diff --git a/Music/Models/SmartPlaylistCondition.swift b/Music/Models/SmartPlaylistCondition.swift
new file mode 100644
index 0000000..62b24f2
--- /dev/null
+++ b/Music/Models/SmartPlaylistCondition.swift
@@ -0,0 +1,152 @@
+import Foundation
+
+// Classifies a track field for operator and UI purposes.
+enum FieldType {
+    case string, int, double, date
+}
+
+// Represents a track column that can be filtered on.
+// Raw value matches the SQLite column name in the "tracks" table.
+enum TrackField: String, Codable, CaseIterable, Identifiable, Sendable {
+    case title, artist, albumArtist, album, genre, composer, fileFormat
+    case year, bpm, rating, playCount, trackNumber, discNumber, bitrate, sampleRate
+    case fileSize, duration
+    case dateAdded, dateModified, lastPlayedAt
+
+    var id: String { rawValue }
+
+    var displayName: String {
+        switch self {
+        case .title: return "Title"
+        case .artist: return "Artist"
+        case .albumArtist: return "Album Artist"
+        case .album: return "Album"
+        case .genre: return "Genre"
+        case .composer: return "Composer"
+        case .fileFormat: return "File Format"
+        case .year: return "Year"
+        case .bpm: return "BPM"
+        case .rating: return "Rating"
+        case .playCount: return "Play Count"
+        case .trackNumber: return "Track Number"
+        case .discNumber: return "Disc Number"
+        case .bitrate: return "Bitrate"
+        case .sampleRate: return "Sample Rate"
+        case .fileSize: return "File Size"
+        case .duration: return "Duration"
+        case .dateAdded: return "Date Added"
+        case .dateModified: return "Date Modified"
+        case .lastPlayedAt: return "Last Played"
+        }
+    }
+
+    var fieldType: FieldType {
+        switch self {
+        case .title, .artist, .albumArtist, .album, .genre, .composer, .fileFormat:
+            return .string
+        case .year, .bpm, .rating, .playCount, .trackNumber, .discNumber, .bitrate, .sampleRate, .fileSize:
+            return .int
+        case .duration:
+            return .double
+        case .dateAdded, .dateModified, .lastPlayedAt:
+            return .date
+        }
+    }
+
+    var validOperators: [ConditionOperator] {
+        switch fieldType {
+        case .string: return [.equals, .startsWith]
+        case .int, .double, .date: return [.equals, .greaterThan, .lessThan]
+        }
+    }
+
+    var defaultValue: ConditionValue {
+        switch fieldType {
+        case .string: return .string("")
+        case .int: return .int(0)
+        case .double: return .double(0)
+        case .date: return .date(Date())
+        }
+    }
+}
+
+enum ConditionOperator: String, Codable, Identifiable, Sendable {
+    case equals
+    case startsWith
+    case greaterThan
+    case lessThan
+
+    var id: String { rawValue }
+
+    var displayName: String {
+        switch self {
+        case .equals: return "is"
+        case .startsWith: return "starts with"
+        case .greaterThan: return "is greater than"
+        case .lessThan: return "is less than"
+        }
+    }
+}
+
+// Tagged union storing the actual filter value with its type.
+// Uses custom Codable to survive JSON round-trips cleanly.
+enum ConditionValue: Equatable, Sendable {
+    case string(String)
+    case int(Int)
+    case double(Double)
+    case date(Date)
+
+    var isEmpty: Bool {
+        if case .string(let s) = self {
+            return s.trimmingCharacters(in: .whitespaces).isEmpty
+        }
+        return false
+    }
+}
+
+extension ConditionValue: Codable {
+    private enum CodingKeys: String, CodingKey { case type, value }
+
+    func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        switch self {
+        case .string(let s):
+            try container.encode("string", forKey: .type)
+            try container.encode(s, forKey: .value)
+        case .int(let i):
+            try container.encode("int", forKey: .type)
+            try container.encode(i, forKey: .value)
+        case .double(let d):
+            try container.encode("double", forKey: .type)
+            try container.encode(d, forKey: .value)
+        case .date(let date):
+            try container.encode("date", forKey: .type)
+            try container.encode(date.timeIntervalSince1970, forKey: .value)
+        }
+    }
+
+    init(from decoder: Decoder) throws {
+        let container = try decoder.container(keyedBy: CodingKeys.self)
+        let type = try container.decode(String.self, forKey: .type)
+        switch type {
+        case "string":
+            self = .string(try container.decode(String.self, forKey: .value))
+        case "int":
+            self = .int(try container.decode(Int.self, forKey: .value))
+        case "double":
+            self = .double(try container.decode(Double.self, forKey: .value))
+        case "date":
+            self = .date(Date(timeIntervalSince1970: try container.decode(Double.self, forKey: .value)))
+        default:
+            throw DecodingError.dataCorruptedError(forKey: .type, in: container, debugDescription: "Unknown type: \(type)")
+        }
+    }
+}
+
+nonisolated struct SmartPlaylistCondition: Codable, Equatable, Sendable {
+    var field: TrackField
+    var op: ConditionOperator
+    var value: ConditionValue
+
+    var isEmpty: Bool { value.isEmpty }
+}
diff --git a/MusicTests/SmartPlaylistTests.swift b/MusicTests/SmartPlaylistTests.swift
index b099238..f89f135 100644
--- a/MusicTests/SmartPlaylistTests.swift
+++ b/MusicTests/SmartPlaylistTests.swift
@@ -76,4 +76,39 @@ struct SmartPlaylistTests {
         #expect(results[0].title == "Bitches Brew")
         #expect(results[1].title == "Kind of Blue")
     }
+
+    // Encodes and decodes a SmartPlaylistCondition to/from JSON,
+    // verifying that all fields survive the round-trip.
+    @Test func conditionCodableRoundTrip() throws {
+        let condition = SmartPlaylistCondition(
+            field: .artist,
+            op: .equals,
+            value: .string("Miles Davis")
+        )
+        let data = try JSONEncoder().encode(condition)
+        let decoded = try JSONDecoder().decode(SmartPlaylistCondition.self, from: data)
+        #expect(decoded.field == .artist)
+        #expect(decoded.op == .equals)
+        if case .string(let s) = decoded.value {
+            #expect(s == "Miles Davis")
+        } else {
+            Issue.record("Expected string value")
+        }
+    }
+
+    // Encodes and decodes an array of conditions with mixed value types.
+    @Test func conditionsArrayCodableRoundTrip() throws {
+        let conditions: [SmartPlaylistCondition] = [
+            SmartPlaylistCondition(field: .artist, op: .startsWith, value: .string("Miles")),
+            SmartPlaylistCondition(field: .year, op: .greaterThan, value: .int(1960)),
+            SmartPlaylistCondition(field: .dateAdded, op: .lessThan, value: .date(Date(timeIntervalSince1970: 0)))
+        ]
+        let data = try JSONEncoder().encode(conditions)
+        let decoded = try JSONDecoder().decode([SmartPlaylistCondition].self, from: data)
+        #expect(decoded.count == 3)
+        #expect(decoded[0].field == .artist)
+        #expect(decoded[1].op == .greaterThan)
+        if case .int(let y) = decoded[1].value { #expect(y == 1960) } else { Issue.record("Expected int") }
+        if case .date(let d) = decoded[2].value { #expect(d == Date(timeIntervalSince1970: 0)) } else { Issue.record("Expected date") }
+    }
 }