v4.0.0: Platform Extensions for Pito

🎯 Overview

koshi v4.0.0 extends the platform as a backend for Pito (React Native/Expo messenger) with group chat, E2E key management, read receipts, and typing indicators.

✨ New Features

👥 E2EE Group Chats (Sender Keys)

• Create groups with up to 100 members
• All groups are always end-to-end encrypted
• Server only verifies signatures, never decrypts
• Sender Keys for group E2E (MLS migration path exists)

📱 X3DH Key Management

• Device registration with identityKey, signedPreKey, preKeySignature
• One-time prekey consumption per session
• Key bundle fetching for X3DH handshake

✅ Read Receipts

• Unified table for DMs and group messages
• WebSocket broadcast for instant cross-device sync

⌨️ Typing Indicators

• Real-time typing start/stop for DMs and groups
• Broadcast to conversation participants only

🔧 TypeScript SDK

npm install @ryopc/koshi

import { Group, GroupMessage, Device, KeyBundle, WSEventMap } from '@ryopc/koshi/types'

📡 New API Endpoints

Category	Endpoints
Groups	GET/POST /api/groups, GET/PATCH/DELETE /api/groups/:id, POST/DELETE /api/groups/:id/members, GET/POST /api/groups/:id/messages, PUT /api/groups/:id/messages/:msgId/read
Devices	GET/POST /api/devices, DELETE /api/devices/:deviceId, GET /api/devices/user/:userId
Keys	GET /api/keys/bundle/:userId

🔌 New WebSocket Events

Client → Server	Server → Client
group:create	group_created
group:update	group_updated
group:delete	group_deleted
group:invite	group_member_added
group:leave	group_member_removed
group:message	group_message
group:read	group_message_read
typing:start	typing_start
typing:stop	typing_stop
key_bundle:request	key_bundle_response

🗄️ New Database Tables

• groups - E2EE group chats
• group_members - Membership with roles (admin/member)
• group_messages - Encrypted group messages
• message_read_receipts - Unified read receipts
• user_devices - X3DH device keys
• group_session_keys - Sender Keys

🛠️ New CLI Commands

kb groups [list|create|delete|info]
kb group <name> members [add|remove|list]
kb devices [list|remove]
kb keys [rotate|bundle]
kb admin promote <username>
kb config set <key> <value>

⚠️ Important Notes

• PostgreSQL required for new features (not available in P2P/SQLite mode)
• Existing APIs (DMs, posts, follows, P2P) remain unchanged
• All groups are E2EE (isE2EE: true always)
• E2E is client responsibility — server only relays, verifies signatures

📦 Installation

npm install -g @ryopc/koshi@4.0.0