Logan — AI Personal Trainer

A Next.js app where you chat with Logan, an AI personal trainer, and get a workout built for the time, equipment and goals you actually have today. Logan then coaches you through the session by voice.

How it works

1. Chat — tell Logan how long you have, what you want to work on, and what equipment is around. He asks follow-ups for anything you leave out.
2. Preview — Logan proposes a workout. Review the exercises, then start it or go back and adjust.
3. Train — work through the session, logging reps and weight per set. An optional voice coach can mark sets complete hands-free.
4. Finish — see what you actually completed. Logan remembers your preferences for next time.

Setup

Requires Node.js 20+.

npm install
cp .env.example .env.local   # then fill it in
npm run dev

Open http://localhost:3000.

.env.example documents every variable. The three required ones are NEXT_PUBLIC_SUPABASE_URL, NEXT_PUBLIC_SUPABASE_ANON_KEY and OPENAI_API_KEY; the app will not build or run without them. See SUPABASE_SETUP.md for where to find the Supabase values.

Memory (MEM0_API_KEY) is optional — without it Logan simply starts fresh each session instead of recalling past preferences.

Scripts

Command	Description
npm run dev	Start the dev server
npm run build	Production build (runs typecheck + lint)
npm run start	Serve the production build
npm run lint	ESLint
npm run typecheck	TypeScript, no emit

Project structure

src/
├── app/
│   ├── api/
│   │   ├── chat-with-logan/        # Conversation with the trainer
│   │   ├── generate-simple-workout/# Turns the conversation into a workout
│   │   └── realtime-session/       # Mints ephemeral keys for the voice coach
│   ├── page.tsx                    # Chat → preview → workout → summary
│   └── layout.tsx
├── components/                     # UI for each step of that flow
├── contexts/AuthContext.tsx        # Supabase auth state
├── lib/
│   ├── conversation-context.ts     # Pulls goals/time/equipment out of chat
│   ├── supabase.ts                 # Browser client
│   ├── supabase-server.ts          # Server client + auth helper
│   ├── memory.ts                   # Mem0 long-term memory
│   └── logger.ts                   # Dev-only debug logging
├── prompts/                        # All model prompts
├── services/database.ts            # Supabase queries
└── types/workout.ts

API routes

All three require an authenticated Supabase session and are rejected with 401 otherwise — each one spends OpenAI credits.

Route	Purpose
POST /api/chat-with-logan	Logan's next reply, given the conversation
POST /api/generate-simple-workout	Build a workout from the conversation
POST /api/realtime-session	Ephemeral key for the realtime voice coach

Developer tools

The chat reset button and memory inspector are hidden unless NEXT_PUBLIC_ENABLE_DEV_TOOLS=true (they are always on in npm run dev). Reset permanently clears the signed-in user's profile and chat history, so keep it off in production.

Security notes

• Never commit .env.local, and never paste keys into logs or issues.
• log.debug is a no-op outside development. Keep chat content, AI responses and memories out of log.warn/log.error — they hold personal data.
• User identity is always read from the session cookie server-side, never from a request body.

Built with

Next.js 15 (App Router) · React 19 · TypeScript · Tailwind CSS 4 · Supabase · OpenAI · Mem0