OpenLine

Your Android phone's SIM, as a voice API. OpenLine is an open-source, self-hosted alternative to Twilio Voice: an Android phone places and answers real phone calls on its SIM, and your code or AI voice agent controls them over REST and talks through WebSockets.

Documentation · Quickstart · Connect an AI agent · API reference · llms.txt

curl -X POST https://your-openline.example/v1/calls \
  -H "Authorization: Bearer $OPENLINE_KEY" -H "content-type: application/json" \
  -d '{"deviceId":"phone-7f3a91c2","to":"+919876543210",
       "stream":{"url":"wss://my-agent.example.com/ws","format":"twilio"}}'

The phone dials. When the call is answered, OpenLine connects it to your agent's WebSocket and streams the conversation both ways. Your agent hangs up by closing the socket.

Features

• Calls API: place, answer, reject, hang up, hold and send DTMF with plain HTTP requests. Every call, event and transcript is stored and queryable.
• AI agents on real calls: the server streams calls to your agent's WebSocket as raw 16 kHz PCM or in Twilio Media Streams format, so Pipecat and other Twilio-ready agents work as they are. Outgoing and incoming calls.
• Webhooks: signed (HMAC-SHA256) call events with retries and a delivery log.
• Built-in assistant: an optional Gemini Live receptionist that answers your calls and takes messages.
• Silent phone, no root: the phone only routes the call; audio never plays on the handset. One APK, no Shizuku, no PC, no extra hardware.
• Console: sign in, pair phones by QR code, watch phone health, test calls from the browser, manage API keys and settings.
• Self-hosted: one Node.js process and one SQLite file. Expose it with Tailscale Funnel or Cloudflare Tunnel.

How it works

 Caller ── mobile network ── Android phone (OpenLine app)
                                   │  WebSocket: commands, events, call audio
                                   ▼
                            OpenLine server ── webhooks ──▶ your backend
                                   │
                    REST + WebSocket
                                   ▼
                  your code / AI agent (Pipecat, LiveKit worker, custom)

Quick start

Needs Node.js 22.13+ and an Android 11+ phone with a SIM.

git clone https://github.com/Manohar-k-Reddy/openline.git
cd openline/server
cp .env.example .env          # set HTTP_GATEWAY_API_KEY to a long random string
npm install && npm run build && npm start

On Windows, double-click run-server.bat instead. Then:

1. Open http://localhost:8787/ and create your account.
2. Give the server a public address: tailscale funnel --bg 8787 (or a Cloudflare Tunnel), and save it in Settings.
3. Install the APK from Releases on the phone, open Connection in the console and scan the QR code with the app.
4. Create an API key in Settings and place a call.

The Quickstart walks through every step.

Repository

Folder	What's in it
server/	Node.js + TypeScript server: REST API, WebSockets, console, SQLite
android/	The OpenLine Android app (Kotlin)
docs-site/	Documentation site (Astro Starlight), API spec, llms.txt
simulator/	Mock phone, media client and an example echo agent
docs/notes/	Historical development notes

Status

OpenLine is a v1, tested end to end on a Vivo V40 with Android 16: outgoing and incoming carrier calls, two-way call audio, AI agents on calls, and a silent handset. Call audio depends on Android behaviour that can differ between phone makers; reports from other phones are welcome.

Not included yet: SMS, call recording, conferencing and TwiML-style call flows.

Responsible use

You're responsible for the calls you place. Follow local laws on automated calls, telling people they're talking to an AI, and recording consent.

License

MIT