DFC CrossCoder: ToolRL vs Base Qwen2.5-3B

A Dedicated Feature CrossCoder (DFC) trained to compare activations between:

Model A: ToolRL fine-tuned Qwen2.5-3B (chengq9/ToolRL-Qwen2.5-3B)
Model B: Base Qwen2.5-3B (Qwen/Qwen2.5-3B)

Model Overview

The DFC CrossCoder learns sparse feature representations with three partitions:

A-exclusive features: Only accessible to ToolRL model (captures tool-use specific patterns)
B-exclusive features: Only accessible to Base model (captures general text patterns)
Shared features: Accessible to both models (captures common representations)

Model Architecture

Dictionary Size: 16,384 features
Top-K Active: 90 features per sample
Layer: 13 (middle layer of Qwen2.5-3B)
Activation Dim: 2048
Partitioning: 5% A-exclusive, 5% B-exclusive, 90% shared

Usage

import torch
from huggingface_hub import hf_hub_download
from dfc import DFCCrossCoder

# Download and load the model
model_path = hf_hub_download(repo_id="antebe1/dfc-crosscoder-qwen-ToolRL", 
                            filename="model.pt")
config_path = hf_hub_download(repo_id="antebe1/dfc-crosscoder-qwen-ToolRL", 
                             filename="config.json")

# Load the crosscoder
dfc = DFCCrossCoder.load("./", device="cuda")

# Example: Extract features from activations
# activations should be shape (batch_size, 2, 2048) where dim 1 is [model_a, model_b]
activations = torch.randn(1, 2, 2048)  # Replace with real activations
features = dfc.encode(activations)  # Returns sparse feature vector

print(f"Active features: {(features > 0).sum().item()}/{features.shape[-1]}")

Quick Demo

See demo.py for a complete example that shows how to:

Load both models (ToolRL and base)
Extract activations from sample text
Run the CrossCoder to get feature vectors
Analyze partition-specific activations

Training Data

FineWeb: 15,000 general text samples
ToolRL Conversations: 15,000 tool-use conversation samples
Layer: 13 (middle layer representations)

Files

model.pt: PyTorch model weights
config.json: Model configuration
dfc.py: CrossCoder implementation
demo.py: Usage example

Citation

If you use this model, please cite:

@misc{dfc-crosscoder,
  title={DFC CrossCoder: Analyzing Tool-Use vs General Text Features},
  author={[Andre Shportko]},
  year={2026},
  url={https://huggingface.co/your-username/dfc-crosscoder-qwen-ToolRL}
}