diff --git a/Assets/Scripts/Mechanics/GameOptimizer.cs b/Assets/Scripts/Mechanics/GameOptimizer.cs
index 30de1fb..32d5b70 100644
--- a/Assets/Scripts/Mechanics/GameOptimizer.cs
+++ b/Assets/Scripts/Mechanics/GameOptimizer.cs
@@ -16,30 +16,29 @@ namespace Platformer.Mechanics
             QualitySettings.vSyncCount = 0;
             Time.fixedDeltaTime = 1f / 60f;
 
-            // BT5-Dev #22 — Layer 영역 분리: Player(13) ↔ Enemy(14) 충돌 영구 OFF.
-            // IgnoreCollision 영역 instance 의존 X = 모든 Player·Enemy 영역 자동 통과 영역.
+            // BT5-Dev #22 — Player(13) ↔ Enemy(14) 충돌 영구 OFF
             Physics2D.IgnoreLayerCollision(13, 14, true);
-            Debug.Log($"[BT22-LayerSep] Player(13) ↔ Enemy(14) collision OFF");
+            // BT5-Dev #27 — Player(13) ↔ JumpThrough(8) 충돌 기본 OFF (Raycast 시점만 동적 활성)
+            Physics2D.IgnoreLayerCollision(13, 8, true);
+            Debug.Log($"[BT27-LayerSep] Player(13) ↔ Enemy(14)·JumpThrough(8) collision OFF");
         }
 
         /// <summary>
-        /// PD 지시 2026-05-07 — 모든 지형 Collider2D를 One-Way Platform으로 자동 변환.
-        /// 위에서만 착지·측면·아래 통과. Player·Enemy·DeathZone·VictoryZone·TokenInstance·Trigger Collider 영역 제외.
+        /// BT5-Dev #27 — PD 제안: Layer 8(JumpThrough) + Raycast 동적 충돌.
+        /// PlatformEffector2D 폐기. 모든 일반 BoxCollider2D를 Layer 8로 변환 → 기본 통과 + Player 발 Raycast 시점만 충돌 활성.
+        /// 제외: Tilemap·Player·Enemy·DeathZone·VictoryZone·TokenInstance·AttackHitbox·Trigger Collider.
         /// </summary>
         [RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterSceneLoad)]
-        static void SetupOneWayPlatforms()
+        static void SetupJumpThroughPlatforms()
         {
-            // BT5-Dev #25 — Tilemap 영역 OneWay 영역 폐기 (모든 Tile 영역 OneWay = 일반 지면 영역도 영역 = 게임 영역 깨짐)
-            // 별개 BoxCollider2D 영역 영역 영역 영역 영역 영역 발판 영역 영역 OneWay 영역 영역 적용
-            int applied = 0;
-            int excludedTrigger = 0, excludedActor = 0, excludedTilemap = 0;
+            int applied = 0, excluded = 0;
             var allColliders = Object.FindObjectsByType<Collider2D>(FindObjectsSortMode.None);
             var appliedNames = new System.Collections.Generic.List<string>();
             foreach (var c in allColliders)
             {
                 if (c == null) continue;
-                if (c.isTrigger) { excludedTrigger++; continue; }
-                if (c.GetComponent<UnityEngine.Tilemaps.TilemapCollider2D>() != null) { excludedTilemap++; continue; }  // BT25 — Tilemap 영역 영역 영역 일반 충돌 영역
+                if (c.isTrigger) { excluded++; continue; }
+                if (c.GetComponent<UnityEngine.Tilemaps.TilemapCollider2D>() != null) { excluded++; continue; }
                 if (c.GetComponent<PlayerController>() != null
                     || c.GetComponent<EnemyController>() != null
                     || c.GetComponent<DeathZone>() != null
@@ -47,23 +46,22 @@ namespace Platformer.Mechanics
                     || c.GetComponent<VictoryZone>() != null
                     || c.GetComponent<AttackHitbox>() != null)
                 {
-                    excludedActor++;
+                    excluded++;
                     continue;
                 }
 
-                c.usedByEffector = true;
+                // PlatformEffector2D 잔존 영역 제거 (BT25 누적 영향 차단)
                 var effector = c.GetComponent<PlatformEffector2D>();
-                if (effector == null) effector = c.gameObject.AddComponent<PlatformEffector2D>();
-                effector.useOneWay = true;
-                effector.surfaceArc = 180f;
-                effector.rotationalOffset = 0f;
-                effector.useSideFriction = false;
-                effector.useSideBounce = false;
+                if (effector != null) Object.Destroy(effector);
+                c.usedByEffector = false;
+
+                // Layer 8 변환 → IgnoreLayerCollision로 기본 통과
+                c.gameObject.layer = 8;
                 applied++;
                 if (appliedNames.Count < 8) appliedNames.Add($"{c.gameObject.name}({c.GetType().Name})");
             }
-            Debug.Log($"[BT25-OneWay] applied={applied} trigger={excludedTrigger} tilemap={excludedTilemap} actor={excludedActor} total={allColliders.Length}");
-            Debug.Log($"[BT25-OneWay] appliedSamples=[{string.Join(", ", appliedNames)}]");
+            Debug.Log($"[BT27-JumpThrough] applied={applied} excluded={excluded} total={allColliders.Length}");
+            Debug.Log($"[BT27-JumpThrough] appliedSamples=[{string.Join(", ", appliedNames)}]");
         }
     }
 }
diff --git a/Assets/Scripts/Mechanics/PlatformDropThrough.cs b/Assets/Scripts/Mechanics/PlatformDropThrough.cs
new file mode 100644
index 0000000..34ae2e8
--- /dev/null
+++ b/Assets/Scripts/Mechanics/PlatformDropThrough.cs
@@ -0,0 +1,75 @@
+using UnityEngine;
+
+namespace Platformer.Mechanics
+{
+    /// <summary>
+    /// BT5-Dev #27 — PD 제안 Layer + Raycast 동적 충돌.
+    /// Layer 8(JumpThrough) 발판은 기본 통과(IgnoreLayerCollision). Player 하강 + 발 Raycast 시점만 IgnoreCollision(false)로 충돌 활성 → 착지.
+    /// 점프(상승) 시 IgnoreCollision(true) 복구 → 다시 통과.
+    /// PlayerController.Awake에서 자동 부착.
+    /// </summary>
+    [RequireComponent(typeof(Collider2D))]
+    public class PlatformDropThrough : MonoBehaviour
+    {
+        const int JUMP_THROUGH_LAYER = 8;
+
+        [Tooltip("발 raycast 거리. 0.05~0.15 권장.")]
+        public float footRayDistance = 0.1f;
+
+        Collider2D _self;
+        KinematicObject _ko;
+        Collider2D _activePlatform;
+        int _jumpThroughMask;
+
+        void Awake()
+        {
+            _self = GetComponent<Collider2D>();
+            _ko = GetComponent<KinematicObject>();
+            _jumpThroughMask = 1 << JUMP_THROUGH_LAYER;
+        }
+
+        void Update()
+        {
+            if (_self == null || _ko == null) return;
+
+            // Player 발 위치 (collider 하단 중심)
+            Vector2 footPos = new Vector2(_self.bounds.center.x, _self.bounds.min.y + 0.02f);
+
+            // Layer 8 발판 raycast (footRayDistance 영역만 검사)
+            RaycastHit2D hit = Physics2D.Raycast(footPos, Vector2.down, footRayDistance, _jumpThroughMask);
+
+            bool falling = _ko.velocity.y <= 0.01f;  // 하강 또는 정지
+            bool rising = _ko.velocity.y > 0.5f;     // 점프 상승
+
+            if (rising)
+            {
+                // 점프 → 활성 발판 통과 복구
+                if (_activePlatform != null)
+                {
+                    Physics2D.IgnoreCollision(_self, _activePlatform, true);
+                    _activePlatform = null;
+                }
+            }
+            else if (falling && hit.collider != null && hit.collider != _activePlatform)
+            {
+                // 하강 + 발판 raycast hit → 충돌 활성 (착지)
+                Physics2D.IgnoreCollision(_self, hit.collider, false);
+                _activePlatform = hit.collider;
+            }
+            else if (falling && hit.collider == null && _activePlatform != null)
+            {
+                // 발판 떠남 (낙하) → 활성 해제
+                Physics2D.IgnoreCollision(_self, _activePlatform, true);
+                _activePlatform = null;
+            }
+        }
+
+        void OnDrawGizmosSelected()
+        {
+            if (_self == null) return;
+            Vector2 footPos = new Vector2(_self.bounds.center.x, _self.bounds.min.y + 0.02f);
+            Gizmos.color = Color.cyan;
+            Gizmos.DrawLine(footPos, footPos + Vector2.down * footRayDistance);
+        }
+    }
+}
diff --git a/Assets/Scripts/Mechanics/PlayerController.cs b/Assets/Scripts/Mechanics/PlayerController.cs
index a8a60c1..73b1591 100644
--- a/Assets/Scripts/Mechanics/PlayerController.cs
+++ b/Assets/Scripts/Mechanics/PlayerController.cs
@@ -82,6 +82,8 @@ namespace Platformer.Mechanics
             // PD 지시 2026-05-07 — 동반 컴포넌트 자동 부착 (Inspector 부착 불요)
             if (GetComponent<PlayerInvulnerabilityFlash>() == null) gameObject.AddComponent<PlayerInvulnerabilityFlash>();
             if (GetComponent<Platformer.UI.ResurrectPromptUI>() == null) gameObject.AddComponent<Platformer.UI.ResurrectPromptUI>();
+            // BT5-Dev #27 — Layer 8 발판 동적 충돌 (PD 제안 Raycast 방식)
+            if (GetComponent<PlatformDropThrough>() == null) gameObject.AddComponent<PlatformDropThrough>();
 
             // PD 지시 2026-05-07 — 사망 시 입력 차단 / 부활 시 입력 복원
             if (health != null)