Installation

Installation

Python library (required)

pip install openjck

Alternative Python installation with built-in server:

pip install "openjck[server]"

npm CLI (recommended)

# Always get the latest version without installation
npx openjck

# Or install globally for frequent use
npm install -g openjck

Verify both installations

Check Python package version:

python -c "import openjck; print(openjck.__version__)"

Check npm CLI version:

npx openjck --version

Troubleshooting table

Problem	Fix
Port 7823 in use → already running, open browser directly	The UI server is already running. Simply open http://localhost:7823 in your browser
No traces found → check ~/.openjck/traces/ exists	Ensure your agent code ran successfully and generated traces. Check the directory exists and contains .json files
ModuleNotFoundError → pip install in the right venv	Make sure you’re using the same Python environment where you installed openjck
Python too old → pyenv install 3.11	OpenJCK requires Python 3.10+. Use pyenv or similar to install a supported version

Directory Structure

After running your first traced agent, you’ll see:

~/.openjck/
└── traces/
    ├── a3f9c1b2.json
    ├── b4d0e2c3.json
    └── ...

Each JSON file contains a complete trace of one agent run.