What problem does it solve? Understanding why a transformer produces a specific behavior requires more than scoring individual neurons or heads in isolation. This Skill localizes the minimal subgraph of a model's computational graph — the attention heads, MLPs, and the edges connecting them — that is causally responsible for a given behavior, yielding a verifiable mechanism-level explanation. ## Core Features & Use Cases - Exact Iterative Search (ACDC): Prunes edges via activation patching with corrupted inputs, walking the graph in reverse topological order until a minimal faithful circuit remains. - Fast Gradient-Based Attribution (EAP-IG): Scores every edge in a few forward/backward passes using Edge Attribution Patching with Integrated Gradients, then thresholds scores to obtain a circuit. - Faithfulness Evaluation: Recovered circuits are validated on a held-out task distribution to confirm they actually implement the behavior rather than merely correlating with it. - Use Case: A researcher studying the 'greater-than' task in GPT-2 can run the EAP-IG demo to score all edges, select the top-n circuit, and measure the performance drop when components outside the circuit are ablated. ## Quick Start Ask the agent to run the EAP-IG demo on a TransformerLens GPT-2 model to score edges, extract a top-n circuit, and evaluate its faithfulness on the greater-than task.