Z-Image

ComfyUI Z-Image Workflow Debugging: Complete Troubleshooting Guide

Sarah Jenkins
Sarah Jenkins

ComfyUI Z-Image Workflow Debugging: Complete Troubleshooting Guide

Description: Struggling with ComfyUI Z-Image errors? Master systematic debugging workflows to fix common issues like OOM crashes, missing nodes, blurry outputs, and workflow failures. Get your generations working reliably.

Introduction: When Your Workflow Won't Work

You've spent hours crafting the perfect ComfyUI workflow for Z-Image. You've connected all the nodes, set your parameters, and hit "Queue Prompt." Then... nothing. Or worse, an error message that makes no sense:

RuntimeError: split_with_sizes expects split_sizes to sum exactly to 900
CUDA error: out of memory
Exception during processing: 'norm_final.weight' not found

Sound familiar? You're not alone. Based on analysis of ComfyUI issues from late 2025 through January 2026, Z-Image workflow problems cluster around predictable patterns. The good news: most have systematic fixes you can apply in minutes.

This guide provides a complete debugging framework for ComfyUI Z-Image workflows, organized by symptom and solution. You'll learn to diagnose issues systematically rather than randomly changing settings hoping something sticks.

![Cover image showing workflow debugging process with error messages and solutions flowchart]

ComfyUI workflow debugging interface

Common Error Categories

Based on 2025-2026 ComfyUI issue analysis, errors fall into these categories:

  1. Memory Issues (40%): CUDA OOM, VRAM exhaustion
  2. Model Loading (25%): Missing keys, wrong formats
  3. Workflow Execution (20%): Node connections, missing inputs
  4. Setup Problems (15%): Installation, compatibility

Memory Issue Fixes

Quick Solutions:

  • Start with: python main.py --disable-pinned-memory
  • Reduce resolution: Try 512×512 instead of 1024×1024
  • Enable CPU offloading in Settings → Performance

Memory allocation diagram

Img2Img Troubleshooting

Issue: Img2Img makes images worse instead of better

Solution: Adjust denoising strength:

  • 0.3-0.5: Subtle enhancement, respects original
  • 0.6-0.8: Balanced transformation
  • 0.9+: Complete regeneration

Img2Img strength comparison

Step-by-Step Debugging Process

  1. Read the error message completely - Don't skim it
  2. Identify the failed node from the traceback
  3. Check node connections - Verify all cables are connected
  4. Test with minimal workflow - Isolate the problem
  5. Try one fix at a time - Don't change everything at once

When All Else Fails

  1. Restart ComfyUI completely
  2. Re-download the Z-Image model
  3. Test with a known-good workflow
  4. Ask for help on r/comfyui or GitHub Issues

Prevention Tips

  • Keep ComfyUI updated (git pull)
  • Monitor VRAM usage during generation
  • Test new workflows with small batches first
  • Document working configurations

For specific performance optimizations, see our guide on reducing generation time from 9s to 3s. If you're experiencing the 2-minute lag issue, check our ComfyUI performance lag fix.

External References: