Signal Claude Bridge

Signal-Claude Bridge

A lightweight daemon that connects Signal Messenger to Claude Code AI agents via signal-cli's JSON-RPC interface. Send a message on Signal, get an AI-powered response — no app, no web UI, just your existing Signal conversations.

Use it to build a personal assistant, a network diagnostics bot, a home automation helper, or anything else a Claude Code agent can do.

Architecture

Signal App                signal-cli daemon            this bridge              Claude Code CLI
    │                          │                           │                         │
    │──── encrypted msg ──────>│                           │                         │
    │                          │── JSON-RPC notification ─>│                         │
    │                          │                           │── claude -p --agent ───>│
    │                          │                           │                         │
    │                          │                           │<── stdout response ─────│
    │                          │<── JSON-RPC send ─────────│                         │
    │<─── encrypted msg ───────│                           │                         │

Features

• Zero dependencies — stdlib-only Python, no pip install needed
• Single file — the entire bridge is one ~450-line Python script
• Agent-agnostic — works with any Claude Code agent, or none (uses default Claude behavior)
• Whitelist access control — only configured phone numbers get responses
• Input sanitization — control characters stripped, XML tag breakout prevented, message length enforced
• Prompt injection mitigation — user input wrapped in untrusted delimiters with scope enforcement
• Config validation — agent names validated, broad permission patterns flagged at startup
• Isolated permissions — optional dedicated settings file keeps bridge permissions separate from your interactive Claude config
• Rate limiting — per-sender