Prototype evidence

This page orients. The canonical contract agents load is skills/plan-work/references/prototypes.md.

A prototype exists to settle a decision.

Build the smallest comparison that makes the contested behavior observable. Record the question, stable artifact, how it was exercised, the observation, the developer's decision and rationale, and open uncertainty.

Keep observed behavior separate from judgment. Keep the artifact inspectable while the decision depends on it. Frontend prototypes also follow Frontend mockups.

When to prototype

Use an experiment when an unresolved assumption could change the solution and observation is cheaper or more decisive than further reading. Technical examples include transaction behavior, integration limits, and performance; UI alternatives may need the developer to try them. Skip experiments for clear routine tasks or questions settled by existing evidence.

Announce the question, artifact, decisive observation, and bounded effort budget. Isolated local experiments may run within existing planning or implementation authority. Stop when the question is settled or the budget expires; an inconclusive run leaves the decision open. Keep experimental code outside production paths and use normal delivery review before promoting it. Product preferences still require the developer's judgment.