ADR-0094: The routing builder is hosted by the Routing screen, and declares a queue inline

• Status: accepted; supersedes the host-screen clause of ADR-0090 D3
• Date: 2026-09-21
• Deciders: Artemis Studio maintainers

Context

ADR-0090 D3 put the routing builder in feature/brokerconfig and made it a tab of the Configuration screen, beside Declared and History. Two parts of that decision were argued for: the builder edits the declaration, so its code belongs in the module that owns the declaration; and a builder in feature/routing would need a new frontend edge and a new backend dependency to reach the document. Both arguments are still right.

The third part — which screen shows it — was not argued for, and it is the part operators trip over. An operator looking for "where do I build a divert" goes to Routing, which lists diverts and bridges. The builder was reached from there only through a link to another screen's fourth tab. Configuration is where an operator goes to apply what is declared, not to draw it.

The builder also had no way to create the queue a divert needs. A divert into an address with no queue drops what it diverts, so composing a divert to a new address meant closing the editor, switching to another screen, declaring the address and its queue, and coming back.

The kernel already has the mechanism for one feature to show a panel on another's screen without importing it: a slot. admin.tabs is a tab-shaped one.

Decision

D1 — The builder is a tab of the Routing screen. The kernel gains a routing.tabs slot ({ clusterId }), modelled on admin.tabs: each contribution is a tab after Diverts and Bridges, labelled with its title, whose id is the tab's ?tab=. feature/brokerconfig contributes RoutingBuilderTab with id builder, title "Builder". The path is Routing in the navigation, then Builder: two clicks.

D2 — Ownership does not move. The builder's code, its editors and the declaration it edits stay in feature/brokerconfig, so ADR-0090 D3's module argument holds unchanged and there is no new feature edge. RoutingBuilderTab brings what the Configuration screen used to hand the builder: the declaration query with its loading and error states, the write and apply gates, its URL state, and the same ReviewApplyDrawer behind a "Review & apply" control in the builder's toolbar. There is still one plan and one apply (ADR-0090 D1).

D3 — Routing's URL carries a contributed tab's keys without knowing them. The routing route accepts any string tab and passes through section, item, anchor and selected as strings. A contribution narrows them to what it accepts; an unknown tab falls back to Diverts.

D4 — The Configuration screen's routing tab is removed, with no redirect. Its tabs are Declared & live, History and Recommended. ?tab=routing on Configuration now opens Declared & live. A disabled brokerconfig removes the Builder tab, as a disabled feature is absent from every surface; the Bridges tab's empty state then does not point at it.

D5 — A divert's target queue is declared inline. The divert editor's "To address" is a combobox of the declared addresses whose last option, when the typed address is not declared, is Create queue '<address>'…. It opens a section inside the drawer — queue name, routing type, durability — that saves the address and its queue to the declaration as their own revision ("Added queue X") and leaves the divert open against the new revision. The queue is declared, not created on a broker: it shows on the canvas at once as declared and not yet applied, and it reaches the brokers in the same apply as the divert, so the divert never goes live ahead of its queue. This changes nothing in ADR-0090 D1 or D2. The builder's toolbar also has "Add queue", which opens the address editor with a queue row to name.

Consequences

Good: the builder is where an operator looks for it, and Routing becomes the one place for routing — what runs (Diverts, Bridges) and what is declared (Builder).

Good: no new module, feature edge, dependency, permission or nav group; one kernel slot with one consumer.

Good: composing a divert to a new address is one flow in one drawer, keyboard-complete.

Bad: the builder's URL keys now live on a route that does not own them, typed as plain strings there and narrowed by the builder. A second contributor to routing.tabs that wants keys of its own will have to add them to the routing route's pass-through list.

Bad: a saved link to configuration?tab=routing lands on Declared & live. There is no redirect, by the project's rule against compatibility paths.

Bad: an inline queue is a revision of its own, so a divert composed with a new queue is two revisions in the history rather than one.

Alternatives considered

• Keep the builder on Configuration and improve the link from Routing. Rejected: it keeps the builder on the screen operators go to apply, not to author, and the link is still a jump to another screen's fourth tab.
• Move the builder into feature/routing. Rejected for the reasons ADR-0090 D3 gives: a new frontend edge and backend dependency to reach the document, and an editor of the declaration outside its owner.
• Create the queue on the brokers at once, through the queues API. Rejected: it is a second write path the builder does not have (ADR-0090 D1); the queue would show as observed and not declared, would appear only after a drift evaluation, and would go live ahead of the divert.
• A nested modal for the new queue. Rejected: a modal over a drawer splits focus and Escape between two layers; a section inside the drawer keeps the divert in view.