diff --git a/CLAUDE.md b/CLAUDE.md
new file mode 100644
index 0000000..84a0515
--- /dev/null
+++ b/CLAUDE.md
@@ -0,0 +1,135 @@
+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Project Overview
+
+This repository contains the code and data for "An Accurate and Rapidly Calibrating Speech Neuroprosthesis" published in the New England Journal of Medicine (2024). It implements a brain-to-text system that converts neural signals from speech motor cortex into text using RNN models and n-gram language models.
+
+## Development Environment Setup
+
+### Main Environment (b2txt25)
+```bash
+./setup.sh
+conda activate b2txt25
+```
+
+### Language Model Environment (b2txt25_lm)
+```bash
+./setup_lm.sh
+conda activate b2txt25_lm
+```
+
+**Important**: The project requires two separate conda environments due to conflicting PyTorch versions:
+- `b2txt25`: PyTorch with CUDA 12.6 for model training/evaluation
+- `b2txt25_lm`: PyTorch 1.13.1 for Kaldi-based n-gram language models
+
+### Redis Setup
+Redis is required for inter-process communication. Install on Ubuntu:
+```bash
+curl -fsSL https://packages.redis.io/gpg | sudo gpg --dearmor -o /usr/share/keyrings/redis-archive-keyring.gpg
+echo "deb [signed-by=/usr/share/keyrings/redis-archive-keyring.gpg] https://packages.redis.io/deb $(lsb_release -cs) main" | sudo tee /etc/apt/sources.list.d/redis.list
+sudo apt-get update && sudo apt-get install redis
+sudo systemctl disable redis-server
+```
+
+## Architecture Overview
+
+### High-Level System Flow
+1. **Neural Data Input**: 512 features (2 per electrode × 256 electrodes) binned at 20ms resolution
+2. **RNN Model**: Converts neural features to phoneme logits via CTC loss
+3. **Language Model**: Decodes phoneme logits to words using n-gram models + OPT rescoring
+4. **Redis Communication**: Coordinates between RNN inference and language model processes
+
+### Key Components
+
+#### Model Training (`model_training/`)
+- **Core Script**: `train_model.py` (loads config from `rnn_args.yaml`)
+- **Model Architecture**: `rnn_model.py` - 5-layer GRU with 768 hidden units
+- **Trainer**: `rnn_trainer.py` - Custom PyTorch trainer with CTC loss
+- **Evaluation**: `evaluate_model.py` - Inference pipeline with Redis communication
+
+#### Language Model (`language_model/`)
+- **Standalone Server**: `language-model-standalone.py` - Redis-based LM server
+- **Kaldi Integration**: Uses custom C++ bindings for efficient n-gram decoding
+- **OPT Rescoring**: Facebook OPT 6.7B for language model rescoring
+- **Build System**: Complex CMake-based build for Kaldi/SRILM integration
+
+#### Utilities (`nejm_b2txt_utils/`)
+- **General Utils**: `general_utils.py` - Shared utility functions
+- **Package**: Installed via `setup.py` as `nejm_b2txt_utils`
+
+#### Analysis (`analyses/`)
+- **Jupyter Notebooks**: `figure_2.ipynb`, `figure_4.ipynb` for paper figures
+
+## Common Development Tasks
+
+### Training a Model
+```bash
+conda activate b2txt25
+cd model_training
+python train_model.py
+```
+
+### Running Evaluation Pipeline
+1. Start Redis server:
+   ```bash
+   redis-server
+   ```
+
+2. Start language model (separate terminal):
+   ```bash
+   conda activate b2txt25_lm
+   python language_model/language-model-standalone.py --lm_path language_model/pretrained_language_models/openwebtext_1gram_lm_sil --do_opt --nbest 100 --acoustic_scale 0.325 --blank_penalty 90 --alpha 0.55 --redis_ip localhost --gpu_number 0
+   ```
+
+3. Run evaluation (separate terminal):
+   ```bash
+   conda activate b2txt25
+   cd model_training
+   python evaluate_model.py --model_path ../data/t15_pretrained_rnn_baseline --data_dir ../data/hdf5_data_final --eval_type test --gpu_number 1
+   ```
+
+4. Shutdown Redis:
+   ```bash
+   redis-cli shutdown
+   ```
+
+### Building Language Model from Scratch
+```bash
+# Build SRILM (in language_model/srilm-1.7.3/)
+export SRILM=$PWD
+make MAKE_PIC=yes World
+
+# Build Kaldi components (in language_model/runtime/server/x86/)
+mkdir build && cd build
+cmake .. && make -j8
+```
+
+## Data Structure
+
+### Neural Data Format
+- **File Type**: HDF5 files in `data/hdf5_data_final/`
+- **Features**: 512 neural features per 20ms bin:
+  - 0-64: ventral 6v threshold crossings
+  - 65-128: area 4 threshold crossings
+  - 129-192: 55b threshold crossings
+  - 193-256: dorsal 6v threshold crossings
+  - 257-320: ventral 6v spike band power
+  - 321-384: area 4 spike band power
+  - 385-448: 55b spike band power
+  - 449-512: dorsal 6v spike band power
+
+### Data Loading
+Use `load_h5py_file()` in `model_training/evaluate_model_helpers.py` as reference for HDF5 data loading.
+
+## Important Notes
+
+- **GPU Requirements**: OPT 6.7B requires ~12.4GB VRAM; RTX 4090s recommended
+- **Memory Requirements**: 3-gram LM needs ~60GB RAM, 5-gram needs ~300GB RAM
+- **Environment Isolation**: Always use correct conda environment for each component
+- **Redis Dependency**: Many scripts require Redis server to be running
+- **Build Dependencies**: CMake ≥3.14 and GCC ≥10.1 required for language model builds
+
+## Competition Context
+This codebase also serves as baseline for the Brain-to-Text '25 Competition on Kaggle, providing reference implementations for neural signal decoding.
\ No newline at end of file