Bridge won’t connect on Snap/Flatpak Linux

In short: a sandboxed (Snap or Flatpak) Thunderbird can’t launch atbridge.ai’s helper, so the add-on won’t connect. Run the helper as a background service (atbridge bridge service install && atbridge bridge service start) and pair the add-on over loopback with the token from atbridge bridge pair — or reinstall Thunderbird from thunderbird.net.

On Linux, if atbridge.ai “worked then stopped”, the @bridge add-on can’t connect, or activation fails with a vague error (and ~/.atbridge has no license.json), the cause is almost always how Thunderbird was installed — not your license.

Why this happens

atbridge.ai talks to Thunderbird through a tiny local helper (a native-messaging host). Normally Thunderbird launches that helper itself. Snap and Flatpak run Thunderbird inside a security sandbox that forbids it from spawning an outside program — so the helper never starts and the add-on can’t connect. This bites Ubuntu users especially: the Ubuntu App Center installs Thunderbird as a Snap by default.

Good news: you don’t have to reinstall Thunderbird. A sandboxed Thunderbird can still make local network connections, so atbridge.ai ships a loopback fallback — you run the helper yourself as a small background service, and the add-on connects to it over 127.0.0.1. Set it up once; it sticks.

Tip

This page is the official fix for Snap/Flatpak Thunderbird. On Windows, macOS, and a non-sandboxed Linux Thunderbird the default setup needs none of this — it just works.

Step 1 — Check how Thunderbird is installed

1. Run these in a terminal:

   snap list 2>/dev/null | grep -i thunderbird
   flatpak list 2>/dev/null | grep -i thunder
   which thunderbird

2. If Thunderbird appears under snap or flatpak, use the loopback fallback below. (A plain path like /usr/bin/thunderbird from your distro package or Mozilla’s tarball doesn’t need any of this.)

Note

atbridge bridge tb-check also detects a Snap/Flatpak Thunderbird and prints these same steps.

Step 2 — Run the bridge as a background service

This runs the helper standalone (a systemd --user service) so the sandboxed Thunderbird can reach it over loopback instead of having to launch it.

1. Install and start the service:

   atbridge bridge service install
   atbridge bridge service start

2. Check it’s up:

   atbridge bridge service status

   You want active. (It also starts automatically when you log in.)

Step 3 — Pair the add-on with the service

Because the add-on can’t read files on your machine, you hand it a one-time token so only it can talk to the service (no random web page can).

1. Print the token:

   atbridge bridge pair

   Copy the token value it shows.

2. In Thunderbird, open atbridge.ai → Settings → Advanced → Local bridge (Snap/Flatpak). Paste the token, tick Enable loopback fallback, and click Save. (Leave the port at 45678 unless you changed it.)

Verify

atbridge bridge ping
atbridge connect status

A reply from bridge ping means Thunderbird and atbridge.ai are talking over loopback. Then activate your plan if you haven’t yet.

Tip

You don’t need to reinstall Thunderbird. The loopback bridge above is a first-class, supported setup — keep your Snap/Flatpak Thunderbird. (If you’d rather skip the one-time service setup, a regular Thunderbird from thunderbird.net or a distro package uses the default native bridge with none of the above — but that’s entirely optional.)

Where to go next

• When activation fails
• When AI says “no tools”
• When your AI can’t find anything