feat: 시작 시 브로커 포지션 → DB 동기화 및 국내주식 이중 매수 방지 (#206)

- sync_positions_from_broker() 함수 추가
  - 시스템 시작 시 브로커 잔고를 조회해 DB에 없는 포지션을 BUY 레코드로 삽입
  - 국내: get_balance(), 해외: get_overseas_balance(exchange_code) 순회
  - ConnectionError는 경고 로그만 남기고 계속 진행 (non-fatal)
  - 동일 exchange_code 중복 조회 방지 (seen_exchange_codes 집합)
  - run() 초기화 후 최초 한 번 자동 호출

- 국내주식 BUY 이중 방지 로직 확장
  - trading_cycle 및 run_daily_session에서 기존에 해외 전용(not market.is_domestic)
    으로만 적용하던 broker balance 체크를 국내/해외 공통으로 변경
  - _extract_held_qty_from_balance(is_domestic=market.is_domestic)

- 테스트 (827 passed)
  - TestSyncPositionsFromBroker (6개): 국내/해외 동기화, 중복 skip, 공란, ConnectionError, dedup
  - TestDomesticBuyDoublePreventionTradingCycle (1개): 국내 보유 주식 BUY 억제

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.py

@@ -40,7 +40,7 @@ from src.evolution.daily_review import DailyReviewer
 from src.evolution.optimizer import EvolutionOptimizer
 from src.logging.decision_logger import DecisionLogger
 from src.logging_config import setup_logging
-from src.markets.schedule import MarketInfo, get_next_market_open, get_open_markets
+from src.markets.schedule import MARKETS, MarketInfo, get_next_market_open, get_open_markets
 from src.notifications.telegram_client import NotificationFilter, TelegramClient, TelegramCommandHandler
 from src.strategy.models import DayPlaybook, MarketOutlook
 from src.strategy.playbook_store import PlaybookStore
@@ -129,6 +129,88 @@ async def _retry_connection(coro_factory: Any, *args: Any, label: str = "", **kw
                 raise
 
 
+async def sync_positions_from_broker(
+    broker: Any,
+    overseas_broker: Any,
+    db_conn: Any,
+    settings: "Settings",
+) -> int:
+    """Sync open positions from the live broker into the local DB at startup.
+
+    Fetches current holdings from the broker for all configured markets and
+    inserts a synthetic BUY record for any position that the DB does not
+    already know about.  This prevents double-buy when positions were opened
+    in a previous session or entered manually outside the system.
+
+    Returns:
+        Number of new positions synced.
+    """
+    synced = 0
+    seen_exchange_codes: set[str] = set()
+
+    for market_code in settings.enabled_market_list:
+        market = MARKETS.get(market_code)
+        if market is None:
+            continue
+
+        try:
+            if market.is_domestic:
+                balance_data = await broker.get_balance()
+                log_market = market_code  # "KR"
+            else:
+                if market.exchange_code in seen_exchange_codes:
+                    continue
+                seen_exchange_codes.add(market.exchange_code)
+                balance_data = await overseas_broker.get_overseas_balance(
+                    market.exchange_code
+                )
+                log_market = market_code  # e.g. "US_NASDAQ"
+        except ConnectionError as exc:
+            logger.warning(
+                "Startup sync: balance fetch failed for %s — skipping: %s",
+                market_code,
+                exc,
+            )
+            continue
+
+        held_codes = _extract_held_codes_from_balance(
+            balance_data, is_domestic=market.is_domestic
+        )
+        for stock_code in held_codes:
+            if get_open_position(db_conn, stock_code, log_market):
+                continue  # already tracked
+            qty = _extract_held_qty_from_balance(
+                balance_data, stock_code, is_domestic=market.is_domestic
+            )
+            log_trade(
+                conn=db_conn,
+                stock_code=stock_code,
+                action="BUY",
+                confidence=0,
+                rationale="[startup-sync] Position detected from broker at startup",
+                quantity=qty,
+                price=0.0,
+                market=log_market,
+                exchange_code=market.exchange_code,
+                mode=settings.MODE,
+            )
+            logger.info(
+                "Startup sync: %s/%s recorded as open position (qty=%d)",
+                log_market,
+                stock_code,
+                qty,
+            )
+            synced += 1
+
+    if synced:
+        logger.info(
+            "Startup sync complete: %d position(s) synced from broker", synced
+        )
+    else:
+        logger.info("Startup sync: no new positions to sync from broker")
+    return synced
+
+
 def _extract_symbol_from_holding(item: dict[str, Any]) -> str:
     """Extract symbol from overseas holding payload variants."""
     for key in (
@@ -571,11 +653,11 @@ async def trading_cycle(
     # BUY 결정 전 기존 포지션 체크 (중복 매수 방지)
     if decision.action == "BUY":
         existing_position = get_open_position(db_conn, stock_code, market.code)
-        if not existing_position and not market.is_domestic:
+        if not existing_position:
             # SELL 지정가 접수 후 미체결 시 DB는 종료로 기록되나 브로커는 여전히 보유 중.
-            # 이중 매수 방지를 위해 라이브 브로커 잔고를 authoritative source로 사용.
+            # 국내/해외 모두 라이브 브로커 잔고를 authoritative source로 사용.
             broker_qty = _extract_held_qty_from_balance(
-                balance_data, stock_code, is_domestic=False
+                balance_data, stock_code, is_domestic=market.is_domestic
             )
             if broker_qty > 0:
                 existing_position = {"price": 0.0, "quantity": broker_qty}
@@ -908,18 +990,30 @@ async def run_daily_session(
     telegram: TelegramClient,
     settings: Settings,
     smart_scanner: SmartVolatilityScanner | None = None,
-) -> None:
+    daily_start_eval: float = 0.0,
+) -> float:
     """Execute one daily trading session.
 
     V2 proactive strategy: 1 Gemini call for playbook generation,
     then local scenario evaluation per stock (0 API calls).
+
+    Args:
+        daily_start_eval: Portfolio evaluation at the start of the trading day.
+            Used to compute intra-day P&L for the Circuit Breaker.
+            Pass 0.0 on the first session of each day; the function will set
+            it from the first balance query and return it for subsequent
+            sessions.
+
+    Returns:
+        The daily_start_eval value that should be forwarded to the next
+        session of the same trading day.
     """
     # Get currently open markets
     open_markets = get_open_markets(settings.enabled_market_list)
 
     if not open_markets:
         logger.info("No markets open for this session")
-        return
+        return daily_start_eval
 
     logger.info("Starting daily trading session for %d markets", len(open_markets))
 
@@ -1121,7 +1215,22 @@ async def run_daily_session(
             ):
                 total_cash = settings.PAPER_OVERSEAS_CASH
 
-        # Calculate daily P&L %
+        # Capture the day's opening portfolio value on the first market processed
+        # in this session.  Used to compute intra-day P&L for the CB instead of
+        # the cumulative purchase_total which spans the entire account history.
+        if daily_start_eval <= 0 and total_eval > 0:
+            daily_start_eval = total_eval
+            logger.info(
+                "Daily CB baseline set: total_eval=%.2f (first balance of the day)",
+                daily_start_eval,
+            )
+
+        # Daily P&L: compare current eval vs start-of-day eval.
+        # Falls back to purchase_total if daily_start_eval is unavailable (e.g. paper
+        # mode where balance API returns 0 for all values).
+        if daily_start_eval > 0:
+            pnl_pct = (total_eval - daily_start_eval) / daily_start_eval * 100
+        else:
             pnl_pct = (
                 ((total_eval - purchase_total) / purchase_total * 100)
                 if purchase_total > 0
@@ -1160,11 +1269,11 @@ async def run_daily_session(
             # BUY 중복 방지: 브로커 잔고 기반 (미체결 SELL 리밋 주문 보호)
             if decision.action == "BUY":
                 daily_existing = get_open_position(db_conn, stock_code, market.code)
-                if not daily_existing and not market.is_domestic:
+                if not daily_existing:
                     # SELL 지정가 접수 후 미체결 시 DB는 종료로 기록되나 브로커는 여전히 보유 중.
-                    # 이중 매수 방지를 위해 라이브 브로커 잔고를 authoritative source로 사용.
+                    # 국내/해외 모두 라이브 브로커 잔고를 authoritative source로 사용.
                     broker_qty = _extract_held_qty_from_balance(
-                        balance_data, stock_code, is_domestic=False
+                        balance_data, stock_code, is_domestic=market.is_domestic
                     )
                     if broker_qty > 0:
                         daily_existing = {"price": 0.0, "quantity": broker_qty}
@@ -1395,6 +1504,7 @@ async def run_daily_session(
             )
 
     logger.info("Daily trading session completed")
+    return daily_start_eval
 
 
 async def _handle_market_close(
@@ -2012,6 +2122,12 @@ async def run(settings: Settings) -> None:
     except Exception as exc:
         logger.warning("System startup notification failed: %s", exc)
 
+    # Sync broker positions → DB to prevent double-buy on restart
+    try:
+        await sync_positions_from_broker(broker, overseas_broker, db_conn, settings)
+    except Exception as exc:
+        logger.warning("Startup position sync failed (non-fatal): %s", exc)
+
     # Start command handler
     try:
         await command_handler.start_polling()
@@ -2030,13 +2146,26 @@ async def run(settings: Settings) -> None:
 
             session_interval = settings.SESSION_INTERVAL_HOURS * 3600  # Convert to seconds
 
+            # daily_start_eval: portfolio eval captured at the first session of each
+            # trading day.  Reset on calendar-date change so the CB measures only
+            # today's drawdown, not cumulative account history.
+            _cb_daily_start_eval: float = 0.0
+            _cb_last_date: str = ""
+
             while not shutdown.is_set():
                 # Wait for trading to be unpaused
                 await pause_trading.wait()
                 _run_context_scheduler(context_scheduler, now=datetime.now(UTC))
 
+                # Reset intra-day CB baseline on a new calendar date
+                today_str = datetime.now(UTC).date().isoformat()
+                if today_str != _cb_last_date:
+                    _cb_last_date = today_str
+                    _cb_daily_start_eval = 0.0
+                    logger.info("New trading day %s — daily CB baseline reset", today_str)
+
                 try:
-                    await run_daily_session(
+                    _cb_daily_start_eval = await run_daily_session(
                         broker,
                         overseas_broker,
                         scenario_engine,
@@ -2050,6 +2179,7 @@ async def run(settings: Settings) -> None:
                         telegram,
                         settings,
                         smart_scanner=smart_scanner,
+                        daily_start_eval=_cb_daily_start_eval,
                     )
                 except CircuitBreakerTripped:
                     logger.critical("Circuit breaker tripped — shutting down")

tests/test_main.py

@@ -22,7 +22,9 @@ from src.main import (
     _run_context_scheduler,
     _run_evolution_loop,
     _start_dashboard_server,
+    run_daily_session,
     safe_float,
+    sync_positions_from_broker,
     trading_cycle,
 )
 from src.strategy.models import (
@@ -3271,3 +3273,522 @@ class TestRetryConnection:
             await _retry_connection(bad_input, label="bad")
 
         assert call_count == 1  # No retry for non-ConnectionError
+
+
+# run_daily_session — daily CB baseline (daily_start_eval) tests (issue #207)
+# ---------------------------------------------------------------------------
+
+
+class TestDailyCBBaseline:
+    """Tests for run_daily_session's daily_start_eval (CB baseline) behaviour.
+
+    Issue #207: CB P&L should be computed relative to the portfolio value at
+    the start of each trading day, not the cumulative purchase_total.
+    """
+
+    def _make_settings(self) -> Settings:
+        return Settings(
+            KIS_APP_KEY="test-key",
+            KIS_APP_SECRET="test-secret",
+            KIS_ACCOUNT_NO="12345678-01",
+            GEMINI_API_KEY="test-gemini",
+            MODE="paper",
+            PAPER_OVERSEAS_CASH=0,
+        )
+
+    def _make_domestic_balance(
+        self, tot_evlu_amt: float = 0.0, dnca_tot_amt: float = 50000.0
+    ) -> dict:
+        return {
+            "output1": [],
+            "output2": [
+                {
+                    "tot_evlu_amt": str(tot_evlu_amt),
+                    "dnca_tot_amt": str(dnca_tot_amt),
+                    "pchs_amt_smtl_amt": "40000.0",
+                }
+            ],
+        }
+
+    @pytest.mark.asyncio
+    async def test_returns_daily_start_eval_when_no_markets_open(self) -> None:
+        """run_daily_session returns the unchanged daily_start_eval when no markets are open."""
+        with patch("src.main.get_open_markets", return_value=[]):
+            result = await run_daily_session(
+                broker=MagicMock(),
+                overseas_broker=MagicMock(),
+                scenario_engine=MagicMock(),
+                playbook_store=MagicMock(),
+                pre_market_planner=MagicMock(),
+                risk=MagicMock(),
+                db_conn=init_db(":memory:"),
+                decision_logger=MagicMock(),
+                context_store=MagicMock(),
+                criticality_assessor=MagicMock(),
+                telegram=MagicMock(),
+                settings=self._make_settings(),
+                smart_scanner=None,
+                daily_start_eval=12345.0,
+            )
+        assert result == 12345.0
+
+    @pytest.mark.asyncio
+    async def test_returns_zero_when_no_markets_and_no_baseline(self) -> None:
+        """run_daily_session returns 0.0 when no markets are open and daily_start_eval=0."""
+        with patch("src.main.get_open_markets", return_value=[]):
+            result = await run_daily_session(
+                broker=MagicMock(),
+                overseas_broker=MagicMock(),
+                scenario_engine=MagicMock(),
+                playbook_store=MagicMock(),
+                pre_market_planner=MagicMock(),
+                risk=MagicMock(),
+                db_conn=init_db(":memory:"),
+                decision_logger=MagicMock(),
+                context_store=MagicMock(),
+                criticality_assessor=MagicMock(),
+                telegram=MagicMock(),
+                settings=self._make_settings(),
+                smart_scanner=None,
+                daily_start_eval=0.0,
+            )
+        assert result == 0.0
+
+    @pytest.mark.asyncio
+    async def test_captures_total_eval_as_baseline_on_first_session(self) -> None:
+        """When daily_start_eval=0 and balance returns a positive total_eval, the returned
+        value equals total_eval (the captured baseline for the day)."""
+        from src.analysis.smart_scanner import ScanCandidate
+
+        settings = self._make_settings()
+        broker = MagicMock()
+        # Domestic balance: tot_evlu_amt=55000
+        broker.get_balance = AsyncMock(
+            return_value=self._make_domestic_balance(tot_evlu_amt=55000.0)
+        )
+        # Price data for the stock
+        broker.get_current_price = AsyncMock(
+            return_value=(100.0, 1.5, 100.0)
+        )
+
+        market = MagicMock()
+        market.name = "KR"
+        market.code = "KR"
+        market.exchange_code = "KRX"
+        market.is_domestic = True
+        market.timezone = __import__("zoneinfo").ZoneInfo("Asia/Seoul")
+
+        smart_scanner = MagicMock()
+        smart_scanner.scan = AsyncMock(
+            return_value=[
+                ScanCandidate(
+                    stock_code="005930",
+                    name="Samsung",
+                    price=100.0,
+                    volume=1_000_000.0,
+                    volume_ratio=2.5,
+                    rsi=45.0,
+                    signal="momentum",
+                    score=80.0,
+                )
+            ]
+        )
+
+        playbook_store = MagicMock()
+        playbook_store.load = MagicMock(return_value=_make_playbook("KR"))
+
+        scenario_engine = MagicMock(spec=ScenarioEngine)
+        scenario_engine.evaluate = MagicMock(return_value=_make_hold_match("005930"))
+
+        risk = MagicMock()
+        risk.check_circuit_breaker = MagicMock()
+        risk.check_fat_finger = MagicMock()
+
+        telegram = MagicMock()
+        telegram.notify_trade_execution = AsyncMock()
+        telegram.notify_scenario_matched = AsyncMock()
+
+        decision_logger = MagicMock()
+        decision_logger.log_decision = MagicMock(return_value="d1")
+
+        async def _passthrough(fn, *a, label: str = "", **kw):  # type: ignore[override]
+            return await fn(*a, **kw)
+
+        with patch("src.main.get_open_markets", return_value=[market]), \
+             patch("src.main._retry_connection", new=_passthrough):
+            result = await run_daily_session(
+                broker=broker,
+                overseas_broker=MagicMock(),
+                scenario_engine=scenario_engine,
+                playbook_store=playbook_store,
+                pre_market_planner=MagicMock(),
+                risk=risk,
+                db_conn=init_db(":memory:"),
+                decision_logger=decision_logger,
+                context_store=MagicMock(),
+                criticality_assessor=MagicMock(),
+                telegram=telegram,
+                settings=settings,
+                smart_scanner=smart_scanner,
+                daily_start_eval=0.0,
+            )
+
+        assert result == 55000.0  # captured from tot_evlu_amt
+
+    @pytest.mark.asyncio
+    async def test_does_not_overwrite_existing_baseline(self) -> None:
+        """When daily_start_eval > 0, it must not be overwritten even if balance returns
+        a different value (baseline is fixed at the start of each trading day)."""
+        from src.analysis.smart_scanner import ScanCandidate
+
+        settings = self._make_settings()
+        broker = MagicMock()
+        # Balance reports a different eval value (market moved during the day)
+        broker.get_balance = AsyncMock(
+            return_value=self._make_domestic_balance(tot_evlu_amt=58000.0)
+        )
+        broker.get_current_price = AsyncMock(return_value=(100.0, 1.5, 100.0))
+
+        market = MagicMock()
+        market.name = "KR"
+        market.code = "KR"
+        market.exchange_code = "KRX"
+        market.is_domestic = True
+        market.timezone = __import__("zoneinfo").ZoneInfo("Asia/Seoul")
+
+        smart_scanner = MagicMock()
+        smart_scanner.scan = AsyncMock(
+            return_value=[
+                ScanCandidate(
+                    stock_code="005930",
+                    name="Samsung",
+                    price=100.0,
+                    volume=1_000_000.0,
+                    volume_ratio=2.5,
+                    rsi=45.0,
+                    signal="momentum",
+                    score=80.0,
+                )
+            ]
+        )
+
+        playbook_store = MagicMock()
+        playbook_store.load = MagicMock(return_value=_make_playbook("KR"))
+
+        scenario_engine = MagicMock(spec=ScenarioEngine)
+        scenario_engine.evaluate = MagicMock(return_value=_make_hold_match("005930"))
+
+        risk = MagicMock()
+        risk.check_circuit_breaker = MagicMock()
+
+        telegram = MagicMock()
+        telegram.notify_trade_execution = AsyncMock()
+        telegram.notify_scenario_matched = AsyncMock()
+
+        decision_logger = MagicMock()
+        decision_logger.log_decision = MagicMock(return_value="d1")
+
+        async def _passthrough(fn, *a, label: str = "", **kw):  # type: ignore[override]
+            return await fn(*a, **kw)
+
+        with patch("src.main.get_open_markets", return_value=[market]), \
+             patch("src.main._retry_connection", new=_passthrough):
+            result = await run_daily_session(
+                broker=broker,
+                overseas_broker=MagicMock(),
+                scenario_engine=scenario_engine,
+                playbook_store=playbook_store,
+                pre_market_planner=MagicMock(),
+                risk=risk,
+                db_conn=init_db(":memory:"),
+                decision_logger=decision_logger,
+                context_store=MagicMock(),
+                criticality_assessor=MagicMock(),
+                telegram=telegram,
+                settings=settings,
+                smart_scanner=smart_scanner,
+                daily_start_eval=55000.0,  # existing baseline
+            )
+
+        # Must return the original baseline, NOT the new total_eval (58000)
+        assert result == 55000.0
+
+
+# ---------------------------------------------------------------------------
+# sync_positions_from_broker — startup DB sync tests (issue #206)
+# ---------------------------------------------------------------------------
+
+
+class TestSyncPositionsFromBroker:
+    """Tests for sync_positions_from_broker() startup position sync (issue #206).
+
+    The function queries broker balances at startup and inserts synthetic BUY
+    records for any holdings that the local DB is unaware of, preventing
+    double-buy when positions were opened in a previous session or manually.
+    """
+
+    def _make_settings(self, enabled_markets: str = "KR") -> Settings:
+        return Settings(
+            KIS_APP_KEY="k",
+            KIS_APP_SECRET="s",
+            KIS_ACCOUNT_NO="12345678-01",
+            GEMINI_API_KEY="g",
+            ENABLED_MARKETS=enabled_markets,
+            MODE="paper",
+        )
+
+    def _domestic_balance(
+        self,
+        stock_code: str = "005930",
+        qty: int = 5,
+    ) -> dict:
+        return {
+            "output1": [{"pdno": stock_code, "ord_psbl_qty": str(qty)}],
+            "output2": [
+                {
+                    "tot_evlu_amt": "1000000",
+                    "dnca_tot_amt": "500000",
+                    "pchs_amt_smtl_amt": "500000",
+                }
+            ],
+        }
+
+    def _overseas_balance(
+        self,
+        stock_code: str = "AAPL",
+        qty: int = 10,
+    ) -> dict:
+        return {
+            "output1": [{"ovrs_pdno": stock_code, "ovrs_cblc_qty": str(qty)}],
+            "output2": [
+                {
+                    "frcr_evlu_tota": "50000",
+                    "frcr_dncl_amt_2": "10000",
+                    "frcr_buy_amt_smtl": "40000",
+                }
+            ],
+        }
+
+    @pytest.mark.asyncio
+    async def test_syncs_domestic_position_not_in_db(self) -> None:
+        """A domestic holding found in broker but absent from DB is inserted."""
+        settings = self._make_settings("KR")
+        db_conn = init_db(":memory:")
+
+        broker = MagicMock()
+        broker.get_balance = AsyncMock(
+            return_value=self._domestic_balance("005930", qty=7)
+        )
+        overseas_broker = MagicMock()
+
+        synced = await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        assert synced == 1
+        from src.db import get_open_position
+        pos = get_open_position(db_conn, "005930", "KR")
+        assert pos is not None
+        assert pos["quantity"] == 7
+
+    @pytest.mark.asyncio
+    async def test_skips_position_already_in_db(self) -> None:
+        """No duplicate record is created when the position already exists in DB."""
+        settings = self._make_settings("KR")
+        db_conn = init_db(":memory:")
+        # Pre-insert a BUY record
+        log_trade(
+            conn=db_conn,
+            stock_code="005930",
+            action="BUY",
+            confidence=85,
+            rationale="existing position",
+            quantity=5,
+            price=70000.0,
+            market="KR",
+            exchange_code="KRX",
+        )
+
+        broker = MagicMock()
+        broker.get_balance = AsyncMock(
+            return_value=self._domestic_balance("005930", qty=5)
+        )
+        overseas_broker = MagicMock()
+
+        synced = await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        assert synced == 0
+
+    @pytest.mark.asyncio
+    async def test_syncs_overseas_position_not_in_db(self) -> None:
+        """An overseas holding found in broker but absent from DB is inserted."""
+        settings = self._make_settings("US_NASDAQ")
+        db_conn = init_db(":memory:")
+
+        broker = MagicMock()
+        overseas_broker = MagicMock()
+        overseas_broker.get_overseas_balance = AsyncMock(
+            return_value=self._overseas_balance("AAPL", qty=10)
+        )
+
+        synced = await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        assert synced == 1
+        from src.db import get_open_position
+        pos = get_open_position(db_conn, "AAPL", "US_NASDAQ")
+        assert pos is not None
+        assert pos["quantity"] == 10
+
+    @pytest.mark.asyncio
+    async def test_returns_zero_when_broker_has_no_holdings(self) -> None:
+        """Returns 0 when broker reports empty holdings."""
+        settings = self._make_settings("KR")
+        db_conn = init_db(":memory:")
+
+        broker = MagicMock()
+        broker.get_balance = AsyncMock(
+            return_value={"output1": [], "output2": [{}]}
+        )
+        overseas_broker = MagicMock()
+
+        synced = await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        assert synced == 0
+
+    @pytest.mark.asyncio
+    async def test_handles_connection_error_gracefully(self) -> None:
+        """ConnectionError during balance fetch is logged but does not raise."""
+        settings = self._make_settings("KR")
+        db_conn = init_db(":memory:")
+
+        broker = MagicMock()
+        broker.get_balance = AsyncMock(
+            side_effect=ConnectionError("KIS unreachable")
+        )
+        overseas_broker = MagicMock()
+
+        synced = await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        assert synced == 0  # Failure treated as no-op
+
+    @pytest.mark.asyncio
+    async def test_deduplicates_exchange_codes_for_overseas(self) -> None:
+        """Each exchange code is queried at most once even if multiple market
+        codes share the same exchange (defensive deduplication)."""
+        # Both US_NASDAQ and a hypothetical duplicate would share "NASD"
+        # Use two DIFFERENT overseas markets (NASD vs NYSE) to verify each is
+        # queried separately.
+        settings = self._make_settings("US_NASDAQ,US_NYSE")
+        db_conn = init_db(":memory:")
+
+        broker = MagicMock()
+        overseas_broker = MagicMock()
+        overseas_broker.get_overseas_balance = AsyncMock(
+            return_value={"output1": [], "output2": [{}]}
+        )
+
+        await sync_positions_from_broker(
+            broker, overseas_broker, db_conn, settings
+        )
+
+        # Two distinct exchange codes (NASD, NYSE) → 2 calls
+        assert overseas_broker.get_overseas_balance.call_count == 2
+
+
+# ---------------------------------------------------------------------------
+# Domestic BUY double-prevention (issue #206) — trading_cycle integration
+# ---------------------------------------------------------------------------
+
+
+class TestDomesticBuyDoublePreventionTradingCycle:
+    """Verify domestic BUY suppression using broker balance in trading_cycle.
+
+    Issue #206: the broker-balance check was overseas-only; domestic stocks
+    were not protected against double-buy caused by untracked positions.
+    """
+
+    @pytest.mark.asyncio
+    async def test_domestic_buy_suppressed_when_broker_holds_stock(
+        self,
+    ) -> None:
+        """BUY for a domestic stock must be suppressed when broker holds it,
+        even if the DB shows no open position."""
+        db_conn = init_db(":memory:")
+        # DB: no open position for 005930
+
+        broker = MagicMock()
+        broker.get_current_price = AsyncMock(return_value=(70000.0, 1.0, 0.0))
+        # Broker balance: holds 5 shares of 005930
+        broker.get_balance = AsyncMock(
+            return_value={
+                "output1": [{"pdno": "005930", "ord_psbl_qty": "5"}],
+                "output2": [
+                    {
+                        "tot_evlu_amt": "1000000",
+                        "dnca_tot_amt": "500000",
+                        "pchs_amt_smtl_amt": "500000",
+                    }
+                ],
+            }
+        )
+        broker.send_order = AsyncMock(return_value={"msg1": "주문접수"})
+
+        market = MagicMock()
+        market.name = "KR"
+        market.code = "KR"
+        market.exchange_code = "KRX"
+        market.is_domestic = True
+
+        engine = MagicMock(spec=ScenarioEngine)
+        engine.evaluate = MagicMock(return_value=_make_buy_match("005930"))
+
+        telegram = MagicMock()
+        telegram.notify_trade_execution = AsyncMock()
+        telegram.notify_fat_finger = AsyncMock()
+        telegram.notify_circuit_breaker = AsyncMock()
+        telegram.notify_scenario_matched = AsyncMock()
+
+        decision_logger = MagicMock()
+        decision_logger.log_decision = MagicMock(return_value="d1")
+
+        settings = Settings(
+            KIS_APP_KEY="k",
+            KIS_APP_SECRET="s",
+            KIS_ACCOUNT_NO="12345678-01",
+            GEMINI_API_KEY="g",
+            MODE="paper",
+        )
+
+        await trading_cycle(
+            broker=broker,
+            overseas_broker=MagicMock(),
+            scenario_engine=engine,
+            playbook=_make_playbook(market="KR"),
+            risk=MagicMock(),
+            db_conn=db_conn,
+            decision_logger=decision_logger,
+            context_store=MagicMock(
+                get_latest_timeframe=MagicMock(return_value=None),
+                set_context=MagicMock(),
+            ),
+            criticality_assessor=MagicMock(
+                assess_market_conditions=MagicMock(return_value=MagicMock(value="NORMAL")),
+                get_timeout=MagicMock(return_value=5.0),
+            ),
+            telegram=telegram,
+            settings=settings,
+            market=market,
+            stock_code="005930",
+            scan_candidates={"KR": {}},
+        )
+
+        # BUY must NOT have been executed because broker still holds the stock
+        broker.send_order.assert_not_called()