Inspiring

Question

CEPHtmlEngine prevents sleep

Forum|Forum|1 year ago
July 17, 2025
4 replies
388 views

When I have Illustrator (the latest version) open, the screensaver and monitor sleep do not work on macOS Sequoia. In Activity Monitor, there is something called CEPHtmlEngine, and it shows 'YES' in the Prevent Sleep section.

What is this thing, and how can I make it stop preventing sleep?

To put it mildly, it's quite annoying.

performance

O

OaktownS

Participant

The latest versionS of Illustrator and reproducible on the latest versionS of macOS Tahoe and Sequoia. You guys have enough screen recordings to suggest that this is an issue waiting on your users – so no it’s not possible to get you a short screen recording as you have been given all the information you need and the screen shots you’ve asked for have previously submitted to you by other users – there is no difference in what I or any other user would send from those.

O

OaktownS

Participant

Yeah… this is reproducible on every Mac that Illustrator runs on… and it is July 2026.

CEPHtmlEngine won’t let your computer go to sleep… and it’s all because of Illustrator 2026

Abhishek Rao

Community Manager

Hi @OaktownS,

Thank you for confirming that you're seeing the same behavior, and I'm sorry you're continuing to experience this issue.

To help us investigate further, could you please confirm your Illustrator version, macOS version, and whether this happens consistently with every Illustrator session or only under specific conditions? Also, does the issue occur with no documents open, or only after opening or working on a document?

If possible, could you share a short screen recording (or a video recorded using your phone) demonstrating the issue, including:

Illustrator running while the Mac is idle,

Activity Monitor with the Preventing Sleep column visible (showing CEPHtmlEngine),

and the system not entering sleep until Illustrator is closed.

This information will help us continue investigating the issue. We appreciate your patience and look forward to your update.

Best,

Abhishek

Abhishek Rao

Community Manager

Hi @Marius Bienius,

Thanks for your continued patience and for sharing the details earlier. Our product team has reviewed this internally and is currently unable to reproduce the issue in-house. To help us investigate this further, we’d like to arrange a debug session with you directly.

If you’re open to this, please share your contact details, including your phone number with country code, email address, and your availability with preferred time slots, via direct message(only) on the community. This will help us coordinate with the team and move this forward more effectively.

Looking forward to your update.

Abhishek

Abhishek Rao

Community Manager

Hi @Marius Bienius,

Thanks for highlighting this, completely understand how frustrating that must be. CEPHtmlEngine is part of architecture that powers panels built using HTML, like Libraries or some plugin interfaces. It's expected to run in the background, but it shouldn't interfere with system sleep.

Can you try disabling the 'Libraries' and other similar panels under Window > Extensions in Illustrator, then restart the app and check if sleep works as expected? If that helps, we'll know which panel is triggering CEPHtmlEngine to keep running actively.

Also, please confirm your exact macOS Sequoia version and Illustrator build, and if this happens even when no documents are open. If possible, share a quick screen recording showing Activity Monitor and the issue in real time. I'll check this with the team and follow up accordingly.

Looking forward to your update!

Abhishek

M

Marius BieniusAuthor

Inspiring

Hi.

Thanks for your response. Here is short screen recording:
https://www.youtube.com/watch?v=mAP1eNLMeyA

I've got Sequoia 15.5 and Illustraotor 29.5.1.

I don't quite understand the operation of disabling libraries. When I select Window > Extensions > Libraries in Illustrator, nothing happens.

I hope this helps to solve the problem.

Greatings.

Abhishek Rao

Community Manager

Hi @Marius Bienius,

Sorry for the delay in getting back to you, and thanks for the recording. Could you try testing the issue in Safe Mode to help isolate any third-party interference: https://adobe.ly/415f98E. Also, please try resetting your Illustrator workspace by going to Window > Workspace > Reset [your current workspace]. Restart Illustrator afterward and check if sleep works as expected. Finally, it would be helpful if you could test this on Illustrator 29.7.1 and let me know if the behavior is the same.

Looking forward to your update.

Abhishek

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