lyramakesmusic/neuron-explorer

neuron explorer

Steering-first neuron explorer for Qwen3.5-4B. Every MLP neuron in a layer is pushed up and down on a few prompts, every rollout is kept, and the explorer lays the results out over a 3D view of the model.

Explorer

uv sync uv run python explorer/server.py # http://localhost:8791

Reads sweep runs from runs/ and per-layer stats from stats/, both produced by the sweep below; the caches in explorer/cache/ ship with the repo. Loads Qwen3.5-4B locally (MPS, CUDA or CPU) for live steered chat, lens, connections and live inference over your own text.

• map: the model's layers in perspective, attention and MLP per layer, one point per neuron. Hover shows a neuron's

steer lens and logit lens; click opens it; click a layer's label to view its sheet face-on. writes places neurons with similar down-projection columns next to each other.

• list: units ranked by word-cluster mass against random-direction controls; lens searches the steer and logit

lenses for a token, fires runs your text through the model and filters neurons by activation.

• neuron: steered rollouts per prompt and dose, a three-column multi-turn steered chat (−, 0, +), lens and

connections, and a name.

• embeddings: UMAP of a layer's rollouts, coloured by neuron, prompt, dose or kind.
• language: the interface follows the browser language on first visit; the menu at the right of the header

switches between English and Simplified Chinese (the choice is kept in this browser). Translations live in explorer/static/i18n.js.

• Claude (fourth neuron-panel tab, or the right-edge handle): a chat running the claude CLI (installed and

logged in) with the explorer as an MCP server (explorer/agent_mcp.py). It reads neurons, cones and lenses, runs the live model (steering, activations, next-token logprobs, ablations), moves the map, list and highlights, and has file tools and a shell in your home folder. Its prompt is explorer/agent_prompt.md plus explorer/agent_methodology.md, and explorer/agent_prompt.local.md when present (untracked, for your own additions); EXPLORER_CLAUDE_MODEL picks the model. The server answers only pages and tools on this machine.

Sweep

Runs on a CUDA 13 GPU pod with the steering fork of vLLM (RhizoNymph/vllm).

bash sweep/setup_pod.sh # fork, deps, model; writes /workspace/env.sh python sweep/neuron_stats.py --layers 22 --tokens 2000000 --out stats/q35-4b python sweep/steer_sweep.py --stats stats/q35-4b_L22.npz --design main_rel --dose-unit rel \ --neurons all --random-controls 256 --run q35-4b-L22 sweep/run_depth.sh "4 9 13 17" 384 64 # random-subset sweep across several layers

main_rel doses are fractions of the median residual norm leaving the layer: {who, snake, orange} × {−0.7, +0.5, +0.8} and {free} × {+3}, plus one unsteered baseline per prompt.

| script | output | |---|---| | sweep/neuron_stats.py | per-neuron activation extremes by sign regime, down columns, residual norms | | sweep/steer_sweep.py | runs/.jsonl: text, token ids, logprobs, top-k per step; optional activation captures | | sweep/rank.py | runs/.units.jsonl: distinctive words, cluster mass, percentile against controls | | sweep/steer_lens.py | stats/steer_lens_L{l}.npz: next-token Δlogprob and KL for ±0.8 pushes on every neuron | | sweep/depth_report.py | runs/depth_report.json: per-layer share of neurons above controls, coherence, top units | | sweep/shift.py | word-shift score against controls, all words counted | | sweep/merge_runs.py | joins sharded runs of one layer | | sweep/check_equivalence.py | HF vs vLLM steering and capture agreement | | sweep/bench.py, sweep/peek.py | throughput conditions; terminal views of a run | | explorer/build_embeddings.py | runs/.umap.json | | explorer/build_layout.py | explorer/cache/layout_writes.npz | | explorer/build_connections.py | explorer/cache/connections.npz: each neuron's 24 strongest direct-path links up and down | | sweep/capture_prefill.py | captures/.mlp_in.npy: MLP input at the last prompt token at the run's capture layers, steered |

research_log.md holds the findings and reasoning; NOTES.md the source notes.

License

MIT, see LICENSE.