fix(subflows): subflow-child selection issues, subflow error logs

[icecrasher321]

Summary

Couple of subflows issues:

• Should not be able to multiselect a subflow and a child inside it. Leading to odd behaviours across the board.
• Subflow error logs surfacing restored
• Subflows with all disabled blocks should throw same runtime error as empty subflow.

Type of Change

• Bug fix

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)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		Mar 19, 2026 1:52am

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PR Summary

Medium Risk
Touches workflow-canvas selection/drag handling and executor subflow initialization, which can affect editor UX and runtime failures for loops/parallels. Changes are localized but involve nuanced selection state and new error conditions/logging.

Overview
Improves subflow UX by making subflow containers clickable/selectable across the full body area and enforcing selection context rules so users can’t multi-select a container and its children (or mix selections across different subflows). Panel editor syncing is updated to show the last selected block, and shift/marquee/drag selection paths now run through a unified resolveSelectionConflicts flow (including edge-selection context IDs).

Hardens subflow execution by preventing DAG build from mutating serialized loop/parallel configs, treating subflows with no reachable/executable children as effectively empty, and surfacing clearer runtime errors/logs when loops/parallels have no executable blocks or when forEach/parallel distributions are empty.

^{Written by Cursor Bugbot for commit 9f22e6a. Configure here.}

[greptile-apps]

Greptile Summary

This PR fixes three related subflow bugs: preventing mixed selection of a subflow container and its children, restoring subflow error log surfacing, and ensuring subflows with all-disabled blocks throw the same runtime error as empty subflows.

Key changes:

• subflow-node.tsx: The subflow body div now captures pointer events and acts as a workflow-drag-handle with a click handler (matching the header), instead of using pointer-events: none — correctly preventing child nodes from being co-selected without breaking ReactFlow's sibling-rendered child nodes.
• workflow.tsx: handleNodeClick now routes through resolveParentChildSelectionConflicts on the controlled displayNodes state, ensuring parent-child conflict resolution is applied consistently across click, shift-click, and marquee selection.
• loops.ts / parallels.ts (DAG constructors): When a reachable loop/parallel has no reachable children, loopConfig.nodes / parallelConfig.nodes is set to [] (instead of skipping sentinel creation), allowing the orchestrators to detect and report the all-disabled state at runtime.
• builder.ts: The validateSubflow method no longer throws for empty nodes; the error is deferred to the orchestrator layer.
• loop.ts / parallel.ts (orchestrators): New early-exit paths with proper error logging for empty nodes (all-disabled blocks), empty forEachItems, and empty parallel distribution.

Confidence Score: 3/5

• Mostly safe to merge, but the in-place mutation of serialized config objects in the DAG constructors could cause incorrect behaviour in scenarios where the same workflow is built more than once (e.g. tests or retry logic).
• The UI and executor logic changes are well-reasoned and address the described bugs. The main concern is that loopConfig.nodes = [] and parallelConfig.nodes = [] in the constructors mutate shared serialized workflow objects, which violates immutability and could silently break repeated builds. The double-wrapped error message for empty parallel distributions is a minor UX issue. All three concerns are in the executor's core path.
• apps/sim/executor/dag/construction/loops.ts and apps/sim/executor/dag/construction/parallels.ts — the in-place mutation of config node arrays; apps/sim/executor/orchestrators/parallel.ts — the double-wrapped error message.

Important Files Changed

Filename	Overview
apps/sim/executor/dag/construction/loops.ts	Refactored to skip loops with unreachable children by emptying loopConfig.nodes in-place rather than skipping sentinel creation — the in-place mutation of the shared config object is a potential correctness risk if the workflow is built more than once.
apps/sim/executor/dag/construction/parallels.ts	Same sentinel-creation refactor as loops.ts with the same in-place mutation concern for parallelConfig.nodes; structure mirrors loops.ts exactly.
apps/sim/executor/dag/builder.ts	Validation for empty subflow nodes now silently returns instead of throwing, deferring the error to the orchestrator layer; the change is intentional and coherent with the orchestrator additions.
apps/sim/executor/orchestrators/loop.ts	Two new early-exit paths added: one for empty nodes (all-disabled blocks), one for forEachItems being null/undefined/empty-string; both produce proper error logs and scopes before throwing, which restores the subflow error logging previously lost.
apps/sim/executor/orchestrators/parallel.ts	Adds early exit for empty-nodes parallel; changes resolveDistributionItems from returning [] to throwing — the thrown error is then caught and re-wrapped by the outer try/catch, producing a verbose double-prefixed message visible to users.
apps/sim/app/workspace/[workspaceId]/w/[workflowId]/workflow.tsx	Fixes parent-child multi-selection conflicts by routing click events through resolveParentChildSelectionConflicts and using the controlled displayNodes state; uses the same selectedIdsRef updater-synchrony pattern already present in onNodesChange.
apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/subflows/subflow-node.tsx	Body div now captures pointer events (unless preview) and acts as a drag/click handle for the subflow, replacing the previous pointer-events: none approach; comment is updated to accurately reflect the new DOM structure rationale.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
A[DAGBuilder.build] --> B[LoopConstructor / ParallelConstructor]
B --> C{subflow reachable?}
C -- No --> D[skip - no sentinels]
C -- Yes --> E{any reachable children?}
E -- Yes --> F[keep nodes, create sentinels]
E -- No --> G[config.nodes = empty, create sentinels]
F --> H[validateSubflow]
G --> H
H --> I{nodes empty?}
I -- Yes --> J[return silently]
I -- No --> K{sentinel connected to child?}
K -- No --> L[throw: start not connected]
K -- Yes --> M[DAG ready]
G --> N[Orchestrator.initializeScope]
N --> O{nodes.length === 0?}
O -- Yes --> P[addErrorLog + throw runtime error]
O -- No --> Q[normal execution]

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