feat: diff mode added

Author: KyleWMiller

understand-anything-plugin/packages/dashboard/src/App.tsx

@@ -6,6 +6,7 @@ import CodeViewer from "./components/CodeViewer";
 import SearchBar from "./components/SearchBar";
 import NodeInfo from "./components/NodeInfo";
 import LayerLegend from "./components/LayerLegend";
+import DiffToggle from "./components/DiffToggle";
 import LearnPanel from "./components/LearnPanel";
 import PersonaSelector from "./components/PersonaSelector";
 import ProjectOverview from "./components/ProjectOverview";
@@ -18,6 +19,7 @@ function App() {
   const persona = useDashboardStore((s) => s.persona);
   const codeViewerOpen = useDashboardStore((s) => s.codeViewerOpen);
   const closeCodeViewer = useDashboardStore((s) => s.closeCodeViewer);
+  const setDiffOverlay = useDashboardStore((s) => s.setDiffOverlay);
   const [loadError, setLoadError] = useState<string | null>(null);
 
   useEffect(() => {
@@ -39,6 +41,32 @@ function App() {
       });
   }, [setGraph]);
 
+  useEffect(() => {
+    fetch("/diff-overlay.json")
+      .then((res) => {
+        if (!res.ok) return null;
+        return res.json();
+      })
+      .then((data: unknown) => {
+        if (
+          data &&
+          typeof data === "object" &&
+          "changedNodeIds" in data &&
+          "affectedNodeIds" in data &&
+          Array.isArray((data as Record<string, unknown>).changedNodeIds) &&
+          Array.isArray((data as Record<string, unknown>).affectedNodeIds)
+        ) {
+          const d = data as { changedNodeIds: string[]; affectedNodeIds: string[] };
+          if (d.changedNodeIds.length > 0) {
+            setDiffOverlay(d.changedNodeIds, d.affectedNodeIds);
+          }
+        }
+      })
+      .catch(() => {
+        // Silently ignore - diff overlay is optional
+      });
+  }, [setDiffOverlay]);
+
   // Determine sidebar content
   // Learn persona always shows LearnPanel; tour active overrides everything
   const sidebarContent = tourActive || persona === "junior" ? (
@@ -61,6 +89,7 @@ function App() {
           <PersonaSelector />
         </div>
         <div className="flex items-center gap-4">
+          <DiffToggle />
           <LayerLegend />
         </div>
       </header>

understand-anything-plugin/packages/dashboard/src/components/CustomNode.tsx

@@ -32,6 +32,9 @@ export interface CustomNodeData extends Record<string, unknown> {
   searchScore?: number;
   isSelected: boolean;
   isTourHighlighted: boolean;
+  isDiffChanged: boolean;
+  isDiffAffected: boolean;
+  isDiffFaded: boolean;
   onNodeClick?: (nodeId: string) => void;
 }
 
@@ -61,6 +64,15 @@ export default function CustomNode({
     }
   }
 
+  // Diff overlay styling (composes with above)
+  if (data.isDiffChanged) {
+    extraClass += " ring-2 ring-[var(--color-diff-changed)] diff-changed-glow";
+  } else if (data.isDiffAffected) {
+    extraClass += " ring-1 ring-[var(--color-diff-affected)] diff-affected-glow";
+  } else if (data.isDiffFaded) {
+    extraClass += " diff-faded";
+  }
+
   const name = data.label ?? "unnamed";
   const truncatedName =
     name.length > 24 ? name.slice(0, 22) + "..." : name;

understand-anything-plugin/packages/dashboard/src/components/DiffToggle.tsx

@@ -0,0 +1,64 @@
+import { useDashboardStore } from "../store";
+
+export default function DiffToggle() {
+  const diffMode = useDashboardStore((s) => s.diffMode);
+  const toggleDiffMode = useDashboardStore((s) => s.toggleDiffMode);
+  const changedNodeIds = useDashboardStore((s) => s.changedNodeIds);
+  const affectedNodeIds = useDashboardStore((s) => s.affectedNodeIds);
+
+  const hasDiff = changedNodeIds.size > 0;
+
+  return (
+    <div className="flex items-center gap-2">
+      <button
+        onClick={toggleDiffMode}
+        disabled={!hasDiff}
+        className={`px-2 py-0.5 rounded text-[11px] font-medium transition-colors ${
+          diffMode && hasDiff
+            ? "bg-[var(--color-diff-changed-dim)] text-[var(--color-diff-changed)]"
+            : hasDiff
+              ? "bg-elevated text-text-secondary hover:bg-surface"
+              : "bg-elevated text-text-muted cursor-not-allowed"
+        }`}
+        title={
+          hasDiff
+            ? diffMode
+              ? "Hide diff overlay"
+              : "Show diff overlay"
+            : "No diff data loaded"
+        }
+      >
+        Diff {diffMode && hasDiff ? "ON" : "OFF"}
+      </button>
+
+      {diffMode && hasDiff && (
+        <div className="flex items-center gap-3">
+          <div className="flex items-center gap-1">
+            <span
+              className="inline-block w-2 h-2 rounded-full"
+              style={{ backgroundColor: "var(--color-diff-changed)" }}
+            />
+            <span className="text-text-secondary text-[11px]">
+              Changed
+              <span className="text-text-muted ml-0.5">
+                ({changedNodeIds.size})
+              </span>
+            </span>
+          </div>
+          <div className="flex items-center gap-1">
+            <span
+              className="inline-block w-2 h-2 rounded-full"
+              style={{ backgroundColor: "var(--color-diff-affected)" }}
+            />
+            <span className="text-text-secondary text-[11px]">
+              Affected
+              <span className="text-text-muted ml-0.5">
+                ({affectedNodeIds.size})
+              </span>
+            </span>
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}

understand-anything-plugin/packages/dashboard/src/components/GraphView.tsx

@@ -30,6 +30,9 @@ export default function GraphView() {
   const showLayers = useDashboardStore((s) => s.showLayers);
   const tourHighlightedNodeIds = useDashboardStore((s) => s.tourHighlightedNodeIds);
   const persona = useDashboardStore((s) => s.persona);
+  const diffMode = useDashboardStore((s) => s.diffMode);
+  const changedNodeIds = useDashboardStore((s) => s.changedNodeIds);
+  const affectedNodeIds = useDashboardStore((s) => s.affectedNodeIds);
 
   const handleNodeSelect = useCallback(
     (nodeId: string) => {
@@ -78,20 +81,41 @@ export default function GraphView() {
           searchScore: matchResult?.score,
           isSelected: selectedNodeId === node.id,
           isTourHighlighted: tourHighlightedNodeIds.includes(node.id),
+          isDiffChanged: diffMode && changedNodeIds.has(node.id),
+          isDiffAffected: diffMode && affectedNodeIds.has(node.id),
+          isDiffFaded: diffMode && !changedNodeIds.has(node.id) && !affectedNodeIds.has(node.id),
           onNodeClick: handleNodeSelect,
         },
       };
     });
 
-    const flowEdges: Edge[] = filteredGraphEdges.map((edge, i) => ({
-      id: `e-${i}`,
-      source: edge.source,
-      target: edge.target,
-      label: edge.type,
-      animated: edge.type === "calls",
-      style: { stroke: "rgba(212,165,116,0.3)", strokeWidth: 1.5 },
-      labelStyle: { fill: "#a39787", fontSize: 10 },
-    }));
+    const diffNodeIds = new Set([...changedNodeIds, ...affectedNodeIds]);
+    const flowEdges: Edge[] = filteredGraphEdges.map((edge, i) => {
+      const sourceInDiff = diffNodeIds.has(edge.source);
+      const targetInDiff = diffNodeIds.has(edge.target);
+      const isImpacted = diffMode && (sourceInDiff || targetInDiff);
+
+      return {
+        id: `e-${i}`,
+        source: edge.source,
+        target: edge.target,
+        label: edge.type,
+        animated: edge.type === "calls" || isImpacted,
+        style: isImpacted
+          ? {
+              stroke: sourceInDiff && targetInDiff
+                ? "rgba(224, 82, 82, 0.7)"
+                : "rgba(212, 160, 48, 0.5)",
+              strokeWidth: 2.5,
+            }
+          : diffMode
+            ? { stroke: "rgba(212,165,116,0.08)", strokeWidth: 1 }
+            : { stroke: "rgba(212,165,116,0.3)", strokeWidth: 1.5 },
+        labelStyle: diffMode && !isImpacted
+          ? { fill: "rgba(163,151,135,0.3)", fontSize: 10 }
+          : { fill: "#a39787", fontSize: 10 },
+      };
+    });
 
     // Run dagre layout on all nodes (without groups)
     const laid = applyDagreLayout(flowNodes, flowEdges);
@@ -190,7 +214,7 @@ export default function GraphView() {
     ];
 
     return { initialNodes: allNodes, initialEdges: laid.edges };
-  }, [graph, searchResults, selectedNodeId, showLayers, tourHighlightedNodeIds, persona, handleNodeSelect]);
+  }, [graph, searchResults, selectedNodeId, showLayers, tourHighlightedNodeIds, persona, handleNodeSelect, diffMode, changedNodeIds, affectedNodeIds]);
 
   const [nodes, setNodes, onNodesChange] = useNodesState(initialNodes);
   const [edges, setEdges, onEdgesChange] = useEdgesState(initialEdges);

understand-anything-plugin/packages/dashboard/src/index.css

@@ -28,6 +28,12 @@
   --color-node-module: #c9a06c;
   --color-node-concept: #b07a8a;
 
+  /* Diff overlay colors */
+  --color-diff-changed: #e05252;
+  --color-diff-affected: #d4a030;
+  --color-diff-changed-dim: rgba(224, 82, 82, 0.25);
+  --color-diff-affected-dim: rgba(212, 160, 48, 0.25);
+
   /* Fonts */
   --font-serif: 'DM Serif Display', Georgia, serif;
   --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
@@ -113,6 +119,22 @@ body {
   box-shadow: 0 0 20px rgba(212, 165, 116, 0.15);
 }
 
+/* Diff overlay glow effects */
+.diff-changed-glow {
+  box-shadow: 0 0 16px rgba(224, 82, 82, 0.25);
+}
+
+.diff-affected-glow {
+  box-shadow: 0 0 12px rgba(212, 160, 48, 0.2);
+}
+
+/* Diff fade for unrelated nodes */
+.diff-faded {
+  opacity: 0.25;
+  filter: saturate(0.3);
+  transition: opacity 0.3s ease, filter 0.3s ease;
+}
+
 /* Custom scrollbar for dark luxury theme */
 ::-webkit-scrollbar {
   width: 6px;

understand-anything-plugin/packages/dashboard/src/store.ts

@@ -28,6 +28,10 @@ interface DashboardStore {
 
   persona: Persona;
 
+  diffMode: boolean;
+  changedNodeIds: Set<string>;
+  affectedNodeIds: Set<string>;
+
   setGraph: (graph: KnowledgeGraph) => void;
   selectNode: (nodeId: string | null) => void;
   setSearchQuery: (query: string) => void;
@@ -36,6 +40,10 @@ interface DashboardStore {
   openCodeViewer: (nodeId: string) => void;
   closeCodeViewer: () => void;
 
+  setDiffOverlay: (changed: string[], affected: string[]) => void;
+  toggleDiffMode: () => void;
+  clearDiffOverlay: () => void;
+
   startTour: () => void;
   stopTour: () => void;
   setTourStep: (step: number) => void;
@@ -67,6 +75,10 @@ export const useDashboardStore = create<DashboardStore>()((set, get) => ({
 
   persona: "junior",
 
+  diffMode: false,
+  changedNodeIds: new Set<string>(),
+  affectedNodeIds: new Set<string>(),
+
   setGraph: (graph) => {
     const searchEngine = new SearchEngine(graph.nodes);
     const query = get().searchQuery;
@@ -96,6 +108,22 @@ export const useDashboardStore = create<DashboardStore>()((set, get) => ({
   openCodeViewer: (nodeId) => set({ codeViewerOpen: true, codeViewerNodeId: nodeId }),
   closeCodeViewer: () => set({ codeViewerOpen: false, codeViewerNodeId: null }),
 
+  setDiffOverlay: (changed, affected) =>
+    set({
+      diffMode: true,
+      changedNodeIds: new Set(changed),
+      affectedNodeIds: new Set(affected),
+    }),
+
+  toggleDiffMode: () => set((state) => ({ diffMode: !state.diffMode })),
+
+  clearDiffOverlay: () =>
+    set({
+      diffMode: false,
+      changedNodeIds: new Set<string>(),
+      affectedNodeIds: new Set<string>(),
+    }),
+
   startTour: () => {
     const { graph } = get();
     if (!graph || !graph.tour || graph.tour.length === 0) return;

understand-anything-plugin/packages/dashboard/vite.config.ts

@@ -38,6 +38,26 @@ export default defineConfig({
               }
             }
           }
+          if (req.url === "/diff-overlay.json") {
+            const graphDir = process.env.GRAPH_DIR;
+            const candidates = [
+              ...(graphDir
+                ? [path.resolve(graphDir, ".understand-anything/diff-overlay.json")]
+                : []),
+              path.resolve(process.cwd(), ".understand-anything/diff-overlay.json"),
+              path.resolve(process.cwd(), "../../../.understand-anything/diff-overlay.json"),
+            ];
+            for (const candidate of candidates) {
+              if (fs.existsSync(candidate)) {
+                res.setHeader("Content-Type", "application/json");
+                fs.createReadStream(candidate).pipe(res);
+                return;
+              }
+            }
+            res.statusCode = 404;
+            res.end();
+            return;
+          }
           next();
         });
       },

understand-anything-plugin/skills/understand-diff/SKILL.md

@@ -55,3 +55,16 @@ The knowledge graph JSON has this structure:
    - **Affected Layers**: Which architectural layers are touched and cross-layer concerns
    - **Risk Assessment**: Based on node `complexity` values, number of cross-layer edges, and blast radius (number of affected components)
    - Suggest what to review carefully and any potential issues
+
+8. **Write diff overlay for dashboard** — after producing the analysis, write the diff data to `.understand-anything/diff-overlay.json` so the dashboard can visualize changed and affected components. The file contains:
+   ```json
+   {
+     "version": "1.0.0",
+     "baseBranch": "<the base branch used>",
+     "generatedAt": "<ISO timestamp>",
+     "changedFiles": ["<list of changed file paths>"],
+     "changedNodeIds": ["<node IDs from step 4>"],
+     "affectedNodeIds": ["<node IDs from step 5, excluding changedNodeIds>"]
+   }
+   ```
+   After writing, tell the user they can run `/understand-anything:understand-dashboard` to see the diff overlay visually.