Module 04 Summary

What this module established

Routers read explicit state fields and return a node name - if a router cannot be written as a truth table over named fields, the state design is the problem. Every node that can raise must catch into an error field, because an uncaught exception discards the state of the entire run, including work a human already reviewed.

Carry forward

• A safe retry needs three things together: a counter in state, a ceiling in the router, and a give-up node distinct from success.
• Only retry failures that could plausibly succeed next time. A validation error fails identically three times.
• Measure branch coverage over router destinations, not lines. The untested branch is reliably the error path.

Before moving on

Move on when every router reads named fields, every branch including the error path has a test asserting which branch ran, and the dead-end check passes.

Mark complete