Xcode 10.1 Beta 3 was released on 15 Oct 2018 and requires macOS 10.13.6+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_10.1_Beta_3/Xcode_10.1_Beta_3.xip.
Release notes are located at https://developer.apple.com/documentation/xcode_release_notes/xcode_10_1_beta_3_release_notes.
The SDKs it contains are:
- iOS 12.1 (Build 16B5084a)
- macOS 10.14.1 (Build 18B64a)
- tvOS 12.1 (Build 16J5600a)
- watchOS 5.1 (Build 16R5584a)
The compilers it contains are:
- clang 10.0.0 (Build 1000.11.45.5)
- swift 4.2.1 (Build 1000.11.42)