diff --git a/backend/engine/cdsl_engine/build123d_adapter.py b/backend/engine/cdsl_engine/build123d_adapter.py
index 511f117d..fe8558fd 100644
--- a/backend/engine/cdsl_engine/build123d_adapter.py
+++ b/backend/engine/cdsl_engine/build123d_adapter.py
@@ -5,7 +5,7 @@ from __future__ import annotations
 import math
 from typing import Any, Iterable
 
-from build123d import Axis, Edge, Face, Plane, Solid, Vector, Wire, export_step
+from build123d import Axis, Compound, Edge, Face, Plane, ShapeList, Solid, Vector, Wire, export_step
 
 from .runtime_types import AxisSpec, HoleSpec, PlaneSpec, TopologyRecord, Vector3, canonical_plane_signature
 
@@ -151,6 +151,43 @@ class Build123dGeometryAdapter:
         # 沿给定方向向量拉伸一个面，生成实体。
         return Solid.extrude(face, _vector(direction))
 
+    @staticmethod
+    def extrude_trimmed(face: Face, target: Any, direction: Vector3) -> Any:
+        """Extrude the profile to the target face, trimming unreached regions.
+
+        Issue #5: when a profile intersects the up_to_surface target
+        non-uniformly (part of the profile reaches the face, part hangs
+        outside it), a plain vector extrusion is wrong.  The CAD semantics is
+        to keep only the material between the profile and the target.  We
+        pierce the profile through the target, push the target face backward
+        by the same margin to build a slab, and keep their boolean common
+        (intersection) as the trimmed solid.
+        """
+        # 1. 采样点到目标的最远命中距离决定穿透余量；没有任何采样点命中
+        #    说明 profile 与目标面无交叠，无法裁剪（保留 extent_target_not_reached）。
+        unit = _vector(direction).normalized()
+        hits = [
+            Build123dGeometryAdapter._forward_intersection_distance(target, point, unit)
+            for point in Build123dGeometryAdapter.profile_sample_points(face)
+        ]
+        distances = [value for value in hits if value is not None]
+        if not distances:
+            raise ValueError("extent target is not reached by the profile")
+        margin = max(distances) + 2.0
+        # 2. 穿透拉伸 profile，同时把目标面向回推生成体层，二者求交即裁剪体。
+        #    build123d 的布尔交方法名是 intersect（不是 OCC 的 common），
+        #    且多实体结果返回 ShapeList，需要规整为单个 Solid / Compound。
+        pierced = Solid.extrude(face, unit * margin)
+        slab = Solid.extrude(target, -unit * margin)
+        trimmed = pierced.intersect(slab)
+        if isinstance(trimmed, ShapeList):
+            members = list(trimmed)
+            # build123d 类型桩未声明 make_compound，但运行时存在（宽泛类型桩噪音）。
+            trimmed = members[0] if len(members) == 1 else Compound.make_compound(members)  # pyright: ignore[reportAttributeAccessIssue]
+        if trimmed is None or (hasattr(trimmed, "is_empty") and trimmed.is_empty()):
+            raise ValueError("extent target produced an empty trimmed solid")
+        return trimmed
+
     @staticmethod
     def body_center(body: Any) -> Vector3:
         # 取主体包围盒的中心坐标，作为体心的近似。
@@ -236,8 +273,9 @@ class Build123dGeometryAdapter:
         return Solid.revolve(face, angle_deg, Build123dGeometryAdapter.axis(axis))
 
     @staticmethod
-    def fuse(body: Any | None, solid: Solid) -> Any:
+    def fuse(body: Any | None, solid: Any) -> Any:
         # 布尔并：没有既有主体时，直接以该实体作为新主体。
+        # 实参类型放宽为 Any：build123d 的布尔结果可能是 Solid 或 Compound。
         return solid if body is None else body.fuse(solid)
 
     @staticmethod
diff --git a/backend/engine/cdsl_engine/runtime.py b/backend/engine/cdsl_engine/runtime.py
index 67ac1ed0..1f502218 100644
--- a/backend/engine/cdsl_engine/runtime.py
+++ b/backend/engine/cdsl_engine/runtime.py
@@ -44,6 +44,21 @@ class FeatureExecutionError(RuntimeError):
         self.detail = detail
 
 
+@dataclass(frozen=True)
+class ExtentVector:
+    """Single-directional extrusion displacement for one profile face.
+
+    ``trim_to`` stays ``None`` for an exact vector extrusion.  When set, the
+    extent means "extrude until the target face, trimming any profile region
+    that does not reach it" (up_to_surface trim semantics, issue #5).  The
+    piercing distance is computed inside the adapter, so ``vector`` only
+    supplies the direction.
+    """
+
+    vector: Vector3
+    trim_to: Any | None = None
+
+
 class AtomicExecutor(Protocol):
     atomic_id: str
 
@@ -62,6 +77,7 @@ class GeometryAdapter(Protocol):
     def body_geometry(self, body: Any) -> dict[str, Any]: ...
     def faces_for_sketch(self, sketch: dict[str, Any]) -> list[Any]: ...
     def extrude(self, face: Any, direction: Vector3) -> Any: ...
+    def extrude_trimmed(self, face: Any, target: Any, direction: Vector3) -> Any: ...
     def revolve(self, face: Any, angle_deg: float, axis: AxisSpec) -> Any: ...
     def fuse(self, body: Any | None, solid: Any) -> Any: ...
     def cut(self, body: Any, tool: Any) -> Any: ...
@@ -163,7 +179,7 @@ def _targeted_extent_vector(
     *,
     end_condition: dict[str, Any] | None = None,
     offset_mm: float | None = None,
-) -> Vector3:
+) -> ExtentVector:
     if session.body is None:
         raise FeatureExecutionError("missing_extent_body", "Selector-dependent extent requires an existing body", extent=condition)
     if condition == "through_next":
@@ -197,8 +213,20 @@ def _targeted_extent_vector(
         try:
             distance = session.adapter.uniform_intersection_distance(target, faces, direction)
         except ValueError as error:
-            code = "non_uniform_extent_target" if "non-uniform" in str(error) else "extent_target_not_reached"
-            raise FeatureExecutionError(code, str(error), extent=condition) from error
+            message = str(error)
+            code = "non_uniform_extent_target" if "non-uniform" in message else "extent_target_not_reached"
+            if condition == "up_to_surface":
+                # #5 高级终止条件：profile 与目标面非均匀相交（部分采样点未
+                # 命中目标 → 悬空；或各点命中距离不一 → 斜目标面）时不再整体
+                # 拒绝，而是"裁剪"——只保留从 profile 到目标面之间的材料。
+                # extrude_trimmed 内部做穿透拉伸 + 与目标面体层布尔求交，未达
+                # 目标的部分被切掉（CAD "拉伸到面"标准语义）。若全部采样点都
+                # 未命中（profile 与目标面无交叠），extrude_trimmed 内部仍抛
+                # "not reached"，保持显式拒绝。
+                # up_to_vertex/up_to_body/offset_from_surface 无 face 可构造
+                # 裁剪体层，仍保持显式拒绝。
+                return ExtentVector(vector_scale(direction, 1.0), trim_to=target)
+            raise FeatureExecutionError(code, message, extent=condition) from error
     if condition == "offset_from_surface":
         offset = abs(float(offset_mm if offset_mm is not None else node.params.get("distance_mm") or 0.0))
         distance -= offset
@@ -208,7 +236,7 @@ def _targeted_extent_vector(
                 "Offset distance reaches or passes the target surface",
                 extent=condition, offset_mm=offset,
             )
-    return vector_scale(direction, distance)
+    return ExtentVector(vector_scale(direction, distance))
 
 
 def _side_extent_vectors(
@@ -219,7 +247,7 @@ def _side_extent_vectors(
     *,
     end_condition: dict[str, Any],
     distance_mm: float,
-) -> list[Vector3]:
+) -> list[ExtentVector]:
     """Resolve one directional extent without borrowing the opposite side.
 
     ``extrude_add_two_sided`` calls this once for each independently captured
@@ -231,17 +259,22 @@ def _side_extent_vectors(
     if condition == "blind":
         if distance <= 0:
             raise ValueError("blind extent requires distance_mm > 0")
-        return [vector_scale(direction, distance)]
+        return [ExtentVector(vector_scale(direction, distance))]
     if condition == "mid_plane":
         if distance <= 0:
             raise ValueError("mid_plane extent requires distance_mm > 0")
-        return [vector_scale(direction, distance / 2), vector_scale(direction, -distance / 2)]
+        return [
+            ExtentVector(vector_scale(direction, distance / 2)),
+            ExtentVector(vector_scale(direction, -distance / 2)),
+        ]
     if condition == "through_all":
         if session.body is None:
             if distance <= 0:
                 raise ValueError("through_all on an initial feature has no body and no fallback distance")
-            return [direction * distance]
-        return [vector_scale(direction, max(session.adapter.body_span(session.body, direction), 1.0) + 2.0)]
+            # 注意：Vector3 是 tuple，不能直接做 direction * distance（那是元组
+            # 重复），这里必须用 vector_scale 做数乘（顺带修复的隐藏 bug）。
+            return [ExtentVector(vector_scale(direction, distance))]
+        return [ExtentVector(vector_scale(direction, max(session.adapter.body_span(session.body, direction), 1.0) + 2.0))]
     if condition in {"up_to_surface", "up_to_vertex", "offset_from_surface", "through_next", "up_to_body"}:
         return [
             _targeted_extent_vector(
@@ -257,7 +290,7 @@ def _extent_vectors(
     faces: list[Any],
     sketch: dict[str, Any],
     session: ExecutionSession,
-) -> list[Vector3]:
+) -> list[ExtentVector]:
     params = node.params
     normal = vector_unit(_normal_from_sketch(sketch), field_name="sketch normal")
     if bool(params.get("reverse")):
@@ -285,16 +318,19 @@ def _extent_vectors(
             # against.  The source must provide a usable blind component.
             if distance <= 0:
                 raise ValueError("through_all on an initial feature has no body and no fallback distance")
-            return [vector_scale(normal, distance)]
+            return [ExtentVector(vector_scale(normal, distance))]
         span = max(session.adapter.body_span(session.body, normal), 1.0) + 2.0
         if condition == "through_all":
-            return [vector_scale(normal, span)]
+            return [ExtentVector(vector_scale(normal, span))]
         if condition == "through_all_both":
-            return [vector_scale(normal, span), vector_scale(normal, -span)]
+            return [ExtentVector(vector_scale(normal, span)), ExtentVector(vector_scale(normal, -span))]
         # Through-all-and-blind is represented by a through direction plus
         # its captured opposite blind direction when available.
         reverse_distance = abs(float(params.get("reverse_distance_mm") or 0.0))
-        return [vector_scale(normal, span), vector_scale(normal, -(reverse_distance or span))]
+        return [
+            ExtentVector(vector_scale(normal, span)),
+            ExtentVector(vector_scale(normal, -(reverse_distance or span))),
+        ]
     return _side_extent_vectors(
         node, faces, normal, session, end_condition=end_condition, distance_mm=distance,
     )
@@ -337,9 +373,17 @@ def _shape_from_primary(node: FeaturePlanNode, session: ExecutionSession, *, ske
     # 3. 按特征类型生成子实体：
     if node.atomic_id.startswith("extrude_"):
         #   拉伸：先按终止条件（盲孔/贯穿/至面/双侧等）求出位移向量，
-        #   再对每个面沿每个向量做拉伸，得到实体列表。
-        vectors = _extent_vectors(node, faces, selected_sketch, session)
-        solids = [session.adapter.extrude(face, vector) for face in faces for vector in vectors]
+        #   再对每个面沿每个向量做拉伸，得到实体列表。up_to_surface 在
+        #   profile 与目标面非均匀相交时（extent.trim_to 非空）改用裁剪
+        #   拉伸：穿透后与目标面求交，只保留可达部分（issue #5）。
+        extents = _extent_vectors(node, faces, selected_sketch, session)
+        solids: list[Any] = []
+        for face in faces:
+            for extent in extents:
+                if extent.trim_to is None:
+                    solids.append(session.adapter.extrude(face, extent.vector))
+                else:
+                    solids.append(session.adapter.extrude_trimmed(face, extent.trim_to, extent.vector))
     else:
         #   旋转：解析旋转轴并校验旋转角，然后绕轴旋转每个面得到实体列表。
         axis = _revolve_axis(node, session)
diff --git a/backend/tests/test_engine_extent_trim_contract.py b/backend/tests/test_engine_extent_trim_contract.py
new file mode 100644
index 00000000..7677598c
--- /dev/null
+++ b/backend/tests/test_engine_extent_trim_contract.py
@@ -0,0 +1,209 @@
+"""#5 高级终止条件：up_to_surface 非均匀 profile 必须裁剪而非拒绝。
+
+中文说明
+--------
+这个文件在测试什么（issue #5「高级终止条件要求整张 profile 同一距离」的回归测试）：
+
+    1. 背景：up_to_surface（拉伸到面）等终止条件用"profile 采样点射线求交"
+       判定终止距离。修复前，只要 profile 与目标面**非均匀相交**——一部分
+       采样点到达目标、一部分悬空（profile 超出目标面范围），或目标面相对
+       profile 倾斜——runtime 就抛 non_uniform_extent_target 拒绝整个特征，
+       零件无法重建。而 CAD 的标准语义是**裁剪**：保留"从 profile 到目标面"
+       的可达材料，切掉悬空部分。
+       修复后：adapter 新增 extrude_trimmed（穿透拉伸 + 目标面体层布尔求交），
+       runtime 的 _targeted_extent_vector 在 up_to_surface 非均匀时返回
+       带 trim_to 的 ExtentVector，_shape_from_primary 改用裁剪拉伸。
+       up_to_vertex / up_to_body / offset_from_surface 没有可构造裁剪体层
+       的 face，仍保持显式拒绝（语义上无法裁剪）。
+
+    2. 本测试套件把"非均匀 up_to_surface 裁剪"合同固定下来：
+         - 单元几何契约（adapter）：斜目标面 + 水平 profile 裁剪出楔形，
+           体积 = ∫斜顶 dxdy；
+         - 集成裁剪契约（rebuild）：profile 悬空超出目标面时不再拒绝，
+           悬空部分被切掉，只保留与目标面之间的材料；
+         - 集成回归护栏（rebuild）：profile 完全落在目标面内仍走精确
+           均匀拉伸路径，体积不变（防止裁剪回退把均匀路径也改坏）。
+
+    3. sys.path 说明：把 backend/engine 加入搜索路径，直接 import cdsl_engine
+       包做端到端测试（与既有测试风格一致）。
+
+函数功能一览
+------------
+    _workplane(origin, normal)       构造指定原点与法向的草图工作平面。
+    _rectangle(minimum, maximum)     构造 XY 平面内的矩形轮廓（2D 多边形）。
+    _base_block()                    构造 10×10×10 拉伸主体（体积 1000，
+                                     顶面 z=10、范围 x/y ∈ [-5, 5]）。
+    _top_face_selector(baseline)     从 baseline 拓扑记录里挑出顶面（法向 +z）
+                                     的几何快照，作为 up_to_surface 的 reference。
+    ExtentTrimContractTests          见各测试方法 docstring。
+"""
+
+from __future__ import annotations
+
+import math
+import sys
+import tempfile
+import unittest
+from copy import deepcopy
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[2]
+sys.path.insert(0, str(ROOT / "backend"))
+sys.path.insert(0, str(ROOT / "backend" / "engine"))
+
+from cdsl_engine.build123d_adapter import Build123dGeometryAdapter  # noqa: E402
+from cdsl_engine.runtime import rebuild_cdsl  # noqa: E402
+
+
+try:
+    from build123d import Face, Plane, Vector  # noqa: F401
+    _HAS_BUILD123D = True
+except ImportError:
+    _HAS_BUILD123D = False
+
+
+# ---------------------------------------------------------------------------
+# 测试夹具
+# ---------------------------------------------------------------------------
+
+
+def _workplane(*, origin: list[float], normal: list[float]) -> dict:
+    """构造草图工作平面：显式指定原点与法向（x_dir 固定 +X）。"""
+    return {"origin_mm": origin, "x_dir": [1, 0, 0], "normal": normal}
+
+
+def _rectangle(minimum: list[float], maximum: list[float]) -> dict:
+    """XY 平面内的矩形轮廓（2D 多边形），顶点逆时针。"""
+    return {"type": "polygon", "vertices": [
+        [minimum[0], minimum[1]], [maximum[0], minimum[1]],
+        [maximum[0], maximum[1]], [minimum[0], maximum[1]],
+    ]}
+
+
+def _base_block() -> dict:
+    """10×10×10 拉伸主体：体积 1000，顶面位于 z=10、范围 x/y ∈ [-5, 5]。"""
+    return {
+        "schema": "cad.cdsl.llm.v1", "schema_version": "1.1.0", "kind": "part",
+        "part_id": "extent-trim-contract", "meta": {"unit": "mm"},
+        "geometry": {"sketches": [{
+            "id": "base", "workplane": _workplane(origin=[0, 0, 0], normal=[0, 0, 1]),
+            "profile": _rectangle([-5, -5], [5, 5]),
+        }]},
+        "features": [{
+            "id": "base_add", "atomic_id": "extrude_add_blind", "depends_on": [],
+            "params": {"distance_mm": 10}, "sketch_id": "base",
+        }],
+    }
+
+
+def _top_face_selector(baseline: dict) -> dict:
+    """从 baseline 拓扑记录里取顶面（法向 +z 的平面 face）的几何快照。
+
+    这个快照被 TopologyRegistry 用来做几何等价匹配，从而把 up_to_surface
+    的 reference 解析到重建主体上的真实 Face。
+    """
+    return next(
+        item for item in baseline["topology_records"]
+        if item["kind"] == "face"
+        and item["geometry"]["surface_type"] == "plane"
+        and item["geometry"]["normal"][2] > 0.9
+    )
+
+
+# ---------------------------------------------------------------------------
+# 测试套件
+# ---------------------------------------------------------------------------
+
+
+class ExtentTrimContractTests(unittest.TestCase):
+    """up_to_surface 非均匀相交「裁剪几何-行为-回归」三方合同测试。"""
+
+    @unittest.skipUnless(_HAS_BUILD123D, "build123d is not available")
+    def test_extrude_trimmed_slanted_target_produces_wedge(self) -> None:
+        """单元几何契约：斜目标面 + 水平 profile 裁剪出楔形。
+
+        profile 是 z=0 的 10×10 矩形；目标面是斜面 z = 0.2x + 5
+        （z_dir=(0.2, 0, 0.98) 的平面）。采样点沿 +z 到斜面的距离从
+        4（x=-5）到 6（x=+5）变化 → uniform_intersection_distance 必然
+        判定非均匀。裁剪结果应是顶面贴斜面的楔形，体积 =
+        ∫∫ (0.2x + 5) dxdy = 5 × 100 = 500。修复前该场景直接抛
+        non_uniform_extent_target（无实体可断言），本测试锁死裁剪几何。
+        """
+        profile = Face.make_rect(10, 10)  # 中心在原点，x/y ∈ [-5, 5]，z=0
+        slanted = Face.make_rect(20, 20, Plane(origin=(0, 0, 5), z_dir=(0.2, 0, 0.98)))
+
+        trimmed = Build123dGeometryAdapter.extrude_trimmed(profile, slanted, (0, 0, 1))
+
+        self.assertAlmostEqual(trimmed.volume, 500.0, places=5)
+
+    @unittest.skipUnless(_HAS_BUILD123D, "build123d is not available")
+    def test_up_to_surface_hanging_profile_is_trimmed_not_rejected(self) -> None:
+        """集成裁剪契约：profile 悬空超出目标面时不再拒绝，悬空部分被切掉。
+
+        baseline 是 10×10×10 主体（顶面 z=10、范围 [-5, 5]²）。第二个 add
+        特征在 z=12 平面、法向 -z，profile 为 16×16 矩形（x/y ∈ [-8, 8]，
+        大部分悬空在顶面范围之外）。up_to_surface 目标 = 顶面：
+          - 中心采样点沿 -z 命中顶面（距离 2）；
+          - 角落采样点（x/y = ±8）在顶面范围外，射线不命中 → 非均匀。
+        修复前抛 non_uniform_extent_target；修复后裁剪出
+        x/y ∈ [-5, 5]、z ∈ [10, 12] 的 10×10×2 体块，总体积 = 1000 + 200。
+        """
+        base = _base_block()
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            baseline = rebuild_cdsl(base, root / "baseline.step")
+            top_face = _top_face_selector(baseline)
+
+            with_cap = deepcopy(base)
+            with_cap["geometry"]["sketches"].append({
+                "id": "cap", "workplane": _workplane(origin=[0, 0, 12], normal=[0, 0, -1]),
+                "profile": _rectangle([-8, -8], [8, 8]),
+            })
+            with_cap["features"].append({
+                "id": "cap_add", "atomic_id": "extrude_add_blind", "depends_on": ["base_add"],
+                "sketch_id": "cap",
+                "params": {
+                    "distance_mm": 0,
+                    "end_condition": {"type": "up_to_surface", "reference": top_face},
+                },
+            })
+            rebuilt = rebuild_cdsl(with_cap, root / "trimmed.step")
+
+        self.assertAlmostEqual(rebuilt["volume_mm3"], 1000 + 200, places=5)
+
+    @unittest.skipUnless(_HAS_BUILD123D, "build123d is not available")
+    def test_up_to_surface_uniform_profile_keeps_exact_distance(self) -> None:
+        """集成回归护栏：profile 完全落在目标面内仍走精确均匀拉伸。
+
+        与上一个测试同构，但 profile 缩到 6×6（x/y ∈ [-3, 3]），完全落在
+        顶面 [-5, 5]² 范围内 → 所有采样点沿 -z 都命中且距离一致（2）→
+        保持原精确拉伸路径（不触发裁剪），体积 = 1000 + 36×2 = 1072。
+        防止裁剪回退把均匀路径也改坏。
+        """
+        base = _base_block()
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            baseline = rebuild_cdsl(base, root / "baseline.step")
+            top_face = _top_face_selector(baseline)
+
+            with_cap = deepcopy(base)
+            with_cap["geometry"]["sketches"].append({
+                "id": "cap", "workplane": _workplane(origin=[0, 0, 12], normal=[0, 0, -1]),
+                "profile": _rectangle([-3, -3], [3, 3]),
+            })
+            with_cap["features"].append({
+                "id": "cap_add", "atomic_id": "extrude_add_blind", "depends_on": ["base_add"],
+                "sketch_id": "cap",
+                "params": {
+                    "distance_mm": 0,
+                    "end_condition": {"type": "up_to_surface", "reference": top_face},
+                },
+            })
+            rebuilt = rebuild_cdsl(with_cap, root / "exact.step")
+
+        self.assertAlmostEqual(rebuilt["volume_mm3"], 1000 + 36 * 2, places=5)
+
+
+if __name__ == "__main__":
+    unittest.main()