Caltext

iMessage calorie tracking assistant powered by AI.

Stack

• Runtime: Bun + Turborepo monorepo
• API: Hono on Nitro (deployed to Vercel, 3 regions)
• iMessage: Chat SDK + Sendblue adapter
• AI: AI SDK v6 + GPT-4.1 (vision + agent)
• Database: Upstash Redis (global, 3 regions)
• Workflows: Vercel Workflow SDK for durable pipelines
• Nutrition: USDA FoodData Central API

Setup

1. Install dependencies

bun install

2. Configure environment

cp .env.example .env

Fill in the required keys:

Variable	Source
SENDBLUE_API_KEY / SENDBLUE_API_SECRET	sendblue.co
SENDBLUE_FROM_NUMBER	Your Sendblue phone number
UPSTASH_REDIS_REST_URL / UPSTASH_REDIS_REST_TOKEN	console.upstash.com
REDIS_URL	Same Upstash Redis in redis:// format
OPENAI_API_KEY	platform.openai.com
USDA_API_KEY	fdc.nal.usda.gov (free)

3. Run locally

bun run dev

4. Deploy to Vercel

vercel deploy

Deploys to 3 regions: US East (iad1), London (lhr1), Tokyo (hnd1).

5. Set Sendblue webhook

Point your Sendblue incoming message webhook to:

https://your-app.vercel.app/webhooks/sendblue

Project Structure

caltext/
  apps/
    api/                  # Hono API server
      src/
        index.ts          # Routes + webhook handler
        bot.ts            # Chat SDK singleton
        router.ts         # Onboarding vs assistant routing
      workflows/
        handle-message.ts # Main message handler
        onboarding.ts     # Multi-step onboarding
        reminder-loop.ts  # Daily reminders + summaries
  packages/
    ai/                   # AI agent + tools
    db/                   # Upstash Redis data layer
    shared/               # Types, locale, timezone utils

How It Works

1. User texts the Caltext number via iMessage
2. Sendblue forwards the message via webhook
3. New users go through conversational onboarding (name, stats, goal)
4. Returning users interact with the AI assistant
5. Photos are analyzed with GPT-4.1 vision, then grounded in USDA nutrition data
6. Text descriptions are matched against USDA database directly
7. Daily reminders at breakfast/lunch/dinner times (timezone-aware)
8. End-of-day summaries with calorie/macro breakdown
9. Weekly recaps with progress bars and trends