diff --git a/Memory.md b/Memory.md
index 733559e..4a70c55 100644
--- a/Memory.md
+++ b/Memory.md
@@ -79,6 +79,15 @@
 - 新增累計盈虧指標：`cumulativePnlNative = floatingPnlNative + realizedPnlNative + accumulatedDividendsNative`、`cumulativePnlPercent = cumulativePnlNative / totalBuyCostNative * 100`。
 - SELL 交易的已實現盈虧計算從 CNY 基準改為 Native 基準，CNY 計算保留用於前端兼容展示。
 
+## Dashboard 流水下鑽明細與行內 CRUD (Task 41b)
+- 完成 Dashboard 流水下鑽功能，支持在資產列表中直接查看、修改和刪除歷史交易流水。
+- 在主行 `TableRow` 下方，根據 `expandedIds[pos.assetId]` 條件渲染第二個子行，使用 `<TableCell colSpan={8} className="p-0">` 確保子行佔滿整行寬度。
+- 構建流水明細次級表格：遍歷 `pos.transactions` 數組，表頭為「交易日期 | 類型 | 價格/數量 | 手續費 | 備註 | 操作」，精確渲染每筆交易的歷史數據。
+- 實裝 `UpdateTransactionDialog` 組件：「修改」按鈕打開彈窗並回顯該筆流水數據（數量、價格、手續費、幣種、執行時間），提交後調用 `updateTransaction` Action 並刷新頁面。
+- 實裝行內刪除功能：「刪除」按鈕彈出確認對話框，確認後調用 `deleteTransaction` Action 並刷新頁面。
+- 在 `portfolio.ts` 的 `TransactionRecord` 接口中補充 `id` 和 `fee` 字段，並在下發數據時包含完整的流水 ID，以支持行內 CRUD 操作。
+- UI 優化：為展開的子表格添加左側彩色邊框 (`border-l-4 border-primary/20`) 與左側縮進 (`ml-2`) 增強層級感；展開/收起按鈕文字根據狀態動態切換（「收起」/「展開」）。
+
 ## Dashboard 表格化基礎重構 (Task 41)
 - Dashboard 完成表格化基礎重構，徹底移除原有的卡片網格佈局，改用 shadcn/ui Table 組件構建高密度專業券商風格主表。
 - 實裝了基於 ID 的行展開狀態管理邏輯：`useState<Record<string, boolean>>` 控制每行的展開/收起狀態，點擊行或展開按鈕觸發 `toggleExpand`。
diff --git a/app/dashboard/page.tsx b/app/dashboard/page.tsx
index b6a289d..75e8948 100644
--- a/app/dashboard/page.tsx
+++ b/app/dashboard/page.tsx
@@ -1,6 +1,6 @@
 'use client';
 
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useTransition } from 'react';
 import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
 import {
   Table,
@@ -11,13 +11,24 @@ import {
   TableRow,
 } from '@/components/ui/table';
 import { Button } from '@/components/ui/button';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import { toast } from 'sonner';
 import { getPortfolioSummary } from '@/actions/portfolio';
 import { getAssets } from '@/actions/asset';
 import { formatQuantity, formatAmount } from '@/lib/formatters';
 import AllocationChart from '@/components/dashboard/allocation-chart';
 import { SyncButton } from '@/components/assets/sync-button';
 import { AddTransactionDialog } from '@/components/transactions/add-transaction-dialog';
-import { ChevronDown, ChevronUp, Plus, Edit3 } from 'lucide-react';
+import { UpdateTransactionDialog } from '@/components/transactions/update-transaction-dialog';
+import { deleteTransaction } from '@/actions/transaction';
+import { ChevronDown, ChevronUp, Plus, Edit3, Trash2 } from 'lucide-react';
 import Big from 'big.js';
 
 function getCurrencySymbol(currency: string): string {
@@ -64,6 +75,9 @@ export default function DashboardPage() {
   const [expandedIds, setExpandedIds] = useState<Record<string, boolean>>({});
   const [dialogOpen, setDialogOpen] = useState(false);
   const [selectedAssetId, setSelectedAssetId] = useState<string>('');
+  const [isPending, startTransition] = useTransition();
+  const [updateTarget, setUpdateTarget] = useState<any>(null);
+  const [deleteTarget, setDeleteTarget] = useState<any>(null);
 
   useEffect(() => {
     async function loadData() {
@@ -88,6 +102,27 @@ export default function DashboardPage() {
     setDialogOpen(true);
   };
 
+  const handleUpdate = (tx: any) => {
+    setUpdateTarget(tx);
+  };
+
+  function handleUpdateSubmit() {
+    setUpdateTarget(null);
+  }
+
+  function handleDelete(tx: any) {
+    startTransition(async () => {
+      const result = await deleteTransaction(tx.id);
+      if (result.success) {
+        toast.success('交易記錄已刪除');
+        setDeleteTarget(null);
+        window.location.reload();
+      } else if (result.error) {
+        toast.error(result.error);
+      }
+    });
+  }
+
   const formattedTotal = formatAmount(totalCnyValue);
   const formattedTotalPnl = formatAmount(totalPnlCny);
   const formattedUnrealized = formatAmount(unrealizedPnlCny);
@@ -214,65 +249,108 @@ export default function DashboardPage() {
                       </TableRow>
                       {isExpanded && (
                         <TableRow>
-                          <TableCell colSpan={8} className="bg-muted/30 p-4">
-                            <div className="space-y-2">
-                              <div className="flex items-center justify-between">
-                                <span className="text-sm font-medium text-muted-foreground">交易記錄</span>
-                                <Button
-                                  size="sm"
-                                  variant="outline"
-                                  className="h-7 px-2 text-xs"
-                                  onClick={(e) => {
-                                    e.stopPropagation();
-                                    handleOpenDialog(pos.assetId);
-                                  }}
-                                >
-                                  <Plus className="h-3 w-3 mr-1" />
-                                  新增記錄
-                                </Button>
+                          <TableCell colSpan={8} className="p-0">
+                            <div className="bg-muted/20 border-l-4 border-primary/20 p-3 ml-2">
+                              <div className="space-y-2">
+                                <div className="flex items-center justify-between pb-2 border-b border-border/50">
+                                  <span className="text-sm font-semibold text-foreground">流水明細</span>
+                                  <Button
+                                    size="sm"
+                                    variant="outline"
+                                    className="h-7 px-2 text-xs"
+                                    onClick={(e) => {
+                                      e.stopPropagation();
+                                      handleOpenDialog(pos.assetId);
+                                    }}
+                                  >
+                                    <Plus className="h-3 w-3 mr-1" />
+                                    新增記錄
+                                  </Button>
+                                </div>
+                                {pos.transactions && pos.transactions.length > 0 ? (
+                                  <Table>
+                                    <TableHeader>
+                                      <TableRow>
+                                        <TableHead>交易日期</TableHead>
+                                        <TableHead>類型</TableHead>
+                                        <TableHead className="text-right">價格/數量</TableHead>
+                                        <TableHead className="text-right">手續費</TableHead>
+                                        <TableHead>備註</TableHead>
+                                        <TableHead className="text-right w-[100px]">操作</TableHead>
+                                      </TableRow>
+                                    </TableHeader>
+                                    <TableBody>
+                                      {pos.transactions.map((tx: any) => {
+                                        const txDate = tx.executedAt
+                                          ? new Date(tx.executedAt).toLocaleString('zh-TW', {
+                                              year: 'numeric',
+                                              month: '2-digit',
+                                              day: '2-digit',
+                                              hour: '2-digit',
+                                              minute: '2-digit',
+                                            })
+                                          : '-';
+                                        return (
+                                          <TableRow key={tx.id} className="bg-muted/10">
+                                            <TableCell className="text-xs text-muted-foreground whitespace-nowrap">
+                                              {txDate}
+                                            </TableCell>
+                                            <TableCell>
+                                              <span className={`text-xs font-medium px-1.5 py-0.5 rounded ${
+                                                tx.txType === 'BUY' ? 'bg-red-100 text-red-700' :
+                                                tx.txType === 'SELL' ? 'bg-green-100 text-green-700' :
+                                                tx.txType === 'DIVIDEND' ? 'bg-blue-100 text-blue-700' :
+                                                tx.txType === 'AIRDROP' ? 'bg-purple-100 text-purple-700' :
+                                                'bg-gray-100 text-gray-700'
+                                              }`}>
+                                                {tx.txType}
+                                              </span>
+                                            </TableCell>
+                                            <TableCell className="text-right text-xs">
+                                              <div className="flex flex-col items-end">
+                                                <span>量: {tx.quantity}</span>
+                                                <span>價: {tx.price}</span>
+                                              </div>
+                                            </TableCell>
+                                            <TableCell className="text-right text-xs">{tx.fee || '0'}</TableCell>
+                                            <TableCell className="text-xs text-muted-foreground">-</TableCell>
+                                            <TableCell className="text-right">
+                                              <div className="flex items-center justify-end gap-1">
+                                                <Button
+                                                  size="sm"
+                                                  variant="ghost"
+                                                  className="h-6 px-1.5 text-xs"
+                                                  onClick={(e) => {
+                                                    e.stopPropagation();
+                                                    handleUpdate(tx);
+                                                  }}
+                                                >
+                                                  <Edit3 className="h-3 w-3 mr-0.5" />
+                                                  修改
+                                                </Button>
+                                                <Button
+                                                  size="sm"
+                                                  variant="ghost"
+                                                  className="h-6 px-1.5 text-xs text-red-500 hover:text-red-700 hover:bg-red-50"
+                                                  onClick={(e) => {
+                                                    e.stopPropagation();
+                                                    setDeleteTarget(tx);
+                                                  }}
+                                                >
+                                                  <Trash2 className="h-3 w-3 mr-0.5" />
+                                                  刪除
+                                                </Button>
+                                              </div>
+                                            </TableCell>
+                                          </TableRow>
+                                        );
+                                      })}
+                                    </TableBody>
+                                  </Table>
+                                ) : (
+                                  <p className="text-sm text-muted-foreground text-center py-3">暫無交易記錄</p>
+                                )}
                               </div>
-                              {pos.transactions && pos.transactions.length > 0 ? (
-                                <Table>
-                                  <TableHeader>
-                                    <TableRow>
-                                      <TableHead>類型</TableHead>
-                                      <TableHead className="text-right">數量</TableHead>
-                                      <TableHead className="text-right">價格</TableHead>
-                                      <TableHead className="text-right">手續費</TableHead>
-                                      <TableHead className="text-right">幣種</TableHead>
-                                      <TableHead className="text-right">日期</TableHead>
-                                    </TableRow>
-                                  </TableHeader>
-                                  <TableBody>
-                                    {pos.transactions.map((tx: any, idx: number) => {
-                                      const txDate = tx.executedAt
-                                        ? new Date(tx.executedAt).toLocaleString('zh-TW')
-                                        : '-';
-                                      return (
-                                        <TableRow key={idx}>
-                                          <TableCell>
-                                            <span className={`text-xs font-medium px-1.5 py-0.5 rounded ${
-                                              tx.txType === 'BUY' ? 'bg-red-100 text-red-700' :
-                                              tx.txType === 'SELL' ? 'bg-green-100 text-green-700' :
-                                              tx.txType === 'DIVIDEND' ? 'bg-blue-100 text-blue-700' :
-                                              'bg-gray-100 text-gray-700'
-                                            }`}>
-                                              {tx.txType}
-                                            </span>
-                                          </TableCell>
-                                          <TableCell className="text-right">{tx.quantity}</TableCell>
-                                          <TableCell className="text-right">{tx.price}</TableCell>
-                                          <TableCell className="text-right">{tx.fee || '0'}</TableCell>
-                                          <TableCell className="text-right">{tx.txCurrency}</TableCell>
-                                          <TableCell className="text-right text-xs text-muted-foreground">{txDate}</TableCell>
-                                        </TableRow>
-                                      );
-                                    })}
-                                  </TableBody>
-                                </Table>
-                              ) : (
-                                <p className="text-sm text-muted-foreground">暫無交易記錄</p>
-                              )}
                             </div>
                           </TableCell>
                         </TableRow>
@@ -301,6 +379,36 @@ export default function DashboardPage() {
         onOpenChange={setDialogOpen}
         defaultAssetId={selectedAssetId}
       />
+
+      <UpdateTransactionDialog
+        open={!!updateTarget}
+        onOpenChange={(open) => !open && setUpdateTarget(null)}
+        transaction={updateTarget}
+        onSuccess={handleUpdateSubmit}
+      />
+
+      <Dialog open={!!deleteTarget} onOpenChange={(open) => !open && setDeleteTarget(null)}>
+        <DialogContent className="sm:max-w-[400px]">
+          <DialogHeader>
+            <DialogTitle>確認刪除</DialogTitle>
+            <DialogDescription>
+              確定要刪除這筆交易記錄嗎？此操作不可撤銷。
+            </DialogDescription>
+          </DialogHeader>
+          <DialogFooter className="gap-2 sm:gap-0">
+            <Button variant="outline" onClick={() => setDeleteTarget(null)}>
+              取消
+            </Button>
+            <Button
+              variant="destructive"
+              onClick={() => deleteTarget && handleDelete(deleteTarget)}
+              disabled={isPending}
+            >
+              {isPending ? '刪除中...' : '刪除'}
+            </Button>
+          </DialogFooter>
+        </DialogContent>
+      </Dialog>
     </div>
   );
 }
diff --git a/src/actions/portfolio.ts b/src/actions/portfolio.ts
index abd5062..a8337e5 100644
--- a/src/actions/portfolio.ts
+++ b/src/actions/portfolio.ts
@@ -41,9 +41,11 @@ interface Position {
 }
 
 interface TransactionRecord {
+  id: string;
   txType: string;
   quantity: string;
   price: string;
+  fee: string;
   txCurrency: string;
   executedAt: Date | null;
 }
@@ -137,9 +139,11 @@ function getTodayInShanghai(): Date {
 export async function getPortfolioPositions(): Promise<Position[]> {
   const allTransactions = await db
     .select({
+      id: transactions.id,
       txType: transactions.txType,
       quantity: transactions.quantity,
       price: transactions.price,
+      fee: transactions.fee,
       exchangeRate: transactions.exchangeRate,
       txCurrency: transactions.txCurrency,
       assetId: transactions.assetId,
@@ -279,9 +283,11 @@ export async function getPortfolioPositions(): Promise<Position[]> {
     }
 
     holding.transactions.push({
+      id: tx.id,
       txType: tx.txType,
       quantity: tx.quantity,
       price: tx.price,
+      fee: tx.fee,
       txCurrency: tx.txCurrency,
       executedAt: tx.executedAt,
     });
diff --git a/src/components/transactions/update-transaction-dialog.tsx b/src/components/transactions/update-transaction-dialog.tsx
new file mode 100644
index 0000000..cb641d8
--- /dev/null
+++ b/src/components/transactions/update-transaction-dialog.tsx
@@ -0,0 +1,211 @@
+'use client';
+
+import { useState, useTransition } from 'react';
+import { useForm } from 'react-hook-form';
+import { zodResolver } from '@hookform/resolvers/zod';
+import { z } from 'zod';
+import {
+  Dialog,
+  DialogContent,
+  DialogDescription,
+  DialogFooter,
+  DialogHeader,
+  DialogTitle,
+} from '@/components/ui/dialog';
+import {
+  Form,
+  FormControl,
+  FormField,
+  FormItem,
+  FormLabel,
+  FormMessage,
+} from '@/components/ui/form';
+import { Input } from '@/components/ui/input';
+import {
+  Select,
+  SelectContent,
+  SelectItem,
+  SelectTrigger,
+  SelectValue,
+} from '@/components/ui/select';
+import { Button } from '@/components/ui/button';
+import { toast } from 'sonner';
+import { updateTransaction } from '@/actions/transaction';
+
+const updateTransactionSchema = z.object({
+  quantity: z.string().regex(/^-?\d+(\.\d+)?$/, '数量必须是数字'),
+  price: z.string().regex(/^-?\d+(\.\d+)?$/, '价格必须是数字'),
+  fee: z.string().regex(/^-?\d+(\.\d+)?$/, '手续费必须是数字').default('0'),
+  txCurrency: z.string().min(1, '交易币种不能为空'),
+  executedAt: z.string(),
+});
+
+type UpdateForm = z.infer<typeof updateTransactionSchema>;
+
+interface UpdateTransactionDialogProps {
+  open: boolean;
+  onOpenChange: (open: boolean) => void;
+  transaction: {
+    id: string;
+    txType: string;
+    quantity: string;
+    price: string;
+    fee: string;
+    txCurrency: string;
+    executedAt: Date | null;
+  } | null;
+  onSuccess: () => void;
+}
+
+export function UpdateTransactionDialog({
+  open,
+  onOpenChange,
+  transaction,
+  onSuccess,
+}: UpdateTransactionDialogProps) {
+  const [isPending, startTransition] = useTransition();
+
+  const form = useForm<UpdateForm>({
+    resolver: zodResolver(updateTransactionSchema),
+    defaultValues: {
+      quantity: '',
+      price: '',
+      fee: '0',
+      txCurrency: 'USD',
+      executedAt: '',
+    },
+  });
+
+  useState(() => {
+    if (transaction && open) {
+      form.reset({
+        quantity: transaction.quantity.toString(),
+        price: transaction.price.toString(),
+        fee: transaction.fee.toString(),
+        txCurrency: transaction.txCurrency,
+        executedAt: transaction.executedAt
+          ? new Date(transaction.executedAt).toISOString().slice(0, 16)
+          : '',
+      });
+    }
+  });
+
+  function handleSubmit(values: UpdateForm) {
+    if (!transaction) return;
+    startTransition(async () => {
+      const result = await updateTransaction({
+        id: transaction.id,
+        quantity: values.quantity,
+        price: values.price,
+        fee: values.fee,
+        txCurrency: values.txCurrency,
+        executedAt: new Date(values.executedAt),
+      });
+      if (result.success) {
+        toast.success('交易记录已更新');
+        onOpenChange(false);
+        onSuccess();
+      } else if (result.error) {
+        toast.error(result.error);
+      }
+    });
+  }
+
+  return (
+    <Dialog open={open} onOpenChange={onOpenChange}>
+      <DialogContent className="sm:max-w-[500px]">
+        <DialogHeader>
+          <DialogTitle>編輯交易</DialogTitle>
+          <DialogDescription>修改交易記錄詳情</DialogDescription>
+        </DialogHeader>
+        <Form {...form}>
+          <form onSubmit={form.handleSubmit(handleSubmit)} className="space-y-4">
+            <div className="grid grid-cols-2 gap-4">
+              <FormField
+                control={form.control}
+                name="quantity"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>數量</FormLabel>
+                    <FormControl>
+                      <Input type="text" {...field} />
+                    </FormControl>
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+              <FormField
+                control={form.control}
+                name="price"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>價格</FormLabel>
+                    <FormControl>
+                      <Input type="text" {...field} />
+                    </FormControl>
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+            </div>
+            <div className="grid grid-cols-2 gap-4">
+              <FormField
+                control={form.control}
+                name="fee"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>手續費</FormLabel>
+                    <FormControl>
+                      <Input type="text" {...field} />
+                    </FormControl>
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+              <FormField
+                control={form.control}
+                name="txCurrency"
+                render={({ field }) => (
+                  <FormItem>
+                    <FormLabel>交易幣種</FormLabel>
+                    <Select onValueChange={field.onChange} value={field.value}>
+                      <FormControl>
+                        <SelectTrigger>
+                          <SelectValue placeholder="選擇幣種" />
+                        </SelectTrigger>
+                      </FormControl>
+                      <SelectContent>
+                        <SelectItem value="USD">USD</SelectItem>
+                        <SelectItem value="CNY">CNY</SelectItem>
+                        <SelectItem value="HKD">HKD</SelectItem>
+                      </SelectContent>
+                    </Select>
+                    <FormMessage />
+                  </FormItem>
+                )}
+              />
+            </div>
+            <FormField
+              control={form.control}
+              name="executedAt"
+              render={({ field }) => (
+                <FormItem>
+                  <FormLabel>執行時間</FormLabel>
+                  <FormControl>
+                    <Input type="datetime-local" {...field} />
+                  </FormControl>
+                  <FormMessage />
+                </FormItem>
+              )}
+            />
+            <DialogFooter>
+              <Button type="submit" disabled={isPending}>
+                {isPending ? '保存中...' : '保存'}
+              </Button>
+            </DialogFooter>
+          </form>
+        </Form>
+      </DialogContent>
+    </Dialog>
+  );
+}