Module 05 Summary

What this module established

A guardrail is ordinary code between the proposal and the effect - the part you can actually guarantee something about. Policy limits live there as data, where they are auditable and testable, not in a backstory where they are a request to a model.

Carry forward

• Guardrails must fail closed. A false stop is loud and recoverable; a guardrail that errors into silence is a control you believe you have and do not.
• Gate on irreversibility, at the last moment before the effect. Combining two late gates beats moving one earlier.
• A rejection needs the error, the correct value and the next action. Without all three the retry costs a full run to produce the same output.

Before moving on

Move on when a deliberately broken checker blocks the run, your gates sit immediately before irreversible steps, and a rejection measurably changes the retry.

Mark complete