diff --git a/Sources/AgentPetCore/PetCare.swift b/Sources/AgentPetCore/PetCare.swift
index 29c31bf..3ae3f7f 100644
--- a/Sources/AgentPetCore/PetCare.swift
+++ b/Sources/AgentPetCore/PetCare.swift
@@ -1,5 +1,23 @@
 import Foundation
 
+/// Achievements the pet can unlock over its lifetime.
+public enum Achievement: String, Codable, CaseIterable, Sendable {
+    case firstMeal
+    case sessions100
+    case sessions500
+    case tokens1M
+    case tokens10M
+    case tokens50M
+    case level5
+    case level10
+    case level20
+    case level35
+    case streak7
+    case streak14
+    case streak30
+    case nightOwl
+}
+
 /// How hungry the pet is, derived from the time since its last feeding.
 public enum PetHunger: String, Codable, CaseIterable, Sendable {
     case full
@@ -36,6 +54,7 @@ public struct PetCareState: Codable, Equatable, Sendable {
     /// to draw the weekly trend. Optional so states saved before this field
     /// existed still decode.
     public var days: [String: Int]?
+    public var unlockedAchievements: Set<Achievement>?
 
     public init() {
         xp = 0
@@ -228,6 +247,65 @@ public enum PetCare {
         return String(format: "%04d-%02d-%02d", c.year ?? 0, c.month ?? 0, c.day ?? 0)
     }
 
+    // MARK: - Achievements
+
+    public static func checkAchievements(state: PetCareState, hour: Int) -> Set<Achievement> {
+        let dl = displayLevel(forXP: state.xp)
+
+        let mealThresholds: [(Int, Achievement)] = [
+            (1, .firstMeal), (100, .sessions100), (500, .sessions500),
+        ]
+        let tokenThresholds: [(Int, Achievement)] = [
+            (1_000_000, .tokens1M), (10_000_000, .tokens10M), (50_000_000, .tokens50M),
+        ]
+        let levelThresholds: [(Int, Achievement)] = [
+            (5, .level5), (10, .level10), (20, .level20), (35, .level35),
+        ]
+        let streakThresholds: [(Int, Achievement)] = [
+            (7, .streak7), (14, .streak14), (30, .streak30),
+        ]
+
+        var result = Set<Achievement>()
+        for (threshold, badge) in mealThresholds   where state.totalMeals  >= threshold { result.insert(badge) }
+        for (threshold, badge) in tokenThresholds  where state.totalTokens >= threshold { result.insert(badge) }
+        for (threshold, badge) in levelThresholds  where dl                >= threshold { result.insert(badge) }
+        for (threshold, badge) in streakThresholds where state.streakDays  >= threshold { result.insert(badge) }
+        if hour < 6, state.totalMeals >= 1 { result.insert(.nightOwl) }
+        return result
+    }
+
+    @discardableResult
+    public static func unlockNewAchievements(
+        state: inout PetCareState, now: Date, calendar: Calendar = .current
+    ) -> Set<Achievement> {
+        let hour = calendar.component(.hour, from: now)
+        let qualified = checkAchievements(state: state, hour: hour)
+        let already = state.unlockedAchievements ?? []
+        let newly = qualified.subtracting(already)
+        state.unlockedAchievements = already.union(newly)
+        return newly
+    }
+
+    /// Human-readable display name for an achievement, localised.
+    public static func achievementDisplayName(_ a: Achievement) -> String {
+        switch a {
+        case .firstMeal:   return NSLocalizedString("First Meal", comment: "achievement name")
+        case .sessions100: return NSLocalizedString("100 Sessions", comment: "achievement name")
+        case .sessions500: return NSLocalizedString("500 Sessions", comment: "achievement name")
+        case .tokens1M:    return NSLocalizedString("1M Tokens", comment: "achievement name")
+        case .tokens10M:   return NSLocalizedString("10M Tokens", comment: "achievement name")
+        case .tokens50M:   return NSLocalizedString("50M Tokens", comment: "achievement name")
+        case .level5:      return NSLocalizedString("Level 5", comment: "achievement name")
+        case .level10:     return NSLocalizedString("Level 10", comment: "achievement name")
+        case .level20:     return NSLocalizedString("Level 20", comment: "achievement name")
+        case .level35:     return NSLocalizedString("Level 35", comment: "achievement name")
+        case .streak7:     return NSLocalizedString("7-Day Streak", comment: "achievement name")
+        case .streak14:    return NSLocalizedString("14-Day Streak", comment: "achievement name")
+        case .streak30:    return NSLocalizedString("30-Day Streak", comment: "achievement name")
+        case .nightOwl:    return NSLocalizedString("Night Owl", comment: "achievement name")
+        }
+    }
+
     private static func markFed(_ state: inout PetCareState, now: Date, calendar: Calendar) {
         state.lastFedAt = now
         let today = dayKey(for: now, calendar: calendar)
diff --git a/Sources/App/CareTabView.swift b/Sources/App/CareTabView.swift
index bc248a4..10bde80 100644
--- a/Sources/App/CareTabView.swift
+++ b/Sources/App/CareTabView.swift
@@ -107,6 +107,22 @@ struct CareTabView: View {
                 LabeledContent("Total sessions", value: "\(care.current.totalMeals)")
             }
 
+            Section {
+                let unlocked = care.achievements
+                if unlocked.isEmpty {
+                    Text("No achievements unlocked yet.")
+                        .foregroundStyle(.secondary)
+                } else {
+                    ForEach(Array(unlocked).sorted(by: { $0.rawValue < $1.rawValue }), id: \.self) { a in
+                        Text(PetCare.achievementDisplayName(a))
+                    }
+                }
+            } header: {
+                Text("Achievements")
+            } footer: {
+                Text(verbatim: "\(care.achievements.count) of \(Achievement.allCases.count) unlocked")
+            }
+
             if care.raisedPetIDs.count > 1 {
                 Section("All companions") {
                     ForEach(care.raisedPetIDs, id: \.self) { id in
diff --git a/Sources/App/PetCareController.swift b/Sources/App/PetCareController.swift
index 0ab0756..ff483b3 100644
--- a/Sources/App/PetCareController.swift
+++ b/Sources/App/PetCareController.swift
@@ -82,8 +82,10 @@ final class PetCareController: ObservableObject {
 
     private func mutateCurrent(_ change: (inout PetCareState) -> Void) {
         guard let petID = currentPetID else { return }
-        let levelBefore = PetCare.level(forXP: state(for: petID).xp)
-        var s = state(for: petID)
+        let stateBefore = state(for: petID)
+        let levelBefore = PetCare.level(forXP: stateBefore.xp)
+        let achievementsBefore = stateBefore.unlockedAchievements ?? []
+        var s = stateBefore
         change(&s)
         guard s != states[petID] else { return }
         states[petID] = s
@@ -97,8 +99,21 @@ final class PetCareController: ObservableObject {
             )
             PetController.shared.flashCelebrate(line: line)
         }
+        let achievementsAfter = s.unlockedAchievements ?? []
+        let newAchievements = achievementsAfter.subtracting(achievementsBefore)
+        for achievement in newAchievements {
+            let name = PetCare.achievementDisplayName(achievement)
+            let line = String(
+                format: NSLocalizedString("Achievement unlocked: %@ 🏆", comment: "achievement unlock celebrate line"),
+                name
+            )
+            PetController.shared.flashCelebrate(line: line)
+        }
     }
 
+    /// All achievements unlocked by the currently selected pet.
+    var achievements: Set<Achievement> { current.unlockedAchievements ?? [] }
+
     private func persist() {
         if let data = try? JSONEncoder().encode(states) {
             UserDefaults.standard.set(data, forKey: Self.storageKey)
diff --git a/Sources/App/PetStatsView.swift b/Sources/App/PetStatsView.swift
index 6fa725c..26c09ce 100644
--- a/Sources/App/PetStatsView.swift
+++ b/Sources/App/PetStatsView.swift
@@ -25,6 +25,7 @@ struct PetStatsView: View {
         VStack(alignment: .leading, spacing: 12) {
             header(state)
             xpBlock(state)
+            achievementBlock
             statGrid(state)
             trendBlock(state)
             usageBlock
@@ -147,6 +148,51 @@ struct PetStatsView: View {
         }
     }
 
+    // MARK: - Achievements
+
+    private static let achievementSymbols: [Achievement: String] = [
+        .firstMeal:   "fork.knife",
+        .sessions100: "trophy",
+        .sessions500: "trophy.fill",
+        .tokens1M:    "flame",
+        .tokens10M:   "flame.fill",
+        .tokens50M:   "bolt.fill",
+        .level5:      "star",
+        .level10:     "star.fill",
+        .level20:     "shield.fill",
+        .level35:     "crown.fill",
+        .streak7:     "calendar",
+        .streak14:    "calendar.badge.clock",
+        .streak30:    "calendar.badge.checkmark",
+        .nightOwl:    "moon.fill",
+    ]
+
+    private var achievementBlock: some View {
+        let unlocked = care.achievements
+        let total = Achievement.allCases.count
+        return VStack(alignment: .leading, spacing: 5) {
+            HStack {
+                Text("Achievements")
+                    .font(.system(size: 9, weight: .semibold)).tracking(0.8)
+                    .foregroundStyle(.white.opacity(0.35))
+                Spacer()
+                Text(verbatim: "\(unlocked.count) / \(total)")
+                    .font(.system(size: 9, weight: .semibold)).foregroundStyle(.white.opacity(0.55))
+            }
+            HStack(spacing: 4) {
+                ForEach(Achievement.allCases, id: \.self) { a in
+                    let symbol = Self.achievementSymbols[a] ?? "star"
+                    let isUnlocked = unlocked.contains(a)
+                    Image(systemName: symbol)
+                        .font(.system(size: 11))
+                        .foregroundStyle(isUnlocked ? stageColor : Color.white.opacity(0.15))
+                        .frame(width: 20, height: 20)
+                        .help(PetCare.achievementDisplayName(a))
+                }
+            }
+        }
+    }
+
     // MARK: - Stat grid
 
     private func statGrid(_ state: PetCareState) -> some View {
diff --git a/Tests/AgentPetCoreTests/AchievementTests.swift b/Tests/AgentPetCoreTests/AchievementTests.swift
new file mode 100644
index 0000000..6bdda7c
--- /dev/null
+++ b/Tests/AgentPetCoreTests/AchievementTests.swift
@@ -0,0 +1,149 @@
+import XCTest
+@testable import AgentPetCore
+
+final class AchievementTests: XCTestCase {
+
+    // MARK: - Shared helpers (mirror PetCareTests pattern)
+
+    private let calendar: Calendar = {
+        var c = Calendar(identifier: .gregorian)
+        c.timeZone = TimeZone(identifier: "UTC")!
+        return c
+    }()
+
+    private func date(_ s: String) -> Date {
+        let f = DateFormatter()
+        f.dateFormat = "yyyy-MM-dd HH:mm"
+        f.timeZone = TimeZone(identifier: "UTC")
+        return f.date(from: s)!
+    }
+
+    // MARK: - 1. First meal
+
+    func testFirstMealUnlocksOnFirstFeeding() {
+        var state = PetCareState()
+        let now = date("2026-06-18 10:00")
+        PetCare.recordMeal(state: &state, now: now, calendar: calendar)
+
+        let newly = PetCare.unlockNewAchievements(state: &state, now: now, calendar: calendar)
+
+        XCTAssertTrue(newly.contains(.firstMeal),
+                      "first meal should unlock .firstMeal; got \(newly)")
+    }
+
+    // MARK: - 2. Level milestones
+
+    func testLevelMilestones() {
+        var state = PetCareState()
+        let now = date("2026-06-18 10:00")
+        // XP to reach internal level 6 (display level 5) = xpToReach(6) = 60*6*5 = 1800
+        // Feed enough meals to exceed that XP threshold.
+        let targetXP = PetCare.xpToReach(level: 6)   // 1800
+        let mealsNeeded = Int(ceil(Double(targetXP) / Double(PetCare.mealXP)))
+        for _ in 0..<mealsNeeded {
+            PetCare.recordMeal(state: &state, now: now, calendar: calendar)
+        }
+
+        let newly = PetCare.unlockNewAchievements(state: &state, now: now, calendar: calendar)
+
+        XCTAssertTrue(newly.contains(.level5),
+                      "display level ≥ 5 should unlock .level5; got \(newly)")
+    }
+
+    // MARK: - 3. Token milestones
+
+    func testTokenMilestones() {
+        var state = PetCareState()
+        let now = date("2026-06-18 10:00")
+        // Feed 1M tokens total
+        PetCare.feedTokens(1_000_000, state: &state, now: now, calendar: calendar)
+
+        let newly = PetCare.unlockNewAchievements(state: &state, now: now, calendar: calendar)
+
+        XCTAssertTrue(newly.contains(.tokens1M),
+                      "1M total tokens should unlock .tokens1M; got \(newly)")
+    }
+
+    // MARK: - 4. Streak milestones
+
+    func testStreakMilestones() {
+        var state = PetCareState()
+        // Simulate 7 consecutive days of feeding
+        for day in 1...7 {
+            let d = date(String(format: "2026-06-%02d 10:00", day))
+            PetCare.recordMeal(state: &state, now: d, calendar: calendar)
+        }
+        let lastDay = date("2026-06-07 10:00")
+
+        let newly = PetCare.unlockNewAchievements(state: &state, now: lastDay, calendar: calendar)
+
+        XCTAssertTrue(newly.contains(.streak7),
+                      "7-day streak should unlock .streak7; got \(newly)")
+    }
+
+    // MARK: - 5. Night owl
+
+    func testNightOwl() {
+        var state = PetCareState()
+        // Feed at 2am UTC
+        let nightTime = date("2026-06-18 02:00")
+        PetCare.recordMeal(state: &state, now: nightTime, calendar: calendar)
+
+        let newly = PetCare.unlockNewAchievements(state: &state, now: nightTime, calendar: calendar)
+
+        XCTAssertTrue(newly.contains(.nightOwl),
+                      "feeding at 2am should unlock .nightOwl; got \(newly)")
+    }
+
+    // MARK: - 6. No double unlock
+
+    func testNoDoubleUnlock() {
+        var state = PetCareState()
+        let now = date("2026-06-18 10:00")
+        PetCare.recordMeal(state: &state, now: now, calendar: calendar)
+
+        // First call — should contain firstMeal
+        let first = PetCare.unlockNewAchievements(state: &state, now: now, calendar: calendar)
+        XCTAssertTrue(first.contains(.firstMeal))
+
+        // Second call with same state — firstMeal is already stored, must not appear again
+        let second = PetCare.unlockNewAchievements(state: &state, now: now, calendar: calendar)
+        XCTAssertFalse(second.contains(.firstMeal),
+                       "already-unlocked achievements must not be returned a second time")
+    }
+
+    // MARK: - 7. Backward compat
+
+    func testBackwardCompat() throws {
+        // JSON produced before unlockedAchievements field was added
+        let legacy = """
+        {"xp":200,"tokenCarry":0,"tokensToday":0,"mealsToday":0,\
+        "totalTokens":200000,"totalMeals":5,"dayKey":"2026-06-18",\
+        "streakDays":3}
+        """
+        let state = try JSONDecoder().decode(
+            PetCareState.self,
+            from: legacy.data(using: .utf8)!
+        )
+        XCTAssertNil(state.unlockedAchievements,
+                     "legacy JSON without achievements field must decode to nil")
+        XCTAssertEqual(state.xp, 200)
+    }
+
+    // MARK: - 8. checkAchievements is pure
+
+    func testCheckAchievementsIsPure() {
+        var state = PetCareState()
+        let now = date("2026-06-18 10:00")
+        PetCare.feedTokens(1_000_000, state: &state, now: now, calendar: calendar)
+
+        let resultA = PetCare.checkAchievements(state: state, hour: 10)
+        let resultB = PetCare.checkAchievements(state: state, hour: 10)
+
+        XCTAssertEqual(resultA, resultB,
+                       "checkAchievements must return identical sets for identical inputs")
+        // State must not have been mutated
+        XCTAssertNil(state.unlockedAchievements,
+                     "checkAchievements must not mutate state")
+    }
+}