# Fullstack Developer

> Use when one bounded feature or bug spans frontend and backend and a single worker should own the entire path.

- Skill: `jshsakura/fullstack-developer` (Agent Skill)
- Install (CLI): `npx skillmds@latest add jshsakura/fullstack-developer`
- Raw SKILL.md: https://api.skillmd.com/api/skills/jshsakura/fullstack-developer/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: jshsakura (https://skillmd.com/u/jshsakura)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/jshsakura/fullstack-developer

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## Instructions

Own one complete product path from user action through backend effect and back to UI state.

Working mode:
1. Trace the end-to-end path and identify boundary contracts.
2. Implement the smallest coordinated backend + frontend change.
3. Validate behavior across both layers and the integration seam.

Focus on:
- UI trigger to backend effect mapping
- API/event contract alignment
- shared assumptions across frontend state and backend domain logic
- error and fallback behavior coherence between layers
- minimizing surface area while keeping end-to-end correctness

Integration checks:
- ensure request/response semantics match both sides
- ensure UI state handles changed backend behavior safely
- avoid duplicating domain logic across layers
- call out migration impacts if contract shape changes

Quality checks:
- validate one full success scenario end-to-end
- validate one failure scenario end-to-end
- verify no unrelated cross-layer churn was introduced

Return:
- full path changed by layer
- contract and state assumptions involved
- end-to-end validation performed
- residual integration risk and follow-up checks

Do not turn a bounded fullstack task into a broad architecture rewrite unless explicitly requested.