fix: Remove newInboxProtectionWindow from LRU eviction (#518)

Remove the 12-minute protection window that prevented newly-created
inboxes from being evicted. When many recent inboxes exist (common
after creating/joining several conversations), all slots become
protected and eviction fails, causing push notification wakes to
fail with wakeCapacityExceeded.

Inboxes with nil lastActivity are now treated as preferred eviction
candidates since they have no message activity to lose. They will be
re-woken when the user navigates back to them.

Changes:
- Remove newInboxProtectionWindow constant from SleepingInboxMessageChecker
- Remove protection window check from sleepLeastRecentlyUsed()
- Update test to expect NULL activity inboxes to be evicted
- Remove obsolete test for protection window expiration

Author: yewreeka

ConvosCore/Sources/ConvosCore/Inboxes/InboxLifecycleManager.swift

@@ -650,36 +650,30 @@ public actor InboxLifecycleManager: InboxLifecycleManagerProtocol {
 
     /// Attempts to sleep the least recently used inbox to free capacity.
     ///
-    /// Inboxes with `nil` lastActivity are treated as "newly created" and protected from eviction
-    /// for `newInboxProtectionWindow` seconds after creation. This prevents newly created inboxes
-    /// (which haven't received messages yet) from being immediately evicted.
-    ///
-    /// Note: This differs from `SleepingInboxMessageChecker.findOldestAwakeLastActivity()` which
-    /// treats `nil` lastActivity as `.distantPast` for message timestamp comparisons. The semantics
-    /// differ because eviction protection (here) and message recency comparison (there) have
-    /// different goals.
+    /// Inboxes with `nil` lastActivity are treated as "never used" and are preferred eviction
+    /// candidates since they have no message activity to lose. The activity repository returns
+    /// inboxes sorted by lastActivity (oldest first, nil treated as distantPast), so iterating
+    /// from the end finds the most recently used inbox that can be evicted.
     ///
     /// - Returns: `true` if an inbox was successfully slept, `false` otherwise.
     @discardableResult
     private func sleepLeastRecentlyUsed(excluding excludedClientIds: Set<String>) async -> Bool {
         do {
             let activities = try activityRepository.allInboxActivities()
-            let newInboxThreshold = Date().addingTimeInterval(-SleepingInboxMessageChecker.newInboxProtectionWindow)
 
             let sleepCandidate = activities.last { activity in
                 awakeInboxes[activity.clientId] != nil &&
                 !excludedClientIds.contains(activity.clientId) &&
                 !pendingInviteClientIds.contains(activity.clientId) &&
-                activity.clientId != _activeClientId &&
-                (activity.lastActivity != nil || activity.createdAt < newInboxThreshold)
+                activity.clientId != _activeClientId
             }
 
             if let candidate = sleepCandidate {
                 Log.debug("LRU sleep candidate: \(candidate.clientId), lastActivity: \(candidate.lastActivity?.description ?? "nil"), createdAt: \(candidate.createdAt)")
                 await sleep(clientId: candidate.clientId)
                 return true
             } else {
-                Log.warning("No suitable inbox found for LRU sleep - all inboxes are protected, active, have pending invites, or are newly created")
+                Log.warning("No suitable inbox found for LRU sleep - all inboxes are active or have pending invites")
                 return false
             }
         } catch {

ConvosCore/Sources/ConvosCore/Inboxes/SleepingInboxMessageChecker.swift

@@ -11,10 +11,6 @@ public actor SleepingInboxMessageChecker {
     /// Default interval between periodic checks (60 seconds in production)
     public static let defaultCheckInterval: TimeInterval = 60
 
-    /// How long new inboxes with no activity are protected from eviction (multiple check cycles)
-    /// In production: 60 * 12 = 720 seconds (12 minutes)
-    public static let newInboxProtectionWindow: TimeInterval = defaultCheckInterval * 12
-
     private let checkInterval: TimeInterval
     private let environment: AppEnvironment
     private let activityRepository: any InboxActivityRepositoryProtocol

ConvosCore/Tests/ConvosCoreTests/InboxLifecycleManagerTests.swift

@@ -174,8 +174,8 @@ struct InboxLifecycleManagerTests {
         #expect(await manager.isAwake(clientId: "client-3"))
     }
 
-    @Test("Inbox with NULL lastActivity is not evicted by LRU")
-    func testNullActivityInboxNotEvicted() async throws {
+    @Test("Inbox with NULL lastActivity IS evicted by LRU (preferred candidate)")
+    func testNullActivityInboxIsEvicted() async throws {
         let fixtures = makeTestFixtures(maxAwake: 2)
         let manager = fixtures.manager
 
@@ -194,34 +194,8 @@ struct InboxLifecycleManagerTests {
 
         try await manager.wakeAndDiscard(clientId: "client-3", inboxId: "inbox-3", reason: .userInteraction)
 
-        #expect(await manager.isAwake(clientId: "client-2"), "NULL activity inbox should NOT be evicted")
-        #expect(await manager.isSleeping(clientId: "client-1"), "Inbox with activity should be evicted instead")
-        #expect(await manager.isAwake(clientId: "client-3"))
-    }
-
-    @Test("Old inbox with NULL lastActivity CAN be evicted after protection window")
-    func testOldNullActivityInboxCanBeEvicted() async throws {
-        let fixtures = makeTestFixtures(maxAwake: 2)
-        let manager = fixtures.manager
-
-        let recentDate = Date()
-        let oldCreatedAt = Date().addingTimeInterval(-(SleepingInboxMessageChecker.newInboxProtectionWindow + 60))
-
-        fixtures.activityRepo.activities = [
-            InboxActivity(clientId: "client-1", inboxId: "inbox-1", lastActivity: recentDate, conversationCount: 1),
-            InboxActivity(clientId: "client-2", inboxId: "inbox-2", lastActivity: nil, conversationCount: 0, createdAt: oldCreatedAt),
-            InboxActivity(clientId: "client-3", inboxId: "inbox-3", lastActivity: Date(), conversationCount: 1),
-        ]
-
-        try await manager.wakeAndDiscard(clientId: "client-1", inboxId: "inbox-1", reason: .appLaunch)
-        try await manager.wakeAndDiscard(clientId: "client-2", inboxId: "inbox-2", reason: .userInteraction)
-
-        #expect(await manager.awakeClientIds.count == 2)
-
-        try await manager.wakeAndDiscard(clientId: "client-3", inboxId: "inbox-3", reason: .userInteraction)
-
-        #expect(await manager.isSleeping(clientId: "client-2"), "Old NULL activity inbox SHOULD be evicted after protection window")
-        #expect(await manager.isAwake(clientId: "client-1"))
+        #expect(await manager.isSleeping(clientId: "client-2"), "NULL activity inbox SHOULD be evicted (no activity to lose)")
+        #expect(await manager.isAwake(clientId: "client-1"), "Inbox with activity should be preserved")
         #expect(await manager.isAwake(clientId: "client-3"))
     }