diff --git a/core/frontend/src/App.tsx b/core/frontend/src/App.tsx
index 40212d4..5eb5115 100644
--- a/core/frontend/src/App.tsx
+++ b/core/frontend/src/App.tsx
@@ -911,6 +911,7 @@ export function App() {
             projects={projects}
             team={currentTeam}
             onRecharge={(amount, bonusPoints) => action(() => api.recharge({ amount, bonus_points: bonusPoints }), "充值成功")}
+            onNotify={(type, text) => setNotice({ type, text })}
           />
         );
       case "team":
diff --git a/core/frontend/src/design-restraint.css b/core/frontend/src/design-restraint.css
index edc57cc..9f0fa04 100644
--- a/core/frontend/src/design-restraint.css
+++ b/core/frontend/src/design-restraint.css
@@ -766,6 +766,7 @@ main { position: relative; background: var(--background-base); min-width: 0; }
 .field-label { font-size: 13px; font-weight: 500; color: var(--accent-black); }
 .field-label .req { color: var(--accent-crimson); margin-left: 2px; }
 .field-hint { font-size: 12px; color: var(--black-alpha-48); }
+.field-hint.is-error { color: var(--accent-crimson); }
 .input, .textarea, .select {
   height: 36px;
   padding: 0 14px;
@@ -783,6 +784,10 @@ main { position: relative; background: var(--background-base); min-width: 0; }
   border-color: var(--heat-40);
   box-shadow: inset 0 0 0 1px var(--heat-40);
 }
+.input.is-invalid, .textarea.is-invalid, .select.is-invalid {
+  border-color: var(--accent-crimson);
+  box-shadow: inset 0 0 0 1px var(--accent-crimson);
+}
 .input::placeholder, .textarea::placeholder { color: var(--black-alpha-48); }
 .input:disabled, .textarea:disabled, .select:disabled {
   background: var(--black-alpha-5);
diff --git a/core/frontend/src/routes/account.tsx b/core/frontend/src/routes/account.tsx
index 9dfbbb3..492c125 100644
--- a/core/frontend/src/routes/account.tsx
+++ b/core/frontend/src/routes/account.tsx
@@ -59,6 +59,7 @@ const RECHARGE: Array<{ amt: number; gift: string; bonus: boolean; bonusAmt: num
   { amt: 1000, gift: "+800 积分赠送", bonus: true, bonusAmt: 800 },
   { amt: 3000, gift: "+3000 积分赠送", bonus: true, bonusAmt: 3000 }
 ];
+const MIN_RECHARGE_AMOUNT = 50;
 
 const STAGES: Array<{ k: string; color: string; bucket: keyof BillingTrend["by_stage"] }> = [
   { k: "视频片段(Seedance)", color: "var(--heat)", bucket: "video" },
@@ -113,12 +114,13 @@ function TopupModal({ open, channel, amount, bonus, rate, close, onDone }: {
   );
 }
 
-export function AccountPage({ billing, projects, team, onRecharge }: {
+export function AccountPage({ billing, projects, team, onRecharge, onNotify }: {
   billing: BillingSummary | null;
   projects: Project[];
   // team prop 用于读取团队级月限额(与团队管理页保持同一来源 · #14)
   team?: Team | null;
   onRecharge: (amount: number, bonus: number) => void | Promise<unknown>;
+  onNotify: (type: "success" | "error" | "info", text: string) => void;
 }) {
   const [tab, setTab] = useState<Tab>("overview");
   // 积分汇率(积分/¥):预览换算与后端 recharge 同源,汇率改配后不至于「预览 ×10 实到 ×N」
@@ -175,11 +177,29 @@ export function AccountPage({ billing, projects, team, onRecharge }: {
   const [billJump, setBillJump] = useState("");
 
   const selectedCard = RECHARGE.find((item) => item.amt === recharge);
-  const effectiveAmount = Number(customAmt) > 0 ? Number(customAmt) : recharge;
-  const effectiveBonus = Number(customAmt) > 0 ? 0 : selectedCard?.bonusAmt || 0;
+  const customAmount = Number(customAmt);
+  const hasCustomAmount = customAmt.length > 0;
+  const customAmountIsValid = !hasCustomAmount || (Number.isFinite(customAmount) && customAmount >= MIN_RECHARGE_AMOUNT);
+  const effectiveAmount = hasCustomAmount ? customAmount : recharge;
+  const effectiveBonus = hasCustomAmount ? 0 : selectedCard?.bonusAmt || 0;
   const setCustomIntegerAmount = (value: string) => setCustomAmt(value.replace(/\D/g, "").replace(/^0+/, ""));
 
+  function validateCustomAmount() {
+    if (customAmountIsValid) return true;
+    onNotify("error", `最小充值金额为 ${MIN_RECHARGE_AMOUNT} 元`);
+    return false;
+  }
+
+  function openTopup(channel: "wechat" | "alipay") {
+    if (!validateCustomAmount()) return;
+    setTopupChannel(channel);
+  }
+
   async function submitRecharge() {
+    if (!validateCustomAmount()) {
+      setTopupChannel(null);
+      return;
+    }
     if (effectiveAmount <= 0) return;
     await onRecharge(effectiveAmount, effectiveBonus); // 父级 action 成功后弹全局「充值成功」toast
     setTopupChannel(null);
@@ -319,13 +339,25 @@ export function AccountPage({ billing, projects, team, onRecharge }: {
           </div>
           <div className="pay-row">
             <div className="pay-title">自定义金额</div>
-            <input className="input" placeholder="最低 ¥50,可输入任意金额" type="text" inputMode="numeric" pattern="[0-9]*" value={customAmt} onChange={(event) => setCustomIntegerAmount(event.target.value)} />
+            <input
+              className={`input${!customAmountIsValid ? " is-invalid" : ""}`}
+              placeholder="最低 ¥50,可输入任意金额"
+              type="number"
+              min={MIN_RECHARGE_AMOUNT}
+              step="1"
+              inputMode="numeric"
+              value={customAmt}
+              aria-invalid={!customAmountIsValid}
+              aria-describedby="custom-recharge-error"
+              onChange={(event) => setCustomIntegerAmount(event.target.value)}
+            />
+            {!customAmountIsValid && <div className="field-hint is-error" id="custom-recharge-error" role="alert">充值金额不能低于 {MIN_RECHARGE_AMOUNT} 元</div>}
             <div className="pay-btn-row">
-              <button className="btn pay-method-btn pay-wechat" type="button" aria-label="微信支付" onClick={() => setTopupChannel("wechat")}>
+              <button className="btn pay-method-btn pay-wechat" type="button" aria-label="微信支付" onClick={() => openTopup("wechat")}>
                 <span className="pay-logo" aria-hidden="true"><img src="/assets/pay-wechat.png" alt="" /></span>
                 微信支付
               </button>
-              <button className="btn pay-method-btn pay-alipay" type="button" aria-label="支付宝" onClick={() => setTopupChannel("alipay")}>
+              <button className="btn pay-method-btn pay-alipay" type="button" aria-label="支付宝" onClick={() => openTopup("alipay")}>
                 <span className="pay-logo" aria-hidden="true"><img src="/assets/pay-alipay.png" alt="" /></span>
                 支付宝
               </button>