fix(parallel): add parallel sentinel to make parallel-parallel and parallel-loop work correctly (#2593)

* fix(parallel): add parallel sentinel to make parallel-parallel and parallel-loop work correctly

* fix regular -> parallel + copilot nested subflows

* add tests

* consolidate to always explode parallel dag at runtime

Author: icecrasher321

apps/sim/executor/constants.ts

@@ -53,6 +53,7 @@ export const EDGE = {
   LOOP_CONTINUE: 'loop_continue',
   LOOP_CONTINUE_ALT: 'loop-continue-source',
   LOOP_EXIT: 'loop_exit',
+  PARALLEL_EXIT: 'parallel_exit',
   ERROR: 'error',
   SOURCE: 'source',
   DEFAULT: 'default',
@@ -88,6 +89,16 @@ export const PARALLEL = {
     SUFFIX: '₎',
   },
 
+  SENTINEL: {
+    PREFIX: 'parallel-',
+    START_SUFFIX: '-sentinel-start',
+    END_SUFFIX: '-sentinel-end',
+    START_TYPE: 'start' as SentinelType,
+    END_TYPE: 'end' as SentinelType,
+    START_NAME_PREFIX: 'Parallel Start',
+    END_NAME_PREFIX: 'Parallel End',
+  },
+
   DEFAULT_COUNT: 1,
 } as const
 

apps/sim/executor/dag/builder.ts

@@ -2,9 +2,14 @@ import { createLogger } from '@sim/logger'
 import { EdgeConstructor } from '@/executor/dag/construction/edges'
 import { LoopConstructor } from '@/executor/dag/construction/loops'
 import { NodeConstructor } from '@/executor/dag/construction/nodes'
+import { ParallelConstructor } from '@/executor/dag/construction/parallels'
 import { PathConstructor } from '@/executor/dag/construction/paths'
 import type { DAGEdge, NodeMetadata } from '@/executor/dag/types'
-import { buildSentinelStartId, extractBaseBlockId } from '@/executor/utils/subflow-utils'
+import {
+  buildParallelSentinelStartId,
+  buildSentinelStartId,
+  extractBaseBlockId,
+} from '@/executor/utils/subflow-utils'
 import type {
   SerializedBlock,
   SerializedLoop,
@@ -31,6 +36,7 @@ export interface DAG {
 export class DAGBuilder {
   private pathConstructor = new PathConstructor()
   private loopConstructor = new LoopConstructor()
+  private parallelConstructor = new ParallelConstructor()
   private nodeConstructor = new NodeConstructor()
   private edgeConstructor = new EdgeConstructor()
 
@@ -50,6 +56,7 @@ export class DAGBuilder {
     const reachableBlocks = this.pathConstructor.execute(workflow, triggerBlockId)
 
     this.loopConstructor.execute(dag, reachableBlocks)
+    this.parallelConstructor.execute(dag, reachableBlocks)
 
     const { blocksInLoops, blocksInParallels, pauseTriggerMapping } = this.nodeConstructor.execute(
       workflow,
@@ -135,7 +142,9 @@ export class DAGBuilder {
       )
     }
 
-    const sentinelStartNode = dag.nodes.get(buildSentinelStartId(id))
+    const sentinelStartId =
+      type === 'Loop' ? buildSentinelStartId(id) : buildParallelSentinelStartId(id)
+    const sentinelStartNode = dag.nodes.get(sentinelStartId)
     if (!sentinelStartNode) return
 
     const hasConnections = Array.from(sentinelStartNode.outgoingEdges.values()).some((edge) =>