diff --git a/crates/engine/src/cmd/draw/line_pline.rs b/crates/engine/src/cmd/draw/line_pline.rs
--- a/crates/engine/src/cmd/draw/line_pline.rs
+++ b/crates/engine/src/cmd/draw/line_pline.rs
@@ -256,6 +256,12 @@ impl Interactive for PlineM {
     fn name(&self) -> &'static str {
         "PLINE"
     }
+    /// Segments start at PLINEWID, the width the last Width or Halfwidth answer left.
+    fn begin(&mut self, s: &mut Session) -> Result<Step> {
+        let w = s.doc()?.header.f64("PLINEWID", 0.0);
+        (self.start_w, self.end_w) = if w.is_finite() && w > 0.0 { (w, w) } else { (0.0, 0.0) };
+        Ok(Step::Continue)
+    }
     fn prompt(&self, s: &Session) -> Prompt {
         if self.asking_width > 0 {
             let unit = if self.half { "half-width" } else { "width" };
@@ -302,6 +308,11 @@ impl Interactive for PlineM {
                 self.end_w = self.start_w;
             }
             self.asking_width = if self.asking_width == 1 { 2 } else { 0 };
+            if self.asking_width == 0 {
+                // The ending width becomes PLINEWID, the next polyline's width (AutoCAD:
+                // Halfwidth 0.5 0.5 leaves PLINEWID 1).
+                s.doc_mut()?.header.set_f64("PLINEWID", self.end_w);
+            }
             return Ok(Step::Continue);
         }
         if let (Some(a), Some(st)) = (self.ask, self.verts.last().map(|v| v.p)) {
@@ -365,6 +376,10 @@ impl Interactive for PlineM {
                         l.bulge = 0.0;
                         (l.start_width, l.end_width) = (0.0, 0.0);
                     }
+                    // Back to the mode of the segment now last (AutoCAD: `_A` point `_U` returns
+                    // to "Specify next point", where `_L` is Length, not arc mode's Line).
+                    let n = self.verts.len();
+                    self.arc_mode = n >= 2 && self.verts.get(n - 2).is_some_and(|v| v.bulge != 0.0);
                     self.sync(s, false)?;
                     Ok(Step::Continue)
                 }
diff --git a/crates/engine/src/tests.rs b/crates/engine/src/tests.rs
--- a/crates/engine/src/tests.rs
+++ b/crates/engine/src/tests.rs
@@ -1226,6 +1226,43 @@ fn pline_width_answers_taper_the_next_segment() {
     assert_eq!(widths(&p), (0.0, vec![(0.0, 0.0), (0.0, 0.0)]));
 }
 
+/// PLINE against what AutoCAD 2024 stores for the same typed input (black-box: synthetic input
+/// in accoreconsole, read back with `entget` and GETVAR).
+#[test]
+fn pline_undo_mode_and_plinewid_match_autocad() {
+    // Undo after an arc segment returns to line mode, where `_L` is Length (a point gives the
+    // length, along the last segment).
+    let p = typed_pline(
+        "pline -0.702422643378533,-28.46727901968281 -27.912058384977463,-34.74188138168937 -22.546524604415925,32.44142803067136 _U \
+         25.831317263304115,13.510616645626207 _A -33.2372517304228,12.083585785350365 _U _L -22.546524604415925,32.44142803067136",
+    );
+    let want = [
+        (-0.7024226433785329, -28.4672790196828),
+        (-27.91205838497746, -34.74188138168937),
+        (25.83131726330411, 13.5106166456262),
+        (64.48701958199356, 48.21692560701169),
+    ];
+    assert_eq!(p.vertices.len(), want.len(), "{p:?}");
+    for (v, (x, y)) in p.vertices.iter().zip(want) {
+        assert!(v.p.near(Vec2::new(x, y), 1e-9 * x.abs().max(y.abs())) && v.bulge == 0.0, "{p:?}");
+    }
+    // PLINEWID is the width a new polyline starts with…
+    let mut s = Session::new();
+    s.cmdline("(setvar \"PLINEWID\" 0.75)").unwrap();
+    s.cmdline("pline -21.06802233135781,9.943678105070298 -29.261665218975015,-28.460093326613574 7.898763272534772,6.73634194079888").unwrap();
+    s.cmdline("").unwrap();
+    assert!(matches!(&s.doc().unwrap().model.last().unwrap().kind, EntityKind::LwPolyline(p) if p.const_width == 0.75));
+    // …and the ending width of the last Width or Halfwidth answer (half-width 0.5: PLINEWID 1).
+    let mut s = Session::new();
+    s.cmdline(
+        "pline -9.151085154682761,12.9438035725412 _W 0.0934460985004879 1.547654372298795 19.161590651864245,38.23079339857958 \
+         26.720225103092986,-9.028145532375504 _H 0.5 0.5 -24.7035288980598,-14.309723714209586",
+    )
+    .unwrap();
+    s.cmdline("").unwrap();
+    assert_eq!(s.doc().unwrap().header.f64("PLINEWID", 0.0), 1.0);
+}
+
 #[test]
 fn press_and_drag_selection_window() {
     let mut s = Session::new();