")
         self.assertNotIn("portableAliases", idl)
 
+    def test_backing_sqlfn_classification(self):
+        # A bbox-topological function carries a shared `<op>_bbox` @sqlfn backing tag
+        # that is never deployed as a CREATE FUNCTION; its public name is the operator's
+        # bare alias. classify_backing_sqlfn must flag it and record publicSqlName.
+        idl = attach_portable_aliases({"functions": [
+            {"name": "Same_stbox_stbox",     "sqlfn": "same_bbox",     "sqlop": "~="},
+            {"name": "Contains_tbox_tnumber", "sqlfn": "contains_bbox", "sqlop": "@>"},
+            {"name": "Left_stbox_stbox",     "sqlfn": "temporal_left", "sqlop": "<<"},
+            {"name": "Tpoint_trajectory",    "sqlfn": "trajectory"},
+        ]}, MAP)
+        idl = classify_backing_sqlfn(idl)
+        by = {f["name"]: f for f in idl["functions"]}
+        # the two _bbox backing tags are flagged with the bare public name
+        self.assertTrue(by["Same_stbox_stbox"]["sqlfnBackingOnly"])
+        self.assertEqual(by["Same_stbox_stbox"]["publicSqlName"], "same")
+        self.assertTrue(by["Contains_tbox_tnumber"]["sqlfnBackingOnly"])
+        self.assertEqual(by["Contains_tbox_tnumber"]["publicSqlName"], "contains")
+        # a positional op whose @sqlfn IS the deployed name (temporal_left) is untouched
+        self.assertNotIn("sqlfnBackingOnly", by["Left_stbox_stbox"])
+        # a plain function with no operator is untouched
+        self.assertNotIn("sqlfnBackingOnly", by["Tpoint_trajectory"])
+
+    def test_backing_sqlfn_noop_without_aliases(self):
+        # No portableAliases attached -> nothing to classify, no crash.
+        idl = classify_backing_sqlfn({"functions": [
+            {"name": "X", "sqlfn": "same_bbox", "sqlop": "~="}]})
+        self.assertNotIn("sqlfnBackingOnly", idl["functions"][0])
+
     def test_duplicate_detection(self):
         bad = {"families": {"a": [{"operator": "&&", "bareName": "x"},
                                   {"operator": "@>", "bareName": "x"}]},