diff --git a/docs/data-model.md b/docs/data-model.md
index fcc5b33..0501e03 100644
--- a/docs/data-model.md
+++ b/docs/data-model.md
@@ -50,6 +50,8 @@
 - 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(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.
+- cancel_state :: TEXT? :: 취소 요청의 즉시 결과(requested/rejected/unknown). 최종 취소 상태가 아니며 같은 주문의 자동 재취소를 막는다.
+- cancel_requested_at :: TIMESTAMPTZ? :: 취소 요청 결과를 저장한 시각. 주문 종료·dispatch clear 때 함께 제거한다.
 - strategy_id / sell_strategy_id :: str? :: 진입/청산 전략 식별
 - portfolio_id :: str? :: 포트폴리오 식별
 - forced_close_at :: datetime? :: 강제 청산 마감선
diff --git a/docs/interface-contract.md b/docs/interface-contract.md
index a36f566..b441244 100644
--- a/docs/interface-contract.md
+++ b/docs/interface-contract.md
@@ -431,10 +431,12 @@ resume_kill_switch 요청·응답 (REQ-046):
 ### cancel_order
 
 ```
-cancel_order(broker_order_id: str, *, side: str, symbol: str, qty: int, venue: str = "KRX") -> bool
+cancel_order(broker_order_id: str, *, side: str, symbol: str, qty: int, venue: str = "KRX") -> CancelOutcome
 ```
 
 - `venue`: 원주문 venue. 취소 시 원주문과 동일한 `EXCG_ID_DVSN_CD`를 사용해야 한다. 기본값 `"KRX"`로 기존 호출자 하위 호환.
+- `CancelOutcome.state`: `requested`(요청 접수), `rejected`(명시적 거부), `unknown`(응답유실·전송 실패). `requested`도 최종 취소가 아니며 `poll_fill()`의 `cancelled|filled`만 주문의 최종 상태를 확정한다.
+- Core는 외부 취소 호출 전에 `unknown`을 먼저 영속화하고 응답 뒤 실제 즉시 결과로 교체한다. 따라서 요청과 저장 사이에 프로세스가 종료돼도 자동 timeout 취소는 같은 주문을 재전송하지 않고, 재시작 뒤 체결조회로만 수렴한다.
 
 ### get_current_price
 
diff --git a/tests/adapters/broker/test_kis.py b/tests/adapters/broker/test_kis.py
index 57d23f9..5c32f05 100644
--- a/tests/adapters/broker/test_kis.py
+++ b/tests/adapters/broker/test_kis.py
@@ -12,7 +12,11 @@ import httpx
 import pytest
 
 from trex_core.adapters.broker.kis import KISBroker
-from trex_core.application.broker_port import BrokerBalanceError, OrderRequest
+from trex_core.application.broker_port import (
+    BrokerBalanceError,
+    CancelState,
+    OrderRequest,
+)
 
 _MOCK_URL = "https://openapivts.koreainvestment.com:29443"
 
@@ -179,15 +183,13 @@ def test_submit_transport_failure_blocks_automatic_duplicate(monkeypatch):
     assert ack.accepted is True
     assert ack.broker_order_id.startswith("submission-unknown:")
     assert ack.reason == "submit_outcome_unknown:ReadTimeout"
-    assert (
-        b.cancel_order(
-            ack.broker_order_id,
-            side="buy",
-            symbol="005930",
-            qty=4,
-        )
-        is False
+    cancel = b.cancel_order(
+        ack.broker_order_id,
+        side="buy",
+        symbol="005930",
+        qty=4,
     )
+    assert cancel.state is CancelState.UNKNOWN
 
 
 def test_submit_gateway_5xx_blocks_automatic_duplicate(monkeypatch):
diff --git a/tests/adapters/broker/test_ownership.py b/tests/adapters/broker/test_ownership.py
index 7042bc7..2458b05 100644
--- a/tests/adapters/broker/test_ownership.py
+++ b/tests/adapters/broker/test_ownership.py
@@ -9,6 +9,8 @@ from trex_core.adapters.broker.ownership import (
 from trex_core.application.broker_port import (
     BalanceItem,
     BrokerBalanceError,
+    CancelOutcome,
+    CancelState,
     FillStatus,
     OrderAck,
 )
@@ -29,7 +31,7 @@ class FakeBroker:
         return self.fill
 
     def cancel_order(self, broker_order_id, *, side, symbol, qty, venue="KRX"):
-        return True
+        return CancelOutcome(CancelState.REQUESTED)
 
     def get_balance(self):
         return self.balance
diff --git a/tests/adapters/broker/test_venue.py b/tests/adapters/broker/test_venue.py
index 411cb26..c5d6701 100644
--- a/tests/adapters/broker/test_venue.py
+++ b/tests/adapters/broker/test_venue.py
@@ -26,12 +26,13 @@ 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, resolve_order_venue
 from trex_core.adapters.broker.paper import PaperBroker
-from trex_core.application.broker_port import OrderRequest
+from trex_core.application.broker_port import CancelState, OrderRequest
 
 _MOCK_URL = "https://openapivts.koreainvestment.com:29443"
 _LIVE_URL = "https://openapi.koreainvestment.com:9443"
@@ -218,7 +219,7 @@ def test_paper_cancel_venue_ignored():
     ack = b.submit_order(req)
     # NXT venue로 cancel — paper는 venue 무관하게 취소 성공
     result = b.cancel_order(ack.broker_order_id, side="buy", symbol="005930", qty=5, venue="NXT")
-    assert result is True
+    assert result.state is CancelState.REQUESTED
 
 
 def test_paper_cancel_default_venue():
@@ -227,7 +228,7 @@ def test_paper_cancel_default_venue():
     req = OrderRequest(slot_id="s1", side="buy", symbol="005930", qty=3)
     ack = b.submit_order(req)
     result = b.cancel_order(ack.broker_order_id, side="buy", symbol="005930", qty=3)
-    assert result is True
+    assert result.state is CancelState.REQUESTED
 
 
 # ---------------------------------------------------------------------------
@@ -301,6 +302,40 @@ def test_cancel_order_krx_includes_excg(monkeypatch):
     assert captured["body"]["EXCG_ID_DVSN_CD"] == "KRX"
 
 
+def test_cancel_explicit_broker_rejection_is_distinct(monkeypatch):
+    def fake_post(url, headers=None, json=None, timeout=None):
+        return _FakeResp({"rt_cd": "1", "msg_cd": "ORDER_NOT_CANCELLABLE"})
+
+    b = _mock_broker()
+    monkeypatch.setattr(kis_mod.httpx, "post", fake_post)
+    outcome = b.cancel_order(
+        "06010:0000123456",
+        side="buy",
+        symbol="005930",
+        qty=1,
+    )
+
+    assert outcome.state is CancelState.REJECTED
+    assert outcome.reason == "ORDER_NOT_CANCELLABLE"
+
+
+def test_cancel_transport_loss_is_unknown(monkeypatch):
+    def fake_post(url, headers=None, json=None, timeout=None):
+        raise httpx.ReadTimeout("timed out")
+
+    b = _mock_broker()
+    monkeypatch.setattr(kis_mod.httpx, "post", fake_post)
+    outcome = b.cancel_order(
+        "06010:0000123456",
+        side="buy",
+        symbol="005930",
+        qty=1,
+    )
+
+    assert outcome.state is CancelState.UNKNOWN
+    assert outcome.reason == "transport_failed"
+
+
 # ---------------------------------------------------------------------------
 # REQ-118 AC-5: get_current_price 기본 market=J
 # ---------------------------------------------------------------------------
@@ -422,4 +457,4 @@ def test_paper_cancel_backward_compat_no_venue():
     ack = b.submit_order(req)
     # 기존 스타일 호출 (venue 없음)
     result = b.cancel_order(ack.broker_order_id, side="sell", symbol="005930", qty=2)
-    assert result is True
+    assert result.state is CancelState.REQUESTED
diff --git a/tests/adapters/persistence/test_postgresql_slot_repository_parity.py b/tests/adapters/persistence/test_postgresql_slot_repository_parity.py
index df812cf..48afe98 100644
--- a/tests/adapters/persistence/test_postgresql_slot_repository_parity.py
+++ b/tests/adapters/persistence/test_postgresql_slot_repository_parity.py
@@ -35,7 +35,8 @@ _SLOT_COLUMNS = (
     "order_id, strategy_id, broker_order_id, portfolio_id, "
     "sell_strategy_id, forced_close_at, stop_loss_price, take_profit_price, "
     "created_at, updated_at, instance_key, retired_at, "
-    "timeout_sec, slippage_pct, occupancy_seq, venue"
+    "timeout_sec, slippage_pct, occupancy_seq, venue, "
+    "cancel_state, cancel_requested_at"
 )
 _MANAGED_SLOT_SQL = (
     f"SELECT {_SLOT_COLUMNS} FROM daily_slot "
@@ -146,6 +147,8 @@ def _row(slot: Slot) -> tuple:
         Decimal(str(slot.slippage_pct)),
         slot.occupancy_seq,
         slot.venue,
+        slot.cancel_state,
+        slot.cancel_requested_at,
     )
 
 
diff --git a/tests/application/test_execution.py b/tests/application/test_execution.py
index 01fd853..81a7e4f 100644
--- a/tests/application/test_execution.py
+++ b/tests/application/test_execution.py
@@ -7,7 +7,12 @@ from __future__ import annotations
 
 from trex_core.adapters.broker.paper import PaperBroker
 from trex_core.adapters.persistence.in_memory_intent_store import InMemoryIntentStore
-from trex_core.application.broker_port import FillStatus, OrderAck
+from trex_core.application.broker_port import (
+    CancelOutcome,
+    CancelState,
+    FillStatus,
+    OrderAck,
+)
 from trex_core.application.execution import ExecutionService
 from trex_core.application.intents import BuyIntent, IntentService, SellIntent
 from trex_core.domain.slot import SlotService, SlotState
@@ -78,7 +83,10 @@ def test_unknown_submit_outcome_stays_dispatched_without_retry():
 
         def cancel_order(self, broker_order_id, *, side, symbol, qty, venue="KRX"):
             self.cancel_count += 1
-            return False
+            return CancelOutcome(
+                CancelState.UNKNOWN,
+                "submission_outcome_unknown",
+            )
 
     broker = UnknownOutcomeBroker()
     repo, svc, intents, execution = _wire(broker)
diff --git a/tests/application/test_execution_cancel.py b/tests/application/test_execution_cancel.py
index 8baa58a..628a30a 100644
--- a/tests/application/test_execution_cancel.py
+++ b/tests/application/test_execution_cancel.py
@@ -13,7 +13,13 @@ from datetime import datetime, timedelta, timezone
 
 from trex_core.adapters.ledger.in_memory import InMemoryLedger
 from trex_core.adapters.persistence.in_memory_intent_store import InMemoryIntentStore
-from trex_core.application.broker_port import BalanceItem, FillStatus, OrderAck
+from trex_core.application.broker_port import (
+    BalanceItem,
+    CancelOutcome,
+    CancelState,
+    FillStatus,
+    OrderAck,
+)
 from trex_core.application.execution import ExecutionService
 from trex_core.application.intents import BuyIntent, IntentService, SellIntent
 from trex_core.application.ledger_outbox import InMemoryLedgerOutbox, LedgerWriter
@@ -46,8 +52,8 @@ class ProgrammableBroker:
         self.polls += 1
         return self.responder(side)
 
-    def cancel_order(self, broker_order_id, *, side, symbol, qty):
-        return True
+    def cancel_order(self, broker_order_id, *, side, symbol, qty, venue="KRX"):
+        return CancelOutcome(CancelState.REQUESTED)
 
     def get_balance(self):
         # M2 (dcy-020/REQ-062): sell dispatch reads the broker balance.
diff --git a/tests/application/test_execution_fill_price_backfill.py b/tests/application/test_execution_fill_price_backfill.py
index 62a6b7e..6503e5a 100644
--- a/tests/application/test_execution_fill_price_backfill.py
+++ b/tests/application/test_execution_fill_price_backfill.py
@@ -19,6 +19,8 @@ from trex_core.adapters.ledger.in_memory import InMemoryLedger
 from trex_core.adapters.persistence.in_memory_intent_store import InMemoryIntentStore
 from trex_core.application.broker_port import (
     BalanceItem,
+    CancelOutcome,
+    CancelState,
     FillStatus,
     OrderAck,
     OrderRequest,
@@ -83,8 +85,16 @@ class StubBroker:
             return FillStatus(state="unknown")
         return o.fill_status
 
-    def cancel_order(self, broker_order_id: str, *, side: str, symbol: str, qty: int) -> bool:
-        return False
+    def cancel_order(
+        self,
+        broker_order_id: str,
+        *,
+        side: str,
+        symbol: str,
+        qty: int,
+        venue: str = "KRX",
+    ) -> CancelOutcome:
+        return CancelOutcome(CancelState.REJECTED, "order_not_cancellable")
 
     def get_balance(self) -> list[BalanceItem]:
         return [
diff --git a/tests/application/test_execution_policy.py b/tests/application/test_execution_policy.py
index adcbe0b..ed0fe3d 100644
--- a/tests/application/test_execution_policy.py
+++ b/tests/application/test_execution_policy.py
@@ -11,7 +11,14 @@ from datetime import datetime, timedelta, timezone
 
 
 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.broker_port import (
+    BalanceItem,
+    CancelOutcome,
+    CancelState,
+    FillStatus,
+    OrderAck,
+    OrderRequest,
+)
 from trex_core.application.execution import ExecutionService
 from trex_core.application.intents import BuyIntent, IntentService, SellIntent
 from trex_core.domain.slot import SlotService, SlotState
@@ -26,6 +33,7 @@ class _RecordingBroker:
         self.orders: list[OrderRequest] = []
         self.cancel_calls: list = []
         self.cancel_raises = False
+        self.cancel_outcome = CancelOutcome(CancelState.REQUESTED)
         self.responder = lambda side: FillStatus(
             state="filled", filled_qty=10, avg_price=1000.0,
             execution_id="exec-1", fee=0.0, tax=0.0,
@@ -47,7 +55,7 @@ class _RecordingBroker:
         self.cancel_calls.append((broker_order_id, side, symbol, qty, venue))
         if self.cancel_raises:
             raise RuntimeError("broker error")
-        return True
+        return self.cancel_outcome
 
     def get_balance(self):
         return [BalanceItem(symbol=s, hldg_qty=q) for s, q in self.balance.items() if q > 0]
@@ -287,6 +295,9 @@ class TestTimeoutCancel:
         r = execution.run_once()
         assert r.timeout_cancelled == 1
         assert len(broker.cancel_calls) == 1
+        assert repo.fetch_slot(sid).cancel_state == "requested"
+        execution.run_once()
+        assert len(broker.cancel_calls) == 1
 
     def test_timeout_not_exceeded_no_cancel(self):
         broker = _RecordingBroker()
@@ -330,7 +341,12 @@ class TestTimeoutCancel:
             r = execution.run_once()
         # timeout_cancelled NOT incremented when the cancel call raises
         assert r.timeout_cancelled == 0
-        assert repo.fetch_slot(sid).status is SlotState.PENDING_BUY  # state unchanged
+        slot = repo.fetch_slot(sid)
+        assert slot.status is SlotState.PENDING_BUY
+        assert slot.cancel_state == "unknown"
+        execution.run_once()
+        ExecutionService(svc, repo, broker).run_once()
+        assert len(broker.cancel_calls) == 1
 
     def test_timeout_cancel_does_not_change_slot_state(self):
         """Timeout cancel is best-effort: slot stays PENDING_BUY after cancel_order."""
@@ -347,6 +363,28 @@ class TestTimeoutCancel:
         # slot still PENDING_BUY — cancel is best-effort; rollback on next poll
         assert repo.fetch_slot(sid).status is SlotState.PENDING_BUY
 
+    def test_timeout_cancel_rejection_is_persisted_without_retry(self):
+        broker = _RecordingBroker()
+        broker.cancel_outcome = CancelOutcome(
+            CancelState.REJECTED,
+            "broker_rejected",
+        )
+        repo, svc, intents, execution = _wire(broker)
+        sid = _buy_to_pending(intents, timeout_sec=1)
+        broker.responder = lambda side: FillStatus(state="accepted")
+        execution.run_once()
+        slot = repo.fetch_slot(sid)
+        repo._slots[sid] = replace(
+            slot,
+            updated_at=datetime.now(tz=timezone.utc) - timedelta(seconds=60),
+        )
+
+        result = execution.run_once()
+        assert result.timeout_cancelled == 0
+        assert repo.fetch_slot(sid).cancel_state == "rejected"
+        ExecutionService(svc, repo, broker).run_once()
+        assert len(broker.cancel_calls) == 1
+
     def test_timeout_cancel_then_fill_race_handled(self):
         """Cancel sent, but broker fills the order — is_filled path wins on next poll."""
         broker = _RecordingBroker()
@@ -368,7 +406,10 @@ class TestTimeoutCancel:
         )
         r2 = execution.run_once()
         assert r2.filled == 1
-        assert repo.fetch_slot(sid).status is SlotState.HOLDING
+        slot = repo.fetch_slot(sid)
+        assert slot.status is SlotState.HOLDING
+        assert slot.cancel_state is None
+        assert slot.cancel_requested_at is None
 
 
 # ============================================================================
@@ -418,7 +459,7 @@ class TestCancelPendingSlot:
         result = execution.cancel_pending_slot(sid)
         assert result == "not_dispatched"
 
-    def test_cancel_fail_returns_cancel_failed(self):
+    def test_cancel_exception_returns_unknown(self):
         broker = _RecordingBroker()
         broker.cancel_raises = True
         repo, svc, intents, execution = _wire(broker)
@@ -427,7 +468,22 @@ class TestCancelPendingSlot:
         execution.run_once()  # dispatch
 
         result = execution.cancel_pending_slot(sid)
-        assert result == "cancel_failed"
+        assert result == "cancel_unknown"
+        assert repo.fetch_slot(sid).cancel_state == "unknown"
+
+    def test_cancel_rejected_is_distinct_and_persisted(self):
+        broker = _RecordingBroker()
+        broker.cancel_outcome = CancelOutcome(
+            CancelState.REJECTED,
+            "broker_rejected",
+        )
+        repo, svc, intents, execution = _wire(broker)
+        sid = _buy_to_pending(intents)
+        broker.responder = lambda side: FillStatus(state="accepted")
+        execution.run_once()
+
+        assert execution.cancel_pending_slot(sid) == "cancel_rejected"
+        assert repo.fetch_slot(sid).cancel_state == "rejected"
 
     def test_cancel_does_not_change_slot_state(self):
         """Operator cancel sends cancel_order; slot stays PENDING_BUY (execution loop transitions)."""
diff --git a/tests/application/test_venue_intent_flow.py b/tests/application/test_venue_intent_flow.py
index 19a50d2..aee5e22 100644
--- a/tests/application/test_venue_intent_flow.py
+++ b/tests/application/test_venue_intent_flow.py
@@ -4,7 +4,14 @@ 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.broker_port import (
+    BalanceItem,
+    CancelOutcome,
+    CancelState,
+    FillStatus,
+    OrderAck,
+    OrderRequest,
+)
 from trex_core.application.execution import ExecutionService
 from trex_core.application.intents import BuyIntent, IntentService
 from trex_core.application.messaging import RpcRequest
@@ -38,9 +45,9 @@ class RecordingBroker:
         symbol: str,
         qty: int,
         venue: str = "KRX",
-    ) -> bool:
+    ) -> CancelOutcome:
         self.cancel_venues.append(venue)
-        return True
+        return CancelOutcome(CancelState.REQUESTED)
 
     def get_balance(self) -> list[BalanceItem]:
         return []
diff --git a/trex_core/adapters/broker/kis.py b/trex_core/adapters/broker/kis.py
index f78bce3..50be9f6 100644
--- a/trex_core/adapters/broker/kis.py
+++ b/trex_core/adapters/broker/kis.py
@@ -24,6 +24,8 @@ import httpx
 from trex_core.application.broker_port import (
     BalanceItem,
     BrokerBalanceError,
+    CancelOutcome,
+    CancelState,
     FillStatus,
     OrderAck,
     OrderRequest,
@@ -756,7 +758,7 @@ class KISBroker:
 
     def cancel_order(
         self, broker_order_id: str, *, side: str, symbol: str, qty: int, venue: str = "KRX"
-    ) -> bool:
+    ) -> CancelOutcome:
         """Cancel a previously submitted order (REQ-118).
 
         venue: exchange venue of the original order. Must match the EXCG_ID_DVSN_CD
@@ -764,7 +766,10 @@ class KISBroker:
         Real-account NXT cancel (EXCG=NXT) confirmed rt_cd=0 on 2026-07-06.
         """
         if broker_order_id.startswith(_SUBMISSION_UNKNOWN_PREFIX):
-            return False
+            return CancelOutcome(
+                CancelState.UNKNOWN,
+                "submission_outcome_unknown",
+            )
         cano, product = self._account()
         parts = broker_order_id.split(":")
         orgno, odno = (parts[0], parts[1]) if len(parts) == 2 else ("", parts[-1])
@@ -789,6 +794,22 @@ class KISBroker:
                 json=body,
                 timeout=self._timeout,
             )
-            return str(resp.json().get("rt_cd")) == "0"
-        except (httpx.HTTPError, ValueError):
-            return False
+        except httpx.HTTPError:
+            return CancelOutcome(CancelState.UNKNOWN, "transport_failed")
+        if getattr(resp, "status_code", 200) >= 500:
+            return CancelOutcome(CancelState.UNKNOWN, "broker_unavailable")
+        try:
+            payload = resp.json()
+        except ValueError:
+            return CancelOutcome(CancelState.UNKNOWN, "malformed_response")
+        rt_cd = payload.get("rt_cd")
+        if str(rt_cd) == "0":
+            return CancelOutcome(CancelState.REQUESTED)
+        if rt_cd is None:
+            if getattr(resp, "status_code", 200) >= 400:
+                return CancelOutcome(CancelState.REJECTED, "http_rejected")
+            return CancelOutcome(CancelState.UNKNOWN, "missing_result_code")
+        return CancelOutcome(
+            CancelState.REJECTED,
+            str(payload.get("msg_cd") or "broker_rejected"),
+        )
diff --git a/trex_core/adapters/broker/ownership.py b/trex_core/adapters/broker/ownership.py
index cd57e28..4c99375 100644
--- a/trex_core/adapters/broker/ownership.py
+++ b/trex_core/adapters/broker/ownership.py
@@ -16,6 +16,7 @@ from threading import Lock
 from trex_core.application.broker_port import (
     BalanceItem,
     BrokerBalanceError,
+    CancelOutcome,
     FillStatus,
     OrderAck,
     OrderRequest,
@@ -146,7 +147,7 @@ class OwnershipAwareBroker:
         symbol: str,
         qty: int,
         venue: str = "KRX",
-    ) -> bool:
+    ) -> CancelOutcome:
         return self._delegate.cancel_order(
             broker_order_id,
             side=side,
diff --git a/trex_core/adapters/broker/paper.py b/trex_core/adapters/broker/paper.py
index 017409b..e95ffc6 100644
--- a/trex_core/adapters/broker/paper.py
+++ b/trex_core/adapters/broker/paper.py
@@ -14,6 +14,8 @@ from typing import Optional
 from trex_core.adapters.broker.seq_store import SeqStore
 from trex_core.application.broker_port import (
     BalanceItem,
+    CancelOutcome,
+    CancelState,
     FillStatus,
     OrderAck,
     OrderRequest,
@@ -105,16 +107,24 @@ class PaperBroker:
                 )
             return FillStatus(state="partially_filled", filled_qty=o.filled, avg_price=o.price)
 
-    def cancel_order(self, broker_order_id: str, *, side: str, symbol: str, qty: int, venue: str = "KRX") -> bool:
+    def cancel_order(
+        self,
+        broker_order_id: str,
+        *,
+        side: str,
+        symbol: str,
+        qty: int,
+        venue: str = "KRX",
+    ) -> CancelOutcome:
         """Cancel a paper order. venue is accepted for BrokerPort protocol conformance
         (REQ-118) but ignored — paper has no exchange concept. Existing behavior preserved.
         """
         with self._lock:
             o = self._orders.get(broker_order_id)
             if o is None or o.filled >= o.qty:
-                return False
+                return CancelOutcome(CancelState.REJECTED, "order_not_cancellable")
             o.cancelled = True
-            return True
+            return CancelOutcome(CancelState.REQUESTED)
 
     def get_balance(self) -> list[BalanceItem]:
         """Deterministic per-symbol fill aggregate (REQ-031 AC-3).
diff --git a/trex_core/adapters/persistence/postgresql.py b/trex_core/adapters/persistence/postgresql.py
index 36da514..64471b6 100644
--- a/trex_core/adapters/persistence/postgresql.py
+++ b/trex_core/adapters/persistence/postgresql.py
@@ -37,7 +37,8 @@ _SLOT_COLUMNS = (
     "order_id, strategy_id, broker_order_id, portfolio_id, "
     "sell_strategy_id, forced_close_at, stop_loss_price, take_profit_price, "
     "created_at, updated_at, instance_key, retired_at, "
-    "timeout_sec, slippage_pct, occupancy_seq, venue"
+    "timeout_sec, slippage_pct, occupancy_seq, venue, "
+    "cancel_state, cancel_requested_at"
 )
 
 
@@ -216,7 +217,8 @@ class PostgreSQLSlotRepository:
                     "broker_order_id=%s, portfolio_id=%s, sell_strategy_id=%s, "
                     "forced_close_at=%s, stop_loss_price=%s, take_profit_price=%s, "
                     "instance_key=%s, retired_at=%s, timeout_sec=%s, slippage_pct=%s, "
-                    "occupancy_seq=%s, venue=%s, updated_at=%s WHERE slot_id=%s",
+                    "occupancy_seq=%s, venue=%s, cancel_state=%s, "
+                    "cancel_requested_at=%s, updated_at=%s WHERE slot_id=%s",
                     (
                         slot.status.value,
                         slot.symbol,
@@ -237,6 +239,8 @@ class PostgreSQLSlotRepository:
                         slot.slippage_pct,
                         slot.occupancy_seq,
                         slot.venue,
+                        slot.cancel_state,
+                        slot.cancel_requested_at,
                         slot.updated_at or datetime.now(tz=timezone.utc),
                         slot.slot_id,
                     ),
@@ -332,6 +336,26 @@ class PostgreSQLSlotRepository:
                 conn.commit()
                 return ok
 
+    def mark_cancel_outcome(
+        self,
+        slot_id: UUID,
+        broker_order_id: str,
+        state: str,
+    ) -> bool:
+        now = datetime.now(tz=timezone.utc)
+        with self._psycopg.connect(self._dsn, autocommit=False) as conn:
+            with conn.cursor() as cur:
+                cur.execute(
+                    "UPDATE daily_slot SET cancel_state=%s, "
+                    "cancel_requested_at=%s, updated_at=%s "
+                    "WHERE slot_id=%s AND broker_order_id=%s "
+                    "AND status IN ('pending_buy','pending_sell')",
+                    (state, now, now, slot_id, broker_order_id),
+                )
+                ok = cur.rowcount == 1
+                conn.commit()
+                return ok
+
     def list_dispatched_pending(self, instance_key: str = "default") -> list[Slot]:
         with self._psycopg.connect(self._dsn) as conn:
             with conn.cursor() as cur:
@@ -347,7 +371,8 @@ class PostgreSQLSlotRepository:
         with self._psycopg.connect(self._dsn, autocommit=False) as conn:
             with conn.cursor() as cur:
                 cur.execute(
-                    "UPDATE daily_slot SET broker_order_id=NULL, updated_at=%s WHERE slot_id=%s",
+                    "UPDATE daily_slot SET broker_order_id=NULL, cancel_state=NULL, "
+                    "cancel_requested_at=NULL, updated_at=%s WHERE slot_id=%s",
                     (datetime.now(tz=timezone.utc), slot_id),
                 )
                 conn.commit()
@@ -374,7 +399,8 @@ class PostgreSQLSlotRepository:
         # forced_close_at(11) stop_loss_price(12) take_profit_price(13)
         # created_at(14) updated_at(15) instance_key(16) retired_at(17)
         # timeout_sec(18) slippage_pct(19)  [dcy-022/REQ-068]
-        # occupancy_seq(20)  [dcy-028/REQ-081], venue(21)
+        # occupancy_seq(20) [dcy-028/REQ-081], venue(21),
+        # cancel_state(22), cancel_requested_at(23)
         return Slot(
             slot_id=row[0] if isinstance(row[0], UUID) else UUID(str(row[0])),
             status=SlotState(row[1]),
@@ -398,6 +424,8 @@ class PostgreSQLSlotRepository:
             slippage_pct=f(row[19]),
             occupancy_seq=int(row[20]) if len(row) > 20 and row[20] is not None else 0,
             venue=str(row[21]) if len(row) > 21 and row[21] is not None else "KRX",
+            cancel_state=str(row[22]) if len(row) > 22 and row[22] is not None else None,
+            cancel_requested_at=row[23] if len(row) > 23 else None,
         )
 
 
diff --git a/trex_core/adapters/persistence/sql/020_persist_cancel_request_outcome.sql b/trex_core/adapters/persistence/sql/020_persist_cancel_request_outcome.sql
new file mode 100644
index 0000000..b1fe153
--- /dev/null
+++ b/trex_core/adapters/persistence/sql/020_persist_cancel_request_outcome.sql
@@ -0,0 +1,18 @@
+-- dcy-041 / GitHub #44: cancellation request acceptance is distinct from
+-- final order cancellation. Persist the immediate result to prevent blind
+-- automatic retries across execution ticks and daemon restarts.
+ALTER TABLE daily_slot
+    ADD COLUMN IF NOT EXISTS cancel_state TEXT;
+
+ALTER TABLE daily_slot
+    ADD COLUMN IF NOT EXISTS cancel_requested_at TIMESTAMPTZ;
+
+ALTER TABLE daily_slot
+    DROP CONSTRAINT IF EXISTS daily_slot_cancel_state_check;
+
+ALTER TABLE daily_slot
+    ADD CONSTRAINT daily_slot_cancel_state_check
+    CHECK (
+        cancel_state IS NULL
+        OR cancel_state IN ('requested', 'rejected', 'unknown')
+    );
diff --git a/trex_core/application/broker_port.py b/trex_core/application/broker_port.py
index e9bbc73..7828198 100644
--- a/trex_core/application/broker_port.py
+++ b/trex_core/application/broker_port.py
@@ -10,6 +10,7 @@ from __future__ import annotations
 import os
 from dataclasses import dataclass, field
 from decimal import Decimal
+from enum import Enum
 from typing import Any, Optional, Protocol
 
 
@@ -29,6 +30,30 @@ class BrokerBalanceError(RuntimeError):
         super().__init__(f"broker balance unavailable ({code})")
 
 
+class CancelState(str, Enum):
+    """Immediate result of a cancel request, not the final order state."""
+
+    REQUESTED = "requested"
+    REJECTED = "rejected"
+    UNKNOWN = "unknown"
+
+
+@dataclass(frozen=True)
+class CancelOutcome:
+    """Sanitized cancel request outcome.
+
+    REQUESTED only means that the broker accepted the cancellation request.
+    Final cancelled/filled state is established exclusively by poll_fill().
+    """
+
+    state: CancelState
+    reason: Optional[str] = None
+
+    @property
+    def is_requested(self) -> bool:
+        return self.state is CancelState.REQUESTED
+
+
 @dataclass(frozen=True)
 class OrderRequest:
     slot_id: str          # originating slot (audit/correlation)
@@ -114,12 +139,23 @@ class BrokerPort(Protocol):
         """Observe current fill status for a previously accepted order."""
         ...
 
-    def cancel_order(self, broker_order_id: str, *, side: str, symbol: str, qty: int, venue: str = "KRX") -> bool:
-        """Best-effort cancel. Returns True if the broker accepted the cancel.
+    def cancel_order(
+        self,
+        broker_order_id: str,
+        *,
+        side: str,
+        symbol: str,
+        qty: int,
+        venue: str = "KRX",
+    ) -> CancelOutcome:
+        """Request cancellation and classify the immediate broker outcome.
 
         venue: exchange venue of the original order (REQ-118). Cancel must use
         the same EXCG_ID_DVSN_CD as the original submit. Default "KRX" preserves
         backward compatibility for existing callers (orb/tsl).
+
+        REQUESTED is not a final cancellation. poll_fill() remains the only
+        authority for cancelled/filled terminal state.
         """
         ...
 
diff --git a/trex_core/application/execution.py b/trex_core/application/execution.py
index 2a8d874..2ea4d91 100644
--- a/trex_core/application/execution.py
+++ b/trex_core/application/execution.py
@@ -29,7 +29,12 @@ from datetime import datetime, timezone
 from typing import Callable, Optional
 
 from trex_core.application.alarm_emitter import AlarmEmitter
-from trex_core.application.broker_port import BrokerPort, OrderRequest
+from trex_core.application.broker_port import (
+    BrokerPort,
+    CancelOutcome,
+    CancelState,
+    OrderRequest,
+)
 from trex_core.application.ledger_outbox import LedgerOutbox
 from trex_core.application.ledger_port import LedgerTrade
 from trex_core.domain.pricing import ceil_to_tick, floor_to_tick
@@ -546,12 +551,28 @@ class ExecutionService:
         """
         if str(slot.broker_order_id or "").startswith("submission-unknown:"):
             return
+        if slot.cancel_state is not None:
+            return
         if slot.timeout_sec is None or slot.updated_at is None:
             return
         age = (now - slot.updated_at).total_seconds()
         if age < slot.timeout_sec:
             return
         qty = int(slot.qty or 0)
+        # Write UNKNOWN before external I/O. If the process dies after KIS
+        # receives the request but before the response is persisted, restart
+        # polls the order instead of issuing a blind second cancellation.
+        if not self._repo.mark_cancel_outcome(
+            slot.slot_id,
+            str(slot.broker_order_id),
+            CancelState.UNKNOWN.value,
+        ):
+            _log.error(
+                "cancel attempt reservation conflict: slot=%s broker_order_id=%s",
+                slot.slot_id,
+                slot.broker_order_id,
+            )
+            return
         try:
             cancel_kwargs = {
                 "side": side,
@@ -560,25 +581,40 @@ class ExecutionService:
             }
             if slot.venue != "KRX":
                 cancel_kwargs["venue"] = slot.venue
-            accepted = self._broker.cancel_order(slot.broker_order_id, **cancel_kwargs)
+            outcome = self._broker.cancel_order(slot.broker_order_id, **cancel_kwargs)
+        except Exception:  # noqa: BLE001 - adapter failure becomes durable unknown
+            outcome = CancelOutcome(CancelState.UNKNOWN, "adapter_exception")
+            _log.warning(
+                "timeout cancel outcome unknown: slot=%s broker_order_id=%s",
+                slot.slot_id,
+                slot.broker_order_id,
+            )
+        persisted = self._repo.mark_cancel_outcome(
+            slot.slot_id,
+            str(slot.broker_order_id),
+            outcome.state.value,
+        )
+        if not persisted:
+            _log.error(
+                "cancel outcome persistence conflict: slot=%s broker_order_id=%s "
+                "outcome=%s",
+                slot.slot_id,
+                slot.broker_order_id,
+                outcome.state.value,
+            )
+            return
+        if outcome.is_requested:
             r.timeout_cancelled += 1
-            _log.warning(
-                "timeout cancel sent: slot=%s status=%s broker_order_id=%s "
-                "age_sec=%.0f timeout_sec=%d broker_accepted=%s",
-                slot.slot_id,
-                slot.status.value,
-                slot.broker_order_id,
-                age,
-                slot.timeout_sec,
-                accepted,
-            )
-        except Exception:  # noqa: BLE001 - best-effort; do not block the loop
-            _log.warning(
-                "timeout cancel failed (exception): slot=%s broker_order_id=%s "
-                "(will retry next tick if still pending)",
-                slot.slot_id,
-                slot.broker_order_id,
-            )
+        _log.warning(
+            "timeout cancel result: slot=%s status=%s broker_order_id=%s "
+            "age_sec=%.0f timeout_sec=%d outcome=%s",
+            slot.slot_id,
+            slot.status.value,
+            slot.broker_order_id,
+            age,
+            slot.timeout_sec,
+            outcome.state.value,
+        )
 
     def _emit_event(self, event_type: str, slot, routing_strategy_id: Optional[str] = None) -> None:
         if self._event_emitter is None:
@@ -655,9 +691,9 @@ class ExecutionService:
     def cancel_pending_slot(self, slot_id) -> str:
         """Operator backstop: send cancel_order for a pending slot (dcy-022/REQ-071).
 
-        Returns "ok" (cancel sent), "not_pending" (slot is HOLDING/INACTIVE),
-        or "slot_not_found". Does NOT transition the slot — the execution loop's
-        next poll handles the rollback via the normal is_terminal_reject path.
+        Returns "ok" (request accepted), "cancel_rejected", "cancel_unknown",
+        "not_pending", "not_dispatched", or "slot_not_found". Does NOT
+        transition the slot — fill polling alone confirms cancelled/filled.
         """
         from uuid import UUID
 
@@ -680,21 +716,40 @@ class ExecutionService:
             }
             if slot.venue != "KRX":
                 cancel_kwargs["venue"] = slot.venue
-            self._broker.cancel_order(slot.broker_order_id, **cancel_kwargs)
-        except Exception:  # noqa: BLE001 - best-effort
+            # Durable unknown reservation closes the crash window between the
+            # outbound request and saving its immediate result.
+            if not self._repo.mark_cancel_outcome(
+                slot.slot_id,
+                str(slot.broker_order_id),
+                CancelState.UNKNOWN.value,
+            ):
+                return "cancel_state_conflict"
+            outcome = self._broker.cancel_order(slot.broker_order_id, **cancel_kwargs)
+        except Exception:  # noqa: BLE001 - adapter failure becomes durable unknown
+            outcome = CancelOutcome(CancelState.UNKNOWN, "adapter_exception")
             _log.warning(
-                "operator cancel failed: slot=%s broker_order_id=%s",
+                "operator cancel outcome unknown: slot=%s broker_order_id=%s",
                 slot.slot_id,
                 slot.broker_order_id,
             )
-            return "cancel_failed"
+        if not self._repo.mark_cancel_outcome(
+            slot.slot_id,
+            str(slot.broker_order_id),
+            outcome.state.value,
+        ):
+            return "cancel_state_conflict"
         _log.warning(
-            "operator cancel sent: slot=%s status=%s broker_order_id=%s",
+            "operator cancel result: slot=%s status=%s broker_order_id=%s outcome=%s",
             slot.slot_id,
             slot.status.value,
             slot.broker_order_id,
+            outcome.state.value,
         )
-        return "ok"
+        if outcome.state is CancelState.REQUESTED:
+            return "ok"
+        if outcome.state is CancelState.REJECTED:
+            return "cancel_rejected"
+        return "cancel_unknown"
 
     def _rollback(self, slot, *, reason: str) -> None:
         total = self._balance_map().get(slot.symbol or "", 0)
diff --git a/trex_core/domain/slot/in_memory_repository.py b/trex_core/domain/slot/in_memory_repository.py
index f4420f8..42421fc 100644
--- a/trex_core/domain/slot/in_memory_repository.py
+++ b/trex_core/domain/slot/in_memory_repository.py
@@ -219,6 +219,29 @@ class InMemorySlotRepository:
         )
         return True
 
+    def mark_cancel_outcome(
+        self,
+        slot_id: UUID,
+        broker_order_id: str,
+        state: str,
+    ) -> bool:
+        """Persist one cancel attempt iff the same order is still pending."""
+        s = self._slots.get(slot_id)
+        if (
+            s is None
+            or s.broker_order_id != broker_order_id
+            or s.status not in self._PENDING
+        ):
+            return False
+        now = datetime.now(tz=timezone.utc)
+        self._slots[slot_id] = replace(
+            s,
+            cancel_state=state,
+            cancel_requested_at=now,
+            updated_at=now,
+        )
+        return True
+
     def list_dispatched_pending(self, instance_key: str = "default") -> list[Slot]:
         """Pending slots already dispatched (broker_order_id NOT NULL) — poll targets."""
         return [
@@ -236,7 +259,11 @@ class InMemorySlotRepository:
         s = self._slots.get(slot_id)
         if s is not None:
             self._slots[slot_id] = replace(
-                s, broker_order_id=None, updated_at=datetime.now(tz=timezone.utc)
+                s,
+                broker_order_id=None,
+                cancel_state=None,
+                cancel_requested_at=None,
+                updated_at=datetime.now(tz=timezone.utc),
             )
 
     # --- bulk counts ---
diff --git a/trex_core/domain/slot/models.py b/trex_core/domain/slot/models.py
index 1b584e2..c1a7543 100644
--- a/trex_core/domain/slot/models.py
+++ b/trex_core/domain/slot/models.py
@@ -59,6 +59,11 @@ class Slot:
     # Order venue carried from the admitted intent through dispatch/cancel.
     # It is reset to KRX when the permanent asset slot returns to INACTIVE.
     venue: str = "KRX"
+    # Immediate cancel-request result. The slot remains pending until fill
+    # polling confirms cancelled/filled. Persisted to prevent blind retries
+    # across ticks and restarts.
+    cancel_state: Optional[str] = None
+    cancel_requested_at: Optional[datetime] = None
 
 
 # Canonical column contract for `Slot` (dcy-001 OQ-2 / FR-5).
@@ -88,6 +93,8 @@ EXPECTED_SLOT_FIELDS: frozenset[str] = frozenset({
     "slippage_pct",       # dcy-022 / REQ-068 (BAT-032)
     "occupancy_seq",      # dcy-028 / REQ-081 (BAT-042)
     "venue",
+    "cancel_state",
+    "cancel_requested_at",
 })
 
 
diff --git a/trex_core/domain/slot/service.py b/trex_core/domain/slot/service.py
index 6767d14..34cd171 100644
--- a/trex_core/domain/slot/service.py
+++ b/trex_core/domain/slot/service.py
@@ -205,6 +205,8 @@ class SlotService:
                 timeout_sec=None,
                 slippage_pct=None,
                 venue="KRX",
+                cancel_state=None,
+                cancel_requested_at=None,
                 updated_at=datetime.now(tz=timezone.utc),
             )
 
@@ -277,6 +279,8 @@ class SlotService:
             slippage_pct=new_slippage_pct,
             occupancy_seq=new_occupancy_seq,
             venue=new_venue,
+            cancel_state=None,
+            cancel_requested_at=None,
             updated_at=datetime.now(tz=timezone.utc),
         )