diff --git a/crates/oa-desktop/src/behavior/topology/layout_tests.rs b/crates/oa-desktop/src/behavior/topology/layout_tests.rs
new file mode 100644
index 00000000..04cc0d0c
--- /dev/null
+++ b/crates/oa-desktop/src/behavior/topology/layout_tests.rs
@@ -0,0 +1,138 @@
+use super::*;
+use iced::advanced::{Layout, layout, widget};
+use iced::{Rectangle, Vector};
+
+#[derive(Default)]
+struct Geometry {
+    scrolls: Vec<(Option<widget::Id>, Rectangle, Vector)>,
+    actions: Option<Rectangle>,
+}
+impl widget::Operation for Geometry {
+    fn traverse(&mut self, operate: &mut dyn FnMut(&mut dyn widget::Operation)) {
+        operate(self);
+    }
+    fn container(&mut self, id: Option<&widget::Id>, bounds: Rectangle) {
+        if id == Some(&widget::Id::new("test-process-actions")) {
+            self.actions = Some(bounds);
+        }
+    }
+    fn scrollable(
+        &mut self,
+        id: Option<&widget::Id>,
+        bounds: Rectangle,
+        _: Rectangle,
+        translation: Vector,
+        _: &mut dyn widget::operation::Scrollable,
+    ) {
+        self.scrolls.push((id.cloned(), bounds, translation));
+    }
+}
+fn workspace(pending: bool) -> iced::Element<'static, Message, iced::Theme, ()> {
+    let diagram = scrollable(iced::widget::Space::new().width(500).height(1200))
+        .id("test-process-page")
+        .height(Fill)
+        .into();
+    let form = if pending {
+        editor_panel(
+            container(iced::widget::Space::new().height(32))
+                .id("test-process-actions")
+                .into(),
+            iced::widget::Space::new().height(1400).into(),
+        )
+    } else {
+        iced::widget::Space::new().height(0).into()
+    };
+    panes(diagram, form, pending)
+}
+fn geometry(
+    view: &mut iced::Element<'_, Message, iced::Theme, ()>,
+    tree: &mut widget::Tree,
+    size: Size,
+) -> (layout::Node, Geometry) {
+    let node = view
+        .as_widget_mut()
+        .layout(tree, &(), &layout::Limits::new(Size::ZERO, size));
+    let mut geometry = Geometry::default();
+    view.as_widget_mut()
+        .operate(tree, Layout::new(&node), &(), &mut geometry);
+    (node, geometry)
+}
+
+#[test]
+fn direct_process_pending_editor_uses_available_height_and_keeps_actions_visible() {
+    // Actual available center-pane sizes at the minimum/default supported windows.
+    // Space represents arbitrarily long diagram/form content; the production
+    // pane/card builders and real Iced layout/scroll operations are exercised.
+    for size in [Size::new(500., 570.), Size::new(840., 770.)] {
+        let mut view = workspace(false);
+        let mut tree = widget::Tree::new(view.as_widget());
+        let (node, _) = geometry(&mut view, &mut tree, size);
+        let mut scroll = widget::operation::scrollable::scroll_to::<()>(
+            widget::Id::new("test-process-page"),
+            widget::operation::scrollable::AbsoluteOffset {
+                x: None,
+                y: Some(180.),
+            },
+        );
+        view.as_widget_mut()
+            .operate(&mut tree, Layout::new(&node), &(), &mut scroll);
+        view = workspace(true);
+        tree.diff(view.as_widget());
+        let (node, before) = geometry(&mut view, &mut tree, size);
+        let page = before
+            .scrolls
+            .iter()
+            .find(|s| s.0 == Some(widget::Id::new("test-process-page")))
+            .unwrap();
+        let form = before
+            .scrolls
+            .iter()
+            .find(|s| s.0 == Some(widget::Id::new("process-form")))
+            .unwrap();
+        assert_eq!(node.size(), size);
+        assert!(
+            form.1.height >= 200.,
+            "usable form viewport: {size:?} {:?}",
+            form.1
+        );
+        assert!(form.1.y >= page.1.y + page.1.height);
+        assert!(form.1.y + form.1.height <= size.height);
+        assert_eq!(page.2.y, 180., "opening a form retains the page scroll");
+        let actions = before.actions.unwrap();
+        assert!(actions.y >= page.1.y + page.1.height);
+        assert!(actions.y + actions.height <= form.1.y);
+        let mut scroll = widget::operation::scrollable::scroll_to::<()>(
+            widget::Id::new("process-form"),
+            widget::operation::scrollable::AbsoluteOffset {
+                x: None,
+                y: Some(600.),
+            },
+        );
+        view.as_widget_mut()
+            .operate(&mut tree, Layout::new(&node), &(), &mut scroll);
+        let (_, after) = geometry(&mut view, &mut tree, size);
+        assert_eq!(
+            after.actions,
+            Some(actions),
+            "Create/Cancel stay pinned during form scrolling"
+        );
+        assert_eq!(
+            after.scrolls[0].2.y, 180.,
+            "form scrolling does not move the diagram page"
+        );
+        assert!(
+            after
+                .scrolls
+                .iter()
+                .any(|s| s.0 == Some(widget::Id::new("process-form")) && s.2.y == 600.)
+        );
+        view = workspace(false);
+        tree.diff(view.as_widget());
+        let (_, closed) = geometry(&mut view, &mut tree, size);
+        assert_eq!(
+            closed.scrolls[0].2.y, 180.,
+            "cancel retains the page scroll"
+        );
+        assert_eq!(closed.scrolls[0].1.height, size.height);
+    }
+}
diff --git a/crates/oa-desktop/src/behavior/topology/view.rs b/crates/oa-desktop/src/behavior/topology/view.rs
index d2d7c917..96483d04 100644
--- a/crates/oa-desktop/src/behavior/topology/view.rs
+++ b/crates/oa-desktop/src/behavior/topology/view.rs
@@ -305,6 +305,7 @@ pub(super) fn view<'a>(
             button("Back to caller").on_press(Message::TopologyCanvas(CanvasEvent::Back(context))),
         );
     }
+    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) {
         let mut form = column![text(d.tool.title()).size(16)].spacing(8);
         if let Some(link) = d.insertion.link.and_then(|id| p.relations.get(&id)) {
@@ -473,21 +474,65 @@ pub(super) fn view<'a>(
             button("Cancel").on_press(event(Event::Cancel))
         ]
         .spacing(7);
-        out = out.push(
-            container(
-                column![
-                    actions,
-                    scrollable(form).height((app.window_size.height - 520.).clamp(150., 260.))
-                ]
-                .spacing(8),
-            )
-            .padding(12)
-            .style(style::card),
-        );
+        form_panel = editor_panel(actions.into(), form.into());
     }
-    super::super::scenario_scroll::observe_topology(
-        context,
-        scenario::ScrollArea::Page,
-        scrollable(out.padding(18)),
+    panes(
+        super::super::scenario_scroll::observe_topology(
+            context,
+            scenario::ScrollArea::Page,
+            scrollable(out.padding(18)),
+        ),
+        form_panel,
+        pending,
     )
 }
+
+/// Keep the diagram mounted while an independent editor uses the remaining
+/// workspace height. The editor must never be clipped by the page scrollable.
+fn panes<'a, R: iced::advanced::Renderer + 'a>(
+    diagram: iced::Element<'a, Message, iced::Theme, R>,
+    form: iced::Element<'a, Message, iced::Theme, R>,
+    pending: bool,
+) -> iced::Element<'a, Message, iced::Theme, R> {
+    column![
+        container(diagram).width(Fill).height(if pending {
+            iced::Length::FillPortion(1)
+        } else {
+            Fill
+        }),
+        container(form).width(Fill).height(if pending {
+            iced::Length::FillPortion(1)
+        } else {
+            iced::Length::Shrink
+        }),
+    ]
+    .width(Fill)
+    .height(Fill)
+    .into()
+}
+
+fn editor_panel<'a, R: iced::advanced::text::Renderer + 'a>(
+    actions: iced::Element<'a, Message, iced::Theme, R>,
+    fields: iced::Element<'a, Message, iced::Theme, R>,
+) -> iced::Element<'a, Message, iced::Theme, R> {
+    container(
+        container(column![actions, scrollable(fields).id("process-form").height(Fill)].spacing(8))
+            .width(Fill)
+            .height(Fill)
+            .padding(12)
+            .style(style::card),
+    )
+    .width(Fill)
+    .height(Fill)
+    .padding(iced::Padding {
+        top: 0.,
+        right: 18.,
+        bottom: 18.,
+        left: 18.,
+    })
+    .into()
+}
+
+#[cfg(all(test, debug_assertions))]
+#[path = "layout_tests.rs"]
+mod layout_tests;