Fix Firefox Dev Edition Sign-Out Loop on Shutdown

Quick fix for Firefox Developer Edition constantly logging out and disabling Sync after every browser shutdown.

If you use Firefox Developer Edition, you may have run into an irritating loop: every time you close Firefox or reboot your computer, your Mozilla account is signed out, Firefox Sync is turned off, and an orange warning icon appears on your profile avatar.

Even if you sign back in, the moment Firefox restarts, you are greeted with the same prompt:

Here is what causes this behavior and how to fix it in two minutes.

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Why It Happens

In recent Developer Edition builds, Mozilla has been testing a new Rust-based password and credential storage engine.

When enabled, Firefox's credential manager (storage-rust.sys.mjs) can fail during early startup initialization with an internal NS_ERROR_ABORT. Firefox translates this abort into a false Primary password locked error—even if you have never set or enabled a Primary Password.

Because the browser believes its credential storage is locked, it fails to retrieve your stored OAuth sync keys on boot, invalidates the local session, and forces a sign-out.

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Step 1: Disable Rust Storage in about:config

Reverting to Firefox's stable, classic credential storage engine resolves the false lock immediately.

1. Open a new tab and navigate to about:config.

2. Click Accept the Risk and Continue.

3. In the search bar, search for:

   signon.storage.rust.active
   

4. Double-click the preference to set its value to false.

(Optional: If signon.storage.rust.enabled also appears in your search results and is set to true, double-click it to set it to false as well.)

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Step 2: Remove Zombie Duplicate Sessions

Because Firefox registered a new device profile each time you attempted to sign back in, your Mozilla account likely has multiple stale duplicate sessions.

1. Go to accounts.firefox.com/settings#connected-services.

2. Under Connected Services, look for duplicate entries named Firefox Developer Edition.

3. Click Sign out next to the stale duplicates to clean up your session registry.

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Step 3: Sign In and Verify

1. Click the Profile Avatar in the top-right corner of Firefox.

2. Click Sign in to sync and complete your authentication.

3. Once connected, your avatar will return to normal with no warning badges.

4. Completely close Firefox Developer Edition (Ctrl + Shift + Q on Windows/Linux or Cmd + Q on macOS) and reopen it.

Your account will remain signed in, and Firefox Sync will persist across restarts.