The Codex is a set of principles and guidelines for development of software and services at ECMWF. It is a snapshot of our current best practices and procedures. It is designed to change, via pull request and discussion.

• Principles — including the Code of Conduct and the Open Source Principles
• Architectural Decision Records (ADR)
• MARS Language Decision Records
• Repository Structure
• Project Maturity
• ECMWF Software EnginE (ESEE)
• Guidelines — branching, pull requests, testing, containerisation, observability, external contributions, continuous software delivery, AI contributions, and security vulnerability disclosure
• Languages
• Legal
• Documentation and Training
• Contributing to External Projects
• Software Management Plan
• Agent Skills