Signal Setup

Signal Setup

Guide for registering and configuring phone numbers with signal-cli for the Signal AI Assistant.

Overview

Signal registration is a one-time setup process that creates the cryptographic identity for a phone number. The registration data is stored in the data/signal-cli-config/ directory and must be preserved - losing this data requires re-registration.

Prerequisites

• signal-cli installed (macOS: brew install signal-cli, or download from GitHub releases)
• Java 21+ (required by signal-cli 0.13.2+)
• A dedicated phone number capable of receiving SMS
• Note: Most VoIP numbers do not work with Signal

Registration Process

Step 1: Obtain CAPTCHA Token

1. Open https://signalcaptchas.org/registration/generate.html in a browser
2. Complete the CAPTCHA challenge
3. Open browser DevTools (F12) → Network tab
4. Look for a request starting with signalcaptcha://
5. Copy the full token (format: signalcaptcha://signal-hcaptcha.LONG_TOKEN_STRING)

Important: Tokens expire quickly. Proceed to Step 2 immediately after obtaining the token.

Step 2: Register Phone Number

./scripts/signal-cli.sh -a +1234567890 register --captcha 'signalcaptcha://signal-hcaptcha.TOKEN_HERE'

Replace +1234567890 with the actual phone number in E.164 format.

Success indicator: Command completes with no output. An SMS verification code will be sent to the phone.

Step 3: Verify with SMS Code

./scripts/signal-cli.sh -a +1234567890 verify 123456

Replace 123456 with the 6-digit code from the SMS.

Success indicator: Command completes with no output.

Step 4: Set Profile Name and Avatar

./scripts/signal-cli.sh -a +1234567890 updateProfile --given-name "AgentName" --avatar jarvis.jpg

This sets the display name and profile picture other Signal users will see.

Troubleshooting

"User not registered" Error

The registration process did not complete. Common causes:

• CAPTCHA token expired before registration command ran
• Network issues during registration
• Phone number already registered on another device

Fix: Start fresh from Step 1 with a new CAPTCHA token.

No SMS Received

Some phone numbers cannot receive Signal verification SMS. Try voice verification:

./scripts/signal-cli.sh -a +1234567890 register --captcha 'TOKEN' --voice

Note: Voice verification only works after an SMS attempt has been made. Signal requires trying SMS first.

CAPTCHA Token Rejected

Tokens have a very short lifespan. Solutions:

• Get a fresh token and run the register command within 30 seconds
• Ensure the full token is copied, including the signalcaptcha:// prefix
• Check for any trailing whitespace or line breaks

Rate Limited

Signal rate-limits registration attempts. If rate limited:

• Wait several hours before retrying
• Avoid repeated failed attempts as this extends the cooldown

Java Version Mismatch

Error: class file version 65.0 ... this is Java 21

signal-cli 0.13.2+ requires Java 21. Check version:

java -version

On macOS, install via Homebrew:

brew install openjdk@21

Configuration Directory Structure

After successful registration, the config directory contains:

data/signal-cli-config/
└── data/
    ├── accounts.json          # Account metadata
    └── {account-id}/          # Per-account data
        ├── identity-key       # Cryptographic identity
        ├── sessions/          # Session keys with contacts
        └── ...

Critical: Back up this directory. Losing it requires re-registration and may cause message delivery issues with existing contacts.

Docker Considerations

When running in Docker, mount the signal-cli config from the host:

volumes:
  - ./data/signal-cli:/home/jarvis/data/signal-cli

Ensure the SIGNAL_CLI_CONFIG environment variable points to the mounted path inside the container.

Environment Variables

Quick Reference

All commands use the wrapper script ./scripts/signal-cli.sh which automatically sets the config path to data/signal-cli-config/.

# Register (get CAPTCHA first)
./scripts/signal-cli.sh -a +1234567890 register --captcha 'TOKEN'

# Verify SMS code
./scripts/signal-cli.sh -a +1234567890 verify 123456

# Set profile name and avatar
./scripts/signal-cli.sh -a +1234567890 updateProfile --given-name "Name" --avatar jarvis.jpg

# Test sending a message
./scripts/signal-cli.sh -a +1234567890 send -m "Hello" +0987654321

# List registered accounts
./scripts/signal-cli.sh listAccounts

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