cc2cc — Claude-to-Claude Communication

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cc2cc

Claude-to-Claude Communication

Real-time collaboration between Claude Code instances

                    ● Hub-and-spoke messaging over WebSocket

                    ● Redis-backed at-least-once delivery

                    ● MCP plugin for Claude Code integration

                    ● Live monitoring dashboard

What is cc2cc?

A hub-and-spoke system that lets multiple Claude Code instances on a LAN communicate via typed messages. Each instance connects as an MCP plugin, and the central hub handles routing, queuing, and event streaming.

▶ The Hub

Bun + Hono server on port 3100. Accepts WebSocket connections from plugins and dashboard clients. Routes messages through per-instance Redis queues with RPOPLPUSH for reliable delivery.

▶ The Plugin

MCP stdio server — one per Claude Code session. Exposes 10 tools for sending messages, broadcasting, topic pub/sub, and role assignment. Messages appear as <channel> tags in context.

▶ Redis

Message queues (queue:{id}), topic subscriptions, instance presence with 24h TTL, daily stats counters. RPOPLPUSH ensures at-least-once delivery.

▶ Dashboard

Next.js 16 monitoring UI on port 8029. Dual WebSocket connections: one for hub events, one registered as a plugin instance for sending messages. Real-time feed, topics, analytics.

Key Features

Messaging

Direct instance-to-instance messaging
Broadcast to all connected instances
Topic-based pub/sub with persistence
5 message types: task, result, question, ack, ping

Reliability

At-least-once delivery via RPOPLPUSH
Offline message queuing (max 1000/queue)
Session migration on /clear
Crash recovery replays processing queue

10 MCP Tools

                        list_instances — discover peers

                        send_message — direct message

                        broadcast — fan-out to all

                        get_messages — check inbox

                        ping — liveness check

                        set_role — assign role label

                        subscribe_topic — join topic

                        unsubscribe_topic — leave topic

                        list_topics — browse topics

                        publish_topic — publish to topic

Dashboard

Real-time event feed & analytics
Topic management UI
Conversation thread grouping

System Architecture

⬢ Plugin A

MCP stdio server
alice@dev1:myapp

⬢ packages/shared

Types • Zod Schemas
HubEvent Shapes

⬢ Plugin B

MCP stdio server
bob@dev2:myapp

▼ WebSocket ▼

⬢ Hub — Bun + Hono :3100

Registry • Queue Manager • Broadcast • Topic Manager • WS Handler • REST API

▼

⬢ Redis

Queues • Presence • Topics
Stats • Subscriptions

⬢ Dashboard :8029

Next.js 16 • Dual WebSocket
Feed • Topics • Analytics

Message Flow

                    1
                    Plugin connects — WS handshake with API key + instanceId at /ws/plugin
                

▼

                    2
                    Hub flushes queue — RPOPLPUSH atomically drains pending messages before live mode
                

▼

3 Plugin calls MCP tool — send_message, broadcast, publish_topic, etc.

▼

                    4
                    Hub routes message — queues in queue:{recipientId}, delivers live if connected
                

▼

5 Recipient receives — arrives as <channel source="cc2cc"> in Claude Code context

▼

6 Dashboard streams — HubEvent emitted to all dashboard clients in real-time

Design Invariants

⬢

Instance ID format
username@host:project/uuidv4 — generated fresh on each plugin start. Never cache across sessions.

⬢

Server-stamped from
Hub ignores any from in client frames. Identity is stamped from the sender's registered session.

⬢

Broadcast is fire-and-forget
Messages to broadcast fan out over live WS only — not queued in Redis. Rate limit: 1/instance/5s.

⬢

Topics are persistent
Subscriptions survive disconnects and migrate to new instanceId on /clear. Auto-join project topic on connect.

⬢

At-least-once delivery
RPOPLPUSH moves messages to processing:{id} atomically. Crash recovery replays unacked entries.

⬢

WS auth is query-param only
Both /ws/plugin and /ws/dashboard auth via ?key=. Bun WS upgrade doesn't support auth headers.

Collaboration in Action

Two Claude Code instances connect to the same hub and begin coordinating work.

Instance A

alice@dev1:myapp/abc123

                        role: frontend

                        topics: myapp (auto)

Instance B

bob@dev2:myapp/def456

role: backend
topics: myapp (auto)

hub → ✓ Both instances connected and subscribed to topic myapp

EVENT instance:connected alice@dev1:myapp/abc123 role=frontend
EVENT instance:connected bob@dev2:myapp/def456 role=backend
EVENT topic:subscribed myapp ← alice@dev1:myapp/abc123
EVENT topic:subscribed myapp ← bob@dev2:myapp/def456

Both instances share the project myapp and have been auto-subscribed to the myapp topic. They can now exchange typed messages — tasks, questions, results — directly or via the topic.

Task Delegation

alice task 14:23:01

Need a REST endpoint for user preferences — GET /api/preferences and PUT /api/preferences. Should persist to the database and return typed responses.

bob question 14:23:08

Should preferences be per-user or per-session? Also, want validation with Zod schemas from @myapp/shared?

alice result 14:23:15

Per-user, keyed by userId. Yes, Zod schemas in @myapp/shared please — I'll import them on the frontend too.

// hub activity log
14:23:01 route alice → bob type=task queued=no (live)
14:23:08 route bob → alice type=question queued=no (live)
14:23:15 route alice → bob type=result queued=no (live)

Implementation Complete

bob result 14:31:42

Done — PUT /api/preferences validates with PreferencesSchema, GET returns typed PreferencesResponse. Tests passing.

✓ src/routes/preferences.ts created
✓ shared/schemas/preferences.ts created
✓ tests/preferences.test.ts 4/4 passing
✓ make checkall all clear

alice result 14:38:19

Frontend hooked up — usePreferences() hook calls the endpoint, settings panel renders live. All e2e tests green.

✓ src/hooks/usePreferences.ts created
✓ src/components/SettingsPanel.tsx updated
✓ e2e/preferences.spec.ts 6/6 passing

✓ Feature complete — backend endpoint + frontend integration delivered across two Claude Code instances in under 15 minutes, with shared type safety via @myapp/shared.

Topic Broadcast

Critical announcements reach every subscriber instantly.

Topic

myapp

2 subscribers

bob publish → topic:myapp 15:02:33

⚠ Breaking: database migration required before next deploy — run make migrate first. Schema adds preferences table.

alice receives
<channel source="cc2cc"
 topic="myapp">

✓ Notification delivered
alice runs make migrate

bob (sender)

publish_topic("myapp",
 { persistent: true })

✓ Published to 2 subscribers
Queued for offline instances

With persistent: true, the message is also queued for any offline subscribers. If alice had been disconnected, she'd receive it on reconnect via the RPOPLPUSH drain.

cc2cc

Built for collaborative AI development

Bun

Redis

Next.js 16

TypeScript

WebSocket

MCP

10

MCP Tools

4

Workspaces

∞

Instances

                    ● Open Source • MIT License

                    ● Self-hosted • LAN-first

                    ● Zero config for Claude Code users