Purpose and Architecture
Neuron Explorer tackles the challenge of understanding internal model mechanics through a steering-first methodology on Qwen3.5-4B. Rather than relying solely on passive feature observation, it actively perturbs MLP neurons across various dose levels and records complete output rollouts.
Core Capabilities
The local web explorer (http://localhost:8791) combines multiple analytical views:
- Spatial Navigation: A 3D layer perspective arranges neurons based on down-projection matrix similarities (
writes). Hovering surfaces steer and logit lenses.
- Evaluation & Clustering: Provides list rankings against random controls, live activation filtering on user text, and UMAP embeddings of rollout clusters.
- Agent Integration: An MCP server (
explorer/agent_mcp.py) connects the claude CLI, allowing an AI assistant to inspect lenses, trigger ablations, and control UI highlights autonomously.
Technology and Maturity
Built with Python and managed via uv, the pipeline uses a custom vLLM fork (RhizoNymph/vllm) for high-throughput GPU sweeps. While popular among researchers with roughly 1,500 GitHub stars, it remains an experimental research instrument with an unspecified software licence, tailored specifically for mechanistic interpretability practitioners.