diff --git a/Strand/BLE/BLEManager.swift b/Strand/BLE/BLEManager.swift
index b9ab47f8d9..c40ff002e0 100644
--- a/Strand/BLE/BLEManager.swift
+++ b/Strand/BLE/BLEManager.swift
@@ -4216,6 +4216,10 @@ extension BLEManager: @preconcurrency CBPeripheralDelegate {
         // revision ever shifts these fields again, the rejection must be visible rather than silent.
         if let pages = DataRange.pagesBehind(from: frame, cmdOff: cmdOff) {
             log("Strap backlog pages behind: \(pages) (#689 — GET_DATA_RANGE ring backlog, diagnostic only)")
+            // #815: confirmed on both WHOOP 4.0 and 5.0/MG, so bank it unconditionally (unlike newest/oldest,
+            // which stay feedsSync-gated to WHOOP4 until a 5/MG capture confirms them too) — the sync chip's
+            // "N pages behind" detail reads this while `backfilling` is true.
+            state.setPagesBehindAtConnect(pages)
         } else {
             log("Strap backlog pages behind: not decodable from this frame (#689 — offsets may have moved; "
                 + "the raw frame above is the input). Diagnostic only, sync is unaffected.")
diff --git a/Strand/BLE/LiveState.swift b/Strand/BLE/LiveState.swift
index 3a59880076..98defe007e 100644
--- a/Strand/BLE/LiveState.swift
+++ b/Strand/BLE/LiveState.swift
@@ -204,6 +204,20 @@ public final class LiveState: ObservableObject {
     /// window can't outlive the link.
     public func clearStrapRange() { strapRange = nil }
 
+    /// #689/#815: the strap's ring-buffer page backlog, sampled ONCE from the connect-time GET_DATA_RANGE
+    /// reply — never re-polled mid-offload (the link is already firmware-paced, ~10 records/s, #377). A
+    /// static "this many pages behind" figure, not a live percentage: the strap never reveals a total
+    /// pending-record count, only this bounded ring-buffer measure (write pointer − read pointer against a
+    /// 131072-page ring), confirmed against real captures on both WHOOP 4.0 and 5.0/MG. The sync chip
+    /// appends it to the chunk count while `backfilling` is true. nil before the first reply this session,
+    /// or if the frame didn't decode. Cleared on disconnect so a stale figure can't outlive the link.
+    @Published public private(set) var pagesBehindAtConnect: Int?
+
+    /// Bank the connect-time GET_DATA_RANGE pages-behind sample (see `pagesBehindAtConnect`).
+    public func setPagesBehindAtConnect(_ pages: Int) {
+        pagesBehindAtConnect = pages
+    }
+
     @Published public var lastFrameType: String? = nil
     @Published public var lastEvent: String? = nil
     /// #987: unix of the most recent strap frame FrameRouter routed. Deliberately NOT @Published - the
@@ -492,6 +506,7 @@ public final class LiveState: ObservableObject {
         recentHrSamples.removeAll()       // Sleep readout buffers must not outlive the link (Group E)
         recentGravitySamples.removeAll()
         clearStrapRange()                 // a stale clock-drift window must not outlive the link either
+        pagesBehindAtConnect = nil        // a stale pages-behind sample must not outlive the link either
         lastFrameAtUnix = nil             // #987: a stale "last frame" freshness must not outlive it either
         ouraWearState = nil               // a stale worn/charging badge must not outlive the link either
         // Perf: flush the durable log tail on disconnect (mirroring is batched in `append`), so a completed
diff --git a/Strand/Liquid/LiquidTodayView.swift b/Strand/Liquid/LiquidTodayView.swift
index 149f27eada..13c472041e 100644
--- a/Strand/Liquid/LiquidTodayView.swift
+++ b/Strand/Liquid/LiquidTodayView.swift
@@ -1949,9 +1949,10 @@ private struct LiquidSyncChip: View {
 
     var body: some View {
         switch SyncChipState.resolve(live: live) {
-        case .syncing(let chunks):
+        case .syncing(let chunks, let pagesBehind):
             pill(system: "arrow.triangle.2.circlepath", text: "\(chunks)",
-                 a11y: String(localized: "Syncing strap history, \(chunks) chunks"))
+                 detail: SyncChipState.pagesBehindDetail(pagesBehind),
+                 a11y: SyncChipState.syncingAccessibilityLabel(chunks: chunks, pagesBehind: pagesBehind))
         case .synced(let agoText):
             pill(system: "checkmark", text: agoText,
                  a11y: String(localized: "Strap history synced \(agoText) ago"))
@@ -1963,10 +1964,14 @@ private struct LiquidSyncChip: View {
         }
     }
 
-    private func pill(system: String, text: String, a11y: String) -> some View {
+    private func pill(system: String, text: String, detail: String? = nil, a11y: String) -> some View {
         HStack(spacing: 4) {
             Image(systemName: system).font(.system(size: 11, weight: .bold))
             Text(text).font(.system(size: 12, weight: .bold))
+            // #689/#815: the pages-behind detail, when known — see `SyncChipState.pagesBehindDetail`.
+            if let detail {
+                Text(detail).font(.system(size: 11, weight: .semibold)).foregroundStyle(.white.opacity(0.7))
+            }
         }
         .foregroundStyle(.white)
         .padding(.horizontal, 10)
diff --git a/Strand/Resources/Localizable.xcstrings b/Strand/Resources/Localizable.xcstrings
index 3ce58af975..783d77a775 100644
--- a/Strand/Resources/Localizable.xcstrings
+++ b/Strand/Resources/Localizable.xcstrings
@@ -169628,6 +169628,110 @@
           }
         }
       }
+    },
+    "%lld pages behind": {
+      "localizations": {
+        "de": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld Seiten im Rückstand"
+          }
+        },
+        "es": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld páginas de retraso"
+          }
+        },
+        "fr": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld pages de retard"
+          }
+        },
+        "it": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld pagine di ritardo"
+          }
+        },
+        "pt-PT": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld páginas em atraso"
+          }
+        },
+        "ru": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "%lld страниц позади"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "落后 %lld 页"
+          }
+        },
+        "zh-Hant": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "落後 %lld 頁"
+          }
+        }
+      }
+    },
+    "Syncing strap history, %lld chunks, %lld pages behind": {
+      "localizations": {
+        "de": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Verlaufssynchronisierung des Straps läuft, %lld Chunks, %lld Seiten im Rückstand"
+          }
+        },
+        "es": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Sincronizando el historial de la pulsera, %lld bloques, %lld páginas de retraso"
+          }
+        },
+        "fr": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Synchronisation de l'historique du bracelet, %lld blocs, %lld pages de retard"
+          }
+        },
+        "it": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Sincronizzazione della cronologia della fascia, %lld blocchi, %lld pagine di ritardo"
+          }
+        },
+        "pt-PT": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "A sincronizar o histórico da bracelete, %lld pedaços, %lld páginas em atraso"
+          }
+        },
+        "ru": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "Синхронизация истории браслета, %lld фрагментов, %lld страниц позади"
+          }
+        },
+        "zh-Hans": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "正在同步手环历史记录，%lld 个数据块，落后 %lld 页"
+          }
+        },
+        "zh-Hant": {
+          "stringUnit": {
+            "state": "translated",
+            "value": "正在同步手環歷史記錄，%lld 個資料塊，落後 %lld 頁"
+          }
+        }
+      }
     }
   },
   "version": "1.0"
diff --git a/Strand/Screens/TodayView.swift b/Strand/Screens/TodayView.swift
index a5443e8446..4f12717e82 100644
--- a/Strand/Screens/TodayView.swift
+++ b/Strand/Screens/TodayView.swift
@@ -4467,14 +4467,20 @@ struct TodayDayScopedCache {
 /// yet) → `✓ live`. `.hidden` only on a true cold start (the building-scores note owns that case). Twin
 /// of Android `SyncStatusChip`.
 enum SyncChipState: Equatable {
-    case syncing(chunks: Int)
+    /// #689/#815 follow-up: `pagesBehind` is the strap's GET_DATA_RANGE ring backlog sampled once at
+    /// connect (`LiveState.pagesBehindAtConnect`) — nil until a reply has landed this session, or on a
+    /// device/frame where it didn't decode. Purely additive: nil renders identically to before this field
+    /// existed, so it defaults to the chunk-count-only chip.
+    case syncing(chunks: Int, pagesBehind: Int? = nil)
     case synced(agoText: String)
     case experimentalLive
     case hidden
 
     @MainActor
     static func resolve(live: LiveState) -> SyncChipState {
-        if live.backfilling { return .syncing(chunks: live.syncChunksThisSession) }
+        if live.backfilling {
+            return .syncing(chunks: live.syncChunksThisSession, pagesBehind: live.pagesBehindAtConnect)
+        }
         if let ts = live.lastSyncedAt { return .synced(agoText: shortAgo(ts)) }
         if live.historySyncExperimental { return .experimentalLive }
         return .hidden
@@ -4492,6 +4498,24 @@ enum SyncChipState: Equatable {
         if hrs < 24 { return "\(hrs)h" }
         return "\(hrs / 24)d"
     }
+
+    /// The small trailing fragment the syncing chip appends beside the chunk count when a pages-behind
+    /// sample is known — "494 pages behind". nil (no fragment) when the sample hasn't landed yet, which
+    /// is exactly today's chunk-count-only rendering. Shared by `SyncStatusChip` and `LiquidSyncChip` so
+    /// the two headers can't word this differently.
+    static func pagesBehindDetail(_ pagesBehind: Int?) -> String? {
+        pagesBehind.map { String(localized: "\($0) pages behind") }
+    }
+
+    /// VoiceOver label for the syncing state. Extends the existing chunk-count sentence with the
+    /// pages-behind figure when known, so the detail reaches accessibility users the same way it reaches
+    /// sighted ones via `pagesBehindDetail`, rather than being a sighted-only visual fragment.
+    static func syncingAccessibilityLabel(chunks: Int, pagesBehind: Int?) -> String {
+        if let pagesBehind {
+            return String(localized: "Syncing strap history, \(chunks) chunks, \(pagesBehind) pages behind")
+        }
+        return String(localized: "Syncing strap history, \(chunks) chunks")
+    }
 }
 
 /// #245: a compact sync-status chip for the Today top bar, shown to EVERY user. The full-width
@@ -4504,9 +4528,10 @@ struct SyncStatusChip: View {
 
     var body: some View {
         switch SyncChipState.resolve(live: live) {
-        case .syncing(let chunks):
-            chip(system: "arrow.triangle.2.circlepath", text: "\(chunks)", tint: StrandPalette.accent,
-                 a11y: String(localized: "Syncing strap history, \(chunks) chunks"))
+        case .syncing(let chunks, let pagesBehind):
+            chip(system: "arrow.triangle.2.circlepath", text: "\(chunks)",
+                 detail: SyncChipState.pagesBehindDetail(pagesBehind), tint: StrandPalette.accent,
+                 a11y: SyncChipState.syncingAccessibilityLabel(chunks: chunks, pagesBehind: pagesBehind))
         case .synced(let agoText):
             chip(system: "checkmark", text: agoText, tint: StrandPalette.textSecondary,
                  a11y: String(localized: "Strap history synced \(agoText) ago"))
@@ -4519,10 +4544,15 @@ struct SyncStatusChip: View {
         }
     }
 
-    private func chip(system: String, text: String, tint: Color, a11y: String) -> some View {
+    private func chip(system: String, text: String, detail: String? = nil, tint: Color, a11y: String) -> some View {
         HStack(spacing: 4) {
             Image(systemName: system).font(.system(size: 11, weight: .semibold))
             Text(text).font(StrandFont.captionNumber)
+            // #689/#815: the pages-behind detail, when known. A trailing fragment rather than a redesign
+            // of this DRAFT chip — see `SyncChipState.pagesBehindDetail`.
+            if let detail {
+                Text(detail).font(StrandFont.caption).foregroundStyle(tint.opacity(0.7))
+            }
         }
         .foregroundStyle(tint)
         .padding(.horizontal, 8)
diff --git a/StrandTests/SyncChipStateTests.swift b/StrandTests/SyncChipStateTests.swift
index feb7ddda9d..b745938b9a 100644
--- a/StrandTests/SyncChipStateTests.swift
+++ b/StrandTests/SyncChipStateTests.swift
@@ -12,7 +12,17 @@ final class SyncChipStateTests: XCTestCase {
         let live = LiveState()
         live.backfilling = true
         live.syncChunksThisSession = 7
-        XCTAssertEqual(SyncChipState.resolve(live: live), .syncing(chunks: 7))
+        XCTAssertEqual(SyncChipState.resolve(live: live), .syncing(chunks: 7, pagesBehind: nil))
+    }
+
+    /// #689/#815 follow-up: when a GET_DATA_RANGE sample has landed this session, it rides along on the
+    /// syncing state so the chip can append the "N pages behind" detail.
+    func testBackfilling_withPagesBehindSample_carriesItOnSyncingState() {
+        let live = LiveState()
+        live.backfilling = true
+        live.syncChunksThisSession = 7
+        live.setPagesBehindAtConnect(494)
+        XCTAssertEqual(SyncChipState.resolve(live: live), .syncing(chunks: 7, pagesBehind: 494))
     }
 
     func testLastSyncedAt_isSyncedWithAgeText() {
diff --git a/android/app/src/main/java/com/noop/ble/WhoopBleClient.kt b/android/app/src/main/java/com/noop/ble/WhoopBleClient.kt
index 5e3d010e67..8eb6d225c6 100644
--- a/android/app/src/main/java/com/noop/ble/WhoopBleClient.kt
+++ b/android/app/src/main/java/com/noop/ble/WhoopBleClient.kt
@@ -208,6 +208,14 @@ data class LiveState(
      *  once empty offloads are SUSTAINED; cleared on connect or once the strap banks real records. Twin of
      *  macOS LiveState.historySyncExperimental. */
     val historySyncExperimental: Boolean = false,
+    /** #689/#815: the strap's ring-buffer page backlog, sampled ONCE from the connect-time GET_DATA_RANGE
+     *  reply — never re-polled mid-offload (the link is already firmware-paced, ~10 records/s). A static
+     *  "pages behind" figure, not a live percentage: the strap never reveals a total record count, only
+     *  this bounded ring-buffer measure (write pointer − read pointer against a 131072-page ring),
+     *  confirmed against real captures on both WHOOP 4.0 and 5.0/MG. The Today sync chip appends it to
+     *  the chunk count while [backfilling] is true. null before the first reply this session, or if the
+     *  frame didn't decode. Twin of macOS LiveState.pagesBehindAtConnect. */
+    val pagesBehindAtConnect: Int? = null,
 ) {
     /** Set the fresh-packet [rr] AND append the valid intervals onto the bounded [rrRecent] rolling
      *  buffer (oldest fall off first). Non-positive sentinels are dropped from the rolling buffer.
@@ -973,6 +981,8 @@ class WhoopBleClient(
                 // #580: the 5/MG "history experimental" note is per-link — a fresh connect re-derives it
                 // from the next offload, so it must not outlive the dropped link.
                 historySyncExperimental = false,
+                // A stale pages-behind sample must not outlive the dropped link either (#689/#815).
+                pagesBehindAtConnect = null,
             )
 
         /**
@@ -4484,6 +4494,9 @@ class WhoopBleClient(
                         val pagesBehind = com.noop.protocol.DataRange.pagesBehind(frame, cmdOff)
                         if (pagesBehind != null) {
                             log("Strap backlog pages behind: $pagesBehind (#689 — GET_DATA_RANGE ring backlog, diagnostic only)")
+                            // #815: confirmed on both WHOOP 4.0 and 5.0/MG, so bank it unconditionally — the
+                            // Today sync chip's "N pages behind" detail reads this while backfilling is true.
+                            _state.update { it.copy(pagesBehindAtConnect = pagesBehind.toInt()) }
                         } else {
                             log(
                                 "Strap backlog pages behind: not decodable from this frame (#689 — offsets may " +
diff --git a/android/app/src/main/java/com/noop/ui/TodayScoring.kt b/android/app/src/main/java/com/noop/ui/TodayScoring.kt
index afd0a85da6..1c003d0bb8 100644
--- a/android/app/src/main/java/com/noop/ui/TodayScoring.kt
+++ b/android/app/src/main/java/com/noop/ui/TodayScoring.kt
@@ -381,7 +381,11 @@ internal fun recordingStateFor(
  *  [Hidden] only on a true cold start (the building-scores note owns that case). Previously this
  *  priority order lived inline inside the `@Composable`, where it could not be unit-tested. */
 sealed class SyncChipState {
-    data class Syncing(val chunks: Int) : SyncChipState()
+    /** #689/#815 follow-up: [pagesBehind] is the strap's GET_DATA_RANGE ring backlog sampled once at
+     *  connect (`LiveState.pagesBehindAtConnect`) — null until a reply has landed this session, or on a
+     *  device/frame where it didn't decode. Purely additive: null renders identically to before this
+     *  field existed, so it defaults to the chunk-count-only chip. Mirrors Swift `SyncChipState.syncing`. */
+    data class Syncing(val chunks: Int, val pagesBehind: Int? = null) : SyncChipState()
     data class Synced(val agoText: String) : SyncChipState()
     object ExperimentalLive : SyncChipState()
     object Hidden : SyncChipState()
@@ -394,8 +398,9 @@ sealed class SyncChipState {
             chunks: Int,
             lastSyncAtSec: Long?,
             historySyncExperimental: Boolean,
+            pagesBehind: Int? = null,
         ): SyncChipState = when {
-            backfilling -> Syncing(chunks)
+            backfilling -> Syncing(chunks, pagesBehind)
             lastSyncAtSec != null -> Synced(shortSyncAgo(lastSyncAtSec))
             historySyncExperimental -> ExperimentalLive
             else -> Hidden
@@ -416,6 +421,21 @@ internal fun shortSyncAgo(unixSec: Long): String {
     }
 }
 
+/** #689/#815 follow-up: the small trailing fragment the syncing chip appends beside the chunk count when
+ *  a pages-behind sample is known — "494 pages behind". null (no fragment) when the sample hasn't landed
+ *  yet, which is exactly today's chunk-count-only rendering. Mirrors iOS `SyncChipState.pagesBehindDetail`. */
+internal fun pagesBehindDetail(pagesBehind: Int?): String? =
+    pagesBehind?.let { uiString(R.string.l10n_today_screen_sync_chip_pages_behind_29b5c548, it) }
+
+/** Accessibility/content-description label for the syncing state. Extends the existing chunk-count
+ *  sentence with the pages-behind figure when known. Mirrors iOS `SyncChipState.syncingAccessibilityLabel`. */
+internal fun syncingAccessibilityLabel(chunks: Int, pagesBehind: Int?): String =
+    if (pagesBehind != null) {
+        uiString(R.string.l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9, chunks, pagesBehind)
+    } else {
+        uiString(R.string.l10n_today_screen_sync_chip_syncing_desc_bfc290e7, chunks)
+    }
+
 /** Whether this night's sleep staging is low-confidence, using the core [ScoreConfidence] rule. */
 internal fun restStageLowConfidence(d: DailyMetric?): Boolean {
     val asleepMin = d?.totalSleepMin ?: return false
diff --git a/android/app/src/main/java/com/noop/ui/TodayScreen.kt b/android/app/src/main/java/com/noop/ui/TodayScreen.kt
index 9e14e2c345..2c93957c09 100644
--- a/android/app/src/main/java/com/noop/ui/TodayScreen.kt
+++ b/android/app/src/main/java/com/noop/ui/TodayScreen.kt
@@ -236,6 +236,9 @@ private data class TodayLiveSnapshot(
     val whoop5: Boolean,
     /** Charging hides the runtime estimate (no "X left" while topping up). Rare flips, snapshot-safe. */
     val charging: Boolean?,
+    /** #689/#815 follow-up: the connect-time GET_DATA_RANGE pages-behind sample, when known. Set once per
+     *  connection, so it doesn't reintroduce per-tick churn either. */
+    val pagesBehindAtConnect: Int?,
 )
 
 @OptIn(ExperimentalMaterial3Api::class)
@@ -302,6 +305,7 @@ fun TodayScreen(
                 batteryPct = s.batteryPct,
                 whoop5 = s.whoop5Detected,
                 charging = s.charging,
+                pagesBehindAtConnect = s.pagesBehindAtConnect,
             )
         }
     }
@@ -1169,6 +1173,7 @@ fun TodayScreen(
                 syncChunksThisSession = liveSnap.syncChunksThisSession,
                 lastSyncAt = liveSnap.lastSyncAt,
                 historySyncExperimental = liveSnap.historySyncExperimental,
+                pagesBehindAtConnect = liveSnap.pagesBehindAtConnect,
                 onPickDay = { offset -> selectedDayOffset = offset },
                 onQuickActions = onQuickActions,
                 onOpenSettings = onOpenSettings,
@@ -2004,6 +2009,8 @@ private fun LiquidTodayHeader(
     syncChunksThisSession: Int = 0,
     lastSyncAt: Long? = null,
     historySyncExperimental: Boolean = false,
+    // #689/#815 follow-up: the connect-time GET_DATA_RANGE pages-behind sample, when known.
+    pagesBehindAtConnect: Int? = null,
     onPickDay: (Int) -> Unit,
     onQuickActions: () -> Unit,
     onOpenSettings: () -> Unit,
@@ -2093,6 +2100,7 @@ private fun LiquidTodayHeader(
             SyncStatusChip(
                 backfilling = backfilling, chunks = syncChunksThisSession,
                 lastSyncAt = lastSyncAt, historySyncExperimental = historySyncExperimental,
+                pagesBehind = pagesBehindAtConnect,
             )
             // (a) Profile avatar (the photo set in Settings, or the NOOP loop mark) → Settings. Mirrors iOS.
             Box(
@@ -2131,11 +2139,13 @@ private fun SyncStatusChip(
     chunks: Int,
     lastSyncAt: Long?,
     historySyncExperimental: Boolean,
+    pagesBehind: Int? = null,
 ) {
-    when (val state = SyncChipState.resolve(backfilling, chunks, lastSyncAt, historySyncExperimental)) {
+    when (val state = SyncChipState.resolve(backfilling, chunks, lastSyncAt, historySyncExperimental, pagesBehind)) {
         is SyncChipState.Syncing -> ChipCapsule(
             Icons.Filled.Autorenew, "${state.chunks}", Palette.accent,
-            uiString(R.string.l10n_today_screen_sync_chip_syncing_desc_bfc290e7, state.chunks))
+            syncingAccessibilityLabel(state.chunks, state.pagesBehind),
+            detail = pagesBehindDetail(state.pagesBehind))
         is SyncChipState.Synced -> ChipCapsule(
             Icons.Filled.Check, state.agoText, Palette.textSecondary,
             uiString(R.string.l10n_today_screen_sync_chip_synced_desc_4d255944, state.agoText))
@@ -2147,9 +2157,11 @@ private fun SyncStatusChip(
     }
 }
 
-/** The shared sync-chip capsule (icon + terse label). Twin of the iOS `SyncStatusChip.chip`. */
+/** The shared sync-chip capsule (icon + terse label). Twin of the iOS `SyncStatusChip.chip`.
+ *  #689/#815: [detail] is the pages-behind fragment appended beside [text], when known —
+ *  see [pagesBehindDetail]. */
 @Composable
-private fun ChipCapsule(icon: ImageVector, text: String, tint: Color, desc: String) {
+private fun ChipCapsule(icon: ImageVector, text: String, tint: Color, desc: String, detail: String? = null) {
     Row(
         verticalAlignment = Alignment.CenterVertically,
         horizontalArrangement = Arrangement.spacedBy(4.dp),
@@ -2160,6 +2172,9 @@ private fun ChipCapsule(icon: ImageVector, text: String, tint: Color, desc: Stri
     ) {
         Icon(icon, contentDescription = desc, tint = tint, modifier = Modifier.size(14.dp))
         Text(text, style = NoopType.caption, color = tint)
+        if (detail != null) {
+            Text(detail, style = NoopType.caption, color = tint.copy(alpha = 0.7f))
+        }
     }
 }
 
diff --git a/android/app/src/main/res/values-de/strings.xml b/android/app/src/main/res/values-de/strings.xml
index a6f1e67041..d0dd7f6ce6 100644
--- a/android/app/src/main/res/values-de/strings.xml
+++ b/android/app/src/main/res/values-de/strings.xml
@@ -1599,6 +1599,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">jetzt</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">Live</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">Verlaufssynchronisierung des Straps läuft, %1$d Chunks</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">%1$d Seiten im Rückstand</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">Verlaufssynchronisierung des Straps läuft, %1$d Chunks, %2$d Seiten im Rückstand</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">Verlauf des Straps vor %1$s synchronisiert</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">Verbunden; die Verlaufssynchronisierung ist bei diesem Strap experimentell.</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">%1$s%% Ladung</string>
diff --git a/android/app/src/main/res/values-es/strings.xml b/android/app/src/main/res/values-es/strings.xml
index 1806b129ed..d25c936417 100644
--- a/android/app/src/main/res/values-es/strings.xml
+++ b/android/app/src/main/res/values-es/strings.xml
@@ -1439,6 +1439,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">ahora</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">en vivo</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">Sincronizando el historial de la pulsera, %1$d bloques</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">%1$d páginas de retraso</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">Sincronizando el historial de la pulsera, %1$d bloques, %2$d páginas de retraso</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">Historial de la pulsera sincronizado hace %1$s</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">Conectado; la sincronización del historial es experimental en esta pulsera.</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">%1$s%%</string>
diff --git a/android/app/src/main/res/values-fr/strings.xml b/android/app/src/main/res/values-fr/strings.xml
index e9245e1d6d..8e6a3bb2df 100644
--- a/android/app/src/main/res/values-fr/strings.xml
+++ b/android/app/src/main/res/values-fr/strings.xml
@@ -1439,6 +1439,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">à l\'instant</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">en direct</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">Synchronisation de l\'historique du bracelet, %1$d blocs</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">%1$d pages de retard</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">Synchronisation de l\'historique du bracelet, %1$d blocs, %2$d pages de retard</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">Historique du bracelet synchronisé il y a %1$s</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">Connecté ; la synchronisation de l\'historique est expérimentale sur ce bracelet.</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">Charge %1$s%%</string>
diff --git a/android/app/src/main/res/values-pt-rPT/strings.xml b/android/app/src/main/res/values-pt-rPT/strings.xml
index 4e77b8073e..b7284bf307 100644
--- a/android/app/src/main/res/values-pt-rPT/strings.xml
+++ b/android/app/src/main/res/values-pt-rPT/strings.xml
@@ -1580,6 +1580,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">agora</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">em direto</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">A sincronizar o histórico da bracelete, %1$d pedaços</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">%1$d páginas em atraso</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">A sincronizar o histórico da bracelete, %1$d pedaços, %2$d páginas em atraso</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">Histórico da bracelete sincronizado há %1$s</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">Ligada; a sincronização do histórico é experimental nesta bracelete.</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">%1$s%% Carga</string>
diff --git a/android/app/src/main/res/values-zh/strings.xml b/android/app/src/main/res/values-zh/strings.xml
index 852bb310e1..80dfb20c10 100644
--- a/android/app/src/main/res/values-zh/strings.xml
+++ b/android/app/src/main/res/values-zh/strings.xml
@@ -1561,6 +1561,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">刚刚</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">实时</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">正在同步腕带历史记录，%1$d 个数据块</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">落后 %1$d 页</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">正在同步腕带历史记录，%1$d 个数据块，落后 %2$d 页</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">手环历史记录已在 %1$s 前同步</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">已连接；此手环的历史同步功能为实验性功能。</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">%1$s%% 充能(Charge)</string>
diff --git a/android/app/src/main/res/values/strings.xml b/android/app/src/main/res/values/strings.xml
index 14389cc086..45034385a0 100644
--- a/android/app/src/main/res/values/strings.xml
+++ b/android/app/src/main/res/values/strings.xml
@@ -1608,6 +1608,8 @@
     <string name="l10n_today_screen_sync_chip_now_c9bc849a">now</string>
     <string name="l10n_today_screen_sync_chip_live_98aadb37">live</string>
     <string name="l10n_today_screen_sync_chip_syncing_desc_bfc290e7">Syncing strap history, %1$d chunks</string>
+    <string name="l10n_today_screen_sync_chip_pages_behind_29b5c548">%1$d pages behind</string>
+    <string name="l10n_today_screen_sync_chip_syncing_pages_desc_6c2a5ea9">Syncing strap history, %1$d chunks, %2$d pages behind</string>
     <string name="l10n_today_screen_sync_chip_synced_desc_4d255944">Strap history synced %1$s ago</string>
     <string name="l10n_today_screen_sync_chip_experimental_desc_3de06a70">Connected; strap history sync is experimental on this strap</string>
     <string name="l10n_today_screen_recovery_roundtoint_charge_92fbaa5e">%1$s%% Charge</string>
diff --git a/android/app/src/test/java/com/noop/ble/GattCrashSafetyTest.kt b/android/app/src/test/java/com/noop/ble/GattCrashSafetyTest.kt
index dd6e97a8e4..cd49c0f910 100644
--- a/android/app/src/test/java/com/noop/ble/GattCrashSafetyTest.kt
+++ b/android/app/src/test/java/com/noop/ble/GattCrashSafetyTest.kt
@@ -82,6 +82,7 @@ class GattCrashSafetyTest {
             historyLayoutVersion = 25,
             backfilling = true,
             syncChunksThisSession = 12,
+            pagesBehindAtConnect = 494,
         )
 
         val after = WhoopBleClient.disconnectedLiveState(live)
@@ -100,6 +101,8 @@ class GattCrashSafetyTest {
         // A stale charging flag must not outlive the link.
         assertNull(after.charging)
         assertNull(after.strapFirmware)
+        // A stale pages-behind sample must not outlive the dropped link either (#689/#815).
+        assertNull(after.pagesBehindAtConnect)
         assertNull(after.historyLayoutVersion)
     }
 
diff --git a/android/app/src/test/java/com/noop/ui/SyncChipStateTest.kt b/android/app/src/test/java/com/noop/ui/SyncChipStateTest.kt
index aef8fd9622..0c029abb6d 100644
--- a/android/app/src/test/java/com/noop/ui/SyncChipStateTest.kt
+++ b/android/app/src/test/java/com/noop/ui/SyncChipStateTest.kt
@@ -16,7 +16,18 @@ class SyncChipStateTest {
         val state = SyncChipState.resolve(
             backfilling = true, chunks = 7, lastSyncAtSec = null, historySyncExperimental = false,
         )
-        assertEquals(SyncChipState.Syncing(7), state)
+        assertEquals(SyncChipState.Syncing(7, null), state)
+    }
+
+    /** #689/#815 follow-up: when a GET_DATA_RANGE sample has landed this session, it rides along on the
+     *  syncing state so the chip can append the "N pages behind" detail. */
+    @Test
+    fun backfilling_withPagesBehindSample_carriesItOnSyncingState() {
+        val state = SyncChipState.resolve(
+            backfilling = true, chunks = 7, lastSyncAtSec = null, historySyncExperimental = false,
+            pagesBehind = 494,
+        )
+        assertEquals(SyncChipState.Syncing(7, 494), state)
     }
 
     @Test