diff --git a/common/metadata_infinity_filter.py b/common/metadata_infinity_filter.py
index 238afd3596..c49174b9aa 100644
--- a/common/metadata_infinity_filter.py
+++ b/common/metadata_infinity_filter.py
@@ -55,6 +55,20 @@ _RANGE_OPS: Dict[str, str] = {
     "≤": "<=",
 }
 
+# Negative operators whose legacy per-value-bucket semantics cannot be
+# reproduced by a single push-down predicate over a multi-valued metadata
+# field. ``meta_fields.<key>`` may hold a JSON array, and the in-memory
+# ``meta_filter`` matches a doc when ANY of its values satisfies the predicate;
+# e.g. a doc whose ``tag`` is ``[a, b]`` still matches ``tag ≠ a`` (via bucket
+# ``b``). ``NOT JSON_CONTAINS(...)`` instead means "the array contains no ``a``
+# at all", which would silently drop that doc. Without a cheap way to prove a
+# field is single-valued at query time we refuse push-down for these operators
+# and let the in-memory fallback handle them. Mirrors the identically named set
+# in ``metadata_es_filter``. ``not contains`` is intentionally excluded:
+# ``all(not contains)`` equals ``not any(contains)``, which the push-down
+# expresses correctly on both single- and multi-valued fields.
+MULTIVALUE_UNSAFE_NEGATIVE_OPS: frozenset[str] = frozenset({"≠", "not in"})
+
 
 class MetaFilterTranslator:
     """Translate one user filter clause at a time into Infinity SQL filter strings."""
@@ -209,6 +223,8 @@ def is_pushdown_supported(filters: Sequence[Dict[str, Any]]) -> bool:
         op = flt.get("op")
         if op not in SUPPORTED_OPERATORS:
             return False
+        if op in MULTIVALUE_UNSAFE_NEGATIVE_OPS:
+            return False
         if not isinstance(flt.get("key"), str) or not flt.get("key"):
             return False
     return True
diff --git a/test/unit_test/common/test_metadata_filter.py b/test/unit_test/common/test_metadata_filter.py
index 62f69c9101..7ea3262d25 100644
--- a/test/unit_test/common/test_metadata_filter.py
+++ b/test/unit_test/common/test_metadata_filter.py
@@ -61,6 +61,20 @@ def test_pushdown_check_accepts_not_contains():
     assert is_pushdown_supported([{"key": "tag", "op": "not contains", "value": "x"}])
 
 
+@pytest.mark.parametrize("op", ["≠", "not in"])
+def test_pushdown_check_rejects_multivalue_unsafe_negative_ops(op):
+    # These negative operators cannot be expressed as a single push-down
+    # predicate over a multi-valued metadata field without diverging from the
+    # in-memory meta_filter's per-value-bucket semantics, so both backends must
+    # refuse push-down and fall back to in-memory evaluation. The ES backend
+    # already does this; the Infinity backend must match it.
+    from common.metadata_es_filter import is_pushdown_supported as es_is_pushdown_supported
+
+    flt = [{"key": "tag", "op": op, "value": "a"}]
+    assert not is_pushdown_supported(flt)
+    assert not es_is_pushdown_supported(flt)
+
+
 # ---------------------------------------------------------------------------
 # Shared: plan_pushdown (same logic for both backends)
 # ---------------------------------------------------------------------------