Trends: price-history fetch failure with no data raises the connection banner

A history fetch that comes back empty BECAUSE the mirror is unreachable
(pointer probe failed) was only an in-sheet retry card — no global signal.
Now it also raises the red connection banner ('Check your internet
connection / Tap to try again'), so a network problem is visible on every
tab, not just inside the Trends sheet. A successful load clears the
banner (only when the banner is the connection banner — never clobbers
the offline-dump banner).

- TrendsView: onHistoryUnavailable/onHistoryRecovered closures fired from
  load() (loadFailed -> unavailable; hasAnyData -> recovered);
  -forceHistoryFailure QA hook (forces the unreachable state, skips
  auto-refresh like the other force-* hooks)
- FavouritesView: closures threaded through the Trends sheet init
- ContentView: wires them to dataStatus (.live -> .connectionProblem on
  failure; recovered clears only .connectionProblem)
- fuelboard-development skill: hook + wiring documented

FuelBoard/BundledDumpProvider.swift

@@ -15,4 +15,14 @@ enum BundledDumpProvider {
         guard let asset = NSDataAsset(name: "FuelBoardDump") else { return nil }
         return try? FuelPriceProvider.decodeStations(from: asset.data)
     }
+
+    /// The GOV.UK `data_updated` stamp from the bundled envelope (ISO 8601).
+    /// Labels the offline-data banner honestly ("Offline data from 15 Aug")
+    /// instead of presenting the build's snapshot as live.
+    static var dataUpdatedStamp: String? {
+        guard let asset = NSDataAsset(name: "FuelBoardDump"),
+              let obj = try? JSONSerialization.jsonObject(with: asset.data)
+                  as? [String: Any] else { return nil }
+        return obj["data_updated"] as? String
+    }
 }

FuelBoard/ContentView.swift

@@ -32,6 +32,19 @@ struct ContentView: View {
     }
     @State private var isLoading = false
     @State private var statusMessage = ""
+    /// What data is on screen, driving which (if any) status banner shows
+    /// above the tabs:
+    ///  - `.live`: fetched or cached data — nothing to say.
+    ///  - `.offlineDump(date)`: serving the BUNDLED no-network snapshot —
+    ///    the banner labels it honestly with the snapshot's own date.
+    ///  - `.connectionProblem`: fetch failed but a saved cache is showing —
+    ///    the banner says to check connectivity (tap = retry).
+    enum DataSourceStatus: Equatable {
+        case live
+        case offlineDump(date: String)
+        case connectionProblem
+    }
+    @State private var dataStatus: DataSourceStatus = .live
     @State private var showOnboarding = false
     @State private var showWidgetMock = false
     @State private var selectedTab = 0
@@ -139,7 +152,31 @@ struct ContentView: View {
     }
 
     var body: some View {
-        TabView(selection: $selectedTab) {
+        VStack(spacing: 0) {
+            switch dataStatus {
+            case .offlineDump(let date):
+                let title = offlineTitle(date: date)
+                statusBanner(
+                    icon: "wifi.slash",
+                    tint: .orange,
+                    title: title,
+                    subtitle: NSLocalizedString("Pull to refresh on the Stations tab", comment: ""),
+                    accessibilityLabel: date.isEmpty
+                        ? NSLocalizedString("Offline data. Pull to refresh on the Stations tab", comment: "")
+                        : String(format: NSLocalizedString("Offline data from %@. Pull to refresh on the Stations tab", comment: ""), date)
+                )
+            case .connectionProblem:
+                statusBanner(
+                    icon: "wifi.exclamationmark",
+                    tint: .red,
+                    title: NSLocalizedString("Check your internet connection", comment: ""),
+                    subtitle: NSLocalizedString("Tap to try again", comment: ""),
+                    accessibilityLabel: NSLocalizedString("Check your internet connection. Tap to try again", comment: "")
+                )
+            case .live:
+                EmptyView()
+            }
+            TabView(selection: $selectedTab) {
             stationsTab
                 .tabItem { Label("Stations", systemImage: "fuelpump.fill") }
                 .tag(0)
@@ -204,6 +241,19 @@ struct ContentView: View {
                 default: selectedTab = 0
                 }
             }
+            // `-forceOfflineDump` / `-forceConnectionProblem` simulate the two
+            // failure legs for the screenshot harness. The auto-refresh below
+            // is skipped so the banner stays up (a live fetch would clear it).
+            if args.contains("-forceOfflineDump") {
+                stations = BundledDumpProvider.stations ?? SampleFuelProvider.sampleStations
+                dataStatus = .offlineDump(date: FuelStore.offlineDataLabel(from: BundledDumpProvider.dataUpdatedStamp) ?? "")
+            }
+            if args.contains("-forceConnectionProblem") {
+                stations = FuelStore.loadStations().isEmpty
+                    ? (BundledDumpProvider.stations ?? SampleFuelProvider.sampleStations)
+                    : FuelStore.loadStations()
+                dataStatus = .connectionProblem
+            }
             // Onboarding runs first on a fresh install — it owns the initial
             // permission prompts (location, notifications, and the data/local
             // network probe on the Data page). Location tracking and the first
@@ -233,7 +283,10 @@ struct ContentView: View {
                 monitor.setEnabled(alertsEnabled)
                 updateLiveActivity()
                 // Refresh only when the cache is stale (twice-a-day policy).
-                Task { await refresh() }
+                // Skipped under the force-* hooks so the banner stays up.
+                if !args.contains("-forceOfflineDump") && !args.contains("-forceConnectionProblem") && !args.contains("-forceHistoryFailure") {
+                    Task { await refresh() }
+                }
             } else {
                 showOnboarding = true
             }
@@ -367,6 +420,59 @@ struct ContentView: View {
             // so reading storage here could push the OLD style.
             updateLiveActivity(priceDisplayStyleOverride: newValue)
         }
+        }  // VStack: status banner + TabView
+        .animation(.spring(response: 0.3, dampingFraction: 0.8), value: dataStatus)
+    }
+
+    /// The banner title for the bundled-snapshot case: date when the stamp
+    /// parsed, plain "Offline data" otherwise.
+    private func offlineTitle(date: String) -> String {
+        date.isEmpty
+            ? NSLocalizedString("Offline data", comment: "")
+            : String(format: NSLocalizedString("Offline data from %@", comment: ""), date)
+    }
+
+    /// Shared status-strip chrome: a tappable card pinned above the tabs.
+    /// Tapping retries the live fetch from ANY screen — no pull gesture
+    /// needed, so the offline banner isn't trapped on the Stations tab.
+    private func statusBanner(icon: String, tint: Color, title: String, subtitle: String, accessibilityLabel: String) -> some View {
+        Button {
+            Task { await refresh(force: true) }
+        } label: {
+            HStack(spacing: 10) {
+                Image(systemName: icon)
+                    .font(.system(size: 17, weight: .semibold))
+                    .foregroundStyle(tint)
+                    .frame(width: 30)
+                VStack(alignment: .leading, spacing: 2) {
+                    Text(title)
+                        .font(.subheadline.weight(.semibold))
+                        .foregroundStyle(.primary)
+                    Text(subtitle)
+                        .font(.caption)
+                        .foregroundStyle(.secondary)
+                }
+                Spacer()
+                Image(systemName: "arrow.clockwise")
+                    .font(.system(size: 14, weight: .semibold))
+                    .foregroundStyle(tint)
+            }
+            .padding(.horizontal, 14)
+            .padding(.vertical, 10)
+            .background(
+                RoundedRectangle(cornerRadius: 12, style: .continuous)
+                    .fill(Color(.secondarySystemGroupedBackground))
+                    .overlay(
+                        RoundedRectangle(cornerRadius: 12, style: .continuous)
+                            .stroke(tint.opacity(0.35), lineWidth: 1)
+                    )
+            )
+            .padding(.horizontal, 12)
+            .padding(.bottom, 6)
+        }
+        .buttonStyle(.plain)
+        .accessibilityLabel(accessibilityLabel)
+        .transition(.move(edge: .top).combined(with: .opacity))
     }
 
     /// Pushes the current best-in-radius station into the Live Activity.
@@ -420,7 +526,9 @@ struct ContentView: View {
             distanceUnit: distanceUnit,
             priceDisplayStyle: priceDisplayStyle,
             onToggleFavourite: toggleFavourite,
-            onReorder: reorderFavourites
+            onReorder: reorderFavourites,
+            onHistoryUnavailable: { if dataStatus == .live { dataStatus = .connectionProblem } },
+            onHistoryRecovered: { if dataStatus == .connectionProblem { dataStatus = .live } }
         )
     }
 
@@ -504,14 +612,26 @@ struct ContentView: View {
             FuelStore.saveFavourites(refreshedFavourites)
             WidgetCenter.shared.reloadAllTimelines()
             statusMessage = "Loaded \(fetched.count) stations · \(Date().formatted(date: .omitted, time: .shortened))"
+            // Live data restored — any status banner no longer applies.
+            dataStatus = .live
         } catch {
             statusMessage = "Live fetch failed: \(error.localizedDescription). Showing cached data."
             if FuelStore.loadStations().isEmpty {
                 // No cached prices — last resort is the bundled REAL dump
-                // (stale but genuine), then the demo sample set.
-                stations = BundledDumpProvider.stations ?? SampleFuelProvider.sampleStations
+                // (stale but genuine), then the demo sample set. The banner
+                // labels the bundled snapshot honestly with its own date.
+                if let dump = BundledDumpProvider.stations {
+                    stations = dump
+                    dataStatus = .offlineDump(date: FuelStore.offlineDataLabel(from: BundledDumpProvider.dataUpdatedStamp) ?? "")
+                } else {
+                    stations = SampleFuelProvider.sampleStations
+                    dataStatus = .live
+                }
             } else {
+                // Saved prices are still on screen — but the fetch failed, so
+                // say so: a stale cache must not look like a live app.
                 stations = FuelStore.loadStations()
+                dataStatus = .connectionProblem
             }
         }
         // Keep monitor geofences in sync with the freshest data.

FuelBoard/FavouritesView.swift

@@ -17,6 +17,10 @@ struct FavouritesView: View {
     var onToggleFavourite: (FuelStation, FuelType) -> Void = { _, _ in }
     /// Persists a reordered favourites array (after drag-and-drop).
     var onReorder: ([FavouriteEntry]) -> Void = { _ in }
+    /// Propagated from ContentView — Trends' history failure with no data
+    /// raises the global connection banner; recovery clears it.
+    var onHistoryUnavailable: (() -> Void)? = nil
+    var onHistoryRecovered: (() -> Void)? = nil
 
     /// Fuel types that currently have at least one favourite — these are the
     /// only tabs shown (a fuel with no favourites gets no tab).
@@ -62,7 +66,9 @@ struct FavouritesView: View {
          distanceUnit: DistanceUnit,
          priceDisplayStyle: PriceDisplayStyle,
          onToggleFavourite: @escaping (FuelStation, FuelType) -> Void = { _, _ in },
-         onReorder: @escaping ([FavouriteEntry]) -> Void = { _ in }) {
+         onReorder: @escaping ([FavouriteEntry]) -> Void = { _ in },
+         onHistoryUnavailable: (() -> Void)? = nil,
+         onHistoryRecovered: (() -> Void)? = nil) {
         self.favourites = favourites
         self.selectedFuel = selectedFuel
         self.location = location
@@ -70,6 +76,8 @@ struct FavouritesView: View {
         self.priceDisplayStyle = priceDisplayStyle
         self.onToggleFavourite = onToggleFavourite
         self.onReorder = onReorder
+        self.onHistoryUnavailable = onHistoryUnavailable
+        self.onHistoryRecovered = onHistoryRecovered
         _fuel = State(initialValue: selectedFuel)
     }
 
@@ -158,7 +166,9 @@ struct FavouritesView: View {
                 TrendsView(
                     favourites: favourites,
                     selectedFuel: activeFuel,
-                    priceDisplayStyle: priceDisplayStyle
+                    priceDisplayStyle: priceDisplayStyle,
+                    onHistoryUnavailable: onHistoryUnavailable,
+                    onHistoryRecovered: onHistoryRecovered
                 )
             }
             .onAppear {

FuelBoard/TrendsView.swift

@@ -16,6 +16,12 @@ struct TrendsView: View {
     let selectedFuel: FuelType
     let priceDisplayStyle: PriceDisplayStyle
 
+    /// Propagated up to ContentView so a price-history fetch that fails with
+    /// NO data raises the global connection banner (same red banner as the
+    /// stations fetch). `onHistoryRecovered` fires once data loads again.
+    var onHistoryUnavailable: (() -> Void)? = nil
+    var onHistoryRecovered: (() -> Void)? = nil
+
     @Environment(\.dismiss) private var dismiss
 
     @State private var fuel: FuelType = .e10
@@ -80,6 +86,15 @@ struct TrendsView: View {
     }
 
     private func load() async {
+        // QA hook: force the unreachable state for screenshots (same pattern
+        // as -showTrends / -forceConnectionProblem). Runs before the fetch so
+        // the retry state renders immediately with no spinner flash.
+        if ProcessInfo.processInfo.arguments.contains("-forceHistoryFailure") {
+            series = []
+            loadFailed = true
+            onHistoryUnavailable?()
+            return
+        }
         isLoading = true
         loadFailed = false
         defer { isLoading = false }
@@ -98,6 +113,14 @@ struct TrendsView: View {
             loadFailed = firstSnapshot == nil
         }
         series = fetched
+        // A failure with no data IS a connection problem — raise the global
+        // banner so the user isn't stuck with a silent retry state. Success
+        // clears it (only if the banner is the connection banner).
+        if loadFailed {
+            onHistoryUnavailable?()
+        } else if hasAnyData {
+            onHistoryRecovered?()
+        }
     }
 
     private func yLabel(_ pence: Double) -> String {

FuelBoard/en.lproj/Localizable.strings

@@ -158,3 +158,13 @@
 "Prices are recorded each day FuelBoard's relay runs — check back in a few days." = "Prices are recorded each day FuelBoard's relay runs — check back in a few days.";
 "Average price over the days shown" = "Average price over the days shown";
 "Average pence above the day's cheapest favourite" = "Average pence above the day's cheapest favourite";
+
+/* Offline data banner */
+"Offline data from %@" = "Offline data from %@";
+"Offline data" = "Offline data";
+"Pull to refresh on the Stations tab" = "Pull to refresh on the Stations tab";
+"Offline data from %@. Pull to refresh on the Stations tab" = "Offline data from %@. Pull to refresh on the Stations tab";
+"Offline data. Pull to refresh on the Stations tab" = "Offline data. Pull to refresh on the Stations tab";
+"Check your internet connection" = "Check your internet connection";
+"Tap to try again" = "Tap to try again";
+"Check your internet connection. Tap to try again" = "Check your internet connection. Tap to try again";

FuelBoardTests/Tests/FuelBoardSharedTests/FuelBoardTests.swift

@@ -587,3 +587,22 @@ final class PriceDisplayTests: XCTestCase {
         XCTAssertEqual(FuelStore.priceTextSpoken(100.9), "£1.009")
     }
 }
+
+// MARK: - Offline data banner label
+
+final class OfflineDataLabelTests: XCTestCase {
+    func testOfflineDataLabelFormatsStampWithFractionalSeconds() {
+        // The bundled dump's real envelope stamp.
+        XCTAssertEqual(FuelStore.offlineDataLabel(from: "2026-08-15T08:46:33.000Z"), "15 Aug")
+    }
+
+    func testOfflineDataLabelToleratesPlainISODate() {
+        XCTAssertEqual(FuelStore.offlineDataLabel(from: "2026-08-15T08:46:33Z"), "15 Aug")
+    }
+
+    func testOfflineDataLabelNilWhenMissingOrUnparseable() {
+        XCTAssertNil(FuelStore.offlineDataLabel(from: nil))
+        XCTAssertNil(FuelStore.offlineDataLabel(from: ""))
+        XCTAssertNil(FuelStore.offlineDataLabel(from: "not-a-date"))
+    }
+}

Shared/FuelStore.swift

@@ -782,6 +782,27 @@ struct FuelStore {
         loadString(service: dataUpdatedKey)
     }
 
+    /// A short label for the offline-data banner: "15 Aug" from a GOV.UK
+    /// `data_updated` ISO 8601 stamp (with or without fractional seconds).
+    /// Nil when the stamp is missing or unparseable — callers then hide the
+    /// banner rather than label data with a wrong date.
+    static func offlineDataLabel(from stamp: String?) -> String? {
+        guard let stamp, !stamp.isEmpty else { return nil }
+        let withFraction = ISO8601DateFormatter()
+        withFraction.formatOptions = [.withInternetDateTime, .withFractionalSeconds]
+        var date = withFraction.date(from: stamp)
+        if date == nil {
+            let plain = ISO8601DateFormatter()
+            plain.formatOptions = [.withInternetDateTime]
+            date = plain.date(from: stamp)
+        }
+        guard let date else { return nil }
+        let formatter = DateFormatter()
+        formatter.dateFormat = "d MMM"
+        formatter.locale = Locale(identifier: "en_GB")
+        return formatter.string(from: date)
+    }
+
     /// True when the cached data is fresh enough that a scheduled auto-refresh
     /// should be skipped (twice-a-day policy).
     static var isCacheFresh: Bool {