{
  "instruction": "Use application factory pattern with create_app(), not module-level app",
  "relevant_when": "Agent builds or scaffolds a Flask application",
  "context": "Flask apps must use a create_app() factory function in app/__init__.py. The factory imports blueprints and extensions inside the function body to avoid circular imports, accepts a config parameter for testing/dev/prod, and never calls app.run() inside itself.",
  "sources": [
    {
      "type": "file",
      "filename": "skills/flask-best-practices/SKILL.md",
      "tile": "tessl-labs/flask-best-practices@0.2.0"
    }
  ],
  "checklist": [
    {
      "name": "create-app-factory",
      "rule": "Agent defines a create_app() function that creates and returns a Flask app instance -- not a module-level `app = Flask(__name__)` with routes defined on it",
      "relevant_when": "Agent sets up a Flask application"
    },
    {
      "name": "factory-in-init",
      "rule": "The create_app() function lives in app/__init__.py (not in run.py or a random module)",
      "relevant_when": "Agent creates the Flask application entry point"
    },
    {
      "name": "imports-inside-factory",
      "rule": "Blueprints and extensions are imported inside create_app(), not at the top of the module",
      "relevant_when": "Agent registers blueprints or extensions in the factory"
    },
    {
      "name": "config-parameter",
      "rule": "create_app() accepts a configuration parameter (config name, dict, or object) to support different environments (testing, development, production)",
      "relevant_when": "Agent defines the create_app() function signature"
    },
    {
      "name": "no-app-run-in-factory",
      "rule": "create_app() does NOT call app.run() -- the caller (run.py, WSGI server, or test fixture) decides how to run",
      "relevant_when": "Agent implements the create_app() function"
    }
  ]
}