🧩 gated-sae-tf

sparse gated autoencoders for TensorFlow & Keras, batteries included

Almost every open-source sparse-autoencoder (SAE) toolkit speaks PyTorch. If you live in TensorFlow/Keras, you've mostly been left to port things yourself. gated-sae-tf closes that gap: a clean, tested, pip-installable gated SAE for dictionary learning and mechanistic interpretability, with the whole training recipe and the interpretability tooling already wired up.

🧠 gated SAE · 📉 warmup→cosine LR · 🔬 sparsity + sharpness reports · 🖼️ feature galleries · ✅ 15 tests · 📦 pip install

💭 Why this exists

I kept wanting to train sparse autoencoders on Keras models without reimplementing the gated SAE from scratch or dragging everything over to PyTorch. So I packaged the version I kept rewriting: the gated formulation from Rajamanoharan et al. (2024), the training tricks that actually make it converge (warmup→cosine LR, gradient clipping, decoder normalization, the auxiliary loss), and the little interpretability utilities you reach for thirty seconds later — sparsity stats, decoder sharpness, feature galleries — all in one importable place.

🧠 What's a gated sparse autoencoder?

A sparse autoencoder learns an overcomplete dictionary of features that reconstruct an input while keeping only a few of them active at a time. The gated variant splits two decisions that a plain ReLU SAE tangles together:

• a gate path decides which features fire: f_gate = 1[π_gate > 0]
• a magnitude path decides how much they fire: f_mag = relu(W_mag·x_c + b_mag)

with the magnitudes tied to the gate via a per-feature rescale, W_mag = exp(r_mag) ⊙ W_gate. The sparse code is f̃ = f_gate ⊙ f_mag and the reconstruction is x̂ = W_dec·f̃ + b_dec, decoder columns kept unit-norm.

Training minimizes:

L = L_reconstruct + λ · L_sparsity + α · L_aux

L_sparsity = Σ relu(π_gate) drives the sparsity, and L_aux reconstructs the input from relu(π_gate) through a frozen (stop_gradient) decoder so the gate path stays well-conditioned. Decoupling the two gives sharper, more monosemantic features than an L1-penalized ReLU SAE, without the shrinkage bias. ✨

📦 Install

pip install gated-sae-tf            # core (TensorFlow + Keras 3)
pip install "gated-sae-tf[viz]"     # + matplotlib for the gallery helpers

Needs Python ≥ 3.10 and TensorFlow ≥ 2.16 (where Keras 3 is the default). The package doesn't pin a TensorFlow build variant, so an existing tensorflow[and-cuda] install is respected.

🚀 Quickstart

import keras, numpy as np
from gated_sae import GatedSAE, WarmupCosineDecay, sparsity_report

(x_train, _), _ = keras.datasets.fashion_mnist.load_data()
X = x_train.reshape(-1, 784).astype("float32") / 255.0

sae = GatedSAE(input_dim=784, encoding_dim=784 * 8,   # 8x overcomplete
               lambda_sparse=1e-3, aux_weight=0.1, clip_norm=1.0)
sae(X[:2])                          # build the weights
sae.b_dec.assign(X.mean(axis=0))    # init decoder bias to the data mean

steps = (len(X) // 256) * 20
sae.compile(optimizer=keras.optimizers.Adam(
    WarmupCosineDecay(1e-3, warmup_steps=steps // 10, total_steps=steps),
    beta_1=0.0, beta_2=0.999))       # beta_1=0 per the paper

sae.fit(X, epochs=20, batch_size=256)
print(sparsity_report(sae, X))       # L0, alive/dead features, top-k share

That trains an 8× overcomplete gated SAE on Fashion-MNIST and prints the L0 mean/median, alive/dead feature counts, and the top-k activation share. A full end-to-end walkthrough notebook ships in the repository (examples/).

🧰 The API, at a glance

🗺️ Roadmap

• More SAE variants (vanilla ReLU, JumpReLU, TopK)
• Activation-store helpers for SAEs on transformer activations
• Pretrained dictionaries / model-hub integration

💛 Contributing

Issues and PRs are genuinely welcome — a new SAE variant, a docs fix, a bug report, all of it. The full walkthrough notebook, the contributing guide, and the extended bibliography live alongside this file in the repository (GUIDE.md and CONTRIBUTING.md).

🤖 How it was made

Built with Claude, shaped and reviewed by me. The implementation follows the gated SAE paper; training, serialization, and every interpretability utility are covered by a 15-test suite that runs in CI.

📚 References & citing

This library implements the gated SAE of Rajamanoharan et al. (2024), Improving Dictionary Learning with Gated Sparse Autoencoders, arXiv:2404.16014 — https://arxiv.org/abs/2404.16014

It sits in the interpretability lineage of Anthropic's Transformer Circuits work on dictionary learning:

• Bricken et al. (2023). Towards Monosemanticity: Decomposing Language Models With Dictionary Learning. Transformer Circuits Thread — https://transformer-circuits.pub/2023/monosemantic-features
• Templeton et al. (2024). Scaling Monosemanticity: Extracting Interpretable Features from Claude 3 Sonnet. Transformer Circuits Thread — https://transformer-circuits.pub/2024/scaling-monosemanticity/index.html

Full bibliography, BibTeX, and related work (Elhage et al., Gao et al.) are in GUIDE.md in the repository.

⚖️ License

MIT © 2026 Aishwarya Natesh.