[Verified] Give-First Fix Guide Python & CUDA Environment Windows 10/11 x64 and Linux x64 (Python 3.10-3.12 Virtual Environments)

Fix AssertionError: Torch Not Compiled with CUDA Enabled on Windows 10/11

IMMEDIATE FIX SUMMARY

AssertionError: Torch not compiled with CUDA enabled happens when pip installs the default CPU-only PyTorch wheel from PyPI instead of the CUDA-enabled build (+cu121 or +cu124). Uninstall torch, torchvision, and torchaudio inside your active virtual environment, then reinstall them with –index-url https://download.pytorch.org/whl/cu124.

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1. Exact Terminal Error Signature & Stack Trace

If your standalone ComfyUI, Ollama, or Python terminal outputs the following error on Windows 10/11 x64 or Linux x64:

AssertionError: Torch not compiled with CUDA enabled
RuntimeError: Found no NVIDIA driver on your system. Please check that you have an NVIDIA GPU and installed a driver

2. Root Cause in Standalone Python, ComfyUI, or Ollama

[Verified] Running a plain pip install torch or installing a custom node whose requirements.txt lists torch without an index URL overwrites your GPU PyTorch installation with the default CPU wheel on Windows and Linux. When ComfyUI starts, torch.cuda.is_available() returns False and crashes on initialization.

3. Manual CLI Fix for Standalone Users (100% Free Utility)

Run the following commands in your terminal or update your launch configuration to resolve the issue immediately in a standalone installation:

# 1. Activate your ComfyUI virtual environment (or use python_embeded\python.exe on portable builds):
pip uninstall -y torch torchvision torchaudio
# 2. Install the official CUDA 12.4 wheel for NVIDIA GPUs:
pip install torch torchvision torchaudio --index-url https://download.pytorch.org/whl/cu124
# 3. Verify CUDA visibility before restarting ComfyUI:
python -c "import torch; print(torch.__version__, 'CUDA:', torch.cuda.is_available())"

4. How Logen 1.4.0 Prevents This Error Automatically

Logen 1.4.0 provisions a dedicated, isolated Python runtime inside %LOCALAPPDATA%\Logen\ (Windows) or ~/.local/share/Logen/ (Linux) pinned to verified CUDA wheels. Your system Python, global pip packages, and external virtual environments never touch Logen's diffusion engine.

Supported platforms: Windows 10/11 x64 (Logen-1.4.0-Setup.exe) and Linux x64 (Logen-1.4.0.AppImage, Logen-1.4.0-amd64.deb). macOS is not supported.

5. Check Your GPU & Model Memory Headroom

INTERACTIVE PC & MODEL FIT CALCULATOR (TRUTH CONTRACT MATH)

Calculate Exact Dedicated VRAM Headroom on Windows 10/11 & Linux x64

Select your NVIDIA graphics card, diffusion model, operating system, and target resolution to compute deterministic peak VRAM usage before you download weights.

1. NVIDIA GPU Tier

2. Diffusion Checkpoint

3. Operating System

4. Output Resolution

VERDICT STATE FITS_IN_VRAM_COMFORTABLE (+1.60 GB Headroom)

EPISTEMIC TIER [Verified Measured]

Dedicated VRAM 12.00 GB

Peak Full-Resident Load 10.40 GB

Sequential Offload Load 9.20 GB

Benchmark / Bandwidth Note 26.83s (4 steps on RTX A2000 12GB)

Formula: Dedicated_VRAM (12.0 GB) – [Weights (6.8 GB) + Encoder (1.2 GB) + VAE Buffer (0.9 GB) + OS Reserve (1.5 GB)] = +1.60 GB available headroom.

6. Troubleshooting FAQ: Fix AssertionError: Torch Not Compiled with CUDA Enabled on Windows 10/11

How can I check if PyTorch is using CPU or CUDA?

Run python -c "import torch; print(torch.__version__, torch.cuda.is_available())". If the version string ends with +cpu or prints False, the environment has the CPU-only wheel installed.

Why did installing a ComfyUI custom node break my CUDA setup?

Many custom node scripts run pip install -r requirements.txt without specifying the PyTorch CUDA wheel index. If pip resolves a newer torch version on default PyPI, it replaces your +cu124 build with a +cpu build.

Do I need to install the NVIDIA CUDA Toolkit SDK separately for Logen 1.4.0?

No. You only need a standard NVIDIA GeForce or RTX display driver installed on Windows 10/11 or Linux x64. Logen's Setup Wizard bundles the required CUDA runtime libraries automatically.

7. Related Local AI & ComfyUI Error Guides

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Fix Prompt Outputs Failed Validation: DualCLIPLoader / VAELoader Not Found in ComfyUI (Missing Nodes & Checkpoints)
Fix CUDA Out of Memory When Running Ollama and ComfyUI Together (VRAM & OOM)
Fix Cannot Import ComfyUI-GGUF Module: No Module Named 'gguf' (Missing Nodes & Checkpoints)
Fix Windows 10/11 WDDM Shared GPU Memory Slowdown (Why FLUX Drops from 25s to 4 Minutes) (VRAM & OOM)
Fix Error: connect ECONNREFUSED 127.0.0.1:11434 (WinError 10061) in Local AI Apps (Ollama & Background Services)
Fix Black Image or NaN Tensor Output When Decoding FLUX VAE in ComfyUI (VAE & Precision Errors)
Fix dlopen(): error loading libfuse.so.2 When Launching AppImage on Ubuntu 22.04 / 24.04 (Linux Desktop & Packaging)
Fix OutOfMemoryError During 4x RealESRGAN 4K Upscaling in ComfyUI (VRAM & OOM)

Checking hardware compatibility? Browse the Local AI GPU & VRAM Compatibility Index or explore Logen 1.4.0 Desktop Studio.

SKIP MANUAL PYTHON DEBUGGING

Generate with FLUX.1-schnell, FLUX.2 [klein] 4B & Z-Image-Turbo in a self-healing desktop studio.

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