External display black on wake when built-in display is disconnected

[toobuntu]

When "Disconnect the built-in display when an external display is connected" is enabled, waking from sleep leaves the external display black with only the mouse pointer visible. The built-in remains off as expected. Physically unplugging and replugging the external display restores it.

The kernel log shows the external display going through two link negotiations on wake. The first lands in RGB 4:4:4 8bpc; the HDCP subsystem then resets the link (abortHDCPNegotiation 0xe00002eb) and the second negotiation lands in YCbCr 4:4:4 10bpc due to the monitor's defective EDID advertising YCbCr support. The black screen may be the display stuck between these two negotiation phases.

Env:
BetterDisplay 4.1.5
macOS 26.3
Connection: MacBook Air M2 (2022) (Mac14,2) USB-C → Anker AK-A8176011 passive USB-C to HDMI cable → DELL SP2309W HDMI input.

[waydabber]

Hmm. I am not really sure what could be the problem. You can try configuring the app to automatically reinitialize the display on wake and/or configure a color mode with Configuration Protection, maybe that helps if this causes the issue.

[berkbb]

I have this issue too. iMac + LG Utragear. LG goes screen black when new virtual monitor connected on BetterDisplay 4.1.5 and
macOS 26.3. Monitor connnected via dispalyPort -> ThunderBolt 3 cable.

[toobuntu]

Confirmed that configuring the app to automatically reinitialize the display on wake fixes it for me.

The common thread between my repro and berkbb's appears to be a non-default display topology at sleep time (built-in suppressed, virtual display).

For me, it usually correlates with built-in display suppressed + battery sleep + clamshell closed during sleep. But I've now seen it persist through an AC wake, suggesting the failure is established at sleep time rather than wake time. A CGConfig no-op recommit post-wake — which might be related to what BetterDisplay's reinitialize does internally — also resolves it without the flicker of a display-sleep via hot corner (Settings > Desktop & Dock > Hot Corners...) or pmset displaysleepnow or the bother of unplugging/replugging the external display.

@berkbb:

1. Does it happen on every sleep/wake or only sometimes? For me, not every time.
2. Is a virtual display active at sleep time? For me, the built-in is suppressed.
3. Does a hot corner display-sleep workaround recover it? For me, this also fixes it.

[berkbb]

Hi @toobuntu ,

1. It happens only on first open / disconnect-connect of virtual monitor for me.
2. Same as you.
3. I will try it.