Read and write the widget snapshot through CalendarrCore

The snapshot format was an internal detail shared between the app and its own
widget extension. A second Mac app needs the same data, and the way to give it
that is a documented contract rather than a format it reverse-engineers and then
drifts from. Both targets now link CalendarrCore and go through SnapshotStore.

Shared/WidgetData.swift becomes a thin facade. The typealiases and the flat
colour accessors exist so the ~70 existing call sites across the app and the
widget views compile unchanged; they are a migration convenience, not a design.

The snapshot now carries what a reader outside this app actually needs:

coverageStart / coverageEnd, because the published window is ~7 days back and
~42 ahead. Outside it the snapshot holds no information, which is not the same
as holding no events — and only the writer knows where that edge is. Without it
a consumer renders a convincingly empty March and is simply wrong.

isLoggedIn plus a session record, so a reader can say "sign in to Calendarr"
rather than "open Calendarr once". The events are deleted on sign-out, so the
absence of a cache alone cannot tell those two apart.

writerVersion, purely so a mismatch between the two apps is diagnosable.

The coverage constants move to SnapshotCoverage, so the writer and the code that
reconstructs the window for older files can no longer disagree about it.

CalendarStore needs an explicit `import CalendarrCore` because the app target
builds with SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY, which requires the
defining module to be imported directly rather than picked up transitively.

Verified: builds for iOS and Mac Catalyst; CalendarrKit's 11 tests pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Calendarr iOS.xcodeproj/project.pbxproj

@@ -8,6 +8,8 @@
 
 /* Begin PBXBuildFile section */
 		D0001A0CABCDEF0100AB5001 /* CalendarrWidgets.appex in Embed Foundation Extensions */ = {isa = PBXBuildFile; fileRef = D0001A02ABCDEF0100AB5001 /* CalendarrWidgets.appex */; settings = {ATTRIBUTES = (RemoveHeadersOnCopy, ); }; };
+		CA1E4D0A0002000000000001 /* CalendarrCore in Frameworks */ = {isa = PBXBuildFile; productRef = CA1E4D0A0001000000000001 /* CalendarrCore */; };
+		CA1E4D0A0002000000000002 /* CalendarrCore in Frameworks */ = {isa = PBXBuildFile; productRef = CA1E4D0A0001000000000002 /* CalendarrCore */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -95,6 +97,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				CA1E4D0A0002000000000001 /* CalendarrCore in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -102,6 +105,7 @@
 			isa = PBXFrameworksBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				CA1E4D0A0002000000000002 /* CalendarrCore in Frameworks */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -175,6 +179,7 @@
 			);
 			name = "Calendarr iOS";
 			packageProductDependencies = (
+				CA1E4D0A0001000000000001 /* CalendarrCore */,
 			);
 			productName = "Calendarr iOS";
 			productReference = C0000B01FC4E10100AB5001 /* Calendarr iOS.app */;
@@ -198,6 +203,7 @@
 			);
 			name = CalendarrWidgets;
 			packageProductDependencies = (
+				CA1E4D0A0001000000000002 /* CalendarrCore */,
 			);
 			productName = CalendarrWidgets;
 			productReference = D0001A02ABCDEF0100AB5001 /* CalendarrWidgets.appex */;
@@ -235,6 +241,9 @@
 			);
 			mainGroup = C0000201FB4E10100AB5001;
 			minimizedProjectReferenceProxies = 1;
+			packageReferences = (
+				39450EFC302A266A0090DDD7 /* XCLocalSwiftPackageReference "../CalendarrKit" */,
+			);
 			preferredProjectObjectVersion = 77;
 			productRefGroup = C0000C01FB4E10100AB5001 /* Products */;
 			projectDirPath = "";
@@ -314,12 +323,10 @@
 			buildSettings = {
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 2;
 				DEVELOPMENT_TEAM = PP34X97WS3;
 				GENERATE_INFOPLIST_FILE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 26.5;
 				MACOSX_DEPLOYMENT_TARGET = 26.5;
-				MARKETING_VERSION = 1.0.1;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.local.scarriffle.Calendarr-iOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = auto;
@@ -341,12 +348,10 @@
 			buildSettings = {
 				BUNDLE_LOADER = "$(TEST_HOST)";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 2;
 				DEVELOPMENT_TEAM = PP34X97WS3;
 				GENERATE_INFOPLIST_FILE = YES;
 				IPHONEOS_DEPLOYMENT_TARGET = 26.5;
 				MACOSX_DEPLOYMENT_TARGET = 26.5;
-				MARKETING_VERSION = 1.0.1;
 				PRODUCT_BUNDLE_IDENTIFIER = "com.local.scarriffle.Calendarr-iOSTests";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = auto;
@@ -397,6 +402,7 @@
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COPY_PHASE_STRIP = NO;
+				CURRENT_PROJECT_VERSION = 7;
 				DEBUG_INFORMATION_FORMAT = dwarf;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
 				ENABLE_TESTABILITY = YES;
@@ -415,8 +421,9 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LOCALIZATION_PREFERS_STRING_CATALOGS = YES;
+				MARKETING_VERSION = 3.5;
 				MTL_ENABLE_DEBUG_INFO = INCLUDE_SOURCE;
 				MTL_FAST_MATH = YES;
 				ONLY_ACTIVE_ARCH = YES;
@@ -461,6 +468,7 @@
 				CLANG_WARN_UNREACHABLE_CODE = YES;
 				CLANG_WARN__DUPLICATE_METHOD_MATCH = YES;
 				COPY_PHASE_STRIP = NO;
+				CURRENT_PROJECT_VERSION = 7;
 				DEBUG_INFORMATION_FORMAT = "dwarf-with-dsym";
 				ENABLE_NS_ASSERTIONS = NO;
 				ENABLE_STRICT_OBJC_MSGSEND = YES;
@@ -473,8 +481,9 @@
 				GCC_WARN_UNINITIALIZED_AUTOS = YES_AGGRESSIVE;
 				GCC_WARN_UNUSED_FUNCTION = YES;
 				GCC_WARN_UNUSED_VARIABLE = YES;
-				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LOCALIZATION_PREFERS_STRING_CATALOGS = YES;
+				MARKETING_VERSION = 3.5;
 				MTL_ENABLE_DEBUG_INFO = NO;
 				MTL_FAST_MATH = YES;
 				SDKROOT = iphoneos;
@@ -490,9 +499,10 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_ENTITLEMENTS = "Calendarr iOS/Calendarr iOS.entitlements";
+				"CODE_SIGN_ENTITLEMENTS[sdk=macosx*]" = "Calendarr iOS/Calendarr iOS-Catalyst.entitlements";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 6;
 				DEVELOPMENT_TEAM = PP34X97WS3;
+				ENABLE_HARDENED_RUNTIME = YES;
 				ENABLE_PREVIEWS = YES;
 				GENERATE_INFOPLIST_FILE = YES;
 				INFOPLIST_KEY_CFBundleDisplayName = Calendarr;
@@ -506,18 +516,16 @@
 				INFOPLIST_KEY_UILaunchScreen_Generation = YES;
 				INFOPLIST_KEY_UIStatusBarStyle = UIStatusBarStyleDarkContent;
 				INFOPLIST_KEY_UISupportedInterfaceOrientations = UIInterfaceOrientationPortrait;
-				INFOPLIST_KEY_UISupportedInterfaceOrientations_iPad = "UIInterfaceOrientationLandscapeRight UIInterfaceOrientationPortrait";
 				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
 				);
-				MARKETING_VERSION = 3.5;
 				PRODUCT_BUNDLE_IDENTIFIER = com.scarriffleservices.calendarr.ios;
 				PRODUCT_NAME = "Calendarr iOS";
 				STRING_CATALOG_GENERATE_SYMBOLS = YES;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
-				SUPPORTS_MACCATALYST = NO;
+				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
@@ -526,6 +534,7 @@
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = 1;
+				"TARGETED_DEVICE_FAMILY[sdk=macosx*]" = 2;
 			};
 			name = Debug;
 		};
@@ -535,9 +544,10 @@
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME = AccentColor;
 				CODE_SIGN_ENTITLEMENTS = "Calendarr iOS/Calendarr iOS.entitlements";
+				"CODE_SIGN_ENTITLEMENTS[sdk=macosx*]" = "Calendarr iOS/Calendarr iOS-Catalyst.entitlements";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 6;
 				DEVELOPMENT_TEAM = PP34X97WS3;
+				ENABLE_HARDENED_RUNTIME = YES;
 				ENABLE_PREVIEWS = YES;
 				GENERATE_INFOPLIST_FILE = YES;
 				INFOPLIST_KEY_CFBundleDisplayName = Calendarr;
@@ -551,18 +561,16 @@
 				INFOPLIST_KEY_UILaunchScreen_Generation = YES;
 				INFOPLIST_KEY_UIStatusBarStyle = UIStatusBarStyleDarkContent;
 				INFOPLIST_KEY_UISupportedInterfaceOrientations = UIInterfaceOrientationPortrait;
-				INFOPLIST_KEY_UISupportedInterfaceOrientations_iPad = "UIInterfaceOrientationLandscapeRight UIInterfaceOrientationPortrait";
 				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
 				);
-				MARKETING_VERSION = 3.5;
 				PRODUCT_BUNDLE_IDENTIFIER = com.scarriffleservices.calendarr.ios;
 				PRODUCT_NAME = "Calendarr iOS";
 				STRING_CATALOG_GENERATE_SYMBOLS = YES;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
-				SUPPORTS_MACCATALYST = NO;
+				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_APPROACHABLE_CONCURRENCY = YES;
@@ -571,6 +579,7 @@
 				SWIFT_UPCOMING_FEATURE_MEMBER_IMPORT_VISIBILITY = YES;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = 1;
+				"TARGETED_DEVICE_FAMILY[sdk=macosx*]" = 2;
 			};
 			name = Release;
 		};
@@ -579,26 +588,25 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
 				CODE_SIGN_ENTITLEMENTS = CalendarrWidgets/CalendarrWidgets.entitlements;
+				"CODE_SIGN_ENTITLEMENTS[sdk=macosx*]" = "CalendarrWidgets/CalendarrWidgets-Catalyst.entitlements";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 2;
 				DEVELOPMENT_TEAM = PP34X97WS3;
 				GENERATE_INFOPLIST_FILE = NO;
 				INFOPLIST_FILE = CalendarrWidgets/Info.plist;
 				INFOPLIST_KEY_CFBundleDisplayName = "Calendarr Widgets";
 				INFOPLIST_KEY_NSHumanReadableCopyright = "© 2026 Scarriffleservices";
-				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
 					"@executable_path/../../Frameworks",
 				);
-				MARKETING_VERSION = 1.0.1;
 				PRODUCT_BUNDLE_IDENTIFIER = com.scarriffleservices.calendarr.ios.CalendarrWidgets;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
 				SKIP_INSTALL = YES;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
-				SUPPORTS_MACCATALYST = NO;
+				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_ACTIVE_COMPILATION_CONDITIONS = "DEBUG $(inherited)";
@@ -606,6 +614,7 @@
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = 1;
+				"TARGETED_DEVICE_FAMILY[sdk=macosx*]" = 2;
 			};
 			name = Debug;
 		};
@@ -614,32 +623,32 @@
 			buildSettings = {
 				ASSETCATALOG_COMPILER_GENERATE_SWIFT_ASSET_SYMBOL_EXTENSIONS = YES;
 				CODE_SIGN_ENTITLEMENTS = CalendarrWidgets/CalendarrWidgets.entitlements;
+				"CODE_SIGN_ENTITLEMENTS[sdk=macosx*]" = "CalendarrWidgets/CalendarrWidgets-Catalyst.entitlements";
 				CODE_SIGN_STYLE = Automatic;
-				CURRENT_PROJECT_VERSION = 2;
 				DEVELOPMENT_TEAM = PP34X97WS3;
 				GENERATE_INFOPLIST_FILE = NO;
 				INFOPLIST_FILE = CalendarrWidgets/Info.plist;
 				INFOPLIST_KEY_CFBundleDisplayName = "Calendarr Widgets";
 				INFOPLIST_KEY_NSHumanReadableCopyright = "© 2026 Scarriffleservices";
-				IPHONEOS_DEPLOYMENT_TARGET = 17.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 26.0;
 				LD_RUNPATH_SEARCH_PATHS = (
 					"$(inherited)",
 					"@executable_path/Frameworks",
 					"@executable_path/../../Frameworks",
 				);
-				MARKETING_VERSION = 1.0.1;
 				PRODUCT_BUNDLE_IDENTIFIER = com.scarriffleservices.calendarr.ios.CalendarrWidgets;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = iphoneos;
 				SKIP_INSTALL = YES;
 				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator";
-				SUPPORTS_MACCATALYST = NO;
+				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_COMPILATION_MODE = wholemodule;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = 1;
+				"TARGETED_DEVICE_FAMILY[sdk=macosx*]" = 2;
 			};
 			name = Release;
 		};
@@ -683,6 +692,24 @@
 			defaultConfigurationName = Release;
 		};
 /* End XCConfigurationList section */
+
+/* Begin XCSwiftPackageProductDependency section */
+		CA1E4D0A0001000000000001 /* CalendarrCore */ = {
+			isa = XCSwiftPackageProductDependency;
+			productName = CalendarrCore;
+		};
+		CA1E4D0A0001000000000002 /* CalendarrCore */ = {
+			isa = XCSwiftPackageProductDependency;
+			productName = CalendarrCore;
+		};
+/* End XCSwiftPackageProductDependency section */
+
+/* Begin XCLocalSwiftPackageReference section */
+		39450EFC302A266A0090DDD7 /* XCLocalSwiftPackageReference "../CalendarrKit" */ = {
+			isa = XCLocalSwiftPackageReference;
+			relativePath = ../CalendarrKit;
+		};
+/* End XCLocalSwiftPackageReference section */
 	};
 	rootObject = C0000301FB4E10100AB5001 /* Project object */;
 }

Calendarr iOS.xcodeproj/xcuserdata/scarriffle.xcuserdatad/xcschemes/xcschememanagement.plist

@@ -12,7 +12,7 @@
 		<key>CalendarrWidgets.xcscheme_^#shared#^_</key>
 		<dict>
 			<key>orderHint</key>
-			<integer>1</integer>
+			<integer>2</integer>
 		</dict>
 	</dict>
 	<key>SuppressBuildableAutocreation</key>

Calendarr iOS/Calendarr iOS-Catalyst.entitlements

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<!--
+	  Mac Catalyst entitlements. A separate file is required because the App
+	  Group value differs per platform: macOS demands the Team ID prefix, iOS
+	  forbids it, and listing both in one file breaks iOS provisioning.
+	  Selected via CODE_SIGN_ENTITLEMENTS[sdk=macosx*].
+
+	  This one file serves both distribution paths. app-sandbox is required by
+	  the Mac App Store and desirable for Developer ID; ENABLE_HARDENED_RUNTIME
+	  is required for notarization and ignored by the App Store. Only the
+	  signing identity differs, and that is chosen at export time.
+	-->
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+
+	<!-- Talks to the user's own Calendarr server. -->
+	<key>com.apple.security.network.client</key>
+	<true/>
+
+	<!-- BirthdaysImporter reads Contacts to sync birthdays. -->
+	<key>com.apple.security.personal-information.addressbook</key>
+	<true/>
+
+	<!-- .ics import (fileImporter) and calendar export (fileExporter). -->
+	<key>com.apple.security.files.user-selected.read-write</key>
+	<true/>
+
+	<!-- Must match CalendarrAppGroup.current on this platform, byte for byte. -->
+	<key>com.apple.security.application-groups</key>
+	<array>
+		<string>PP34X97WS3.group.com.scarriffleservices.calendarr</string>
+	</array>
+
+	<!-- Own group first: it stays the default access group, so tokens written
+	     before this entitlement existed keep resolving. The .shared group is
+	     what a second app from this team reads the auth token from. -->
+	<key>keychain-access-groups</key>
+	<array>
+		<string>$(AppIdentifierPrefix)com.scarriffleservices.calendarr.ios</string>
+		<string>$(AppIdentifierPrefix)com.scarriffleservices.calendarr.shared</string>
+	</array>
+</dict>
+</plist>

Calendarr iOS/Calendarr iOS.entitlements

@@ -6,5 +6,15 @@
 	<array>
 		<string>group.com.scarriffleservices.calendarr</string>
 	</array>
+	<!-- Order matters. Without this entitlement the default access group is
+	     <AppIdentifierPrefix><bundle id>, which is where every existing token
+	     lives. Adding the entitlement makes the FIRST entry the new default, so
+	     listing our own group first keeps those tokens resolving and nobody
+	     gets signed out. The .shared group is the one the Mac app also reads. -->
+	<key>keychain-access-groups</key>
+	<array>
+		<string>$(AppIdentifierPrefix)com.scarriffleservices.calendarr.ios</string>
+		<string>$(AppIdentifierPrefix)com.scarriffleservices.calendarr.shared</string>
+	</array>
 </dict>
 </plist>

Calendarr iOS/CalendarrApp.swift

@@ -1,5 +1,4 @@
 import SwiftUI
-import Security
 
 @main
 struct CalendarrApp: App {
@@ -25,17 +24,45 @@ class AppState {
 
     init() {
         serverURL = UserDefaults.standard.string(forKey: "serverURL") ?? ""
-        // Migrate a token previously kept in UserDefaults into the Keychain once,
-        // so existing logins survive the change without re-authenticating.
-        if let legacy = UserDefaults.standard.string(forKey: "authToken"), !legacy.isEmpty {
-            Keychain.set(legacy, for: "authToken")
-            UserDefaults.standard.removeObject(forKey: "authToken")
-        }
-        authToken = Keychain.get("authToken") ?? ""
+        authToken = Self.loadToken()
         username = UserDefaults.standard.string(forKey: "username") ?? ""
         isAdmin = UserDefaults.standard.bool(forKey: "isAdmin")
     }
 
+    /// Find the stored token, migrating it forward from wherever an older build
+    /// left it. Runs on every launch but does real work only once.
+    ///
+    /// Step 2 is the one that keeps existing users signed in. Before the
+    /// `keychain-access-groups` entitlement existed, items landed in the app's
+    /// own default group. Adding the entitlement makes the *first* array entry
+    /// the new default — and that entry is deliberately the app's own group, so
+    /// an unqualified query still resolves those items and we can copy them
+    /// across instead of stranding them.
+    private static func loadToken() -> String {
+        let key = "authToken"
+
+        // 1. Already in the shared group — the steady state.
+        if let token = try? KeychainStore.get(key), !token.isEmpty {
+            return token
+        }
+
+        // 2. In the app's own default group, written before the entitlement.
+        if let token = try? KeychainStore.get(key, accessGroup: nil), !token.isEmpty {
+            try? KeychainStore.set(token, for: key)
+            try? KeychainStore.set(nil, for: key, accessGroup: nil)
+            return token
+        }
+
+        // 3. In UserDefaults, written before secrets moved to the Keychain.
+        if let legacy = UserDefaults.standard.string(forKey: key), !legacy.isEmpty {
+            try? KeychainStore.set(legacy, for: key)
+            UserDefaults.standard.removeObject(forKey: key)
+            return legacy
+        }
+
+        return ""
+    }
+
     func saveServer(url: String) {
         serverURL = url.trimmingCharacters(in: .whitespacesAndNewlines)
         if serverURL.hasSuffix("/") { serverURL = String(serverURL.dropLast()) }
@@ -46,58 +73,45 @@ class AppState {
         authToken = token
         username = user
         isAdmin = admin
-        Keychain.set(token, for: "authToken")   // secret → Keychain, not UserDefaults
+        try? KeychainStore.set(token, for: "authToken")   // secret → Keychain, not UserDefaults
         UserDefaults.standard.set(user, forKey: "username")
         UserDefaults.standard.set(admin, forKey: "isAdmin")
+        publishSession()
+    }
+
+    /// Mirror the non-secret session facts into the shared container. Apps in
+    /// another sandbox cannot read our UserDefaults, so this is how they learn
+    /// which server we point at and whether anyone is signed in. The token
+    /// itself stays in the shared keychain group, never in a plain file.
+    private func publishSession() {
+        WidgetStore.writeSession(baseURL: serverURL,
+                                 username: username,
+                                 isLoggedIn: isLoggedIn)
     }
 
     func logout() {
         authToken = ""
         username = ""
         isAdmin = false
-        Keychain.set(nil, for: "authToken")
-        UserDefaults.standard.removeObject(forKey: "authToken")  // clear any legacy copy
+        try? KeychainStore.set(nil, for: "authToken")
+        try? KeychainStore.set(nil, for: "authToken", accessGroup: nil)  // pre-entitlement copy
+        UserDefaults.standard.removeObject(forKey: "authToken")          // pre-Keychain copy
         UserDefaults.standard.removeObject(forKey: "username")
         UserDefaults.standard.removeObject(forKey: "isAdmin")
+        // The shared container outlives the session, so it has to be cleared
+        // explicitly — otherwise widgets keep showing the signed-out user's data.
+        // The session record stays behind, flagged signed-out, so a reader can
+        // say "sign in to Calendarr" rather than "open Calendarr once".
+        WidgetStore.clear()
+        publishSession()
     }
 
     func resetServer() {
         logout()
         serverURL = ""
         UserDefaults.standard.removeObject(forKey: "serverURL")
-    }
-}
-
-/// Minimal Keychain wrapper for secrets (the auth bearer token). Values are
-/// stored as generic passwords, accessible after first unlock.
-enum Keychain {
-    private static let service = "Calendarr"
-
-    static func set(_ value: String?, for key: String) {
-        let base: [String: Any] = [
-            kSecClass as String: kSecClassGenericPassword,
-            kSecAttrService as String: service,
-            kSecAttrAccount as String: key,
-        ]
-        SecItemDelete(base as CFDictionary)
-        guard let value, let data = value.data(using: .utf8) else { return }
-        var add = base
-        add[kSecValueData as String] = data
-        add[kSecAttrAccessible as String] = kSecAttrAccessibleAfterFirstUnlock
-        SecItemAdd(add as CFDictionary, nil)
-    }
-
-    static func get(_ key: String) -> String? {
-        let query: [String: Any] = [
-            kSecClass as String: kSecClassGenericPassword,
-            kSecAttrService as String: service,
-            kSecAttrAccount as String: key,
-            kSecReturnData as String: true,
-            kSecMatchLimit as String: kSecMatchLimitOne,
-        ]
-        var out: AnyObject?
-        guard SecItemCopyMatching(query as CFDictionary, &out) == errSecSuccess,
-              let data = out as? Data else { return nil }
-        return String(data: data, encoding: .utf8)
+        // Back to unconfigured: there is no server left to name, so drop the
+        // session record rather than leaving a stale URL in the container.
+        WidgetStore.clearSession()
     }
 }

Calendarr iOS/Models/CalendarStore.swift

@@ -1,5 +1,6 @@
 import Foundation
 import SwiftUI
+import CalendarrCore
 
 extension Notification.Name {
     /// Posted whenever the persistent "banished calendars" set is mutated from
@@ -579,8 +580,12 @@ class CalendarStore {
         let now = Date()
         // Include the week before today so widgets that show the current week
         // (e.g. "This Week", "Up Next + Calendar") have data for Monday–today.
-        let from = cal.date(byAdding: .day, value: -7, to: cal.startOfDay(for: now)) ?? now
-        let to   = cal.date(byAdding: .day, value: 42, to: cal.startOfDay(for: now)) ?? from
+        // The window is published in the snapshot as coverageStart/coverageEnd:
+        // outside it a reader has no information, which is not the same as
+        // having no events, and only the writer knows where the edge is.
+        let dayStart = cal.startOfDay(for: now)
+        let from = cal.date(byAdding: .day, value: -SnapshotCoverage.daysBehind, to: dayStart) ?? now
+        let to   = cal.date(byAdding: .day, value: SnapshotCoverage.daysAhead, to: dayStart) ?? from
 
         // Build the calendar list from all cached events (not just the window)
         // so every calendar appears in the widget configuration picker.
@@ -604,7 +609,7 @@ class CalendarStore {
                     && !banishedCalendarKeys.contains(key)
             }
             .sorted { $0.startDate < $1.startDate }
-            .prefix(500)
+            .prefix(SnapshotCoverage.maxEvents)
             .map { ev in
                 WidgetEvent(id: ev.id,
                             title: ev.title,
@@ -615,19 +620,9 @@ class CalendarStore {
                             location: ev.location,
                             calendarKey: Self.calendarKey(source: ev.source, calendarId: ev.calendarId))
             }
-        let defaults = UserDefaults.standard
-        let snap = WidgetSnapshot(
-            writtenAt: now,
-            events: Array(visible),
-            todayColorHex:      defaults.string(forKey: "todayColor")       ?? "#4285f4",
-            textColorHex:       defaults.string(forKey: "textColor")        ?? "#FFFFFF",
-            backgroundColorHex: defaults.string(forKey: "backgroundColor")  ?? "#000000",
-            lineColorHex:       defaults.string(forKey: "lineColor")        ?? "#3A3A52",
-            primaryColorHex:    defaults.string(forKey: "primaryColor")     ?? "#4285f4",
-            accentColorHex:     defaults.string(forKey: "accentColor")      ?? "#ea4335",
-            language:           defaults.string(forKey: "appLanguage")      ?? "system"
-        )
-        WidgetStore.write(snap)
+        WidgetStore.write(WidgetStore.makeSnapshot(events: Array(visible),
+                                                   coverageStart: from,
+                                                   coverageEnd: to))
         WidgetTimelineNotifier.reload()
     }
 

Calendarr iOS/Services/KeychainStore.swift

@@ -0,0 +1,131 @@
+import Foundation
+import Security
+
+/// Keychain access for secrets (currently just the auth bearer token).
+///
+/// This replaces the earlier `enum Keychain`, which discarded every `OSStatus`.
+/// That mattered more than it looks: on Mac Catalyst a missing
+/// `keychain-access-groups` entitlement makes `SecItemAdd`/`SecItemCopyMatching`
+/// fail with `errSecMissingEntitlement`, and because nothing checked the status
+/// the result was indistinguishable from "no token stored" — the user was
+/// silently signed out on every launch.
+///
+/// Items live in a shared access group so the Mac build and other apps from the
+/// same team can read the token. Reading requires `keychain-access-groups` in
+/// the entitlements listing `sharedAccessGroup`.
+enum KeychainStore {
+    /// Access group shared across our apps. Must match an entry in the
+    /// `keychain-access-groups` entitlement of every app that uses it.
+    /// The `PP34X97WS3.` prefix is this account's Team ID — the same value
+    /// `$(AppIdentifierPrefix)` expands to at build time.
+    static let sharedAccessGroup = "PP34X97WS3.com.scarriffleservices.calendarr.shared"
+
+    private static let service = "Calendarr"
+
+    /// Set when a keychain call failed because the entitlement was missing and
+    /// we fell back to the app's own default access group. Signing is a build
+    /// configuration concern, so in DEBUG we make it loud; in release we keep
+    /// working rather than locking the user out of their own account.
+    private(set) nonisolated(unsafe) static var didFallBackToDefaultGroup = false
+
+    // MARK: - Public API
+
+    /// Store or delete a value. Passing `nil` deletes it.
+    static func set(_ value: String?, for key: String,
+                    accessGroup: String? = sharedAccessGroup) throws {
+        do {
+            try write(value, key: key, accessGroup: accessGroup)
+        } catch KeychainError.status(errSecMissingEntitlement, _) where accessGroup != nil {
+            noteEntitlementFallback()
+            try write(value, key: key, accessGroup: nil)
+        }
+    }
+
+    /// Read a value. Returns `nil` when the item simply is not there;
+    /// throws when the keychain itself refused the request.
+    static func get(_ key: String, accessGroup: String? = sharedAccessGroup) throws -> String? {
+        do {
+            return try read(key: key, accessGroup: accessGroup)
+        } catch KeychainError.status(errSecMissingEntitlement, _) where accessGroup != nil {
+            noteEntitlementFallback()
+            return try read(key: key, accessGroup: nil)
+        }
+    }
+
+    // MARK: - Implementation
+
+    private static func baseQuery(key: String, accessGroup: String?) -> [String: Any] {
+        var q: [String: Any] = [
+            kSecClass as String: kSecClassGenericPassword,
+            kSecAttrService as String: service,
+            kSecAttrAccount as String: key,
+            // Selects the modern, entitlement-gated keychain on macOS/Catalyst
+            // instead of the legacy file-based login keychain. Documented no-op
+            // on iOS 13+, so it is safe to set unconditionally.
+            kSecUseDataProtectionKeychain as String: true,
+        ]
+        if let accessGroup { q[kSecAttrAccessGroup as String] = accessGroup }
+        return q
+    }
+
+    private static func write(_ value: String?, key: String, accessGroup: String?) throws {
+        let base = baseQuery(key: key, accessGroup: accessGroup)
+
+        let deleteStatus = SecItemDelete(base as CFDictionary)
+        guard deleteStatus == errSecSuccess || deleteStatus == errSecItemNotFound else {
+            throw KeychainError.status(deleteStatus, operation: "delete \(key)")
+        }
+
+        guard let value, let data = value.data(using: .utf8) else { return }
+
+        var add = base
+        add[kSecValueData as String] = data
+        add[kSecAttrAccessible as String] = kSecAttrAccessibleAfterFirstUnlock
+
+        let addStatus = SecItemAdd(add as CFDictionary, nil)
+        guard addStatus == errSecSuccess else {
+            throw KeychainError.status(addStatus, operation: "add \(key)")
+        }
+    }
+
+    private static func read(key: String, accessGroup: String?) throws -> String? {
+        var query = baseQuery(key: key, accessGroup: accessGroup)
+        query[kSecReturnData as String] = true
+        query[kSecMatchLimit as String] = kSecMatchLimitOne
+
+        var out: AnyObject?
+        let status = SecItemCopyMatching(query as CFDictionary, &out)
+        switch status {
+        case errSecSuccess:
+            guard let data = out as? Data else { return nil }
+            return String(data: data, encoding: .utf8)
+        case errSecItemNotFound:
+            return nil
+        default:
+            throw KeychainError.status(status, operation: "read \(key)")
+        }
+    }
+
+    private static func noteEntitlementFallback() {
+        guard !didFallBackToDefaultGroup else { return }
+        didFallBackToDefaultGroup = true
+        assertionFailure("""
+            Keychain access group \(sharedAccessGroup) was refused \
+            (errSecMissingEntitlement). Add it to keychain-access-groups and \
+            enable Keychain Sharing on the App ID. Falling back to the app's \
+            own default group — the Mac app will not see this token.
+            """)
+    }
+}
+
+enum KeychainError: Error, LocalizedError {
+    case status(OSStatus, operation: String)
+
+    var errorDescription: String? {
+        switch self {
+        case let .status(status, operation):
+            let detail = SecCopyErrorMessageString(status, nil) as String? ?? "OSStatus \(status)"
+            return "Keychain \(operation) failed: \(detail)"
+        }
+    }
+}

CalendarrWidgets/CalendarIntent.swift

@@ -32,11 +32,16 @@ struct CalendarEntityQuery: EntityQuery {
 }
 
 /// Widget configuration intent: lets the user pick which calendars to show.
-/// An empty selection means "show all calendars" (the default).
+/// No selection means "show all calendars" (the default).
+///
+/// The parameter must be optional: WidgetConfigurationIntent requires every
+/// parameter type to be optional, and the macOS/Mac Catalyst SDK enforces that
+/// where the iOS one lets a bare array through. `nil` and `[]` are treated
+/// alike downstream, so this is behaviour-preserving.
 struct CalendarSelectionIntent: WidgetConfigurationIntent {
     static var title: LocalizedStringResource = "Kalender auswählen"
     static var description = IntentDescription("Wähle welche Kalender im Widget angezeigt werden. Leer = alle Kalender.")
 
     @Parameter(title: "Kalender")
-    var selectedCalendars: [CalendarAppEntity]
+    var selectedCalendars: [CalendarAppEntity]?
 }

CalendarrWidgets/CalendarrTimelineProvider.swift

@@ -38,19 +38,20 @@ struct CalendarrTimelineProvider: AppIntentTimelineProvider {
 
     private func filtered(_ snapshot: WidgetSnapshot?, by config: CalendarSelectionIntent) -> WidgetSnapshot? {
         guard let snapshot else { return nil }
-        let ids = config.selectedCalendars.map { $0.id }
-        guard !ids.isEmpty else { return snapshot }   // empty = show all
+        let ids = (config.selectedCalendars ?? []).map { $0.id }
+        guard !ids.isEmpty else { return snapshot }   // nothing selected = show all
         let keep = Set(ids)
+        // Filtering narrows the events but not the window: the snapshot still
+        // speaks for the same range, it just has fewer calendars in it.
         return WidgetSnapshot(
-            writtenAt:          snapshot.writtenAt,
-            events:             snapshot.events.filter { keep.contains($0.calendarKey) },
-            todayColorHex:      snapshot.todayColorHex,
-            textColorHex:       snapshot.textColorHex,
-            backgroundColorHex: snapshot.backgroundColorHex,
-            lineColorHex:       snapshot.lineColorHex,
-            primaryColorHex:    snapshot.primaryColorHex,
-            accentColorHex:     snapshot.accentColorHex,
-            language:           snapshot.language
+            writtenAt:     snapshot.writtenAt,
+            coverageStart: snapshot.coverageStart,
+            coverageEnd:   snapshot.coverageEnd,
+            isLoggedIn:    snapshot.isLoggedIn,
+            writerVersion: snapshot.writerVersion,
+            events:        snapshot.events.filter { keep.contains($0.calendarKey) },
+            theme:         snapshot.theme,
+            language:      snapshot.language
         )
     }
 }

CalendarrWidgets/CalendarrWidgets-Catalyst.entitlements

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<!--
+	  Mac Catalyst entitlements for the widget extension. Deliberately minimal:
+	  the widget only ever reads the snapshot from the App Group container. It
+	  does no networking, touches no Contacts, and needs no keychain access.
+	-->
+	<key>com.apple.security.app-sandbox</key>
+	<true/>
+
+	<!-- Must match CalendarrAppGroup.current on this platform, byte for byte. -->
+	<key>com.apple.security.application-groups</key>
+	<array>
+		<string>PP34X97WS3.group.com.scarriffleservices.calendarr</string>
+	</array>
+</dict>
+</plist>

Shared/WidgetData.swift

@@ -1,178 +1,136 @@
 import Foundation
+@_spi(Writer) import CalendarrCore
 #if canImport(WidgetKit)
 import WidgetKit
 #endif
 
-/// App-Group identifier shared between the main app and the widget extension.
-/// IMPORTANT: This must match the App Group capability in BOTH targets
-/// and the App Group ID registered in the Apple Developer Portal.
-let widgetAppGroupID = "group.com.scarriffleservices.calendarr"
+// The snapshot types and the App Group plumbing now live in CalendarrCore, so
+// that a second app from this team reads the exact same format instead of
+// reimplementing it and drifting.
+//
+// These aliases keep the ~70 existing call sites in the app and the widget
+// compiling unchanged. They are a migration convenience, not a design: new code
+// should use the CalendarrCore names directly.
+typealias WidgetEvent = SnapshotEvent
+typealias WidgetCalendar = SnapshotCalendar
+typealias WidgetSnapshot = CalendarrSnapshot
 
-/// Lightweight calendar descriptor stored alongside the event cache so the
-/// widget configuration intent can offer calendar options without a network call.
-struct WidgetCalendar: Codable, Identifiable, Hashable {
-    let id: String       // calendarKey ("source-calendarId")
-    let name: String
-    let colorHex: String
-}
-
-/// Lightweight event representation that lives inside the widget cache.
-/// We strip everything the widget doesn't need (notes, calendar IDs, URLs).
-struct WidgetEvent: Codable, Hashable, Identifiable {
-    let id: String
-    let title: String
-    let start: Date
-    let end: Date
-    let isAllDay: Bool
-    let colorHex: String
-    let location: String
-    let calendarKey: String   // used for per-calendar filtering in widget config
-
-    init(id: String, title: String, start: Date, end: Date,
-         isAllDay: Bool, colorHex: String, location: String, calendarKey: String) {
-        self.id = id; self.title = title; self.start = start; self.end = end
-        self.isAllDay = isAllDay; self.colorHex = colorHex
-        self.location = location; self.calendarKey = calendarKey
-    }
-
-    // Backward-compatible decoder: old caches have no calendarKey field.
-    init(from decoder: Decoder) throws {
-        let c = try decoder.container(keyedBy: CodingKeys.self)
-        id         = try c.decode(String.self, forKey: .id)
-        title      = try c.decode(String.self, forKey: .title)
-        start      = try c.decode(Date.self,   forKey: .start)
-        end        = try c.decode(Date.self,   forKey: .end)
-        isAllDay   = try c.decode(Bool.self,   forKey: .isAllDay)
-        colorHex   = try c.decode(String.self, forKey: .colorHex)
-        location   = try c.decode(String.self, forKey: .location)
-        calendarKey = try c.decodeIfPresent(String.self, forKey: .calendarKey) ?? ""
-    }
-}
-
-/// Snapshot blob the app writes to the App-Group container and the widget reads.
-struct WidgetSnapshot: Codable {
-    let writtenAt: Date
-    let events: [WidgetEvent]
-    /// Mirrors the user's chosen visual settings so the widget looks the same
-    /// as the app even when its own AppStorage in the extension is empty.
-    let todayColorHex: String
-    let textColorHex: String
-    let backgroundColorHex: String
-    let lineColorHex: String
-    let primaryColorHex: String
-    let accentColorHex: String
-    let language: String
-
-    init(writtenAt: Date,
-         events: [WidgetEvent],
-         todayColorHex: String,
-         textColorHex: String,
-         backgroundColorHex: String,
-         lineColorHex: String,
-         primaryColorHex: String,
-         accentColorHex: String,
-         language: String) {
-        self.writtenAt = writtenAt
-        self.events = events
-        self.todayColorHex = todayColorHex
-        self.textColorHex = textColorHex
-        self.backgroundColorHex = backgroundColorHex
-        self.lineColorHex = lineColorHex
-        self.primaryColorHex = primaryColorHex
-        self.accentColorHex = accentColorHex
-        self.language = language
-    }
-
-    /// Custom decoder so older caches without the new colour fields still load.
-    init(from decoder: Decoder) throws {
-        let c = try decoder.container(keyedBy: CodingKeys.self)
-        writtenAt          = try c.decode(Date.self,           forKey: .writtenAt)
-        events             = try c.decode([WidgetEvent].self,  forKey: .events)
-        todayColorHex      = try c.decode(String.self,         forKey: .todayColorHex)
-        textColorHex       = try c.decode(String.self,         forKey: .textColorHex)
-        backgroundColorHex = try c.decode(String.self,         forKey: .backgroundColorHex)
-        lineColorHex       = try c.decode(String.self,         forKey: .lineColorHex)
-        language           = try c.decode(String.self,         forKey: .language)
-        primaryColorHex    = try c.decodeIfPresent(String.self, forKey: .primaryColorHex) ?? "#4285f4"
-        accentColorHex     = try c.decodeIfPresent(String.self, forKey: .accentColorHex)  ?? "#ea4335"
-    }
-
-    private enum CodingKeys: String, CodingKey {
-        case writtenAt, events, todayColorHex, textColorHex, backgroundColorHex
-        case lineColorHex, primaryColorHex, accentColorHex, language
-    }
+/// The App Group identifier for this platform. See `CalendarrAppGroup`.
+let widgetAppGroupID = CalendarrAppGroup.current
+
+extension CalendarrSnapshot {
+    // The six colours are stored flat on the wire for backwards compatibility
+    // but exposed as `theme` in the package. These keep the widget views, which
+    // read them individually, from having to change.
+    var todayColorHex: String      { theme.today }
+    var textColorHex: String       { theme.text }
+    var backgroundColorHex: String { theme.background }
+    var lineColorHex: String       { theme.line }
+    var primaryColorHex: String    { theme.primary }
+    var accentColorHex: String     { theme.accent }
 }
 
+/// Thin facade over `CalendarrCore.SnapshotStore`, preserving the static API the
+/// app and widget already use. Errors are swallowed here exactly as before —
+/// a failed widget cache write must never interrupt the user — but the store now
+/// reports *why* a read failed, which is what `read()` discards and callers that
+/// need the distinction should use `SnapshotStore` directly for.
 enum WidgetStore {
-    private static let cacheFilename     = "widget-cache.json"
-    private static let calendarsFilename = "widget-calendars.json"
+    private static let store = SnapshotStore()
+    private static let sessions = SharedSessionStore()
 
-    private static var containerURL: URL? {
-        FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: widgetAppGroupID)
+    /// Version of the app writing the cache, for diagnostics in the consumer.
+    private static var writerVersion: String {
+        Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "unknown"
     }
 
-    private static var cacheURL: URL? {
-        containerURL?.appendingPathComponent(cacheFilename)
-    }
-
-    private static var calendarsURL: URL? {
-        containerURL?.appendingPathComponent(calendarsFilename)
-    }
-
-    /// Called by the app whenever the event cache changes.
     static func write(_ snapshot: WidgetSnapshot) {
-        guard let url = cacheURL else { return }
-        let encoder = JSONEncoder()
-        encoder.dateEncodingStrategy = .iso8601
-        if let data = try? encoder.encode(snapshot) {
-            try? data.write(to: url, options: .atomic)
-        }
+        try? store.write(snapshot)
     }
 
-    /// Called by the widget timeline provider to load the latest snapshot.
     static func read() -> WidgetSnapshot? {
-        guard let url = cacheURL, let data = try? Data(contentsOf: url) else { return nil }
-        let decoder = JSONDecoder()
-        decoder.dateDecodingStrategy = .iso8601
-        return try? decoder.decode(WidgetSnapshot.self, from: data)
+        store.read().snapshot
     }
 
-    /// Write the list of available calendars so the widget intent can offer
-    /// calendar options for filtering without a network call.
     static func writeCalendars(_ calendars: [WidgetCalendar]) {
-        guard let url = calendarsURL else { return }
-        if let data = try? JSONEncoder().encode(calendars) {
-            try? data.write(to: url, options: .atomic)
-        }
+        try? store.writeCalendars(calendars)
     }
 
-    /// Read the calendar list written by the main app.
     static func readCalendars() -> [WidgetCalendar] {
-        guard let url = calendarsURL, let data = try? Data(contentsOf: url) else { return [] }
-        return (try? JSONDecoder().decode([WidgetCalendar].self, from: data)) ?? []
+        store.readCalendars()
     }
 
-    /// Rewrite the existing snapshot with the latest colour / language values
-    /// from UserDefaults. Used when the user tweaks an appearance setting and
-    /// we want the widgets to refresh immediately, without needing a new event
-    /// sync. No-op if there's no cached snapshot yet.
+    /// Record which server we are pointed at and whether anyone is signed in, so
+    /// a reading app can tell "signed out" from "never ran" without reaching into
+    /// this app's UserDefaults, which lives in another sandbox.
+    static func writeSession(baseURL: String, username: String, isLoggedIn: Bool) {
+        try? sessions.write(SharedSession(baseURL: baseURL,
+                                          username: username,
+                                          isLoggedIn: isLoggedIn,
+                                          writtenAt: Date()))
+    }
+
+    /// Forget the session entirely. Used on server reset, where the app returns
+    /// to unconfigured and there is no longer a server worth naming.
+    static func clearSession() {
+        sessions.clear()
+    }
+
+    /// Drop the cached calendar. Called on sign-out and server reset: the
+    /// container outlives the session, so without this every reader keeps
+    /// rendering the previous user's events.
+    static func clear() {
+        store.clear()
+        WidgetTimelineNotifier.reload()
+    }
+
+    /// Rewrite the existing snapshot with the latest colour / language values so
+    /// widgets pick up an appearance change immediately, without waiting for the
+    /// next event sync. No-op when nothing is cached yet.
     static func republishAppearanceOnly() {
         guard let existing = read() else { return }
         let defaults = UserDefaults.standard
         let updated = WidgetSnapshot(
             writtenAt: Date(),
+            coverageStart: existing.coverageStart,
+            coverageEnd: existing.coverageEnd,
+            isLoggedIn: existing.isLoggedIn,
+            writerVersion: writerVersion,
             events: existing.events,
-            todayColorHex:      defaults.string(forKey: "todayColor")       ?? existing.todayColorHex,
-            textColorHex:       defaults.string(forKey: "textColor")        ?? existing.textColorHex,
-            backgroundColorHex: defaults.string(forKey: "backgroundColor")  ?? existing.backgroundColorHex,
-            lineColorHex:       defaults.string(forKey: "lineColor")        ?? existing.lineColorHex,
-            primaryColorHex:    defaults.string(forKey: "primaryColor")     ?? existing.primaryColorHex,
-            accentColorHex:     defaults.string(forKey: "accentColor")      ?? existing.accentColorHex,
-            language:           defaults.string(forKey: "appLanguage")      ?? existing.language
-        )
+            theme: SnapshotTheme(
+                today:      defaults.string(forKey: "todayColor")      ?? existing.theme.today,
+                text:       defaults.string(forKey: "textColor")       ?? existing.theme.text,
+                background: defaults.string(forKey: "backgroundColor") ?? existing.theme.background,
+                line:       defaults.string(forKey: "lineColor")       ?? existing.theme.line,
+                primary:    defaults.string(forKey: "primaryColor")    ?? existing.theme.primary,
+                accent:     defaults.string(forKey: "accentColor")     ?? existing.theme.accent),
+            language: defaults.string(forKey: "appLanguage") ?? existing.language)
         write(updated)
         WidgetTimelineNotifier.reload()
     }
+
+    /// Build a snapshot from the app's current state. Kept here so the coverage
+    /// window and the writer version are stamped in exactly one place.
+    static func makeSnapshot(events: [WidgetEvent],
+                             coverageStart: Date,
+                             coverageEnd: Date) -> WidgetSnapshot {
+        let defaults = UserDefaults.standard
+        return WidgetSnapshot(
+            writtenAt: Date(),
+            coverageStart: coverageStart,
+            coverageEnd: coverageEnd,
+            isLoggedIn: true,          // only ever written while signed in
+            writerVersion: writerVersion,
+            events: events,
+            theme: SnapshotTheme(
+                today:      defaults.string(forKey: "todayColor")      ?? "#4285f4",
+                text:       defaults.string(forKey: "textColor")       ?? "#FFFFFF",
+                background: defaults.string(forKey: "backgroundColor") ?? "#000000",
+                line:       defaults.string(forKey: "lineColor")       ?? "#3A3A52",
+                primary:    defaults.string(forKey: "primaryColor")    ?? "#4285f4",
+                accent:     defaults.string(forKey: "accentColor")     ?? "#ea4335"),
+            language: defaults.string(forKey: "appLanguage") ?? "system")
+    }
 }
 
 enum WidgetTimelineNotifier {