Firefox Native Messaging unavailable in Zen Browser Flatpak on Fedora 44, breaking download capture

[a-y-a-n-das]

📝 Description

AB Download Manager's Firefox extension connects successfully to AB Download Manager on port 15151, but automatic download capture and the context-menu integration do not work in Zen Browser installed from Flathub.

The extension console reports:

Native messaging is not available!

Environment

OS: Fedora Linux 44

Desktop: COSMIC / Wayland

Zen: 1.21.14b, Flathub Flatpak

Zen App ID: app.zen_browser.zen

Runtime: org.freedesktop.Platform/x86_64/25.08

AB DM extension: 1.5.0

AB DM: installed under ~/.local/ABDownloadManager/

What works

AB Download Manager is running and listening:

AB DM: /home/ayandas/.local/ABDownloadManager/bin/ABDownloadManager --background
Port: 15151

The extension's connection test reports:

Success — Port (15151) is connected

The native messaging host exists and is executable:

~/.local/ABDownloadManager/bin/ABDownloadManagerNativeMessagingHost

The Firefox native messaging manifest also exists at:

~/.mozilla/native-messaging-hosts/com.abdownloadmanager.json

with the correct extension ID:

"allowed_extensions": [
"firefox-integration@abdownloadmanager.com"
]

What doesn't work

Automatic download capture

"Download with AB Download Manager" context-menu integration

Native Messaging

The extension reports:

Native messaging is not available!

Investigation

I granted Zen read-only access to:

~/.mozilla/native-messaging-hosts

but this did not resolve the issue.

Fedora is running:

xdg-desktop-portal-1.22.1-1.fc44.x86_64

However, the following D-Bus interface is unavailable:

org.freedesktop.portal.WebExtensions

dnf provides '*/org.freedesktop.portal.WebExtensions.xml' also returns:

No matches found.

Therefore, it appears that the required Flatpak/WebExtensions Native Messaging bridge is unavailable in this Fedora setup.

Suspected cause

Zen Flatpak
↓
Firefox Native Messaging
↓
WebExtensions portal
↓
Not available on Fedora 44
↓
AB Download Manager native host

The AB Download Manager application and port 15151 are working correctly. The failure appears to occur at the browser's Native Messaging layer.

Question

Is there a way for the AB Download Manager extension to support Zen/Firefox Flatpak installations where Native Messaging is unavailable?

Since the extension can already communicate with AB DM through port 15151, could automatic download capture use that existing connection as a fallback instead of requiring browser.runtime.connectNative()?

If this is fundamentally a Flatpak/Fedora limitation.

🏷️ App Version

1.5.0

💻 Platform

Fedora 44

📦 Installation Type (optional)

Flathub

⚙️ System/Device Details (optional)

Ryzen 5625u

🔁 Steps to Reproduce

Steps to reproduce

1. Install AB Download Manager Browser Integration in Zen Flatpak.
2. Open a direct download link.
3. Click the download link.
4. Download starts in Zen instead of AB Download Manager.

✅ Expected Behavior

The download should be automatically captured by AB Download Manager, and the context-menu integration should work.

📷 Screenshots or Recordings (optional)

No response

🗒️ Additional Information (optional)

No response

💡 Possible Solution (optional)

No response