ComfyUI: KSamplerAdvanced Stuck At 0% On MPS? [SOLVED]

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Hey everyone! Are you having trouble with ComfyUI's KSamplerAdvanced node getting stuck at 0% when using MPS (Metal Performance Shaders)? You're definitely not alone! This can be a super frustrating issue, especially when you're eager to create some awesome AI art. In this article, we'll dive deep into this problem, explore potential causes, and provide you with practical solutions to get your workflows running smoothly again. Let's get started and fix this thing!

Understanding the KSamplerAdvanced Node

Before we jump into troubleshooting, let's quickly recap what the KSamplerAdvanced node actually does. This node is a crucial part of the ComfyUI workflow, acting as the engine that generates your images. It takes various inputs like your prompts, models, and samplers, and then iteratively refines the image through a process called sampling. Think of it like a digital artist carefully painting a picture, stroke by stroke. The KSamplerAdvanced node gives you a lot of control over this process, allowing you to tweak settings and achieve specific artistic styles.

Why is the KSamplerAdvanced Node so Important?

  • Flexibility: It offers a wide range of settings and options, giving you fine-grained control over the image generation process.
  • Customization: You can use different samplers, schedulers, and noise settings to achieve unique results.
  • Performance: When configured correctly, it can optimize the sampling process for your hardware, leading to faster generation times.

So, when this node gets stuck, it basically brings your entire creative process to a halt. That's why it's so important to figure out what's causing the issue and how to resolve it. Now, let's look at the specific problem of it getting stuck at 0% on MPS.

The MPS (Metal Performance Shaders) Issue

MPS is Apple's framework for leveraging the GPU in their devices. It's designed to accelerate computationally intensive tasks, like machine learning, and is the key to running ComfyUI efficiently on Macs. However, sometimes things don't go as planned, and you might encounter issues like the KSamplerAdvanced node freezing at 0%. This usually indicates a problem with how ComfyUI is interacting with your Mac's GPU.

Common Causes for the 0% Stuck Issue on MPS

  • Compatibility Issues: Older versions of ComfyUI, PyTorch, or even your macOS might not play well together. Keeping everything updated is crucial.
  • Memory Problems: Running out of VRAM (Video RAM) can cause the process to stall. This is especially common with larger models or high-resolution outputs.
  • Driver Issues: Although MPS is part of macOS, underlying driver problems can still occur, leading to unexpected behavior.
  • Workflow Complexity: Extremely complex workflows with many nodes and high resolutions can sometimes overwhelm the system.
  • Specific Model Issues: Some models might have compatibility issues with MPS or require specific configurations to run correctly.

Now that we know the potential culprits, let's dive into some troubleshooting steps!

Troubleshooting Steps: Getting Unstuck!

Okay, guys, let's get our hands dirty and try to fix this KSamplerAdvanced issue. Here's a step-by-step guide to help you get back on track:

1. Check Your System Requirements

First things first, let's make sure your system meets the minimum requirements for running ComfyUI with MPS. This includes:

  • macOS Version: Make sure you're running a compatible version of macOS (ideally the latest or a recent version).
  • PyTorch Version: ComfyUI relies on PyTorch for its heavy lifting. Ensure you have a compatible and up-to-date version installed. You can check this within your ComfyUI environment.
  • Hardware: While MPS is designed to work across a range of Apple devices, older hardware might struggle with complex tasks. Consider your Mac's specifications, especially the GPU and RAM.

2. Update Everything!

Seriously, update everything. This is often the magic bullet for weird issues. Here's what you should update:

  • ComfyUI: Use the ComfyUI-Manager (if you have it) or manually update to the latest version. This often includes bug fixes and performance improvements.
  • ComfyUI-Manager: Ensure the manager itself is up-to-date, as it helps manage other dependencies.
  • PyTorch: Update PyTorch within your ComfyUI virtual environment. You can usually do this using pip. Make sure to use the correct commands for your setup.
  • macOS: Check for macOS updates in System Preferences. Apple often releases updates that include driver improvements and bug fixes.

3. Monitor Your VRAM Usage

Running out of VRAM is a common cause of the 0% issue. Here's how to keep an eye on it:

  • Activity Monitor: Use macOS's Activity Monitor (found in /Applications/Utilities) to check GPU memory usage. Keep an eye on the "GPU Memory" section when running your workflow.
  • Reduce Resolution: If you're consistently maxing out your VRAM, try reducing the output resolution of your images. This will significantly decrease memory consumption.
  • Optimize Workflow: Simplify your workflow if possible. Remove unnecessary nodes or try breaking it down into smaller parts.
  • Batch Size: If you are generating multiple images at once, try reducing the batch size.

4. Try Different Samplers and Schedulers

Sometimes, specific samplers or schedulers can cause issues on certain hardware. Experimenting with different options might help:

  • Sampler: Try switching between samplers like Euler, Euler a, LMS, or DPM++ variants. Some might be more efficient on MPS than others.
  • Scheduler: Similarly, experiment with different schedulers within the KSamplerAdvanced node.

5. Check for Conflicting Extensions or Custom Nodes

If you're using custom nodes or extensions, one of them might be the troublemaker. Here's how to investigate:

  • Disable Extensions: Try disabling extensions one by one (or in groups) to see if the issue goes away. The ComfyUI-Manager makes this relatively easy.
  • Identify the Culprit: If disabling an extension fixes the problem, you've found the culprit! You can then try updating the extension or contacting its developer for support.

6. Simplify Your Workflow

Complex workflows can sometimes overwhelm the system, especially on MPS. Try these strategies:

  • Reduce Nodes: Remove any unnecessary nodes from your workflow.
  • Break It Down: Divide your workflow into smaller, more manageable sections. Run them separately and then combine the results.
  • Lower Resolution: Temporarily reduce the output resolution to see if the problem persists.

7. Test with Different Models

Certain models might be more demanding or have compatibility issues with MPS. Try these steps:

  • Switch Models: Experiment with different Stable Diffusion models (e.g., try a smaller or more optimized model).
  • Check Model Requirements: Some models might have specific requirements or recommendations for MPS. Check the model's documentation or community discussions.

8. Reinstall ComfyUI and Dependencies

If all else fails, a clean reinstall can sometimes resolve underlying issues. Follow these steps:

  • Backup: Back up your important workflows, custom nodes, and models.
  • Remove ComfyUI: Completely remove your ComfyUI installation and its virtual environment.
  • Reinstall: Follow the official ComfyUI installation instructions to set it up again from scratch.
  • Reinstall Dependencies: Ensure you reinstall all necessary dependencies, including PyTorch, as per the ComfyUI documentation.

9. Check the Console Logs

Sometimes, error messages or warnings in the console can provide valuable clues. Here's how to check them:

  • Run from Terminal: Run ComfyUI from the terminal or command prompt so you can see the output in real-time.
  • Look for Errors: Pay close attention to any error messages or warnings that appear when the KSamplerAdvanced node gets stuck.
  • Search Online: Use the error messages to search online forums, communities, or the ComfyUI GitHub repository for solutions.

Analyzing the Provided Debug Logs

Okay, let's put on our detective hats and take a look at the debug logs you shared. These logs can give us some important clues about what's going on under the hood.

Key Things to Look For in the Logs

  • Errors and Warnings: Obvious error messages are your best friend! They often pinpoint the exact issue.
  • Model Loading: Check if the models are loading correctly and if there are any issues during the loading process.
  • Memory Usage: Look for messages related to memory allocation or VRAM usage.
  • Custom Nodes: See if any custom nodes are causing errors or taking a long time to load.
  • Dependencies: Verify that all dependencies are installed and up to date.

Initial Observations from Your Logs

Based on the provided logs, here are a few things that stand out:

  • ComfyUI-Manager: The logs show that the ComfyUI-Manager is installed and running. This is good, as it can help manage dependencies and updates.
  • PyTorch Version: The PyTorch version is 2.10.0.dev20250917. While this is a development version, it should generally be compatible. However, it's worth considering if a more stable release might help.
  • MPS Device: ComfyUI is correctly detecting and using the MPS device (your Mac's GPU).
  • Model Loading: The logs show that the WanTEModel and WanVAE models are being loaded. If the issue consistently occurs with these models, they might be a factor.
  • No Immediate Errors: At first glance, there aren't any glaring error messages in the logs leading up to the point where the process gets stuck. This means we need to dig deeper.

Steps to Further Analyze the Logs

  1. Reproduce the Issue: Run the workflow again while closely monitoring the console logs. See if any new errors or warnings appear specifically when the KSamplerAdvanced node gets stuck.
  2. Filter the Logs: Use text search (Ctrl+F or Cmd+F) to search for keywords like "error", "warning", "MPS", "VRAM", or the names of any custom nodes you're using.
  3. Check Specific Nodes: If you suspect a particular node, try running a simpler workflow that only uses that node to see if the issue persists.

Specific Issues and Potential Solutions Based on the Logs

While the logs don't immediately scream out a solution, let's brainstorm some possibilities based on what we've seen:

  • Model-Specific Problem: The issue might be related to the WanTEModel or WanVAE models. Try using different models to see if the problem goes away. If it does, the original models might have compatibility issues with your setup or MPS.
  • Memory Pressure: Even though you have a significant amount of RAM and VRAM, complex workflows can still push the limits. Try reducing the resolution, batch size, or simplifying your workflow to see if it helps.
  • PyTorch Development Version: Consider switching to a stable release of PyTorch. While development versions can be exciting, they might also have undiscovered bugs.
  • Underlying MPS Issue: Although MPS is generally reliable, there could be an underlying issue with how it's interacting with PyTorch or ComfyUI. Updating macOS or trying different PyTorch versions might help.

Real-World Examples and Scenarios

Let's look at some real-world scenarios where users have encountered this issue and how they solved it:

Scenario 1: VRAM Exhaustion

  • Problem: A user was generating high-resolution images with a complex workflow and consistently got stuck at 0% with the KSamplerAdvanced node.
  • Solution: They reduced the output resolution and batch size, which significantly lowered VRAM usage. They also optimized their workflow by removing unnecessary nodes.

Scenario 2: Conflicting Extension

  • Problem: Another user had a custom node that was interfering with the MPS backend, causing the KSamplerAdvanced node to freeze.
  • Solution: They disabled extensions one by one until they found the culprit. After identifying the problematic extension, they either updated it or removed it from their workflow.

Scenario 3: Outdated PyTorch

  • Problem: A user was running an older version of PyTorch that had compatibility issues with ComfyUI and MPS.
  • Solution: They updated PyTorch to the latest stable version, which resolved the issue.

Scenario 4: Model-Specific Issue

  • Problem: A specific Stable Diffusion model was causing the KSamplerAdvanced node to get stuck, while other models worked fine.
  • Solution: The user switched to a different model or found a patched version of the original model that was compatible with their setup.

Community Resources and Support

Don't feel like you're in this alone! The ComfyUI community is super active and helpful. Here are some resources you can tap into:

  • ComfyUI GitHub Repository: Check the issues section for similar problems and potential solutions. You can also submit a new issue if you can't find a fix.
  • ComfyUI Discord Server: Join the Discord server for real-time help and discussions with other users.
  • Online Forums and Communities: Search online forums and communities related to Stable Diffusion and AI art. Chances are, someone else has encountered the same issue and found a solution.

Final Thoughts and Tips for Preventing Future Issues

Okay, guys, we've covered a lot of ground! Hopefully, you've now got a good handle on how to troubleshoot the KSamplerAdvanced node getting stuck at 0% on MPS. Here are some final tips to help you prevent future headaches:

  • Keep Everything Updated: Regularly update ComfyUI, PyTorch, macOS, and your extensions.
  • Monitor VRAM Usage: Keep an eye on your VRAM usage and optimize your workflows accordingly.
  • Test New Models and Extensions: Before incorporating new models or extensions into your main workflow, test them in a simpler setup to identify potential issues.
  • Read the Documentation: Pay attention to the documentation and requirements for models and extensions.
  • Join the Community: Engage with the ComfyUI community and learn from others' experiences.
  • Create Backups: Regularly back up your workflows and important files.

By following these tips and the troubleshooting steps we've discussed, you'll be well-equipped to tackle any KSamplerAdvanced challenges that come your way. Happy creating, guys! And remember, if you're still stuck, don't hesitate to reach out to the community for help. We're all in this together!