diff --git a/Sources/App/AppDaemon.swift b/Sources/App/AppDaemon.swift
index 708386f..425d370 100644
--- a/Sources/App/AppDaemon.swift
+++ b/Sources/App/AppDaemon.swift
@@ -41,6 +41,7 @@ final class AppDaemon: ObservableObject {
         pruneTimer = Timer.scheduledTimer(withTimeInterval: 10, repeats: true) { _ in
             Task { @MainActor [weak self] in self?.prune() }
         }
+        ReactiveEngine.shared.start()
     }
 
     /// Clears the tracked sessions (e.g. after disconnecting an integration).
diff --git a/Sources/App/BubbleSettings.swift b/Sources/App/BubbleSettings.swift
index c403293..cf0994b 100644
--- a/Sources/App/BubbleSettings.swift
+++ b/Sources/App/BubbleSettings.swift
@@ -319,6 +319,9 @@ final class BubbleSettings: ObservableObject {
             ActivityFormatter.currentTheme = activityTheme
         }
     }
+    @Published var reactiveBubblesEnabled: Bool {
+        didSet { ud.set(reactiveBubblesEnabled, forKey: Keys.reactiveBubblesEnabled) }
+    }
 
     // MARK: Computed
 
@@ -357,6 +360,7 @@ final class BubbleSettings: ObservableObject {
         static let hiddenKinds         = "agentpet.bubble.hiddenKinds"
         static let iconChoices     = "agentpet.bubble.iconChoices"
         static let activityTheme   = "agentpet.bubble.activityTheme"
+        static let reactiveBubblesEnabled = "agentpet.bubble.reactiveBubblesEnabled"
     }
 
     init() {
@@ -372,6 +376,7 @@ final class BubbleSettings: ObservableObject {
         groupByKind     = ud.bool(forKey: Keys.groupByKind)
         displayMode = BubbleDisplayMode(rawValue: ud.string(forKey: Keys.displayMode) ?? "") ?? .carousel
         multiAgentBubbleEnabled = ud.object(forKey: Keys.multiAgentBubbleEnabled) as? Bool ?? true
+        reactiveBubblesEnabled = ud.object(forKey: Keys.reactiveBubblesEnabled) as? Bool ?? true
         hiddenKinds        = Set((Self.loadJSON(Keys.hiddenKinds) as [String]? ?? []).compactMap(AgentKind.init(rawValue:)))
         iconChoices    = Self.loadJSON(Keys.iconChoices) ?? [:]
         activityTheme  = ActivityTheme(rawValue: ud.string(forKey: Keys.activityTheme) ?? "") ?? .chef
diff --git a/Sources/App/BubbleSettingsView.swift b/Sources/App/BubbleSettingsView.swift
index ad807ac..517a815 100644
--- a/Sources/App/BubbleSettingsView.swift
+++ b/Sources/App/BubbleSettingsView.swift
@@ -47,6 +47,15 @@ struct BubbleSettingsView: View {
                 Spacer()
                 ColorSwitch(isOn: $settings.multiAgentBubbleEnabled)
             }
+            HStack {
+                VStack(alignment: .leading, spacing: 2) {
+                    Text("Pet reactive bubbles")
+                    Text("Pet reacts to rate limits, token usage, hunger, and streaks.")
+                        .font(.caption).foregroundStyle(.secondary)
+                }
+                Spacer()
+                ColorSwitch(isOn: $settings.reactiveBubblesEnabled)
+            }
         } header: {
             Text("Bubble mode")
         }
diff --git a/Sources/App/PetController.swift b/Sources/App/PetController.swift
index 4ecd206..62a312d 100644
--- a/Sources/App/PetController.swift
+++ b/Sources/App/PetController.swift
@@ -170,6 +170,12 @@ final class PetController: ObservableObject {
         }
     }
 
+    func flashReactiveLine(_ line: String) {
+        guard showChat else { return }
+        chatLine = line
+        StatusBarController.shared.refreshTitle()
+    }
+
     private func setMood(_ newMood: PetMood) {
         let changed = newMood != mood
         mood = newMood
diff --git a/Sources/App/ReactiveEngine.swift b/Sources/App/ReactiveEngine.swift
new file mode 100644
index 0000000..f4fb451
--- /dev/null
+++ b/Sources/App/ReactiveEngine.swift
@@ -0,0 +1,267 @@
+import Foundation
+import Combine
+import AgentPetCore
+
+// Re-export so test target (import agentpet) can use PetHunger without importing AgentPetCore directly
+public typealias PetHunger = AgentPetCore.PetHunger
+
+// MARK: - ReactiveMetric
+
+public enum ReactiveMetric: Hashable {
+    case rateLimit
+    case dailyTokens
+    case sessionCount
+    case hunger
+    case streak
+    case dailyMeals
+}
+
+// MARK: - Thresholds
+
+private enum Thresholds {
+    enum RateLimit {
+        static let silent: Double = 0.5
+        static let low: Double = 0.15
+        static let high: Double = 0.05
+    }
+    enum DailyTokens {
+        static let silent: Int = 1_000_000
+        static let low: Int = 3_000_000
+        static let mid: Int = 6_000_000
+    }
+    enum SessionCount {
+        static let silent: Int = 5
+        static let low: Int = 8
+    }
+    enum Streak {
+        static let silent: Int = 4
+        static let low: Int = 7
+        static let mid: Int = 14
+    }
+    enum DailyMeals {
+        static let silent: Int = 20
+        static let low: Int = 50
+        static let mid: Int = 100
+    }
+    enum Cooldown {
+        static let sameMetric: TimeInterval = 600
+        static let crossMetric: TimeInterval = 30
+    }
+    enum Hunger {
+        static let dailyLimit: Int = 2
+    }
+}
+
+// MARK: - Phrase Pools
+
+private enum Phrases {
+    static let rateLimitLow = ["用量開始升喇～", "慢慢嚟，唔急", "留意下 quota"]
+    static let rateLimitHigh = ["Rate limit 快見底...", "要慳住用喇！", "Quota 唔多喇"]
+    static let rateLimitCritical = ["差唔多冇 quota 喇 😰", "停一停吖...", "Quota 幾乎用完"]
+
+    static let dailyTokensLow = ["今日燒咗唔少 token～", "食咗好多 token 喇", "Token 消耗上升中"]
+    static let dailyTokensMid = ["大胃王模式！", "今日胃口好好～", "Token 食得好快"]
+    static let dailyTokensHigh = ["今日 token 用量爆炸 🔥", "Token 消耗超高！", "今日 burn 好勁"]
+
+    static let sessionCountLow = ["5 個 agent 齊開～", "好多 agent 喺度做嘢", "並行度唔低"]
+    static let sessionCountHigh = ["指揮中心模式 😳", "咁多 session！", "全力運作中"]
+
+    static let hungerLow = ["有少少肚餓...", "嗯...想食嘢", "肚子打鼓"]
+    static let hungerMid = ["好耐冇餵我喇 😢", "肚餓...", "想食嘢..."]
+    static let hungerHigh = ["你去咗邊... 😭", "快要餓暈喇", "好肚餓啊"]
+
+    static let streakLow = ["連續幾日！繼續加油", "連續好幾日～", "堅持緊"]
+    static let streakMid = ["成個禮拜冇斷過！", "好有毅力～", "太穩定喇"]
+    static let streakHigh = ["傳說級連續！", "太強喇！", "無人能擋"]
+
+    static let dailyMealsLow = ["今日完成好多 session～", "效率唔錯", "做咗唔少嘢"]
+    static let dailyMealsMid = ["半百 session！效率怪物", "50+！", "超高產"]
+    static let dailyMealsHigh = ["破百！你今日唔駛瞓？", "100+ session！", "超人嚟嘅"]
+}
+
+// MARK: - CooldownTracker
+
+private struct CooldownTracker {
+    private var lastFiredAt: [ReactiveMetric: Date] = [:]
+    private var lastAnyFiredAt: Date? = nil
+    private var hungerDayKey: String = ""
+    private var hungerDayCount: Int = 0
+
+    private static let utcCalendar: Calendar = {
+        var cal = Calendar(identifier: .gregorian)
+        cal.timeZone = TimeZone(identifier: "UTC")!
+        return cal
+    }()
+
+    private func dayKey(for date: Date) -> String {
+        let c = Self.utcCalendar.dateComponents([.year, .month, .day], from: date)
+        return String(format: "%04d-%02d-%02d", c.year ?? 0, c.month ?? 0, c.day ?? 0)
+    }
+
+    /// Returns true if allowed to fire. Mutates state if allowed.
+    mutating func check(metric: ReactiveMetric, now: Date) -> Bool {
+        // Same-metric gate takes priority
+        if let last = lastFiredAt[metric] {
+            if now.timeIntervalSince(last) < Thresholds.Cooldown.sameMetric {
+                return false
+            }
+        }
+
+        // Cross-metric gate: only applies when a *different* metric fired most recently
+        let lastAnyIsOtherMetric = lastAnyFiredAt != nil && lastAnyFiredAt != lastFiredAt[metric]
+        if lastAnyIsOtherMetric,
+           let lastAny = lastAnyFiredAt,
+           now.timeIntervalSince(lastAny) < Thresholds.Cooldown.crossMetric {
+            return false
+        }
+
+        // Hunger daily limit
+        if metric == .hunger {
+            let today = dayKey(for: now)
+            if hungerDayKey != today {
+                hungerDayKey = today
+                hungerDayCount = 0
+            }
+            if hungerDayCount >= Thresholds.Hunger.dailyLimit { return false }
+            hungerDayCount += 1
+        }
+
+        lastFiredAt[metric] = now
+        lastAnyFiredAt = now
+        return true
+    }
+}
+
+// MARK: - ReactiveEngine
+
+@MainActor
+public final class ReactiveEngine {
+
+    public static let shared = ReactiveEngine()
+
+    private var cooldown = CooldownTracker()
+    private var cancellables = Set<AnyCancellable>()
+
+    public init() {}
+
+    @discardableResult
+    public func evaluate(metric: ReactiveMetric, value: AnyHashable?, now: Date = .now) -> String? {
+        guard let phrases = phrasePool(metric: metric, value: value) else { return nil }
+        guard BubbleSettings.shared.reactiveBubblesEnabled else { return nil }
+        guard cooldown.check(metric: metric, now: now) else { return nil }
+        return phrases.randomElement()
+    }
+
+    // MARK: - Subscriptions
+
+    public func start() {
+        // Sink 1: OpenUsageClient
+        OpenUsageClient.shared.$providers
+            .receive(on: RunLoop.main)
+            .sink { [weak self] _ in
+                let value = OpenUsageClient.shared.lowestFractionLeft
+                if let line = self?.evaluate(metric: .rateLimit, value: value.map { AnyHashable($0) }) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+            }
+            .store(in: &cancellables)
+
+        // Sink 2: PetCareController (evaluates 4 metrics)
+        PetCareController.shared.$states
+            .receive(on: RunLoop.main)
+            .sink { [weak self] _ in
+                guard let self else { return }
+                let care = PetCareController.shared
+                let current = care.current
+
+                // dailyTokens — use days[todayKey] for real value
+                let todayKey = Self.todayKey()
+                let realTokens = current.days?[todayKey] ?? 0
+                if let line = self.evaluate(metric: .dailyTokens, value: AnyHashable(realTokens)) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+
+                // streak
+                if let line = self.evaluate(metric: .streak, value: AnyHashable(current.streakDays)) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+
+                // dailyMeals
+                if let line = self.evaluate(metric: .dailyMeals, value: AnyHashable(current.mealsToday)) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+
+                // hunger
+                let hunger = care.hunger
+                if let line = self.evaluate(metric: .hunger, value: AnyHashable(hunger)) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+            }
+            .store(in: &cancellables)
+
+        // Sink 3: AppDaemon sessions
+        AppDaemon.shared.$sessions
+            .receive(on: RunLoop.main)
+            .sink { [weak self] sessions in
+                if let line = self?.evaluate(metric: .sessionCount, value: AnyHashable(sessions.count)) {
+                    PetController.shared.flashReactiveLine(line)
+                }
+            }
+            .store(in: &cancellables)
+    }
+
+    private static func todayKey() -> String {
+        let c = Calendar.current.dateComponents([.year, .month, .day], from: Date())
+        return String(format: "%04d-%02d-%02d", c.year ?? 0, c.month ?? 0, c.day ?? 0)
+    }
+
+    // MARK: - Tier resolution
+
+    private func phrasePool(metric: ReactiveMetric, value: AnyHashable?) -> [String]? {
+        switch metric {
+        case .rateLimit:
+            guard let v = value.flatMap({ $0.base as? Double }) else { return nil }
+            if v > Thresholds.RateLimit.silent { return nil }
+            if v > Thresholds.RateLimit.low { return Phrases.rateLimitLow }
+            if v > Thresholds.RateLimit.high { return Phrases.rateLimitHigh }
+            return Phrases.rateLimitCritical
+
+        case .dailyTokens:
+            guard let v = value.flatMap({ $0.base as? Int }) else { return nil }
+            if v < Thresholds.DailyTokens.silent { return nil }
+            if v < Thresholds.DailyTokens.low { return Phrases.dailyTokensLow }
+            if v < Thresholds.DailyTokens.mid { return Phrases.dailyTokensMid }
+            return Phrases.dailyTokensHigh
+
+        case .sessionCount:
+            guard let v = value.flatMap({ $0.base as? Int }) else { return nil }
+            if v < Thresholds.SessionCount.silent { return nil }
+            if v < Thresholds.SessionCount.low { return Phrases.sessionCountLow }
+            return Phrases.sessionCountHigh
+
+        case .hunger:
+            guard let h = value.flatMap({ $0.base as? PetHunger }) else { return nil }
+            switch h {
+            case .full, .satisfied: return nil
+            case .peckish: return Phrases.hungerLow
+            case .hungry: return Phrases.hungerMid
+            case .starving: return Phrases.hungerHigh
+            }
+
+        case .streak:
+            guard let v = value.flatMap({ $0.base as? Int }) else { return nil }
+            if v < Thresholds.Streak.silent { return nil }
+            if v < Thresholds.Streak.low { return Phrases.streakLow }
+            if v < Thresholds.Streak.mid { return Phrases.streakMid }
+            return Phrases.streakHigh
+
+        case .dailyMeals:
+            guard let v = value.flatMap({ $0.base as? Int }) else { return nil }
+            if v < Thresholds.DailyMeals.silent { return nil }
+            if v < Thresholds.DailyMeals.low { return Phrases.dailyMealsLow }
+            if v < Thresholds.DailyMeals.mid { return Phrases.dailyMealsMid }
+            return Phrases.dailyMealsHigh
+        }
+    }
+}
+
diff --git a/Tests/AgentPetAppTests/ReactiveEngineTests.swift b/Tests/AgentPetAppTests/ReactiveEngineTests.swift
new file mode 100644
index 0000000..acd15c5
--- /dev/null
+++ b/Tests/AgentPetAppTests/ReactiveEngineTests.swift
@@ -0,0 +1,282 @@
+import XCTest
+@testable import agentpet
+
+@MainActor
+final class ReactiveEngineTests: XCTestCase {
+
+    private func makeEngine() -> ReactiveEngine {
+        ReactiveEngine()
+    }
+
+    func testRateLimitAbove50PercentIsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: 0.6)
+        XCTAssertNil(result)
+    }
+
+    func testRateLimitBetween15And50PercentIsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: 0.30)
+        XCTAssertNotNil(result)
+    }
+
+    func testRateLimitBetween5And15PercentIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: 0.10)
+        XCTAssertNotNil(result)
+    }
+
+    func testRateLimitBelow5PercentIsCritical() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: 0.03)
+        XCTAssertNotNil(result)
+    }
+
+    func testRateLimitNilValueReturnsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: nil as Double?)
+        XCTAssertNil(result)
+    }
+
+    func testDailyTokensBelow1MIsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyTokens, value: 800_000)
+        XCTAssertNil(result)
+    }
+
+    func testDailyTokensBetween1MAnd3MIsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyTokens, value: 2_000_000)
+        XCTAssertNotNil(result)
+    }
+
+    func testDailyTokensBetween3MAnd6MIsMid() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyTokens, value: 4_500_000)
+        XCTAssertNotNil(result)
+    }
+
+    func testDailyTokensAbove6MIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyTokens, value: 7_000_000)
+        XCTAssertNotNil(result)
+    }
+
+    func testSessionCount1To4IsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .sessionCount, value: 3)
+        XCTAssertNil(result)
+    }
+
+    func testSessionCount5To7IsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .sessionCount, value: 6)
+        XCTAssertNotNil(result)
+    }
+
+    func testSessionCount8OrMoreIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .sessionCount, value: 8)
+        XCTAssertNotNil(result)
+    }
+
+    func testHungerFullIsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .hunger, value: PetHunger.full)
+        XCTAssertNil(result)
+    }
+
+    func testHungerSatisfiedIsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .hunger, value: PetHunger.satisfied)
+        XCTAssertNil(result)
+    }
+
+    func testHungerPeckishIsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .hunger, value: PetHunger.peckish)
+        XCTAssertNotNil(result)
+    }
+
+    func testHungerHungryIsMid() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .hunger, value: PetHunger.hungry)
+        XCTAssertNotNil(result)
+    }
+
+    func testHungerStarvingIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .hunger, value: PetHunger.starving)
+        XCTAssertNotNil(result)
+    }
+
+    func testStreak1To3IsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .streak, value: 2)
+        XCTAssertNil(result)
+    }
+
+    func testStreak4To6IsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .streak, value: 5)
+        XCTAssertNotNil(result)
+    }
+
+    func testStreak7To13IsMid() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .streak, value: 10)
+        XCTAssertNotNil(result)
+    }
+
+    func testStreak14OrMoreIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .streak, value: 14)
+        XCTAssertNotNil(result)
+    }
+
+    func testDailyMealsBelow20IsSilent() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyMeals, value: 10)
+        XCTAssertNil(result)
+    }
+
+    func testDailyMeals20To50IsLow() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyMeals, value: 35)
+        XCTAssertNotNil(result)
+    }
+
+    func testDailyMeals50To100IsMid() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyMeals, value: 75)
+        XCTAssertNotNil(result)
+    }
+
+    func testDailyMeals100OrMoreIsHigh() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .dailyMeals, value: 100)
+        XCTAssertNotNil(result)
+    }
+
+    func testSameMetricBlockedWithin600Seconds() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        let first = engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: now)
+        XCTAssertNotNil(first)
+        let secondNow = now.addingTimeInterval(599)
+        let second = engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: secondNow)
+        XCTAssertNil(second)
+    }
+
+    func testSameMetricAllowedAfter600Seconds() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: now)
+        let laterNow = now.addingTimeInterval(600)
+        let result = engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: laterNow)
+        XCTAssertNotNil(result)
+    }
+
+    func testCrossMetricBlockedWithin30Seconds() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: now)
+        let laterNow = now.addingTimeInterval(29)
+        let result = engine.evaluate(metric: .sessionCount, value: 6, now: laterNow)
+        XCTAssertNil(result)
+    }
+
+    func testCrossMetricAllowedAfter30Seconds() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: now)
+        let laterNow = now.addingTimeInterval(30)
+        let result = engine.evaluate(metric: .sessionCount, value: 6, now: laterNow)
+        XCTAssertNotNil(result)
+    }
+
+    func testSameMetricGateTakesPriorityOverCrossMetricGate() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: now)
+        let laterNow = now.addingTimeInterval(35)
+        let result = engine.evaluate(metric: .dailyTokens, value: 2_000_000, now: laterNow)
+        XCTAssertNil(result)
+    }
+
+    func testHungerDailyLimitBlocksThirdTriggerSameDay() {
+        let engine = makeEngine()
+        let base = Date(timeIntervalSince1970: 1_750_000_000)
+        let t1 = engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: base)
+        XCTAssertNotNil(t1)
+        let t2 = engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: base.addingTimeInterval(600))
+        XCTAssertNotNil(t2)
+        let t3 = engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: base.addingTimeInterval(1200))
+        XCTAssertNil(t3)
+    }
+
+    func testHungerDailyLimitResetsNextDay() {
+        let engine = makeEngine()
+        let formatter = DateFormatter()
+        formatter.dateFormat = "yyyy-MM-dd HH:mm"
+        formatter.timeZone = TimeZone(identifier: "UTC")
+        let day1 = formatter.date(from: "2026-06-17 10:00")!
+        let day2 = formatter.date(from: "2026-06-18 10:00")!
+        engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: day1)
+        engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: day1.addingTimeInterval(600))
+        let blocked = engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: day1.addingTimeInterval(1200))
+        XCTAssertNil(blocked)
+        let tomorrow = engine.evaluate(metric: .hunger, value: PetHunger.hungry, now: day2)
+        XCTAssertNotNil(tomorrow)
+    }
+
+    func testSilentTierReturnsNil() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: 0.9)
+        XCTAssertNil(result)
+    }
+
+    func testNonSilentTierReturnsNonNilString() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .streak, value: 14)
+        XCTAssertNotNil(result)
+        XCTAssertFalse(result?.isEmpty ?? true)
+    }
+
+    func testNilValueReturnsNil() {
+        let engine = makeEngine()
+        let result = engine.evaluate(metric: .rateLimit, value: nil as Double?)
+        XCTAssertNil(result)
+    }
+
+    func testCooldownBlockReturnsNil() {
+        let engine = makeEngine()
+        let now = Date(timeIntervalSince1970: 1_000_000)
+        let first = engine.evaluate(metric: .streak, value: 14, now: now)
+        XCTAssertNotNil(first)
+        let second = engine.evaluate(metric: .streak, value: 14, now: now.addingTimeInterval(1))
+        XCTAssertNil(second)
+    }
+}
+
+private extension ReactiveEngine {
+    @discardableResult
+    func evaluate(metric: ReactiveMetric, value: Double?, now: Date = .now) -> String? {
+        evaluate(metric: metric, value: value.map { AnyHashable($0) }, now: now)
+    }
+
+    @discardableResult
+    func evaluate(metric: ReactiveMetric, value: Double, now: Date = .now) -> String? {
+        evaluate(metric: metric, value: AnyHashable(value), now: now)
+    }
+
+    @discardableResult
+    func evaluate(metric: ReactiveMetric, value: Int, now: Date = .now) -> String? {
+        evaluate(metric: metric, value: AnyHashable(value), now: now)
+    }
+
+    @discardableResult
+    func evaluate(metric: ReactiveMetric, value: PetHunger, now: Date = .now) -> String? {
+        evaluate(metric: metric, value: AnyHashable(value), now: now)
+    }
+}