diff --git a/app/models/balance/reverse_calculator.rb b/app/models/balance/reverse_calculator.rb
index 39b530178..ba970fdcd 100644
--- a/app/models/balance/reverse_calculator.rb
+++ b/app/models/balance/reverse_calculator.rb
@@ -25,20 +25,20 @@ class Balance::ReverseCalculator < Balance::BaseCalculator
           start_non_cash_balance = end_non_cash_balance
           market_value_change = 0
         elsif valuation && valuation.entryable.reconciliation?
-          # Reconciliation waypoint: reset to the known API-reported balance.
-          # These waypoints are created by CurrentBalanceManager when it preserves
-          # a stale current_anchor as a reconciliation before replacing it.
-          # We derive both cash and non-cash from the total to ensure the split
-          # reflects the account's cash ratio on that date.
+          # Reconciliation waypoint: hard-reset the END-of-day balance to the
+          # API-reported value, neutralizing any drift accumulated from missing
+          # transactions between here and the next anchor. The START is still
+          # derived from this day's own flows, so a same-day transaction is
+          # attributed exactly once (and not added on top of the waypoint).
           end_cash_balance = derive_cash_balance_on_date_from_total(
             total_balance: valuation.amount,
             date: date
           )
           end_non_cash_balance = valuation.amount - end_cash_balance
 
-          start_cash_balance = end_cash_balance
-          start_non_cash_balance = end_non_cash_balance
-          market_value_change = 0
+          start_cash_balance = derive_start_cash_balance(end_cash_balance: end_cash_balance, date: date)
+          start_non_cash_balance = derive_start_non_cash_balance(end_non_cash_balance: end_non_cash_balance, date: date)
+          market_value_change = market_value_change_on_date(date, flows)
         else
           start_cash_balance = derive_start_cash_balance(end_cash_balance: end_cash_balance, date: date)
           start_non_cash_balance = derive_start_non_cash_balance(end_non_cash_balance: end_non_cash_balance, date: date)
diff --git a/test/models/balance/reverse_calculator_test.rb b/test/models/balance/reverse_calculator_test.rb
index cee497bc8..11f4463e3 100644
--- a/test/models/balance/reverse_calculator_test.rb
+++ b/test/models/balance/reverse_calculator_test.rb
@@ -231,6 +231,66 @@ class Balance::ReverseCalculatorTest < ActiveSupport::TestCase
     )
   end
 
+  # Regression for #2007: a reconciliation waypoint on a day that ALSO has a transaction.
+  # The waypoint is an END-of-day balance, so the day's own flow must derive the START
+  # (waypoint - flow), and the flow must NOT be added on top of the waypoint (double-count).
+  # Critically, the derived start (not the waypoint) is what carries back, so the prior
+  # gap day must not show a phantom jump.
+  test "reconciliation waypoint with a same-day transaction is not double-counted" do
+    account = create_account_with_ledger(
+      account: { type: Depository, balance: 20000, cash_balance: 20000, currency: "USD" },
+      entries: [
+        { type: "current_anchor", date: Date.current, balance: 20000 },
+        { type: "reconciliation", date: 2.days.ago, balance: 17000 }, # Waypoint (end-of-day)
+        { type: "transaction", date: 2.days.ago, amount: -2000 },      # 2000 deposit ON the waypoint day
+        { type: "opening_anchor", date: 4.days.ago, balance: 15000 }
+      ]
+    )
+
+    calculated = Balance::ReverseCalculator.new(account).calculate
+
+    assert_calculated_ledger_balances(
+      calculated_data: calculated,
+      expected_data: [
+        {
+          date: Date.current,
+          legacy_balances: { balance: 20000, cash_balance: 20000 },
+          balances: { start: 20000, start_cash: 20000, start_non_cash: 0, end_cash: 20000, end_non_cash: 0, end: 20000 },
+          flows: 0,
+          adjustments: 0
+        },
+        {
+          date: 1.day.ago,
+          legacy_balances: { balance: 20000, cash_balance: 20000 },
+          balances: { start: 20000, start_cash: 20000, start_non_cash: 0, end_cash: 20000, end_non_cash: 0, end: 20000 },
+          flows: 0,
+          adjustments: 0
+        },
+        {
+          date: 2.days.ago, # End forced to waypoint 17000; start derived from the +2000 deposit = 15000
+          legacy_balances: { balance: 17000, cash_balance: 17000 },
+          balances: { start: 15000, start_cash: 15000, start_non_cash: 0, end_cash: 17000, end_non_cash: 0, end: 17000 },
+          flows: { cash_inflows: 2000, cash_outflows: 0 },
+          adjustments: 0
+        },
+        {
+          date: 3.days.ago, # No phantom jump: stays at 15000 (the deposit is not re-applied here)
+          legacy_balances: { balance: 15000, cash_balance: 15000 },
+          balances: { start: 15000, start_cash: 15000, start_non_cash: 0, end_cash: 15000, end_non_cash: 0, end: 15000 },
+          flows: 0,
+          adjustments: 0
+        },
+        {
+          date: 4.days.ago,
+          legacy_balances: { balance: 15000, cash_balance: 15000 },
+          balances: { start: 15000, start_cash: 15000, start_non_cash: 0, end_cash: 15000, end_non_cash: 0, end: 15000 },
+          flows: 0,
+          adjustments: 0
+        } # Opening anchor
+      ]
+    )
+  end
+
 
   # Investment account balances are made of two components: cash and holdings.
   test "anchors on investment accounts calculate cash balance dynamically based on holdings value" do
diff --git a/test/models/balance/waypoint_gui_breakdown_test.rb b/test/models/balance/waypoint_gui_breakdown_test.rb
new file mode 100644
index 000000000..0a43c389f
--- /dev/null
+++ b/test/models/balance/waypoint_gui_breakdown_test.rb
@@ -0,0 +1,113 @@
+require "test_helper"
+
+# Proves what the day-detail "Details" popup (UI::Account::BalanceReconciliation)
+# shows for a daily-waypoint (EnableBanking-style) account with a transaction on
+# every waypoint day. Persists real balances and reads the actual PG generated
+# columns through the real GUI component.
+class Balance::WaypointGuiBreakdownTest < ActiveSupport::TestCase
+  include LedgerTestingHelper
+
+  def persist_and_load(account)
+    calculated = Balance::ReverseCalculator.new(account).calculate
+    account.balances.upsert_all(
+      calculated.map { |b|
+        b.attributes.slice(
+          "date", "balance", "cash_balance", "currency",
+          "start_cash_balance", "start_non_cash_balance",
+          "cash_inflows", "cash_outflows",
+          "non_cash_inflows", "non_cash_outflows",
+          "net_market_flows", "cash_adjustments", "non_cash_adjustments",
+          "flows_factor"
+        ).merge("updated_at" => Time.now)
+      },
+      unique_by: %i[account_id date currency]
+    )
+    account.balances.order(:date).to_a
+  end
+
+  # Reads the three lines exactly as the GUI Details popup renders them.
+  def gui_lines(balance, account)
+    items = UI::Account::BalanceReconciliation.new(balance: balance, account: account).reconciliation_items
+    {
+      start:    items.find { |i| i[:style] == :start }[:value].amount,
+      net_flow: items.find { |i| i[:style] == :flow  }[:value].amount,
+      final:    items.find { |i| i[:style] == :final }[:value].amount
+    }
+  end
+
+  def build_account
+    create_account_with_ledger(
+      account: { type: Depository, balance: 20000, cash_balance: 20000, currency: "USD" },
+      entries: [
+        { type: "current_anchor", date: Date.current, balance: 20000 },
+        { type: "reconciliation", date: 1.day.ago,  balance: 19000 },
+        { type: "transaction",    date: 1.day.ago,  amount: -1000 }, # +1000 deposit
+        { type: "reconciliation", date: 2.days.ago, balance: 17000 },
+        { type: "transaction",    date: 2.days.ago, amount: -2000 }, # +2000 deposit
+        { type: "reconciliation", date: 3.days.ago, balance: 16000 },
+        { type: "transaction",    date: 3.days.ago, amount: 500 },   # -500 expense
+        # 4.days.ago is a GAP day: no waypoint, no transaction
+        { type: "opening_anchor", date: 5.days.ago, balance: 15000 }
+      ]
+    )
+  end
+
+  # Hard assertions for the fix currently in the tree (derive-start).
+  test "derive-start fix: Net cash flow preserved on every waypoint day and it reconciles" do
+    account = build_account
+    balances = persist_and_load(account).index_by(&:date)
+
+    expectations = {
+      1.day.ago.to_date  => { start: 18000, net_flow: 1000,  final: 19000 },
+      2.days.ago.to_date => { start: 15000, net_flow: 2000,  final: 17000 },
+      3.days.ago.to_date => { start: 16500, net_flow: -500,  final: 16000 }
+    }
+
+    expectations.each do |date, exp|
+      g = gui_lines(balances[date], account)
+      assert_equal exp[:start],    g[:start],    "Start balance wrong on #{date}"
+      assert_equal exp[:net_flow], g[:net_flow], "Net cash flow wrong on #{date} (should NOT be zeroed)"
+      assert_equal exp[:final],    g[:final],    "Final balance wrong on #{date}"
+      assert_equal g[:start] + g[:net_flow], g[:final], "Breakdown does not reconcile on #{date}"
+      refute_equal 0, g[:net_flow], "Net cash flow was zeroed on #{date} — transaction hidden"
+    end
+  end
+
+  # Investment account: reconciliation waypoint on a day with a same-day trade.
+  # End total must match the API-reported waypoint (not waypoint + trade flows).
+  # Cash/non-cash split must be preserved and no double-count on the non-cash side.
+  test "investment reconciliation waypoint with same-day trade is not double-counted" do
+    account = create_account_with_ledger(
+      account: { type: Investment, balance: 20000, cash_balance: 10000, currency: "USD" },
+      entries: [
+        { type: "current_anchor", date: Date.current, balance: 20000 },
+        { type: "reconciliation", date: 1.day.ago, balance: 18000 }, # Bank says total was 18000
+        { type: "trade",          date: 1.day.ago, ticker: "AAPL", qty: 10, price: 100 }, # Buy $1000 of AAPL
+        { type: "opening_anchor", date: 3.days.ago, balance: 15000 }
+      ],
+      holdings: [
+        { date: Date.current,      ticker: "AAPL", qty: 10, price: 100, amount: 1000 },
+        { date: 1.day.ago.to_date, ticker: "AAPL", qty: 10, price: 100, amount: 1000 },
+        { date: 2.days.ago.to_date, ticker: "AAPL", qty: 0,  price: 100, amount: 0 },
+        { date: 3.days.ago.to_date, ticker: "AAPL", qty: 0,  price: 100, amount: 0 }
+      ]
+    )
+
+    balances = persist_and_load(account).index_by(&:date)
+    waypoint = balances[1.day.ago.to_date]
+
+    # End total must equal the API-reported waypoint — not 18000 + trade flows (which would be 20000).
+    assert_equal 18000, waypoint.end_balance, "Investment waypoint end_balance must equal 18000, not double-count the trade"
+
+    # Cash/non-cash flows from the trade must still be present (not zeroed).
+    assert waypoint.cash_outflows > 0 || waypoint.non_cash_inflows > 0,
+      "Trade flows should be preserved on the waypoint day, not zeroed"
+
+    # A trade moves cash → holdings but doesn't change the total balance, so
+    # the gap day correctly stays at the same total as the waypoint — this is
+    # expected, not a phantom. The key check is that the waypoint day itself
+    # didn't inflate above 18000 by double-counting the trade.
+    gap_day = balances[2.days.ago.to_date]
+    assert_equal 18000, gap_day.end_balance, "Gap day total should equal pre-trade balance (trade doesn't change total)"
+  end
+end