Xcode Preview Error 879

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Created Apr ’21

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Hi. I've run into the following error message that prevents me from live previews. I'm running Xcode 12.4 on Big Sur 11.3 Beta 7. Please help.

Code Block HumanReadableNSError: connectToPreviewHost: Failed to connect to 879: Error Domain=com.apple.dt.ProcessAttachUtilities Code=3 "Attach to 879 failed; an unknown error occurred" UserInfo={NSLocalizedDescription=Attach to 879 failed; an unknown error occurred}
com.apple.dt.xcodepreviews.service (17):

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Answer 1

Developer Tools Engineer OP

Apple

May ’21

Hi,

Apologies it took us so long to get back to you.

I'm sorry to hear you are having problems getting previews working. Best next step will be to file a feedback with diagnostics. We will need the diagnostics Xcode Previews generates in order to make sure we understand the error the previews system is encountering.

When you get an error in Xcode Previews, an error banner appears in the canvas
Click the "Diagnostics" button in that banner
In the sheet that appears, click "Generate Report" in the bottom left of the sheet
Attach (or make from the folder) the resulting zip file to the bug (will be named something like previews-diagnostics-0123456789.zip)

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