diff --git a/MALKHUT/malkhut/cwm/core.py b/MALKHUT/malkhut/cwm/core.py
index 4ef0663..fb525ab 100644
--- a/MALKHUT/malkhut/cwm/core.py
+++ b/MALKHUT/malkhut/cwm/core.py
@@ -333,6 +333,7 @@ class MinimalCryptoLOBCWM:
             last_update_ts_ns=ts,
             reduce_only=action.reduce_only,
             post_only=action.post_only,
+            ttl_ms=action.ttl_ms if action.ttl_ms > 0 else 0,
         )
 
     def transition(
@@ -356,6 +357,17 @@ class MinimalCryptoLOBCWM:
             if our_action.kind.value == "CANCEL_REPLACE" and our_action.cancel_order_id:
                 open_orders = [o for o in open_orders if o.client_order_id != our_action.cancel_order_id]
 
+        # 1b. TTL enforcement — auto-cancel expired open orders (CHASE mechanic)
+        if open_orders:
+            alive = []
+            for oo in open_orders:
+                age_ms = (now_ts - oo.created_ts_ns) / 1_000_000
+                ttl = getattr(oo, 'ttl_ms', 0)
+                if ttl > 0 and age_ms >= ttl:
+                    continue  # expired
+                alive.append(oo)
+            open_orders = alive
+
         # 2. Process counterparty cancels
         for cp in counterparty_actions:
             if isinstance(cp, CounterpartyAction) and cp.kind.value == "CANCEL":
diff --git a/MALKHUT/malkhut/cwm/hft_cwm.py b/MALKHUT/malkhut/cwm/hft_cwm.py
index 6234647..cea7ab8 100644
--- a/MALKHUT/malkhut/cwm/hft_cwm.py
+++ b/MALKHUT/malkhut/cwm/hft_cwm.py
@@ -202,6 +202,7 @@ class HftBacktestCWM:
             last_update_ts_ns=ts,
             reduce_only=action.reduce_only,
             post_only=action.post_only,
+            ttl_ms=action.ttl_ms if action.ttl_ms > 0 else 0,
         )
 
     def transition(
@@ -225,7 +226,22 @@ class HftBacktestCWM:
             if our_action.kind.value == "CANCEL_REPLACE" and our_action.cancel_order_id:
                 open_orders = [o for o in open_orders if o.client_order_id != our_action.cancel_order_id]
 
-        # 2. Process counterparty cancels
+        # 2. TTL enforcement — auto-cancel expired open orders (CHASE mechanic)
+        # Orders with ttl_ms > 0 expire after ttl_ms. This is how CHASE works:
+        # place → wait → auto-cancel → next step re-places at new offset.
+        if open_orders:
+            alive = []
+            for oo in open_orders:
+                age_ms = (now_ts - oo.created_ts_ns) / 1_000_000
+                if oo.last_update_ts_ns > oo.created_ts_ns:
+                    age_ms = (now_ts - oo.last_update_ts_ns) / 1_000_000
+                ttl = oo.ttl_ms
+                if ttl > 0 and age_ms >= ttl:
+                    continue  # expired — auto-cancel
+                alive.append(oo)
+            open_orders = alive
+
+        # 3. Process counterparty cancels
         for cp in counterparty_actions:
             if isinstance(cp, CounterpartyAction) and cp.kind.value == "CANCEL":
                 open_orders = [o for o in open_orders if o.symbol != state.venue.symbol]
diff --git a/MALKHUT/malkhut/state.py b/MALKHUT/malkhut/state.py
index 30a82eb..9bccbc9 100644
--- a/MALKHUT/malkhut/state.py
+++ b/MALKHUT/malkhut/state.py
@@ -210,6 +210,7 @@ class OpenOrderState:
     last_update_ts_ns: int
     reduce_only: bool = False
     post_only: bool = False
+    ttl_ms: int = 0  # 0 = no expiry; >0 = auto-cancel after ttl_ms (CHASE)
 
 
 @dataclass(frozen=True, slots=True)
diff --git a/MALKHUT/malkhut/tests/test_hft_cwm.py b/MALKHUT/malkhut/tests/test_hft_cwm.py
index 2fde3af..fb11e09 100644
--- a/MALKHUT/malkhut/tests/test_hft_cwm.py
+++ b/MALKHUT/malkhut/tests/test_hft_cwm.py
@@ -716,3 +716,85 @@ class TestHftAvailability:
         assert cwm._use_queue_model is False
         assert cwm._fill_probability_at_level(0) == 1.0
         assert cwm._fill_probability_at_level(50) == 1.0
+
+
+# ==============================================================================
+# PART 16: CHASE Mechanics
+# ==============================================================================
+
+class TestChaseMechanics:
+    def test_ttl_enforcement_cancels_expired_order(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        # Place order with TTL=1ms
+        a = _place(Side.BUY, price_ticks=5, qty=0.10)
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 1, post_only=True)  # ttl_ms=1
+        s2 = cwm.transition(s, (a,))
+        assert len(s2.open_orders) == 1
+
+        # Next step: order should be expired (1ms < 1ms tick)
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+        s3 = cwm.transition(s2, (noop,))
+        assert len(s3.open_orders) == 0
+
+    def test_ttl_zero_means_no_expiry(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 0, post_only=True)  # ttl_ms=0
+        s2 = cwm.transition(s, (a,))
+        assert len(s2.open_orders) == 1
+
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+        s3 = cwm.transition(s2, (noop,))
+        assert len(s3.open_orders) == 1  # not expired
+
+    def test_chase_action_has_ttl(self):
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             5, 0.10, 100, post_only=True, metadata={"chase": True})
+        assert a.ttl_ms == 100
+
+    def test_chase_cancel_retry_cycle(self):
+        cwm = HftBacktestCWM(use_queue_model=False)
+        s = _state()
+        noop = FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)
+
+        # Step 1: Place chase order with short TTL
+        a1 = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                              5, 0.10, 1, post_only=True, metadata={"chase": True})
+        s1 = cwm.transition(s, (a1,))
+        assert len(s1.open_orders) == 1
+
+        # Step 2: Order expired (TTL=1ms)
+        s2 = cwm.transition(s1, (noop,))
+        assert len(s2.open_orders) == 0
+
+        # Step 3: Re-place at offset 3 (simulating cancel-retry)
+        a3 = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                              3, 0.10, 1, post_only=True, metadata={"chase": True})
+        s3 = cwm.transition(s2, (a3,))
+        assert len(s3.open_orders) == 1
+        assert s3.open_orders[0].price != s1.open_orders[0].price  # different offset
+
+    def test_chase_max_retries_in_metadata(self):
+        a = FulfilmentAction(ActionKind.PLACE, Side.BUY, OrderType.LIMIT,
+                             2, 0.10, 100, post_only=True,
+                             metadata={"chase": True, "chase_max_retries": 3})
+        assert a.metadata["chase_max_retries"] == 3
+
+    def test_wait_to_retry_in_params(self):
+        p = _params()
+        assert p.wait_to_retry_ms == 0
+        assert p.chase_enabled is False
+        assert p.chase_offset_ticks == 1
+        assert p.chase_max_retries == 0
+
+    def test_cma_codec_includes_chase_params(self):
+        from malkhut.training.cma_trainer import CMAParameterCodec
+        codec = CMAParameterCodec()
+        param_names = [s.name for s in codec.SPECS]
+        assert "wait_to_retry_ms" in param_names
+        assert "chase_offset_ticks" in param_names
+        assert "chase_max_retries" in param_names
+        assert "urgency_taker_threshold" in param_names
diff --git a/MALKHUT/malkhut/training/dsl.py b/MALKHUT/malkhut/training/dsl.py
index 4d96607..f68aeeb 100644
--- a/MALKHUT/malkhut/training/dsl.py
+++ b/MALKHUT/malkhut/training/dsl.py
@@ -712,6 +712,19 @@ def _primitive_to_action(primitive: ActionPrimitive, state: MarketWorldState) ->
             ttl_ms=int(primitive.duration_s * 1000), post_only=True,
         )
 
+    elif at == ActionType.CHASE:
+        # Chase: place at target with short TTL. CWM auto-cancels when TTL expires.
+        # Next step the planner re-places at new offset (cancel-retry across CWM steps).
+        # Key: uses primitive.duration_s as the wait_to_retry_ms (how long before cancel).
+        ttl = int(primitive.duration_s * 1000) if primitive.duration_s > 0 else 100
+        return FulfilmentAction(
+            kind=ActionKind.PLACE, side=primitive.side, order_type=OrderType.LIMIT,
+            price_ticks_from_best=primitive.offset_ticks, qty_fraction=primitive.size_fraction,
+            ttl_ms=ttl, post_only=True,
+            metadata={"chase": True, "chase_offset": primitive.offset_ticks,
+                      "chase_ttl_ms": ttl, "chase_target": "follow_price"},
+        )
+
     return FulfilmentAction(ActionKind.NOOP, None, None, 0, 0.0, 0)