diff --git a/esphome/automation.py b/esphome/automation.py
index fad344fe1f..366d23e882 100644
--- a/esphome/automation.py
+++ b/esphome/automation.py
@@ -62,14 +62,16 @@ def register_action(
     action_type: MockObjClass,
     schema: cv.Schema,
     *,
-    deferred: bool = False,
+    deferred: bool = True,
 ):
     """Register an action type.
 
-    Set ``deferred=True`` if this action stores trigger arguments for later
-    execution (e.g. delay, wait_until, script.wait).  This tells the code
-    generator to use owning types (std::string) instead of non-owning views
-    (StringRef) for string arguments, preventing dangling references.
+    Actions default to ``deferred=True`` (safe default), meaning string
+    arguments use owning std::string to prevent dangling references.
+
+    Set ``deferred=False`` only for actions that complete synchronously
+    and never store trigger arguments for later execution.  This allows
+    the code generator to use non-owning StringRef for zero-copy access.
     """
     return ACTION_REGISTRY.register(name, action_type, schema, deferred=deferred)
 
@@ -351,7 +353,6 @@ async def component_is_idle_condition_to_code(
     "delay",
     DelayAction,
     cv.templatable(cv.positive_time_period_milliseconds),
-    deferred=True,
 )
 async def delay_action_to_code(
     config: ConfigType,
@@ -382,6 +383,7 @@ async def delay_action_to_code(
         cv.has_at_least_one_key(CONF_THEN, CONF_ELSE),
         cv.has_at_least_one_key(CONF_CONDITION, CONF_ANY, CONF_ALL),
     ),
+    deferred=False,
 )
 async def if_action_to_code(
     config: ConfigType,
@@ -410,6 +412,7 @@ async def if_action_to_code(
             cv.Required(CONF_THEN): validate_action_list,
         }
     ),
+    deferred=False,
 )
 async def while_action_to_code(
     config: ConfigType,
@@ -433,6 +436,7 @@ async def while_action_to_code(
             cv.Required(CONF_THEN): validate_action_list,
         }
     ),
+    deferred=False,
 )
 async def repeat_action_to_code(
     config: ConfigType,
@@ -461,7 +465,7 @@ _validate_wait_until = cv.maybe_simple_value(
 )
 
 
-@register_action("wait_until", WaitUntilAction, _validate_wait_until, deferred=True)
+@register_action("wait_until", WaitUntilAction, _validate_wait_until)
 async def wait_until_action_to_code(
     config: ConfigType,
     action_id: ID,
@@ -477,7 +481,7 @@ async def wait_until_action_to_code(
     return var
 
 
-@register_action("lambda", LambdaAction, cv.lambda_)
+@register_action("lambda", LambdaAction, cv.lambda_, deferred=False)
 async def lambda_action_to_code(
     config: ConfigType,
     action_id: ID,
@@ -496,6 +500,7 @@ async def lambda_action_to_code(
             cv.Required(CONF_ID): cv.use_id(cg.PollingComponent),
         }
     ),
+    deferred=False,
 )
 async def component_update_action_to_code(
     config: ConfigType,
@@ -515,6 +520,7 @@ async def component_update_action_to_code(
             cv.Required(CONF_ID): cv.use_id(cg.PollingComponent),
         }
     ),
+    deferred=False,
 )
 async def component_suspend_action_to_code(
     config: ConfigType,
@@ -537,6 +543,7 @@ async def component_suspend_action_to_code(
             ),
         }
     ),
+    deferred=False,
 )
 async def component_resume_action_to_code(
     config: ConfigType,
diff --git a/esphome/components/ble_client/__init__.py b/esphome/components/ble_client/__init__.py
index 37db181584..e7e96b6da5 100644
--- a/esphome/components/ble_client/__init__.py
+++ b/esphome/components/ble_client/__init__.py
@@ -172,7 +172,9 @@ BLE_REMOVE_BOND_ACTION_SCHEMA = cv.Schema(
 
 
 @automation.register_action(
-    "ble_client.disconnect", BLEDisconnectAction, BLE_CONNECT_ACTION_SCHEMA
+    "ble_client.disconnect",
+    BLEDisconnectAction,
+    BLE_CONNECT_ACTION_SCHEMA,
 )
 async def ble_disconnect_to_code(config, action_id, template_arg, args):
     parent = await cg.get_variable(config[CONF_ID])
@@ -180,7 +182,9 @@ async def ble_disconnect_to_code(config, action_id, template_arg, args):
 
 
 @automation.register_action(
-    "ble_client.connect", BLEConnectAction, BLE_CONNECT_ACTION_SCHEMA
+    "ble_client.connect",
+    BLEConnectAction,
+    BLE_CONNECT_ACTION_SCHEMA,
 )
 async def ble_connect_to_code(config, action_id, template_arg, args):
     parent = await cg.get_variable(config[CONF_ID])
@@ -188,7 +192,9 @@ async def ble_connect_to_code(config, action_id, template_arg, args):
 
 
 @automation.register_action(
-    "ble_client.ble_write", BLEWriteAction, BLE_WRITE_ACTION_SCHEMA
+    "ble_client.ble_write",
+    BLEWriteAction,
+    BLE_WRITE_ACTION_SCHEMA,
 )
 async def ble_write_to_code(config, action_id, template_arg, args):
     parent = await cg.get_variable(config[CONF_ID])
diff --git a/esphome/components/script/__init__.py b/esphome/components/script/__init__.py
index 0a9e289511..4ff3d27ceb 100644
--- a/esphome/components/script/__init__.py
+++ b/esphome/components/script/__init__.py
@@ -160,6 +160,7 @@ async def to_code(config):
             cv.Optional(validate_parameter_name): cv.templatable(cv.valid),
         },
     ),
+    deferred=False,
 )
 async def script_execute_action_to_code(config, action_id, template_arg, args):
     def convert(type: str):
@@ -208,6 +209,7 @@ async def script_execute_action_to_code(config, action_id, template_arg, args):
     "script.stop",
     ScriptStopAction,
     maybe_simple_id({cv.Required(CONF_ID): cv.use_id(Script)}),
+    deferred=False,
 )
 async def script_stop_action_to_code(config, action_id, template_arg, args):
     full_id, paren = await cg.get_variable_with_full_id(config[CONF_ID])
@@ -219,7 +221,6 @@ async def script_stop_action_to_code(config, action_id, template_arg, args):
     "script.wait",
     ScriptWaitAction,
     maybe_simple_id({cv.Required(CONF_ID): cv.use_id(Script)}),
-    deferred=True,
 )
 async def script_wait_action_to_code(config, action_id, template_arg, args):
     full_id, paren = await cg.get_variable_with_full_id(config[CONF_ID])
diff --git a/esphome/util.py b/esphome/util.py
index 9fb7ef6227..c4d82fbd92 100644
--- a/esphome/util.py
+++ b/esphome/util.py
@@ -25,7 +25,7 @@ class RegistryEntry:
         type_id: "MockObjClass",
         schema: "Schema",
         *,
-        deferred: bool = False,
+        deferred: bool = True,
     ):
         self.name = name
         self.fun = fun
@@ -58,7 +58,7 @@ class Registry(dict[str, RegistryEntry]):
         type_id: "MockObjClass",
         schema: "Schema",
         *,
-        deferred: bool = False,
+        deferred: bool = True,
     ):
         def decorator(fun: Callable[..., Any]):
             self[name] = RegistryEntry(name, fun, type_id, schema, deferred=deferred)
diff --git a/tests/unit_tests/test_automation.py b/tests/unit_tests/test_automation.py
index b1170c74bb..98e0b1eea7 100644
--- a/tests/unit_tests/test_automation.py
+++ b/tests/unit_tests/test_automation.py
@@ -10,10 +10,13 @@ from esphome.util import RegistryEntry
 
 
 def _make_registry(deferred_actions: set[str]) -> dict[str, RegistryEntry]:
-    """Create a mock ACTION_REGISTRY with specified deferred actions."""
+    """Create a mock ACTION_REGISTRY with specified deferred actions.
+
+    Uses the default deferred=True, matching the real registry behavior.
+    """
     registry: dict[str, RegistryEntry] = {}
     for name in deferred_actions:
-        registry[name] = RegistryEntry(name, lambda: None, None, None, deferred=True)
+        registry[name] = RegistryEntry(name, lambda: None, None, None)
     return registry
 
 
@@ -72,10 +75,23 @@ def test_has_deferred_actions_non_deferred(
     assert has_deferred_actions([{"logger.log": "hello"}]) is False
 
 
-def test_has_deferred_actions_unknown(mock_registry: dict[str, RegistryEntry]) -> None:
+def test_has_deferred_actions_unknown_not_in_registry(
+    mock_registry: dict[str, RegistryEntry],
+) -> None:
+    """Unknown actions not in registry are not flagged (only registered actions count)."""
     assert has_deferred_actions([{"unknown.action": "value"}]) is False
 
 
+def test_has_deferred_actions_default_deferred(
+    mock_registry: dict[str, RegistryEntry],
+) -> None:
+    """Actions registered without explicit deferred=False default to deferred=True."""
+    mock_registry["some.action"] = RegistryEntry(
+        "some.action", lambda: None, None, None
+    )
+    assert has_deferred_actions([{"some.action": "value"}]) is True
+
+
 def test_has_deferred_actions_nested_in_then(
     mock_registry: dict[str, RegistryEntry],
 ) -> None: