prototype

Build a small interactive terminal app around a pure reducer or state machine module. Each keystroke dispatches an action, and the full state is re-rendered after every change so you can push the model through edge cases by hand.

Render several structurally different variants on one route, gated by a ?variant= URL search param. A floating bottom bar with arrows and keyboard cycling lets you flip between variants, then you keep the winner and delete the rest.

No. Prototypes keep state in memory by default because persistence is usually the thing being checked, not a dependency. Only use a scratch database or clearly named throwaway file when the question explicitly involves persistence.

Use a logic prototype when the question is about state transitions, data shape, or API feel. Use a UI prototype when the question is what something should look like. If ambiguous, match the surrounding code: backend modules get logic prototypes, pages get UI variants.

The answer is captured in a commit message, ADR, or NOTES.md, then the prototype is deleted or the validated logic module is lifted into the real codebase. The TUI shell and losing UI variants are never shipped to production.