improvement(executor): subflows, hitl handling cleanup

[icecrasher321]

Summary

Refactors parallel batching onto explicit DAG control flow while hardening nested subflow execution, pause/resume, run-from-block, and output resolution edge cases.

Type of Change

• Other: Code quality

Testing

Tested manually

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	May 26, 2026 7:33pm

[cursor]

PR Summary

High Risk
Touches core workflow execution (DAG construction, edge activation, nested loops/parallels, pause/resume, and variable resolution); regressions could stall runs or mis-route branches.

Overview
This PR refactors how loops and parallels are represented and executed: DAG nodes use unified subflowId / subflowType metadata (replacing separate loopId / parallelId fields), with shared sentinel construction in sentinels.ts.

DAG wiring gains explicit subflow control edges: start→end bypass routes for skip-at-start / early exit, parallel_continue back-edges (mirroring loop continue), and tighter handling when edges stay inside the same parallel or cross nested subflows. EdgeManager now keys deactivated edges with JSON (fixing prefix collisions), honors parallel_continue / subflow control handles, and can restore deactivated-edge state on resume.

Runtime behavior shifts parallel batching to sentinel-driven prepareCurrentBatch / prepareForBatchContinuation instead of ad-hoc dynamic queue expansion. Loops can be skippedAtStart (empty forEach, zero iterations, false while) and exit via loop_exit without running the body. Block output resolution is branch-aware, including stable __obranch-* aliases and stricter scoping for cloned outer branches.

Pause / resume / run-from-block: snapshots persist deactivated edges and activated join nodes; resumed edges mark targets as activated before readiness checks; pause completion is recorded before returning paused. Restored parallel batches re-register cloned nested subflows in the parent map. Large test coverage accompanies these paths.

^{Reviewed by Cursor Bugbot for commit 70d0777. Configure here.}

[greptile-apps]

Greptile Summary

This PR refactors the workflow executor's parallel batching and nested subflow handling: batch expansion is deferred from initializeParallelScope to a new prepareCurrentBatch call on sentinel-start, eliminating a race where in-flight branches could have their state reset mid-execution. It also unifies loopId/parallelId node metadata into a single subflowId/subflowType pair, adds handleParentSubflowCompletion to propagate nested subflow exit outputs to parent containers, and introduces updateResumeOutputInAggregationBuffers to patch HITL pause entries in aggregation buffers before snapshot serialization.

• Parallel batch timing fix: prepareCurrentBatch (now called at sentinel-start) replaces the inline expandParallel call in initializeParallelScope and scheduleNextBatch; advanceToNextBatch only advances scope counters and the next sentinel-start cycle drives the actual DAG expansion.
• Metadata unification: NodeMetadata.loopId/parallelId/isParallelSentinel collapsed into subflowId/subflowType; all orchestrators, resolvers, and the edge manager updated accordingly.
• Nested subflow output propagation: handleParentSubflowCompletion fires on sentinel-end nodes and pushes { results } to the parent parallel's branch outputs or the parent loop's iteration outputs, replacing ad-hoc per-orchestrator logic.

Confidence Score: 3/5

The core batch-timing refactor and metadata unification look structurally sound, but the empty-parallel path loses its execution log because sentinel-end is never activated after emitEmptySubflowEvents was removed without a parallel-equivalent of the loop skippedAtStart sentinel-end bypass.

The redesign correctly fixes the concurrent batch-reset race by deferring expansion to sentinel-start. However, the empty-parallel case silently drops the block log: prepareCurrentBatch returns early, sentinel-start emits sentinelStart true with no selectedRoute, the PARALLEL_EXIT bypass edge is classified as a control edge and deactivated, and sentinel-end never fires. Empty loops handle this correctly with skippedAtStart plus selectedRoute LOOP_EXIT; the parallel path has no equivalent.

apps/sim/executor/orchestrators/parallel.ts (prepareCurrentBatch empty-scope early return and sentinel-start return value for empty parallels), apps/sim/executor/execution/state.ts (getScopedBlockOutput linear scan)

Important Files Changed

Filename	Overview
apps/sim/executor/orchestrators/parallel.ts	Major refactor: batch expansion moved from initializeParallelScope to new prepareCurrentBatch (called at sentinel-start time), advanceToNextBatch replaces scheduleNextBatch. Empty parallel case loses its block log because sentinel-end is never activated.
apps/sim/executor/orchestrators/node.ts	Unifies loopId/parallelId metadata into subflowId/subflowType; adds handleParentSubflowCompletion to propagate nested subflow outputs to parent parallel/loop; adds isFinalSentinelOutput to correctly classify sentinel output finality.
apps/sim/executor/execution/engine.ts	Adds handleNodeCompletion call for _pauseMetadata outputs and widens the stopAfterBlockId guard to include PARALLEL_CONTINUE.
apps/sim/executor/execution/state.ts	Adds getScopedBlockOutput for outer-branch-aware lookups with full-scan O(n) fallback; early-returns undefined for outer-branch nodes not found in scope.
apps/sim/executor/execution/edge-manager.ts	Switches edge key format to JSON arrays, adds restoreDeactivatedEdges for snapshot resume, and adds PARALLEL_CONTINUE edge activation logic.
apps/sim/executor/utils/parallel-expansion.ts	Rewrites edge wiring and boundary detection to use resolveBranchChildBoundaryId; separates cloneDAGNode from edge remapping via remapClonedEdges.
apps/sim/executor/dag/construction/edges.ts	Adds addSubflowStartExitBypass for bypass edges and edgeStaysWithinSameParallel to correctly route intra-parallel edges through sentinel boundaries.
apps/sim/lib/workflows/executor/human-in-the-loop-manager.ts	Adds updateResumeOutputInAggregationBuffers to patch _pauseMetadata entries in aggregation buffers with isPausedOutputForContext guard.
apps/sim/executor/utils/subflow-utils.ts	Adds subflowContainsBlock and isSubflowNestedInside for recursive containment checks; adds extractInnermostOuterBranchIndex and buildOuterBranchScopedId helpers.
apps/sim/executor/execution/executor.ts	Adds registerRestoredClonedSubflows to rebuild subflowParentMap for cloned subflows after snapshot restore; adds branchIndex to parentMap entries.

Sequence Diagram

sequenceDiagram
    participant E as ExecutionEngine
    participant SStart as ParallelSentinelStart
    participant PO as ParallelOrchestrator
    participant Branch as BranchNodes
    participant SEnd as ParallelSentinelEnd
    participant NO as NodeOrchestrator
    E->>SStart: execute
    SStart->>PO: initializeParallelScope
    SStart->>PO: prepareCurrentBatch
    PO->>PO: expandParallel, registerClonedSubflows, resetBatchExecutionState
    SStart-->>E: sentinelStart true
    E->>Branch: execute branches
    Branch-->>E: output per branch
    E->>NO: handleNodeCompletion
    NO->>PO: handleParallelBranchCompletion
    E->>SEnd: all branch edges satisfied
    SEnd->>PO: aggregateParallelResults
    alt more batches
        PO->>PO: advanceToNextBatch
        SEnd-->>E: PARALLEL_CONTINUE
        E->>SStart: re-execute
    else done
        PO->>PO: emitSubflowSuccessEvents
        SEnd-->>E: PARALLEL_EXIT
    end

Loading

_{Reviews (7): Last reviewed commit: "address comments" | Re-trigger Greptile}

[icecrasher321]

bugbot run

[icecrasher321]

@greptile

[icecrasher321]

@greptile

[icecrasher321]

bugbot run

[icecrasher321]

@greptile

[icecrasher321]

@greptile

[icecrasher321]

bugbot run

[icecrasher321]

bugbot run

[icecrasher321]

@greptile

[icecrasher321]

bugbot run

[icecrasher321]

bugbot run

[icecrasher321]

@greptile

[icecrasher321]

bugbot run

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 70d0777. Configure here.}