2019321 - A new tab opens up each time the browser restarts

Status: RESOLVED WORKSFORME

(Enterprise Products :: Firefox, defect)

Description

[lburuian]

Attachment: Screencast from 2026-02-25 17-19-18.webm

Found in

• Firefox Enterprise 149.0a1 (2026-02-21)

Tested platforms

• Affected platforms: All

Preconditions

• Be logged into Firefox Enterprise.
• Make sure to enable the "Open previous windows and tabs" options in about:preferences.

Steps to reproduce

1. Restart the browser using the restart firefox functionality from the URL search results.
2. Close and reopen the browser.

Expected result

• The previous open tabs are displayed in the browser after restart.

Actual result

• A new tab is opened each time the browser restarts.

Comment 1

[vlopezgarcia]

It looks like it is the same behavior than in Mozilla central.

Basically there is some code that checks whether a new tab needs to be spawned when a session restore happens.

The check takes into account defaultargs vs the window args when a homepage policy is applied, this check yields another result than for a the case without a policy.

Without policy:
SessionStore: _isCmdLineEmpty firstArg=about:home defaultArgs=about:home match=true

With policy:
echo '{"policies":{"Homepage":{"URL":"https://example.com","StartPage":"homepage"}}}' > firefox/obj-aarch64-apple-darwin25.3.0/dist/Nightly.app/Contents/Resources/distribution/policies.json

SessionStore: _isCmdLineEmpty firstArg=about:home defaultArgs=https://example.com/ match=false

This is in turn spawning a new tab when a restore session is happening.

Comment 2

[Brian Thomas Smith [:bsmth]]

I can't repro this on macOS with FxEnt 154.0 against prod. Both with and without the homepage policy.

Miruna, can you reproduce this?

Comment 3

[Miruna Curtean]

(In reply to Brian Thomas Smith [:bsmth] from comment #2)

I can't repro this on macOS with FxEnt 154.0 against prod. Both with and without the homepage policy.

Miruna, can you reproduce this?

Hi Brian,
I cannot repro it either on 154.0 (20260814140741) on macOS 26.4, neither through app re-launch or restart from the URL bar. I'm waiting for confirmation on the other platforms, and then we could close it as WORKSFORME.

Comment 4

[Miruna Curtean]

Attachment: new blank tabs are closed upon restart.webm

While the initial behavior is not reproducible, we noticed a few other issues:

1. Blank new tabs are closed upon restart - this is behavior that does not occur on regular Firefox. should we assume the same for FxE?
2. There is an inconsistent issue that was noticed initially on Ubuntu and we have to investigate more because there seemingly is no exact pattern, but it looks like upon restart, previously closed blank tabs are re-opened (sometimes on the second restart, sometimes at restart from another tabs where content has been loaded)
   I suggest we leave this open for a while so we can investigate on all platforms and see if we can figure out a pattern or at least document all new behaviors.
   Thank you

Comment 5

[Miruna Curtean]

Confirming this ticket as resolved with 154.0 (20260814140741) on macOS 26.4, Win 11 and Ubuntu 20.4 as the original issue of a new tab opening each time we restart is no longer reproducible.
QA will investigate and log a separate issue for the behavior with the new/blank tabs that are already opened re-opening inconsistently (occurring on all platforms)