Prototype

Prototype one uncertain decision

Use a prototype to answer a named question, not to start implementation early. If the decision is already settled, return to the calling workflow and build the real vertical slice instead.

Use /design-prototype when the question is visual layout, hierarchy or a user-flow sketch. This skill exercises behavior and contracts; a visual preview alone does not prove a state machine or failure-handling rule.

Frame the experiment

1. State the question, competing hypotheses, and the observation that would distinguish them. If the choice is user-owned, use /grilling first.
2. Inspect the repository for the current language, framework, test seams, and existing spike conventions. Do not assume a stack or invent a parallel project layout.
3. Define a strict time, file, and side-effect boundary. Use synthetic data and do not contact production systems or external services merely to increase fidelity.

Useful shapes include:

• a small interactive runner for a data model or state machine;
• minimal request, response, and error types for an interface contract;
• a pure function over an ordered event sequence for retry, replay, idempotency, or partial-failure behavior;
• two or three deliberately different implementations behind the same tiny interface when the trade-off is the question.

Build for learning

• Keep the experimental shell separate from the behavior under test.
• Make the relevant state, output, and failures visible after each action.
• Provide one documented command that reproduces the experiment.
• Prefer the repository's existing test/runtime tooling; do not add a durable dependency for a disposable experiment without explicit approval.
• Label every artifact as a prototype and keep it away from production entry points, deployment inputs, and real data.

Pause when the prototype exposes a new product, architecture, security, or scope decision. Use /architecture-review for architecture boundaries, including when the decision depends on Nav or NAIS. Use /domain-modeling for qualifying durable decisions within the active task's documented-work boundary; preserve its eligibility and authorization gate.

Close the experiment

Demonstrate the exact command and observations, then record:

• the question answered;
• what the evidence supports and does not support;
• the decision or remaining alternatives;
• which part, if any, is suitable to reimplement in production.

Delete the prototype after the result is captured, unless the user explicitly chooses to retain it as a clearly marked task artifact. Never promote the throwaway shell directly to production. Return the conclusion to the calling workflow so production implementation and verification start from a clean contract.