diff --git a/Sources/XcodesKit/Models+Runtimes.swift b/Sources/XcodesKit/Models+Runtimes.swift
index 6463569..66f0636 100644
--- a/Sources/XcodesKit/Models+Runtimes.swift
+++ b/Sources/XcodesKit/Models+Runtimes.swift
@@ -11,7 +11,7 @@ struct DownloadableRuntimesResponse: Decodable {
 public struct DownloadableRuntime: Decodable {
     let category: Category
     let simulatorVersion: SimulatorVersion
-    let source: String
+    let source: String?
     let dictionaryVersion: Int
     let contentType: ContentType
     let platform: Platform
@@ -79,6 +79,7 @@ extension DownloadableRuntime {
     enum ContentType: String, Decodable {
         case diskImage = "diskImage"
         case package = "package"
+        case cryptexDiskImage = "cryptexDiskImage"
     }
 
     enum Platform: String, Decodable {
diff --git a/Sources/XcodesKit/RuntimeInstaller.swift b/Sources/XcodesKit/RuntimeInstaller.swift
index cf0821c..34189e8 100644
--- a/Sources/XcodesKit/RuntimeInstaller.swift
+++ b/Sources/XcodesKit/RuntimeInstaller.swift
@@ -112,6 +112,8 @@ public class RuntimeInstaller {
                 try await installFromPackage(dmgUrl: dmgUrl, runtime: matchedRuntime)
             case .diskImage:
                 try await installFromImage(dmgUrl: dmgUrl)
+            case .cryptexDiskImage:
+                throw Error.unsupportedCryptexDiskImage
         }
         if shouldDelete {
             Current.logging.log("Deleting Archive")
@@ -183,7 +185,10 @@ public class RuntimeInstaller {
 
     @MainActor
     public func downloadOrUseExistingArchive(runtime: DownloadableRuntime, to destinationDirectory: Path, downloader: Downloader) async throws -> URL {
-        let url = URL(string: runtime.source)!
+        guard let source = runtime.source else {
+            throw Error.missingRuntimeSource(runtime.identifier)
+        }
+        let url = URL(string: source)!
         let destination = destinationDirectory/url.lastPathComponent
         let aria2DownloadMetadataPath = destination.parent/(destination.basename() + ".aria2")
         var aria2DownloadIsIncomplete = false
@@ -226,6 +231,8 @@ extension RuntimeInstaller {
         case unavailableRuntime(String)
         case failedMountingDMG
         case rootNeeded
+        case missingRuntimeSource(String)
+        case unsupportedCryptexDiskImage
 
         public var errorDescription: String? {
             switch self {
@@ -235,6 +242,10 @@ extension RuntimeInstaller {
                     return "Failed to mount image."
                 case .rootNeeded:
                     return "Must be run as root to install the specified runtime"
+                case let .missingRuntimeSource(identifier):
+                    return "Runtime \(identifier) is missing source url."
+                case .unsupportedCryptexDiskImage:
+                    return "Cryptex Disk Image is not yet supported."
             }
         }
     }
diff --git a/Tests/XcodesKitTests/Fixtures/DownloadableRuntimes.plist b/Tests/XcodesKitTests/Fixtures/DownloadableRuntimes.plist
index 4229254..46d8a23 100644
--- a/Tests/XcodesKitTests/Fixtures/DownloadableRuntimes.plist
+++ b/Tests/XcodesKitTests/Fixtures/DownloadableRuntimes.plist
@@ -1794,7 +1794,34 @@
                 <key>version</key>
                 <string>1.0.0.1</string>
             </dict>
-	</array>
+            <dict>
+                <key>category</key>
+                <string>simulator</string>
+                <key>contentType</key>
+                <string>cryptexDiskImage</string>
+                <key>dictionaryVersion</key>
+                <integer>2</integer>
+                <key>downloadMethod</key>
+                <string>mobileAsset</string>
+                <key>fileSize</key>
+                <integer>8455760175</integer>
+                <key>identifier</key>
+                <string>com.apple.dmg.iPhoneSimulatorSDK18_0_b1</string>
+                <key>name</key>
+                <string>iOS 18.0 beta Simulator Runtime</string>
+                <key>platform</key>
+                <string>com.apple.platform.iphoneos</string>
+                <key>simulatorVersion</key>
+                <dict>
+                    <key>buildUpdate</key>
+                    <string>22A5282m</string>
+                    <key>version</key>
+                    <string>18.0</string>
+                </dict>
+                <key>version</key>
+                <string>18.0.0.1</string>
+            </dict>
+        </array>
         <key>refreshInterval</key>
         <integer>86400</integer>
         <key>sdkToSeedMappings</key>
diff --git a/Tests/XcodesKitTests/Fixtures/LogOutput-Runtimes.txt b/Tests/XcodesKitTests/Fixtures/LogOutput-Runtimes.txt
index 591f086..cedde68 100644
--- a/Tests/XcodesKitTests/Fixtures/LogOutput-Runtimes.txt
+++ b/Tests/XcodesKitTests/Fixtures/LogOutput-Runtimes.txt
@@ -25,6 +25,7 @@ iOS 16.2
 iOS 16.4
 iOS 17.0-beta1
 iOS 17.0-beta2
+iOS 18.0-beta1
 -- watchOS --
 watchOS 6.0
 watchOS 6.1.1
diff --git a/Tests/XcodesKitTests/RuntimeTests.swift b/Tests/XcodesKitTests/RuntimeTests.swift
index 314761a..04f6c89 100644
--- a/Tests/XcodesKitTests/RuntimeTests.swift
+++ b/Tests/XcodesKitTests/RuntimeTests.swift
@@ -80,7 +80,7 @@ final class RuntimeTests: XCTestCase {
     func test_downloadableRuntimes() async throws {
         mockDownloadables()
         let values = try await runtimeList.downloadableRuntimes().downloadables
-        XCTAssertEqual(values.count, 59)
+        XCTAssertEqual(values.count, 60)
     }
 
     func test_downloadableRuntimesNoBetas() async throws {
@@ -171,7 +171,7 @@ final class RuntimeTests: XCTestCase {
         }
 
         let url = try await runtimeInstaller.downloadOrUseExistingArchive(runtime: runtime, to: .xcodesCaches, downloader: .urlSession)
-        let fileName = URL(string: runtime.source)!.lastPathComponent
+        let fileName = URL(string: runtime.source!)!.lastPathComponent
         XCTAssertEqual(url, Path.xcodesCaches.join(fileName).url)
         XCTAssertNil(xcodeDownloadURL)
     }
@@ -185,10 +185,10 @@ final class RuntimeTests: XCTestCase {
             return (Progress(), Promise.value((destination, HTTPURLResponse(url: url.pmkRequest.url!, statusCode: 200, httpVersion: nil, headerFields: nil)!)))
         }
         let runtime = try await runtimeList.downloadableRuntimes().downloadables.first { $0.visibleIdentifier == "iOS 15.5" }!
-        let fileName = URL(string: runtime.source)!.lastPathComponent
+        let fileName = URL(string: runtime.source!)!.lastPathComponent
         let url = try await runtimeInstaller.downloadOrUseExistingArchive(runtime: runtime, to: .xcodesCaches, downloader: .urlSession)
         XCTAssertEqual(url, Path.xcodesCaches.join(fileName).url)
-        XCTAssertEqual(xcodeDownloadURL, URL(string: runtime.source)!)
+        XCTAssertEqual(xcodeDownloadURL, URL(string: runtime.source!)!)
     }
 
     func test_installStepsForPackage() async throws {