From c24e291017c1e81fa26d5d11fd8e3b86c807a306 Mon Sep 17 00:00:00 2001
From: Jack Kingsman <jack.kingsman@gmail.com>
Date: Sun, 12 Apr 2026 14:59:41 -0700
Subject: [PATCH] Destroy old discovery topics when the radio key changes

---
 app/fanout/mqtt_ha.py |  6 +++++-
 tests/test_mqtt_ha.py | 50 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/app/fanout/mqtt_ha.py b/app/fanout/mqtt_ha.py
index 094c651..635f1f3 100644
--- a/app/fanout/mqtt_ha.py
+++ b/app/fanout/mqtt_ha.py
@@ -519,12 +519,16 @@ class MqttHaModule(FanoutModule):
 
             if key_changed:
                 old_key = self._radio_key
+                old_topics = list(self._discovery_topics)
+                if old_topics:
+                    await self._clear_retained_topics(old_topics)
+                    self._discovery_topics.clear()
                 self._radio_key = pub_key
                 self._radio_name = new_name
                 # Remove stale discovery entries from the old identity (e.g.
                 # "unknown" placeholder from before the radio key was known),
                 # then re-publish with the real identity.
-                if old_key is not None:
+                if old_key is not None and not old_topics:
                     await self._clear_retained_topics(
                         [t for t, _ in _radio_discovery_configs(self._prefix, old_key, "")]
                     )
diff --git a/tests/test_mqtt_ha.py b/tests/test_mqtt_ha.py
index d8973fc..c96ff0f 100644
--- a/tests/test_mqtt_ha.py
+++ b/tests/test_mqtt_ha.py
@@ -286,6 +286,56 @@ class TestMqttHaHealth:
         assert mod._radio_key == "aabbccddeeff"
         assert mod._radio_name == "MyRadio"
 
+    @pytest.mark.asyncio
+    async def test_on_health_key_change_clears_all_existing_discovery_topics(self):
+        mod = MqttHaModule("test", _base_config())
+        mod._publisher = MagicMock()
+        mod._publisher.connected = True
+        mod._publisher.publish = AsyncMock()
+        mod._radio_key = "aabbccddeeff"
+        mod._radio_name = "OldRadio"
+        mod._discovery_topics = [
+            "homeassistant/sensor/meshcore_aabbccddeeff/noise_floor/config",
+            "homeassistant/event/meshcore_aabbccddeeff/messages/config",
+            "homeassistant/device_tracker/meshcore_ccdd11223344/config",
+            "homeassistant/sensor/meshcore_eeff11223344/battery_voltage/config",
+        ]
+
+        mod._clear_retained_topics = AsyncMock()
+
+        async def publish_discovery_side_effect():
+            assert mod._discovery_topics == []
+            mod._discovery_topics = [
+                "homeassistant/sensor/meshcore_112233445566/noise_floor/config",
+                "homeassistant/event/meshcore_112233445566/messages/config",
+            ]
+
+        mod._publish_discovery = AsyncMock(side_effect=publish_discovery_side_effect)
+
+        await mod.on_health(
+            {
+                "connected": True,
+                "public_key": "112233445566",
+                "name": "NewRadio",
+            }
+        )
+
+        mod._clear_retained_topics.assert_awaited_once_with(
+            [
+                "homeassistant/sensor/meshcore_aabbccddeeff/noise_floor/config",
+                "homeassistant/event/meshcore_aabbccddeeff/messages/config",
+                "homeassistant/device_tracker/meshcore_ccdd11223344/config",
+                "homeassistant/sensor/meshcore_eeff11223344/battery_voltage/config",
+            ]
+        )
+        mod._publish_discovery.assert_awaited_once()
+        assert mod._radio_key == "112233445566"
+        assert mod._radio_name == "NewRadio"
+        assert mod._discovery_topics == [
+            "homeassistant/sensor/meshcore_112233445566/noise_floor/config",
+            "homeassistant/event/meshcore_112233445566/messages/config",
+        ]
+
 
 class TestMqttHaLifecycle:
     @pytest.mark.asyncio