/slash

cross-platform application JUST for messaging. an Expo / React Native client (Android, web, optional iOS) talks to a Bun + Elysia backend over HTTP and one WebSocket. the client imports the backend's App type through Eden, so there is no hand-written API client.

Docs →

built by Artur Kozubov and Artem Zaitsev against the MTAA 2025 requirements (Figma, use cases and UAT are in the docs).

What it does

• email + password sign-up and sign-in with Better Auth, optional TOTP two-factor
• private chats (one other user) and group chats with admin and member roles; pin and mute per chat
• text, image (camera or gallery) and location messages, paged history
• live delivery over /ws and Expo push notifications to the other members' devices
• English and Slovak UI; light, dark and high-contrast themes

Run

the backend and the app are Bun workspaces; install once at the root (postinstall also sets up lefthook):

bun install

backend, from modules/backend:

cp .env.example .env     # PORT, HOSTNAME, FRONTEND_URL; AXIOM_API_TOKEN + AXIOM_DATASET send OpenTelemetry traces to Axiom
bun migration:run        # applies sqlite/migrations to sqlite/slash.sqlite (override with DB=)
bun dev                  # http://localhost:3000, Swagger UI at /swagger
ngrok http 3000          # in another terminal, so a phone can reach it

app, from modules/mobile:

cp .env.example .env     # EXPO_PUBLIC_BACKEND_URL=https://***.ngrok-free.app/ (http(s) is swapped for wss:// for the socket)
bun run dev --clear      # Expo dev server: browser preview, Expo Go, Android emulator, iOS simulator, dev build

the app uses file-based routing: screens live in modules/mobile/app.

How it works

the backend keeps an in-memory map of chat → open sockets. a client opens /ws?id=<user id> after sign-in and is subscribed to all of its chats; a new message is stored, broadcast to that map and pushed to everyone else in the chat.

sequenceDiagram
  participant A as mobile (sender)
  participant B as backend
  participant DB as SQLite
  participant C as mobile (other members)
  participant P as Expo push
  C->>B: open /ws?id=userId
  B->>DB: look up the user's chats, subscribe the socket
  A->>B: POST /messages/:chatId (type, content)
  B->>DB: insert message, plus image file or location
  B-->>C: new_message over /ws
  B->>P: push to the members' device tokens
  B-->>A: the saved message

Loading

everything except /api/auth/* (Better Auth) sits behind the auth middleware: /users, /chats, /messages, /files. the database is SQLite through Drizzle (bun:sqlite, WAL mode); the schema and its ER diagram are on the architecture page.

Structure

modules/backend      @slash/backend: Bun + Elysia API, Drizzle on SQLite, Better Auth, Swagger, OpenTelemetry
modules/mobile       @slash/mobile: Expo Router app, Eden client typed from the backend, i18n-js (en, sk)
packages/tsconfig    @slash/tsconfig: shared base tsconfig
docs/                Fumadocs (Next.js) site, deployed at slash-docs.vercel.app
.releases/02/        snapshot of the docs' MDX for release 02
.linked/             google-services.json for the Android build (referenced from app.json)

flowchart LR
  mobile["modules/mobile<br/>Expo app"] -- "App type via Eden" --> backend["modules/backend<br/>Bun + Elysia API"]
  mobile -- "HTTP + WebSocket" --> backend
  backend --> tsconfig["packages/tsconfig"]
  mobile --> tsconfig
  docs["docs<br/>Fumadocs site"] --> tsconfig

Loading

modules/backend and modules/mobile used to be the separate slash-backend and slash-mobile repos; both were merged in here with their full history.

Docs

docs/ is a Fumadocs site; the pages are MDX in docs/content/docs, Mermaid diagrams included.

section	pages
introduction	what /slash is, authors, activity
tech overview	architecture (deployment and ER diagrams), tech stack, third-party APIs
project overview	platforms, use cases
design	Figma
tests	UAT

cd docs
bun install              # not a workspace; it has its own lockfile
bun dev                  # http://localhost:3000, redirects to /docs

.releases/02/mdx-files keeps the same pages as they were for the GitHub release 02. code docs for the app come from TypeDoc: bun run docs in modules/mobile writes them to modules/mobile/.docs (git-ignored).

Develop

bun run biome:check                      # Biome format + lint, from the root
bun run --cwd modules/backend test
bun run --cwd modules/mobile test        # jest-expo, watch mode

Deploy

• backend: bun run build:linux-x64 (or build:windows-x64) in modules/backend compiles one server binary; example-systemd.slash-bun.service runs it under systemd
• app: EAS builds from modules/mobile/eas.json (development, preview APK, production); preview and production point at https://slash-backend.justadomainname.dev
• docs: slash-docs.vercel.app

Activity