context-engineering-intro: Instructions file for Claude Code

🔄 Project Awareness & Context

• Always read PLANNING.md at the start of a new conversation to understand the project's architecture, goals, style, and constraints.
• Check TASK.md before starting a new task. If the task isn’t listed, add it with a brief description and today's date.
• Use consistent naming conventions, file structure, and architecture patterns as described in PLANNING.md.
• Use venv_linux (the virtual environment) whenever executing Python commands, including for unit tests.

🧱 Code Structure & Modularity

• Never create a file longer than 500 lines of code. If a file approaches this limit, refactor by splitting it into modules or helper files.
• Organize code into clearly separated modules, grouped by feature or responsibility. For agents this looks like:
  • agent.py - Main agent definition and execution logic
  • tools.py - Tool functions used by the agent
  • prompts.py - System prompts
• Use clear, consistent imports (prefer relative imports within packages).
• Use clear, consistent imports (prefer relative imports within packages).
• Use python_dotenv and load_env() for environment variables.

🧪 Testing & Reliability

• Always create Pytest unit tests for new features (functions, classes, routes, etc).
• After updating any logic, check whether existing unit tests need to be updated. If so, do it.
• Tests should live in a /tests folder mirroring the main app structure.
  • Include at least:
    • 1 test for expected use
    • 1 edge case
    • 1 failure case

✅ Task Completion

• Mark completed tasks in TASK.md immediately after finishing them.
• Add new sub-tasks or TODOs discovered during development to TASK.md under a “Discovered During Work” section.

📎 Style & Conventions

• Use Python as the primary language.
• Follow PEP8, use type hints, and format with black.
• Use pydantic for data validation.
• Use FastAPI for APIs and SQLAlchemy or SQLModel for ORM if applicable.
• Write docstrings for every function using the Google style:

  def example():
      """
      Brief summary.
  
      Args:
          param1 (type): Description.
  
      Returns:
          type: Description.
      """