Although I have been a happy user of macOS Sonoma since its first developer beta-release, I’ve been experiencing strange behaviour on one of my Macs that has now become more than a background niggle. As this only appears to affect one of them, I’m asking whether this is something peculiar to that system, or more widespread. It involves Accessibility and brief episodes of impaired responsiveness. Is anyone else running Sonoma experiencing similar?

My old iMac Pro remains my daily workhorse for routine tasks, including writing articles for this blog. I’m still in the process of a slow migration to my Mac Studio M1 Max, but for the moment use the iMac for most production tasks. Occasionally, at seemingly random intervals, the fans in the iMac blow, and its responsiveness suffers, just for a few seconds. Activity Monitor reveals that the process that’s suddenly consuming high CPU % at the time is universalaccessd, which is typically taking over 100% for a period of a few seconds, then drops back to a far lower percentage as responsiveness returns.

This typically occurs when window focus is changed, by bringing another window to the front. However, that action doesn’t normally cause this burst of activity from universalaccessd, only occasionally.

I have tinkered with Accessibility settings, disabled Stage Manager, and watched to see whether any specific app is involved, but so far have been unable to link this behaviour with anything, nor to prevent it from happening.

What’s even more mysterious are the log excerpts that I have obtained from these episodes. When universalaccessd is taking large amounts of CPU, the log is filling with a barrage of entries, in groups of 5 repeated every 0.004 seconds for a period of about half a second. Entries aren’t flagged as errors, although they appear to be from their contents:
gui/501 launchd could not find active service for lookup: pid = 88966, name = com.apple.axserver
user/501 launchd could not find active service for lookup: pid = 88966, name = com.apple.axserver
system launchd could not find active service for lookup: pid = 88966, name = com.apple.axserver
gui/501 launchd failed lookup: name = com.apple.axserver, handle = 88966, flags = 0x3, requestor = universalaccess[465], error = 3: No such process
universalaccessd AccessibilityFoundation AXFUIElement Timeout: [pid: 88966] [thread: ] [request: _AXFUIElementCopyAttributeValue] [info: AXRole]

These occur in barrages of tens of thousands but only when universalaccessd is taking high CPU %. There’s nothing in the log entries either before or after a barrage of entries that appears to be responsible or related in any way, they simply appear, fill the log for half a second or so, then vanish again.

If that isn’t odd enough, I’m unable to find any reference to com.apple.axserver, although those entries demonstrate that macOS is looking for it in three different groups of processes:

• user processes and apps (gui/501)
• user-owned background processes (user/501)
• system processes (system)

then a second time in user processes and apps.

There’s no process listed in Activity Monitor as com.apple.axserver or axserver. Neither is there any LaunchAgent or LaunchDaemon named com.apple.axserver, nor can I find any reference to axserver in any bundle in /System/Library.

Checking my Mac Studio draws a complete blank: I have been unable to provoke any similar problem, nor can I find any trace of com.apple.axserver or axserver there. I have seen similar reports elsewhere, and other users have tried similar solutions in a bid to stop this odd and mildly disruptive behaviour, but so far no one appears to have been successful.

Have you seen this in macOS Sonoma? Has anyone any ideas? While I’m prepared to report this to Apple in Feedback, at the moment the information is too vague to enable an engineer to reproduce the problem, and I suspect that it would remain unsolved.