FIX_APPLIED.md

Meta Tensor Error - Fix Applied ✅

Summary of Changes

Successfully applied fixes to resolve the "Tensor.item() cannot be called on meta tensors" error that was preventing model initialization on Hugging Face Spaces with ZeroGPU.

Files Modified

1. acestep/handler.py - 3 fixes

• ✅ Line 498: DiT model loading with device_map={"": device}
• ✅ Line 573: VAE model loading with device_map={"": vae_device}
• ✅ Line 606: Text encoder loading with device_map={"": text_encoder_device}

2. acestep/llm_inference.py - 3 fixes

• ✅ Line 282: Main LLM loading with device_map={"": target_device}
• ✅ Line 3028: vLLM scoring model with device_map={"": str(device)}
• ✅ Line 3058: MLX scoring model with device_map={"": device}

What Was Fixed

The issue occurred because on Hugging Face Spaces with ZeroGPU, Transformers creates models on "meta" device (placeholder tensors) during initialization. The custom ACE-Step model code tried to perform operations during __init__, which failed with meta tensors.

By adding explicit device_map parameters to all model loading calls, we force models to load directly onto the target device (CUDA/CPU), bypassing the meta device phase entirely.

Deployment Steps

Option 1: Automated (Recommended)

deploy_hf_fix.bat

This script will:

1. Show current git status
2. Ask for confirmation
3. Commit changes with descriptive message
4. Push to remote repository

Option 2: Manual

git add acestep/handler.py acestep/llm_inference.py
git commit -m "Fix: Add device_map to prevent meta tensor errors on ZeroGPU"
git push

After Deployment

Monitor your HF Space logs for:

✅ Expected (Success):

2026-02-09 XX:XX:XX - acestep.handler - INFO - [initialize_service] Attempting to load model with attention implementation: sdpa
2026-02-09 XX:XX:XX - acestep.handler - INFO - ✅ Model initialized successfully on cuda

❌ Previously (Error):

RuntimeError: Tensor.item() cannot be called on meta tensors

Testing Checklist

After deployment to HF Space:

• Space builds successfully without errors
• Models initialize without meta tensor errors
• Standard generation works with test prompts
• No crashes during model loading
• GPU allocation works correctly with ZeroGPU

Documentation

• FIX_META_TENSOR_ERROR.md - Detailed technical explanation
• verify_fix.py - Local verification script
• deploy_hf_fix.bat - Automated deployment script

Support

If you encounter issues after deployment:

1. Check HF Space logs for specific error messages
2. Verify all 6 device_map additions are in your deployed code
3. Ensure Transformers version >= 4.20.0 in requirements.txt
4. Check that spaces package is properly configured for ZeroGPU

Expected Behavior

✅ Models load directly to CUDA on ZeroGPU ✅ No meta device intermediate step ✅ All tensor operations work correctly during initialization ✅ Compatible with both local and HF Space environments

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Status: ✅ Fix Applied and Ready for Deployment Date: 2026-02-09 Impact: Resolves critical initialization failure on HF Spaces