🐛 Fix round/square linecaps not being applied correctly in open paths

render-wasm/src/render/strokes.rs

@@ -302,6 +302,12 @@ fn handle_stroke_caps(
         return;
     }
 
+    // When both ends share the same simple line cap, Skia already drew it
+    // natively via `PaintCap` on the stroke paint, so skip the manual overlay.
+    if stroke.to_skia_linecap().is_some() {
+        return;
+    }
+
     // Curves can have duplicated points, so let's remove consecutive duplicated points
     let mut points = path.points().to_vec();
     points.dedup();

render-wasm/src/shapes/strokes.rs

@@ -293,6 +293,10 @@ impl Stroke {
             }
         }
 
+        if let Some(cap) = self.to_skia_linecap() {
+            paint.set_stroke_cap(cap);
+        }
+
         paint
     }
 
@@ -330,6 +334,19 @@ impl Stroke {
         cap_margin_for_cap(self.cap_start, self.width)
             .max(cap_margin_for_cap(self.cap_end, self.width))
     }
+
+    /// Returns a Skia `PaintCap` to apply natively on the stroke paint when
+    /// both ends share the same simple line cap (`Round/Round` or
+    /// `Square/Square`). Skia only emits cap geometry at sub-path endpoints,
+    /// so this is a no-op on closed paths and avoids the extra fill draw the
+    /// manual caps would otherwise require on open paths.
+    pub fn to_skia_linecap(&self) -> Option<skia::paint::Cap> {
+        match (self.cap_start, self.cap_end) {
+            (Some(StrokeCap::Round), Some(StrokeCap::Round)) => Some(skia::paint::Cap::Round),
+            (Some(StrokeCap::Square), Some(StrokeCap::Square)) => Some(skia::paint::Cap::Square),
+            _ => None,
+        }
+    }
 }
 
 fn align_rect_to_half_pixel(rect: &Rect, stroke_width: f32, scale: f32) -> Rect {