diff --git a/docs/data-model.md b/docs/data-model.md
index c41c25f..fcc5b33 100644
--- a/docs/data-model.md
+++ b/docs/data-model.md
@@ -49,7 +49,7 @@
 - limit_price :: numeric? :: 현재 pending 주문 지정가(side 무관, dcy-012/REQ-002 — 과거 `entry_price`에서 rename). pending 진입(매수/매도 지정가) 시 set, pending 이탈(→holding/→closed) 시 None 으로 clear → 매수 지정가가 매도로 누수되지 않음(issue #10). None 이면 dispatch 시 시장가.
 - allocated_capital :: numeric? :: 배정 자본
 - order_id / broker_order_id :: str? :: 주문 식별자(자유 주석 / 브로커 핸들)
-- venue :: TEXT NOT NULL DEFAULT 'KRX' :: 현재 주문 거래소 구분(KRX/NXT/SOR). pending 주문·취소까지 보존하고 INACTIVE 진입 시 KRX 초기화.
+- venue :: TEXT NOT NULL DEFAULT 'KRX' :: 현재 주문 거래소 구분(AUTO/KRX/NXT/SOR). intent 단계의 AUTO는 KIS 제출 시 실제 KRX/NXT로 교체되며 주문번호와 원자 저장한다. pending 주문·취소까지 보존하고 HOLDING 진입 시 다음 자율주문의 AUTO, INACTIVE 진입 시 KRX로 초기화한다.
 - strategy_id / sell_strategy_id :: str? :: 진입/청산 전략 식별
 - portfolio_id :: str? :: 포트폴리오 식별
 - forced_close_at :: datetime? :: 강제 청산 마감선
@@ -128,6 +128,7 @@
 - fee :: float :: BrokerPort `calculate_fee(side, qty*price)`
 - tax :: float :: 기본 0(정밀 모델 후속)
 - executed_at :: datetime?
+- venue :: str :: Core가 실제 제출에 사용한 거래소. 외부 Portfolio Hub API에는 아직 전달하지 않는다.
 - correlation_id (derived) :: `{asset_id}:{order_id}:{execution_id}`
 
 ### State Rules
@@ -147,6 +148,7 @@
 - side :: TEXT CHECK ('buy','sell')
 - qty / price / fee / tax :: NUMERIC(18,4)
 - executed_at :: TIMESTAMPTZ?
+- venue :: TEXT NOT NULL DEFAULT 'KRX' :: 실제 제출 거래소. 기존 행은 KRX로 보존한다.
 - status :: TEXT CHECK ('pending','completed','conflict_blocked','delivery_failed') — `delivery_failed` 추가(dcy-015, 마이그레이션 007)
 - attempts :: INTEGER :: 재시도 누적
 - last_outcome :: TEXT? CHECK ('completed','duplicate_completed','retryable_failure','conflict_blocked','permanent_failure','dead_lettered')
diff --git a/docs/interface-contract.md b/docs/interface-contract.md
index b4499ab..a36f566 100644
--- a/docs/interface-contract.md
+++ b/docs/interface-contract.md
@@ -396,7 +396,7 @@ resume_kill_switch 요청·응답 (REQ-046):
 
 ### Persistence
 
-- PostgreSQL: `ledger_outbox(correlation_id PK, asset_id, order_id, execution_id, side, qty, price, fee, tax, executed_at, status, attempts, last_outcome, last_error, created_at, updated_at)` — `ON CONFLICT (correlation_id) DO NOTHING` 이 outbox dedup 게이트.
+- PostgreSQL: `ledger_outbox(correlation_id PK, asset_id, order_id, execution_id, side, qty, price, fee, tax, executed_at, venue, status, attempts, last_outcome, last_error, created_at, updated_at)` — `ON CONFLICT (correlation_id) DO NOTHING` 이 outbox dedup 게이트. `venue`는 Core 내부 실제 제출 거래소이며 Portfolio Hub wire에는 아직 보내지 않는다.
 
 ## `OrderRequest` DTO (BAT-004 / REQ-011, BAT-056 / REQ-117)
 
@@ -415,8 +415,9 @@ resume_kill_switch 요청·응답 (REQ-046):
 ### Additive Notes (REQ-117)
 
 - `venue` 필드는 BAT-056에서 additive 추가. 기존 orb/tsl 미지정 호출 → 기본값 `"KRX"` 자동 적용 → 하위 호환.
-- `OrderRequest`는 AMQP wire 위를 직접 흐르지 않는다. BAT-059부터 buy/sell intent의 선택적 `venue`(기본 KRX)를 슬롯에 보존해 이 DTO까지 전달한다. 허용값 외에는 `invalid_venue`로 admission 전 거부한다.
-- KIS 어댑터(REQ-118)는 `venue` → `EXCG_ID_DVSN_CD` 로 변환해 KIS HTTP 요청에 항상 명시 전송.
+- `OrderRequest`는 AMQP wire 위를 직접 흐르지 않는다. buy/sell intent의 선택적 `venue` 기본은 `AUTO`이고, 명시한 KRX/NXT/SOR는 그대로 슬롯에 보존한다. 허용값 외에는 `invalid_venue`로 admission 전 거부한다.
+- KIS 어댑터는 `AUTO`를 KST 세션 기준 실제 KRX/NXT로 확정한 뒤 `EXCG_ID_DVSN_CD`로 전송한다. 결정 불가능 구간은 KRX로 대체하지 않고 주문을 거부한다.
+- `OrderAck.venue`의 실제 제출 거래소는 `broker_order_id`와 함께 슬롯에 원자 저장되며 재시작·취소·Core 원장 outbox에서 재사용한다.
 
 ## `BrokerPort` Protocol 메서드 (BAT-056 / REQ-118)
 
@@ -446,6 +447,7 @@ get_current_price(symbol: str, market: str = "J") -> Optional[Decimal]
 ### KIS 어댑터 EXCG 명시화 (REQ-118)
 
 - `submit_order`: body에 `EXCG_ID_DVSN_CD: req.venue` 항상 명시 전송 (이전: 미전송·서버 기본값 의존 → 명시화로 견고성 향상). 실측(2026-07-06): NXT(EXCG=NXT) 주문 rt_cd=0 확인.
+- `AUTO` 세션: 08:00~08:49:59 NXT, 09:00:30~15:29:59 KRX, 15:30~20:00 NXT. 그 밖의 시간은 `auto_venue_session_closed`로 fail-closed 한다.
 - `cancel_order`: body에 `EXCG_ID_DVSN_CD: venue` 명시 전송. 실측(2026-07-06): NXT 취소 rt_cd=0 확인.
 - `poll_fill`: 구 TR(`TTTC8001R`/`VTTC8001R`) 유지. NXT 체결 포함 여부 미확인(OPEN ITEM — 운영 스모크 필요). 확인 후 미포함이면 `TTTC0081R`(EXCG=ALL) 전환 별도 batch 처리.
 
diff --git a/tests/adapters/broker/test_venue.py b/tests/adapters/broker/test_venue.py
index 8dfdd61..411cb26 100644
--- a/tests/adapters/broker/test_venue.py
+++ b/tests/adapters/broker/test_venue.py
@@ -26,13 +26,12 @@ from __future__ import annotations
 from datetime import datetime, timedelta, timezone
 from decimal import Decimal
 
-import httpx
 import pytest
 
 from trex_core.adapters.broker import kis as kis_mod
-from trex_core.adapters.broker.kis import KISBroker
+from trex_core.adapters.broker.kis import KISBroker, resolve_order_venue
 from trex_core.adapters.broker.paper import PaperBroker
-from trex_core.application.broker_port import BrokerPort, OrderRequest
+from trex_core.application.broker_port import OrderRequest
 
 _MOCK_URL = "https://openapivts.koreainvestment.com:29443"
 _LIVE_URL = "https://openapi.koreainvestment.com:9443"
@@ -42,8 +41,14 @@ _LIVE_URL = "https://openapi.koreainvestment.com:9443"
 # Helpers
 # ---------------------------------------------------------------------------
 
-def _mock_broker() -> KISBroker:
-    b = KISBroker("12345678-01", app_key="k", app_secret="s", base_url=_MOCK_URL)
+def _mock_broker(*, clock=None) -> KISBroker:
+    b = KISBroker(
+        "12345678-01",
+        app_key="k",
+        app_secret="s",
+        base_url=_MOCK_URL,
+        clock=clock,
+    )
     b._token = "tok"
     b._token_exp = datetime.now(tz=timezone.utc) + timedelta(hours=1)
     return b
@@ -85,6 +90,84 @@ def test_order_request_venue_nxt():
     assert req.venue == "NXT"
 
 
+@pytest.mark.parametrize(
+    ("at", "expected"),
+    [
+        (datetime(2026, 7, 29, 8, 0, tzinfo=timezone(timedelta(hours=9))), "NXT"),
+        (datetime(2026, 7, 29, 8, 49, 59, tzinfo=timezone(timedelta(hours=9))), "NXT"),
+        (datetime(2026, 7, 29, 9, 0, 30, tzinfo=timezone(timedelta(hours=9))), "KRX"),
+        (datetime(2026, 7, 29, 15, 29, 59, tzinfo=timezone(timedelta(hours=9))), "KRX"),
+        (datetime(2026, 7, 29, 15, 30, tzinfo=timezone(timedelta(hours=9))), "NXT"),
+        (datetime(2026, 7, 29, 20, 0, tzinfo=timezone(timedelta(hours=9))), "NXT"),
+    ],
+)
+def test_auto_venue_resolves_by_kst_session(at, expected):
+    assert resolve_order_venue("AUTO", at) == expected
+
+
+@pytest.mark.parametrize(
+    "at",
+    [
+        datetime(2026, 7, 29, 7, 59, 59, tzinfo=timezone(timedelta(hours=9))),
+        datetime(2026, 7, 29, 8, 50, tzinfo=timezone(timedelta(hours=9))),
+        datetime(2026, 7, 29, 9, 0, 29, tzinfo=timezone(timedelta(hours=9))),
+        datetime(2026, 7, 29, 20, 0, 1, tzinfo=timezone(timedelta(hours=9))),
+    ],
+)
+def test_auto_venue_fails_closed_outside_supported_sessions(at):
+    with pytest.raises(ValueError, match="auto_venue_session_closed"):
+        resolve_order_venue("AUTO", at)
+
+
+def test_submit_auto_uses_nxt_and_reports_actual_venue(monkeypatch):
+    captured = {}
+    at = datetime(2026, 7, 29, 8, 1, tzinfo=timezone(timedelta(hours=9)))
+
+    def fake_post(url, headers=None, json=None, timeout=None):
+        captured["body"] = json
+        return _FakeResp(
+            {"rt_cd": "0", "output": {"ODNO": "0002", "KRX_FWDG_ORD_ORGNO": "06010"}}
+        )
+
+    broker = _mock_broker(clock=lambda: at)
+    monkeypatch.setattr(kis_mod.httpx, "post", fake_post)
+    ack = broker.submit_order(
+        OrderRequest(
+            slot_id="s-auto",
+            side="buy",
+            symbol="005930",
+            qty=1,
+            venue="AUTO",
+        )
+    )
+
+    assert ack.accepted is True
+    assert ack.venue == "NXT"
+    assert captured["body"]["EXCG_ID_DVSN_CD"] == "NXT"
+
+
+def test_submit_auto_outside_session_rejects_without_http(monkeypatch):
+    at = datetime(2026, 7, 29, 8, 55, tzinfo=timezone(timedelta(hours=9)))
+    broker = _mock_broker(clock=lambda: at)
+
+    def unexpected_post(*args, **kwargs):
+        raise AssertionError("AUTO session rejection must happen before HTTP")
+
+    monkeypatch.setattr(kis_mod.httpx, "post", unexpected_post)
+    ack = broker.submit_order(
+        OrderRequest(
+            slot_id="s-auto-closed",
+            side="buy",
+            symbol="005930",
+            qty=1,
+            venue="AUTO",
+        )
+    )
+
+    assert ack.accepted is False
+    assert ack.reason == "auto_venue_session_closed"
+
+
 # ---------------------------------------------------------------------------
 # REQ-117 AC-4: 기존 위치 인수 순서 불변
 # ---------------------------------------------------------------------------
diff --git a/tests/adapters/persistence/test_postgresql_ledger_outbox.py b/tests/adapters/persistence/test_postgresql_ledger_outbox.py
index 4836d08..f2bff2e 100644
--- a/tests/adapters/persistence/test_postgresql_ledger_outbox.py
+++ b/tests/adapters/persistence/test_postgresql_ledger_outbox.py
@@ -20,7 +20,7 @@ def _trade(execution_id="paper:1:10") -> LedgerTrade:
     return LedgerTrade(
         asset_id="PF-1", order_id="ORD-1", execution_id=execution_id,
         side="buy", qty=10, price=1000.0, fee=1.5, tax=0.0,
-        executed_at=datetime(2026, 6, 4, tzinfo=timezone.utc),
+        executed_at=datetime(2026, 6, 4, tzinfo=timezone.utc), venue="NXT",
     )
 
 
@@ -32,6 +32,7 @@ def test_enqueue_persists_and_is_idempotent(pg_clean):
     pending = outbox.list_pending()
     assert len(pending) == 1
     assert pending[0].status is WorkItemStatus.PENDING
+    assert pending[0].trade.venue == "NXT"
 
 
 def test_writer_completes_persisted_item(pg_clean):
diff --git a/tests/application/test_execution_ledger.py b/tests/application/test_execution_ledger.py
index 6f4d904..476aff4 100644
--- a/tests/application/test_execution_ledger.py
+++ b/tests/application/test_execution_ledger.py
@@ -59,6 +59,7 @@ def test_buy_fill_enqueues_one_ledger_item_and_writer_records_it():
     assert (t.asset_id, t.side, t.qty, t.price) == ("PF-1", "buy", 10, 1000.0)
     assert t.execution_id.startswith("paper:PAPER-")
     assert t.fee > 0.0 and t.tax == 0.0
+    assert t.venue == "AUTO"
 
 
 def test_sell_fill_enqueues_sell_ledger_item():
diff --git a/tests/application/test_execution_policy.py b/tests/application/test_execution_policy.py
index 4c26f86..adcbe0b 100644
--- a/tests/application/test_execution_policy.py
+++ b/tests/application/test_execution_policy.py
@@ -43,8 +43,8 @@ class _RecordingBroker:
     def poll_fill(self, broker_order_id, *, side, symbol):
         return self.responder(side)
 
-    def cancel_order(self, broker_order_id, *, side, symbol, qty):
-        self.cancel_calls.append((broker_order_id, side, symbol, qty))
+    def cancel_order(self, broker_order_id, *, side, symbol, qty, venue="KRX"):
+        self.cancel_calls.append((broker_order_id, side, symbol, qty, venue))
         if self.cancel_raises:
             raise RuntimeError("broker error")
         return True
diff --git a/tests/application/test_venue_intent_flow.py b/tests/application/test_venue_intent_flow.py
index d70fed6..19a50d2 100644
--- a/tests/application/test_venue_intent_flow.py
+++ b/tests/application/test_venue_intent_flow.py
@@ -1,10 +1,12 @@
 """Venue propagation from the strategy wire contract to broker execution."""
 from __future__ import annotations
 
+from uuid import UUID
+
 from trex_core.adapters.persistence.in_memory_intent_store import InMemoryIntentStore
 from trex_core.application.broker_port import BalanceItem, FillStatus, OrderAck, OrderRequest
 from trex_core.application.execution import ExecutionService
-from trex_core.application.intents import IntentService
+from trex_core.application.intents import BuyIntent, IntentService
 from trex_core.application.messaging import RpcRequest
 from trex_core.application.messaging_handlers import make_intent_rpc_handler
 from trex_core.domain.slot import SlotService, SlotState
@@ -12,13 +14,18 @@ from trex_core.domain.slot.in_memory_repository import InMemorySlotRepository
 
 
 class RecordingBroker:
-    def __init__(self) -> None:
+    def __init__(self, *, actual_venue: str | None = None) -> None:
         self.orders: list[OrderRequest] = []
         self.cancel_venues: list[str] = []
+        self.actual_venue = actual_venue
 
     def submit_order(self, req: OrderRequest) -> OrderAck:
         self.orders.append(req)
-        return OrderAck(accepted=True, broker_order_id=f"order-{len(self.orders)}")
+        return OrderAck(
+            accepted=True,
+            broker_order_id=f"order-{len(self.orders)}",
+            venue=self.actual_venue or req.venue,
+        )
 
     def poll_fill(self, broker_order_id: str, *, side: str, symbol: str) -> FillStatus:
         return FillStatus(state="accepted")
@@ -104,6 +111,41 @@ def test_invalid_venue_is_rejected_before_slot_transition() -> None:
     assert repo.list_slots("default")[0].status is SlotState.INACTIVE
 
 
+def test_omitted_wire_venue_is_auto_then_actual_venue_is_persisted() -> None:
+    repo = InMemorySlotRepository()
+    service = SlotService(repo)
+    intents = IntentService(
+        service,
+        repo,
+        InMemoryIntentStore(),
+        resolve_symbol=lambda portfolio_id: "005930",
+    )
+    repo.reconcile_universe("default", {"PF-1": "005930"})
+    broker = RecordingBroker(actual_venue="NXT")
+    execution = ExecutionService(service, repo, broker)
+    handler = make_intent_rpc_handler(intents)
+
+    response = handler(
+        RpcRequest(
+            payload={
+                "intent_type": "buy",
+                "intent_id": "auto-buy",
+                "portfolio_id": "PF-1",
+                "qty": 1,
+            },
+            correlation_id="auto-buy",
+        )
+    )
+
+    slot_id = UUID(response.payload["slot_id"])
+    pending = repo.fetch_slot(slot_id)
+    assert pending is not None and pending.venue == "AUTO"
+    execution.run_once()
+    dispatched = repo.fetch_slot(slot_id)
+    assert broker.orders[0].venue == "AUTO"
+    assert dispatched is not None and dispatched.venue == "NXT"
+
+
 def test_inactive_transition_resets_venue_to_krx() -> None:
     repo, intents, _, _ = _wire()
     handler = make_intent_rpc_handler(intents)
@@ -131,6 +173,30 @@ def test_inactive_transition_resets_venue_to_krx() -> None:
     assert reset.venue == "KRX"
 
 
+def test_holding_transition_resets_next_order_venue_to_auto() -> None:
+    repo, intents, _, _ = _wire()
+    decision = intents.submit_buy(
+        BuyIntent(
+            intent_id="nxt-buy-holding",
+            portfolio_id="PF-1",
+            qty=1,
+            venue="NXT",
+        )
+    )
+    slot = repo.fetch_slot(decision.slot_id)
+    service = SlotService(repo)
+    holding = service.transit_slot(
+        slot.slot_id,
+        SlotState.PENDING_BUY,
+        SlotState.HOLDING,
+        reason="fill",
+        actor="test",
+        qty=1,
+        avg_price=1000,
+    )
+    assert holding.venue == "AUTO"
+
+
 def test_operator_cancel_uses_original_nxt_venue() -> None:
     repo, intents, execution, broker = _wire()
     handler = make_intent_rpc_handler(intents)
diff --git a/trex_core/adapters/broker/kis.py b/trex_core/adapters/broker/kis.py
index e251184..f78bce3 100644
--- a/trex_core/adapters/broker/kis.py
+++ b/trex_core/adapters/broker/kis.py
@@ -14,10 +14,10 @@ from __future__ import annotations
 import base64
 import json
 from dataclasses import replace
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, time, timedelta, timezone
 from decimal import Decimal, InvalidOperation
 from time import monotonic
-from typing import Optional
+from typing import Callable, Optional
 
 import httpx
 
@@ -37,6 +37,30 @@ _MOCK_HINTS = ("openapivts", "virtual", "mock")
 _FILL_POLL_MIN_INTERVAL_SECONDS = 5.0
 _FILL_POLL_TRANSPORT_BACKOFF_SECONDS = 30.0
 _SUBMISSION_LOOKUP_GRACE_SECONDS = 90.0
+_SUPPORTED_ORDER_VENUES = frozenset({"AUTO", "KRX", "NXT", "SOR"})
+
+
+def resolve_order_venue(venue: str, at: datetime) -> str:
+    """Resolve AUTO to the venue that accepts domestic-stock orders at `at`.
+
+    The gaps are intentional fail-closed intervals. They prevent an AUTO order
+    from silently falling back to KRX while the opening venue is indeterminate.
+    Explicit KRX/NXT/SOR values are preserved.
+    """
+    normalized = str(venue).strip().upper()
+    if normalized not in _SUPPORTED_ORDER_VENUES:
+        raise ValueError("unsupported_order_venue")
+    if normalized != "AUTO":
+        return normalized
+
+    current = at.astimezone(_KST).time().replace(tzinfo=None)
+    if time(8, 0) <= current < time(8, 50):
+        return "NXT"
+    if time(9, 0, 30) <= current < time(15, 30):
+        return "KRX"
+    if time(15, 30) <= current <= time(20, 0):
+        return "NXT"
+    raise ValueError("auto_venue_session_closed")
 
 
 def _safe_int(v: object) -> Optional[int]:
@@ -108,6 +132,7 @@ class KISBroker:
         timeout: float = 5.0,
         allow_live: bool = False,
         token_cache=None,
+        clock: Optional[Callable[[], datetime]] = None,
     ) -> None:
         self._account_ref = account_ref
         self._app_key = app_key
@@ -117,6 +142,7 @@ class KISBroker:
         self._token: Optional[str] = None
         self._token_exp: datetime = datetime.now(tz=timezone.utc)
         self._token_cache = token_cache  # optional TokenCache (L2, REQ-016)
+        self._clock = clock or (lambda: datetime.now(tz=_KST))
         self._fill_poll_not_before: dict[str, float] = {}
         is_mock = any(h in self._base_url for h in _MOCK_HINTS)
         if not is_mock and not allow_live:
@@ -226,23 +252,28 @@ class KISBroker:
     # --- BrokerPort ---
     def submit_order(self, req: OrderRequest) -> OrderAck:
         cano, product = self._account()
-        submitted_at = datetime.now(tz=_KST)
+        submitted_at = self._clock().astimezone(_KST)
+        try:
+            actual_venue = resolve_order_venue(req.venue, submitted_at)
+        except ValueError as exc:
+            return OrderAck(accepted=False, reason=str(exc))
+        resolved_req = replace(req, venue=actual_venue)
         body = {
             "CANO": cano,
             "ACNT_PRDT_CD": product,
-            "PDNO": req.symbol,
-            "ORD_DVSN": req.order_type,
-            "ORD_QTY": str(req.qty),
-            "ORD_UNPR": str(req.limit_price or 0),
+            "PDNO": resolved_req.symbol,
+            "ORD_DVSN": resolved_req.order_type,
+            "ORD_QTY": str(resolved_req.qty),
+            "ORD_UNPR": str(resolved_req.limit_price or 0),
             # REQ-118: always send EXCG_ID_DVSN_CD from req.venue (default "KRX").
             # Previously omitted (server defaulted to KRX); explicit is more robust.
             # Real-account NXT order confirmed rt_cd=0 on 2026-07-06.
-            "EXCG_ID_DVSN_CD": req.venue,
+            "EXCG_ID_DVSN_CD": actual_venue,
         }
         try:
             resp = httpx.post(
                 f"{self._base_url}/uapi/domestic-stock/v1/trading/order-cash",
-                headers=self._headers(self._tr_submit(req.side)),
+                headers=self._headers(self._tr_submit(resolved_req.side)),
                 json=body,
                 timeout=self._timeout,
             )
@@ -253,15 +284,17 @@ class KISBroker:
             # the execution loop cannot submit the same order again.
             return OrderAck(
                 accepted=True,
-                broker_order_id=_encode_submission_unknown(req, submitted_at),
+                broker_order_id=_encode_submission_unknown(resolved_req, submitted_at),
                 reason=f"submit_outcome_unknown:{type(exc).__name__}",
+                venue=actual_venue,
                 raw={"error_class": type(exc).__name__},
             )
         if getattr(resp, "status_code", 200) >= 500:
             return OrderAck(
                 accepted=True,
-                broker_order_id=_encode_submission_unknown(req, submitted_at),
+                broker_order_id=_encode_submission_unknown(resolved_req, submitted_at),
                 reason=f"submit_outcome_unknown:http_{resp.status_code}",
+                venue=actual_venue,
                 raw={"http_status": resp.status_code},
             )
         if str(payload.get("rt_cd")) == "0":
@@ -269,9 +302,17 @@ class KISBroker:
             odno = out.get("ODNO") or out.get("odno")
             orgno = out.get("KRX_FWDG_ORD_ORGNO") or out.get("ord_gno_brno") or ""
             bid = f"{orgno}:{odno}" if orgno else str(odno)
-            return OrderAck(accepted=True, broker_order_id=bid, raw=payload)
+            return OrderAck(
+                accepted=True,
+                broker_order_id=bid,
+                venue=actual_venue,
+                raw=payload,
+            )
         return OrderAck(
-            accepted=False, reason=payload.get("msg1") or payload.get("msg_cd"), raw=payload
+            accepted=False,
+            reason=payload.get("msg1") or payload.get("msg_cd"),
+            venue=actual_venue,
+            raw=payload,
         )
 
     def poll_fill(self, broker_order_id: str, *, side: str, symbol: str) -> FillStatus:
diff --git a/trex_core/adapters/broker/paper.py b/trex_core/adapters/broker/paper.py
index 5afb701..017409b 100644
--- a/trex_core/adapters/broker/paper.py
+++ b/trex_core/adapters/broker/paper.py
@@ -76,7 +76,7 @@ class PaperBroker:
                 seq = self._seq
             oid = f"PAPER-{seq:06d}"
             self._orders[oid] = _Order(oid, req)
-        return OrderAck(accepted=True, broker_order_id=oid)
+        return OrderAck(accepted=True, broker_order_id=oid, venue=req.venue)
 
     def poll_fill(self, broker_order_id: str, *, side: str, symbol: str) -> FillStatus:
         with self._lock:
diff --git a/trex_core/adapters/persistence/postgresql.py b/trex_core/adapters/persistence/postgresql.py
index 1016bc2..36da514 100644
--- a/trex_core/adapters/persistence/postgresql.py
+++ b/trex_core/adapters/persistence/postgresql.py
@@ -285,13 +285,25 @@ class PostgreSQLSlotRepository:
                 )
                 return [self._row_to_slot(r) for r in cur.fetchall()]
 
-    def mark_dispatched(self, slot_id: UUID, broker_order_id: str) -> bool:
+    def mark_dispatched(
+        self,
+        slot_id: UUID,
+        broker_order_id: str,
+        *,
+        venue: Optional[str] = None,
+    ) -> bool:
         with self._psycopg.connect(self._dsn, autocommit=False) as conn:
             with conn.cursor() as cur:
                 cur.execute(
-                    "UPDATE daily_slot SET broker_order_id=%s, updated_at=%s "
+                    "UPDATE daily_slot SET broker_order_id=%s, "
+                    "venue=COALESCE(%s, venue), updated_at=%s "
                     "WHERE slot_id=%s AND broker_order_id IS NULL",
-                    (broker_order_id, datetime.now(tz=timezone.utc), slot_id),
+                    (
+                        broker_order_id,
+                        venue,
+                        datetime.now(tz=timezone.utc),
+                        slot_id,
+                    ),
                 )
                 ok = cur.rowcount == 1
                 conn.commit()
@@ -456,7 +468,7 @@ class _PgIntentRecord:
 _OUTBOX_COLUMNS = (
     "correlation_id, asset_id, order_id, execution_id, side, qty, price, "
     "fee, tax, executed_at, status, attempts, last_outcome, last_error, "
-    "created_at, updated_at, next_retry_at"
+    "created_at, updated_at, next_retry_at, venue"
 )
 
 
@@ -473,8 +485,8 @@ class PostgreSQLLedgerOutbox:
                 cur.execute(
                     "INSERT INTO ledger_outbox "
                     "(correlation_id, asset_id, order_id, execution_id, side, "
-                    " qty, price, fee, tax, executed_at) "
-                    "VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s) "
+                    " qty, price, fee, tax, executed_at, venue) "
+                    "VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s) "
                     "ON CONFLICT (correlation_id) DO NOTHING",
                     (
                         trade.correlation_id,
@@ -487,6 +499,7 @@ class PostgreSQLLedgerOutbox:
                         trade.fee,
                         trade.tax,
                         trade.executed_at,
+                        trade.venue,
                     ),
                 )
                 conn.commit()
@@ -590,6 +603,7 @@ class PostgreSQLLedgerOutbox:
             fee=f(row[7]),
             tax=f(row[8]),
             executed_at=row[9],
+            venue=row[17],
         )
         return LedgerWorkItem(
             correlation_id=row[0],
diff --git a/trex_core/adapters/persistence/sql/019_preserve_actual_order_venue.sql b/trex_core/adapters/persistence/sql/019_preserve_actual_order_venue.sql
new file mode 100644
index 0000000..54b4610
--- /dev/null
+++ b/trex_core/adapters/persistence/sql/019_preserve_actual_order_venue.sql
@@ -0,0 +1,20 @@
+-- dcy-041 / GitHub #44: AUTO may exist while an intent is pending, but the
+-- actual submitted KRX/NXT value replaces it atomically with broker_order_id.
+ALTER TABLE daily_slot
+    DROP CONSTRAINT IF EXISTS daily_slot_venue_check;
+
+ALTER TABLE daily_slot
+    ADD CONSTRAINT daily_slot_venue_check
+    CHECK (venue IN ('AUTO', 'KRX', 'NXT', 'SOR'));
+
+-- Core keeps the actual venue in its durable ledger outbox. Portfolio Hub's
+-- HTTP schema is intentionally unchanged in this migration.
+ALTER TABLE ledger_outbox
+    ADD COLUMN IF NOT EXISTS venue TEXT NOT NULL DEFAULT 'KRX';
+
+ALTER TABLE ledger_outbox
+    DROP CONSTRAINT IF EXISTS ledger_outbox_venue_check;
+
+ALTER TABLE ledger_outbox
+    ADD CONSTRAINT ledger_outbox_venue_check
+    CHECK (venue IN ('AUTO', 'KRX', 'NXT', 'SOR'));
diff --git a/trex_core/application/broker_port.py b/trex_core/application/broker_port.py
index 7da3c1f..e9bbc73 100644
--- a/trex_core/application/broker_port.py
+++ b/trex_core/application/broker_port.py
@@ -45,6 +45,10 @@ class OrderAck:
     accepted: bool
     broker_order_id: Optional[str] = None
     reason: Optional[str] = None
+    # Actual venue used for submission. KIS resolves AUTO before the HTTP call;
+    # execution persists this value with the broker order id so restart/cancel
+    # never has to infer the original venue.
+    venue: Optional[str] = None
     raw: dict[str, Any] = field(default_factory=dict)
 
 
diff --git a/trex_core/application/execution.py b/trex_core/application/execution.py
index 0987cee..2a8d874 100644
--- a/trex_core/application/execution.py
+++ b/trex_core/application/execution.py
@@ -201,7 +201,11 @@ class ExecutionService:
                 )
             )
             if ack.accepted and ack.broker_order_id:
-                self._repo.mark_dispatched(slot.slot_id, ack.broker_order_id)
+                self._repo.mark_dispatched(
+                    slot.slot_id,
+                    ack.broker_order_id,
+                    venue=ack.venue,
+                )
                 r.dispatched += 1
                 if ack.reason and ack.reason.startswith("submit_outcome_unknown:"):
                     _log.warning(
@@ -643,6 +647,7 @@ class ExecutionService:
             fee=float(fs.fee),
             tax=float(fs.tax),
             executed_at=datetime.now(tz=timezone.utc),
+            venue=slot.venue,
         )
         self._ledger_outbox.enqueue(trade)
         r.ledger_enqueued += 1
diff --git a/trex_core/application/intents.py b/trex_core/application/intents.py
index 50d9b99..57f6d9d 100644
--- a/trex_core/application/intents.py
+++ b/trex_core/application/intents.py
@@ -75,7 +75,9 @@ class BuyIntent:
     # slippage_pct: effective limit = entry_price*(1+pct/100) buy / *(1-pct/100) sell.
     timeout_sec: Optional[int] = None
     slippage_pct: Optional[float] = None
-    venue: str = "KRX"
+    # Strategy wire default. AUTO is resolved at the broker boundary so
+    # strategies remain session-agnostic while explicit KRX/NXT/SOR is kept.
+    venue: str = "AUTO"
     extra: dict[str, Any] = field(default_factory=dict)
 
 
@@ -94,7 +96,7 @@ class SellIntent:
     # dcy-022 / REQ-068: execution policy (optional, backward-compat).
     timeout_sec: Optional[int] = None
     slippage_pct: Optional[float] = None
-    venue: str = "KRX"
+    venue: str = "AUTO"
     extra: dict[str, Any] = field(default_factory=dict)
 
 
@@ -211,7 +213,7 @@ class IntentService:
         dcy-036 / REQ-114: entry gate — if entry_allowed_fn returns False,
         BuyIntent is rejected before any slot lookup."""
 
-        if intent.venue not in {"KRX", "NXT", "SOR"}:
+        if intent.venue not in {"AUTO", "KRX", "NXT", "SOR"}:
             return IntentDecision(intent.intent_id, "rejected", None, "invalid_venue")
 
         # dcy-036 / REQ-114: day-start entry gate (fail-closed).
@@ -308,7 +310,7 @@ class IntentService:
         return IntentDecision(intent.intent_id, "rejected", None, "already_active")
 
     def _admit_sell(self, intent: SellIntent) -> IntentDecision:
-        if intent.venue not in {"KRX", "NXT", "SOR"}:
+        if intent.venue not in {"AUTO", "KRX", "NXT", "SOR"}:
             return IntentDecision(intent.intent_id, "rejected", None, "invalid_venue")
 
         slot = self._repo.fetch_slot(intent.slot_id)
diff --git a/trex_core/application/ledger_port.py b/trex_core/application/ledger_port.py
index 56dcf8e..ee37273 100644
--- a/trex_core/application/ledger_port.py
+++ b/trex_core/application/ledger_port.py
@@ -57,6 +57,9 @@ class LedgerTrade:
     fee: float = 0.0
     tax: float = 0.0
     executed_at: Optional[datetime] = None
+    # Actual order venue persisted in the Core outbox. Portfolio Hub remains
+    # unchanged until its API contract explicitly accepts this additive field.
+    venue: str = "KRX"
 
     @property
     def correlation_id(self) -> str:
diff --git a/trex_core/application/messaging_handlers.py b/trex_core/application/messaging_handlers.py
index 2a4f3e6..d0d7a8a 100644
--- a/trex_core/application/messaging_handlers.py
+++ b/trex_core/application/messaging_handlers.py
@@ -117,7 +117,7 @@ def make_intent_rpc_handler(
                     # dcy-022 / REQ-068: execution policy (optional, backward-compat).
                     timeout_sec=_opt_int(body.get("timeout_sec")),
                     slippage_pct=_opt_float(body.get("slippage_pct")),
-                    venue=_opt_str(body.get("venue")) or "KRX",
+                    venue=_opt_str(body.get("venue")) or "AUTO",
                 )
                 d = intent_service.submit_buy(buy)
             elif intent_type == "sell":
@@ -133,7 +133,7 @@ def make_intent_rpc_handler(
                     # dcy-022 / REQ-068: execution policy (optional, backward-compat).
                     timeout_sec=_opt_int(body.get("timeout_sec")),
                     slippage_pct=_opt_float(body.get("slippage_pct")),
-                    venue=_opt_str(body.get("venue")) or "KRX",
+                    venue=_opt_str(body.get("venue")) or "AUTO",
                 )
                 d = intent_service.submit_sell(sell)
             else:
@@ -627,4 +627,3 @@ def _parse_date(v) -> date_cls:
 
 def _today() -> date_cls:
     return datetime.now(tz=timezone.utc).date()
-
diff --git a/trex_core/domain/slot/in_memory_repository.py b/trex_core/domain/slot/in_memory_repository.py
index 494d5fa..f4420f8 100644
--- a/trex_core/domain/slot/in_memory_repository.py
+++ b/trex_core/domain/slot/in_memory_repository.py
@@ -185,13 +185,22 @@ class InMemorySlotRepository:
         ]
         return out[:limit]
 
-    def mark_dispatched(self, slot_id: UUID, broker_order_id: str) -> bool:
-        """Atomically set broker_order_id iff still undispatched (idempotency guard)."""
+    def mark_dispatched(
+        self,
+        slot_id: UUID,
+        broker_order_id: str,
+        *,
+        venue: Optional[str] = None,
+    ) -> bool:
+        """Atomically persist dispatch identity and the actual broker venue."""
         s = self._slots.get(slot_id)
         if s is None or s.broker_order_id is not None:
             return False
         self._slots[slot_id] = replace(
-            s, broker_order_id=broker_order_id, updated_at=datetime.now(tz=timezone.utc)
+            s,
+            broker_order_id=broker_order_id,
+            venue=venue if venue is not None else s.venue,
+            updated_at=datetime.now(tz=timezone.utc),
         )
         return True
 
diff --git a/trex_core/domain/slot/service.py b/trex_core/domain/slot/service.py
index 80ca97d..6767d14 100644
--- a/trex_core/domain/slot/service.py
+++ b/trex_core/domain/slot/service.py
@@ -215,10 +215,15 @@ class SlotService:
             new_limit_price = limit_price if limit_price is not None else slot.limit_price
             new_timeout_sec = timeout_sec if timeout_sec is not None else slot.timeout_sec
             new_slippage_pct = slippage_pct if slippage_pct is not None else slot.slippage_pct
+            new_venue = venue if venue is not None else slot.venue
         else:  # HOLDING / ERROR — pending order policy no longer applies.
             new_limit_price = None
             new_timeout_sec = None
             new_slippage_pct = None
+            # A completed order's venue must not leak into a later autonomous
+            # sell. The next order starts session-aware unless its intent
+            # explicitly chooses KRX/NXT/SOR.
+            new_venue = "AUTO" if to_state is SlotState.HOLDING else slot.venue
 
         # occupancy_seq (dcy-028/REQ-081): bump when a slot begins a new
         # occupancy (inactive→pending_buy). Stable across the rest of the
@@ -271,7 +276,7 @@ class SlotService:
             timeout_sec=new_timeout_sec,
             slippage_pct=new_slippage_pct,
             occupancy_seq=new_occupancy_seq,
-            venue=venue if venue is not None else slot.venue,
+            venue=new_venue,
             updated_at=datetime.now(tz=timezone.utc),
         )