sYnX

sYnX is a to-do list app for the web and Android. The web app is a Remix app on Cloudflare Workers with a Cloudflare D1 database. The Android app is built with Expo and React Native, and uses the same account and data through the web app's REST API. Both live in this repo.

Live at synx.christran.io.

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Features

Lists and tasks (web and mobile)

• Multiple lists, each with a category: Checklist, Study, Shopping, Movies, Work, Personal, Travel, Fitness, or a custom one.
• Tasks with a priority (none, low, medium, high), an optional duration (5m to 60m presets or a custom value), and subtasks nested under their parent task.
• Reminders, with quick presets or a picked date and time, and recurrence (daily, weekly, monthly). Repeating tasks keep their local clock time in your home time zone, including across daylight saving changes.
• Inline editing of task and list titles, search (including subtask text), filters (all, active, done), sorting by date created, priority, reminder time or name, and clearing completed tasks.
• A calendar view next to the list view. On the web you can drag unscheduled tasks onto a day.

Sharing

• Each list is Private, View-Only or Collaborative. Anyone with the link can open a View-Only list, and anyone with the link can edit a Collaborative one.
• Lists you open from someone else's link appear under "Shared with me", with the owner's display name. Emails are never shown.

Accounts and guest mode

• Sign-in goes through sYnID, an OpenAuth server at auth.christran.io, with PKCE. Sessions renew in the background.
• Without signing in, the web app works in guest mode. Guest lists are kept in the browser's local storage and move to your account when you sign in.

Reminders and notifications

• A cron trigger runs every minute and sends due reminders by email (Resend), text message (an email-to-SMS carrier gateway through Resend, or Twilio), Discord webhook, and push notification to your phones (Firebase Cloud Messaging).
• The web app can also show browser notifications while it's open.
• Reminder channels, your display name and your home time zone are set in Settings.

Web extras

• Five color themes: Midnight Indigo (default), Emerald Forest, Sunset Rose, Cyberpunk Neon and Light Pastel.
• A progress ring for each list, confetti when you finish the last task, and a What's New popup for each release.

For the Android app's extras, see Mobile app.

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Web app

Framework	Remix 2.17 (on Vite 5) with React 19, running on Cloudflare Workers with static assets
Database	Cloudflare D1 (synx-db, binding DB)
Styling	Tailwind CSS 3
Auth	OpenAuth client (@openauthjs/openauth) against sYnID
Validation	Valibot
Tooling	Wrangler 4, TypeScript 5.8, ESLint 9 (flat config), Vitest 4 with @cloudflare/vitest-pool-workers

server.ts is the Worker entry. Its fetch handler serves the Remix app, and its scheduled handler is the every-minute reminder cron (triggers.crons in wrangler.jsonc).

REST API (/api/v1)

The mobile app uses these routes. They expect a sYnID access token in an Authorization: Bearer <token> header.

Route	Methods
/api/v1/lists	GET, POST
/api/v1/lists/:id	GET, PUT, DELETE
/api/v1/lists/:id/share-mode	PUT
/api/v1/lists/:id/shared	DELETE (remove from Shared with me)
/api/v1/todos	GET, POST
/api/v1/todos/:id	PUT, DELETE
/api/v1/todos/:id/completed	POST
/api/v1/todos/:id/toggle	POST
/api/v1/todos/:id/mark-reminder-sent	POST
/api/v1/todos/clear-completed	POST
/api/v1/settings	GET, PUT
/api/v1/settings/time-zone	PUT
/api/v1/devices	POST (register a push token), DELETE (unregister it)

Environment variables and secrets

Set these on the Worker in the Cloudflare dashboard, or locally in a .dev.vars file (gitignored). Only DB is needed to run locally. Each notification channel is skipped when its secret isn't set.

Name	Used for
DB	D1 binding, set up in wrangler.jsonc
OPENAUTH_ISSUER	sYnID issuer URL (defaults to https://auth.christran.io)
CLIENT_ID_MAP	Optional JSON map from hostname to OAuth client ID (defaults to synx)
SYNX_ALLOWED_CLIENT_IDS	Optional comma-separated list of accepted token audiences (defaults to synx)
RESEND_API_KEY	Reminder emails and email-to-SMS
TWILIO_ACCOUNT_SID, TWILIO_AUTH_TOKEN, TWILIO_FROM_NUMBER	Text messages through Twilio, used when no carrier is set
FIREBASE_SERVICE_ACCOUNT_JSON	Push notifications through FCM

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Mobile app

The Android app lives in mobile/. It's an Expo SDK 58 app (React Native 0.88, React 19.3) in the Expo project synx, owned by chris-tran, with the Android package io.christran.synx. It uses the production web app's /api/v1 routes.

Features

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