diff --git a/cylc/flow/network/resolvers.py b/cylc/flow/network/resolvers.py
index fc9b67eeef5..79b91f97ee7 100644
--- a/cylc/flow/network/resolvers.py
+++ b/cylc/flow/network/resolvers.py
@@ -49,10 +49,10 @@
 from cylc.flow.id import Tokens
 from cylc.flow.network.schema import (
     DEF_TYPES,
-    RUNTIME_FIELD_TO_CFG_MAP,
     NodesEdges,
     PROXY_NODES,
     SUB_RESOLVERS,
+    runtime_schema_to_cfg,
     sort_elements,
 )
 
@@ -791,10 +791,8 @@ def broadcast(
             # Convert schema field names to workflow config setting names if
             # applicable:
             for i, dict_ in enumerate(settings):
-                settings[i] = {
-                    RUNTIME_FIELD_TO_CFG_MAP.get(key, key): value
-                    for key, value in dict_.items()
-                }
+                settings[i] = runtime_schema_to_cfg(dict_)
+
         if mode == 'put_broadcast':
             return self.schd.task_events_mgr.broadcast_mgr.put_broadcast(
                 cycle_points, namespaces, settings)
diff --git a/cylc/flow/network/schema.py b/cylc/flow/network/schema.py
index 2e7bd789dbf..6388b7b7e87 100644
--- a/cylc/flow/network/schema.py
+++ b/cylc/flow/network/schema.py
@@ -860,6 +860,20 @@ class Meta:
 """Map GQL Runtime fields' names to workflow config setting names."""
 
 
+def runtime_schema_to_cfg(runtime: dict) -> dict:
+    """Covert GQL Runtime field names to workflow config setting names and
+    perform any necessary processing on the values."""
+    # We have to manually lowercase the run_mode field because we don't define
+    # a proper schema for BroadcastSetting (it's just GenericScalar) so
+    # Graphene has no way to know that it should be a TaskRunMode enum.
+    return {
+        RUNTIME_FIELD_TO_CFG_MAP.get(key, key): (
+            value.lower() if key == 'run_mode' else value
+        )
+        for key, value in runtime.items()
+    }
+
+
 class Job(ObjectType):
     class Meta:
         description = "Jobs."
diff --git a/cylc/flow/scheduler.py b/cylc/flow/scheduler.py
index b8604c54cfd..ab68b454b63 100644
--- a/cylc/flow/scheduler.py
+++ b/cylc/flow/scheduler.py
@@ -604,7 +604,7 @@ def log_start(self) -> None:
             # Note that the following lines must be present at the top of
             # the workflow log file for use in reference test runs.
             LOG.info(
-                f'Run mode: {self.get_run_mode()}',
+                f'Run mode: {self.get_run_mode().value}',
                 extra=RotatingLogFileHandler.header_extra
             )
             LOG.info(
diff --git a/tests/unit/network/test_schema.py b/tests/unit/network/test_schema.py
index 5f92cb4a35c..1604cadfb0a 100644
--- a/tests/unit/network/test_schema.py
+++ b/tests/unit/network/test_schema.py
@@ -26,6 +26,7 @@
     RUNTIME_FIELD_TO_CFG_MAP,
     Mutations,
     Runtime,
+    runtime_schema_to_cfg,
     sort_elements,
     SortArgs,
 )
@@ -105,6 +106,20 @@ def test_runtime_field_to_cfg_map(field_name: str):
     assert WORKFLOW_SPEC.get('runtime', '__MANY__', cfg_name)
 
 
+@pytest.mark.parametrize('runtime_dict,expected', [
+    pytest.param(
+        {'run_mode': 'Skip'}, {'run mode': 'skip'}, id='edit-runtime'
+    ),
+    pytest.param(
+        {'run mode': 'skip'}, {'run mode': 'skip'}, id='broadcast'
+    ),
+])
+def test_runtime_schema_to_cfg(runtime_dict, expected):
+    """Test this function can handle Edit Runtime submitted values as well
+    as normal broadcast values."""
+    assert runtime_schema_to_cfg(runtime_dict) == expected
+
+
 @pytest.mark.parametrize('mutation', (
     pytest.param(attr, id=name)
     for name, attr in Mutations.__dict__.items()