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M
Marius Bienius
Inspiring
July 17, 2025
Question

CEPHtmlEngine prevents sleep

  • July 17, 2025
  • 2 replies
  • 251 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.

 

    2 replies

    Abhishek Rao
    Community Manager
    Abhishek RaoCommunity Manager
    Community Manager
    February 12, 2026

    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
    Abhishek RaoCommunity Manager
    Community Manager
    July 17, 2025

    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
    July 21, 2025

    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
    Abhishek RaoCommunity Manager
    Community Manager
    August 14, 2025

    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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