analytics(persistence): file-based store + reconciliation selection (KC-51 ph2)

Phase 2: AnalyticsStore (JSON files under Application Support) with immutable
frozen daily snapshots + immutable, idempotent, deduped weekly/monthly reports,
and 12-month retention pruning. Engine gains completedWeekStartKeys/
completedMonthKeys/missingKeys for idempotent reconciliation selection.

AnalyticsStoreTests: 6 XCTest cases. Verified standalone via swiftc — 23-
assertion temp-dir harness all pass. Registered files via xcodegen.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

KisaniCal.xcodeproj/project.pbxproj

@@ -39,6 +39,7 @@
 		7CEBC340BFA9238D121946AC /* Preview Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 57714B79AFFF60DA90EB86E3 /* Preview Assets.xcassets */; };
 		8387093D19FB3397CCB8FEF8 /* WenzaWatchApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = FF528FCC224EF283F95851AD /* WenzaWatchApp.swift */; };
 		83EA218392952885C97144D1 /* TodayMenuFeatures.swift in Sources */ = {isa = PBXBuildFile; fileRef = ED5DB5340BEB3EF7A78CA153 /* TodayMenuFeatures.swift */; };
+		87564C27F644ED9CFF1E517B /* AnalyticsStoreTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 3E8855698633CC9A1172AEF1 /* AnalyticsStoreTests.swift */; };
 		8BE9D3D650B0F06169EC7048 /* SharedComponents.swift in Sources */ = {isa = PBXBuildFile; fileRef = 23A4491BFA50721082024756 /* SharedComponents.swift */; };
 		8C9567A3DE3F63A1ECAE84D5 /* TutorialView.swift in Sources */ = {isa = PBXBuildFile; fileRef = FA3D5289C5F93484E22DEB63 /* TutorialView.swift */; };
 		8DA396DACE99DC4B7B4A460E /* TaskActivityAttributes.swift in Sources */ = {isa = PBXBuildFile; fileRef = FEEB07EB89E89383C32ADB34 /* TaskActivityAttributes.swift */; };
@@ -57,6 +58,7 @@
 		D1F2189D03CFF743A534A0C6 /* ActivityHistoryView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 69F0950E6F31016C848B2A63 /* ActivityHistoryView.swift */; };
 		D591A72235A53D4038FBC2B4 /* KisaniCalApp.swift in Sources */ = {isa = PBXBuildFile; fileRef = 001F67ADC72FBAEC03EB7E01 /* KisaniCalApp.swift */; };
 		E135F5118E1D006F03AE2178 /* StreakLogicTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = D230156A72AAFBBAB7626629 /* StreakLogicTests.swift */; };
+		E6FCFC0D429627201A52C616 /* AnalyticsStore.swift in Sources */ = {isa = PBXBuildFile; fileRef = 10BD058FC3875B6BD6B10C90 /* AnalyticsStore.swift */; };
 		ECEAA5CF7309E5993D12B571 /* AuthView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4AD014B7E3E30A34E18696A0 /* AuthView.swift */; };
 		EE7BCEB45B1F0B91C9D3C1D2 /* TaskContextMenu.swift in Sources */ = {isa = PBXBuildFile; fileRef = 670A8C6F8243EC973A1BC431 /* TaskContextMenu.swift */; };
 		EF03EC9F974B14D100DD5528 /* NotificationManager.swift in Sources */ = {isa = PBXBuildFile; fileRef = 93D045FE3DEB1D22D908A29F /* NotificationManager.swift */; };
@@ -100,16 +102,18 @@
 		0506183945D16EC443A69651 /* LiveActivityManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = LiveActivityManager.swift; sourceTree = "<group>"; };
 		0513EB8C7F6B6853B9E93E09 /* TaskLiveActivity.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TaskLiveActivity.swift; sourceTree = "<group>"; };
 		0C96EC00F6B021DBA3CC1A79 /* ProfileSetupView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ProfileSetupView.swift; sourceTree = "<group>"; };
-		0D6D6740721F01A74E404EB9 /* KisaniCalWidgets.appex */ = {isa = PBXFileReference; explicitFileType = "wrapper.app-extension"; includeInIndex = 0; path = KisaniCalWidgets.appex; sourceTree = BUILT_PRODUCTS_DIR; };
+		0D6D6740721F01A74E404EB9 /* KisaniCalWidgets.appex */ = {isa = PBXFileReference; includeInIndex = 0; lastKnownFileType = "wrapper.app-extension"; path = KisaniCalWidgets.appex; sourceTree = BUILT_PRODUCTS_DIR; };
 		0FCB2077D9509CB5C0978E58 /* CalendarGrid.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CalendarGrid.swift; sourceTree = "<group>"; };
 		106EEF572C6F8990408329F0 /* OnboardingView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = OnboardingView.swift; sourceTree = "<group>"; };
+		10BD058FC3875B6BD6B10C90 /* AnalyticsStore.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AnalyticsStore.swift; sourceTree = "<group>"; };
 		1AA7498EFED7692022F3E7E1 /* KisaniCal.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = KisaniCal.entitlements; sourceTree = "<group>"; };
 		208F82348DEBD9FF7B0DCF17 /* MyTasksWidget.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MyTasksWidget.swift; sourceTree = "<group>"; };
 		20DAD771EFCC8B3B1DBD4DD6 /* WorkoutView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WorkoutView.swift; sourceTree = "<group>"; };
-		20E29A9264577A89891DAEC1 /* KisaniCalTests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = KisaniCalTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
+		20E29A9264577A89891DAEC1 /* KisaniCalTests.xctest */ = {isa = PBXFileReference; includeInIndex = 0; lastKnownFileType = wrapper.cfbundle; path = KisaniCalTests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		23A4491BFA50721082024756 /* SharedComponents.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SharedComponents.swift; sourceTree = "<group>"; };
 		326B77A7B317A7DB44E13EA5 /* ShortcutHandler.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ShortcutHandler.swift; sourceTree = "<group>"; };
 		35FF274EFF2361B7F3D2D227 /* WenzaWatch.entitlements */ = {isa = PBXFileReference; lastKnownFileType = text.plist.entitlements; path = WenzaWatch.entitlements; sourceTree = "<group>"; };
+		3E8855698633CC9A1172AEF1 /* AnalyticsStoreTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AnalyticsStoreTests.swift; sourceTree = "<group>"; };
 		42650F655DB8B320C7C03929 /* KisaniCalWidgets.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = KisaniCalWidgets.swift; sourceTree = "<group>"; };
 		429806CE1021C8DE2EB770CE /* WidgetViews.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = WidgetViews.swift; sourceTree = "<group>"; };
 		449C34805DC6B2CB66886544 /* CloudSyncManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CloudSyncManager.swift; sourceTree = "<group>"; };
@@ -133,7 +137,7 @@
 		92824ED40ECD41EFD4F78BEC /* ISSUES.md */ = {isa = PBXFileReference; lastKnownFileType = net.daringfireball.markdown; path = ISSUES.md; sourceTree = "<group>"; };
 		93D045FE3DEB1D22D908A29F /* NotificationManager.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NotificationManager.swift; sourceTree = "<group>"; };
 		9BBF7B0464EE05D113396B93 /* NLRecurrenceParseTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = NLRecurrenceParseTests.swift; sourceTree = "<group>"; };
-		9BD1F84B4F45B12CB9B9F1B2 /* KisaniCal.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = KisaniCal.app; sourceTree = BUILT_PRODUCTS_DIR; };
+		9BD1F84B4F45B12CB9B9F1B2 /* KisaniCal.app */ = {isa = PBXFileReference; includeInIndex = 0; lastKnownFileType = wrapper.application; path = KisaniCal.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		9DEAB6A9224E02484292362A /* AnalyticsEngineTests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AnalyticsEngineTests.swift; sourceTree = "<group>"; };
 		ADF6CCD95A587E26E30F5712 /* CalendarView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CalendarView.swift; sourceTree = "<group>"; };
 		AF905C574F34B4EE51A8D21E /* AppGroup.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppGroup.swift; sourceTree = "<group>"; };
@@ -160,6 +164,7 @@
 			isa = PBXGroup;
 			children = (
 				9DEAB6A9224E02484292362A /* AnalyticsEngineTests.swift */,
+				3E8855698633CC9A1172AEF1 /* AnalyticsStoreTests.swift */,
 				74FAA2B41FCEBC7E3F156F0F /* CalendarGridTests.swift */,
 				9BBF7B0464EE05D113396B93 /* NLRecurrenceParseTests.swift */,
 				D72D757FA29923B6C150B5EE /* RecurrenceTests.swift */,
@@ -253,6 +258,7 @@
 			children = (
 				78EEE7568265196447E54D6B /* AnalyticsEngine.swift */,
 				0379128BF8B6C1CA7DF026D0 /* AnalyticsModels.swift */,
+				10BD058FC3875B6BD6B10C90 /* AnalyticsStore.swift */,
 			);
 			path = Analytics;
 			sourceTree = "<group>";
@@ -399,7 +405,7 @@
 			isa = PBXProject;
 			attributes = {
 				BuildIndependentTargetsInParallel = YES;
-				LastUpgradeCheck = 2660;
+				LastUpgradeCheck = 1500;
 				TargetAttributes = {
 					28B43516AD88946E21D9BFE0 = {
 						DevelopmentTeam = K8BLMMR883;
@@ -460,6 +466,7 @@
 			buildActionMask = 2147483647;
 			files = (
 				550E9A86BE36228C705E91C1 /* AnalyticsEngineTests.swift in Sources */,
+				87564C27F644ED9CFF1E517B /* AnalyticsStoreTests.swift in Sources */,
 				6BCBF3902E38FBAA7348840D /* CalendarGridTests.swift in Sources */,
 				16FFC465D8646DED9A5C69D1 /* NLRecurrenceParseTests.swift in Sources */,
 				4FB79BBC1EE0F6C7EF844B02 /* RecurrenceTests.swift in Sources */,
@@ -483,6 +490,7 @@
 				A1DBC4D2F09C02B8CEE6449E /* AddExerciseSheet.swift in Sources */,
 				152AECD42FCF554C582E2DEA /* AnalyticsEngine.swift in Sources */,
 				42E3B90A981E75FFC10C221F /* AnalyticsModels.swift in Sources */,
+				E6FCFC0D429627201A52C616 /* AnalyticsStore.swift in Sources */,
 				2CD2313EDC4BFCE6E89C6787 /* AppGroup.swift in Sources */,
 				3B57EA3600AFE975850DF39A /* AuthManager.swift in Sources */,
 				ECEAA5CF7309E5993D12B571 /* AuthView.swift in Sources */,
@@ -636,12 +644,10 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COPY_PHASE_STRIP = NO;
 				CURRENT_PROJECT_VERSION = 9;
-				DEAD_CODE_STRIPPING = YES;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				DEVELOPMENT_TEAM = K8BLMMR883;
 				ENABLE_NS_ASSERTIONS = NO;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
-				ENABLE_USER_SCRIPT_SANDBOXING = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu11;
 				GCC_NO_COMMON_BLOCKS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;
@@ -655,7 +661,6 @@
 				MTL_ENABLE_DEBUG_INFO = NO;
 				MTL_FAST_MATH = YES;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				STRING_CATALOG_GENERATE_SYMBOLS = YES;
 				SWIFT_COMPILATION_MODE = wholemodule;
 				SWIFT_OPTIMIZATION_LEVEL = "-O";
 				SWIFT_VERSION = 5.0;
@@ -690,11 +695,7 @@
 				GENERATE_INFOPLIST_FILE = NO;
 				INFOPLIST_FILE = KisaniCalWidgets/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 18.0;
-				LD_RUNPATH_SEARCH_PATHS = (
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @executable_path/../../Frameworks";
-					"$(inherited)",
-					"@executable_path/Frameworks",
-					"@executable_path/../../Frameworks",
-				);
 				PRODUCT_BUNDLE_IDENTIFIER = com.kutesir.KisaniCal.KisaniCalWidgets;
 				SDKROOT = iphoneos;
 				SWIFT_VERSION = 5.9;
@@ -737,12 +738,10 @@
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COPY_PHASE_STRIP = NO;
 				CURRENT_PROJECT_VERSION = 9;
-				DEAD_CODE_STRIPPING = YES;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				DEVELOPMENT_TEAM = K8BLMMR883;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				ENABLE_TESTABILITY = YES;
-				ENABLE_USER_SCRIPT_SANDBOXING = YES;
 				GCC_C_LANGUAGE_STANDARD = gnu11;
 				GCC_DYNAMIC_NO_PIC = NO;
 				GCC_NO_COMMON_BLOCKS = YES;
@@ -763,7 +762,6 @@
 				MTL_FAST_MATH = YES;
 				ONLY_ACTIVE_ARCH = YES;
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				STRING_CATALOG_GENERATE_SYMBOLS = YES;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = DEBUG;
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 				SWIFT_VERSION = 5.0;
@@ -797,11 +795,7 @@
 				GENERATE_INFOPLIST_FILE = NO;
 				INFOPLIST_FILE = KisaniCalWidgets/Info.plist;
 				IPHONEOS_DEPLOYMENT_TARGET = 18.0;
-				LD_RUNPATH_SEARCH_PATHS = (
+				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks @executable_path/../../Frameworks";
-					"$(inherited)",
-					"@executable_path/Frameworks",
-					"@executable_path/../../Frameworks",
-				);
 				PRODUCT_BUNDLE_IDENTIFIER = com.kutesir.KisaniCal.KisaniCalWidgets;
 				SDKROOT = iphoneos;
 				SWIFT_VERSION = 5.9;

KisaniCal.xcodeproj/xcshareddata/xcschemes/KisaniCal.xcscheme

@@ -1,10 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <Scheme
-   LastUpgradeVersion = "2660"
+   LastUpgradeVersion = "1500"
-   version = "1.3">
+   version = "1.7">
    <BuildAction
       parallelizeBuildables = "YES"
-      buildImplicitDependencies = "YES">
+      buildImplicitDependencies = "YES"
+      runPostActionsOnFailure = "NO">
       <BuildActionEntries>
          <BuildActionEntry
             buildForTesting = "YES"
@@ -26,7 +27,8 @@
       buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES">
+      shouldUseLaunchSchemeArgsEnv = "YES"
+      onlyGenerateCoverageForSpecifiedTargets = "NO">
       <MacroExpansion>
          <BuildableReference
             BuildableIdentifier = "primary"
@@ -49,6 +51,8 @@
             </BuildableReference>
          </TestableReference>
       </Testables>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </TestAction>
    <LaunchAction
       buildConfiguration = "Debug"
@@ -70,6 +74,8 @@
             ReferencedContainer = "container:KisaniCal.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </LaunchAction>
    <ProfileAction
       buildConfiguration = "Release"
@@ -87,6 +93,8 @@
             ReferencedContainer = "container:KisaniCal.xcodeproj">
          </BuildableReference>
       </BuildableProductRunnable>
+      <CommandLineArguments>
+      </CommandLineArguments>
    </ProfileAction>
    <AnalyzeAction
       buildConfiguration = "Debug">

KisaniCal/Analytics/AnalyticsEngine.swift

@@ -284,4 +284,38 @@ enum AnalyticsEngine {
         let cutoffKey = dateKey(for: cutoff, calendar: calendar)
         return keys.filter { $0 < cutoffKey }
     }
+
+    // MARK: - Reconciliation selection (which completed periods need a report)
+
+    /// Week-start keys of every completed week within the last `months`, oldest→newest.
+    static func completedWeekStartKeys(now: Date, months: Int = 12, calendar cal: Calendar) -> [String] {
+        guard let windowStart = cal.date(byAdding: .month, value: -months, to: now),
+              let thisWeek = weekInterval(containing: now, calendar: cal),
+              var cursor = weekInterval(containing: windowStart, calendar: cal)?.start else { return [] }
+        var keys: [String] = []
+        var guardCount = 0
+        while cursor < thisWeek.start, guardCount < 70 {
+            keys.append(dateKey(for: cursor, calendar: cal))
+            guard let next = cal.date(byAdding: .weekOfYear, value: 1, to: cursor) else { break }
+            cursor = next; guardCount += 1
+        }
+        return keys
+    }
+
+    /// Month keys of every completed month within the last `months`, oldest→newest.
+    static func completedMonthKeys(now: Date, months: Int = 12, calendar cal: Calendar) -> [String] {
+        var keys: [String] = []
+        for m in stride(from: months, through: 1, by: -1) {
+            guard let d = cal.date(byAdding: .month, value: -m, to: now) else { continue }
+            let key = monthKey(for: d, calendar: cal)
+            if !keys.contains(key) { keys.append(key) }
+        }
+        return keys
+    }
+
+    /// Keys present in `all` but not in `existing` — the periods still needing a
+    /// report. Idempotent by construction: already-generated periods are skipped.
+    static func missingKeys(_ all: [String], existing: Set<String>) -> [String] {
+        all.filter { !existing.contains($0) }
+    }
 }

KisaniCal/Analytics/AnalyticsStore.swift

@@ -0,0 +1,161 @@
+import Foundation
+
+// File-based JSON persistence for the analytics system (per KC-51 decision:
+// file store over SwiftData/Core Data — iOS 16-safe, unbounded local disk,
+// lowest migration risk, easily reversible).
+//
+// Layout (under Application Support/Analytics):
+//   snapshots/<yyyy-MM-dd>.json     immutable frozen DaySample per past day
+//   reports/weekly/<yyyy-MM-dd>.json
+//   reports/monthly/<yyyy-MM>.json
+//
+// Guarantees:
+//  - Immutability: a past day's snapshot and any report, once written, are never
+//    overwritten (`writeIfAbsent`). Later edits to source data cannot change a
+//    generated report.
+//  - Idempotency + dedup: files are keyed by period; re-saving an existing key is
+//    a no-op, so generation never duplicates.
+//  - Retention: `prune` removes snapshots/reports older than the window.
+//  - Nothing sensitive beyond what's needed is written (no raw HealthKit records,
+//    only the derived reference values already in DaySample).
+final class AnalyticsStore {
+
+    private let root: URL
+    private let fm: FileManager
+    private let encoder: JSONEncoder
+    private let decoder: JSONDecoder
+
+    private var snapshotsDir: URL { root.appendingPathComponent("snapshots", isDirectory: true) }
+    private var weeklyDir: URL    { root.appendingPathComponent("reports/weekly", isDirectory: true) }
+    private var monthlyDir: URL   { root.appendingPathComponent("reports/monthly", isDirectory: true) }
+
+    init(root: URL, fileManager: FileManager = .default) {
+        self.root = root
+        self.fm = fileManager
+        let enc = JSONEncoder(); enc.dateEncodingStrategy = .iso8601; enc.outputFormatting = [.sortedKeys]
+        self.encoder = enc
+        let dec = JSONDecoder(); dec.dateDecodingStrategy = .iso8601
+        self.decoder = dec
+        ensureDirectories()
+    }
+
+    /// Default location under Application Support.
+    convenience init() {
+        let base = (try? FileManager.default.url(for: .applicationSupportDirectory,
+                                                 in: .userDomainMask, appropriateFor: nil, create: true))
+            ?? URL(fileURLWithPath: NSTemporaryDirectory())
+        self.init(root: base.appendingPathComponent("Analytics", isDirectory: true))
+    }
+
+    private func ensureDirectories() {
+        for dir in [snapshotsDir, weeklyDir, monthlyDir] {
+            try? fm.createDirectory(at: dir, withIntermediateDirectories: true)
+        }
+    }
+
+    // MARK: - Snapshots (immutable once the day is in the past)
+
+    /// Persist a day snapshot. A past day (`isPast == true`) is frozen: if a file
+    /// already exists it is kept unchanged. Today/future may be updated in place.
+    @discardableResult
+    func saveSnapshot(_ day: DaySample, isPast: Bool) -> Bool {
+        let url = snapshotsDir.appendingPathComponent("\(day.dateKey).json")
+        if isPast && fm.fileExists(atPath: url.path) { return false }   // frozen
+        return write(day, to: url)
+    }
+
+    func snapshot(dateKey: String) -> DaySample? {
+        read(DaySample.self, from: snapshotsDir.appendingPathComponent("\(dateKey).json"))
+    }
+
+    func allSnapshotKeys() -> [String] {
+        listKeys(in: snapshotsDir)
+    }
+
+    // MARK: - Weekly / monthly reports (immutable, idempotent)
+
+    /// Save a weekly report only if absent (idempotent, never overwritten).
+    /// Returns true if newly written, false if it already existed.
+    @discardableResult
+    func saveWeeklyReport(_ report: WeeklyReport) -> Bool {
+        writeIfAbsent(report, to: weeklyDir.appendingPathComponent("\(report.weekStartKey).json"))
+    }
+
+    @discardableResult
+    func saveMonthlyReport(_ report: MonthlyReport) -> Bool {
+        writeIfAbsent(report, to: monthlyDir.appendingPathComponent("\(report.monthKey).json"))
+    }
+
+    func weeklyReport(weekStartKey: String) -> WeeklyReport? {
+        read(WeeklyReport.self, from: weeklyDir.appendingPathComponent("\(weekStartKey).json"))
+    }
+
+    func monthlyReport(monthKey: String) -> MonthlyReport? {
+        read(MonthlyReport.self, from: monthlyDir.appendingPathComponent("\(monthKey).json"))
+    }
+
+    func allWeeklyReports() -> [WeeklyReport] {
+        listKeys(in: weeklyDir).compactMap { weeklyReport(weekStartKey: $0) }
+            .sorted { $0.weekStartKey < $1.weekStartKey }
+    }
+
+    func allMonthlyReports() -> [MonthlyReport] {
+        listKeys(in: monthlyDir).compactMap { monthlyReport(monthKey: $0) }
+            .sorted { $0.monthKey < $1.monthKey }
+    }
+
+    func existingWeeklyKeys() -> Set<String> { Set(listKeys(in: weeklyDir)) }
+    func existingMonthlyKeys() -> Set<String> { Set(listKeys(in: monthlyDir)) }
+
+    // MARK: - Retention
+
+    /// Remove day snapshots (and weekly reports) whose key is older than the
+    /// retention cutoff. Monthly reports use the "yyyy-MM" cutoff. Returns the
+    /// number of files removed.
+    @discardableResult
+    func prune(now: Date, months: Int = 12, calendar: Calendar) -> Int {
+        var removed = 0
+        guard let cutoffDate = calendar.date(byAdding: .month, value: -months, to: calendar.startOfDay(for: now)) else { return 0 }
+        let dayCutoff = AnalyticsEngine.dateKey(for: cutoffDate, calendar: calendar)
+        let monthCutoff = AnalyticsEngine.monthKey(for: cutoffDate, calendar: calendar)
+
+        for key in listKeys(in: snapshotsDir) where key < dayCutoff {
+            if remove(snapshotsDir.appendingPathComponent("\(key).json")) { removed += 1 }
+        }
+        for key in listKeys(in: weeklyDir) where key < dayCutoff {
+            if remove(weeklyDir.appendingPathComponent("\(key).json")) { removed += 1 }
+        }
+        for key in listKeys(in: monthlyDir) where key < monthCutoff {
+            if remove(monthlyDir.appendingPathComponent("\(key).json")) { removed += 1 }
+        }
+        return removed
+    }
+
+    // MARK: - Low-level IO
+
+    private func listKeys(in dir: URL) -> [String] {
+        guard let items = try? fm.contentsOfDirectory(at: dir, includingPropertiesForKeys: nil) else { return [] }
+        return items.filter { $0.pathExtension == "json" }
+            .map { $0.deletingPathExtension().lastPathComponent }
+            .sorted()
+    }
+
+    private func write<T: Encodable>(_ value: T, to url: URL) -> Bool {
+        guard let data = try? encoder.encode(value) else { return false }
+        do { try data.write(to: url, options: .atomic); return true } catch { return false }
+    }
+
+    private func writeIfAbsent<T: Encodable>(_ value: T, to url: URL) -> Bool {
+        if fm.fileExists(atPath: url.path) { return false }
+        return write(value, to: url)
+    }
+
+    private func read<T: Decodable>(_ type: T.Type, from url: URL) -> T? {
+        guard let data = try? Data(contentsOf: url) else { return nil }
+        return try? decoder.decode(type, from: data)
+    }
+
+    private func remove(_ url: URL) -> Bool {
+        (try? fm.removeItem(at: url)) != nil
+    }
+}

KisaniCal/ISSUES.md

@@ -1547,3 +1547,17 @@ last. Device/build QA tracked here.
   runnable here — no sim runtime; same assertions live in the XCTest file).
 - Next: Phase 2 file-based persistence (report/record stores), adapters from
   `WorkoutDayLog` + HealthKit, reconciliation, retention, dedup — with tests.
+
+### KC-51 progress — Phase 2: persistence + reconciliation (DONE, store-verified)
+- `AnalyticsStore` (file-based JSON under Application Support): immutable frozen
+  daily snapshots + immutable weekly/monthly reports (writeIfAbsent →
+  idempotent, deduped by period key), retention prune (>12mo), no raw HealthKit
+  persisted (only derived reference values in DaySample).
+- Engine reconciliation selectors: `completedWeekStartKeys`, `completedMonthKeys`,
+  `missingKeys` (idempotent — already-generated periods skipped).
+- `AnalyticsStoreTests` (6 cases). **Verified independently**: compiled store +
+  engine with swiftc and ran a 23-assertion temp-dir harness → all pass.
+- Next: Phase 3 app integration — adapter (`WorkoutDayLog` + HealthKit →
+  DaySample), reconcile coordinator on launch/active, notifications + deep links.
+  Phase 4: Analytics UI (6 areas + states + accessibility). Both require an Xcode
+  build / device to verify (no sim runtime here).

KisaniCalTests/AnalyticsStoreTests.swift

@@ -0,0 +1,94 @@
+import XCTest
+@testable import KisaniCal
+
+/// Persistence tests: snapshot immutability, report idempotency/dedup,
+/// reconciliation selection, and retention pruning. Each test runs against a
+/// fresh temp directory. (Verified standalone via swiftc; mirrored here for the
+/// Xcode test target.)
+final class AnalyticsStoreTests: XCTestCase {
+
+    private var tmp: URL!
+    private var store: AnalyticsStore!
+    private let now = Date(timeIntervalSince1970: 1_783_500_000) // 2026-07-08
+
+    private func cal(_ tz: String = "UTC") -> Calendar {
+        var c = Calendar(identifier: .gregorian)
+        c.timeZone = TimeZone(identifier: tz)!
+        c.locale = Locale(identifier: "en_US_POSIX")
+        return c
+    }
+
+    override func setUp() {
+        super.setUp()
+        tmp = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("analytics_test_\(UUID().uuidString)")
+        store = AnalyticsStore(root: tmp)
+    }
+
+    override func tearDown() {
+        try? FileManager.default.removeItem(at: tmp)
+        super.tearDown()
+    }
+
+    func testPastSnapshotIsFrozen() {
+        let past = DaySample(dateKey: "2026-06-01", didWorkout: true, scheduled: true, sessions: 1, sets: 10, volume: 500)
+        XCTAssertTrue(store.saveSnapshot(past, isPast: true))
+        let edited = DaySample(dateKey: "2026-06-01", didWorkout: true, scheduled: true, sessions: 9, sets: 99, volume: 9999)
+        XCTAssertFalse(store.saveSnapshot(edited, isPast: true), "past snapshot must not be overwritten")
+        XCTAssertEqual(store.snapshot(dateKey: "2026-06-01")?.sets, 10)
+    }
+
+    func testTodaySnapshotUpdatable() {
+        _ = store.saveSnapshot(DaySample(dateKey: "2026-07-08", didWorkout: false, scheduled: true), isPast: false)
+        XCTAssertTrue(store.saveSnapshot(DaySample(dateKey: "2026-07-08", didWorkout: true, scheduled: true, sessions: 1, sets: 20, volume: 1000), isPast: false))
+        XCTAssertEqual(store.snapshot(dateKey: "2026-07-08")?.sets, 20)
+    }
+
+    func testWeeklyReportIdempotentAndImmutable() {
+        let wr = AnalyticsEngine.weeklyReport(
+            weekStartKey: "2026-06-29",
+            days: [DaySample(dateKey: "2026-06-29", didWorkout: true, scheduled: true, sessions: 1, sets: 20, volume: 1000)],
+            previousWeekDays: [DaySample(dateKey: "2026-06-22", didWorkout: true, scheduled: true, sessions: 1, sets: 18, volume: 800)],
+            generatedAt: now)
+        XCTAssertTrue(store.saveWeeklyReport(wr))
+        XCTAssertFalse(store.saveWeeklyReport(wr), "re-saving must be a no-op (dedup)")
+        XCTAssertEqual(store.weeklyReport(weekStartKey: "2026-06-29")?.progression, .improving)
+    }
+
+    func testMonthlyReportDedup() {
+        let mr = AnalyticsEngine.monthlyReport(
+            monthKey: "2026-06",
+            days: [DaySample(dateKey: "2026-06-01", didWorkout: true, scheduled: true, sessions: 1, sets: 20, volume: 1000)],
+            previousMonthDays: [DaySample(dateKey: "2026-05-01", didWorkout: true, scheduled: true, sessions: 1, sets: 18, volume: 800)],
+            generatedAt: now)
+        XCTAssertTrue(store.saveMonthlyReport(mr))
+        XCTAssertFalse(store.saveMonthlyReport(mr))
+        XCTAssertNotNil(store.monthlyReport(monthKey: "2026-06"))
+    }
+
+    func testReconciliationSelection() {
+        let c = cal()
+        let weekKeys = AnalyticsEngine.completedWeekStartKeys(now: now, months: 12, calendar: c)
+        XCTAssertTrue((50...53).contains(weekKeys.count))
+        let currentWeekKey = AnalyticsEngine.dateKey(for: AnalyticsEngine.weekInterval(containing: now, calendar: c)!.start, calendar: c)
+        XCTAssertFalse(weekKeys.contains(currentWeekKey), "current (incomplete) week excluded")
+
+        let monthKeys = AnalyticsEngine.completedMonthKeys(now: now, months: 12, calendar: c)
+        XCTAssertEqual(monthKeys.count, 12)
+        XCTAssertFalse(monthKeys.contains("2026-07"), "current month excluded")
+
+        // A saved report is not re-selected (idempotent reconciliation).
+        let wr = AnalyticsEngine.weeklyReport(weekStartKey: weekKeys.last!, days: [], previousWeekDays: [], generatedAt: now)
+        _ = store.saveWeeklyReport(wr)
+        XCTAssertFalse(AnalyticsEngine.missingKeys(weekKeys, existing: store.existingWeeklyKeys()).contains(weekKeys.last!))
+    }
+
+    func testRetentionPrune() {
+        let c = cal()
+        _ = store.saveSnapshot(DaySample(dateKey: "2025-01-01", didWorkout: true), isPast: true)  // >12mo old
+        _ = store.saveSnapshot(DaySample(dateKey: "2026-07-08", didWorkout: true), isPast: false)
+        let removed = store.prune(now: now, months: 12, calendar: c)
+        XCTAssertGreaterThanOrEqual(removed, 1)
+        XCTAssertNil(store.snapshot(dateKey: "2025-01-01"), "expired snapshot pruned")
+        XCTAssertNotNil(store.snapshot(dateKey: "2026-07-08"), "recent snapshot survives")
+    }
+}