Prototype
A prototype is throwaway code that answers a question. The question decides the shape.
Mutation boundary
Create prototypes outside the project repository by default, using the current Codex task's work directory or another temporary location. If answering the question genuinely requires integration with project code, first show the exact paths that would be added or changed and obtain explicit approval. Never create a branch, commit, push, open an issue or pull request, or modify shared services unless the user separately requests that action.
Pick a branch
Identify which question is being answered, using 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 single shareable HTML file (free-play buttons plus tabbed guided walkthroughs) that pushes the state machine through cases that are hard to reason about on paper, and that a non-developer can drive.
- "What should this look like?" → UI.md. Generate several radically different UI variations on a single route, switchable via a URL search param and a floating bottom bar.
The two branches produce very different artifacts, so 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.
Rules that apply to both
- Throwaway from day one, and clearly marked as such. Keep it outside the repository unless the user approves listed project paths. If approved for project integration, name it so a casual reader can see it is a prototype and obey the project's routing conventions.
- Trivial to run. A UI prototype starts from one command in the project's task runner:
pnpm <name>, python <path>, bun <path>, etc. A logic demo is a single HTML file the user double-clicks. Either way, no thinking required to start it.
- 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.
- Skip the polish. No tests, no error handling beyond what makes the prototype runnable, no abstractions. The point is to learn something fast.
- 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.
- Capture the answer, not repository history. Report the verdict and the question it settled in chat. Preserve an artifact only at a user-approved path. Do not fold decisions into production code or create a branch, issue, or commit unless explicitly requested.
1---2name: prototype3description: Build a throwaway prototype to answer a design question. Use when the user wants to sanity-check whether a state model or logic feels right, or explore what a UI should look like.4---56# Prototype78A prototype is **throwaway code that answers a question**. The question decides the shape.910## Mutation boundary1112Create prototypes outside the project repository by default, using the current Codex task's work directory or another temporary location. If answering the question genuinely requires integration with project code, first show the exact paths that would be added or changed and obtain explicit approval. Never create a branch, commit, push, open an issue or pull request, or modify shared services unless the user separately requests that action.1314## Pick a branch1516Identify which question is being answered, using the user's prompt, the surrounding code, or by asking if the user is around:1718- **"Does this logic / state model feel right?"** → [LOGIC.md](LOGIC.md). Build a single shareable HTML file (free-play buttons plus tabbed guided walkthroughs) that pushes the state machine through cases that are hard to reason about on paper, and that a non-developer can drive.19- **"What should this look like?"** → [UI.md](UI.md). Generate several radically different UI variations on a single route, switchable via a URL search param and a floating bottom bar.2021The two branches produce very different artifacts, so 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.2223## Rules that apply to both24251. **Throwaway from day one, and clearly marked as such.** Keep it outside the repository unless the user approves listed project paths. If approved for project integration, name it so a casual reader can see it is a prototype and obey the project's routing conventions.262. **Trivial to run.** A UI prototype starts from one command in the project's task runner: `pnpm <name>`, `python <path>`, `bun <path>`, etc. A logic demo is a single HTML file the user double-clicks. Either way, no thinking required to start it.273. **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.284. **Skip the polish.** No tests, no error handling beyond what makes the prototype _runnable_, no abstractions. The point is to learn something fast.295. **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.306. **Capture the answer, not repository history.** Report the verdict and the question it settled in chat. Preserve an artifact only at a user-approved path. Do not fold decisions into production code or create a branch, issue, or commit unless explicitly requested.
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