Signal Bridge #

Based on mautrix-signal. Pairs as a Signal linked device — the same way Signal Desktop works — so your Signal identity, groups and contacts flow into Matrix with full Signal-protocol E2EE preserved on the Signal side.

Prerequisites #

Meldry plan: Business
A Signal account on your phone (required — Signal does not support primary desktop accounts)
An active phone + network during the initial pairing

Enable the bridge #

Dashboard → Server → Bridges → Signal → Enable.
Wait ~10 seconds. The bot appears at @signalbot:<your-name>.meldry.com.

Link your Signal account #

Signal's linked-device flow is QR-code-based, same as WhatsApp.

In your Matrix client, DM @signalbot:<your-name>.meldry.com.
Send link.
The bot replies with a QR code.
On your phone: Signal → Settings → Linked devices → Link new device. Scan the QR.
Your phone confirms the new device is added. The bot replies Successfully linked as +14155550001.
Signal backfills your recent 1:1 chats and groups as Matrix rooms within a minute.

What gets bridged #

1:1 chats → Matrix DM rooms with contact avatars puppeted.
Groups → Matrix rooms.
Disappearing messages — Signal's timer syncs to Matrix retention; Matrix rooms with a retention policy also expire.
Reactions → bidirectional.
Attachments — images, videos, voice notes, files. Re-encrypted across the bridge.
Read receipts and typing indicators → bidirectional (respects your Signal privacy settings).
Stories → NOT bridged (Signal Stories use a separate API).
Calls → NOT bridged (Signal voice/video is Signal-proprietary).

Signal-protocol caveats #

Signal is ruthlessly E2EE and doesn't give linked devices direct message history. The bridge starts receiving messages from the moment you pair — there's no backfill of older history. Messages sent while your phone was offline will come through once it reconnects.

Commands reference #

Command	What it does
`link`	Start the linked-device QR flow
`unlink`	Unlink (also removes the device from the phone's linked-devices list)
`status`	Show link health
`list-contacts`	List Signal contacts
`pm <+countrynumber>`	Start a DM with a Signal number
`sync-contacts`	Force contact re-sync
`help`	Full command list

Identity verification (safety numbers) #

Signal identifies contacts by safety numbers — a fingerprint you compare in-person to confirm you're talking to the right person. The bridge exposes them:

Run safety <matrix-user-id> in the bridge DM to view a contact's safety number.
If a safety number changes (your contact reinstalled Signal), the bridge flags it in the room as a system message.

Troubleshooting #

QR code expired — run link again for a fresh one (expires every ~30 seconds).

"Primary device went away" — if your phone is factory-reset or you delete Signal on it, every linked device (including the bridge) is kicked. Set up Signal on the phone again, then re-link.

Messages delivered on phone but not on Matrix — check the bridge DM for a status report. If it shows registration lock, you've added a Signal PIN — re-run link to re-pair.

Group changes not syncing — large group admin events batch; wait 30 seconds and run sync-contacts.

Media fails to decrypt — very rarely, Signal's attachment cipher rotates and old links break. Re-send the image from the original chat.

Privacy considerations #

Your phone number is stored in the bridge database.
Signal message content is decrypted at the bridge process to be re-encrypted for Matrix. Meldry does not log message bodies.
Unlinking removes the bridge's Signal session and closes all puppeted rooms.