🐱 FafyCat - Local-First Transaction Categorization

FafyCat is a privacy-focused financial transaction categorization tool that uses machine learning to automatically organize your banking data with >90% accuracy. All processing happens locally on your device - no cloud services, no data sharing.

Import bank CSVs, let the local model predict categories, review the uncertain cases, and explore the results.

✨ Key Features

• 🤖 Smart Categorization: Machine learning automatically categorizes transactions with high accuracy
• 🔒 Privacy First: All data stays on your device - no external APIs or cloud services
• 📊 Intelligent Review: Active learning reduces manual work by 70-90%
• 🏪 Merchant Memory: Learns from your patterns to improve over time
• 📈 Export Ready: Multiple export formats for your favorite analysis tools
• ⚡ Fast & Efficient: Process thousands of transactions in seconds

🚀 Quick Start

Prerequisites

• Python 3.13 or later
• uv package manager https://docs.astral.sh/uv/getting-started/installation/

Installation

1. Install with uv

   uv tool install git+https://github.com/davidchris/fafycat

2. Or clone for development

   git clone https://github.com/davidchris/fafycat.git
   cd fafycat
   uv sync

3. Configure environment (optional)

   cp .env.example .env
   # Edit .env only if you want to override the defaults

4. Start the application

   # Start the packaged app
   fafycat serve
   
   # Development mode with sample data and hot reload
   fafycat serve --dev
   
   # If developing from a cloned checkout
   uv run fafycat serve --dev

5. Open your browser

   • Development: http://localhost:8001
   • Production: http://localhost:8000

📋 Getting Started Guide

First Time Setup

1. Import Your Data

   • Navigate to the Import page
   • Upload your bank transaction CSV files
   • The system auto-detects column formats

2. Review & Categorize

   • Go to the Review page
   • Correct any miscategorized transactions
   • The system learns from your corrections

3. Train the Model

   • Visit Settings → Train Model
   • Click "Train ML Model Now"
   • Training takes seconds to minutes

4. Enjoy Automation

   • Future imports will be auto-categorized
   • Only review uncertain predictions
   • Export data for analysis

Using Labeled Historical Data

If you have previously categorized transactions:

# Import your labeled data
uv run python scripts/import_labeled_data.py --data-path /path/to/your/data

# Or use the reset script for a fresh start
uv run python scripts/reset_and_import.py --labeled-data-path /path/to/your/data --train-model

Where do I get my banking transactions from?

• I'm getting mine via the MoneyMoney App.

🏗️ Architecture

┌─────────────────┐
│   CSV Import    │ → Flexible format detection
└────────┬────────┘
         │
         ▼
┌─────────────────┐     ┌──────────────────┐
│ Feature Extract │────▶│  ML Prediction   │
│  - Merchants    │     │  - LightGBM      │
│  - Amounts      │     │  - Naive Bayes   │
│  - Patterns     │     │  - Ensemble      │
└─────────────────┘     └──────────────────┘
                                 │
                                 ▼
                        ┌──────────────────┐
                        │   Review UI      │
                        │  Active Learning │
                        └──────────────────┘
                                 │
                                 ▼
                        ┌──────────────────┐
                        │   Data Export    │
                        │ CSV/Excel/JSON   │
                        └──────────────────┘

📊 Supported CSV Formats

FafyCat automatically detects and handles various banking export formats:

• Date: Various formats (DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD)
• Amount: Positive/negative or separate debit/credit columns
• Description: Transaction details and merchant names
• Category: If present, used for training

Common bank formats supported:

• German banks (Sparkasse, DKB, etc.)
• US banks (Chase, Bank of America, etc.)
• UK banks (Barclays, HSBC, etc.)
• Generic CSV exports

🎯 How It Works

Smart Learning System

1. Initial Training: Learn from your categorized transactions
2. Prediction: Automatically categorize new transactions
3. Active Learning: Intelligently select which transactions need review
4. Continuous Improvement: Learn from corrections over time

Privacy & Security

• Local Processing: All ML models run on your device
• No Cloud Services: Zero external API calls
• Your Data: You own and control all your financial data
• Open Source: Fully auditable codebase

🛠️ Configuration

Environment Variables

Create a .env file only if you want to override the default user-data location:

# Data defaults to your platform user-data directory
# Override only if you want a custom location
FAFYCAT_DATA_DIR=/path/to/fafycat-data
FAFYCAT_EXPORT_DIR=/path/to/fafycat-data/exports
FAFYCAT_MODEL_DIR=/path/to/fafycat-data/models

# Optional explicit database override
FAFYCAT_DB_URL=sqlite:////path/to/fafycat-data/fafycat.db

# Server settings
FAFYCAT_DEV_PORT=8001
FAFYCAT_PROD_PORT=8000
FAFYCAT_HOST=127.0.0.1

Database Management

• Default: Uses your platform user-data directory
• Development: fafycat serve --dev seeds synthetic test data
• Custom: Set FAFYCAT_DB_URL or pass --data-dir

📈 Performance

• Accuracy: >90% correct categorization
• Speed: <100ms per transaction
• Scale: Handles 100,000+ transactions
• Efficiency: 70-90% reduction in manual review

🔧 Development

Running Tests

uv run pytest

Code Quality

# Linting
uvx ruff check --fix

# Formatting
uvx ruff format

# Type checking
uvx ty check

API Documentation

• FastAPI docs: http://localhost:8000/docs
• OpenAPI schema: http://localhost:8000/openapi.json

📦 Project Layout

All shipped application code lives under src/fafycat/:

• src/fafycat/app.py for the FastAPI app factory
• src/fafycat/cli.py for the packaged CLI
• src/fafycat/api/ for API routes and services
• src/fafycat/web/ for HTML routes, pages, and components
• src/fafycat/core/ for config, database, and shared models
• src/fafycat/data/ for CSV processing
• src/fafycat/ml/ for the ML pipeline
• src/fafycat/static/ for packaged static assets

🤝 Contributing

tbd.

📄 License

This project is licensed under the Apache License 2.0 - see the LICENSE file for details.

🙏 Acknowledgments

• Built with FastAPI, FastHTML, and scikit-learn
• Inspired by the need for privacy-preserving financial tools

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Note: FafyCat is designed for personal use. Always verify categorizations for important financial decisions.