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7. Defensive rule writing (mental model)

File: 02_core_concepts/defensive_rules.md

This introduces principles, not syntax:

  • Assume parameters are missing
  • Assume bindings are wrong
  • Assume users did something unexpected
  • Never trust data without checking existence

This sets up later chapters on shared parameters perfectly.

What this chapter unlocks later

After 02_core_concepts, users are ready for:

  • 03_filtering_patterns
  • 04_shared_parameters
  • 05_validation_patterns
  • 06_real_world_rules

Without this chapter, those become copy-paste exercises.