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Use when discovering interpretable features, analyzing superposition, or studying monosemantic representations in language models.","Tashima-Tarsh\u002FDisha6.6","Tashima-Tarsh","https:\u002F\u002Favatars.githubusercontent.com\u002Fu\u002F269906498?v=4","01M6PBH98X03XERH0HFT4PFB1P","NITISH KUMAR","01M6PBH9DA0M6KM3Z12P848F0K",0,"MIT","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fqc-saelens\u002FSKILL.md",[18],{"categoryNo":19,"categoryName":20,"taxonomyType":21,"taxonomyTypeDesc":22},"01JBSEEDCAT000000000000021","资料检索与研究","SCENARIO","使用场景",[24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43],"training","sparse autoencoder training","features","research","for","orchestra","Interpretability","Transformer","lens","neural network","ai-research","saelens","feature","superposition","Neural","decompose","use","discovery","network","analyzing","2026-11-10 10:12:30",false,"---\nname: sparse-autoencoder-training\ndescription: Provides guidance for training and analyzing Sparse Autoencoders (SAEs) using SAELens to decompose neural network activations into interpretable features. Use when discovering interpretable features, analyzing superposition, or studying monosemantic representations in language models.\nversion: 1.0.0\nauthor: Orchestra Research\nlicense: MIT\ntags: [Sparse Autoencoders, SAE, Mechanistic Interpretability, Feature Discovery, Superposition]\ndependencies: [sae-lens>=6.0.0, transformer-lens>=2.0.0, torch>=2.0.0]\ncategory: \"ai-research\"\n---\n\n# SAELens: Sparse Autoencoders for Mechanistic Interpretability\n\nSAELens is the primary library for training and analyzing Sparse Autoencoders (SAEs) - a technique for decomposing polysemantic neural network activations into sparse, interpretable features. Based on Anthropic's groundbreaking research on monosemanticity.\n\n**GitHub**: [jbloomAus\u002FSAELens](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens) (1,100+ stars)\n\n## The Problem: Polysemanticity & Superposition\n\nIndividual neurons in neural networks are **polysemantic** - they activate in multiple, semantically distinct contexts. This happens because models use **superposition** to represent more features than they have neurons, making interpretability difficult.\n\n**SAEs solve this** by decomposing dense activations into sparse, monosemantic features - typically only a small number of features activate for any given input, and each feature corresponds to an interpretable concept.\n\n## When to Use SAELens\n\n**Use SAELens when you need to:**\n- Discover interpretable features in model activations\n- Understand what concepts a model has learned\n- Study superposition and feature geometry\n- Perform feature-based steering or ablation\n- Analyze safety-relevant features (deception, bias, harmful content)\n\n**Consider alternatives when:**\n- You need basic activation analysis → Use **TransformerLens** directly\n- You want causal intervention experiments → Use **pyvene** or **TransformerLens**\n- You need production steering → Consider direct activation engineering\n\n## Installation\n\n```bash\npip install sae-lens\n```\n\nRequirements: Python 3.10+, transformer-lens>=2.0.0\n\n## Core Concepts\n\n### What SAEs Learn\n\nSAEs are trained to reconstruct model activations through a sparse bottleneck:\n\n```\nInput Activation → Encoder → Sparse Features → Decoder → Reconstructed Activation\n    (d_model)       ↓        (d_sae >> d_model)    ↓         (d_model)\n                 sparsity                      reconstruction\n                 penalty                          loss\n```\n\n**Loss Function**: `MSE(original, reconstructed) + L1_coefficient × L1(features)`\n\n### Key Validation (Anthropic Research)\n\nIn \"Towards Monosemanticity\", human evaluators found **70% of SAE features genuinely interpretable**. Features discovered include:\n- DNA sequences, legal language, HTTP requests\n- Hebrew text, nutrition statements, code syntax\n- Sentiment, named entities, grammatical structures\n\n## Workflow 1: Loading and Analyzing Pre-trained SAEs\n\n### Step-by-Step\n\n```python\nfrom transformer_lens import HookedTransformer\nfrom sae_lens import SAE\n\n# 1. Load model and pre-trained SAE\nmodel = HookedTransformer.from_pretrained(\"gpt2-small\", device=\"cuda\")\nsae, cfg_dict, sparsity = SAE.from_pretrained(\n    release=\"gpt2-small-res-jb\",\n    sae_id=\"blocks.8.hook_resid_pre\",\n    device=\"cuda\"\n)\n\n# 2. Get model activations\ntokens = model.to_tokens(\"The capital of France is Paris\")\n_, cache = model.run_with_cache(tokens)\nactivations = cache[\"resid_pre\", 8]  # [batch, pos, d_model]\n\n# 3. Encode to SAE features\nsae_features = sae.encode(activations)  # [batch, pos, d_sae]\nprint(f\"Active features: {(sae_features > 0).sum()}\")\n\n# 4. Find top features for each position\nfor pos in range(tokens.shape[1]):\n    top_features = sae_features[0, pos].topk(5)\n    token = model.to_str_tokens(tokens[0, pos:pos+1])[0]\n    print(f\"Token '{token}': features {top_features.indices.tolist()}\")\n\n# 5. Reconstruct activations\nreconstructed = sae.decode(sae_features)\nreconstruction_error = (activations - reconstructed).norm()\n```\n\n### Available Pre-trained SAEs\n\n| Release | Model | Layers |\n|---------|-------|--------|\n| `gpt2-small-res-jb` | GPT-2 Small | Multiple residual streams |\n| `gemma-2b-res` | Gemma 2B | Residual streams |\n| Various on HuggingFace | Search tag `saelens` | Various |\n\n### Checklist\n- [ ] Load model with TransformerLens\n- [ ] Load matching SAE for target layer\n- [ ] Encode activations to sparse features\n- [ ] Identify top-activating features per token\n- [ ] Validate reconstruction quality\n\n## Workflow 2: Training a Custom SAE\n\n### Step-by-Step\n\n```python\nfrom sae_lens import SAE, LanguageModelSAERunnerConfig, SAETrainingRunner\n\n# 1. Configure training\ncfg = LanguageModelSAERunnerConfig(\n    # Model\n    model_name=\"gpt2-small\",\n    hook_name=\"blocks.8.hook_resid_pre\",\n    hook_layer=8,\n    d_in=768,  # Model dimension\n\n    # SAE architecture\n    architecture=\"standard\",  # or \"gated\", \"topk\"\n    d_sae=768 * 8,  # Expansion factor of 8\n    activation_fn=\"relu\",\n\n    # Training\n    lr=4e-4,\n    l1_coefficient=8e-5,  # Sparsity penalty\n    l1_warm_up_steps=1000,\n    train_batch_size_tokens=4096,\n    training_tokens=100_000_000,\n\n    # Data\n    dataset_path=\"monology\u002Fpile-uncopyrighted\",\n    context_size=128,\n\n    # Logging\n    log_to_wandb=True,\n    wandb_project=\"sae-training\",\n\n    # Checkpointing\n    checkpoint_path=\"checkpoints\",\n    n_checkpoints=5,\n)\n\n# 2. Train\ntrainer = SAETrainingRunner(cfg)\nsae = trainer.run()\n\n# 3. Evaluate\nprint(f\"L0 (avg active features): {trainer.metrics['l0']}\")\nprint(f\"CE Loss Recovered: {trainer.metrics['ce_loss_score']}\")\n```\n\n### Key Hyperparameters\n\n| Parameter | Typical Value | Effect |\n|-----------|---------------|--------|\n| `d_sae` | 4-16× d_model | More features, higher capacity |\n| `l1_coefficient` | 5e-5 to 1e-4 | Higher = sparser, less accurate |\n| `lr` | 1e-4 to 1e-3 | Standard optimizer LR |\n| `l1_warm_up_steps` | 500-2000 | Prevents early feature death |\n\n### Evaluation Metrics\n\n| Metric | Target | Meaning |\n|--------|--------|---------|\n| **L0** | 50-200 | Average active features per token |\n| **CE Loss Score** | 80-95% | Cross-entropy recovered vs original |\n| **Dead Features** | \u003C5% | Features that never activate |\n| **Explained Variance** | >90% | Reconstruction quality |\n\n### Checklist\n- [ ] Choose target layer and hook point\n- [ ] Set expansion factor (d_sae = 4-16× d_model)\n- [ ] Tune L1 coefficient for desired sparsity\n- [ ] Enable L1 warm-up to prevent dead features\n- [ ] Monitor metrics during training (W&B)\n- [ ] Validate L0 and CE loss recovery\n- [ ] Check dead feature ratio\n\n## Workflow 3: Feature Analysis and Steering\n\n### Analyzing Individual Features\n\n```python\nfrom transformer_lens import HookedTransformer\nfrom sae_lens import SAE\nimport torch\n\nmodel = HookedTransformer.from_pretrained(\"gpt2-small\", device=\"cuda\")\nsae, _, _ = SAE.from_pretrained(\n    release=\"gpt2-small-res-jb\",\n    sae_id=\"blocks.8.hook_resid_pre\",\n    device=\"cuda\"\n)\n\n# Find what activates a specific feature\nfeature_idx = 1234\ntest_texts = [\n    \"The scientist conducted an experiment\",\n    \"I love chocolate cake\",\n    \"The code compiles successfully\",\n    \"Paris is beautiful in spring\",\n]\n\nfor text in test_texts:\n    tokens = model.to_tokens(text)\n    _, cache = model.run_with_cache(tokens)\n    features = sae.encode(cache[\"resid_pre\", 8])\n    activation = features[0, :, feature_idx].max().item()\n    print(f\"{activation:.3f}: {text}\")\n```\n\n### Feature Steering\n\n```python\ndef steer_with_feature(model, sae, prompt, feature_idx, strength=5.0):\n    \"\"\"Add SAE feature direction to residual stream.\"\"\"\n    tokens = model.to_tokens(prompt)\n\n    # Get feature direction from decoder\n    feature_direction = sae.W_dec[feature_idx]  # [d_model]\n\n    def steering_hook(activation, hook):\n        # Add scaled feature direction at all positions\n        activation += strength * feature_direction\n        return activation\n\n    # Generate with steering\n    output = model.generate(\n        tokens,\n        max_new_tokens=50,\n        fwd_hooks=[(\"blocks.8.hook_resid_pre\", steering_hook)]\n    )\n    return model.to_string(output[0])\n```\n\n### Feature Attribution\n\n```python\n# Which features most affect a specific output?\ntokens = model.to_tokens(\"The capital of France is\")\n_, cache = model.run_with_cache(tokens)\n\n# Get features at final position\nfeatures = sae.encode(cache[\"resid_pre\", 8])[0, -1]  # [d_sae]\n\n# Get logit attribution per feature\n# Feature contribution = feature_activation × decoder_weight × unembedding\nW_dec = sae.W_dec  # [d_sae, d_model]\nW_U = model.W_U    # [d_model, vocab]\n\n# Contribution to \"Paris\" logit\nparis_token = model.to_single_token(\" Paris\")\nfeature_contributions = features * (W_dec @ W_U[:, paris_token])\n\ntop_features = feature_contributions.topk(10)\nprint(\"Top features for 'Paris' prediction:\")\nfor idx, val in zip(top_features.indices, top_features.values):\n    print(f\"  Feature {idx.item()}: {val.item():.3f}\")\n```\n\n## Common Issues & Solutions\n\n### Issue: High dead feature ratio\n```python\n# WRONG: No warm-up, features die early\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=1e-4,\n    l1_warm_up_steps=0,  # Bad!\n)\n\n# RIGHT: Warm-up L1 penalty\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=8e-5,\n    l1_warm_up_steps=1000,  # Gradually increase\n    use_ghost_grads=True,   # Revive dead features\n)\n```\n\n### Issue: Poor reconstruction (low CE recovery)\n```python\n# Reduce sparsity penalty\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=5e-5,  # Lower = better reconstruction\n    d_sae=768 * 16,       # More capacity\n)\n```\n\n### Issue: Features not interpretable\n```python\n# Increase sparsity (higher L1)\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=1e-4,  # Higher = sparser, more interpretable\n)\n# Or use TopK architecture\ncfg = LanguageModelSAERunnerConfig(\n    architecture=\"topk\",\n    activation_fn_kwargs={\"k\": 50},  # Exactly 50 active features\n)\n```\n\n### Issue: Memory errors during training\n```python\ncfg = LanguageModelSAERunnerConfig(\n    train_batch_size_tokens=2048,  # Reduce batch size\n    store_batch_size_prompts=4,    # Fewer prompts in buffer\n    n_batches_in_buffer=8,         # Smaller activation buffer\n)\n```\n\n## Integration with Neuronpedia\n\nBrowse pre-trained SAE features at [neuronpedia.org](https:\u002F\u002Fneuronpedia.org):\n\n```python\n# Features are indexed by SAE ID\n# Example: gpt2-small layer 8 feature 1234\n# → neuronpedia.org\u002Fgpt2-small\u002F8-res-jb\u002F1234\n```\n\n## Key Classes Reference\n\n| Class | Purpose |\n|-------|---------|\n| `SAE` | Sparse Autoencoder model |\n| `LanguageModelSAERunnerConfig` | Training configuration |\n| `SAETrainingRunner` | Training loop manager |\n| `ActivationsStore` | Activation collection and batching |\n| `HookedSAETransformer` | TransformerLens + SAE integration |\n\n## Reference Documentation\n\nFor detailed API documentation, tutorials, and advanced usage, see the `references\u002F` folder:\n\n| File | Contents |\n|------|----------|\n| [references\u002FREADME.md](references\u002FREADME.md) | Overview and quick start guide |\n| [references\u002Fapi.md](references\u002Fapi.md) | Complete API reference for SAE, TrainingSAE, configurations |\n| [references\u002Ftutorials.md](references\u002Ftutorials.md) | Step-by-step tutorials for training, analysis, steering |\n\n## External Resources\n\n### Tutorials\n- [Basic Loading & Analysis](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens\u002Fblob\u002Fmain\u002Ftutorials\u002Fbasic_loading_and_analysing.ipynb)\n- [Training a Sparse Autoencoder](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens\u002Fblob\u002Fmain\u002Ftutorials\u002Ftraining_a_sparse_autoencoder.ipynb)\n- [ARENA SAE Curriculum](https:\u002F\u002Fwww.lesswrong.com\u002Fposts\u002FLnHowHgmrMbWtpkxx\u002Fintro-to-superposition-and-sparse-autoencoders-colab)\n\n### Papers\n- [Towards Monosemanticity](https:\u002F\u002Ftransformer-circuits.pub\u002F2023\u002Fmonosemantic-features) - Anthropic (2023)\n- [Scaling Monosemanticity](https:\u002F\u002Ftransformer-circuits.pub\u002F2024\u002Fscaling-monosemanticity\u002F) - Anthropic (2024)\n- [Sparse Autoencoders Find Highly Interpretable Features](https:\u002F\u002Farxiv.org\u002Fabs\u002F2309.08600) - Cunningham et al. (ICLR 2024)\n\n### Official Documentation\n- [SAELens Docs](https:\u002F\u002Fjbloomaus.github.io\u002FSAELens\u002F)\n- [Neuronpedia](https:\u002F\u002Fneuronpedia.org) - Feature browser\n\n## SAE Architectures\n\n| Architecture | Description | Use Case |\n|--------------|-------------|----------|\n| **Standard** | ReLU + L1 penalty | General purpose |\n| **Gated** | Learned gating mechanism | Better sparsity control |\n| **TopK** | Exactly K active features | Consistent sparsity |\n\n```python\n# TopK SAE (exactly 50 features active)\ncfg = LanguageModelSAERunnerConfig(\n    architecture=\"topk\",\n    activation_fn=\"topk\",\n    activation_fn_kwargs={\"k\": 50},\n)\n```\n","# SAELens: Sparse Autoencoders for Mechanistic Interpretability\n\nSAELens is the primary library for training and analyzing Sparse Autoencoders (SAEs) - a technique for decomposing polysemantic neural network activations into sparse, interpretable features. Based on Anthropic's groundbreaking research on monosemanticity.\n\n**GitHub**: [jbloomAus\u002FSAELens](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens) (1,100+ stars)\n\n## The Problem: Polysemanticity & Superposition\n\nIndividual neurons in neural networks are **polysemantic** - they activate in multiple, semantically distinct contexts. This happens because models use **superposition** to represent more features than they have neurons, making interpretability difficult.\n\n**SAEs solve this** by decomposing dense activations into sparse, monosemantic features - typically only a small number of features activate for any given input, and each feature corresponds to an interpretable concept.\n\n## When to Use SAELens\n\n**Use SAELens when you need to:**\n- Discover interpretable features in model activations\n- Understand what concepts a model has learned\n- Study superposition and feature geometry\n- Perform feature-based steering or ablation\n- Analyze safety-relevant features (deception, bias, harmful content)\n\n**Consider alternatives when:**\n- You need basic activation analysis → Use **TransformerLens** directly\n- You want causal intervention experiments → Use **pyvene** or **TransformerLens**\n- You need production steering → Consider direct activation engineering\n\n## Installation\n\n```bash\npip install sae-lens\n```\n\nRequirements: Python 3.10+, transformer-lens>=2.0.0\n\n## Core Concepts\n\n### What SAEs Learn\n\nSAEs are trained to reconstruct model activations through a sparse bottleneck:\n\n```\nInput Activation → Encoder → Sparse Features → Decoder → Reconstructed Activation\n    (d_model)       ↓        (d_sae >> d_model)    ↓         (d_model)\n                 sparsity                      reconstruction\n                 penalty                          loss\n```\n\n**Loss Function**: `MSE(original, reconstructed) + L1_coefficient × L1(features)`\n\n### Key Validation (Anthropic Research)\n\nIn \"Towards Monosemanticity\", human evaluators found **70% of SAE features genuinely interpretable**. Features discovered include:\n- DNA sequences, legal language, HTTP requests\n- Hebrew text, nutrition statements, code syntax\n- Sentiment, named entities, grammatical structures\n\n## Workflow 1: Loading and Analyzing Pre-trained SAEs\n\n### Step-by-Step\n\n```python\nfrom transformer_lens import HookedTransformer\nfrom sae_lens import SAE\n\n# 1. Load model and pre-trained SAE\nmodel = HookedTransformer.from_pretrained(\"gpt2-small\", device=\"cuda\")\nsae, cfg_dict, sparsity = SAE.from_pretrained(\n    release=\"gpt2-small-res-jb\",\n    sae_id=\"blocks.8.hook_resid_pre\",\n    device=\"cuda\"\n)\n\n# 2. Get model activations\ntokens = model.to_tokens(\"The capital of France is Paris\")\n_, cache = model.run_with_cache(tokens)\nactivations = cache[\"resid_pre\", 8]  # [batch, pos, d_model]\n\n# 3. Encode to SAE features\nsae_features = sae.encode(activations)  # [batch, pos, d_sae]\nprint(f\"Active features: {(sae_features > 0).sum()}\")\n\n# 4. Find top features for each position\nfor pos in range(tokens.shape[1]):\n    top_features = sae_features[0, pos].topk(5)\n    token = model.to_str_tokens(tokens[0, pos:pos+1])[0]\n    print(f\"Token '{token}': features {top_features.indices.tolist()}\")\n\n# 5. Reconstruct activations\nreconstructed = sae.decode(sae_features)\nreconstruction_error = (activations - reconstructed).norm()\n```\n\n### Available Pre-trained SAEs\n\n| Release | Model | Layers |\n|---------|-------|--------|\n| `gpt2-small-res-jb` | GPT-2 Small | Multiple residual streams |\n| `gemma-2b-res` | Gemma 2B | Residual streams |\n| Various on HuggingFace | Search tag `saelens` | Various |\n\n### Checklist\n- [ ] Load model with TransformerLens\n- [ ] Load matching SAE for target layer\n- [ ] Encode activations to sparse features\n- [ ] Identify top-activating features per token\n- [ ] Validate reconstruction quality\n\n## Workflow 2: Training a Custom SAE\n\n### Step-by-Step\n\n```python\nfrom sae_lens import SAE, LanguageModelSAERunnerConfig, SAETrainingRunner\n\n# 1. Configure training\ncfg = LanguageModelSAERunnerConfig(\n    # Model\n    model_name=\"gpt2-small\",\n    hook_name=\"blocks.8.hook_resid_pre\",\n    hook_layer=8,\n    d_in=768,  # Model dimension\n\n    # SAE architecture\n    architecture=\"standard\",  # or \"gated\", \"topk\"\n    d_sae=768 * 8,  # Expansion factor of 8\n    activation_fn=\"relu\",\n\n    # Training\n    lr=4e-4,\n    l1_coefficient=8e-5,  # Sparsity penalty\n    l1_warm_up_steps=1000,\n    train_batch_size_tokens=4096,\n    training_tokens=100_000_000,\n\n    # Data\n    dataset_path=\"monology\u002Fpile-uncopyrighted\",\n    context_size=128,\n\n    # Logging\n    log_to_wandb=True,\n    wandb_project=\"sae-training\",\n\n    # Checkpointing\n    checkpoint_path=\"checkpoints\",\n    n_checkpoints=5,\n)\n\n# 2. Train\ntrainer = SAETrainingRunner(cfg)\nsae = trainer.run()\n\n# 3. Evaluate\nprint(f\"L0 (avg active features): {trainer.metrics['l0']}\")\nprint(f\"CE Loss Recovered: {trainer.metrics['ce_loss_score']}\")\n```\n\n### Key Hyperparameters\n\n| Parameter | Typical Value | Effect |\n|-----------|---------------|--------|\n| `d_sae` | 4-16× d_model | More features, higher capacity |\n| `l1_coefficient` | 5e-5 to 1e-4 | Higher = sparser, less accurate |\n| `lr` | 1e-4 to 1e-3 | Standard optimizer LR |\n| `l1_warm_up_steps` | 500-2000 | Prevents early feature death |\n\n### Evaluation Metrics\n\n| Metric | Target | Meaning |\n|--------|--------|---------|\n| **L0** | 50-200 | Average active features per token |\n| **CE Loss Score** | 80-95% | Cross-entropy recovered vs original |\n| **Dead Features** | \u003C5% | Features that never activate |\n| **Explained Variance** | >90% | Reconstruction quality |\n\n### Checklist\n- [ ] Choose target layer and hook point\n- [ ] Set expansion factor (d_sae = 4-16× d_model)\n- [ ] Tune L1 coefficient for desired sparsity\n- [ ] Enable L1 warm-up to prevent dead features\n- [ ] Monitor metrics during training (W&B)\n- [ ] Validate L0 and CE loss recovery\n- [ ] Check dead feature ratio\n\n## Workflow 3: Feature Analysis and Steering\n\n### Analyzing Individual Features\n\n```python\nfrom transformer_lens import HookedTransformer\nfrom sae_lens import SAE\nimport torch\n\nmodel = HookedTransformer.from_pretrained(\"gpt2-small\", device=\"cuda\")\nsae, _, _ = SAE.from_pretrained(\n    release=\"gpt2-small-res-jb\",\n    sae_id=\"blocks.8.hook_resid_pre\",\n    device=\"cuda\"\n)\n\n# Find what activates a specific feature\nfeature_idx = 1234\ntest_texts = [\n    \"The scientist conducted an experiment\",\n    \"I love chocolate cake\",\n    \"The code compiles successfully\",\n    \"Paris is beautiful in spring\",\n]\n\nfor text in test_texts:\n    tokens = model.to_tokens(text)\n    _, cache = model.run_with_cache(tokens)\n    features = sae.encode(cache[\"resid_pre\", 8])\n    activation = features[0, :, feature_idx].max().item()\n    print(f\"{activation:.3f}: {text}\")\n```\n\n### Feature Steering\n\n```python\ndef steer_with_feature(model, sae, prompt, feature_idx, strength=5.0):\n    \"\"\"Add SAE feature direction to residual stream.\"\"\"\n    tokens = model.to_tokens(prompt)\n\n    # Get feature direction from decoder\n    feature_direction = sae.W_dec[feature_idx]  # [d_model]\n\n    def steering_hook(activation, hook):\n        # Add scaled feature direction at all positions\n        activation += strength * feature_direction\n        return activation\n\n    # Generate with steering\n    output = model.generate(\n        tokens,\n        max_new_tokens=50,\n        fwd_hooks=[(\"blocks.8.hook_resid_pre\", steering_hook)]\n    )\n    return model.to_string(output[0])\n```\n\n### Feature Attribution\n\n```python\n# Which features most affect a specific output?\ntokens = model.to_tokens(\"The capital of France is\")\n_, cache = model.run_with_cache(tokens)\n\n# Get features at final position\nfeatures = sae.encode(cache[\"resid_pre\", 8])[0, -1]  # [d_sae]\n\n# Get logit attribution per feature\n# Feature contribution = feature_activation × decoder_weight × unembedding\nW_dec = sae.W_dec  # [d_sae, d_model]\nW_U = model.W_U    # [d_model, vocab]\n\n# Contribution to \"Paris\" logit\nparis_token = model.to_single_token(\" Paris\")\nfeature_contributions = features * (W_dec @ W_U[:, paris_token])\n\ntop_features = feature_contributions.topk(10)\nprint(\"Top features for 'Paris' prediction:\")\nfor idx, val in zip(top_features.indices, top_features.values):\n    print(f\"  Feature {idx.item()}: {val.item():.3f}\")\n```\n\n## Common Issues & Solutions\n\n### Issue: High dead feature ratio\n```python\n# WRONG: No warm-up, features die early\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=1e-4,\n    l1_warm_up_steps=0,  # Bad!\n)\n\n# RIGHT: Warm-up L1 penalty\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=8e-5,\n    l1_warm_up_steps=1000,  # Gradually increase\n    use_ghost_grads=True,   # Revive dead features\n)\n```\n\n### Issue: Poor reconstruction (low CE recovery)\n```python\n# Reduce sparsity penalty\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=5e-5,  # Lower = better reconstruction\n    d_sae=768 * 16,       # More capacity\n)\n```\n\n### Issue: Features not interpretable\n```python\n# Increase sparsity (higher L1)\ncfg = LanguageModelSAERunnerConfig(\n    l1_coefficient=1e-4,  # Higher = sparser, more interpretable\n)\n# Or use TopK architecture\ncfg = LanguageModelSAERunnerConfig(\n    architecture=\"topk\",\n    activation_fn_kwargs={\"k\": 50},  # Exactly 50 active features\n)\n```\n\n### Issue: Memory errors during training\n```python\ncfg = LanguageModelSAERunnerConfig(\n    train_batch_size_tokens=2048,  # Reduce batch size\n    store_batch_size_prompts=4,    # Fewer prompts in buffer\n    n_batches_in_buffer=8,         # Smaller activation buffer\n)\n```\n\n## Integration with Neuronpedia\n\nBrowse pre-trained SAE features at [neuronpedia.org](https:\u002F\u002Fneuronpedia.org):\n\n```python\n# Features are indexed by SAE ID\n# Example: gpt2-small layer 8 feature 1234\n# → neuronpedia.org\u002Fgpt2-small\u002F8-res-jb\u002F1234\n```\n\n## Key Classes Reference\n\n| Class | Purpose |\n|-------|---------|\n| `SAE` | Sparse Autoencoder model |\n| `LanguageModelSAERunnerConfig` | Training configuration |\n| `SAETrainingRunner` | Training loop manager |\n| `ActivationsStore` | Activation collection and batching |\n| `HookedSAETransformer` | TransformerLens + SAE integration |\n\n## Reference Documentation\n\nFor detailed API documentation, tutorials, and advanced usage, see the `references\u002F` folder:\n\n| File | Contents |\n|------|----------|\n| [references\u002FREADME.md](references\u002FREADME.md) | Overview and quick start guide |\n| [references\u002Fapi.md](references\u002Fapi.md) | Complete API reference for SAE, TrainingSAE, configurations |\n| [references\u002Ftutorials.md](references\u002Ftutorials.md) | Step-by-step tutorials for training, analysis, steering |\n\n## External Resources\n\n### Tutorials\n- [Basic Loading & Analysis](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens\u002Fblob\u002Fmain\u002Ftutorials\u002Fbasic_loading_and_analysing.ipynb)\n- [Training a Sparse Autoencoder](https:\u002F\u002Fgithub.com\u002FjbloomAus\u002FSAELens\u002Fblob\u002Fmain\u002Ftutorials\u002Ftraining_a_sparse_autoencoder.ipynb)\n- [ARENA SAE Curriculum](https:\u002F\u002Fwww.lesswrong.com\u002Fposts\u002FLnHowHgmrMbWtpkxx\u002Fintro-to-superposition-and-sparse-autoencoders-colab)\n\n### Papers\n- [Towards Monosemanticity](https:\u002F\u002Ftransformer-circuits.pub\u002F2023\u002Fmonosemantic-features) - Anthropic (2023)\n- [Scaling Monosemanticity](https:\u002F\u002Ftransformer-circuits.pub\u002F2024\u002Fscaling-monosemanticity\u002F) - Anthropic (2024)\n- [Sparse Autoencoders Find Highly Interpretable Features](https:\u002F\u002Farxiv.org\u002Fabs\u002F2309.08600) - Cunningham et al. (ICLR 2024)\n\n### Official Documentation\n- [SAELens Docs](https:\u002F\u002Fjbloomaus.github.io\u002FSAELens\u002F)\n- [Neuronpedia](https:\u002F\u002Fneuronpedia.org) - Feature browser\n\n## SAE Architectures\n\n| Architecture | Description | Use Case |\n|--------------|-------------|----------|\n| **Standard** | ReLU + L1 penalty | General purpose |\n| **Gated** | Learned gating mechanism | Better sparsity control |\n| **TopK** | Exactly K active features | Consistent sparsity |\n\n```python\n# TopK SAE (exactly 50 features active)\ncfg = LanguageModelSAERunnerConfig(\n    architecture=\"topk\",\n    activation_fn=\"topk\",\n    activation_fn_kwargs={\"k\": 50},\n)\n```\n",{"name":5,"tags":49,"author":55,"license":15,"version":56,"category":34,"description":7,"dependencies":57},[50,51,52,53,54],"Sparse Autoencoders","SAE","Mechanistic Interpretability","Feature Discovery","Superposition","Orchestra Research","1.0.0",[58,59,60],"sae-lens>=6.0.0","transformer-lens>=2.0.0","torch>=2.0.0","main","0da4485785ee599388900be50db1635489d53056",".agents\u002Fskills\u002Fqc-saelens","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6","https:\u002F\u002Fdisha6.6.thenitishkr.in\u002F","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh","www.thenitishkr","thenitishkr | AI • Cyber-security • Research\r\n","2026-11-08 03:33:25",{"source":8,"skillName":5,"commands":71,"prompt":81,"zipAvailable":82},[72,75,78],{"tool":73,"command":74},"npx","npx skills add Tashima-Tarsh\u002FDisha6.6 --skill sparse-autoencoder-training",{"tool":76,"command":77},"bunx","bunx skills add Tashima-Tarsh\u002FDisha6.6 --skill sparse-autoencoder-training",{"tool":79,"command":80},"pnpm","pnpm dlx skills add Tashima-Tarsh\u002FDisha6.6 --skill sparse-autoencoder-training","安装技能，技能地址：https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fqc-saelens\u002FSKILL.md",true,[84,90,94],{"path":85,"resourceType":86,"resourceTypeDesc":87,"sizeBytes":88,"sourceHtmlUrl":89},"references\u002Fapi.md","REFERENCE","参考文档",6968,"https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fqc-saelens\u002Freferences\u002Fapi.md",{"path":91,"resourceType":86,"resourceTypeDesc":87,"sizeBytes":92,"sourceHtmlUrl":93},"references\u002FREADME.md",2155,"https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fqc-saelens\u002Freferences\u002FREADME.md",{"path":95,"resourceType":86,"resourceTypeDesc":87,"sizeBytes":96,"sourceHtmlUrl":97},"references\u002Ftutorials.md",9383,"https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fqc-saelens\u002Freferences\u002Ftutorials.md",[99,128,151,178,203,227],{"skillNo":100,"name":101,"nameZh":6,"description":102,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":103,"categories":104,"keywords":108,"publishedAt":44},"01M6QRD07D4TGNDK6VJ4EHF8BV","youtube-full","Use when the user needs YouTube transcripts, video search, channel browsing, playlist extraction, or content monitoring. Trigger phrases: 'get the transcript for', 'search YouTube for', 'what are the latest videos on', 'list this playlist', 'monitor this channel', or any request involving a YouTube URL, video ID, or @handle. Do NOT use for downloading video or audio files, YouTube engagement data (likes, comments), or private\u002Fage-restricted videos.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fyoutube-full\u002FSKILL.md",[105],{"categoryNo":106,"categoryName":107,"taxonomyType":21,"taxonomyTypeDesc":22},"01JBSEEDCAT000000000000016","图像与多媒体",[109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,28,125,126,127],"youtube full","youtube","full","transcript","search","monitoring","data","Video","Audio","list","files","do","get","age","trigger","URL","browsing","request","youtube transcripts",{"skillNo":129,"name":130,"nameZh":6,"description":131,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":132,"categories":133,"keywords":134,"publishedAt":44},"01M6QRCJ3112VYPA97YG7KGMC2","x-twitter-growth","X\u002FTwitter growth engine for building audience, crafting viral content, and analyzing engagement. Use when the user wants to grow on X\u002FTwitter, write tweets or threads, analyze their X profile, research competitors on X, plan a posting strategy, or optimize engagement. Complements social-content (generic multi-platform) with X-specific depth: algorithm mechanics, thread engineering, reply strategy, profile optimization, and competitive intelligence via web search.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fx-twitter-growth\u002FSKILL.md",[],[135,136,137,27,113,138,139,140,141,142,143,144,145,146,40,147,148,149,150,28],"twitter","x twitter growth","growth","content","engineering","plan","web search","competitors","analyze","engine","write","strategy","platform","grow","posting","competitive",{"skillNo":152,"name":153,"nameZh":6,"description":154,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":155,"categories":156,"keywords":160,"publishedAt":44},"01M6QRBN3EHQNJY42RERP7A149","write-a-skill","Create new agent skills with proper structure, progressive disclosure, and bundled resources. Use when user wants to create, write, build, or author a new skill.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fwrite-a-skill\u002FSKILL.md",[157],{"categoryNo":158,"categoryName":159,"taxonomyType":21,"taxonomyTypeDesc":22},"01JBSEEDCAT000000000000023","Skill与智能体开发",[161,145,162,163,164,165,166,167,40,168,169,61,170,171,172,173,174,175,176,177],"write a skill","github","create","https","productivity","matt pocock","direct","example","build","new skill","structure","new agent","resources","with","tree","progressive disclosure","author",{"skillNo":179,"name":180,"nameZh":6,"description":181,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":182,"categories":183,"keywords":184,"publishedAt":44},"01M6QRB6G8P33PNGAF9Y69EJ9T","wrap-up","Close out a launched Claude Managed Agent — recap every primitive the founder now owns, regenerate the single-file overview page, and suggest the next 1-2 upgrades. Use when the user says \"wrap up\", \"close this out\", \"what do I own now\", \"give me the summary\", \"recap the agent\", or when the orchestrator routes phase=wrap-up. primitives_inventory.py tables everything owned (agent, environment, session, memory, outcome, deployment); overview_page.py regenerates a self-contained .\u002Fmy-agent\u002Fagent-overview.html; upgrade_suggester.py ranks the next moves from recorded deferrals plus standing hardening steps. Companion to run-without-you; the last stop before phase=done.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fwrap-up\u002FSKILL.md",[],[185,186,187,188,189,190,191,192,193,40,194,120,195,196,197,198,199,200,201,202],"wrap up","up","wrap","gemini","deployment","run","file","hardening","closeout","stop","upgrade","founder","close","companion","you","tables","directions","phase",{"skillNo":204,"name":205,"nameZh":6,"description":206,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":207,"categories":208,"keywords":210,"publishedAt":44},"01M6QRA5AYC1RBFZ39GTWGS3N8","workflow-builder","Design and write deterministic multi-agent workflow scripts (.js files in .claude\u002Fworkflows\u002F) for Claude Code's Workflow tool. Use when a user wants to build, create, author, scaffold, or run a custom Claude Code workflow, orchestrate sub-agents (fan-out, pipeline, loop, judge-panel), or automate a repeatable multi-step task across fresh-context agents.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fworkflow-builder\u002FSKILL.md",[209],{"categoryNo":158,"categoryName":159,"taxonomyType":21,"taxonomyTypeDesc":22},[211,212,213,214,215,163,190,216,217,218,219,220,145,221,119,222,223,224,225,226],"workflow","workflow builder","builder","design","workflows","code","orchestrate","pipeline","loop","multi-agent","context","across","fresh","scripts","judge","claude code workflow",{"skillNo":228,"name":229,"nameZh":6,"description":230,"descriptionZh":6,"repositoryFullName":8,"ownerLogin":9,"ownerAvatarUrl":10,"ownerAccountNo":11,"ownerDisplayName":12,"repositoryNo":13,"starsCount":14,"licenseSpdxId":15,"licenseFileUrl":6,"sourceHtmlUrl":231,"categories":232,"keywords":233,"publishedAt":44},"01M6QR7QMCZESKQA0ERW1E657M","weekly-review","Use when someone wants to run a weekly review, close open loops, audit stalled projects and commitments, get their system back to trusted, restart a lapsed review habit, or says \"\u002Fcs:weekly-review\". Walks David Allen's three-phase loop — GET CLEAR, GET CURRENT, GET CREATIVE — with deterministic scripts that inventory open loops, gate the checklist with named gaps, and score commitment health 0-100.","https:\u002F\u002Fgithub.com\u002FTashima-Tarsh\u002FDisha6.6\u002Fblob\u002Fmain\u002F.agents\u002Fskills\u002Fweekly-review\u002FSKILL.md",[],[234,235,236,237,238,239,240,241,242,219,243,244,245,246,247,248,121,249,250,202],"review","weekly review","weekly","deterministic scripts","reflect","feeds","inventory","open","team","projects","project-management","scanner","conversation","back","project","sprint","cadence"]