diff --git a/docs/spec/07-implementation-phases-todo.md b/docs/spec/07-implementation-phases-todo.md
index 0859dee..b3d2c96 100644
--- a/docs/spec/07-implementation-phases-todo.md
+++ b/docs/spec/07-implementation-phases-todo.md
@@ -281,6 +281,13 @@ Tasks:
 - review sensible default columns and responsive behavior for typical browser widths
 - redesign column filtering with clearer controls, active-filter indicators and an easy reset action
 
+Implemented layout foundation:
+
+- table scrolling is contained inside the editor so sticky headers remain visible
+- the toolbar remains reachable while the page scrolls
+- programmatic grid focus preserves the viewport during undo/redo reloads
+- wide tables no longer expand the surrounding browser layout
+
 Acceptance criteria:
 
 - users retain column context anywhere in a long list
diff --git a/src/app/globals.css b/src/app/globals.css
index 8a71bb2..9038930 100644
--- a/src/app/globals.css
+++ b/src/app/globals.css
@@ -44,12 +44,19 @@ body {
   display: flex;
   flex-direction: column;
   gap: 0.75rem;
+  min-width: 0;
 }
 
 .editor-toolbar {
   display: flex;
+  flex-wrap: wrap;
   gap: 0.5rem;
-  position: relative;
+  position: sticky;
+  top: 0;
+  z-index: 12;
+  padding: 0.35rem 0;
+  background: #fff;
+  box-shadow: 0 1px 0 rgba(196, 205, 220, 0.8);
 }
 
 .editor-toolbar button {
@@ -137,13 +144,20 @@ body {
   overflow: auto;
   border: 1px solid #d9dee8;
   background: #fff;
+  width: 100%;
+  max-width: 100%;
+  min-width: 0;
+  max-height: max(28rem, calc(100vh - 12rem));
+  scrollbar-gutter: stable;
 }
 
 .tree-editor-layout {
   display: grid;
-  grid-template-columns: 320px 1fr;
+  grid-template-columns: minmax(240px, 320px) minmax(0, 1fr);
   gap: 0.75rem;
   min-height: 560px;
+  min-width: 0;
+  align-items: start;
 }
 
 .project-device-sidebar {
diff --git a/src/frontend/components/circuit-tree-editor.tsx b/src/frontend/components/circuit-tree-editor.tsx
index 33efa0a..b5a5927 100644
--- a/src/frontend/components/circuit-tree-editor.tsx
+++ b/src/frontend/components/circuit-tree-editor.tsx
@@ -482,7 +482,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
       setAnchorRowKey(null);
     }
     setSelectedCell({ rowKey: row.rowKey, cellKey });
-    requestAnimationFrame(() => containerRef.current?.focus());
+    focusGridWithoutScroll();
   }
 
   // Captures semantic identity for post-reload focus restoration.
@@ -556,7 +556,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
     }
     await loadTree({ showLoading: false });
     if (!intent) {
-      requestAnimationFrame(() => containerRef.current?.focus());
+      focusGridWithoutScroll();
     }
   }
 
@@ -779,7 +779,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
     if (resolved) {
       setSelectedCell(resolved);
     }
-    requestAnimationFrame(() => containerRef.current?.focus());
+    focusGridWithoutScroll();
   }, [data, editableCells, visibleRows]);
 
   // Restores multi-selected device rows after operations that rebuild row keys.
@@ -870,6 +870,10 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
     return row?.cells.find((cell) => cell.cellKey === cellKey);
   }
 
+  function focusGridWithoutScroll() {
+    requestAnimationFrame(() => containerRef.current?.focus({ preventScroll: true }));
+  }
+
   // Opens edit session for selected cell.
   // Enter/F2/double-click use selectExisting; type-to-edit uses replaceWithTypedChar.
   function startEdit(cell: SelectedCell, mode: StartEditMode, typedChar?: string) {
@@ -1169,7 +1173,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
     }
     setEditingCell(null);
     setSelectedCell({ rowKey: editingCell.rowKey, cellKey: editingCell.cellKey });
-    requestAnimationFrame(() => containerRef.current?.focus());
+    focusGridWithoutScroll();
   }
 
   async function handleAddReserveCircuit(sectionId: string, afterCircuitId?: string) {
@@ -3164,7 +3168,7 @@ export function CircuitTreeEditor(props: { projectId: string; circuitListId: str
                                 const active = document.activeElement as HTMLElement | null;
                                 if (!active || !containerRef.current?.contains(active)) {
                                   setEditingCell(null);
-                                  requestAnimationFrame(() => containerRef.current?.focus());
+                                  focusGridWithoutScroll();
                                 }
                               });
                             }}