| name | create-prototype |
| description | Implements a single user story from the PRD: writes code and tests, follows project conventions. Invoked by: nvst create prototype. |
| user-invocable | true |
Implement User Story
Implement the provided user story by writing production code and tests that satisfy all acceptance criteria, following the project's conventions and architecture.
The Job
- Read the user story and its acceptance criteria carefully.
- Review the project context to understand conventions, tech stack, testing strategy, and module structure.
- Plan the implementation: identify which files to create or modify, what tests to write, and how the change fits into the existing architecture.
- Implement the user story:
- Write production code that satisfies every acceptance criterion.
- Write tests that verify each acceptance criterion (follow the testing strategy from the project context).
- Follow all naming conventions, code standards, and forbidden patterns from the project context.
- Verify your work:
- Ensure the code compiles / type-checks without errors.
- Run any quality checks defined in the project context.
- Fix any issues before finishing.
- Do not commit — the calling command handles git commits.
Inputs
| Source | Used for |
|---|
user_story (context variable) | The user story JSON with id, title, description, and acceptanceCriteria |
project_context (context variable) | Project conventions, tech stack, code standards, testing strategy, and architecture |
iteration (context variable) | Current iteration number for file naming and context |
Standalone Fallback
When user_story or iteration are not injected as context variables, resolve them using the following lookup order before asking the user:
- Injected context variable — use directly if present.
state.json — read .agents/state.json (if it exists) to obtain current_iteration.- Artifact files — using the resolved iteration, look for:
.agents/flow/it_{iteration}_PRD.json (preferred) — read the userStories array and present the available stories to the user, asking which one to implement..agents/flow/it_{iteration}_product-requirement-document.md (fallback) — read the file, identify the user stories listed, and ask the user which story to implement.
- Ask user — only if neither
state.json nor any PRD artifact can be found, ask the user to provide the 6-digit iteration number (e.g. 000037). Once the iteration is known, retry step 3.
UI / Frontend Stories
Before implementation, detect whether this is a UI task.
- Consider it a UI task when the user story description or acceptance criteria contain keywords such as:
UI, interface, page, component, visual, button, form, layout, style, or frontend.
- If it is a UI task, apply these Impeccable skills in this exact order before finishing implementation:
frontend-design — set design direction and aesthetics.harden — handle UI edge cases and resilience.polish — run a final quality and refinement pass.
- Use these skills as guidance for the implementation you are already making in this story. Do not edit the Impeccable skill files themselves.
Rules
- One story at a time. Implement only the user story provided — do not implement other stories or make unrelated changes.
- Follow conventions exactly. Use the naming, formatting, error handling, and module organisation patterns from the project context.
- Test every acceptance criterion. Each AC should have at least one corresponding test assertion.
- No new dependencies unless the acceptance criteria explicitly require them.
- Do not modify state files. Do not touch
.agents/state.json or progress files — the calling command manages those.
- Do not commit. The calling command will commit after verifying quality checks pass.
- Keep changes minimal. Only modify files necessary to implement the user story. Do not refactor unrelated code.
Output
The output is the set of file changes (new files created, existing files modified) in the working tree. There is no document to produce — the code and tests are the deliverable.
Checklist
Before finishing:
