diff --git a/frontend/src/app/canvas/CanvasPage.tsx b/frontend/src/app/canvas/CanvasPage.tsx
index 4722eb2..216a0e6 100644
--- a/frontend/src/app/canvas/CanvasPage.tsx
+++ b/frontend/src/app/canvas/CanvasPage.tsx
@@ -66,6 +66,7 @@ import {
   getNodeType,
   isConnectionAllowed,
 } from '@/lib/nodeRegistry'
+import { getPathNodeIds } from '@/lib/graphPath'
 import type { AppNode, AppEdge } from '@/lib/nodeTypes'
 import { toast } from 'sonner'
 import {
@@ -77,6 +78,8 @@ import {
 
 const SNAP_GRID: [number, number] = [15, 15]
 const DUPLICATE_OFFSET = { x: 30, y: 30 }
+/** Minimum time (ms) the connection ant trail runs when a path update is in progress. */
+const CONNECTION_PATH_UPDATE_MIN_MS = 1500
 const snapToGrid = (x: number, y: number): { x: number; y: number } => ({
   x: Math.round(x / SNAP_GRID[0]) * SNAP_GRID[0],
   y: Math.round(y / SNAP_GRID[1]) * SNAP_GRID[1],
@@ -264,6 +267,75 @@ export function CanvasPage({ projectId }: CanvasPageProps) {
   const [isSelecting, setIsSelecting] = React.useState(false)
   const [ariaAnnouncement, setAriaAnnouncement] = React.useState<string | null>(null)
   const [fullscreenNodeId, setFullscreenNodeId] = React.useState<string | null>(null)
+  const [connectionPathUpdatingNodeIds, setConnectionPathUpdatingNodeIds] = React.useState<string[]>([])
+  const [connectionPathTriggerNodeIds, setConnectionPathTriggerNodeIds] = React.useState<string[]>([])
+  const pathUpdateNodeIdsRef = useRef<Set<string>>(new Set())
+  const pathUpdateStartTimeRef = useRef<number | null>(null)
+  const pathUpdateEndTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+
+  const clearPathUpdateSession = useCallback(() => {
+    setConnectionPathUpdatingNodeIds([])
+    setConnectionPathTriggerNodeIds([])
+  }, [])
+
+  const startConnectionPathUpdate = useCallback((nodeId: string) => {
+    const ref = pathUpdateNodeIdsRef.current
+    ref.add(nodeId)
+    if (ref.size === 1) {
+      pathUpdateStartTimeRef.current = Date.now()
+      if (pathUpdateEndTimeoutRef.current != null) {
+        clearTimeout(pathUpdateEndTimeoutRef.current)
+        pathUpdateEndTimeoutRef.current = null
+      }
+    }
+    setConnectionPathUpdatingNodeIds(Array.from(ref))
+  }, [])
+
+  const endConnectionPathUpdate = useCallback((nodeId: string) => {
+    const ref = pathUpdateNodeIdsRef.current
+    ref.delete(nodeId)
+    if (ref.size > 0) {
+      setConnectionPathUpdatingNodeIds(Array.from(ref))
+      return
+    }
+    const startedAt = pathUpdateStartTimeRef.current ?? 0
+    const elapsed = Date.now() - startedAt
+    const remaining = Math.max(0, CONNECTION_PATH_UPDATE_MIN_MS - elapsed)
+    if (remaining === 0) {
+      clearPathUpdateSession()
+    } else {
+      pathUpdateEndTimeoutRef.current = setTimeout(() => {
+        pathUpdateEndTimeoutRef.current = null
+        clearPathUpdateSession()
+      }, remaining)
+    }
+  }, [clearPathUpdateSession])
+
+  const pathTriggerBatchRef = useRef<Set<string>>(new Set())
+  const pathTriggerScheduledRef = useRef(false)
+  const addConnectionPathTrigger = useCallback((nodeId: string) => {
+    pathTriggerBatchRef.current.add(nodeId)
+    if (pathTriggerScheduledRef.current) return
+    pathTriggerScheduledRef.current = true
+    requestAnimationFrame(() => {
+      pathTriggerScheduledRef.current = false
+      const batch = new Set(pathTriggerBatchRef.current)
+      pathTriggerBatchRef.current = new Set()
+      if (batch.size === 0) return
+      setConnectionPathTriggerNodeIds((prev) => {
+        const next = new Set(prev)
+        batch.forEach((id) => next.add(id))
+        return next.size === prev.length && prev.every((id) => next.has(id)) ? prev : Array.from(next)
+      })
+    })
+  }, [])
+
+  React.useEffect(() => () => {
+    if (pathUpdateEndTimeoutRef.current != null) {
+      clearTimeout(pathUpdateEndTimeoutRef.current)
+    }
+  }, [])
+
   const nodesRef = useRef(nodes)
   nodesRef.current = nodes
 
@@ -471,6 +543,11 @@ export function CanvasPage({ projectId }: CanvasPageProps) {
     flowActionsRef.current?.pasteAtViewportCenter?.()
   }, [])
 
+  const connectionPathNodeIds = useMemo(
+    () => getPathNodeIds(edges, connectionPathUpdatingNodeIds, connectionPathTriggerNodeIds),
+    [edges, connectionPathUpdatingNodeIds, connectionPathTriggerNodeIds]
+  )
+
   const flowContextValue = useMemo(
     () => ({
       nodes,
@@ -485,6 +562,12 @@ export function CanvasPage({ projectId }: CanvasPageProps) {
       flowActionsRef,
       fullscreenNodeId,
       setFullscreenNodeId,
+      connectionPathUpdatingNodeIds,
+      connectionPathTriggerNodeIds,
+      addConnectionPathTrigger,
+      connectionPathNodeIds,
+      startConnectionPathUpdate,
+      endConnectionPathUpdate,
     }),
     [
       nodes,
@@ -499,6 +582,12 @@ export function CanvasPage({ projectId }: CanvasPageProps) {
       flowActionsRef,
       fullscreenNodeId,
       setFullscreenNodeId,
+      connectionPathUpdatingNodeIds,
+      connectionPathTriggerNodeIds,
+      addConnectionPathTrigger,
+      connectionPathNodeIds,
+      startConnectionPathUpdate,
+      endConnectionPathUpdate,
     ]
   )
 
diff --git a/frontend/src/app/canvas/ContextualZoomNode.tsx b/frontend/src/app/canvas/ContextualZoomNode.tsx
index 0b9a6f8..558b2ee 100644
--- a/frontend/src/app/canvas/ContextualZoomNode.tsx
+++ b/frontend/src/app/canvas/ContextualZoomNode.tsx
@@ -79,6 +79,8 @@ function CompactNodeView({ id, type, selected, width, height }: NodeProps) {
 /**
  * Wraps a node component so that when the viewport zoom is at or below
  * CONTEXTUAL_ZOOM_THRESHOLD, the node renders as a compact icon-only view.
+ * Inner is always mounted (hidden when compact) so switching zoom does not
+ * remount and re-trigger effects (e.g. RenderingNode fetch).
  */
 export function createContextualNode<P extends NodeProps>(
   Inner: React.ComponentType<P>
@@ -86,22 +88,35 @@ export function createContextualNode<P extends NodeProps>(
   function ContextualZoomNode(props: P) {
     const { zoom } = useViewport()
     const showCompact = zoom <= CONTEXTUAL_ZOOM_THRESHOLD
+    const p = props as NodeProps
+    const type = p.type
+    const defaultStyle = type ? getDefaultStyle(type) : { width: 320, height: 320 }
+    const w = p.width ?? defaultStyle.width
+    const h = p.height ?? defaultStyle.height
 
-    if (showCompact) {
-      const p = props as NodeProps
-      return (
-        <CompactNodeView
-          id={p.id}
-          type={p.type}
-          data={p.data}
-          selected={p.selected}
-          width={p.width}
-          height={p.height}
-        />
-      )
-    }
-
-    return <Inner {...props} />
+    return (
+      <div
+        style={
+          showCompact
+            ? { width: w, height: h, minWidth: w, minHeight: h, position: 'relative' }
+            : { display: 'contents' }
+        }
+      >
+        {showCompact && (
+          <CompactNodeView
+            id={p.id}
+            type={type}
+            data={p.data}
+            selected={p.selected}
+            width={p.width}
+            height={p.height}
+          />
+        )}
+        <div style={{ display: showCompact ? 'none' : undefined }} aria-hidden={showCompact}>
+          <Inner {...props} />
+        </div>
+      </div>
+    )
   }
 
   ContextualZoomNode.displayName = `ContextualZoom(${Inner.displayName ?? Inner.name ?? 'Node'})`
diff --git a/frontend/src/components/base/AnimatedEdge.tsx b/frontend/src/components/base/AnimatedEdge.tsx
index 67b6bbc..665484b 100644
--- a/frontend/src/components/base/AnimatedEdge.tsx
+++ b/frontend/src/components/base/AnimatedEdge.tsx
@@ -9,9 +9,11 @@ import { getConnectionLabelForTarget } from '../../lib/nodeRegistry'
 
 const EDGE_STROKE_WIDTH = 2
 const DOT_MARKER_R = 1.5
+const EMPTY_PATH_NODE_IDS = new Set<string>()
 
 export function AnimatedEdge({
   id,
+  source,
   sourceX,
   sourceY,
   targetX,
@@ -25,6 +27,7 @@ export function AnimatedEdge({
 }: EdgeProps) {
   const ctx = useContext(FlowContext)
   const nodes = ctx?.nodes ?? []
+  const pathNodeIds = ctx?.connectionPathNodeIds ?? EMPTY_PATH_NODE_IDS
   const targetNode = useMemo(() => nodes.find((n: any) => n.id === target), [nodes, target])
   const derivedLabel = useMemo(
     () => (targetNode?.type != null ? getConnectionLabelForTarget(targetNode.type) : undefined),
@@ -32,6 +35,8 @@ export function AnimatedEdge({
   )
   const label = labelProp ?? derivedLabel
 
+  const isOnUpdatingPath = pathNodeIds.has(source) && pathNodeIds.has(target)
+
   const [edgePath, edgeLabelX, edgeLabelY] = getBezierPath({
     sourceX,
     sourceY,
@@ -88,7 +93,7 @@ export function AnimatedEdge({
           strokeWidth: EDGE_STROKE_WIDTH,
           ...style,
         }}
-        className="animated-edge-path"
+        className={`animated-edge-path${isOnUpdatingPath ? ' animated-edge-path--updating' : ''}`}
         interactionWidth={interactionWidth}
       />
       {label != null && (
diff --git a/frontend/src/components/base/BaseNode.tsx b/frontend/src/components/base/BaseNode.tsx
index ff070ef..602a1d7 100644
--- a/frontend/src/components/base/BaseNode.tsx
+++ b/frontend/src/components/base/BaseNode.tsx
@@ -1,6 +1,7 @@
 import type { ComponentProps, ReactNode } from "react";
 import { NodeResizer } from "@xyflow/react";
 
+import { useConnectionPathRole } from "@/lib/flowContext";
 import { cn } from "@/lib/utils";
 
 /** Default min size for resizable nodes (used by NodeResizer). */
@@ -34,6 +35,7 @@ export function BaseNode({
   resizeConstraints,
   ...props
 }: BaseNodeProps) {
+  const connectionPathRole = useConnectionPathRole(nodeId);
   const hasSize =
     dimensions &&
     dimensions.width > 0 &&
@@ -62,9 +64,13 @@ export function BaseNode({
         "bg-card text-card-foreground relative rounded-md border transition-[border-color,box-shadow] duration-200",
         "hover:ring-1",
         selected && "border-primary/50 shadow-[0_0_0_2px_hsl(var(--primary)_/_0.15)] dark:border-primary/35 dark:shadow-[0_0_0_2px_hsl(var(--primary)_/_0.1)]",
+        connectionPathRole === "trigger" && "connection-path-trigger",
+        connectionPathRole === "updating" && "connection-path-updating",
+        connectionPathRole === "on-path" && "connection-path-on-path",
         className,
       )}
       data-selected={selected}
+      data-path-role={connectionPathRole ?? undefined}
       style={appliedStyle}
       tabIndex={0}
       {...props}
diff --git a/frontend/src/components/nodes/AgentNode.tsx b/frontend/src/components/nodes/AgentNode.tsx
index 2da9ebe..b64b3e0 100644
--- a/frontend/src/components/nodes/AgentNode.tsx
+++ b/frontend/src/components/nodes/AgentNode.tsx
@@ -55,6 +55,8 @@ function serializeNodeForContext(nodes: { id: string; type?: string; data?: unkn
 function AgentNodeComponent({ id, data, width, height, selected }: Props) {
   const flowContext = useContext(FlowContext)
   const setFullscreenNodeId = flowContext?.setFullscreenNodeId
+  const startConnectionPathUpdate = flowContext?.startConnectionPathUpdate
+  const endConnectionPathUpdate = flowContext?.endConnectionPathUpdate
   const supportsFullscreen = getNodeType('agent')?.supportsFullscreen
   const { nodes, sourceIds, updateData } = useAbstractNode<AgentNodeData>(id, data ?? {})
   const { aiConnection } = usePlatform()
@@ -88,6 +90,7 @@ function AgentNodeComponent({ id, data, width, height, selected }: Props) {
     const contextNodes = sourceIds.map((sid) => ({ id: sid, content: serializeNodeForContext(nodes, sid) }))
 
     updateData({ error: undefined, loading: true })
+    startConnectionPathUpdate?.(id)
     setRunning(true)
     try {
       const res = await fetch('/api/agent', {
@@ -107,16 +110,19 @@ function AgentNodeComponent({ id, data, width, height, selected }: Props) {
           error: (json as { error?: string }).error ?? `Request failed: ${res.status}`,
           outputMarkdown: undefined,
         })
+        endConnectionPathUpdate?.(id)
         return
       }
       const markdown = (json as { markdown?: string }).markdown ?? ''
       updateData({ loading: false, error: undefined, outputMarkdown: markdown })
+      endConnectionPathUpdate?.(id)
     } catch (err: unknown) {
       updateData({
         loading: false,
         error: err instanceof Error ? err.message : 'Agent request failed',
         outputMarkdown: undefined,
       })
+      endConnectionPathUpdate?.(id)
     } finally {
       setRunning(false)
     }
@@ -131,6 +137,7 @@ function AgentNodeComponent({ id, data, width, height, selected }: Props) {
     <BaseNode
       className="min-w-[360px] min-h-[320px]"
       dimensions={dimensions}
+      nodeId={id}
       selected={selected}
       handles={
         <>
diff --git a/frontend/src/components/nodes/RenderingNode.tsx b/frontend/src/components/nodes/RenderingNode.tsx
index 474ff26..2d04466 100644
--- a/frontend/src/components/nodes/RenderingNode.tsx
+++ b/frontend/src/components/nodes/RenderingNode.tsx
@@ -50,6 +50,8 @@ type ViewMode = 'preview' | 'raw'
 function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
     const flowContext = useContext(FlowContext)
     const setFullscreenNodeId = flowContext?.setFullscreenNodeId
+    const startConnectionPathUpdate = flowContext?.startConnectionPathUpdate
+    const endConnectionPathUpdate = flowContext?.endConnectionPathUpdate
     const supportsFullscreen = getNodeType('render')?.supportsFullscreen
     const [renderedContent, setRenderedContent] = useState<string | null>(null)
     const [resolvedContent, setResolvedContent] = useState<string | null>(null)
@@ -61,6 +63,7 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
     const runIdRef = useRef(0)
     const loadingStartedAtRef = useRef<number | null>(null)
     const minLoadingTimeoutRef = useRef<ReturnType<typeof setTimeout> | null>(null)
+    const isInitialRunRef = useRef(true)
     const { nodes, edges, setNodes, setEdges, sourceIds, updateData } = useAbstractNode<RenderingNodeData>(id, data ?? {})
     const viewportWidth = data?.viewportWidth ?? DEFAULT_VIEWPORT_WIDTH
     const viewportHeight = data?.viewportHeight ?? DEFAULT_VIEWPORT_HEIGHT
@@ -195,6 +198,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                 message: isAgentSource ? 'Run the Agent node to generate output.' : 'No content on connected configuration node',
             })
             setLoading(false)
+            if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+            isInitialRunRef.current = false
             return
         }
         if (incomingIds.length === 0) {
@@ -202,6 +207,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
             setResolvedContent(null)
             setError(null)
             setLoading(false)
+            if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+            isInitialRunRef.current = false
             return
         }
 
@@ -212,6 +219,7 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
         const run = async () => {
             loadingStartedAtRef.current = Date.now()
             setLoading(true)
+            if (!isInitialRunRef.current) startConnectionPathUpdate?.(id)
             setError(null)
             try {
                 if (srcNode?.type === 'agent') {
@@ -223,6 +231,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                     setRenderedContent(html)
                     setError(null)
                     setLoading(false)
+                    if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+                    isInitialRunRef.current = false
                     return
                 }
                 const configIdsUsed = new Set<string>()
@@ -497,6 +507,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                         setResolvedContent(null)
                         setError({ kind: 'render', message: `Nunjucks: ${nunjucksErr.message}` })
                         setLoading(false)
+                        if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+                        isInitialRunRef.current = false
                         return
                     }
 
@@ -524,10 +536,16 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                             if (remaining > 0) {
                                 minLoadingTimeoutRef.current = setTimeout(() => {
                                     minLoadingTimeoutRef.current = null
-                                    if (!cancelled && thisRunId === runIdRef.current) setLoading(false)
+                                    if (!cancelled && thisRunId === runIdRef.current) {
+                                        setLoading(false)
+                                        if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+                                        isInitialRunRef.current = false
+                                    }
                                 }, remaining)
                             } else {
                                 setLoading(false)
+                                if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+                                isInitialRunRef.current = false
                             }
                         }
                     }
@@ -537,6 +555,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                     setRenderedContent(null)
                     setError({ kind: 'render', message: err?.message ?? 'Render error' })
                     setLoading(false)
+                    if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+                    isInitialRunRef.current = false
                 }
             }
         }
@@ -549,6 +569,8 @@ function RenderingNodeComponent({ id, data, width, height, selected }: Props) {
                 clearTimeout(minLoadingTimeoutRef.current)
                 minLoadingTimeoutRef.current = null
             }
+            if (!isInitialRunRef.current) endConnectionPathUpdate?.(id)
+            isInitialRunRef.current = false
         }
         // Only re-run when inputs that affect the resolved output change (signatures + source). Debounced to avoid excessive re-renders while typing. retryCount triggers re-run on Retry.
     }, [id, sourceContent, configTypeId, configSignature, edgesSignature, variablesSignature, functionsSignature, dataSignature, viewportWidth, viewportHeight, retryCount, isAgentSource])
diff --git a/frontend/src/components/nodes/VariableNode.tsx b/frontend/src/components/nodes/VariableNode.tsx
index a9fc806..ff6d9d0 100644
--- a/frontend/src/components/nodes/VariableNode.tsx
+++ b/frontend/src/components/nodes/VariableNode.tsx
@@ -84,7 +84,7 @@ function VariableNodeComponent({ id, data, width, height, selected }: Props) {
     )
 
     return (
-        <BaseNode className="min-w-56 min-h-[180px]" dimensions={dimensions} selected={selected} handles={<OutputHandle id="out" />}>
+        <BaseNode className="min-w-56 min-h-[180px]" dimensions={dimensions} nodeId={id} selected={selected} handles={<OutputHandle id="out" />}>
             <BaseNodeHeaderRow icon={<Variable className="size-4" />} title={<NodeHeaderTitle nodeId={id} displayTitle={id} />} />
 
             <BaseNodeContent>
diff --git a/frontend/src/lib/abstractNode.ts b/frontend/src/lib/abstractNode.ts
index c2a85a2..894ea69 100644
--- a/frontend/src/lib/abstractNode.ts
+++ b/frontend/src/lib/abstractNode.ts
@@ -72,6 +72,7 @@ export function useAbstractNode<TData = Record<string, unknown>>(
   const setNodes = ctx?.setNodes
   const setEdges = ctx?.setEdges
 
+  const addConnectionPathTrigger = ctx?.addConnectionPathTrigger
   const updateData = useCallback(
     (partial: Partial<TData>) => {
       if (!setNodes) return
@@ -80,8 +81,9 @@ export function useAbstractNode<TData = Record<string, unknown>>(
           n.id === id ? { ...n, data: { ...(n.data as object), ...partial } } : n
         ) as AppNode[]
       )
+      addConnectionPathTrigger?.(id)
     },
-    [id, setNodes]
+    [id, setNodes, addConnectionPathTrigger]
   )
 
   const incomingEdges = useMemo(
diff --git a/frontend/src/lib/flowContext.tsx b/frontend/src/lib/flowContext.tsx
index 5777fbc..2038e21 100644
--- a/frontend/src/lib/flowContext.tsx
+++ b/frontend/src/lib/flowContext.tsx
@@ -1,9 +1,12 @@
-import React from 'react'
+import React, { useMemo } from 'react'
 import type { Connection } from '@xyflow/react'
 import type { AppNode, AppEdge } from '@/lib/nodeTypes'
 
 export type ConnectionFrom = { nodeId: string; sourceHandle?: string } | null
 
+/** Role of a node in the current connection path update: pushing data, receiving/loading, or just on path. */
+export type ConnectionPathRole = 'trigger' | 'updating' | 'on-path'
+
 export type FlowActions = {
     pasteAtViewportCenter: () => void
     fitView: () => void
@@ -25,8 +28,38 @@ export type FlowContextValue = {
     /** When set, graph centers on this node and a fullscreen dialog shows the node. Cleared on close. */
     fullscreenNodeId: string | null
     setFullscreenNodeId: (id: string | null) => void
+    /** Node ids currently updating (e.g. render loading, agent running). Only edges on those paths show the ant trail. */
+    connectionPathUpdatingNodeIds: string[]
+    /** Node ids that triggered the current update (e.g. variable/config that changed). Path is restricted to downstream(trigger) ∩ upstream(updating). */
+    connectionPathTriggerNodeIds: string[]
+    /** Call when this node's output changed and may trigger downstream updates (e.g. variable value, config content). */
+    addConnectionPathTrigger: (nodeId: string) => void
+    /** All node ids on the path of an update. Edges with both endpoints in this set animate. */
+    connectionPathNodeIds: Set<string>
+    /** Call when a path update starts for this node. Animation runs at least CONNECTION_PATH_UPDATE_MIN_MS. */
+    startConnectionPathUpdate: (nodeId: string) => void
+    /** Call when a path update ends for this node. If min duration not reached, animation continues until then. */
+    endConnectionPathUpdate: (nodeId: string) => void
 }
 
 const FlowContext = React.createContext<FlowContextValue | null>(null)
 
 export default FlowContext
+
+/**
+ * Returns this node's role in the current path update for styling (pushing vs receiving).
+ * Use with BaseNode's connectionPathRole prop or data-path-role for CSS.
+ */
+export function useConnectionPathRole(nodeId: string | undefined): ConnectionPathRole | null {
+  const ctx = React.useContext(FlowContext)
+  return useMemo(() => {
+    if (!nodeId) return null
+    const triggers = ctx?.connectionPathTriggerNodeIds
+    const updating = ctx?.connectionPathUpdatingNodeIds
+    const path = ctx?.connectionPathNodeIds
+    if (!path?.has(nodeId)) return null
+    if (triggers?.includes(nodeId)) return 'trigger'
+    if (updating?.includes(nodeId)) return 'updating'
+    return 'on-path'
+  }, [nodeId, ctx?.connectionPathTriggerNodeIds, ctx?.connectionPathUpdatingNodeIds, ctx?.connectionPathNodeIds])
+}
diff --git a/frontend/src/lib/graphPath.ts b/frontend/src/lib/graphPath.ts
new file mode 100644
index 0000000..6ebffe3
--- /dev/null
+++ b/frontend/src/lib/graphPath.ts
@@ -0,0 +1,67 @@
+/**
+ * Graph path utilities: compute which nodes/edges are "on the path" of an update.
+ * Used to show connection ant trail only along the full chain (upstream → updating → downstream).
+ * Works with any node types; any node can signal it is updating via startConnectionPathUpdate(id).
+ */
+
+export type GraphEdge = { source: string; target: string }
+
+/** Nodes reachable from seedIds by following edges forward (source → target). */
+export function getDownstreamNodeIds(edges: GraphEdge[], seedIds: string[]): Set<string> {
+  const out = new Set<string>(seedIds)
+  let added = true
+  while (added) {
+    added = false
+    for (const e of edges) {
+      if (out.has(e.source) && !out.has(e.target)) {
+        out.add(e.target)
+        added = true
+      }
+    }
+  }
+  return out
+}
+
+/** Nodes that can reach any seed by following edges backward (target → source). */
+export function getUpstreamNodeIds(edges: GraphEdge[], seedIds: string[]): Set<string> {
+  const out = new Set<string>(seedIds)
+  let added = true
+  while (added) {
+    added = false
+    for (const e of edges) {
+      if (out.has(e.target) && !out.has(e.source)) {
+        out.add(e.source)
+        added = true
+      }
+    }
+  }
+  return out
+}
+
+/**
+ * All node ids that lie on the path of an update.
+ * - If triggerNodeIds is non-empty: path = nodes that are both downstream of a trigger and
+ *   upstream of an updating node (only the chain that actually triggered the update).
+ * - Otherwise: path = upstream ∪ updating ∪ downstream of updating (legacy full upstream/downstream).
+ * An edge should show the update animation iff both its source and target are in this set.
+ */
+export function getPathNodeIds(
+  edges: GraphEdge[],
+  updatingNodeIds: string[],
+  triggerNodeIds?: string[]
+): Set<string> {
+  if (updatingNodeIds.length === 0) return new Set()
+  const upstream = getUpstreamNodeIds(edges, updatingNodeIds)
+  if (triggerNodeIds != null && triggerNodeIds.length > 0) {
+    const downstreamOfTrigger = getDownstreamNodeIds(edges, triggerNodeIds)
+    const path = new Set<string>()
+    upstream.forEach((id) => {
+      if (downstreamOfTrigger.has(id)) path.add(id)
+    })
+    return path
+  }
+  const downstream = getDownstreamNodeIds(edges, updatingNodeIds)
+  const path = new Set<string>(upstream)
+  downstream.forEach((id) => path.add(id))
+  return path
+}
diff --git a/frontend/src/styles.css b/frontend/src/styles.css
index 5dc2a2a..c2289ca 100644
--- a/frontend/src/styles.css
+++ b/frontend/src/styles.css
@@ -24,9 +24,11 @@ body {
 .react-flow__pane {
     cursor: crosshair;
 }
+
 .react-flow.react-flow--panning .react-flow__pane {
     cursor: grabbing;
 }
+
 .react-flow.react-flow--selecting .react-flow__pane {
     cursor: crosshair;
 }
@@ -133,26 +135,43 @@ body {
     min-height: min-content;
 }
 
-/* Animated React Flow edges: thicker stroke + path animation */
+/* Animated React Flow edges: ant trail always on; color shows updating path */
 .react-flow__edge path.animated-edge-path,
 .animated-edge-path {
     stroke-width: 4;
-    stroke: hsl(var(--foreground) / 0.6);
+    stroke: hsl(var(--foreground) / 0.5);
     fill: none;
     stroke-dasharray: 8 6;
-    animation: edge-flow 0.6s linear infinite;
+    stroke-dashoffset: 0;
+    animation: edge-flow 1.2s linear infinite;
+    will-change: stroke-dashoffset;
+    transform: translateZ(0);
+    backface-visibility: hidden;
+    transition: stroke 0.4s ease-out;
+}
+
+.react-flow__edge path.animated-edge-path.animated-edge-path--updating,
+.animated-edge-path.animated-edge-path--updating {
+    stroke: hsl(var(--primary));
 }
 
 @keyframes edge-flow {
-    from {
+    0% {
         stroke-dashoffset: 14;
     }
-
-    to {
+    100% {
         stroke-dashoffset: 0;
     }
 }
 
+/* Connection path roles: pushing (trigger) vs receiving (updating) — classes on BaseNode root */
+.connection-path-trigger {
+    box-shadow: inset 3px 0 0 hsl(var(--primary));
+}
+.connection-path-updating {
+    box-shadow: inset 0 0 0 2px hsl(var(--primary) / 0.4);
+}
+
 /* NodeResizer: snappy drag; no border/background on handles; keep resize cursors. */
 .react-flow__resize-control {
     touch-action: none;
@@ -174,14 +193,37 @@ body {
 }
 
 /* Resize cursor per position (keep cursor style change on hover). */
-.react-flow__resize-control.top.left { cursor: nw-resize; }
-.react-flow__resize-control.top.right { cursor: ne-resize; }
-.react-flow__resize-control.bottom.left { cursor: sw-resize; }
-.react-flow__resize-control.bottom.right { cursor: se-resize; }
-.react-flow__resize-control.top { cursor: n-resize; }
-.react-flow__resize-control.right { cursor: e-resize; }
-.react-flow__resize-control.bottom { cursor: s-resize; }
-.react-flow__resize-control.left { cursor: w-resize; }
+.react-flow__resize-control.top.left {
+    cursor: nw-resize;
+}
+
+.react-flow__resize-control.top.right {
+    cursor: ne-resize;
+}
+
+.react-flow__resize-control.bottom.left {
+    cursor: sw-resize;
+}
+
+.react-flow__resize-control.bottom.right {
+    cursor: se-resize;
+}
+
+.react-flow__resize-control.top {
+    cursor: n-resize;
+}
+
+.react-flow__resize-control.right {
+    cursor: e-resize;
+}
+
+.react-flow__resize-control.bottom {
+    cursor: s-resize;
+}
+
+.react-flow__resize-control.left {
+    cursor: w-resize;
+}
 
 /* Small helper for monospace pre output */
 pre {