SteamOS 3.8.25: HDMI-CEC incorrectly switches TV from HDMI 1 to HDMI 3

System information

• Device: Steam Deck OLED 1 TB
• SteamOS: 3.8.25 Beta
• Steam Client: Beta
• SteamRT 3 experimental client: Enabled
• Dock: JSAUX HB0603S
• TV: LG 49UH6109
• Steam Deck connected directly to TV HDMI 1
• AV receiver connected to TV HDMI 3

Description

Since updating to SteamOS 3.8.25 Beta, the TV incorrectly switches from HDMI 1 to HDMI 3 whenever the Steam Deck is connected through the dock.

HDMI 3 is connected to my AV receiver. The receiver may be powered off, but the TV still switches to HDMI 3. When I manually switch the TV back to HDMI 1, it automatically switches back to HDMI 3.

This issue was not present with SteamOS 3.7.x, SteamOS 3.8.16 Stable, or SteamOS 3.8.24 Beta. It began with SteamOS 3.8.25 Beta.

The Steam Deck is connected directly to HDMI 1. The AV receiver is not between the Steam Deck and the TV.

Steps to reproduce

1. Connect the JSAUX HB0603S dock directly to the TV's HDMI 1 port.
2. Connect the AV receiver to HDMI 3.
3. Connect the Steam Deck to the dock.
4. Observe that the TV switches to HDMI 3.
5. Manually switch the TV back to HDMI 1.
6. Observe that the TV switches back to HDMI 3.

Turning on the AV receiver temporarily resolves the behavior.

Expected behavior

The TV should remain on HDMI 1, the input directly connected to the Steam Deck dock.

Actual behavior

The TV switches to HDMI 3, which is connected to the AV receiver, even when the receiver is powered off.

System report

The SteamOS 3.8.25 system report contains repeated HDMI-CEC-related entries, including:

• CEC device activation and deactivation
• Audio logical-address changes
• Physical address changing from 4096 to 65535
• Failed to add display topology, DTM TA is not initialized

These entries may be related to the incorrect HDMI input switching.

The issue appears to be related to HDMI-CEC, display topology, or HDMI hotplug handling introduced or changed in SteamOS 3.8.25.

Start with the SteamOS 3.8.25 system report and review the repeated HDMI-CEC, display-topology, and HDMI hotplug entries, including the physical-address change and DTM initialization failure. Compare the behavior with the listed 3.8.x versions and verify that the TV remains on HDMI 1 when the dock is connected, including with the receiver powered off.