diff --git a/weave_query/tests/test_propagate_gql_keys.py b/weave_query/tests/test_propagate_gql_keys.py
new file mode 100644
index 000000000000..e13aa5e87c29
--- /dev/null
+++ b/weave_query/tests/test_propagate_gql_keys.py
@@ -0,0 +1,64 @@
+import pytest
+from weave_query import (
+    weave_types as types,
+    graph,
+    op_def,
+    op_args
+)
+from weave_query.language_features.tagging import (
+    tagged_value_type,
+)
+from weave_query.propagate_gql_keys import _propagate_gql_keys_for_node
+from weave_query.ops_domain import wb_domain_types as wdt
+
+def test_mapped_tag_propagation():
+    test_op = op_def.OpDef(
+        name="run-base_op",
+        input_type=op_args.OpNamedArgs({"run": wdt.RunType}),
+        output_type=types.List(types.Number()),
+        resolve_fn=lambda: None
+    )
+
+    mapped_opdef = op_def.OpDef(
+        name="mapped_run-base_op",
+        input_type=op_args.OpNamedArgs({"run": types.List(wdt.RunType)}),
+        output_type=types.List(types.List(types.Number())),
+        resolve_fn=lambda: None
+    )
+
+    mapped_opdef.derived_from = test_op
+    test_op.derived_ops = {"mapped": mapped_opdef}
+
+    test_node = graph.OutputNode(
+        types.List(types.Number()),
+        "mapped_run-base_op",
+        {
+            "run": graph.OutputNode(
+                tagged_value_type.TaggedValueType(types.TypedDict({"project": wdt.ProjectType}), types.List(wdt.RunType)),
+                "limit",
+                {
+                    "arr": graph.OutputNode(
+                        tagged_value_type.TaggedValueType(
+                            types.TypedDict({"project": wdt.ProjectType}),
+                            types.List(wdt.RunType)
+                        ),
+                    "project-filteredRuns",
+                    {}
+            )
+        }
+            )
+        }
+    )
+
+    def mock_key_fn(ip, input_type):
+        return types.List(types.Number())
+    
+    result = _propagate_gql_keys_for_node(mapped_opdef, test_node, mock_key_fn, None)
+
+    assert isinstance(result, tagged_value_type.TaggedValueType)
+    # existing project tag from inputs flowed to output
+    assert result.tag.property_types["project"]
+    # run input propagated as tag on output
+    assert result.value.object_type.tag.property_types["run"]
+    assert isinstance(result.value.object_type.value, types.List)
+    assert isinstance(result.value.object_type.value.object_type, types.Number)
\ No newline at end of file
diff --git a/weave_query/weave_query/propagate_gql_keys.py b/weave_query/weave_query/propagate_gql_keys.py
index 641fd771fae8..382dd782c69c 100644
--- a/weave_query/weave_query/propagate_gql_keys.py
+++ b/weave_query/weave_query/propagate_gql_keys.py
@@ -43,6 +43,11 @@ def _propagate_gql_keys_for_node(
         raise ValueError('GQL key function returned "Invalid" type')
 
     if is_mapped:
+        # Handle tag propagation for mapped run ops
+        if opdef_util.should_tag_op_def_outputs(opdef.derived_from):
+            new_output_type = tagged_value_type.TaggedValueType(
+                types.TypedDict({first_arg_name: unwrapped_input_type}), new_output_type
+            )
         new_output_type = types.List(new_output_type)
 
     # now we rewrap the types to propagate the tags