diff --git a/cimery/crates/viewer/src/lib.rs b/cimery/crates/viewer/src/lib.rs
index d5e6416..af0f16f 100644
--- a/cimery/crates/viewer/src/lib.rs
+++ b/cimery/crates/viewer/src/lib.rs
@@ -25,8 +25,8 @@ use winit::{
 use wgpu::util::DeviceExt;
 use cimery_core::{MaterialGrade, SectionType};
 use cimery_ir::{FeatureId, GirderIR, PscISectionParams, SectionParams};
-use cimery_kernel::{GeomKernel, StubKernel};
-use camera::{Camera, CameraUniform};
+use cimery_kernel::{GeomKernel, PureRustKernel};
+use camera::Camera;
 
 // ─── Vertex ───────────────────────────────────────────────────────────────────
 
@@ -148,7 +148,8 @@ impl RenderState {
             spacing:  0.0,
             material: MaterialGrade::C50,
         };
-        let mesh = StubKernel.girder_mesh(&test_ir).expect("StubKernel mesh");
+        // Sprint 3: replace PureRustKernel with OcctKernel (--features occt)
+        let mesh = PureRustKernel.girder_mesh(&test_ir).expect("PureRustKernel mesh");
 
         let verts: Vec<Vertex> = mesh.vertices.iter().zip(mesh.normals.iter())
             .map(|(p, n)| Vertex { position: *p, normal: *n })
@@ -376,7 +377,7 @@ impl Default for CimeryApp {
 impl ApplicationHandler for CimeryApp {
     fn resumed(&mut self, event_loop: &ActiveEventLoop) {
         let attrs = Window::default_attributes()
-            .with_title("cimery viewer [Sprint 2 — StubKernel]")
+            .with_title("cimery viewer [Sprint 2 — PSC-I PureRustKernel]")
             .with_inner_size(winit::dpi::LogicalSize::new(1280u32, 720u32));
         let window = Arc::new(
             event_loop.create_window(attrs).expect("create window"),