Improve behavior authoring and typed trace history (untested checkpoint)

crates/oa-desktop/src/behavior/topology.rs

@@ -836,6 +836,12 @@ struct GraphEdge {
     incidence: bool,
     layer: EdgeLayer,
 }
+// Ordered exchange adjacency is a projection, never a persisted relation ID.
+struct OrderedPath {
+    source: Id,
+    target: Id,
+    points: Vec<Point>,
+}
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum EdgeLayer {
     Direct,
@@ -863,6 +869,8 @@ struct Graph<'a> {
     scroll_offset: iced::Vector,
     nodes: Vec<GraphNode>,
     edges: Vec<GraphEdge>,
+    ordered_paths: Vec<OrderedPath>,
+    ordered: bool,
     size: Size,
     selected: Id,
     scale: f32,
@@ -884,11 +892,17 @@ impl<'a> Graph<'a> {
         let context_index = oa_core::topology_context::TopologyIndex::new(p);
         let choices = contributions(p, owner);
         let links = sequence_links(p, owner);
+        let order = legacy_order(p, owner);
+        let adjacency: Vec<_> = links
+            .iter()
+            .map(|r| (r.source(), r.target()))
+            .chain(order.windows(2).map(|pair| (pair[0], pair[1])))
+            .collect();
         let ids: BTreeSet<_> = choices.iter().map(|c| c.id).collect();
         let mut incoming: BTreeMap<_, usize> = ids.iter().map(|id| (*id, 0)).collect();
         let mut ranks: BTreeMap<_, usize> = ids.iter().map(|id| (*id, 0)).collect();
-        for r in &links {
-            *incoming.entry(r.target()).or_default() += 1;
+        for &(_, target) in &adjacency {
+            *incoming.entry(target).or_default() += 1;
         }
         let mut queue: Vec<_> = choices
             .iter()
@@ -903,8 +917,7 @@ impl<'a> Graph<'a> {
             if !done.insert(id) {
                 continue;
             }
-            for r in links.iter().filter(|r| r.source() == id) {
-                let next = r.target();
+            for &(_, next) in adjacency.iter().filter(|(source, _)| *source == id) {
                 ranks.insert(next, ranks[&next].max(ranks[&id] + 1));
                 let count = incoming.get_mut(&next).expect("Graph endpoint");
                 *count = count.saturating_sub(1);
@@ -1031,6 +1044,29 @@ impl<'a> Graph<'a> {
             size.height = size.height.max(node.rect.y + node.rect.height + 42.);
             nodes.push(node);
         }
+        let ordered_paths = order
+            .windows(2)
+            .map(|pair| {
+                let a = nodes
+                    .iter()
+                    .find(|n| n.id == pair[0])
+                    .expect("ordered source")
+                    .rect;
+                let b = nodes
+                    .iter()
+                    .find(|n| n.id == pair[1])
+                    .expect("ordered target")
+                    .rect;
+                OrderedPath {
+                    source: pair[0],
+                    target: pair[1],
+                    points: vec![
+                        Point::new(a.x + a.width, a.center_y()),
+                        Point::new(b.x, b.center_y()),
+                    ],
+                }
+            })
+            .collect();
         let mut edges = vec![];
         let mut routed_pairs = BTreeSet::new();
         for (i, r) in links.into_iter().enumerate() {
@@ -1165,6 +1201,8 @@ impl<'a> Graph<'a> {
             scroll_offset: iced::Vector::ZERO,
             nodes,
             edges,
+            ordered_paths,
+            ordered: !order.is_empty(),
             size,
             selected,
             scale: 1.,
@@ -1264,6 +1302,18 @@ impl canvas::Program<Message> for Graph<'_> {
         for pass in PAINT_PASSES {
             match pass {
                 PaintPass::DirectEdges | PaintPass::ContextualEdges => {
+                    if pass == PaintPass::DirectEdges {
+                        for path in &self.ordered_paths {
+                            let selected =
+                                path.source == self.selected || path.target == self.selected;
+                            draw_arrow(
+                                &mut f,
+                                &path.points,
+                                if selected { style::TEAL } else { style::MUTED },
+                                if selected { 2.5 } else { 1.5 },
+                            );
+                        }
+                    }
                     for e in self.edges.iter().filter(|edge| {
                         edge.layer
                             == if pass == PaintPass::DirectEdges {
@@ -1465,6 +1515,11 @@ impl canvas::Program<Message> for Graph<'_> {
         if cursor.position_in(bounds).is_some_and(|p| {
             let p = Point::new(p.x / self.scale, p.y / self.scale);
             self.nodes.iter().any(|n| n.rect.contains(p))
+                || self.ordered_paths.iter().any(|path| {
+                    path.points.windows(2).any(|pair| {
+                        crate::diagram::distance_to_segment(p, pair[0], pair[1]) < 8. / self.scale
+                    })
+                })
                 || self.edges.iter().any(|e| {
                     e.label.contains(p)
                         || e.points

crates/oa-desktop/src/behavior/topology/direct.rs

@@ -238,9 +238,7 @@ impl State {
         ) {
             return Err("Choose a contribution tool.".into());
         }
-        if !legacy_order(p, context.owner).is_empty() {
-            return Err("Convert the ordered path to explicit links before drawing.".into());
-        }
+        let order = legacy_order(p, context.owner);
         let link = insertion
             .link
             .map(|id| {
@@ -268,6 +266,13 @@ impl State {
         if let Some(r) = link {
             d.before = Some(r.source());
             d.after = Some(r.target());
+        } else if !order.is_empty() {
+            let index = insertion
+                .before
+                .and_then(|id| order.iter().position(|v| *v == id))
+                .unwrap_or(order.len());
+            d.before = index.checked_sub(1).map(|i| order[i]);
+            d.after = order.get(index).copied();
         }
         Ok(())
     }
@@ -416,6 +421,13 @@ impl Input {
     }
 }
 impl Graph<'_> {
+    fn ordered_path_at(&self, point: Point) -> Option<&OrderedPath> {
+        self.ordered_paths.iter().find(|path| {
+            path.points.windows(2).any(|pair| {
+                crate::diagram::distance_to_segment(point, pair[0], pair[1]) < 8. / self.scale
+            })
+        })
+    }
     fn node_at(&self, point: Point) -> Option<Id> {
         self.nodes
             .iter()
@@ -579,7 +591,9 @@ impl Graph<'_> {
                                 link: self
                                     .edge_at(point)
                                     .filter(|_| self.node_at(point).is_none()),
-                                before: self.node_at(point),
+                                before: self.node_at(point).or_else(|| {
+                                    self.ordered_path_at(point).map(|path| path.target)
+                                }),
                             },
                         });
                     }
@@ -807,6 +821,13 @@ impl Graph<'_> {
                     draw_arrow(f, &e.points, style::TEAL, 3.);
                 }
                 "Insert on this path · preserve its guard"
+            } else if let Some(path) = self.ordered_path_at(point) {
+                draw_arrow(f, &path.points, style::TEAL, 3.);
+                "Insert on ordered path · preserve its order"
+            } else if self.ordered && self.node_at(point).is_some() {
+                "Insert before this contribution · preserve path"
+            } else if self.ordered {
+                "Continue the ordered path"
             } else if self.node_at(point).is_some() {
                 "Add before this contribution · unconnected"
             } else {

crates/oa-desktop/src/behavior/topology/direct_tests.rs

@@ -970,6 +970,359 @@ fn direct_process_append_preserves_existing_order_and_rejects_incompatible_excha
     }
 }
 
+fn assert_interactive_owner_view(p: &Project, owner: Id) {
+    use iced::advanced::widget::Tree;
+    fn contains(tree: &Tree, tag: iced::advanced::widget::tree::Tag) -> bool {
+        tree.tag == tag || tree.children.iter().any(|child| contains(child, tag))
+    }
+    let mut app = App::with_project(p.clone());
+    app.layer = p.elements[&owner].layer();
+    app.page = crate::app::Page::Behavior;
+    app.selected = owner;
+    app.behavior.active_owner = Some(owner);
+    let graph: Element<'_, Message> = canvas::Canvas::new(Graph::new(p, owner, owner)).into();
+    let tag = Tree::new(graph.as_widget()).tag;
+    let view = view::view(&app, owner, Column::new());
+    assert!(
+        contains(&Tree::new(view.as_widget()), tag),
+        "every path uses the interactive graph"
+    );
+}
+
+#[test]
+fn direct_process_three_ordered_exchanges_preserve_outer_paths_on_insertion() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let (mut f, next) = empty_exchange_fixture(layer);
+        f.p = execute_batch(
+            &f.p,
+            &[Command::Connect(
+                f.p.relations[&f.exchange].kind(),
+                "Return for reassessment".into(),
+                f.work[2],
+                f.work[0],
+            )],
+        )
+        .unwrap();
+        let last =
+            f.p.relations
+                .values()
+                .find(|r| r.name == "Return for reassessment")
+                .unwrap()
+                .id;
+        for exchange in [f.exchange, next, last] {
+            let node = occurrence(
+                &f.p,
+                f.owner,
+                "Ordered contribution",
+                OccurrenceBody::Exchange {
+                    operation: None,
+                    exchange: Some(exchange),
+                    sender: None,
+                    receiver: None,
+                    message_kind: MessageKind::default(),
+                    reply_to: None,
+                    values: vec![],
+                },
+            );
+            f.p = execute_batch(&f.p, &[Command::CreateElement(node)]).unwrap();
+        }
+        for index in [0, 2] {
+            let mut doc = Document::from_project(f.p.clone(), ProjectLimits::default()).unwrap();
+            let before = doc.bundle().clone();
+            let old_order = legacy_order(doc.project(), f.owner);
+            let graph = Graph::new(doc.project(), f.owner, f.owner);
+            assert_eq!(graph.ordered_paths.len(), 2);
+            assert!(graph.edges.is_empty());
+            let mut state = State::default();
+            state
+                .begin(
+                    doc.project(),
+                    context(f.owner),
+                    Tool::Work,
+                    ControlKind::Choice,
+                    Insertion {
+                        link: None,
+                        before: Some(old_order[index]),
+                    },
+                )
+                .unwrap();
+            state
+                .update(
+                    doc.project(),
+                    Event::Target(Choice {
+                        id: f.work[index],
+                        label: "Shared activity".into(),
+                    }),
+                )
+                .unwrap();
+            doc.execute(state.prepare_pending(doc.project()).unwrap())
+                .unwrap();
+            let added = created(&f.p, doc.project(), f.owner);
+            let mut expected = old_order;
+            expected.insert(index, added);
+            assert_eq!(doc.project().elements[&f.owner].steps().unwrap(), &expected);
+            let links = sequence_links(doc.project(), f.owner);
+            assert_eq!(links.len(), 3);
+            for pair in expected.windows(2) {
+                assert_eq!(
+                    links
+                        .iter()
+                        .filter(|r| r.source() == pair[0] && r.target() == pair[1])
+                        .count(),
+                    1
+                );
+            }
+            for (id, relation) in &f.p.relations {
+                assert_eq!(&doc.project().relations[id], relation);
+            }
+            let after = doc.bundle().clone();
+            assert!(doc.undo());
+            assert_eq!(doc.bundle(), &before);
+            assert_eq!(doc.project(), &f.p);
+            assert!(doc.redo());
+            assert_eq!(doc.bundle(), &after);
+        }
+    }
+}
+
+#[test]
+fn direct_process_incompatible_imported_order_rejects_conversion_without_losing_draft() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let (mut f, _) = empty_exchange_fixture(layer);
+        // Repeated exchange uses have different occurrences, but this legacy path
+        // has an endpoint gap. Converting its implied adjacency must reject.
+        for _ in 0..2 {
+            let node = occurrence(
+                &f.p,
+                f.owner,
+                "Repeated exchange",
+                OccurrenceBody::Exchange {
+                    operation: None,
+                    exchange: Some(f.exchange),
+                    sender: None,
+                    receiver: None,
+                    message_kind: MessageKind::default(),
+                    reply_to: None,
+                    values: vec![],
+                },
+            );
+            f.p = execute_batch(&f.p, &[Command::CreateElement(node)]).unwrap();
+        }
+        let mut doc = Document::from_project(f.p.clone(), ProjectLimits::default()).unwrap();
+        let before = doc.bundle().clone();
+        assert_interactive_owner_view(doc.project(), f.owner);
+        assert_eq!(
+            Graph::new(doc.project(), f.owner, f.owner)
+                .ordered_paths
+                .len(),
+            1
+        );
+        let mut state = State::default();
+        state
+            .begin(
+                doc.project(),
+                context(f.owner),
+                Tool::Control,
+                ControlKind::Choice,
+                Insertion::default(),
+            )
+            .unwrap();
+        state
+            .update(
+                doc.project(),
+                Event::Name("Retain this proposed decision".into()),
+            )
+            .unwrap();
+        assert!(state.prepare_pending(doc.project()).is_err());
+        assert_eq!(
+            state.draft.as_ref().unwrap().name,
+            "Retain this proposed decision"
+        );
+        assert_eq!(doc.bundle(), &before);
+        assert_eq!(doc.project(), &f.p);
+        assert!(!doc.undo(), "rejection must not create history");
+        state.update(doc.project(), Event::Cancel).unwrap();
+        assert!(state.draft.is_none());
+        assert_eq!(doc.bundle(), &before);
+    }
+}
+
+#[test]
+fn direct_process_empty_first_and_second_exchange_keep_the_same_interactive_renderer() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let (f, next) = empty_exchange_fixture(layer);
+        let mut doc = Document::from_project(f.p.clone(), ProjectLimits::default()).unwrap();
+        for (index, target) in [f.exchange, next].into_iter().enumerate() {
+            assert_interactive_owner_view(doc.project(), f.owner);
+            let before = doc.bundle().clone();
+            let mut graph = Graph::new(doc.project(), f.owner, f.owner);
+            let c = context(f.owner);
+            graph.interaction = Some((
+                c,
+                CanvasTool::Add(Tool::Exchange, ControlKind::Choice),
+                true,
+            ));
+            let mut input = Input::default();
+            let bounds = Rectangle::with_size(graph.size);
+            let point = Point::new(graph.size.width - 10., graph.size.height - 10.);
+            send(
+                &graph,
+                &mut input,
+                mouse::Event::ButtonPressed(mouse::Button::Left),
+                point,
+                bounds,
+            );
+            let Some(Message::TopologyCanvas(CanvasEvent::Begin { insertion, .. })) = send(
+                &graph,
+                &mut input,
+                mouse::Event::ButtonReleased(mouse::Button::Left),
+                point,
+                bounds,
+            ) else {
+                panic!("canvas retains direct exchange insertion");
+            };
+            let mut state = State::default();
+            state
+                .begin(
+                    doc.project(),
+                    c,
+                    Tool::Exchange,
+                    ControlKind::Choice,
+                    insertion,
+                )
+                .unwrap();
+            state
+                .update(
+                    doc.project(),
+                    Event::Target(Choice {
+                        id: target,
+                        label: "Exchange".into(),
+                    }),
+                )
+                .unwrap();
+            doc.execute(state.prepare_pending(doc.project()).unwrap())
+                .unwrap();
+            assert_eq!(
+                doc.project().elements[&f.owner].steps().unwrap().len(),
+                index + 1
+            );
+            assert_eq!(sequence_links(doc.project(), f.owner).len(), index);
+            assert_interactive_owner_view(doc.project(), f.owner);
+            let after = doc.bundle().clone();
+            assert!(doc.undo());
+            assert_eq!(doc.bundle(), &before);
+            assert!(doc.redo());
+            assert_eq!(doc.bundle(), &after);
+        }
+    }
+}
+
+#[test]
+fn direct_process_imported_order_is_projected_without_mutation_and_first_canvas_edit_is_atomic() {
+    for layer in [Layer::Oa, Layer::Sa] {
+        let (mut f, next) = empty_exchange_fixture(layer);
+        for exchange in [f.exchange, next] {
+            let node = occurrence(
+                &f.p,
+                f.owner,
+                "Imported exchange",
+                OccurrenceBody::Exchange {
+                    operation: None,
+                    exchange: Some(exchange),
+                    sender: None,
+                    receiver: None,
+                    message_kind: MessageKind::default(),
+                    reply_to: None,
+                    values: vec![],
+                },
+            );
+            f.p = execute_batch(&f.p, &[Command::CreateElement(node)]).unwrap();
+        }
+        let mut doc = Document::from_project(f.p.clone(), ProjectLimits::default()).unwrap();
+        let before = doc.bundle().clone();
+        let order = legacy_order(doc.project(), f.owner);
+        assert_eq!(order.len(), 2);
+        assert_interactive_owner_view(doc.project(), f.owner);
+        let mut graph = Graph::new(doc.project(), f.owner, order[0]);
+        assert!(
+            graph.edges.is_empty(),
+            "projection never invents relation identities"
+        );
+        assert_eq!(graph.ordered_paths.len(), 1);
+        assert!(position(&graph, order[0]).x < position(&graph, order[1]).x);
+        let points = &graph.ordered_paths[0].points;
+        let point = Point::new((points[0].x + points[1].x) / 2., points[0].y);
+        let c = context(f.owner);
+        graph.interaction = Some((c, CanvasTool::Add(Tool::Work, ControlKind::Choice), true));
+        let mut input = Input::default();
+        let bounds = Rectangle::with_size(graph.size);
+        send(
+            &graph,
+            &mut input,
+            mouse::Event::ButtonPressed(mouse::Button::Left),
+            point,
+            bounds,
+        );
+        let Some(Message::TopologyCanvas(CanvasEvent::Begin { insertion, .. })) = send(
+            &graph,
+            &mut input,
+            mouse::Event::ButtonReleased(mouse::Button::Left),
+            point,
+            bounds,
+        ) else {
+            panic!("ordered arrow supports direct insertion");
+        };
+        assert_eq!(
+            insertion,
+            Insertion {
+                link: None,
+                before: Some(order[1])
+            }
+        );
+        assert_eq!(doc.bundle(), &before);
+        let mut state = State::default();
+        state
+            .begin(doc.project(), c, Tool::Work, ControlKind::Choice, insertion)
+            .unwrap();
+        state
+            .update(
+                doc.project(),
+                Event::Target(Choice {
+                    id: f.work[1],
+                    label: "Respond".into(),
+                }),
+            )
+            .unwrap();
+        doc.execute(state.prepare_pending(doc.project()).unwrap())
+            .unwrap();
+        let inserted = created(&f.p, doc.project(), f.owner);
+        assert_eq!(
+            doc.project().elements[&f.owner].steps().unwrap(),
+            &[order[0], inserted, order[1]]
+        );
+        let links = sequence_links(doc.project(), f.owner);
+        assert_eq!(links.len(), 2);
+        for (a, b) in [(order[0], inserted), (inserted, order[1])] {
+            assert!(
+                links
+                    .iter()
+                    .any(|link| link.source() == a && link.target() == b)
+            );
+        }
+        assert!(
+            Graph::new(doc.project(), f.owner, inserted)
+                .ordered_paths
+                .is_empty()
+        );
+        for id in f.work {
+            assert_eq!(doc.project().elements[&id], f.p.elements[&id]);
+        }
+        assert!(doc.undo());
+        assert_eq!(doc.bundle(), &before);
+        assert_eq!(doc.project(), &f.p);
+    }
+}
+
 #[test]
 fn direct_process_palette_preserves_fit_and_manual_camera() {
     for layer in [Layer::Oa, Layer::Sa] {

crates/oa-desktop/src/behavior/topology/view.rs

@@ -59,21 +59,16 @@ pub(super) fn choice_page(len: usize, requested: usize) -> std::ops::Range<usize
     let start = requested.min(len.saturating_sub(1) / 24) * 24;
     start..(start + 24).min(len)
 }
-pub(super) fn view<'a>(
-    app: &'a App,
-    owner: Id,
-    mut out: Column<'a, Message>,
-) -> Element<'a, Message> {
+pub(super) fn view<'a>(app: &'a App, owner: Id, out: Column<'a, Message>) -> Element<'a, Message> {
     let p = app.project();
     let context = app.topology_context().expect("visible process context");
     let state = &app.behavior.topology;
     let pending = state.draft.is_some();
-    let explicit =
-        uses_explicit_topology(p, owner) || p.elements[&owner].steps().is_none_or(Vec::is_empty);
+    let ordered = !legacy_order(p, owner).is_empty();
     let selected = is_contribution(p, owner, app.selected).then_some(app.selected);
     let choose = |tool| Message::TopologyCanvas(CanvasEvent::Choose(context, tool));
     let mut controls = Column::new().spacing(6);
-    if !pending && explicit {
+    if !pending {
         controls = controls
             .push(
                 row![
@@ -156,10 +151,22 @@ pub(super) fn view<'a>(
                 .spacing(6),
             );
     }
-    controls=controls.push(label(if pending{"Pending contribution · apply or cancel below"}else if !explicit{"Ordered contributions · Append exchange continues the path"}else{match state.tool{
+    controls=controls.push(label(if pending{"Pending contribution · apply or cancel below"}else if ordered{"Ordered exchange path · click a path to insert or empty canvas to continue; the edit preserves its order"}else{match state.tool{
         CanvasTool::Select=>"Select local contributions and paths · drag path endpoints to reconnect · ↕ reorders within a column",
         CanvasTool::Connect=>"Sequence link · click or drag from preceding to following contribution · Escape cancels",
         CanvasTool::Add(..)=>"Choose a highlighted path or contribution position · existing work stays shared · Escape cancels"}}));
+    if !pending && ordered {
+        controls = controls.push(button("Append exchange…").on_press(Message::TopologyCanvas(
+            CanvasEvent::AppendExchange(context),
+        )));
+        let commands = preserved_order(p, owner, None);
+        if !commands.is_empty() {
+            controls = controls.push(
+                button("Edit path links and guards")
+                    .on_press(Message::Command(unique_batch(p, commands))),
+            );
+        }
+    }
     // A fixed sibling keeps Iced's canvas scroll state through selection/form changes.
     let mut navigation = column![].spacing(6);
     if let Some(Relation {
@@ -249,7 +256,7 @@ pub(super) fn view<'a>(
             button("Back to caller").on_press(Message::TopologyCanvas(CanvasEvent::Back(context))),
         );
     }
-    let diagram = if explicit {
+    let diagram = {
         let mut graph = Graph::expanded_qualified(
             p,
             owner,
@@ -373,58 +380,6 @@ pub(super) fn view<'a>(
             state.shelf.is_some(),
             pending,
         )
-    } else {
-        out = out
-            .push(
-                button(if state.focused {
-                    "Restore explorer and properties"
-                } else {
-                    "Focus canvas"
-                })
-                .on_press(Message::TopologyCanvas(CanvasEvent::Focus(context))),
-            )
-            .push(controls)
-            .push(navigation);
-        out = out.push(label(
-            "Ordered exchange path · append the next exchange or convert to explicit links.",
-        ));
-        if !pending {
-            out = out.push(
-                button("Append exchange…")
-                    .on_press(Message::TopologyCanvas(CanvasEvent::AppendExchange(context))),
-            ).push(label("Append creates the next exchange contribution and an explicit sequence link from the final contribution in one undo step."));
-        }
-        let commands = preserved_order(p, owner, None);
-        if !commands.is_empty() {
-            out = out.push(
-                button("Convert ordered path to explicit links")
-                    .on_press(Message::Command(unique_batch(p, commands))),
-            );
-        } else {
-            out=out.push(label("A single exchange has no path link to convert. Append the next exchange, or involve work, a control or a reusable process."))
-            .push(row![button("Add work…").on_press(event(Event::Start(owner,Tool::Work,selected))),
-                button("Add control…").on_press(event(Event::Start(owner,Tool::Control,selected))),
-                button("Reuse…").on_press(event(Event::Start(owner,Tool::Reuse,selected)))].spacing(6));
-        }
-        let scene = Scene::sequence(p, owner, app.selected);
-        let size = scene.size;
-        out = out.push(
-            scrollable(
-                canvas::Canvas::new(scene)
-                    .width(size.width)
-                    .height(size.height),
-            )
-            .direction(scrollable::Direction::Both {
-                vertical: scrollable::Scrollbar::default(),
-                horizontal: scrollable::Scrollbar::default(),
-            })
-            .height(240.),
-        );
-        super::super::scenario_scroll::observe_topology(
-            context,
-            scenario::ScrollArea::Page,
-            scrollable(out.padding(18)),
-        )
     };
     let mut form_panel: Element<'_, Message> = iced::widget::Space::new().height(0).into();
     if let Some(d) = state.draft.as_ref().filter(|d| d.owner == owner) {
@@ -451,6 +406,17 @@ pub(super) fn view<'a>(
                     p.named(link.target()),
                     guard
                 )));
+            } else if d.fixed && ordered {
+                form = form.push(label(match (d.before, d.after) {
+                    (Some(before), Some(after)) => format!(
+                        "Insert between {} → {} · preserve the ordered path",
+                        p.named(before),
+                        p.named(after)
+                    ),
+                    (Some(before), None) => format!("Continue after {}", p.named(before)),
+                    (None, Some(after)) => format!("Insert before {}", p.named(after)),
+                    _ => "Start the ordered path".into(),
+                }));
             } else if d.fixed
                 && d.tool == Tool::Exchange
                 && let Some(before) = d.before