fix(workflow): hide idle nested subflow end handles (#6976)

* fix(workflow): hide idle nested subflow end handles

* perf(workflow): avoid repeated subflow edge scans

* perf(workflow): stabilize subflow edge selector

---------

Co-authored-by: Bill Leoutsakos <billleoutsakos@Bills-MacBook-Pro.local>
Co-authored-by: Waleed Latif <walif6@gmail.com>

Author: 3 people

apps/docs/components/workflow-preview/docs-container-node.tsx

@@ -8,6 +8,7 @@ interface DocsContainerData {
   name: string
   blockType: string
   size?: { width: number; height: number }
+  parentId?: string
 }
 
 /**
@@ -24,6 +25,7 @@ export const DocsContainerNode = memo(function DocsContainerNode({
     name: data.name,
     width: data.size?.width,
     height: data.size?.height,
+    parentId: data.parentId,
     isPreview: true,
   }
 

apps/docs/components/workflow-preview/workflow-data.test.ts

@@ -0,0 +1,63 @@
+/**
+ * @vitest-environment node
+ */
+import { BLOCK_Z_BASE, CONTAINER_CHILD_Z_BASE, getEdgeZIndex } from '@sim/workflow-renderer'
+import { describe, expect, it } from 'vitest'
+import { type PreviewBlock, type PreviewWorkflow, toReactFlowElements } from './workflow-data'
+
+const block = (
+  overrides: Partial<PreviewBlock> & Pick<PreviewBlock, 'id' | 'type'>
+): PreviewBlock => ({
+  name: overrides.id,
+  bgColor: '#000000',
+  rows: [],
+  position: { x: 0, y: 0 },
+  ...overrides,
+})
+
+const workflow: PreviewWorkflow = {
+  id: 'nested-subflows',
+  name: 'Nested subflows',
+  blocks: [
+    block({ id: 'start', type: 'starter' }),
+    block({ id: 'loop', type: 'loop', size: { width: 500, height: 300 } }),
+    block({
+      id: 'parallel',
+      type: 'parallel',
+      parentId: 'loop',
+      position: { x: 24, y: 64 },
+      size: { width: 400, height: 200 },
+    }),
+    block({ id: 'agent', type: 'agent', parentId: 'loop', position: { x: 24, y: 140 } }),
+  ],
+  edges: [
+    { id: 'start-loop', source: 'start', target: 'loop' },
+    { id: 'loop-parallel', source: 'loop', target: 'parallel' },
+    { id: 'loop-agent', source: 'loop', target: 'agent' },
+  ],
+}
+
+describe('toReactFlowElements layering', () => {
+  it('places incoming edges on their container target layer', () => {
+    const { nodes, edges } = toReactFlowElements(workflow, false, {
+      highlightEdge: 'loop-parallel',
+    })
+    const nodeById = new Map(nodes.map((node) => [node.id, node]))
+    const edgeById = new Map(edges.map((edge) => [edge.id, edge]))
+
+    expect(nodeById.get('loop')?.zIndex).toBe(0)
+    expect(nodeById.get('parallel')?.zIndex).toBe(1)
+    expect(edgeById.get('start-loop')?.zIndex).toBe(0)
+    expect(edgeById.get('loop-parallel')?.zIndex).toBe(1)
+  })
+
+  it('keeps ordinary cards above normally layered edges', () => {
+    const { nodes, edges } = toReactFlowElements(workflow)
+    const nodeById = new Map(nodes.map((node) => [node.id, node]))
+    const edgeById = new Map(edges.map((edge) => [edge.id, edge]))
+
+    expect(nodeById.get('start')?.zIndex).toBe(BLOCK_Z_BASE)
+    expect(nodeById.get('agent')?.zIndex).toBe(CONTAINER_CHILD_Z_BASE)
+    expect(edgeById.get('loop-agent')?.zIndex).toBe(getEdgeZIndex(0))
+  })
+})

apps/docs/components/workflow-preview/workflow-data.ts

@@ -1,3 +1,9 @@
+import {
+  BLOCK_Z_BASE,
+  CONTAINER_CHILD_Z_BASE,
+  getEdgeZIndex,
+  getEdgeZIndexForTarget,
+} from '@sim/workflow-renderer'
 import { type Edge, type Node, Position } from 'reactflow'
 
 /**
@@ -61,6 +67,24 @@ export interface HighlightOptions {
   selectedBlock?: string
 }
 
+/** Semantic container depth used for z-order while docs positions stay flattened. */
+function getNestingDepth(block: PreviewBlock, blocksById: Map<string, PreviewBlock>): number {
+  let depth = 0
+  let parentId = block.parentId
+  const visited = new Set<string>()
+
+  while (parentId && !visited.has(parentId)) {
+    const parent = blocksById.get(parentId)
+    if (!parent) break
+
+    visited.add(parentId)
+    depth += 1
+    parentId = parent.parentId
+  }
+
+  return depth
+}
+
 /**
  * Converts a {@link PreviewWorkflow} to React Flow nodes and edges.
  *
@@ -81,6 +105,7 @@ export function toReactFlowElements(
 
   const nodes: Node[] = workflow.blocks.map((block, index) => {
     const isContainer = Boolean(block.size)
+    const nestingDepth = getNestingDepth(block, blocksById)
     // Nested blocks are authored relative to their container; render them at
     // absolute coordinates (not React Flow parentNode children) so the edges
     // between a container and its nested blocks render reliably and on top.
@@ -92,7 +117,7 @@ export function toReactFlowElements(
       id: block.id,
       type: isContainer ? 'previewContainer' : 'previewBlock',
       position,
-      zIndex: isContainer ? 0 : 1,
+      zIndex: isContainer ? nestingDepth : block.parentId ? CONTAINER_CHILD_Z_BASE : BLOCK_Z_BASE,
       ...(block.size ? { style: { width: block.size.width, height: block.size.height } } : {}),
       data: {
         name: block.name,
@@ -103,6 +128,7 @@ export function toReactFlowElements(
         tools: block.tools,
         hideTargetHandle: block.hideTargetHandle,
         size: block.size,
+        parentId: block.parentId,
         index,
         animate,
         isHighlighted: highlightBlock === block.id || selectedBlock === block.id,
@@ -127,6 +153,14 @@ export function toReactFlowElements(
     // so edges into and out of Loop/Parallel containers still connect.
     const sourceBlock = blocksById.get(e.source)
     const targetBlock = blocksById.get(e.target)
+    const parentContainer = blocksById.get(sourceBlock?.parentId ?? targetBlock?.parentId ?? '')
+    const baseZIndex = getEdgeZIndex(
+      parentContainer ? getNestingDepth(parentContainer, blocksById) : undefined,
+      { isHighlighted: isEdgeHighlight }
+    )
+    const targetContainerZIndex = targetBlock?.size
+      ? getNestingDepth(targetBlock, blocksById)
+      : undefined
     const sourceHandle =
       e.sourceHandle ?? (sourceBlock?.size ? `${sourceBlock.type}-end-source` : 'source')
     const targetHandle = targetBlock?.size ? undefined : 'target'
@@ -142,6 +176,7 @@ export function toReactFlowElements(
       },
       sourceHandle,
       targetHandle,
+      zIndex: getEdgeZIndexForTarget(baseZIndex, targetContainerZIndex),
       data: {
         animate,
         delay: animate ? sourceIndex * BLOCK_STAGGER + BLOCK_STAGGER : 0,

apps/docs/package.json

@@ -10,6 +10,7 @@
     "build": "fumadocs-mdx && NODE_OPTIONS='--max-old-space-size=8192' next build",
     "start": "next start",
     "postinstall": "fumadocs-mdx",
+    "test": "vitest run",
     "type-check": "fumadocs-mdx && tsc --noEmit",
     "lint": "biome check --write --unsafe .",
     "lint:check": "biome check .",
@@ -47,6 +48,7 @@
     "@types/react-dom": "^19.0.4",
     "postcss": "^8.5.3",
     "tailwindcss": "^4.0.12",
-    "typescript": "^7.0.2"
+    "typescript": "^7.0.2",
+    "vitest": "^4.1.0"
   }
 }

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/workflow.tsx

@@ -28,6 +28,7 @@ import {
   EDGE_Z_MAX,
   getBlockZIndex,
   getEdgeZIndex,
+  getEdgeZIndexForTarget,
   getNoteBlockHeight,
   normalizeCursorSourceHandleId,
 } from '@sim/workflow-renderer'
@@ -4887,10 +4888,16 @@ const WorkflowContent = React.memo(
             isEdgeSelected: isSelected,
           }),
         })
+        const targetContainerZIndex =
+          targetNode?.type === 'subflowNode' ? (targetNode.zIndex ?? 0) : undefined
+        // The target node paints after an equal-z edge. A nested container is
+        // one depth above its parent, so this hides only the segment beneath
+        // the target while leaving the route visible over the parent body.
+        const zIndex = getEdgeZIndexForTarget(baseZIndex, targetContainerZIndex)
 
         return {
           ...edge,
-          zIndex: baseZIndex,
+          zIndex,
           data: {
             ...edge.data,
             isSelected,
@@ -4899,6 +4906,7 @@ const WorkflowContent = React.memo(
             parentLoopId,
             sourceHandle: edge.sourceHandle,
             onDelete: handleEdgeDelete,
+            ...(targetContainerZIndex !== undefined ? { labelZIndex: zIndex } : {}),
           },
         }
       })

apps/sim/app/workspace/[workspaceId]/w/components/preview/components/preview-workflow/components/subflow/subflow.tsx

@@ -12,6 +12,7 @@ interface WorkflowPreviewSubflowData {
   width?: number
   height?: number
   kind: 'loop' | 'parallel'
+  parentId?: string
   /** Whether this subflow is enabled */
   enabled?: boolean
   /** Whether this subflow is selected in preview mode */

apps/sim/app/workspace/[workspaceId]/w/components/preview/components/preview-workflow/preview-workflow.tsx

@@ -22,6 +22,7 @@ import {
   CONTAINER_DIMENSIONS,
   EDGE_Z_BASE,
   EDGE_Z_MAX,
+  getEdgeZIndexForTarget,
 } from '@sim/workflow-renderer'
 import { normalizeWorkflowEdgeHandles } from '@sim/workflow-types/workflow'
 import { WorkflowEdge } from '@/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-edge/workflow-edge'
@@ -567,6 +568,14 @@ export function PreviewWorkflow({
     return normalizeWorkflowEdgeHandles(workflowState.edges).map((edge) => {
       const status = getEdgeExecutionStatus(edge)
       const isErrorEdge = edge.sourceHandle === 'error'
+      const baseZIndex =
+        status === 'success' ? EDGE_Z_MAX : isErrorEdge ? EDGE_Z_BASE + 2 : EDGE_Z_BASE
+      const targetBlock = workflowState.blocks[edge.target]
+      const targetContainerZIndex =
+        targetBlock?.type === 'loop' || targetBlock?.type === 'parallel'
+          ? calculateNestingDepth(targetBlock, workflowState.blocks)
+          : undefined
+
       return {
         id: edge.id,
         source: edge.source,
@@ -580,12 +589,14 @@ export function PreviewWorkflow({
         /* Inside the shared edge band, so a line clears the opaque container it
            crosses and still passes behind cards. Execution status orders edges
            within the band: a successful path draws over an error one, which
-           draws over an unexecuted one. */
-        zIndex: status === 'success' ? EDGE_Z_MAX : isErrorEdge ? EDGE_Z_BASE + 2 : EDGE_Z_BASE,
+           draws over an unexecuted one. A Loop/Parallel target overrides that
+           ordering so its node paints over the incoming segment. */
+        zIndex: getEdgeZIndexForTarget(baseZIndex, targetContainerZIndex),
       }
     })
   }, [
     edgesStructure,
+    workflowState.blocks,
     workflowState.edges,
     isValidWorkflowState,
     blockExecutionMap,

bun.lock

@@ -9,6 +9,7 @@ import {
   EDGE_Z_MAX,
   getBlockZIndex,
   getEdgeZIndex,
+  getEdgeZIndexForTarget,
 } from './canvas-layers'
 
 /**
@@ -69,3 +70,36 @@ describe('getEdgeZIndex', () => {
     expect(getEdgeZIndex(8)).toBeLessThan(getEdgeZIndex(undefined, { isHighlighted: true }))
   })
 })
+
+describe('getEdgeZIndexForTarget', () => {
+  it('shares a container target layer so the node paints over the incoming edge', () => {
+    const parentZIndex = 0
+    const targetZIndex = 1
+    const edgeZIndex = getEdgeZIndex(parentZIndex)
+
+    const resolved = getEdgeZIndexForTarget(edgeZIndex, targetZIndex)
+
+    expect(resolved).toBe(targetZIndex)
+    expect(resolved).toBeGreaterThan(parentZIndex)
+  })
+
+  it('places incoming edges beneath top-level container targets', () => {
+    expect(getEdgeZIndexForTarget(EDGE_Z_BASE, 0)).toBe(0)
+  })
+
+  it('does not let highlighting elevate an edge over its container target', () => {
+    const highlighted = getEdgeZIndex(undefined, { isHighlighted: true })
+
+    expect(getEdgeZIndexForTarget(highlighted, 2)).toBe(2)
+  })
+
+  it('does not let an execution edge elevate over its container target', () => {
+    expect(getEdgeZIndexForTarget(EDGE_Z_MAX, 2)).toBe(2)
+  })
+
+  it('leaves edges to ordinary blocks unchanged', () => {
+    const edgeZIndex = getEdgeZIndex(1)
+
+    expect(getEdgeZIndexForTarget(edgeZIndex, undefined)).toBe(edgeZIndex)
+  })
+})

packages/workflow-renderer/src/canvas-layers.test.ts

@@ -9,12 +9,15 @@
  * - {@link CONTAINER_CHILD_Z_BASE} — cards inside a container (same +1 / +10 steps)
  * - {@link CONNECTION_PICKER_Z} — the connection block picker
  *
- * Containers and edges must occupy separate bands. A container paints an opaque
- * body, so an edge sharing its z loses the equal-z tiebreak to DOM order — React
- * Flow renders the nodes layer after the edges layer — and is drawn *behind* the
- * container. That is what hid every line crossing a top-level subflow, whether
- * in flight or persisted. Cards then sit above the edge band, so a line still
- * passes behind card chrome, knobs, and the action-bar swell.
+ * Containers and ordinary edges occupy separate bands. A container paints an
+ * opaque body, so an edge sharing its z loses the equal-z tiebreak to DOM order
+ * — React Flow renders the nodes layer after the edges layer — and is drawn
+ * *behind* the container. Incoming container edges deliberately use that rule
+ * at their target's depth: the target sits above its parent by one depth, leaving
+ * the edge over the parent body but beneath the target. The edge can also be
+ * occluded by peer or higher-depth containers it crosses. Cards then sit above
+ * the edge band, so every other line still passes behind card chrome, knobs, and
+ * the action-bar swell.
  *
  * Shared by the editor canvas and the read-only preview because both render the
  * same graph through the same React Flow layering rules; a second scale drifted
@@ -74,3 +77,22 @@ export function getEdgeZIndex(
   const depth = containerZIndex === undefined ? 0 : containerZIndex + 1
   return Math.min(EDGE_Z_BASE + depth, EDGE_Z_DEPTH_MAX)
 }
+
+/**
+ * Keeps an incoming edge beneath a Loop/Parallel target without hiding it
+ * behind that target's parent.
+ *
+ * Containers use their nesting depth as z-index, so a nested target is exactly
+ * one layer above its parent. React Flow renders equal-z edges before nodes;
+ * sharing the target's layer therefore leaves the edge visible over the parent
+ * body while the target paints over the segment that reaches beneath it.
+ *
+ * `targetContainerZIndex` must only be supplied when the edge targets a
+ * container. Ordinary edges retain their existing depth/highlight ordering.
+ */
+export function getEdgeZIndexForTarget(
+  edgeZIndex: number,
+  targetContainerZIndex: number | undefined
+): number {
+  return targetContainerZIndex ?? edgeZIndex
+}