diff --git a/backend/agent/skills/cad-authoring/SKILL.md b/backend/agent/skills/cad-authoring/SKILL.md
index b777186d..27d2a480 100644
--- a/backend/agent/skills/cad-authoring/SKILL.md
+++ b/backend/agent/skills/cad-authoring/SKILL.md
@@ -127,6 +127,62 @@ For `max_z`/`min_z` placement intent, use an owner role such as
 Use only supplied operations and their exact parameter schemas. Do not invent
 parameters, implicit booleans, or substitutes after a capability error.
 
+## Semantic Annotation (meta and intent)
+
+Every document carries semantic annotations for downstream training. They are
+purely descriptive: the compiler carries them through verbatim, geometry never
+depends on them, and they are never acceptance targets.
+
+Document level — include `meta` with at least one of:
+
+```json
+{
+  "meta": {
+    "description": "R8 rounded square bushing, 100×100×12, central Ø45 bore",
+    "function": "Spacer sleeve over a Ø45 shaft; rounded corners for handling"
+  }
+}
+```
+
+- `description`: one sentence naming the part with its key specifications
+  (≤60 characters). `function`: what the part does and where it fits
+  (≤200 characters). Narratives are written in the request language; keys and
+  controlled labels are English `snake_case`.
+
+Feature level — attach `intent` to every feature:
+
+```json
+{
+  "intent": {
+    "label": "shaft_passage",
+    "summary": "Ø45 central through bore, concentric with the outer contour",
+    "why": "The fitting face of the sleeve; diameter follows the mating shaft",
+    "provenance": "authored"
+  }
+}
+```
+
+- `label`: one controlled vocabulary term in `snake_case` — for example
+  `housing_blank`, `shaft_passage`, `fastener_hole`, `bolt_circle`,
+  `tap_hole`, `counterbore_seat`, `countersink_seat`, `locating_pin_hole`,
+  `bearing_seat`, `press_fit_boss`, `mounting_boss`, `mounting_foot`,
+  `lifting_eye`, `slot_adjustment`, `coolant_channel`, `lubrication_gallery`,
+  `vent_hole`, `drain_port`, `fluid_inlet`, `process_corner_relief`,
+  `weld_prep`, `machining_setup_tab`, `inspection_access`,
+  `stress_relief_fillet`, `stiffening_rib`, `weight_relief`,
+  `mass_saving_pocket`, `load_path_flange`, `wall_thickness_transition`,
+  `gear_teeth`, `rack_teeth`, `thread_drive`, `cam_track`, `bend_wing`,
+  `cosmetic_surface`, `datum_plane_feature`, `datum_axis_feature`. The list
+  is open: an accurate new `snake_case` term is valid, but prefer vocabulary.
+- `summary` (required, ≤80 characters): what it is plus the key parameters.
+  Use parameterized wording (`M8`, `Ø75`, `R8`), never a restatement of the
+  request prose.
+- `why` (optional, ≤400 characters): the functional reason this feature exists.
+- `provenance`: always `"authored"` when the model writes it.
+- Do not invent fields inside `intent`, and never treat a mismatch between an
+  annotation and geometry as acceptable — the label must match the feature
+  actually constructed.
+
 ## Sketches And Coordinates
 
 Keep a sketch to exactly `workplane` and `profile`. The workplane declares its
@@ -228,6 +284,9 @@ Before returning the document, check every feature against these invariants:
 5. Every requested removal intersects its intended material, every repeated
    feature has a valid seed reference, and every connected addition uses an
    operation whose contract explicitly supports the chosen result mode.
+6. Every feature carries an `intent` with a truthful `label`, a parameterized
+   `summary` of at most 80 characters, and `provenance: "authored"`; the
+   document carries `meta` with at least one of `description`/`function`.
 
 If any invariant is false, revise the construction before emitting the single
 complete `cad.author.v1` document.
diff --git a/backend/app/cad_agent/application/authoring_compiler.py b/backend/app/cad_agent/application/authoring_compiler.py
index 6b2c36a5..c78c15df 100644
--- a/backend/app/cad_agent/application/authoring_compiler.py
+++ b/backend/app/cad_agent/application/authoring_compiler.py
@@ -106,10 +106,17 @@ class AuthoringCompiler:
                 sketch_id = f"sketch_{source_positions[feature.name]:03d}"
                 sketches.append({"id": sketch_id, **self._runtime_sketch(feature.sketch.model_dump(mode="json"))})
                 output["sketch_id"] = sketch_id
+            if feature.intent is not None:
+                # Semantic annotation only: carried through for training data,
+                # never consumed by runtime geometry or validation semantics.
+                output["intent"] = feature.intent.model_dump(mode="json", exclude_none=True)
             features.append(output)
+        document_meta: dict[str, Any] = {"unit": "mm"}
+        if doc.meta is not None:
+            document_meta.update(doc.meta.model_dump(mode="json", exclude_none=True))
         runtime = {
             "schema": "cad.runtime.v1", "schema_version": "1.0.0", "kind": "part",
-            "part_id": "compiled", "meta": {"unit": "mm"},
+            "part_id": "compiled", "meta": document_meta,
             "bodies": [
                 {"id": body_ids[body.name], "name": body.name}
                 for body in doc.bodies
diff --git a/backend/app/cad_agent/application/authoring_contract.py b/backend/app/cad_agent/application/authoring_contract.py
index 677736ef..67d109be 100644
--- a/backend/app/cad_agent/application/authoring_contract.py
+++ b/backend/app/cad_agent/application/authoring_contract.py
@@ -108,6 +108,33 @@ class SelectorIntent(AuthorModel):
         return value
 
 
+class FeatureIntent(AuthorModel):
+    """Feature-level semantic annotation for training data.
+
+    Mirrors ``$defs/featureIntent`` in ``cdsl_schema.json``: purely
+    descriptive, never read by the compiler for geometry decisions.
+    """
+
+    label: str | None = Field(default=None, pattern=r"^[a-z][a-z0-9_]{2,63}$")
+    summary: str = Field(min_length=1, max_length=80)
+    why: str | None = Field(default=None, min_length=1, max_length=400)
+    ties_to_requirement: str | None = Field(default=None, pattern=r"^[A-Za-z0-9_.:-]{1,80}$")
+    provenance: Literal["authored", "annotated", "imported"]
+
+
+class DocumentMeta(AuthorModel):
+    """Document-level semantic annotation (part description and function)."""
+
+    description: str | None = Field(default=None, min_length=1, max_length=60)
+    function: str | None = Field(default=None, min_length=1, max_length=200)
+
+    @model_validator(mode="after")
+    def require_at_least_one(self) -> "DocumentMeta":
+        if self.description is None and self.function is None:
+            raise ValueError("meta requires at least one of description or function")
+        return self
+
+
 class AuthorFeature(AuthorModel):
     name: str = Field(pattern=_NAME)
     operation: str = Field(pattern=r"^[a-z][a-z0-9_]{0,80}$")
@@ -121,6 +148,10 @@ class AuthorFeature(AuthorModel):
         default=None,
         description="For sketch operations: exactly {workplane, profile}. Circle profiles use diameter_mm and center_mm.",
     )
+    intent: FeatureIntent | None = Field(
+        default=None,
+        description="Optional semantic annotation for training; never consumed by geometry.",
+    )
 
 
 class AuthorBody(AuthorModel):
@@ -133,6 +164,10 @@ class AuthoringDocument(AuthorModel):
     units: str = Field(default="mm", pattern=r"^mm$")
     coordinate_system: str = Field(default="right_handed", pattern=r"^[a-z][a-z0-9_-]{0,40}$")
     assumptions: list[str] = Field(default_factory=list, max_length=64)
+    meta: DocumentMeta | None = Field(
+        default=None,
+        description="Optional document-level semantic annotation (description/function).",
+    )
     bodies: list[AuthorBody] = Field(min_length=1, max_length=32)
     acceptance_targets: list[dict[str, Any]] = Field(default_factory=list, max_length=128)
 
diff --git a/backend/engine/cdsl_engine/cdsl_schema.json b/backend/engine/cdsl_engine/cdsl_schema.json
index 9c6d01c7..6f2cb533 100644
--- a/backend/engine/cdsl_engine/cdsl_schema.json
+++ b/backend/engine/cdsl_engine/cdsl_schema.json
@@ -24,6 +24,18 @@
   "required": ["schema", "geometry", "features"],
   "additionalProperties": false,
   "$defs": {
+    "featureIntent": {
+      "type": "object",
+      "properties": {
+        "label": {"type": "string", "pattern": "^[a-z][a-z0-9_]{2,63}$"},
+        "summary": {"type": "string", "minLength": 1, "maxLength": 80},
+        "why": {"type": "string", "minLength": 1, "maxLength": 400},
+        "ties_to_requirement": {"type": "string", "pattern": "^[A-Za-z0-9_.:-]{1,80}$"},
+        "provenance": {"enum": ["authored", "annotated", "imported"]}
+      },
+      "required": ["summary", "provenance"],
+      "additionalProperties": false
+    },
     "number": {"type": "number"},
     "positive": {"type": "number", "exclusiveMinimum": 0},
     "positiveInteger": {"type": "integer", "minimum": 1},
@@ -1192,7 +1204,8 @@
         "params": {"type": "object"},
         "execution_status": {"enum": ["supported", "deferred"]},
         "selectors": {"type": "array", "items": {"$ref": "#/$defs/selectorRef"}},
-        "unresolved": {"type": "array", "items": {"type": "string", "minLength": 1}}
+        "unresolved": {"type": "array", "items": {"type": "string", "minLength": 1}},
+        "intent": {"$ref": "#/$defs/featureIntent"}
       },
       "required": ["id", "atomic_id", "depends_on", "params"],
       "additionalProperties": false,
diff --git a/backend/engine/cdsl_engine/semantic_vocabulary.json b/backend/engine/cdsl_engine/semantic_vocabulary.json
new file mode 100644
index 00000000..f208fc9b
--- /dev/null
+++ b/backend/engine/cdsl_engine/semantic_vocabulary.json
@@ -0,0 +1,443 @@
+{
+  "_meta": {
+    "title": "CDSL 语义词表几何签名（初稿 v0.1）",
+    "protocol": "cad.cdsl.llm.v1",
+    "date": "2026-09-14",
+    "role": "三层关联机制的字典层：label ↔ 几何期望的机器可读绑定。签名是期望（expectation），不是模板（template）。",
+    "checking_semantics": "签名检查只产生警告与训练数据分级，永不阻塞建模与重建（与 AGENTS.md 一致：不把语义分歧当程序错误）。",
+    "input_dependency": "metric_expectations 依赖重建管线输出的逐特征指标（derived_metrics per_feature delta）。缺失 delta 时，退化检查为：metric_expectations 中 *_delta 键跳过，其余照查。",
+    "inheritance": "label 可带 parent，检查时先应用父签名再应用自身（并集）。composite=true 表示该语义典型地由特征组合实现（如打孔+阵列），检查时沿 depends_on 链聚合 delta。",
+    "out_of_vocabulary": "词表外 label 无签名，程序侧零校验（开放词表的设计使然）；训练侧应引导收敛到词表内。",
+    "known_limitation": "纯用途差异在几何上不可分：coolant_channel 与 lubrication_gallery、cosmetic_surface 与 stress_relief_fillet 的几何签名几乎相同，其区分依赖 intent.why 与上下文，不依赖本签名。",
+    "cross_field_reference": "param_expectations 的值可以引用另一参数路径（如 {\">\": \"diameter_mm\"}），匹配器解析为跨字段比较。",
+    "signature_version": "0.1",
+    "vocabulary_count": 37
+  },
+  "signatures": {
+    "bolt_circle": {
+      "parent": "fastener_hole",
+      "composite": true,
+      "allowed_atomics": ["pattern_circular", "pattern_linear", "hole_wizard", "hole_blind"],
+      "param_expectations": {
+        "pattern_count": {">=": 3},
+        "positions": {">=": 3}
+      },
+      "metric_expectations": {
+        "hole_count_delta": {">=": 3},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "relations": ["instances_same_diameter", "instances_on_common_circle"],
+      "notes_zh": "一组等径紧固孔沿公共圆周分布。典型实现：hole_wizard(1孔)+pattern_circular 阵列，或一次多 positions。检查时沿 depends_on 聚合打孔与阵列两特征的 delta。"
+    },
+    "fastener_hole": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through"],
+      "param_expectations": {
+        "end_condition.type": {"in": ["through_all", "through_all_both", "blind"]}
+      },
+      "metric_expectations": {
+        "hole_count_delta": {">=": 1},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "紧固件过孔（光孔）。词表父节点：tap_hole / bolt_circle / 沉头类均为其子型或伴生型。"
+    },
+    "tap_hole": {
+      "parent": "fastener_hole",
+      "allowed_atomics": ["hole_wizard", "thread_cut"],
+      "param_expectations": {
+        "thread": {"required_if_atomic": "hole_wizard"}
+      },
+      "metric_expectations": {
+        "hole_count_delta": {">=": 1},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true,
+        "creates_thread_helix": false
+      },
+      "notes_zh": "螺纹孔。注意：hole_wizard 的 thread 装饰当前被引擎降级为光孔（thread_decoration_ignored 诊断），creates_thread_helix 恒为 false，签名如实反映现状；thread_cut 才产生真实螺旋几何。"
+    },
+    "counterbore_seat": {
+      "parent": "fastener_hole",
+      "allowed_atomics": ["hole_counterbore", "hole_wizard"],
+      "param_expectations": {
+        "counterbore_diameter_mm": {">": "diameter_mm"},
+        "counterbore_depth_mm": {">": 0}
+      },
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true,
+        "creates_planar_shoulder": true
+      },
+      "notes_zh": "沉头柱坑：主孔 + 同轴大直径浅坑，坑底形成环形平面肩。"
+    },
+    "countersink_seat": {
+      "parent": "fastener_hole",
+      "allowed_atomics": ["hole_countersink", "hole_wizard"],
+      "param_expectations": {
+        "countersink_diameter_mm": {">": "diameter_mm"},
+        "countersink_angle_rad": {">": 0, "<": 3.141592653589793}
+      },
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cone_face": true
+      },
+      "notes_zh": "沉头锥坑：主孔 + 锥形扩口，锥面是与柱面区分的强拓扑指纹。"
+    },
+    "locating_pin_hole": {
+      "allowed_atomics": ["hole_wizard", "hole_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "hole_count_delta": {">=": 1},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "定位销孔。配合公差与双孔位置度是设计要点，但公差不在 CDSL 当前表达能力内，机器只能查到 存在性/数量；配合语义写 why。"
+    },
+    "bearing_seat": {
+      "allowed_atomics": ["extrude_add_blind", "cylinder_add", "revolve_add", "hole_wizard"],
+      "param_expectations": {},
+      "metric_expectations": {},
+      "topology_expectations": {
+        "creates_cylindrical_fit_surface": true
+      },
+      "notes_zh": "轴承位（轴颈或座孔）。功能型语义，几何签名天然宽：内核是圆柱配合面（外圆或内孔），方向（增/减材）与安装形式有关。尺寸配合关系写 why。"
+    },
+    "shaft_passage": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through"],
+      "param_expectations": {
+        "end_condition.type": {"in": ["through_all", "through_all_both"]}
+      },
+      "metric_expectations": {
+        "hole_count_delta": {">=": 1},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "relations": ["axis_aligned_with_body_center_or_axis"],
+      "notes_zh": "过轴通孔。贯穿是强约束（签名可查）；同心是典型但非必然（签名标注为关系提示）。"
+    },
+    "press_fit_boss": {
+      "allowed_atomics": ["extrude_add_blind", "cylinder_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_outer_cylindrical_face": true
+      },
+      "notes_zh": "压配合凸台：增材圆柱特征。过盈量等配合信息写在 why，几何只可查 增材+圆柱面。"
+    },
+    "alignment_datum": {
+      "allowed_atomics": ["reference_plane", "reference_axis", "extrude_add_blind", "hole_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">=": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "对中/对位基准结构。可以是参考几何（零材料变化）也可以是小凸台/销孔；签名宽，依赖 why。"
+    },
+    "mounting_boss": {
+      "allowed_atomics": ["extrude_add_blind", "cylinder_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_outer_cylindrical_face": true
+      },
+      "notes_zh": "安装凸台：增材圆柱特征，常带后续紧固孔（组合语义）。"
+    },
+    "mounting_foot": {
+      "allowed_atomics": ["extrude_add_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_planar_faces": true
+      },
+      "notes_zh": "安装底脚：增材板状特征，形成安装平面。"
+    },
+    "lifting_eye": {
+      "allowed_atomics": ["extrude_add_blind", "revolve_add", "sweep_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "吊环/吊耳：增材结构带贯穿吊孔（吊索穿过）。孔的存在是较强指纹。"
+    },
+    "slot_adjustment": {
+      "allowed_atomics": ["extrude_cut_blind", "extrude_cut_through", "hole_wizard", "hole_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_planar_walls": true
+      },
+      "notes_zh": "调整长孔/滑槽：允许位置调节的细长切口。典型实现：长圆 polygon 切除，或两孔+直切。"
+    },
+    "coolant_channel": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through", "sweep_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "冷却通道。与 lubrication_gallery 几何签名几乎相同（能力边界案例），区分靠 why 与介质上下文。"
+    },
+    "lubrication_gallery": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through", "sweep_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "润滑油路。同上，几何上与冷却通道不可分。"
+    },
+    "vent_hole": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "hole_count_delta": {">=": 1},
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "排气孔：小直径贯穿孔，通常贯穿（呼吸/排气的功能要求）。"
+    },
+    "drain_port": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "排液口。位置在最低点是设计要点但不在几何签名能力内，写 why。"
+    },
+    "fluid_inlet": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through", "extrude_add_blind"],
+      "param_expectations": {},
+      "metric_expectations": {},
+      "topology_expectations": {},
+      "notes_zh": "进液口。可能是孔（减材）也可能是接管凸台+孔（增减组合），签名宽。"
+    },
+    "process_corner_relief": {
+      "allowed_atomics": ["extrude_cut_blind", "extrude_cut_through", "chamfer", "fillet"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "工艺让位（避让刀具/相邻件干涉）。材料切除量小是典型特征。"
+    },
+    "weld_prep": {
+      "allowed_atomics": ["chamfer"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_cone_face": true
+      },
+      "notes_zh": "焊接坡口：倒角原子直接映射（坡口即倒角），锥面是强指纹。"
+    },
+    "machining_setup_tab": {
+      "allowed_atomics": ["extrude_add_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "装夹工艺台：临时增材，后续工序去除。生命周期语义写在 why（几何本身与普通小凸台不可分）。"
+    },
+    "inspection_access": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_through"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_inner_cylindrical_face": true
+      },
+      "notes_zh": "测量/探针可达孔。"
+    },
+    "stress_relief_fillet": {
+      "allowed_atomics": ["fillet"],
+      "param_expectations": {
+        "radius_mm": {">": 0}
+      },
+      "metric_expectations": {
+        "volume_delta": {"<": 0},
+        "face_count_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_torus_face": true
+      },
+      "notes_zh": "应力缓解圆角。torus 面（圆角面）+面数增加是修饰操作生效的强指纹；与 cosmetic_surface 的区别是用途而非几何。"
+    },
+    "stiffening_rib": {
+      "allowed_atomics": ["extrude_add_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_planar_faces": true
+      },
+      "notes_zh": "加强筋：增材薄壁特征。薄（相对壁厚）是定义的一部分但属跨字段相对约束，初稿不做机器检查。"
+    },
+    "weight_relief": {
+      "allowed_atomics": ["hole_wizard", "hole_blind", "extrude_cut_blind", "extrude_cut_through"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "减重（孔/槽）。通常多孔或多腔（volume delta 显著为负）。"
+    },
+    "mass_saving_pocket": {
+      "allowed_atomics": ["extrude_cut_blind"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_planar_faces": true
+      },
+      "notes_zh": "减重腔：盲切腔体，不留穿。与 weight_relief 的区别是形式（腔 vs 孔阵）。"
+    },
+    "load_path_flange": {
+      "allowed_atomics": ["extrude_add_blind", "revolve_add"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "承载法兰/接盘。功能型语义，签名宽。"
+    },
+    "wall_thickness_transition": {
+      "allowed_atomics": ["shell", "extrude_add_blind"],
+      "param_expectations": {},
+      "metric_expectations": {},
+      "topology_expectations": {},
+      "notes_zh": "壁厚过渡。实现多样（抽壳/变截面拉伸），签名宽。"
+    },
+    "gear_teeth": {
+      "allowed_atomics": ["gear_add"],
+      "param_expectations": {
+        "module_mm": {">": 0},
+        "teeth_count": {">=": 8}
+      },
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_involute_or_bspline_faces": true
+      },
+      "notes_zh": "轮齿：gear_add 原子专属。渐开线/自由曲面齿面是强指纹（亦可用于检测 gear_add 是否真的生成几何）。"
+    },
+    "rack_teeth": {
+      "allowed_atomics": ["rack_add"],
+      "param_expectations": {
+        "module_mm": {">": 0}
+      },
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_involute_or_bspline_faces": true
+      },
+      "notes_zh": "齿条齿：rack_add 原子专属。"
+    },
+    "thread_drive": {
+      "allowed_atomics": ["thread_add"],
+      "param_expectations": {
+        "pitch_mm": {">": 0}
+      },
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_thread_helix": true
+      },
+      "notes_zh": "传动螺纹（外螺纹实体段）：thread_add 专属，螺旋面是强指纹。"
+    },
+    "cam_track": {
+      "allowed_atomics": ["sweep_add", "extrude_cut_through", "extrude_cut_blind"],
+      "param_expectations": {},
+      "metric_expectations": {},
+      "topology_expectations": {
+        "creates_bspline_curve_geometry": true
+      },
+      "notes_zh": "凸轮轨道：曲线扫掠或曲线槽，B 样条路径/曲线是其指纹。"
+    },
+    "bend_wing": {
+      "allowed_atomics": ["bend_add"],
+      "param_expectations": {
+        "chain": {">=": 1}
+      },
+      "metric_expectations": {
+        "volume_delta": {">": 0}
+      },
+      "topology_expectations": {
+        "creates_cylindrical_bend_face": true
+      },
+      "notes_zh": "折弯翼：bend_add 原子专属，折弯内/外圆柱面是指纹。"
+    },
+    "cosmetic_surface": {
+      "allowed_atomics": ["fillet", "chamfer"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"<": 0}
+      },
+      "topology_expectations": {
+        "creates_torus_face": true
+      },
+      "notes_zh": "外观修饰（倒圆/倒角）。与 stress_relief_fillet 几何签名几乎相同（能力边界案例），区别写 why。"
+    },
+    "datum_plane_feature": {
+      "allowed_atomics": ["reference_plane"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"==": 0},
+        "face_count_delta": {"==": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "设计基准面：零材料变化 + 零拓扑变化 + 特定原子，是全部签名中最确定的一条（强指纹）。"
+    },
+    "datum_axis_feature": {
+      "allowed_atomics": ["reference_axis"],
+      "param_expectations": {},
+      "metric_expectations": {
+        "volume_delta": {"==": 0},
+        "face_count_delta": {"==": 0}
+      },
+      "topology_expectations": {},
+      "notes_zh": "设计基准轴：同上，强指纹。"
+    }
+  }
+}