diff --git a/README.md b/README.md
index 6d71d58..95c4da1 100644
--- a/README.md
+++ b/README.md
@@ -93,10 +93,12 @@ Invoke-RestMethod http://localhost:5173/api/openapi.json
 
 账户页开启“快速记账”后使用紧凑卡片直接更新余额；转账按钮紧邻模式入口。右侧显示本次保存成功的余额、转账、还款及标记，支持逐项撤回；窄屏记录面板显示在账户列表下方。列表为当前页面会话，刷新或重新进入后清空，已保存账目仍在变化记录中。
 
-欠款账户弹窗提供“还款”，通过付款账户与欠款账户双边记账更新余额。可手动标记“本月已还款”和“当天已记账”，并筛选未还款或隐藏当天已记账的账户。数据库保留最后完成月份/日期，跨月、跨日只按当前 UTC+8 时间判断是否显示，无需定时删除；标记不会改变金额。
+欠款账户弹窗提供“还款”，通过付款账户与欠款账户双边记账更新余额。信用卡与独立债务还款支持优惠：正数减少扣款，负数表示手续费，欠款按本金减少。可手动标记“本月已还款”和“当天已记账”，并筛选未还款或隐藏当天已记账的账户。数据库保留最后完成月份/日期，跨月、跨日只按当前 UTC+8 时间判断是否显示，无需定时删除；标记不会改变金额。
 
 账户、独立资产和债务可在详情删除。存在配对往来或定时计划时需先处理依赖，避免破坏另一账户余额。详见 [快速记账更新与验收](docs/update-quick-entry-2026-10-04.md) 和 [项目删除说明](docs/update-position-deletion-2026-10-04.md)。
 
+净资产轨迹支持分别隐藏总资产、总负债和净资产折线；悬停或点击图表查看对应日期的金额，方向键切换日期。缺失汇率或估值时保留断线并提示不完整。详见 [还款优惠与图表更新](docs/update-repayment-trend-2026-10-04.md)。
+
 ## 连接 Agent / MCP
 
 设置中的“连接助手”提供可复制的接入提示词、能力说明及权限选择。OAuth 授权和草稿确认使用独立页面；可选择 1、3、7、30 天、1 年或永久授权，并分别控制读取、修改隐藏账户。普通权限分为只读、草稿修改、直接写入，草稿需本人在网页审阅确认后才生效。
diff --git a/apps/api/package.json b/apps/api/package.json
index ec57d5a..98f29fb 100644
--- a/apps/api/package.json
+++ b/apps/api/package.json
@@ -5,7 +5,7 @@
     "dev": "node scripts/dev.cjs",
     "build": "tsc",
     "typecheck": "tsc --noEmit",
-    "test": "tsx --test --test-concurrency=1 test/calculation.test.ts test/update.test.ts test/zip.test.ts test/metals.test.ts ../web/test/i18n.test.ts test/account-deletion.test.ts test/mcp-hosts.test.ts test/mcp-http.test.ts test/network.test.ts ../web/test/quick-entry.test.ts",
+    "test": "tsx --test --test-concurrency=1 test/calculation.test.ts test/update.test.ts test/zip.test.ts test/metals.test.ts ../web/test/i18n.test.ts test/account-deletion.test.ts test/mcp-hosts.test.ts test/mcp-http.test.ts test/network.test.ts ../web/test/quick-entry.test.ts ../web/test/net-worth-chart.test.ts",
     "db:generate": "prisma generate",
     "db:migrate": "node scripts/database.cjs deploy",
     "db:status": "node scripts/database.cjs status",
diff --git a/apps/api/test/quick-entry-integration.test.ts b/apps/api/test/quick-entry-integration.test.ts
index e5a2311..678f866 100644
--- a/apps/api/test/quick-entry-integration.test.ts
+++ b/apps/api/test/quick-entry-integration.test.ts
@@ -168,6 +168,58 @@ test('quick entries undo paired repayment and balance, persist monthly marks, pr
     assert.equal((await call(a, '/transfers/' + payment.data.id, 'DELETE')).status, 200);
     assert.equal((await call(a, '/positions/' + cash)).data.amount, '1000');
     assert.equal((await call(a, '/positions/' + card)).data.amount, '200');
+
+    for (const [fee, expected] of [
+      ['-5.87654321', '955.87654321'],
+      ['1.86420975', '948.13579025'],
+    ] as const) {
+      const movement = await call(a, '/transfers', 'POST', {
+        sourceId: cash,
+        targetId: card,
+        amount: '50',
+        received: '50',
+        fee,
+        date: '2026-09-03T11:00',
+        requestId: randomUUID(),
+      });
+      assert.equal(movement.status, 201);
+      assert.equal((await call(a, '/positions/' + cash)).data.amount, expected);
+      assert.equal((await call(a, '/positions/' + card)).data.amount, '150');
+      assert.equal((await call(a, '/transfers/' + movement.data.id, 'DELETE')).status, 200);
+      assert.equal((await call(a, '/positions/' + cash)).data.amount, '1000');
+      assert.equal((await call(a, '/positions/' + card)).data.amount, '200');
+    }
+    const invalidDiscount = await call(a, '/transfers', 'POST', {
+      sourceId: cash,
+      targetId: card,
+      amount: '30',
+      received: '30',
+      fee: '-31',
+      date: '2026-09-03T11:00',
+      requestId: randomUUID(),
+    });
+    assert.equal(invalidDiscount.status, 400);
+    assert.equal((await call(a, '/positions/' + cash)).data.amount, '1000');
+    const loan = await create('测试独立欠款', 'debt', 'liability', 'personal', '200');
+    for (const [fee, expected] of [
+      ['-5', '975'],
+      ['2', '968'],
+    ] as const) {
+      const movement = await call(a, '/transfers', 'POST', {
+        operation: 'repay',
+        sourceId: cash,
+        targetId: loan,
+        amount: '30',
+        received: '30',
+        fee,
+        date: '2026-09-03T12:00',
+        requestId: randomUUID(),
+      });
+      assert.equal(movement.status, 201);
+      assert.equal((await call(a, '/positions/' + cash)).data.amount, expected);
+      assert.equal((await call(a, '/positions/' + loan)).data.amount, '170');
+      assert.equal((await call(a, '/transfers/' + movement.data.id, 'DELETE')).status, 200);
+    }
     const month = today().slice(0, 7),
       path = '/positions/' + card + '/repayment-mark';
     assert.equal((await call(b, path, 'PATCH', { month, expectedMonth: null })).status, 404);
diff --git a/apps/web/src/App.tsx b/apps/web/src/App.tsx
index 01ae418..849c56b 100644
--- a/apps/web/src/App.tsx
+++ b/apps/web/src/App.tsx
@@ -46,6 +46,7 @@ import {
   type PageResult,
 } from './api';
 import './style.css';
+import { NetWorthChart } from './NetWorthChart';
 import { allOverviewCards, overviewCardLabels } from './overview-cards';
 import { useToast } from './Toast';
 import { GroupOrderContext } from './GroupOrderContext';
@@ -165,76 +166,6 @@ function Empty({ title, body, action }: { title: string; body: string; action?:
     </div>
   );
 }
-function Chart({ rows, base }: { rows: Total[]; base: string }) {
-  const valid = rows.filter((r) => r.complete);
-  if (valid.length < 2)
-    return (
-      <Empty
-        title={tr('等待更多历史记录')}
-        body={tr('至少两个日期的完整余额和汇率记录，才能绘制趋势。')}
-      />
-    );
-  const values = valid.flatMap((r) => [Number(r.assets), Number(r.liabilities), Number(r.net)]),
-    min = Math.min(0, ...values),
-    max = Math.max(1, ...values),
-    w = 720,
-    h = 210;
-  const x = (date: string) =>
-    35 +
-    ((new Date(date).getTime() - new Date(rows[0].date).getTime()) /
-      (new Date(rows.at(-1)!.date).getTime() - new Date(rows[0].date).getTime() || 1)) *
-      (w - 65);
-  const y = (v: string) => 15 + ((max - Number(v)) / (max - min)) * (h - 40);
-  const series = ['assets', 'liabilities', 'net'] as const;
-  return (
-    <>
-      <div className="legend">
-        <span className="green">{tr('总资产')}</span>
-        <span className="danger-text">{tr('总负债')}</span>
-        <span className="blue">{tr('净资产')}</span>
-        <small>{base}</small>
-      </div>
-      <svg
-        viewBox={`0 0 ${w} ${h}`}
-        className="chart"
-        role="img"
-        aria-label={tr('资产、负债和净资产历史趋势')}
-      >
-        <line x1="35" y1={y('0')} x2="690" y2={y('0')} stroke="#dbe4e2" />
-        {series.map((s, i) => (
-          <path
-            key={s}
-            d={rows
-              .map((r, n) =>
-                r.complete
-                  ? `${n === 0 || !rows[n - 1].complete ? 'M' : 'L'}${x(r.date)},${y(r[s])}`
-                  : '',
-              )
-              .join(' ')}
-            fill="none"
-            stroke={['#199b76', '#c73542', '#457bca'][i]}
-            strokeWidth="3"
-          />
-        ))}
-        {valid.map((r) => (
-          <circle key={r.date} cx={x(r.date)} cy={y(r.net)} r="4" fill="#457bca">
-            <title>
-              {r.date} {tr('净资产')}
-              {money(r.net, base)}
-            </title>
-          </circle>
-        ))}
-      </svg>
-      <div className="chart-dates">
-        <span>{rows[0].date}</span>
-        <span>{rows.at(-1)!.date}</span>
-      </div>
-      {rows.some((r) => !r.complete) && (
-        <p className="muted">{tr('缺失汇率的日期未绘制，曲线在该处断开。')}</p>
-      )}
-    </>
-  );
-}
 export default function App() {
   const locale = useLocale();
   const sessionGeneration = useRef(0),
@@ -381,6 +312,7 @@ export default function App() {
         currency: source?.currency || '',
         amount: value.amount,
         received: value.received,
+        fee: value.fee,
         targetCurrency: target?.currency,
         date: value.date,
       },
@@ -1390,7 +1322,7 @@ export default function App() {
                       '默认最近90天；周一至周日及自然月取期末余额，变化归因累计区间内每日变化，首尾不足周期按实际范围。',
                     )}
                   </p>
-                  <Chart rows={overview.trend} base={user.baseCurrency} />
+                  <NetWorthChart rows={overview.trend} base={user.baseCurrency} />
                   <p className="muted">
                     {tr('按当时可用汇率重放；更正历史后重新计算。归档项目仍计入。')}
                   </p>
diff --git a/apps/web/src/DebtPaymentForm.tsx b/apps/web/src/DebtPaymentForm.tsx
index 13370d9..ba2bcce 100644
--- a/apps/web/src/DebtPaymentForm.tsx
+++ b/apps/web/src/DebtPaymentForm.tsx
@@ -1,4 +1,5 @@
 import { AccountPicker } from './AccountPicker';
+import { repaymentFee } from './repayment';
 import { useState, type FormEvent } from 'react';
 import { type Position, nowMinute, money, requestUuid, positionAmount } from './api';
 import { t as tr } from './i18n';
@@ -45,7 +46,12 @@ export function DebtPaymentForm({
   const same = debt?.currency === account?.currency;
   function save(event: FormEvent<HTMLFormElement>) {
     event.preventDefault();
-    submit(Object.fromEntries(new FormData(event.currentTarget)));
+    const data = Object.fromEntries(new FormData(event.currentTarget));
+    if (operation === 'repay') {
+      data.fee = repaymentFee(String(data.discount));
+      delete data.discount;
+    }
+    submit(data);
   }
   if (!accounts.length || !debts.length)
     return <p>{tr('请先创建启用的资产账户和借入或借出债务。')}</p>;
@@ -122,9 +128,11 @@ export function DebtPaymentForm({
         )}
       </label>
       <label>
-        {tr('手续费 / 优惠')} ({account?.currency})
+        {tr(operation === 'repay' ? '还款优惠（负数表示手续费）' : '手续费 / 优惠')} (
+        {account?.currency})
         <input
-          name="fee"
+          name={operation === 'repay' ? 'discount' : 'fee'}
+          key={operation}
           required
           defaultValue="0"
           inputMode="decimal"
@@ -132,7 +140,11 @@ export function DebtPaymentForm({
         />
       </label>
       <p className="muted">
-        {tr('手续费只影响账户余额：付款时额外扣除，收款时从到账金额扣除；负数表示优惠。')}
+        {tr(
+          operation === 'repay'
+            ? '正数为优惠，负数为手续费，0 表示无优惠；只影响付款账户，优惠不能超过还款金额。跨币种请填写欠款减少金额。'
+            : '手续费只影响账户余额：付款时额外扣除，收款时从到账金额扣除；负数表示优惠。',
+        )}
       </p>
       <label>
         {tr('记录时间（UTC+8）')}
diff --git a/apps/web/src/NetWorthChart.tsx b/apps/web/src/NetWorthChart.tsx
new file mode 100644
index 0000000..6bd4d68
--- /dev/null
+++ b/apps/web/src/NetWorthChart.tsx
@@ -0,0 +1,209 @@
+import React, { useId, useState, type PointerEvent } from 'react';
+import { money, type Total } from './api';
+import { t as tr } from './i18n';
+
+const series = [
+  { key: 'assets', label: '总资产', color: '#199b76' },
+  { key: 'liabilities', label: '总负债', color: '#c73542' },
+  { key: 'net', label: '净资产', color: '#457bca' },
+] as const;
+type SeriesKey = (typeof series)[number]['key'];
+const dateValue = (date: string) => Date.parse(date + 'T00:00:00Z');
+export function nearestTrendIndex(rows: Pick<Total, 'date'>[], time: number) {
+  let index = 0,
+    distance = Infinity;
+  rows.forEach((row, i) => {
+    const next = Math.abs(dateValue(row.date) - time);
+    if (next < distance) {
+      index = i;
+      distance = next;
+    }
+  });
+  return index;
+}
+export function trendPath(
+  rows: Total[],
+  key: SeriesKey,
+  x: (date: string) => number,
+  y: (value: string) => number,
+) {
+  return rows
+    .map((r, n) =>
+      r.complete ? `${n === 0 || !rows[n - 1].complete ? 'M' : 'L'}${x(r.date)},${y(r[key])}` : '',
+    )
+    .join(' ');
+}
+export function NetWorthChart({ rows, base }: { rows: Total[]; base: string }) {
+  const [visible, setVisible] = useState<Record<SeriesKey, boolean>>({
+    assets: true,
+    liabilities: true,
+    net: true,
+  });
+  const [activeDate, setActiveDate] = useState<string | null>(null);
+  const tooltipId = useId();
+  const valid = rows.filter((r) => r.complete);
+  if (valid.length < 2)
+    return (
+      <div className="empty">
+        <h3>{tr('等待更多历史记录')}</h3>
+        <p>{tr('至少两个日期的完整余额和汇率记录，才能绘制趋势。')}</p>
+      </div>
+    );
+  const shown = series.filter((s) => visible[s.key]);
+  const values = valid.flatMap((r) => shown.map((s) => Number(r[s.key])));
+  const min = Math.min(0, ...values),
+    max = Math.max(1, ...values);
+  const start = dateValue(rows[0].date),
+    end = dateValue(rows.at(-1)!.date);
+  const x = (date: string) => 35 + ((dateValue(date) - start) / (end - start || 1)) * 655;
+  const y = (value: string) => 15 + ((max - Number(value)) / (max - min)) * 170;
+  const active = rows.find((r) => r.date === activeDate);
+  function point(event: PointerEvent<SVGSVGElement>) {
+    if (!shown.length) return;
+    const matrix = event.currentTarget.getScreenCTM();
+    if (!matrix) return;
+    const position = new DOMPoint(event.clientX, event.clientY).matrixTransform(matrix.inverse());
+    const time = start + Math.max(0, Math.min(1, (position.x - 35) / 655)) * (end - start);
+    setActiveDate(rows[nearestTrendIndex(rows, time)].date);
+  }
+  return (
+    <div className="trend-chart">
+      <div className="legend trend-legend" aria-label={tr('趋势折线显示设置')}>
+        {series.map((s) => (
+          <button
+            key={s.key}
+            type="button"
+            aria-pressed={visible[s.key]}
+            style={{ color: s.color }}
+            className={visible[s.key] ? 'trend-series' : 'trend-series is-hidden'}
+            onClick={() => setVisible((v) => ({ ...v, [s.key]: !v[s.key] }))}
+          >
+            <span aria-hidden="true">{visible[s.key] ? '●' : '○'}</span> {tr(s.label)}
+          </button>
+        ))}
+        <small>{base}</small>
+      </div>
+      {!shown.length ? (
+        <p className="muted" role="status">
+          {tr('已隐藏全部折线，点击上方名称可重新显示。')}
+        </p>
+      ) : (
+        <>
+          <p className="muted trend-help" id={tooltipId + '-help'}>
+            {tr('点击名称切换折线；悬停或点击图表查看当天数据，方向键切换日期。')}
+          </p>
+          <div className="trend-plot">
+            <svg
+              viewBox="0 0 720 210"
+              className="chart"
+              role="img"
+              tabIndex={0}
+              aria-label={tr('资产、负债和净资产历史趋势')}
+              aria-describedby={tooltipId + '-help'}
+              onPointerMove={point}
+              onPointerDown={point}
+              onPointerLeave={(e) => {
+                if (e.pointerType === 'mouse' && document.activeElement !== e.currentTarget)
+                  setActiveDate(null);
+              }}
+              onFocus={() => setActiveDate((current) => current || rows.at(-1)!.date)}
+              onBlur={() => setActiveDate(null)}
+              onKeyDown={(e) => {
+                if (!['ArrowLeft', 'ArrowRight', 'Home', 'End', 'Escape'].includes(e.key)) return;
+                e.preventDefault();
+                if (e.key === 'Escape') {
+                  setActiveDate(null);
+                  return;
+                }
+                const current = rows.findIndex((r) => r.date === activeDate);
+                const next =
+                  e.key === 'Home'
+                    ? 0
+                    : e.key === 'End'
+                      ? rows.length - 1
+                      : Math.max(
+                          0,
+                          Math.min(
+                            rows.length - 1,
+                            (current < 0 ? rows.length - 1 : current) +
+                              (e.key === 'ArrowLeft' ? -1 : 1),
+                          ),
+                        );
+                setActiveDate(rows[next].date);
+              }}
+            >
+              <line x1="35" y1={y('0')} x2="690" y2={y('0')} stroke="#dbe4e2" />
+              {shown.map((s) => (
+                <path
+                  key={s.key}
+                  data-series={s.key}
+                  d={trendPath(rows, s.key, x, y)}
+                  fill="none"
+                  stroke={s.color}
+                  strokeWidth="3"
+                />
+              ))}
+              {active && (
+                <line
+                  x1={x(active.date)}
+                  x2={x(active.date)}
+                  y1="15"
+                  y2="185"
+                  stroke="#899b94"
+                  strokeDasharray="4 4"
+                />
+              )}
+              {shown.map((s) =>
+                valid.map((r) => (
+                  <circle
+                    key={s.key + r.date}
+                    cx={x(r.date)}
+                    cy={y(r[s.key])}
+                    r={activeDate === r.date ? 5 : 2.5}
+                    fill={s.color}
+                  >
+                    <title>{r.date + ' · ' + tr(s.label) + ' ' + money(r[s.key], base)}</title>
+                  </circle>
+                )),
+              )}
+            </svg>
+            {active && (
+              <section
+                className="trend-tooltip"
+                id={tooltipId}
+                role="status"
+                aria-label={tr('当天趋势数据')}
+              >
+                <strong>{active.date}</strong>
+                {active.complete ? (
+                  <dl>
+                    {shown.map((s) => (
+                      <React.Fragment key={s.key}>
+                        <dt>
+                          <span style={{ color: s.color }} aria-hidden="true">
+                            ●
+                          </span>{' '}
+                          {tr(s.label)}
+                        </dt>
+                        <dd>{money(active[s.key], base)}</dd>
+                      </React.Fragment>
+                    ))}
+                  </dl>
+                ) : (
+                  <p>{tr('当天估值或汇率不完整，无法显示完整总额。')}</p>
+                )}
+              </section>
+            )}
+          </div>
+        </>
+      )}
+      <div className="chart-dates">
+        <span>{rows[0].date}</span>
+        <span>{rows.at(-1)!.date}</span>
+      </div>
+      {rows.some((r) => !r.complete) && (
+        <p className="muted">{tr('缺失汇率的日期未绘制，曲线在该处断开。')}</p>
+      )}
+    </div>
+  );
+}
diff --git a/apps/web/src/QuickJournal.tsx b/apps/web/src/QuickJournal.tsx
index fb24448..0497db9 100644
--- a/apps/web/src/QuickJournal.tsx
+++ b/apps/web/src/QuickJournal.tsx
@@ -1,4 +1,5 @@
 import React, { useState } from 'react';
+import { repaymentFee } from './repayment';
 import { AccountPicker } from './AccountPicker';
 import { QuickTransfer } from './QuickTransfer';
 import { money, positionAmount, type Position } from './api';
@@ -14,6 +15,7 @@ export type QuickEntry = {
   after?: string;
   amount?: string;
   received?: string;
+  fee?: string;
   targetCurrency?: string;
   date: string;
   previousMonth?: string | null;
@@ -82,6 +84,15 @@ export function QuickJournal({
                   )}
                 </p>
               )}
+              {entry.kind === 'transfer' && entry.fee && !/^-?0(?:\.0+)?$/.test(entry.fee) && (
+                <p>
+                  {tr(entry.fee.startsWith('-') ? '优惠' : '手续费')} ·{' '}
+                  {money(
+                    entry.fee.startsWith('-') ? repaymentFee(entry.fee) : entry.fee,
+                    entry.currency,
+                  )}
+                </p>
+              )}
               {entry.kind === 'mark' && (
                 <p>{tr(entry.month ? '已标记本月还款' : '已取消本月标记')}</p>
               )}
@@ -154,6 +165,7 @@ export function QuickRepayment({
               changeSource={() => setSourceId('')}
               changeTarget={() => {}}
               fixedTarget
+              repayment
               actionLabel={tr('确认还款')}
               submit={submit}
             />
diff --git a/apps/web/src/QuickTransfer.tsx b/apps/web/src/QuickTransfer.tsx
index a3f2c48..bc99501 100644
--- a/apps/web/src/QuickTransfer.tsx
+++ b/apps/web/src/QuickTransfer.tsx
@@ -1,4 +1,5 @@
 import { useState } from 'react';
+import { repaymentFee } from './repayment';
 import { money, positionAmount, nowMinute, requestUuid, type Position } from './api';
 import { t as tr } from './i18n';
 export function QuickTransfer({
@@ -10,6 +11,7 @@ export function QuickTransfer({
   submit,
   actionLabel,
   fixedTarget,
+  repayment,
 }: {
   source: Position;
   target: Position;
@@ -19,6 +21,7 @@ export function QuickTransfer({
   submit: (data: unknown) => void;
   actionLabel?: string;
   fixedTarget?: boolean;
+  repayment?: boolean;
 }) {
   const [amount, setAmount] = useState('');
   const [requestId] = useState(requestUuid);
@@ -34,7 +37,7 @@ export function QuickTransfer({
           targetId: target.id,
           amount,
           received: same ? amount : String(f.get('received')),
-          fee: '0',
+          fee: repayment ? repaymentFee(String(f.get('discount'))) : '0',
           notes: '',
           date: nowMinute(),
         });
@@ -62,7 +65,7 @@ export function QuickTransfer({
         </div>
       </div>
       <label>
-        {tr('转出金额（')}
+        {tr(repayment ? '还款金额（' : '转出金额（')}
         {source.currency}）
         <input
           name="amount"
@@ -77,7 +80,7 @@ export function QuickTransfer({
       </label>
       {!same && (
         <label>
-          {tr('实际到账（')}
+          {tr(repayment ? '欠款减少金额（' : '实际到账（')}
           {target.currency}）
           <input
             name="received"
@@ -88,7 +91,26 @@ export function QuickTransfer({
           />
         </label>
       )}
-      <p className="muted">{tr('按当前时间记录，手续费为 0。跨币种请填写实际到账金额。')}</p>
+      {repayment && (
+        <label>
+          {tr('还款优惠（负数表示手续费）')} ({source.currency})
+          <input
+            name="discount"
+            required
+            defaultValue="0"
+            inputMode="decimal"
+            pattern="-?(0|[1-9][0-9]{0,15})([.][0-9]{1,8})?"
+            disabled={busy}
+          />
+        </label>
+      )}
+      <p className="muted">
+        {tr(
+          repayment
+            ? '正数为优惠，负数为手续费，0 表示无优惠；只影响付款账户，优惠不能超过还款金额。跨币种请填写欠款减少金额。'
+            : '按当前时间记录，手续费为 0。跨币种请填写实际到账金额。',
+        )}
+      </p>
       <button className="primary" disabled={busy}>
         {busy ? tr('正在保存…') : actionLabel || tr('确认转账')}
       </button>
diff --git a/apps/web/src/locales/en.json b/apps/web/src/locales/en.json
index cc9b280..5a21b52 100644
--- a/apps/web/src/locales/en.json
+++ b/apps/web/src/locales/en.json
@@ -607,5 +607,15 @@
   "计入总资产": "Included in total assets",
   "已标记当天记账": "Marked booked today",
   "已取消当天标记": "Removed today’s mark",
-  "当前筛选下没有账户，可切换筛选查看其他账户。": "No accounts match these filters. Change the filters to view other accounts."
+  "当前筛选下没有账户，可切换筛选查看其他账户。": "No accounts match these filters. Change the filters to view other accounts.",
+  "还款金额（": "Repayment amount (",
+  "欠款减少金额（": "Debt reduction (",
+  "还款优惠（负数表示手续费）": "Repayment discount (negative for fees)",
+  "正数为优惠，负数为手续费，0 表示无优惠；只影响付款账户，优惠不能超过还款金额。跨币种请填写欠款减少金额。": "Positive values are discounts; negative values are fees; zero means no discount. Only the payment account is adjusted. Discounts cannot exceed the repayment amount. For different currencies, enter the debt reduction.",
+  "优惠": "Discount",
+  "趋势折线显示设置": "Trend series visibility",
+  "已隐藏全部折线，点击上方名称可重新显示。": "All series are hidden. Click a name above to show it again.",
+  "点击名称切换折线；悬停或点击图表查看当天数据，方向键切换日期。": "Click a name to toggle a series. Hover or tap the chart to inspect a date; use arrow keys to move between dates.",
+  "当天趋势数据": "Data for selected date",
+  "当天估值或汇率不完整，无法显示完整总额。": "Valuations or exchange rates are incomplete for this date; full totals are unavailable."
 }
diff --git a/apps/web/src/locales/zh-Hant.json b/apps/web/src/locales/zh-Hant.json
index afb9f7c..f02c885 100644
--- a/apps/web/src/locales/zh-Hant.json
+++ b/apps/web/src/locales/zh-Hant.json
@@ -607,5 +607,15 @@
   "计入总资产": "計入總資產",
   "已标记当天记账": "已標記當天記賬",
   "已取消当天标记": "已取消當天標記",
-  "当前筛选下没有账户，可切换筛选查看其他账户。": "當前篩選下沒有賬戶，可切換篩選查看其他賬戶。"
+  "当前筛选下没有账户，可切换筛选查看其他账户。": "當前篩選下沒有賬戶，可切換篩選查看其他賬戶。",
+  "还款金额（": "還款金額（",
+  "欠款减少金额（": "欠款減少金額（",
+  "还款优惠（负数表示手续费）": "還款優惠（負數表示手續費）",
+  "正数为优惠，负数为手续费，0 表示无优惠；只影响付款账户，优惠不能超过还款金额。跨币种请填写欠款减少金额。": "正數為優惠，負數為手續費，0 表示無優惠；隻影響付款賬戶，優惠不能超過還款金額。跨幣種請填寫欠款減少金額。",
+  "优惠": "優惠",
+  "趋势折线显示设置": "趨勢折線顯示設置",
+  "已隐藏全部折线，点击上方名称可重新显示。": "已隱藏全部折線，點擊上方名稱可重新顯示。",
+  "点击名称切换折线；悬停或点击图表查看当天数据，方向键切换日期。": "點擊名稱切換折線；懸停或點擊圖表查看當天數據，方向鍵切換日期。",
+  "当天趋势数据": "當天趨勢數據",
+  "当天估值或汇率不完整，无法显示完整总额。": "當天估值或匯率不完整，無法顯示完整總額。"
 }
diff --git a/apps/web/src/repayment.ts b/apps/web/src/repayment.ts
new file mode 100644
index 0000000..1175ef6
--- /dev/null
+++ b/apps/web/src/repayment.ts
@@ -0,0 +1,7 @@
+// UI: positive discount, negative surcharge. API stores the opposite fee sign.
+// Flip the decimal string directly to preserve all eight fractional digits.
+export function repaymentFee(discount: string) {
+  if (!/^-?(0|[1-9]\d{0,15})(\.\d{1,8})?$/.test(discount)) throw new Error('还款优惠格式无效');
+  if (/^-?0(?:\.0+)?$/.test(discount)) return '0';
+  return discount.startsWith('-') ? discount.slice(1) : '-' + discount;
+}
diff --git a/apps/web/src/style.css b/apps/web/src/style.css
index b039add..c350fe5 100644
--- a/apps/web/src/style.css
+++ b/apps/web/src/style.css
@@ -2422,3 +2422,73 @@ textarea,
     top: 225px;
   }
 }
+
+.trend-legend {
+  flex-wrap: wrap;
+  gap: 8px;
+}
+.trend-legend .trend-series {
+  border: 1px solid #dbe4df;
+  background: #fff;
+  padding: 6px 10px;
+  border-radius: 8px;
+  font-size: 13px;
+}
+.trend-legend .trend-series.is-hidden {
+  opacity: 0.55;
+  text-decoration: line-through;
+  background: #f2f5f3;
+}
+.trend-legend .trend-series:focus-visible,
+.trend-plot svg:focus-visible {
+  outline: 2px solid #457bca;
+  outline-offset: 2px;
+}
+.trend-help {
+  font-size: 12px;
+  margin: 8px 0;
+}
+.trend-plot {
+  position: relative;
+}
+.trend-plot .chart {
+  display: block;
+  cursor: crosshair;
+}
+.trend-tooltip {
+  position: absolute;
+  top: 12px;
+  transform: translateX(-50%);
+  pointer-events: none;
+  z-index: 2;
+  width: max-content;
+  max-width: min(280px, 90%);
+  padding: 10px 12px;
+  background: #ffffffee;
+  border: 1px solid #cbd9d2;
+  border-radius: 10px;
+  box-shadow: 0 4px 18px #17374718;
+  font-size: 12px;
+}
+.trend-tooltip dl {
+  display: grid;
+  grid-template-columns: auto auto;
+  gap: 5px 14px;
+  margin: 6px 0 0;
+}
+.trend-tooltip dd {
+  margin: 0;
+  text-align: right;
+  overflow-wrap: anywhere;
+  font-variant-numeric: tabular-nums;
+}
+.trend-tooltip p {
+  margin: 6px 0 0;
+}
+
+.trend-tooltip {
+  left: auto;
+  right: 12px;
+  transform: none;
+  max-width: calc(100% - 24px);
+}
diff --git a/apps/web/test/net-worth-chart.test.ts b/apps/web/test/net-worth-chart.test.ts
new file mode 100644
index 0000000..ad95dcc
--- /dev/null
+++ b/apps/web/test/net-worth-chart.test.ts
@@ -0,0 +1,45 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { nearestTrendIndex, trendPath, NetWorthChart } from '../src/NetWorthChart';
+import { createElement } from 'react';
+import { renderToStaticMarkup } from 'react-dom/server';
+const rows = [
+  {
+    date: '2026-09-01',
+    assets: '100.86420975',
+    liabilities: '20',
+    net: '80.86420975',
+    complete: true,
+    missing: [],
+  },
+  {
+    date: '2026-09-02',
+    assets: '0',
+    liabilities: '0',
+    net: '0',
+    complete: false,
+    missing: ['USD'],
+  },
+  { date: '2026-09-10', assets: '120', liabilities: '20', net: '100', complete: true, missing: [] },
+];
+test('hover dates use time distance across uneven dates and expose missing dates', () => {
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-09-02T00:00:00Z')), 1);
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-09-09T00:00:00Z')), 2);
+  assert.equal(nearestTrendIndex(rows, Date.parse('2026-08-01T00:00:00Z')), 0);
+});
+test('trend paths keep a gap for incomplete dates rather than connecting misleading totals', () => {
+  const path = trendPath(
+    rows,
+    'net',
+    (d) => Number(d.slice(-2)),
+    (v) => Number(v),
+  );
+  assert.equal(path, 'M1,80.86420975  M10,100');
+});
+test('trend legend offers three independent toggles and exact monetary data', () => {
+  const html = renderToStaticMarkup(createElement(NetWorthChart, { rows, base: 'CNY' }));
+  assert.equal((html.match(/aria-pressed="true"/g) || []).length, 3);
+  assert.equal((html.match(/data-series=/g) || []).length, 3);
+  assert.match(html, /80\.86420975/);
+  assert.match(html, /tabindex="0"/);
+});
diff --git a/apps/web/test/quick-entry.test.ts b/apps/web/test/quick-entry.test.ts
index 1cc46fe..a103fff 100644
--- a/apps/web/test/quick-entry.test.ts
+++ b/apps/web/test/quick-entry.test.ts
@@ -1,3 +1,4 @@
+import { repaymentFee } from '../src/repayment';
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import {
@@ -76,3 +77,11 @@ test('daily badges expire and filters combine month and day without mutating mar
   );
   assert.equal(p.lastBookedDate, '2026-10-04');
 });
+
+test('repayment discount uses opposite fee sign without decimal precision loss', () => {
+  assert.equal(repaymentFee('5.87654321'), '-5.87654321');
+  assert.equal(repaymentFee('-1.86420975'), '1.86420975');
+  assert.equal(repaymentFee('-0.00000000'), '0');
+  assert.equal(repaymentFee('0'), '0');
+  assert.throws(() => repaymentFee('1e3'));
+});
diff --git a/docs/update-repayment-trend-2026-10-04.md b/docs/update-repayment-trend-2026-10-04.md
new file mode 100644
index 0000000..29853c7
--- /dev/null
+++ b/docs/update-repayment-trend-2026-10-04.md
@@ -0,0 +1,27 @@
+# 还款优惠与净资产轨迹交互（2026-10-04）
+
+## 还款优惠
+
+信用卡/贷款账户的快速还款，以及独立债务“还款”表单，提供“还款优惠（负数表示手续费）”字段。币种为付款账户原币；默认 0。正数减少实际扣款，负数增加实际扣款；欠款按本次本金减少。优惠不能超过还款金额。跨币种时仍填写欠款币种的减少金额，优惠仅作用于付款币种。
+
+例如还款 50，优惠 5.86420975，付款账户实际扣除 44.13579025，欠款减少 50；还款 30、输入 -2，则付款账户扣除 32，欠款减少 30。独立借出债务的收款、借贷本金操作和普通转账表单仍按各自现有手续费说明处理。
+
+前端直接翻转十进制字符串的符号，保留八位小数；提交时将优惠正数转换为既有 fee 负数、手续费负数转换为 fee 正数。金额未经过 JavaScript 浮点运算，不改变现有接口字段、金额规则或备份格式。已有 Transfer.fee 字段及数据库注释保持有效，无新增数据库迁移。
+
+快速记录同时显示本次优惠或手续费，撤回继续使用成对往来删除与历史重放，恢复双方余额。独立债务还款可在变化记录管理并删除。
+
+## 净资产轨迹
+
+点击图例中的“总资产”“总负债”“净资产”，可独立隐藏或恢复对应折线，纵轴范围随可见折线调整。隐藏全部时显示恢复提示；重新点击任何图例可恢复。显示选择仅影响当前页面图表，不改变资产统计、历史或备份。
+
+鼠标悬停图表时显示最接近日期的提示卡，包含日期及当前可见折线金额。点击图表支持触屏查看；聚焦后可使用左右方向键切换日期、Home/End 跳到首尾、Escape 关闭提示。提示金额使用原始十进制字符串格式化，绘图坐标仅作视觉近似。
+
+周/月日期间距按真实日期计算。汇率或估值不完整的日期保留断线，查看这些日期时明确提示总额不完整，不以零替代。少于两个完整日期时保留原有等待提示。
+
+## 验证
+
+- 52 项基础测试通过，包含优惠符号转换与精度、非均匀日期选择、缺失数据断线、三条独立图例及原始金额格式化。
+- 扩展快速记账真实 MySQL/REST 测试通过：信用卡和独立债务优惠、手续费、优惠超额拒绝、成对撤回，以及已有隐藏隔离、标记和 ZIP 恢复。
+- 临时账号页面验证：还款 50、优惠 5.87654321 后余额从 1000 变为 955.87654321；快速记录正确显示优惠；撤回恢复。独立债务还款 30、手续费 2 后付款余额为 968，欠款从 200 减至 170。
+- 图表验证：隐藏总负债后对应路径消失，提示仅显示可见折线；End 显示最后业务日期及精确总额；全部隐藏后可恢复净资产线。
+- 前后端类型检查与生产构建通过。测试账号退出并清理，未修改真实用户财务数据；docs 目录无截图。
diff --git a/update.md b/update.md
index 1c95a6d..e306637 100644
--- a/update.md
+++ b/update.md
@@ -90,4 +90,6 @@
 - ~~独立资产可以快速点击卡片却认是否计入总资产，与快速记账类似~~ — 已完成并验证：2026-10-04 16:00（UTC+8），见 docs/update-quick-entry-2026-10-04.md
 - ~~快速记账使用，减小卡片中不重要的信息，并缩小卡片和缩小间距，同时隐藏页面中不重要的信息和按钮，让快速记账更便捷~~ — 已完成并验证：2026-10-04 16:00（UTC+8），见 docs/update-quick-entry-2026-10-04.md
 - ~~快速记账的转账按钮 和快速记账显示在附近，不在显示在右边~~ — 已完成并验证：2026-10-04 16:00（UTC+8），见 docs/update-quick-entry-2026-10-04.md
-- ~~快速记账时，可以出现点击当天已完成记账的按钮，点击可以快速设置某个账号当天已完成记账，同时在快速记账中可以显示或隐藏当天已完成记账~~ — 已完成并验证：2026-10-04 16:00（UTC+8），见 docs/update-quick-entry-2026-10-04.md
\ No newline at end of file
+- ~~快速记账时，可以出现点击当天已完成记账的按钮，点击可以快速设置某个账号当天已完成记账，同时在快速记账中可以显示或隐藏当天已完成记账~~ — 已完成并验证：2026-10-04 16:00（UTC+8），见 docs/update-quick-entry-2026-10-04.md
+- ~~还款可以优惠功能（负数表示手续费）~~ — 已完成并验证：2026-10-04 22:18（UTC+8），见 docs/update-repayment-trend-2026-10-04.md
+- ~~净资产轨迹，可以设置隐藏某条折线，鼠标放线线可以查看当天数据~~ — 已完成并验证：2026-10-04 22:18（UTC+8），见 docs/update-repayment-trend-2026-10-04.md
\ No newline at end of file