prototype

name	prototype
description	Use this skill when the user wants to prototype an idea, sanity-check a data model or state machine, mock up a UI, explore design options, or try several approaches before committing — even if they just say "let me play with it" or "try a few designs". Creates a runnable throwable that lets the user interact with the design before implementation.

Prototype

A prototype is throwaway code that answers a question. The question decides the shape.

Pick a branch

Identify which question is being answered — from the user's prompt, the surrounding code, or by asking if the user is around:

• "Does this logic / state model feel right?" → LOGIC.md. Build a tiny interactive terminal app that pushes the state machine through cases that are hard to reason about on paper.
• "What should this look like?" → UI.md. Generate several radically different UI variations in an ignored fixture host, switchable via a URL search param and a floating bottom bar.

The two branches produce very different artifacts — getting this wrong wastes the whole prototype. If the question is genuinely ambiguous and the user isn't reachable, default to whichever branch better matches the surrounding code (a backend module → logic; a page or component → UI) and state the assumption at the top of the prototype.

Mandatory location and launch contract

1. Write prototypes only under the ignored root: prototypes/<kebab-case-slug>/.

   • Slugs use lowercase letters/numbers separated by single dashes, e.g. plan-review-toolbar.
   • Before writing executable files, run git check-ignore prototypes/<slug>/ and stop if it is not ignored.
   • Never add prototype imports, routes, switchers, CSS, or marker comments under src/ or another tracked production directory.

2. Use one local folder shape:

   • README.md — question, assumptions, run command, and eventual answer.
   • project-native local task config — deno.json in RunWield, package.json in npm projects, Makefile/justfile where that is the existing convention.
   • source files for the UI or logic branch.

3. Launch with one command. In RunWield, create a local deno.json with a dev task and run:

   deno task prototype <slug>
   

   In other projects, use the equivalent committed generic launcher or document the project-native command in the prototype README; do not add a new production-root task per prototype.

Rules that apply to both

1. Throwaway from day one, and clearly marked as such. The prototype root is ignored and local. Keep context in its README, not by placing code next to production modules.
2. One command to run. The user must be able to start it without remembering internal file paths.
3. No persistence by default. State lives in memory. Persistence is the thing the prototype is checking, not something it should depend on. If the question explicitly involves a database, hit a scratch DB or a local file with a clear "PROTOTYPE — wipe me" name under the ignored prototype root.
4. Skip the polish. No tests, no error handling beyond what makes the prototype runnable, no abstractions. The point is to learn something fast and then delete it.
5. Surface the state. After every action (logic) or on every variant switch (UI), print or render the full relevant state so the user can see what changed.
6. Delete or absorb when done. When the prototype has answered its question, either delete it or fold the validated decision into the real code — don't leave it rotting in the repo.

When done

The answer is the only thing worth keeping from a prototype. Capture it somewhere durable (Plan/PRD/ADR, issue, commit message, or README.md/NOTES.md under the ignored prototype until the user confirms the verdict). Then delete or ignore the executable prototype artifacts. Do not force-add prototype code to share it.