ComfyUI Troubleshooting Guide

Render completes but looks WRONG (artifacts, wrong subject/pose/color, a ControlNet/mask/LoRA not taking, a refiner degrading it)? That's not an error. Use the debug-render skill (list_packs with action: "skill_read", name: "debug-render") to localize the bad stage with run-to-node (panel_run to_node_id) by previewing intermediate steps. This guide is for runs that fail with an error, OOM, or missing node.

Error Diagnosis Strategy

When a workflow fails, follow this approach:

1. Get the error. Use get_history(action="diagnose") to retrieve the execution result with the full traceback, plus any missing models/nodes
2. Check logs. Use get_system_stats (action:"logs") with keyword filters like "error", "warning", "traceback"
3. Identify the failing node. The history response includes the node_id and node_type that failed
4. Cross-reference inputs. Use create_workflow (action:"node_info") to verify the failing node's expected input schema
5. Check models. Use list_local_models to verify all referenced model files exist