From bd1d6b747fa7df7f01d977dcd7f9e9b510f48c25 Mon Sep 17 00:00:00 2001
From: jbouwh <jan@jbsoft.nl>
Date: Sat, 14 Feb 2026 13:31:16 +0000
Subject: [PATCH] Allow updates of group members

---
 homeassistant/components/mqtt/entity.py  |  7 ++--
 tests/components/mqtt/test_light_json.py | 43 ++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/homeassistant/components/mqtt/entity.py b/homeassistant/components/mqtt/entity.py
index 60514ffa974..9a2199dc85f 100644
--- a/homeassistant/components/mqtt/entity.py
+++ b/homeassistant/components/mqtt/entity.py
@@ -466,7 +466,7 @@ def async_setup_entity_entry_helper(
 
 
 class MqttAttributesMixin(Entity):
-    """Mixin used for platforms that support JSON attributes."""
+    """Mixin used for platforms that support JSON attributes and group entities."""
 
     _attributes_extra_blocked: frozenset[str] = frozenset()
     _attr_tpl: Callable[[ReceivePayloadType], ReceivePayloadType] | None = None
@@ -474,9 +474,10 @@ class MqttAttributesMixin(Entity):
         [MessageCallbackType, set[str] | None, ReceiveMessage], None
     ]
     _process_update_extra_state_attributes: Callable[[dict[str, Any]], None]
+    group: IntegrationSpecificGroup
 
     def __init__(self, config: ConfigType) -> None:
-        """Initialize the JSON attributes mixin."""
+        """Initialize the JSON attributes and handle group entities."""
         self._attributes_sub_state: dict[str, EntitySubscription] = {}
         if CONF_GROUP in config:
             self.group = IntegrationSpecificGroup(self, config[CONF_GROUP])
@@ -490,6 +491,8 @@ class MqttAttributesMixin(Entity):
 
     def attributes_prepare_discovery_update(self, config: DiscoveryInfoType) -> None:
         """Handle updated discovery message."""
+        if self.group is not None and CONF_GROUP in config:
+            self.group.included_unique_ids = config[CONF_GROUP]
         self._attributes_config = config
         self._attributes_prepare_subscribe_topics()
 
diff --git a/tests/components/mqtt/test_light_json.py b/tests/components/mqtt/test_light_json.py
index 353e54b7480..82ab35fe887 100644
--- a/tests/components/mqtt/test_light_json.py
+++ b/tests/components/mqtt/test_light_json.py
@@ -173,6 +173,7 @@ COLOR_MODES_CONFIG = {
 
 GROUP_MEMBER_1_TOPIC = "homeassistant/light/member_1/config"
 GROUP_MEMBER_2_TOPIC = "homeassistant/light/member_2/config"
+GROUP_MEMBER_3_TOPIC = "homeassistant/light/member_3/config"
 GROUP_TOPIC = "homeassistant/light/group/config"
 GROUP_DISCOVERY_MEMBER_1_CONFIG = json.dumps(
     {
@@ -192,6 +193,15 @@ GROUP_DISCOVERY_MEMBER_2_CONFIG = json.dumps(
         "default_entity_id": "light.member2",
     }
 )
+GROUP_DISCOVERY_MEMBER_3_CONFIG = json.dumps(
+    {
+        "schema": "json",
+        "command_topic": "test-command-topic-member3",
+        "unique_id": "very_unique_member3",
+        "name": "member3",
+        "default_entity_id": "light.member3",
+    }
+)
 GROUP_DISCOVERY_LIGHT_GROUP_CONFIG = json.dumps(
     {
         "schema": "json",
@@ -203,6 +213,17 @@ GROUP_DISCOVERY_LIGHT_GROUP_CONFIG = json.dumps(
         "group": ["very_unique_member1", "very_unique_member2"],
     }
 )
+GROUP_DISCOVERY_LIGHT_GROUP_CONFIG_EXPANDED = json.dumps(
+    {
+        "schema": "json",
+        "command_topic": "test-command-topic-group",
+        "state_topic": "test-state-topic-group",
+        "unique_id": "very_unique_group",
+        "name": "group",
+        "default_entity_id": "light.group",
+        "group": ["very_unique_member1", "very_unique_member2", "very_unique_member3"],
+    }
+)
 
 
 class JsonValidator:
@@ -1921,6 +1942,28 @@ async def test_light_group_discovery_members_before_group(
         "light.member2",
     ]
 
+    # Now create and discover a new member
+    async_fire_mqtt_message(hass, GROUP_MEMBER_3_TOPIC, GROUP_DISCOVERY_MEMBER_3_CONFIG)
+    await hass.async_block_till_done()
+
+    # Update the group discovery
+    async_fire_mqtt_message(
+        hass, GROUP_TOPIC, GROUP_DISCOVERY_LIGHT_GROUP_CONFIG_EXPANDED
+    )
+
+    await hass.async_block_till_done()
+
+    assert hass.states.get("light.member1") is not None
+    assert hass.states.get("light.member2") is not None
+    assert hass.states.get("light.member3") is not None
+    group_state = hass.states.get("light.group")
+    assert group_state is not None
+    assert group_state.attributes.get("group_entities") == [
+        "light.member1",
+        "light.member2",
+        "light.member3",
+    ]
+
 
 async def test_light_group_discovery_group_before_members(
     hass: HomeAssistant,