diff --git a/crates/ocs_doc_api/IMPLEMENTATION.md b/crates/ocs_doc_api/IMPLEMENTATION.md
index 6666c36a0..537f35d69 100644
--- a/crates/ocs_doc_api/IMPLEMENTATION.md
+++ b/crates/ocs_doc_api/IMPLEMENTATION.md
@@ -106,8 +106,12 @@ tested: 615 host lib + 8 crate unit + 3 spec↔wire consistency tests green.
 - **Done:** media/misc families report a **real `kind`** via `GetEntity`
   (`RasterImage`, `Table`, `Leader`, `MultiLeader`, `MLine`, `Mesh`, `Helix`,
   `Region`, `Body`, `Surface`, `Face3D`, `Dimension`, `Hatch`) instead of "Other";
-  `RasterImage` has coarse bounds (insertion + u·width + v·height); generic
-  `delete` works on all. Covered by `phase5_*` test.
+  generic `delete` works on all. Covered by `phase5_*` test.
+- **Done (read-mostly bounds):** `bounds()` now works for the vertex/point-carrying
+  families — `Leader`, `Mesh`, `Face3D` (4 corners), `MLine` (vertex positions),
+  `Helix` (start point) — via a points-to-AABB helper (`read_mostly_family_bounds_*`
+  test). `RasterImage` has 4-corner bounds. `Region`/`Body`/`Surface`/`MultiLeader`
+  stay `Unsupported` for bounds (complex/nested geometry).
 - **Done (typed create):** `create_raster_image(file_path, insertion, u, v, size)`
   → `Operation::CreateRasterImage` (host auto-registers the ImageDefinition), and
   `create_table(insertion_point, data[row][col])` → `Operation::CreateTable`
diff --git a/src/app/doc_api.rs b/src/app/doc_api.rs
index 160279bc7..9c58225d5 100644
--- a/src/app/doc_api.rs
+++ b/src/app/doc_api.rs
@@ -1301,6 +1301,54 @@ mod tests {
         }
     }
 
+    // ── Read-mostly family bounds (Leader/Mesh/Face3D/MLine/Helix) ──────────
+
+    #[test]
+    fn read_mostly_family_bounds_leader_and_mesh() {
+        let mut app = OpenCADStudio::new_for_test();
+        let mut host = HostSession::new(&mut app, 0);
+        // Leader with vertices at (0,0,0),(5,5,0),(10,0,0) -> bounds x[0,10] y[0,5].
+        let mut leader = acadrust::entities::Leader::default();
+        leader.vertices = vec![
+            acadrust::types::Vector3::new(0.0, 0.0, 0.0),
+            acadrust::types::Vector3::new(5.0, 5.0, 0.0),
+            acadrust::types::Vector3::new(10.0, 0.0, 0.0),
+        ];
+        let leader_h = host.document_mut().add_entity(EntityType::Leader(leader)).unwrap();
+        // Mesh with vertices in a unit cube at (2..3, 2..3, 0).
+        let mut mesh = acadrust::entities::Mesh::default();
+        mesh.vertices = vec![
+            acadrust::types::Vector3::new(2.0, 2.0, 0.0),
+            acadrust::types::Vector3::new(3.0, 2.0, 0.0),
+            acadrust::types::Vector3::new(3.0, 3.0, 0.0),
+            acadrust::types::Vector3::new(2.0, 3.0, 0.0),
+        ];
+        let mesh_h = host.document_mut().add_entity(EntityType::Mesh(mesh)).unwrap();
+
+        let receipt = dispatch(&mut host, DocApiEnvelope::queries(vec![
+            Query::GetBounds { id: handle_to_obj(leader_h) },
+            Query::GetBounds { id: handle_to_obj(mesh_h) },
+            Query::GetEntity { id: handle_to_obj(leader_h) },
+        ])).unwrap();
+        match &receipt.query_results[0] {
+            QueryResult::Bounds(b) => {
+                assert!((b.min[0] - 0.0).abs() < 1e-6 && (b.max[0] - 10.0).abs() < 1e-6, "{b:?}");
+                assert!((b.min[1] - 0.0).abs() < 1e-6 && (b.max[1] - 5.0).abs() < 1e-6, "{b:?}");
+            }
+            other => panic!("expected bounds, got {other:?}"),
+        }
+        match &receipt.query_results[1] {
+            QueryResult::Bounds(b) => {
+                assert!((b.min[0] - 2.0).abs() < 1e-6 && (b.max[0] - 3.0).abs() < 1e-6, "{b:?}");
+            }
+            other => panic!("expected bounds, got {other:?}"),
+        }
+        match &receipt.query_results[2] {
+            QueryResult::Entity(e) => assert_eq!(e.kind, "Leader"),
+            other => panic!("expected entity, got {other:?}"),
+        }
+    }
+
     // ── Phase 5 remaining: typed raster image create ─────────────────────────
 
     #[test]
diff --git a/src/app/doc_api_convert.rs b/src/app/doc_api_convert.rs
index 17be1df27..784a1a833 100644
--- a/src/app/doc_api_convert.rs
+++ b/src/app/doc_api_convert.rs
@@ -473,8 +473,31 @@ pub fn entity_bounds(entity: Option<&EntityType>, id: ObjectId) -> ApiResult<Aab
             }
             Aabb { min, max }
         }
+        // Read-mostly families with vertex/point data: bounds from their points.
+        EntityType::Leader(l) => points_aabb(l.vertices.iter().collect(), id)?,
+        EntityType::Mesh(m) => points_aabb(m.vertices.iter().collect(), id)?,
+        EntityType::Face3D(f) => points_aabb(
+            [&f.first_corner, &f.second_corner, &f.third_corner, &f.fourth_corner].into_iter().collect(),
+            id,
+        )?,
+        EntityType::MLine(m) => points_aabb(m.vertices.iter().map(|v| &v.position).collect(), id)?,
+        EntityType::Helix(h) => points_aabb([&h.start_point].into_iter().collect(), id)?,
         // Ray/XLine are unbounded by definition — no finite bounds.
         _ => return Err(ApiError::Unsupported("bounds for this entity family is not yet implemented".into())),
     };
     Ok(bb)
 }
+
+/// AABB over a set of 3D points. `UnknownId` if empty (no points to bound).
+fn points_aabb(pts: Vec<&Vector3>, id: ObjectId) -> ApiResult<Aabb> {
+    if pts.is_empty() {
+        return Err(ApiError::UnknownId(id));
+    }
+    let mut min = [f64::INFINITY; 3];
+    let mut max = [f64::NEG_INFINITY; 3];
+    for p in pts {
+        min = [min[0].min(p.x), min[1].min(p.y), min[2].min(p.z)];
+        max = [max[0].max(p.x), max[1].max(p.y), max[2].max(p.z)];
+    }
+    Ok(Aabb { min, max })
+}