From df32e6bf68984a834bff3b8a9868163968d39f22 Mon Sep 17 00:00:00 2001
From: Erwin Douna <e.douna@gmail.com>
Date: Thu, 1 Oct 2026 09:44:57 +0200
Subject: [PATCH] Match SMA DHCP MAC updates on serial (#183845)

---
 homeassistant/components/sma/config_flow.py | 19 +++----------
 tests/components/sma/test_config_flow.py    | 30 +++++++++++++++++++++
 2 files changed, 33 insertions(+), 16 deletions(-)

diff --git a/homeassistant/components/sma/config_flow.py b/homeassistant/components/sma/config_flow.py
index 8ed6e6938c54..7d610768bf47 100644
--- a/homeassistant/components/sma/config_flow.py
+++ b/homeassistant/components/sma/config_flow.py
@@ -280,25 +280,12 @@ class SmaConfigFlow(ConfigFlow, domain=DOMAIN):
             self._discovery_data[CONF_MAC],
         )
 
-        existing_entries_with_host = [
-            entry
-            for entry in self._async_current_entries(include_ignore=False)
-            if entry.data.get(CONF_HOST) == self._data[CONF_HOST]
-            and not entry.data.get(CONF_MAC)
-        ]
-
-        # If we have an existing entry with the same host but no MAC address,
-        # we update the entry with the MAC address and reload it.
-        if existing_entries_with_host:
-            entry = existing_entries_with_host[0]
-            self.async_update_reload_and_abort(
-                entry, data_updates={CONF_MAC: self._data[CONF_MAC]}
-            )
-
         if not (match := HOSTNAME_SERIAL.match(discovery_info.hostname)):
             return self.async_abort(reason="not_supported")
         await self.async_set_unique_id(match.group(1))
-        self._abort_if_unique_id_configured(updates={CONF_HOST: self._data[CONF_HOST]})
+        self._abort_if_unique_id_configured(
+            updates={CONF_HOST: self._data[CONF_HOST], CONF_MAC: self._data[CONF_MAC]}
+        )
 
         return await self.async_step_discovery_confirm()
 
diff --git a/tests/components/sma/test_config_flow.py b/tests/components/sma/test_config_flow.py
index 725e53705c9e..32e2a9a97ed8 100644
--- a/tests/components/sma/test_config_flow.py
+++ b/tests/components/sma/test_config_flow.py
@@ -242,6 +242,36 @@ async def test_dhcp_already_configured_duplicate(
     )
 
 
+@pytest.mark.parametrize(
+    ("hostname", "result_type"),
+    [
+        pytest.param("SMA987654321", FlowResultType.FORM, id="other_serial"),
+        pytest.param("evcharger", FlowResultType.ABORT, id="not_sma"),
+    ],
+)
+async def test_dhcp_other_device_on_same_host(
+    hass: HomeAssistant,
+    mock_config_entry: MockConfigEntry,
+    hostname: str,
+    result_type: FlowResultType,
+) -> None:
+    """Test another device on the host of an entry doesn't change that entry."""
+    mock_config_entry.add_to_hass(hass)
+
+    result = await hass.config_entries.flow.async_init(
+        DOMAIN,
+        context={"source": SOURCE_DHCP},
+        data=DhcpServiceInfo(
+            ip=mock_config_entry.data[CONF_HOST],
+            hostname=hostname,
+            macaddress="0015bb00ffff",
+        ),
+    )
+
+    assert result["type"] is result_type
+    assert CONF_MAC not in mock_config_entry.data
+
+
 @pytest.mark.parametrize(
     ("hostname", "unique_id"),
     [