Transformer Lens Interpretability

---
name: transformer-lens-interpretability
description: Provides guidance for mechanistic interpretability research using TransformerLens to inspect and manipulate transformer internals via HookPoints and activation caching. Use when reverse-engineering model algorithms, studying attention patterns, or performing activation patching experiments.
version: 1.0.0
author: Orchestra Research
license: MIT
tags: [Mechanistic Interpretability, TransformerLens, Activation Patching, Circuit Analysis]
dependencies: [transformer-lens>=2.0.0, torch>=2.0.0]
---

# TransformerLens: Mechanistic Interpretability for Transformers

TransformerLens is the de facto standard library for mechanistic interpretability research on GPT-style language models. Created by Neel Nanda and maintained by Bryce Meyer, it provides clean interfaces to inspect and manipulate model internals via HookPoints on every activation.

**GitHub**: [TransformerLensOrg/TransformerLens](https://github.com/TransformerLensOrg/TransformerLens) (2,900+ stars)

## When to Use TransformerLens

**Use TransformerLens when you need to:**
- Reverse-engineer algorithms learned during training
- Perform activation patching / causal tracing experiments
- Study attention patterns and information flow
- Analyze circuits (e.g., induction heads, IOI circuit)
- Cache and inspect intermediate activations
- Apply direct logit attribution… load the full skill through Skill Me