Fix 'Cannot load underlying module for UIKit' Error in VSCode for iOS Swift Development

A quick note for those encountering the Cannot load underlying module for 'UIKit' error from SourceKit when developing Swift for iOS in VSCode.

Add Settings to settings.json

Replace 18.1 with your appropriate version.

{
    "swift.swiftSDK": "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator18.1.sdk",
    "swift.sourcekit-lsp.serverArguments": [
        "-Xswiftc",
        "-sdk",
        "-Xswiftc",
        "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator18.1.sdk",
        "-Xswiftc",
        "-target",
        "-Xswiftc",
        "arm64-apple-ios18.1-simulator"
    ]
}

Environment at Time of Writing

$ code --version
1.97.2
e54c774e0add60467559eb0d1e229c6452cf8447
arm64

$ code --list-extensions --show-versions | grep swift
swiftlang.swift-vscode@2.0.2

$ swift --version
swift-driver version: 1.115 Apple Swift version 6.0.2 (swiftlang-6.0.2.1.2 clang-1600.0.26.4)
Target: arm64-apple-macosx15.0

$ xcodebuild -version
Xcode 16.1
Build version 16B40

$ xcrun simctl list runtimes
== Runtimes ==
iOS 18.1 (18.1 - 22B81) - com.apple.CoreSimulator.SimRuntime.iOS-18-1

$ LANG=C date
Mon Feb 24 04:50:52 JST 2025