diff --git a/db.mjs b/db.mjs
index 92459c0..832f5a2 100644
--- a/db.mjs
+++ b/db.mjs
@@ -359,6 +359,18 @@ export async function migrateSchema(pool) {
     );
   }
 
+  if (!(await columnExists(pool, 'h5_users', 'low_balance_gift_eligible'))) {
+    await pool.query(
+      `ALTER TABLE h5_users ADD COLUMN low_balance_gift_eligible TINYINT(1) NOT NULL DEFAULT 0 AFTER signup_source`,
+    );
+  }
+
+  if (!(await columnExists(pool, 'h5_users', 'low_balance_gift_granted_at'))) {
+    await pool.query(
+      `ALTER TABLE h5_users ADD COLUMN low_balance_gift_granted_at BIGINT NULL AFTER low_balance_gift_eligible`,
+    );
+  }
+
   if (!(await columnExists(pool, 'h5_user_sessions', 'goosed_node'))) {
     await pool.query(
       `ALTER TABLE h5_user_sessions ADD COLUMN goosed_node TINYINT UNSIGNED NOT NULL DEFAULT 0`,
diff --git a/schema.sql b/schema.sql
index 485f37f..9db7a7f 100644
--- a/schema.sql
+++ b/schema.sql
@@ -11,6 +11,8 @@ CREATE TABLE IF NOT EXISTS h5_users (
   status ENUM('active', 'suspended', 'disabled') NOT NULL DEFAULT 'active',
   plan_type VARCHAR(32) NOT NULL DEFAULT 'free',
   workspace_root VARCHAR(512) NOT NULL,
+  low_balance_gift_eligible TINYINT(1) NOT NULL DEFAULT 0,
+  low_balance_gift_granted_at BIGINT NULL,
   created_at BIGINT NOT NULL,
   updated_at BIGINT NOT NULL,
   UNIQUE KEY uq_h5_users_slug (slug),
diff --git a/user-auth.mjs b/user-auth.mjs
index 98290a3..979f231 100644
--- a/user-auth.mjs
+++ b/user-auth.mjs
@@ -129,6 +129,8 @@ export function createUserAuth(pool, options = {}) {
   const publicBaseUrl = resolvePublicBaseUrl(env);
   const skillCatalog = listPlatformSkillCatalog(h5Root);
   const defaultSignupBalanceCents = Number(options.defaultSignupBalanceCents ?? 500);
+  const lowBalanceGiftThresholdCents = Number(options.lowBalanceGiftThresholdCents ?? 100);
+  const lowBalanceGiftAmountCents = Number(options.lowBalanceGiftAmountCents ?? 1000);
   const sessionTtlMs = Number(options.sessionTtlMs ?? 7 * 24 * 60 * 60 * 1000);
   const loginMaxFailures = Number(options.loginMaxFailures ?? 5);
   const loginFailureWindowMs = Number(options.loginFailureWindowMs ?? 5 * 60 * 1000);
@@ -340,6 +342,72 @@ export function createUserAuth(pool, options = {}) {
     );
   };
 
+  const shouldEnableLowBalanceGift = ({ isAdmin = false, initialBalanceCents }) => {
+    return !isAdmin && Number(initialBalanceCents) === defaultSignupBalanceCents && defaultSignupBalanceCents > 0;
+  };
+
+  const grantLowBalanceGiftIfNeeded = async (conn, { userId, currentBalance, nextBalance, now }) => {
+    if (lowBalanceGiftAmountCents <= 0 || lowBalanceGiftThresholdCents < 0 || nextBalance > lowBalanceGiftThresholdCents) {
+      return { gifted: false, balanceAfter: nextBalance };
+    }
+
+    const [rows] = await conn.query(
+      `SELECT low_balance_gift_eligible, low_balance_gift_granted_at
+       FROM h5_users
+       WHERE id = ?
+       FOR UPDATE`,
+      [userId],
+    );
+    const user = rows[0];
+    if (!user || !Boolean(user.low_balance_gift_eligible) || user.low_balance_gift_granted_at != null) {
+      return { gifted: false, balanceAfter: nextBalance };
+    }
+
+    const giftedBalance = nextBalance + lowBalanceGiftAmountCents;
+    await conn.query(
+      `UPDATE h5_user_wallets
+       SET balance_cents = ?, updated_at = ?
+       WHERE user_id = ?`,
+      [giftedBalance, now, userId],
+    );
+    await conn.query(
+      `UPDATE h5_users
+       SET low_balance_gift_eligible = 0,
+           low_balance_gift_granted_at = ?,
+           status = CASE WHEN status = 'suspended' THEN 'active' ELSE status END,
+           updated_at = ?
+       WHERE id = ?`,
+      [now, now, userId],
+    );
+    await conn.query(
+      `INSERT INTO h5_billing_ledger
+       (user_id, type, amount_cents, tokens, note, operator_id, created_at)
+       VALUES (?, 'adjust', ?, 0, ?, NULL, ?)`,
+      [userId, lowBalanceGiftAmountCents, '新用户低余额自动赠送', now],
+    );
+    await conn.query(
+      `INSERT INTO h5_user_notifications
+       (id, user_id, channel, notification_type, title, body, data_json, status, read_at, created_at, updated_at)
+       VALUES (?, ?, 'web', 'low_balance_gift', ?, ?, ?, 'unread', NULL, ?, ?)`,
+      [
+        crypto.randomUUID(),
+        userId,
+        '新用户额度已自动补送',
+        `检测到你的余额已低于 ¥${(lowBalanceGiftThresholdCents / 100).toFixed(2)}，系统已自动赠送 ¥${(lowBalanceGiftAmountCents / 100).toFixed(2)} 新用户额度。本福利仅可领取一次。`,
+        JSON.stringify({
+          triggerBalanceCents: nextBalance,
+          previousBalanceCents: currentBalance,
+          giftAmountCents: lowBalanceGiftAmountCents,
+          thresholdCents: lowBalanceGiftThresholdCents,
+        }),
+        now,
+        now,
+      ],
+    );
+
+    return { gifted: true, balanceAfter: giftedBalance };
+  };
+
   const register = async ({ username, password, displayName, email }) => {
     const normalized = normalizeUsername(username);
     if (!isValidUsername(normalized)) {
@@ -364,8 +432,9 @@ export function createUserAuth(pool, options = {}) {
       await conn.query(
         `INSERT INTO h5_users
          (id, username, slug, email, display_name, salt, password_hash, password_algorithm,
-          role, status, plan_type, workspace_root, created_at, updated_at)
-         VALUES (?, ?, ?, ?, ?, ?, ?, ?, 'user', 'active', 'free', ?, ?, ?)`,
+          role, status, plan_type, workspace_root, low_balance_gift_eligible, low_balance_gift_granted_at,
+          created_at, updated_at)
+         VALUES (?, ?, ?, ?, ?, ?, ?, ?, 'user', 'active', 'free', ?, 1, NULL, ?, ?)`,
         [
           userId,
           normalized,
@@ -815,13 +884,15 @@ export function createUserAuth(pool, options = {}) {
     const now = Date.now();
 
     const conn = await pool.getConnection();
+    const initialBalanceCents = Number(balanceCents ?? defaultSignupBalanceCents);
     try {
       await conn.beginTransaction();
       await conn.query(
         `INSERT INTO h5_users
          (id, username, slug, email, display_name, salt, password_hash, password_algorithm,
-          role, status, plan_type, workspace_root, created_at, updated_at)
-         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 'active', 'free', ?, ?, ?)`,
+          role, status, plan_type, workspace_root, low_balance_gift_eligible, low_balance_gift_granted_at,
+          created_at, updated_at)
+         VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, 'active', 'free', ?, ?, NULL, ?, ?)`,
         [
           userId,
           normalized,
@@ -833,6 +904,7 @@ export function createUserAuth(pool, options = {}) {
           passwordAlgorithm,
           isAdmin ? 'admin' : 'user',
           root,
+          shouldEnableLowBalanceGift({ isAdmin, initialBalanceCents }) ? 1 : 0,
           now,
           now,
         ],
@@ -840,7 +912,7 @@ export function createUserAuth(pool, options = {}) {
       await conn.query(
         `INSERT INTO h5_user_wallets (user_id, balance_cents, tokens_used, updated_at)
          VALUES (?, ?, 0, ?)`,
-        [userId, Number(balanceCents ?? defaultSignupBalanceCents), now],
+        [userId, initialBalanceCents, now],
       );
       await conn.query(
         `INSERT INTO h5_user_path_grants (user_id, path, mode) VALUES (?, ?, 'readwrite')`,
@@ -1315,7 +1387,11 @@ export function createUserAuth(pool, options = {}) {
       let tokensUsedAfter = null;
       if (costCents > 0) {
         const [walletRows] = await conn.query(
-          `SELECT balance_cents, tokens_used FROM h5_user_wallets WHERE user_id = ? FOR UPDATE`,
+          `SELECT w.balance_cents, w.tokens_used, u.status
+           FROM h5_user_wallets w
+           JOIN h5_users u ON u.id = w.user_id
+           WHERE w.user_id = ?
+           FOR UPDATE`,
           [userId],
         );
         const wallet = walletRows[0];
@@ -1366,7 +1442,15 @@ export function createUserAuth(pool, options = {}) {
           ],
         );
 
-        if (nextBalance <= 0) {
+        const lowBalanceGift = await grantLowBalanceGiftIfNeeded(conn, {
+          userId,
+          currentBalance,
+          nextBalance,
+          now,
+        });
+        balanceAfter = lowBalanceGift.balanceAfter;
+
+        if (balanceAfter <= 0) {
           await conn.query(`UPDATE h5_users SET status = 'suspended', updated_at = ? WHERE id = ?`, [
             now,
             userId,
@@ -2425,8 +2509,9 @@ export function createUserAuth(pool, options = {}) {
       await conn.query(
         `INSERT INTO h5_users
          (id, username, slug, email, display_name, salt, password_hash, password_algorithm,
-          role, status, plan_type, workspace_root, signup_source, created_at, updated_at)
-         VALUES (?, ?, ?, NULL, ?, ?, ?, ?, 'user', 'active', 'free', ?, 'wechat', ?, ?)`,
+          role, status, plan_type, workspace_root, signup_source, low_balance_gift_eligible,
+          low_balance_gift_granted_at, created_at, updated_at)
+         VALUES (?, ?, ?, NULL, ?, ?, ?, ?, 'user', 'active', 'free', ?, 'wechat', 1, NULL, ?, ?)`,
         [
           userId,
           normalized,
diff --git a/user-auth.test.mjs b/user-auth.test.mjs
index a0bc16e..c547215 100644
--- a/user-auth.test.mjs
+++ b/user-auth.test.mjs
@@ -431,6 +431,130 @@ test('purchaseSpaceQuota deducts balance and increases quota', async () => {
   assert.equal(result.quota.availableBytes, 15 * 1024 * 1024 - 1024 - 2048);
 });
 
+test('billSessionUsage auto gifts low-balance bonus once for eligible new users', async () => {
+  const userRow = {
+    id: 'user-3',
+    username: 'bonus_user',
+    slug: 'bonus_user',
+    email: 'bonus@example.com',
+    display_name: 'Bonus User',
+    role: 'user',
+    status: 'active',
+    plan_type: 'free',
+    workspace_root: '/tmp/bonus-user',
+    balance_cents: 150,
+    tokens_used: 0,
+    spent_cents: 0,
+  };
+  const stateBySession = new Map();
+  let walletBalance = 150;
+  let tokensUsed = 0;
+  let lowBalanceGiftEligible = 1;
+  let lowBalanceGiftGrantedAt = null;
+  let ledgerAdjustCount = 0;
+  let notificationTypes = [];
+
+  const pool = {
+    async query(sql) {
+      if (sql.includes('FROM h5_users u') && sql.includes('WHERE u.id = ?')) {
+        return [[{ ...userRow, balance_cents: walletBalance, tokens_used: tokensUsed }]];
+      }
+      throw new Error(`unexpected pool query: ${sql}`);
+    },
+    async getConnection() {
+      return {
+        async beginTransaction() {},
+        async commit() {},
+        async rollback() {},
+        release() {},
+        async query(sql, params = []) {
+          if (sql.includes('SELECT cost_cents FROM h5_usage_records WHERE request_id = ? LIMIT 1')) return [[]];
+          if (sql.includes('INSERT INTO h5_session_billing_state') && sql.includes('agent_session_id = agent_session_id')) {
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('FROM h5_session_billing_state') && sql.includes('FOR UPDATE')) {
+            const row = stateBySession.get(params[0]);
+            return [row ? [row] : []];
+          }
+          if (sql.includes('INSERT INTO h5_session_billing_state') && sql.includes('ON DUPLICATE KEY UPDATE')) {
+            stateBySession.set(params[0], {
+              last_accumulated_cost: params[2],
+              last_input_tokens: params[3],
+              last_output_tokens: params[4],
+            });
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('SELECT w.balance_cents, w.tokens_used, u.status')) {
+            return [[{ balance_cents: walletBalance, tokens_used: tokensUsed, status: userRow.status }]];
+          }
+          if (sql.includes('UPDATE h5_user_wallets') && sql.includes('tokens_used = tokens_used + ?')) {
+            walletBalance = params[0];
+            tokensUsed += params[1];
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('INSERT INTO h5_usage_records')) return [{ affectedRows: 1 }, []];
+          if (sql.includes("INSERT INTO h5_billing_ledger") && sql.includes("'deduct'")) return [{ affectedRows: 1 }, []];
+          if (sql.includes('SELECT low_balance_gift_eligible, low_balance_gift_granted_at')) {
+            return [[{
+              low_balance_gift_eligible: lowBalanceGiftEligible,
+              low_balance_gift_granted_at: lowBalanceGiftGrantedAt,
+            }]];
+          }
+          if (sql.includes('UPDATE h5_user_wallets') && sql.includes('SET balance_cents = ?, updated_at = ?')) {
+            walletBalance = params[0];
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('UPDATE h5_users') && sql.includes('low_balance_gift_eligible = 0')) {
+            lowBalanceGiftEligible = 0;
+            lowBalanceGiftGrantedAt = params[0];
+            userRow.status = 'active';
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes("INSERT INTO h5_billing_ledger") && sql.includes("'adjust'")) {
+            ledgerAdjustCount += 1;
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('INSERT INTO h5_user_notifications')) {
+            notificationTypes.push('low_balance_gift');
+            return [{ affectedRows: 1 }, []];
+          }
+          if (sql.includes('UPDATE h5_users SET status = \'suspended\'')) {
+            userRow.status = 'suspended';
+            return [{ affectedRows: 1 }, []];
+          }
+          throw new Error(`unexpected connection query: ${sql}`);
+        },
+      };
+    },
+  };
+
+  const auth = createUserAuth(pool, { persistSessions: false });
+
+  const first = await auth.billSessionUsage(
+    userRow.id,
+    'session-bonus-1',
+    { accumulatedOutputTokens: 10_000 },
+    'req-bonus-1',
+  );
+  assert.equal(first.ok, true);
+  assert.equal(first.costCents, 60);
+  assert.equal(first.balanceCents, 1090);
+  assert.equal(ledgerAdjustCount, 1);
+  assert.deepEqual(notificationTypes, ['low_balance_gift']);
+
+  const second = await auth.billSessionUsage(
+    userRow.id,
+    'session-bonus-2',
+    { accumulatedOutputTokens: 10_000 },
+    'req-bonus-2',
+  );
+  assert.equal(second.ok, true);
+  assert.equal(second.costCents, 60);
+  assert.equal(second.balanceCents, 1030);
+  assert.equal(ledgerAdjustCount, 1);
+  assert.deepEqual(notificationTypes, ['low_balance_gift']);
+});
+
 test('updateUser rejects quota smaller than occupied bytes', async () => {
   const userRow = {
     id: 'user-3',