| name | fullstack-webapp |
| description | Use when building a full-stack web application from scratch or adding major features — assembles architect, frontend-dev, backend-dev, qa-engineer, and devops-engineer to deliver complete code, tests, and deployment setup. Covers React/Next.js + Node.js/Python backends, PostgreSQL/MongoDB databases, and Vercel/AWS/Railway deployment. Does NOT cover mobile apps (React Native/Flutter), desktop apps, game development, or ML/AI model training. Also triggers on: re-run, update, revise, supplement. |
| metadata | {"category":"harness","harness":"16-fullstack-webapp","agent_type":"general-purpose"} |
Fullstack Web App — Full-Stack Development Pipeline
An agent team collaborates to develop web apps through requirements → design → frontend → backend → testing → deployment.
Execution Mode
File-Bus Team — Agents communicate via _workspace/messages/, orchestrator sequences execution.
Agent Composition
| Agent | File | Role | Type |
|---|
| architect | agents/architect.md | Requirements, architecture, DB, API design | general-purpose |
| frontend-dev | agents/frontend-dev.md | React/Next.js frontend implementation | general-purpose |
| backend-dev | agents/backend-dev.md | API, DB, auth, business logic | general-purpose |
| qa-engineer | agents/qa-engineer.md | Test strategy and automation | general-purpose |
| devops-engineer | agents/devops-engineer.md | CI/CD, deployment, monitoring | general-purpose |
Pre-Flight Checks
Phase 1: Setup (Orchestrator)
task(agent_type="general-purpose",
description="Read the user's web app request. Create _workspace/ and _workspace/messages/ directories. Extract: app description/purpose, core features, tech stack preferences, scale (MVP/small/medium/large), existing code (if any), deployment platform. Write organized input to _workspace/00_input.md with sections: APP_DESCRIPTION, CORE_FEATURES, TECH_PREFERENCES, SCALE, EXISTING_CODE, DEPLOYMENT_TARGET.")
Phase 2: Architecture Design
Step 2.1 — Architect
task(agent_type="general-purpose",
description="You are the architect agent. Read agents/architect.md for your full instructions. Read _workspace/00_input.md. Design the system architecture: component diagram, technology stack selection, database schema, and API specification. Write to _workspace/01_architecture.md, _workspace/02_api_spec.md, _workspace/03_db_schema.md. Write handoff message to _workspace/messages/architect-to-all.md.")
Phase 3: Sequential Development (file-bus port of original parallel step)
Step 3.1 — Frontend Developer
task(agent_type="general-purpose",
description="You are the frontend-dev agent. Read agents/frontend-dev.md for your full instructions. Read _workspace/00_input.md, _workspace/01_architecture.md, _workspace/02_api_spec.md, and _workspace/messages/architect-to-all.md. Implement the complete frontend application. Write source code to src/ (frontend). Write handoff message to _workspace/messages/frontend-dev-to-qa.md.")
Step 3.2 — Backend Developer
task(agent_type="general-purpose",
description="You are the backend-dev agent. Read agents/backend-dev.md for your full instructions. Read _workspace/00_input.md, _workspace/01_architecture.md, _workspace/02_api_spec.md, _workspace/03_db_schema.md, and _workspace/messages/architect-to-all.md. Implement the complete backend API and database layer. Write source code to src/ (backend/api). Write handoff message to _workspace/messages/backend-dev-to-qa.md.")
Step 3.3 — DevOps Engineer (deployment setup)
task(agent_type="general-purpose",
description="You are the devops-engineer agent working on deployment setup. Read agents/devops-engineer.md for your full instructions. Read _workspace/00_input.md, _workspace/01_architecture.md, and _workspace/messages/architect-to-all.md. Create Dockerfile, docker-compose.yml, and .github/workflows/ CI/CD pipeline. Write _workspace/05_deploy_guide.md. (QA test commands will be updated after QA phase.)")
Phase 4: QA & Review
Step 4.1 — QA Engineer
task(agent_type="general-purpose",
description="You are the qa-engineer agent. Read agents/qa-engineer.md for your full instructions. Read _workspace/00_input.md, _workspace/01_architecture.md, _workspace/02_api_spec.md, _workspace/messages/frontend-dev-to-qa.md, and _workspace/messages/backend-dev-to-qa.md. Write test strategy to _workspace/04_test_plan.md, write test code to src/. Review the frontend and backend code for bugs. Write message to _workspace/messages/qa-engineer-to-devops.md including all MUST_FIX items.")
Step 4.2 — DevOps Final Review
task(agent_type="general-purpose",
description="You are the devops-engineer agent doing final review. Read agents/devops-engineer.md for your full instructions. Read _workspace/messages/qa-engineer-to-devops.md. Update CI/CD pipeline with test commands from QA. Address any MUST_FIX items that affect deployment. Write final review report to _workspace/06_review_report.md.")
Scale Modes
| Request Pattern | Mode | Agents Used |
|---|
| "Build me a web app" / "full stack" | Full Pipeline | All 5 |
| "Just build the API" | Backend Mode | architect + backend-dev + qa-engineer |
| "Build the frontend" (API exists) | Frontend Mode | architect + frontend-dev + qa-engineer |
| "Set up deployment" | DevOps Mode | devops-engineer |
| "Refactor this codebase" | Refactor Mode | architect + relevant-dev + qa-engineer |
Error Handling
| Error Type | Strategy |
|---|
| Unclear requirements | Orchestrator extracts what it can, marks assumptions in 00_input.md |
| Frontend/backend API mismatch | QA engineer catches this; flag in messages/qa-engineer-to-devops.md |
| Test failures | QA marks MUST_FIX items; DevOps addresses in final review |
Test Scenarios
- Normal case: Complete app requirements provided → full pipeline produces working code + tests + deployment
- Existing code: User provides existing codebase → architect analyzes, only needed agents run
- Partial request: "Add auth to my app" → architect + backend-dev (auth focus) + qa-engineer
