After installing Xcode 7 I can't build and run projects anymore as document fails to open

EDIT: This question refers to teh pre-release version of Xcode 7, hence it may not be relevant if you are running the currently released version as some issues may have been fixed.

I get the following:

Failed to connect with the iOS agent. Please file a bug report at bugreport.apple.com.

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Why is that?

If I look at the details I get:

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ERROR:

Failed to find or create execution context for description System content 1x for IBCocoaTouchFramework-EightAndLater w/ default fidelity (Failure reason: Software caused connection abort): Failed to find newest available Simulator runtime (Failure reason: Software caused connection abort): Simulator verification failed. (Failure reason: A connection to the simulator verification service could not be established.)

Error Domain=NSPOSIXErrorDomain Code=53 "Failed to find or create execution context for description System content 1x for IBCocoaTouchFramework-EightAndLater w/ default fidelity" UserInfo=0x7fcf5961ebd0 {NSLocalizedDescription=Failed to find or create execution context for description System content 1x for IBCocoaTouchFramework-EightAndLater w/ default fidelity, NSUnderlyingError=0x7fcf58b72950 "Failed to find newest available Simulator runtime"}

Solution

I am not sure which answer to accept as for me what worked was installing a later beta (beta 5). I had filed a bug to Apple a couple of months ago so I assume they solved this problem by updating Xcode.

Anyone experiencing this with the current official release?

I post this as answer for now but if anyone has a more detailed explanation I will be happy to remove my answer and accept yours.