Agent Builder (DevDay Challenge)

A small monorepo to design, save, and run LLM “flows” (router → agent) with a visual editor.

• Backend: Fastify (TypeScript)
• Frontend: Vite + React + React Flow/XYFlow
• Storage (MVP): filesystem for flows + in-memory conversation store
• LLM: Google Gemini (via @google/genai)

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Features

Backend (apps/api)

• POST /flows — Save a flow (stored on disk, returns flow_id)
• GET /flows/:id — Load a flow by id
• POST /chat — Run a flow for a message (router_llm -> pickNext -> agent)
• Trace output for debugging (router decision + selected agent)
• Swagger UI available at /docs

Frontend (apps/web)

• Visual flow editor using React Flow
• Custom nodes:
  • Router LLM node
  • Agent node
• Save flow to backend and display the generated flow_id

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Monorepo Structure

apps/ api/ # Fastify API (TypeScript) web/ # Vite + React UI (React Flow) packages/ shared/ # (reserved, mostly empty for now)

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Requirements

• Node.js 18+ recommended
• npm (or your preferred package manager)