Xcode 16 broke my SwiftData application

I'm building an application with SwiftUI and SwiftData. Up until a couple days ago, everything was working fine. Then, Xcode auto-updated to v16 in the background, and the next time I opened Xcode and tried to build my app it wouldn't build anymore, citing some errors in expanding the SwiftData @Model macro on one of my objects. Attached are the errors specifically, shown where Xcode shows them (in the expanded @Model macro). In text, they are:

• Instance method 'access(_:keyPath:)' requires that 'Member' conform to 'Observable'
• Cannot convert value of type 'Risers.Member' to expected argument type 'Member'
• Instance method 'withMutation(of:keyPath:_:)' requires that 'Member' conform to 'Observable'
• Cannot convert value of type 'Risers.Member' to expected argument type 'Member'

Here is the SwiftData class in full:

import SwiftData
import SwiftUI

@Model
class Member: Identifiable, Hashable {
    var chorus: Chorus?

    var id = UUID()

    var firstName: String
    var lastName: String
    var fullName: String {
        "\(firstName) \(lastName)"
    }

    var voicePart: Int
    var voicePartString: String? {
        chorus?.voicePartType.prettyName(forPart: voicePart)
    }

    @Attribute(.externalStorage) var pictureData: Data

    init(chorus: Chorus? = nil,
         firstName: String = "",
         lastName: String = "",
         voicePart: Int = 1,
         pictureData: Data = Data()) {
        self.chorus = chorus
        self.firstName = firstName
        self.lastName = lastName
        self.voicePart = voicePart
        self.pictureData = pictureData
    }

    init(member: Member) {
        self.chorus = member.chorus
        self.firstName = member.firstName
        self.lastName = member.lastName
        self.voicePart = member.voicePart
        self.pictureData = member.pictureData
    }

I tried building again on Xcode 15.4, and it still builds successfully there. Xcode 16.1 beta has not made a difference. Is this my fault, or is Xcode 16 broken?