Fail Fast

Surface problems at the earliest, cheapest, most informative moment: compile > startup > request boundary > deep in runtime.

Rules for agents

• Validate inputs at the system boundary; trust them inside.
• Validate configuration and required secrets at startup, not on first use.
• Crash on programmer errors (broken invariants, impossible states). Handle expected operational errors (network, bad user input) explicitly.
• Never swallow exceptions. No empty catch, no bare except: pass, no defaulting away a failure.
• Prefer types and non-nullable fields that make invalid states unrepresentable.
• Error messages must name what failed, the value seen, and what was expected.
• Assert invariants where they are established, not where they are read.

Anti-pattern

Defensive fallbacks that hide bugs — returning empty lists, null-coalescing to zero, try/except around the whole function. These turn a loud failure into silent corruption.

Smells

except Exception: pass, ?? 0 on a required value, errors logged and ignored, a bug found three layers away from its cause.