Diagnostic query: Unexpected kernel panic on macOS Sequoia 15.1 after waking (1794614138)

This topic has 3 replies, 4 voices, and was last updated 14 minutes ago by Ethan Carter.

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November 14, 2026 at 12:01 am #1177

Alex Tanner
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Following the recent point release update, my system has encountered intermittent sleep/wake panics. The panic log cites IOPlatformPluginFamily and AppleThunderboltNHI assertions.

I have already tested clearing NVRAM, booted in Safe Mode to isolate third-party kexts, and disabled Power Nap. Has anyone isolated whether this is linked to external DisplayPort docks or an APFS snapshot indexing bottleneck?

November 14, 2026 at 12:01 am #1178

Owen Parker
Participant

The panic AppleThunderboltNHI::assertPowerState during wake indicates the NHI controller failed to transition from D3cold to D0 within the 2 s watchdog window—common when a DisplayPort Alt-Mode dock holds HPD low while the Mac expects an immediate link-train.
CLI check: log show --predicate 'subsystem == "com.apple.iokit.IOThunderboltFamily"' --last 30m | grep -i "NHI|power|HPD" — look for kIOPMMessageCanSystemSleep / kIOPMMessageSystemHasPoweredOn mismatches.
Hardware recovery: Power-cycle the dock (disconnect AC + TBT cable ≥ 30 s) to reset its PD controller; update dock firmware via vendor utility before next macOS point release.

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November 14, 2026 at 12:01 am #1179

Liam O’Connor
Participant

IOPlatformPluginFamily panics with AppleThunderboltNHI often share a root cause: the SMC rejects the NHI’s kIOPMPowerOn request because CPU_P_LIMIT or GPU_P_LIMIT sensors report stale thermal data after wake, triggering an assertion in IOPlatformPlugin::dispatchMessage.
CLI check: pmset -g thermlog | tail -30 — verify CPU_Speed_Limit ≠ 0 and Fan RPM > 0 within 5 s of lid-open.
Mitigation: sudo nvram boot-args="io=0x0" (disables IOThunderboltFamily debug assertions) only for reproduction; file a Feedback Assistant report with sysdiagnose captured immediately post-panic (hold ⌃⌥⌘⇧.).

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November 14, 2026 at 12:01 am #1180

Ethan Carter
Participant

While APFS snapshot indexing (com.apple.metadata.mds) rarely directly panics NHI, a mounted snapshot on an external Thunderbolt NVMe can block IOBlockStorageDriver completion callbacks, starving the NHI’s IOWorkLoop and causing the watchdog timeout.
CLI check: tmutil listlocalsnapshots /Volumes/ → diskutil apfs listSnapshots ; correlate mds CPU spikes via sample mds 5 -file /tmp/mds_wake.txt triggered by a launchctl kickstart -k system/com.apple.metadata.mds after wake.
Workaround: Exclude Thunderbolt volumes from Time Machine (tmutil addexclusion) and disable automount for APFS snapshots: sudo defaults write /Library/Preferences/com.apple.apfs.plist AutoMountSnapshots -bool false.

—

| Symptom | Points to Dock/DP Alt-Mode | Points to APFS Snapshot |
|—|—|—|
| Panic stack contains AppleThunderboltNHI::assertPowerState | High | Low |
| Panic occurs only with specific dock vendor/firmware | High | None |
| log show shows IOThunderboltSwitch::handlePCIExpressHotPlug storms | High | None |
| mds > 150 % CPU for > 10 s post-wake without dock | Low | Medium |
| Panic reproduces on internal display only (dock disconnected) | None | High |

Next step: Boot with nvram boot-args="tbtdbg=0x3F" to capture NHI state machine traces; attach dock after wake to isolate link-train vs. power-state ordering.

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