fix: keep numeric reminder targets stable across fetches

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- Keep numeric reminder indexes stable across reordered EventKit fetches by breaking equal due-date/title sort ties with the reminder ID.
 - Reject impossible ISO dates, malformed offsets, and trailing date text; select explicit field order so day-first inputs cannot silently become another date while retaining unambiguous legacy spellings.
 
 ## 0.3.7 - 2026-09-13

Sources/RemindCore/ReminderFilter.swift

@@ -97,17 +97,21 @@ public enum ReminderFiltering {
     reminders.sorted { lhs, rhs in
       switch (lhs.dueDate, rhs.dueDate) {
       case (nil, nil):
-        return lhs.title < rhs.title
+        break
       case (nil, _?):
         return false
       case (_?, nil):
         return true
       case (let left?, let right?):
-        if left == right {
-          return lhs.title < rhs.title
+        if left != right {
+          return left < right
         }
-        return left < right
       }
+      if lhs.title != rhs.title {
+        return lhs.title < rhs.title
+      }
+      // EventKit fetch order can change between displaying and resolving a numeric index.
+      return lhs.id < rhs.id
     }
   }
 }

Tests/RemindCoreTests/IDResolverTests.swift

@@ -45,6 +45,30 @@ struct IDResolverTests {
     #expect(resolved.first?.title == "Second")
   }
 
+  @Test("Numeric indexes survive reordered fetches with tied sort keys", arguments: [true, false])
+  func stableIndexesWithTiedSortKeys(hasDueDate: Bool) throws {
+    let items = ["aaaa-1111", "bbbb-2222", "cccc-3333"].map { id in
+      ReminderItem(
+        id: id,
+        title: "Pay invoice",
+        notes: nil,
+        isCompleted: false,
+        completionDate: nil,
+        priority: .none,
+        dueDate: hasDueDate ? Date(timeIntervalSince1970: 1_700_000_000) : nil,
+        listID: "synthetic",
+        listName: "Synthetic"
+      )
+    }
+    let displayed = ReminderFiltering.sort(items)
+    let fetched = Array(items.reversed())
+    #expect(ReminderFiltering.sort(fetched).map(\.id) == displayed.map(\.id))
+    for (index, reminder) in displayed.enumerated() {
+      let resolved = try IDResolver.resolve([String(index + 1)], from: fetched, numericFrom: fetched)
+      #expect(resolved.first?.id == reminder.id)
+    }
+  }
+
   @Test("Reject out-of-range indexes without overflow", arguments: [Int.min, -1, 0, 3, Int.max])
   func rejectInvalidIndex(_ index: Int) {
     let input = String(index)

docs/commands.md

@@ -75,6 +75,7 @@ remindctl edit 4A83 --no-repeat
 
 `edit`, `complete`, and `delete` accept indexes from the current default listing or ID prefixes.
 Numeric indexes must be positive and within the current view; out-of-range values return an error.
+Reminders sort by due date, then title, then stable ID so equal dates and titles do not make numeric targets depend on EventKit's fetch order. Use IDs when reminders may be added, removed, or edited between commands.
 
 If `add`, `edit`, or `complete` reports `Reminder is missing a calendar`, EventKit saved the reminder but returned it without its list. Check Reminders.app before retrying; this error does not roll back the saved change.