---
license: other
pretty_name: Crosscoder Multilayer Split Activations
tags:
  - mechanistic-interpretability
  - crosscoder
  - activations
  - sparse-autoencoder
---

# Crosscoder Multilayer Split Activations

Raw split activation artifacts for multilayer SPARC-style crosscoder training.

This dataset stores reusable base-only and aligned-only activation tensors. These
are intended to be assembled into matched `activations.pt` training artifacts
before crosscoder training.

## Versions

### v1

Source local run: `interp_utils/crosscoder/results-multi-v1`

Layout:

```text
v1/
  base_activations/
    smollm3-union/
    llama32-3b-union/
    qwen3-4b-union/
  aligned_activations/
    smollm3-{dpo,grpo,kto,orpo,ppo,simpo}/
    llama32-3b-{dpo,grpo,kto,orpo,ppo,simpo}/
    qwen3-4b-{dpo,grpo,kto,orpo,ppo,simpo}/
```

Each run directory contains:

```text
run_meta.json
activations/base_activations.pt      # base-only runs
activations/aligned_activations.pt   # aligned-only runs
```

The base tensors contain union layer sets. The aligned tensors contain each
aligned model's target probe-best layer window. Assembly slices/reorders the
base union tensor to the aligned run's layers.

## v1 Base Layers

```text
smollm3-union:      [16, 17, 18, 19, 20]
llama32-3b-union:   [10, 11, 12, 13, 14, 23, 24, 25, 26]
qwen3-4b-union:     [19, 20, 21, 22, 23, 24, 25]
```

## Use

Download one base union and one aligned run, then assemble locally with:

```bash
.venv/bin/python -m interp_utils.crosscoder.main \
  --stage assemble \
  --crosscoder-kind multilayer_sparc \
  --base-activations-dir path/to/base_union_dir \
  --aligned-activations-dir path/to/aligned_run_dir \
  --output-dir path/to/assembled_run_dir
```