container commander by sapn95

Firefox containers are excellent and their tooling fights itself. Run several container add-ons together and each answers the same question from its own list, none of them able to see who asked, and the tie-break is a dialog asking you to settle it by hand.

container commander is the arbiter that gives the question one answer.

THE ONE IDEA

A container is a property of a flow, not of a URL.

A sign-in host is shared by every identity you own. A federation endpoint is shared by every application in a tenant. A cloud console hostname carries the region, not the account. No pattern over those strings can answer "which identity is this", because the string genuinely does not know — and a rule that tries will pull a sign-in from one identity into another halfway through, which is a failure that reports itself as something else entirely.

So the decision happens exactly once, at a flow's first request, from the best evidence available. After that the flow is inherited, untouched, to the end.

HOW IT DECIDES

1. Claims — a cooperating extension said "this tab is mine" before it created it. Outranks everything.
2. Inheritance — a redirect, a link click, or a container you chose by hand is left alone without any rule being read.
3. Entry rules — first match over your policy, for tabs that genuinely begin a flow.
4. Leave alone — a named outcome, not an else-branch. Everything unknown, ambiguous or misconfigured lands here.

WHAT IT WILL NOT DO

• Never re-routes a navigation already under way, so a sign-in cannot be pulled between identities.
• Never reopens a form submission: a container change is close-and-reopen, and the body would be lost.
• Never asks when it is unsure. Unknown means it behaves as though it were not installed.
• Keeps no writable rule store of its own, so nothing it holds can drift or come back after you delete it.

THE POLICY IS YOURS

There are no rules in this add-on and no settings screen to add one. The policy arrives read-only through managed storage, from a file your own configuration repository generates. Nothing is uploaded, nothing is synchronised, and a version update cannot change your routing.

Start with dry run: it decides everything and enforces nothing, and the popup shows what it would have done — with a reason for every decision, including the ones where it did nothing.

Open source, MIT: https://github.com/sapn95/container-commander