product-capability

App Builder

Full-stack application orchestrator. Translates a natural language request into a concrete project plan, selects the right tech stack, and coordinates specialist agents to build each layer.

When to Use

• User wants to build a new application from scratch
• User describes an app idea and needs a complete starting point
• User wants scaffolding for a specific project type
• User needs to add a major feature that requires coordinating multiple domains

Execution Flow

Step 1 → DETECT     : Identify project type from user description
Step 2 → STACK      : Select tech stack (2026 defaults or user preference)
Step 3 → PLAN       : Generate file structure and task breakdown
Step 4 → COORDINATE : Assign domains to specialist agents
Step 5 → BUILD      : Execute in dependency order
Step 6 → VERIFY     : Confirm structure and report next steps

Project Type Detection

User Description	Project Type	Primary Stack
"web app", "full-stack", "dashboard"	Next.js Full-Stack	Next.js + Prisma + PostgreSQL
"SaaS", "subscription", "payments"	SaaS Product	Next.js + Stripe + Clerk
"landing page", "marketing site"	Static Site	Next.js + Tailwind
"REST API", "backend only"	Express API	Express + JWT + PostgreSQL
"Python API", "FastAPI"	Python API	FastAPI + SQLAlchemy
"mobile app", "iOS + Android"	React Native	Expo + Zustand
"cross-platform mobile"	Flutter	Flutter + Riverpod
"desktop app"	Electron	Electron + React
"browser extension"	Chrome Extension	Chrome MV3
"CLI tool"	Node CLI	Node.js + Commander
"monorepo"	Monorepo	Turborepo + pnpm

Template Reference

Read only the template that matches the detected project type from the templates/ directory.

Template	Path
Next.js Full-Stack	templates/nextjs-fullstack/TEMPLATE.md
Next.js SaaS	templates/nextjs-saas/TEMPLATE.md
Next.js Static	templates/nextjs-static/TEMPLATE.md
Express API	templates/express-api/TEMPLATE.md
Python FastAPI	templates/python-fastapi/TEMPLATE.md
React Native	templates/react-native-app/TEMPLATE.md
Flutter	templates/flutter-app/TEMPLATE.md
Electron Desktop	templates/electron-desktop/TEMPLATE.md
Chrome Extension	templates/chrome-extension/TEMPLATE.md
CLI Tool	templates/cli-tool/TEMPLATE.md
Monorepo	templates/monorepo-turborepo/TEMPLATE.md

Agent Coordination

Domain	Agent	When to Invoke
Database schema	database-architect	When project has persistent data
API routes	backend-specialist	When project has server-side logic
UI components	frontend-specialist	When project has user interface
Auth flow	security-auditor + backend-specialist	When project has authentication
Deployment	devops-engineer	When project needs CI/CD or hosting config
Tests	test-engineer	After core structure is scaffolded

Build Example

User: "Build an Instagram clone with photo sharing and likes"

App Builder Process:
1. DETECT  → Social media app with media upload
2. STACK   → Next.js + Prisma + Cloudinary + Clerk
3. PLAN    → Schema (users, posts, likes, follows)
             API (12 endpoints)
             Pages (feed, profile, upload)
             Components (PostCard, Feed, LikeButton)
4. AGENTS  → database-architect, backend-specialist, frontend-specialist
5. BUILD   → Schema first, then API, then UI
6. VERIFY  → Report created files and next steps

Guardrails

• Always confirm the project type and stack with the user before scaffolding.
• Do not install packages without listing them explicitly first.
• Do not create files outside the project directory.
• Prefer battle-tested defaults (listed above) over novel stacks unless user specifies otherwise.
• If requirements are ambiguous (> 2 interpretations possible), apply the Socratic Gate before building.

Anti-Patterns

• Do not start scaffolding before confirming the project type — wrong assumptions waste significant effort.
• Do not generate an entire application in one shot without a plan — coordinate agents in dependency order.
• Do not choose an exotic stack to be clever — users need maintainable, well-documented defaults.
• Do not skip the verify step — users need to know what was created and what to do next.
• Do not ignore security from the start — auth, input validation, and env var handling must be in the initial scaffold.