diff --git a/app/usage.test.js b/app/usage.test.js
index aa79008..21655fc 100644
--- a/app/usage.test.js
+++ b/app/usage.test.js
@@ -196,6 +196,25 @@ describe('resolveRemainingPercent', () => {
     assert.match(pct.reason, /無上限/);
   });
 
+  it('returns null percent for non-finite or non-positive quota limits', () => {
+    for (const limit of [0, -5, Infinity, NaN, undefined]) {
+      const pct = resolveRemainingPercent({ available: true, used: 0, limit, remaining: limit, currency: 'USD' }, null);
+      assert.equal(pct.percent, null, `quota.limit=${limit} 應算不出百分比`);
+    }
+  });
+
+  it('returns null percent for non-finite or non-positive rate limits', () => {
+    for (const limit of [0, -1, Infinity, NaN]) {
+      const pct = resolveRemainingPercent({ available: false, reason: 'x' }, { hasData: true, remaining: limit, limit, kind: 'tokens' });
+      assert.equal(pct.percent, null, `rate.limit=${limit} 應算不出百分比`);
+    }
+  });
+
+  it('returns null percent when limit is finite but remaining is non-finite', () => {
+    const pct = resolveRemainingPercent({ available: true, used: 0, limit: 100, remaining: Infinity, currency: 'USD' }, null);
+    assert.equal(pct.percent, null);
+  });
+
   it('does not divide by zero when quota.limit is 0', () => {
     const pct = resolveRemainingPercent({ available: true, used: 5, limit: 0, currency: 'USD' }, { hasData: false });
     assert.equal(pct.percent, null); // limit > 0 守衛擋掉除以零
@@ -253,4 +272,21 @@ describe('formatUsageStatsLine', () => {
     assert.doesNotMatch(line, /NaN/);
     assert.match(line, /剩餘可用: 無法計算/);
   });
+
+  it('does not output Infinity/NaN/negative percent for invalid quota numbers', () => {
+    const ownUsage = { calls: 1, promptTokens: 1, completionTokens: 1, totalTokens: 2 };
+    for (const limit of [Infinity, 0, -5, NaN]) {
+      const line = formatUsageStatsLine('openai', 'm', ownUsage, { available: true, used: 0, limit, remaining: limit, currency: 'USD' }, null);
+      assert.doesNotMatch(line, /NaN|Infinity|-\d+%/);
+      assert.match(line, /剩餘可用: 無法計算/);
+    }
+  });
+
+  it('falls back to a valid rate percent when only the quota limit is invalid', () => {
+    const ownUsage = { calls: 1, promptTokens: 1, completionTokens: 1, totalTokens: 2 };
+    const line = formatUsageStatsLine('openai', 'm', ownUsage,
+      { available: true, used: 0, limit: Infinity, currency: 'USD' },          // quota 無效
+      { hasData: true, remaining: 150000, limit: 200000, kind: 'tokens' });     // rate 有效 → 75%
+    assert.match(line, /剩餘可用: 75%（速率配額/);
+  });
 });