WhatsApp Bridge

Wire WhatsApp into the existing chat interface as one more channel adapter. The framework already abstracts Telegram/Slack/Discord (see .claude/sections/02_*); this adds a WhatsApp adapter behind the same interface — it does not fork the engine.

Provider

Use the WhatsApp Cloud API (Meta) or an equivalent gateway (e.g. Twilio for WhatsApp). Both deliver inbound messages via webhook and accept outbound sends via REST.

Required .env values:

WHATSAPP_PHONE_NUMBER_ID=
WHATSAPP_ACCESS_TOKEN=
WHATSAPP_VERIFY_TOKEN=          # for webhook handshake
WHATSAPP_ALLOWED_NUMBERS=       # comma-separated allowlist

Adapter contract

Implement the channel adapter to match the existing chat interface:

1. Inbound — verify the webhook signature, drop senders not in WHATSAPP_ALLOWED_NUMBERS, normalize the payload to the engine's message shape, and hand it to the router.
2. Outbound — render the engine's reply to WhatsApp's message format and POST it to the Cloud API.

Security

• Enforce WHATSAPP_ALLOWED_NUMBERS on every inbound message — mirror the TELEGRAM_ALLOWED_USER_IDS allowlist pattern. Unknown senders are dropped, not answered.
• Outbound sends are mutations: route them through the chat.send capability gate with an audit trail. Never call the WhatsApp API directly from a tool.
• Verify the webhook X-Hub-Signature-256 HMAC before trusting any payload.