MacBook Pro wakes from sleep within 30 seconds only when bus-powered USB‑C SSD is attached to a hub

Environment

MacBook Pro 16-inch (Apple silicon, macOS 13.4), bus-powered USB‑C hub (no external power) with a Samsung T7 NVMe enclosure attached. Finder shows SSD formatted APFS. SMC-equivalent (for Apple silicon) not user-accessible; NVRAM and Safe Boot attempted.

Symptoms

Laptop reliably enters sleep, but wakes automatically after ~20–40 seconds only when the SSD is connected through the hub. Sleep works normally with no hub or with the SSD connected directly to a different USB‑C port with a powered hub. Wakes show 'Wake reason: USB' in pmset -g log.

Observations

pmset -g log and log show repeated USB wake events; IORegistryExplorer (ioreg) shows the SSD device disconnecting and reconnecting on wake. System logs include 'USB device attached' followed by 'IOUSBHostHIDDevice' entries. Energy Saver settings are default; Wake for network access is off. The hub's LED flickers before wake events.

Already attempted

Tested on two different USB‑C hubs (both bus-powered) and one powered hub; only bus-powered hubs cause the immediate wake. Reset NVRAM and performed Safe Boot (no change). Updated macOS to latest point release. Replaced the USB‑C cable and tried direct connection (no wake). Experimented with disabling 'Allow Bluetooth devices to wake this computer' (no effect).

Question

What is causing the wake-from-sleep when a bus-powered hub + SSD is attached, and which logs or diagnostic steps will safely identify whether this is a device hotplug, power negotiation (PD) issue, or kernel/IOKit USB driver bug? What reversible mitigations are recommended so the SSD can remain attached without waking the Mac?

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AI DIAGNOSTICS

Incident analysis

Updated 1w ago• Trouble ID

Most likely causes

Bus-powered hub or SSD enclosure draws brief surge current during sleep causing the hub to reset the upstream port, generating a USB attach event. 90%

Hub or SSD firmware incorrectly implements selective suspend or U1/U2 link power states; on sleep this triggers re-enumeration. 65%

USB‑C Power Delivery role or CC line negotiation changes at sleep transition, interpreted as device connect by macOS. 35%

Summary

pmset logs showing USB as the wake reason plus intermittent device disconnect/reconnect point to the hub/SSD performing a short reset or reenumeration that the kernel interprets as a wake event. Because the CPU/system wakes on USB device attach, the likely root causes are: the hub's power budget or cable allowing transient power drops as the system settles into sleep; the hub or enclosure performing a link training or spin-up audible event that triggers USB re-enumeration; or a macOS USB driver reacting to a non-compliant USB-C PD or USB-C Power Role change. Differences between bus-powered and externally powered hubs strongly implicate power negotiation/hub behavior.

Suggested Fixes

Diagnostic step 1

Reproduce with console and pmset -g log; capture system.log while entering sleep and waiting for the wake to capture exact kernel messages for the downstream port.

Diagnostic step 2

Test with a powered USB‑C hub (confirmed as working in your tests). If a powered hub prevents wake, prefer that as a workaround.

Diagnostic step 3

Try a different bus-powered hub of known compatibility or a different SSD enclosure to isolate whether hub or enclosure is at fault; if only one vendor reproduces, file a firmware/compatibility bug with that vendor.