diff --git a/ai_trade/kis_client.py b/ai_trade/kis_client.py
index 5492360..84edb61 100644
--- a/ai_trade/kis_client.py
+++ b/ai_trade/kis_client.py
@@ -38,6 +38,7 @@ class KISClient:
         self._client = httpx.AsyncClient(timeout=timeout)
         self._token_cache: tuple[str, float] | None = None  # (token, file_mtime)
         self._last_throttle_at = 0.0
+        self._throttle_lock = asyncio.Lock()
 
     async def close(self) -> None:
         await self._client.aclose()
@@ -56,10 +57,13 @@ class KISClient:
         return token
 
     async def _throttle(self) -> None:
-        elapsed = time.monotonic() - self._last_throttle_at
-        if elapsed < _THROTTLE_INTERVAL:
-            await asyncio.sleep(_THROTTLE_INTERVAL - elapsed)
-        self._last_throttle_at = time.monotonic()
+        # F2: Lock으로 직렬화. 없으면 asyncio.gather 동시 호출 시 race로
+        # 같은 elapsed 계산 후 동시에 깨어나 KIS 초당 2회(EGW00201) 위반.
+        async with self._throttle_lock:
+            elapsed = time.monotonic() - self._last_throttle_at
+            if elapsed < _THROTTLE_INTERVAL:
+                await asyncio.sleep(_THROTTLE_INTERVAL - elapsed)
+            self._last_throttle_at = time.monotonic()
 
     def _common_headers(self, tr_id: str) -> dict[str, str]:
         token = self._read_v1_token()
diff --git a/ai_trade/tests/test_kis_client.py b/ai_trade/tests/test_kis_client.py
index 125af6e..7d17bff 100644
--- a/ai_trade/tests/test_kis_client.py
+++ b/ai_trade/tests/test_kis_client.py
@@ -1,5 +1,7 @@
 """Tests for KISClient (REST)."""
+import asyncio
 import json
+import time as time_module
 from pathlib import Path
 
 import httpx
@@ -159,3 +161,30 @@ async def test_get_daily_ohlcv_returns_60_bars(kis_client_factory):
         assert "datetime" in bars[0]
     finally:
         await client.close()
+
+
+@respx.mock
+async def test_throttle_serializes_concurrent_gather(kis_client_factory):
+    """F2 — 5개 동시 요청이 asyncio.gather로 들어와도 0.5초 간격으로 직렬화.
+
+    초당 2회 = 0.5초 간격. 5개 요청 시 최소 (5-1)*0.5 = 2.0초.
+    Lock 없으면 race condition으로 거의 동시에 나가 0.5초대로 끝남.
+    """
+    sample = {"output2": []}
+    respx.get(
+        "https://openapivts.koreainvestment.com:29443"
+        "/uapi/domestic-stock/v1/quotations/inquire-time-itemchartprice"
+    ).mock(return_value=httpx.Response(200, json=sample))
+
+    client = kis_client_factory()
+    try:
+        start = time_module.monotonic()
+        await asyncio.gather(*[client.get_minute_ohlcv(f"00593{i}") for i in range(5)])
+        elapsed = time_module.monotonic() - start
+        # 5 throttle = 최소 (5-1)*0.5 = 2.0s, tolerance 0.3s
+        assert elapsed >= 1.7, (
+            f"throttle race condition: 5 concurrent calls took only {elapsed:.2f}s, "
+            f"expected >=1.7s (0.5s * 4 inter-call gaps)"
+        )
+    finally:
+        await client.close()