Faster tests: hostile_params_never_panic shares its commands across threads (154 s to 20 s), the design-file fuzz test tries its seeded cases on all cores (21 s to 7.5 s), the kernel's tangent-primitive boolean test runs its three seeds at once, and the headless scenario harness skips the software viewport render it threw away every frame (scenarios 63 s to 26 s). kill_mid_save waits for the saver to reach a varying round instead of sleeping a fixed time, so it holds on a busy machine

crates/ui-egui/src/scenario.rs

@@ -170,6 +170,8 @@ impl Harness {
     /// File pickers answer like a person would: save into the scenario's folder, open the file
     /// the scenario chose.
     fn install(&mut self) {
+        // Frames are laid out, never painted.
+        self.app.viewport.no_pixels = true;
         let dir = self.dir.clone();
         self.app.services.pick_save = Some(Box::new(move |name, _| Some(dir.join(name).to_string_lossy().into_owned())));
         let next = self.next_file.clone();

crates/ui-egui/src/viewport.rs

@@ -35,6 +35,8 @@ pub struct ViewportState {
     hl_slot: SceneSlot,
     hl_key: u64,
     cpu: Option<(u64, egui::TextureHandle)>,
+    /// Nothing will look at the frame (the headless scenario harness): skip the software render.
+    pub no_pixels: bool,
     pub nav: Option<NavMode>,
     /// What a click would pick now (after the active command's filter).
     pub hover: Option<Hit>,
@@ -1927,6 +1929,9 @@ fn overlays(app: &SolveApp, painter: &egui::Painter, proj: &Proj) {
 }
 
 fn cpu_render(app: &mut SolveApp, ctx: &egui::Context, painter: &egui::Painter, rect: Rect, proj: &Proj) {
+    if app.viewport.no_pixels {
+        return;
+    }
     let mut h = std::collections::hash_map::DefaultHasher::new();
     scene_key(app).hash(&mut h);
     for v in [proj.cam.yaw, proj.cam.pitch, proj.cam.distance, proj.cam.target.x, proj.cam.target.y, proj.cam.target.z] {