diff --git a/crates/tools/src/draw2/gesture.rs b/crates/tools/src/draw2/gesture.rs
index bdb8e4d84..d4a351e4f 100644
--- a/crates/tools/src/draw2/gesture.rs
+++ b/crates/tools/src/draw2/gesture.rs
@@ -22,6 +22,10 @@ use super::{FEEDBACK, eraser_area, points_json, polyline};
 use crate::guides::DrawSnap;
 use crate::{Action, Cursor, Mods, Overlay, PointerEvent, PointerKind, Tool, ToolContext, ToolKey};
 
+/// How far from its drag the Smooth tool smooths, in screen pixels. The Pencil uses the same
+/// radius while Alt switches it to the Smooth tool.
+const SMOOTH_RADIUS: f64 = 12.0;
+
 pub struct GestureTool {
     /// How many points the last preview of the stroke had ([`crate::previews_at`]).
     previewed: usize,
@@ -339,9 +343,13 @@ impl GestureTool {
         let pts = &self.points;
         let has_sel = !cx.selection.is_empty();
         let tol = cx.tol(self.edit_within);
+        let radius = cx.tol(SMOOTH_RADIUS);
         if self.smoothing {
             if has_sel && pts.len() >= 2 {
-                return vec![Action::Exec("path.smoothRegion".into(), json!({"points": points_json(pts), "radius": tol, "fidelity": self.fidelity}))];
+                return vec![Action::Exec(
+                    "path.smoothRegion".into(),
+                    json!({"points": points_json(pts), "radius": radius, "fidelity": self.fidelity}),
+                )];
             }
             return vec![];
         }
@@ -378,7 +386,7 @@ impl GestureTool {
             )],
             "knife" if pts.len() >= 2 => vec![Action::Exec("path.knife".into(), json!({"points": points_json(pts)}))],
             "smooth" if has_sel && pts.len() >= 2 => {
-                vec![Action::Exec("path.smoothRegion".into(), json!({"points": points_json(pts), "radius": tol, "fidelity": self.fidelity}))]
+                vec![Action::Exec("path.smoothRegion".into(), json!({"points": points_json(pts), "radius": radius, "fidelity": self.fidelity}))]
             }
             "pathEraser" if has_sel => vec![Action::Exec("path.eraseSegments".into(), json!({"points": points_json(pts), "width": cx.tol(8.0)}))],
             "join" if pts.len() >= 2 => vec![Action::Exec("path.joinScrub".into(), json!({"points": points_json(pts), "tolerance": tol}))],
diff --git a/crates/tools/src/draw2/gesture/tests.rs b/crates/tools/src/draw2/gesture/tests.rs
index 2daac5705..d1e07d13b 100644
--- a/crates/tools/src/draw2/gesture/tests.rs
+++ b/crates/tools/src/draw2/gesture/tests.rs
@@ -703,6 +703,34 @@ fn pencil_alt_with_alt_to_smooth_on_smooths_instead_of_drawing_a_line() {
     assert!(matches!(&acts.last().unwrap()[0], Action::Exec(c, v) if c == "path.smoothRegion" && v["points"].as_array().unwrap().len() == 3));
 }
 
+/// While Alt switches the Pencil to the Smooth tool, the Pencil smooths within the Smooth tool's
+/// radius at any Edit selected paths Within value, 0 included.
+#[test]
+fn pencil_alt_smooths_within_the_smooth_tools_radius() {
+    let (d, id) = doc_with_rect();
+    let mut s = Selection::default();
+    s.set([id]);
+    let p = paint();
+    let mut cx = cx(&d, &s, &p);
+    cx.smart_guides = false;
+    let pts = [(50.0, 150.0), (150.0, 150.0), (250.0, 160.0)];
+    let radius = |acts: &[Vec<Action>]| match acts.last().and_then(|a| a.first()) {
+        Some(Action::Exec(c, v)) if c == "path.smoothRegion" => v["radius"].as_f64().unwrap(),
+        a => panic!("expected path.smoothRegion, got: {a:?}"),
+    };
+    let alt = Mods { alt: true, ..Default::default() };
+    for zoom in [1.0, 2.0] {
+        cx.zoom = zoom;
+        let want = radius(&drag(&mut GestureTool::new("smooth"), &cx, &pts, Mods::default()));
+        for within in [0.0, 5.0, 40.0] {
+            let mut t = GestureTool::new("pencil");
+            t.set_option("altSmooth", &json!(true));
+            t.set_option("editWithin", &json!(within));
+            assert_eq!(radius(&drag_held(&mut t, &cx, &pts, alt)), want, "zoom {zoom}, editWithin {within}");
+        }
+    }
+}
+
 /// #3799: Alt's line starts and ends on Smart Guides as a stroke does, and pressed on an end of
 /// a selected open path it continues the path from that end to the pointer.
 #[test]