brightness_step sets all lights to the same average-based brightness for grouped hue lights

[agoode]

The problem

Example:

light.music_room_lamps is a hue grouped_light consisting of 2 lamps. One is at 25% brightness, the second is 75%.

I make this service call:

service: light.turn_on
target:
  entity_id: light.music_room_lamps
data:
  brightness_step_pct: 10

Expected:
Lamp 1 is at 35% brightness, lamp 2 is 85%.

Actual:
Both lamps are set to the previous average value + 10 = 60%.

This is because the core light integration reads the current brightness value, adds the step to it, then sets the value as the new brightness. But grouped lights return the average brightness of all lit lights for brightness.

The API provides dimming_delta for grouped_light. This is already exposed by aiohue. Home Assistant should use this API to ensure grouped lights can move in sync and to each correct step value.

This probably needs to be fixed in the core light integration, but I wanted to start here since this is the device I have. I assume this problem affects other integrations like zigbee that have an internal concept of light groups.

What version of Home Assistant Core has the issue?

core-2024.5.4

What was the last working version of Home Assistant Core?

No response

What type of installation are you running?

Home Assistant OS

Integration causing the issue

Philips Hue

Link to integration documentation on our website

https://www.home-assistant.io/integrations/hue/

Diagnostics information

config_entry-hue-fd830b57f44697df0c68b2267fd01f12.json

Example YAML snippet

service: light.turn_on
target:
  entity_id: light.music_room_lamps
data:
  brightness_step_pct: 10

Anything in the logs that might be useful for us?

No response

Additional information

No response

[home-assistant]

Hey there @balloob, @marcelveldt, mind taking a look at this issue as it has been labeled with an integration (hue) you are listed as a code owner for? Thanks!

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