fix: cap number pad entry at available balance across amount screens

Bitkit/Components/NumberPadTextField.swift

@@ -3,7 +3,7 @@ import SwiftUI
 /// NumberPadTextField - Amount view to be used with number pad
 struct NumberPadTextField: View {
     @EnvironmentObject var currency: CurrencyViewModel
-    @ObservedObject var viewModel: AmountInputViewModel
+    var viewModel: AmountInputViewModel
 
     var showConversion: Bool = true
     var showEditButton: Bool = false

Bitkit/Models/Toast.swift

@@ -5,6 +5,9 @@ struct Toast: Equatable {
         case success, info, lightning, warning, error
     }
 
+    /// Brief visibility for transient feedback (e.g. blocked number pad input).
+    static let visibilityTimeShort = 1.5
+
     let id: UUID
     let type: ToastType
     let title: String

Bitkit/Resources/Localization/en.lproj/Localizable.strings

@@ -164,6 +164,8 @@
 "lightning__spending_confirm__default" = "Use Defaults";
 "lightning__spending_advanced__title" = "Receiving\n<accent>capacity</accent>";
 "lightning__spending_advanced__fee" = "Liquidity fee";
+"lightning__spending_advanced__error_max__title" = "Receiving Capacity Maximum";
+"lightning__spending_advanced__error_max__description" = "The receiving capacity is currently limited to ₿ {amount}.";
 "lightning__liquidity__title" = "Liquidity\n<accent>& routing</accent>";
 "lightning__liquidity__text" = "Your Spending Balance uses the Lightning Network to make your payments cheaper, faster, and more private.\n\nThis works like internet access, but you pay for liquidity & routing instead of bandwidth.\n\nThis setup includes some one-time costs.";
 "lightning__liquidity__label" = "Spending Balance Liquidity";
@@ -1145,6 +1147,8 @@
 "wallet__send_available_savings" = "Available (savings)";
 "wallet__send_max_spending__title" = "Reserve Balance";
 "wallet__send_max_spending__description" = "The maximum spendable amount is a bit lower due to a required reserve balance.";
+"wallet__send_amount_exceeded__title" = "Insufficient balance";
+"wallet__send_amount_exceeded__description" = "The amount exceeds your available balance.";
 "wallet__send_review" = "Confirm";
 "wallet__send_confirming_in" = "Confirming in";
 "wallet__send_invoice_expiration" = "Invoice expiration";
@@ -1357,9 +1361,13 @@
 "wallet__lnurl_w_max" = "AvailablE TO WITHDRAW";
 "wallet__lnurl_w_text" = "The funds you withdraw will be deposited into your Bitkit spending balance.";
 "wallet__lnurl_w_button" = "Withdraw";
+"wallet__lnurl_w_error_max__title" = "Amount Too High";
+"wallet__lnurl_w_error_max__description" = "The amount exceeds the maximum you can withdraw.";
 "wallet__lnurl_p_title" = "Pay Bitcoin";
 "wallet__lnurl_pay__error_min__title" = "Amount Too Low";
 "wallet__lnurl_pay__error_min__description" = "The minimum amount for this invoice is ₿ {amount}.";
+"wallet__lnurl_pay__error_max__title" = "Amount Too High";
+"wallet__lnurl_pay__error_max__description" = "The amount exceeds this invoice's maximum.";
 "wallet__lnurl_p_max" = "Maximum amount";
 "wallet__balance_hidden_title" = "Wallet Balance Hidden";
 "wallet__balance_hidden_message" = "Swipe your wallet balance to reveal it again.";

Bitkit/ViewModels/AmountInputViewModel.swift

@@ -1,11 +1,21 @@
 import Foundation
 import SwiftUI
 
+@Observable
 @MainActor
-class AmountInputViewModel: ObservableObject {
-    @Published var amountSats: UInt64 = 0
-    @Published var displayText: String = ""
-    @Published var errorKey: String?
+final class AmountInputViewModel {
+    var amountSats: UInt64 = 0
+    var displayText: String = ""
+    var errorKey: String?
+
+    /// Optional per-screen cap (e.g. the max sendable balance in the send flow).
+    /// When set, input is additionally blocked above this value, on top of `maxAmount`.
+    var maxAmountOverride: UInt64?
+
+    /// Incremented each time input is blocked by the screen-specific cap (`maxAmountOverride`),
+    /// so views can react (e.g. show a toast). Not bumped when only the global
+    /// `maxAmount` blocks input.
+    private(set) var maxExceededCount = 0
 
     // MARK: - Constants
 
@@ -15,6 +25,12 @@ class AmountInputViewModel: ObservableObject {
     private let classicBitcoinDecimals = 8
     private let fiatDecimals = 2
 
+    /// The active upper bound for input: the global `maxAmount`, further restricted by `maxAmountOverride` when set.
+    private var effectiveMaxAmount: UInt64 {
+        guard let maxAmountOverride else { return maxAmount }
+        return Swift.min(maxAmount, maxAmountOverride)
+    }
+
     // MARK: - Private Properties
 
     private var rawInputText: String = ""
@@ -38,17 +54,25 @@ class AmountInputViewModel: ObservableObject {
             maxDecimals: maxDecimals
         )
 
+        // Deletions must always apply, even when the amount is above the cap (e.g. a
+        // prefilled invoice amount over the available balance, or a cap that dropped
+        // after input). The cap only blocks growing the amount; without this, each
+        // delete still leaves the amount over the cap and gets rejected, trapping the
+        // user with an invalid amount they can't reduce.
+        let isDeletion = key == "delete"
+
         // For decimal input (classic Bitcoin and fiat), preserve the text as-is
         // For integer input (modern Bitcoin), format the final amount
         if currency.primaryDisplay == .bitcoin && currency.displayUnit == .modern {
             let newAmount = convertToSats(newText, currency: currency)
 
-            if newAmount <= maxAmount {
+            if isDeletion || newAmount <= effectiveMaxAmount {
                 rawInputText = newText
                 displayText = formatDisplayTextFromAmount(newAmount, currency: currency)
                 amountSats = newAmount
                 errorKey = nil
             } else {
+                notifyMaxExceededIfCapped()
                 Haptics.notify(.warning)
                 errorKey = key
                 DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
@@ -59,7 +83,7 @@ class AmountInputViewModel: ObservableObject {
             // For decimal input, check limits before updating state
             if !newText.isEmpty {
                 let newAmount = convertToSats(newText, currency: currency)
-                if newAmount <= maxAmount {
+                if isDeletion || newAmount <= effectiveMaxAmount {
                     // Update both raw input and display text
                     rawInputText = newText
                     // Format with grouping separators but not decimal formatting
@@ -72,6 +96,7 @@ class AmountInputViewModel: ObservableObject {
                     errorKey = nil
                 } else {
                     // Block input when limit exceeded
+                    notifyMaxExceededIfCapped()
                     Haptics.notify(.warning)
                     errorKey = key
                     DispatchQueue.main.asyncAfter(deadline: .now() + 0.5) {
@@ -218,6 +243,14 @@ class AmountInputViewModel: ObservableObject {
 
     // MARK: - Private Methods
 
+    /// Signals blocked input to observers, but only when the screen-specific cap is the
+    /// limiting bound. Hitting the global `maxAmount` stays silent.
+    private func notifyMaxExceededIfCapped() {
+        if effectiveMaxAmount < maxAmount {
+            maxExceededCount += 1
+        }
+    }
+
     private func formatDisplayTextFromAmount(_ amountSats: UInt64, currency: CurrencyViewModel) -> String {
         if amountSats == 0 {
             return ""

Bitkit/Views/Transfer/FundManualAmountView.swift

@@ -8,13 +8,21 @@ struct FundManualAmountView: View {
 
     let lnPeer: LnPeer
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
     @State private var didAttemptPeerConnection = false
 
     var amountSats: UInt64 {
         amountViewModel.amountSats
     }
 
+    private var fundableBalanceSats: UInt64 {
+        UInt64(max(0, wallet.channelFundableBalanceSats))
+    }
+
+    private var isValidAmount: Bool {
+        amountSats > 0 && amountSats <= fundableBalanceSats
+    }
+
     var body: some View {
         VStack(spacing: 0) {
             NavigationBar(title: t("lightning__external__nav_title"))
@@ -58,7 +66,7 @@ struct FundManualAmountView: View {
                     amountViewModel.handleNumberPadInput(key, currency: currency)
                 }
 
-                CustomButton(title: t("common__continue"), isDisabled: amountSats == 0) {
+                CustomButton(title: t("common__continue"), isDisabled: !isValidAmount) {
                     navigation.navigate(.fundManualConfirm(lnPeer: lnPeer, amountSats: amountSats))
                 }
                 .accessibilityIdentifier("ExternalAmountContinue")
@@ -70,6 +78,24 @@ struct FundManualAmountView: View {
         .task {
             await connectToPeerIfNeeded()
         }
+        .onChange(of: wallet.channelFundableBalanceSats, initial: true) { updateInputCap() }
+        .onChange(of: amountViewModel.maxExceededCount) { showMaxExceededToast() }
+    }
+
+    private func updateInputCap() {
+        amountViewModel.maxAmountOverride = fundableBalanceSats > 0 ? fundableBalanceSats : nil
+    }
+
+    private func showMaxExceededToast() {
+        app.toast(
+            type: .warning,
+            title: t("lightning__spending_amount__error_max__title"),
+            description: t(
+                "lightning__spending_amount__error_max__description",
+                variables: ["amount": CurrencyFormatter.formatSats(fundableBalanceSats)]
+            ),
+            visibilityTime: Toast.visibilityTimeShort
+        )
     }
 
     private var numberPadButtons: some View {

Bitkit/Views/Transfer/SpendingAdvancedView.swift

@@ -10,7 +10,7 @@ struct SpendingAdvancedView: View {
     @EnvironmentObject var transfer: TransferViewModel
     @Environment(\.dismiss) var dismiss
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
     @State private var feeEstimate: UInt64?
     @State private var isLoading = false
     @State private var feeEstimateTask: Task<Void, Never>?
@@ -116,6 +116,25 @@ struct SpendingAdvancedView: View {
                 feeEstimate = nil
             }
         }
+        .onChange(of: transfer.transferValues.maxLspBalance, initial: true) { updateInputCap() }
+        .onChange(of: amountViewModel.maxExceededCount) { showMaxExceededToast() }
+    }
+
+    private func updateInputCap() {
+        let maxLspBalance = transfer.transferValues.maxLspBalance
+        amountViewModel.maxAmountOverride = maxLspBalance > 0 ? maxLspBalance : nil
+    }
+
+    private func showMaxExceededToast() {
+        app.toast(
+            type: .warning,
+            title: t("lightning__spending_advanced__error_max__title"),
+            description: t(
+                "lightning__spending_advanced__error_max__description",
+                variables: ["amount": CurrencyFormatter.formatSats(transfer.transferValues.maxLspBalance)]
+            ),
+            visibilityTime: Toast.visibilityTimeShort
+        )
     }
 
     private var actionButtons: some View {

Bitkit/Views/Transfer/SpendingAmount.swift

@@ -10,7 +10,7 @@ struct SpendingAmount: View {
     @EnvironmentObject var transfer: TransferViewModel
     @EnvironmentObject var wallet: WalletViewModel
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
     @State private var isLoading = false
     @State private var availableAmount: UInt64?
     @State private var maxTransferAmount: UInt64?
@@ -87,6 +87,24 @@ struct SpendingAmount: View {
                 await calculateMaxTransferAmount()
             }
         }
+        .onChange(of: maxTransferAmount) { updateInputCap() }
+        .onChange(of: amountViewModel.maxExceededCount) { showMaxExceededToast() }
+    }
+
+    private func updateInputCap() {
+        amountViewModel.maxAmountOverride = (maxTransferAmount ?? 0) > 0 ? maxTransferAmount : nil
+    }
+
+    private func showMaxExceededToast() {
+        app.toast(
+            type: .warning,
+            title: t("lightning__spending_amount__error_max__title"),
+            description: t(
+                "lightning__spending_amount__error_max__description",
+                variables: ["amount": CurrencyFormatter.formatSats(maxTransferAmount ?? 0)]
+            ),
+            visibilityTime: Toast.visibilityTimeShort
+        )
     }
 
     private var actionButtons: some View {

Bitkit/Views/Wallets/LnurlWithdraw/LnurlWithdrawAmount.swift

@@ -6,7 +6,7 @@ struct LnurlWithdrawAmount: View {
     @EnvironmentObject var wallet: WalletViewModel
     let onContinue: () -> Void
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
 
     var minAmount: Int {
         Int(max(1, app.lnurlWithdrawData!.minWithdrawableSat))
@@ -78,6 +78,23 @@ struct LnurlWithdrawAmount: View {
                 amountViewModel.updateFromSats(UInt64(minAmount), currency: currency)
             }
         }
+        .onChange(of: maxAmount, initial: true) { updateInputCap() }
+        .onChange(of: amountViewModel.maxExceededCount) { showMaxExceededToast() }
+    }
+
+    private func updateInputCap() {
+        let cap = max(minAmount, maxAmount)
+        amountViewModel.maxAmountOverride = cap > 0 ? UInt64(cap) : nil
+    }
+
+    private func showMaxExceededToast() {
+        app.toast(
+            type: .warning,
+            title: t("wallet__lnurl_w_error_max__title"),
+            description: t("wallet__lnurl_w_error_max__description"),
+            visibilityTime: Toast.visibilityTimeShort,
+            accessibilityIdentifier: "SendAmountExceededToast"
+        )
     }
 
     private func handleContinue() {

Bitkit/Views/Wallets/Receive/ReceiveCjitAmount.swift

@@ -9,7 +9,7 @@ struct ReceiveCjitAmount: View {
 
     @Binding var navigationPath: [ReceiveRoute]
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
 
     var minimumAmount: UInt64 {
         blocktank.minCjitSats ?? 0

Bitkit/Views/Wallets/Receive/ReceiveEdit.swift

@@ -12,7 +12,7 @@ struct ReceiveEdit: View {
 
     @Binding var navigationPath: [ReceiveRoute]
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
     @State private var note = ""
     @State private var isAmountInputFocused: Bool = false
     @FocusState private var isNoteEditorFocused: Bool

Bitkit/Views/Wallets/Send/LnurlPayAmount.swift

@@ -7,7 +7,7 @@ struct LnurlPayAmount: View {
 
     @Binding var navigationPath: [SendRoute]
 
-    @StateObject private var amountViewModel = AmountInputViewModel()
+    @State private var amountViewModel = AmountInputViewModel()
 
     var maxAmount: UInt64 {
         // TODO: subtract fee
@@ -81,6 +81,25 @@ struct LnurlPayAmount: View {
         .navigationBarHidden(true)
         .padding(.horizontal, 16)
         .sheetBackground()
+        .onChange(of: maxAmount, initial: true) { updateInputCap() }
+        .onChange(of: amountViewModel.maxExceededCount) { showMaxExceededToast() }
+    }
+
+    private func updateInputCap() {
+        amountViewModel.maxAmountOverride = maxAmount > 0 ? maxAmount : nil
+    }
+
+    private func showMaxExceededToast() {
+        // The cap is min(invoice max, spending balance); word the message for whichever bound is hit.
+        let isInvoiceCapped = app.lnurlPayData!.maxSendableSat < UInt64(wallet.totalLightningSats)
+
+        app.toast(
+            type: .warning,
+            title: t(isInvoiceCapped ? "wallet__lnurl_pay__error_max__title" : "wallet__send_amount_exceeded__title"),
+            description: t(isInvoiceCapped ? "wallet__lnurl_pay__error_max__description" : "wallet__send_amount_exceeded__description"),
+            visibilityTime: Toast.visibilityTimeShort,
+            accessibilityIdentifier: "SendAmountExceededToast"
+        )
     }
 
     private func onContinue() {