From 8025b2ba3c7fa97a5b4a5eefbdf86fe1c5a549e2 Mon Sep 17 00:00:00 2001
From: "J. Nick Koston" <nick@koston.org>
Date: Thu, 23 Jul 2026 08:28:59 -1000
Subject: [PATCH] Fix homekit_controller sending zero brightness for low
 brightness values (#177148)

---
 .../components/homekit_controller/light.py    |  7 +++--
 .../homekit_controller/test_light.py          | 29 +++++++++++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/homeassistant/components/homekit_controller/light.py b/homeassistant/components/homekit_controller/light.py
index fd08872fc8ef..c49083a12651 100644
--- a/homeassistant/components/homekit_controller/light.py
+++ b/homeassistant/components/homekit_controller/light.py
@@ -188,8 +188,11 @@ class HomeKitLight(HomeKitEntity, LightEntity):
         characteristics: dict[str, Any] = {}
 
         if brightness is not None:
-            characteristics[CharacteristicsTypes.BRIGHTNESS] = int(
-                brightness * 100 / 255
+            # Some devices such as Nanoleaf Essentials treat brightness 0
+            # with on as full brightness; a real brightness 0 is handled
+            # as turn_off by the light component.
+            characteristics[CharacteristicsTypes.BRIGHTNESS] = max(
+                1, int(brightness * 100 / 255)
             )
 
         # If they send both temperature and hs_color, and the device
diff --git a/tests/components/homekit_controller/test_light.py b/tests/components/homekit_controller/test_light.py
index c656507ffaf3..3b3ad971b5d0 100644
--- a/tests/components/homekit_controller/test_light.py
+++ b/tests/components/homekit_controller/test_light.py
@@ -7,6 +7,7 @@ from aiohomekit.model import Accessory
 from aiohomekit.model.characteristics import CharacteristicsTypes
 from aiohomekit.model.services import Service, ServicesTypes
 from aiohomekit.testing import FakeController
+import pytest
 
 from homeassistant.components.homekit_controller.const import KNOWN_DEVICES
 from homeassistant.components.light import (
@@ -60,6 +61,34 @@ def create_lightbulb_service_with_color_temp(accessory: Accessory) -> Service:
     return service
 
 
+@pytest.mark.parametrize("brightness", [1, 2, 3])
+async def test_turn_on_low_brightness_no_zero(
+    hass: HomeAssistant, get_next_aid: Callable[[], int], brightness: int
+) -> None:
+    """Test low brightness values never send 0 percent to the device.
+
+    Sending brightness 0 with on results in full brightness on some
+    devices such as Nanoleaf Essentials bulbs.
+    """
+    helper = await setup_test_component(
+        hass, get_next_aid(), create_lightbulb_service_with_hs
+    )
+
+    await hass.services.async_call(
+        "light",
+        "turn_on",
+        {"entity_id": "light.testdevice", "brightness": brightness},
+        blocking=True,
+    )
+    helper.async_assert_service_values(
+        ServicesTypes.LIGHTBULB,
+        {
+            CharacteristicsTypes.ON: True,
+            CharacteristicsTypes.BRIGHTNESS: 1,
+        },
+    )
+
+
 async def test_switch_change_light_state(
     hass: HomeAssistant, get_next_aid: Callable[[], int]
 ) -> None: