The Panels That Already Existed
I went into C4b thinking I needed to build eight UI panels from scratch. The issue says “wire blocks-ui panels to C4a backend” — but somehow the design process drifted toward building custom Lit components to replace three of them. The adversarial review caught it: work-item-inbox, work-item-detail, and approval-gate are production components in blocks-ui, used by three other CaseHub apps. Building custom replacements was a platform coherence violation hiding behind a reasonable-sounding rationale about “fewer components.”
The corrected approach is simpler. Register the blocks-ui components via hostPanel(), point them at the C4a REST endpoints, and let them manage their own data subscriptions. The dock-workbench treats them like any other panel — defaultOpen: false in the right zone, available on demand.
The real work was the push plumbing
C4a built the incident backend — case definition, SLA policy, risk classifier, thirteen response agents. But it broadcast raw CDI event records to the push topics. FsiIncidentNotifier was firing IncidentCreatedEvent objects directly through EventBroadcaster, while every other push listener in the app wraps events in typed sealed interfaces with a type discriminator.
The inconsistency matters on the client side. When three different event shapes arrive on the same incidents/{caseId} topic — created, SLA breach, resolved — the topicSource accumulator has no way to distinguish them. A type field solves client-side dispatch; accumulate: false solves the overwrite problem by treating the topic as an event stream rather than accumulated state.
So C4b adds IncidentPushPayload (three records) and WorkItemPushPayload (five records, including GateOpened which moved here from the incident domain — it creates a work item, so it belongs with work-item events). Both follow the TradingPushPayload pattern: sealed interface, type discriminator string, convenience constructor that auto-populates the discriminator.
WorkItemLifecycleEvent has a confusing API
The platform fires WorkItemLifecycleEvent for every work item across every application. To filter for fsitrading’s work items, you need event.workItem().scope() — there’s no scope() on the event itself. And workItem() returns null for wire-deserialized events, so the null guard comes first.
Then there’s event.type() vs event.eventType(). The first returns a CloudEvent URI string like "io.casehub.work.workitem.created". The second parses it and returns the WorkEventType enum. A developer writing a switch statement would naturally reach for type() and get a string where they expected an enum. Each mistake compiles.
I captured this as a garden entry — it’s the kind of thing that costs an hour the first time and zero the second.
SLA deadlines belong server-side
The sla-indicator panel needs countdown timers. The CDI events didn’t carry deadline timestamps — IncidentCreatedEvent had severity but not the actual Instant when the claim window expires. Computing deadlines client-side would duplicate the IncidentSeverityDescriptor logic in TypeScript and break the moment SLA windows change.
The fix: FsiIncidentTrigger now computes claimDeadline and completionDeadline at incident creation time (from the descriptor’s Duration plus Instant.now()), stores them in IncidentRecord, carries them through the CDI event, and delivers them in the push payload. When FsiSlaBreachPolicy escalates and the work item’s candidate group changes, FsiWorkItemPushListener broadcasts the updated deadlines so the panel can refresh its countdown.
The timestamps come from a single Instant.now() call in the trigger — the same instant used for the database record, the CDI event, and the push payload. The spec review caught this: computing Instant.now() independently in the notifier would create clock skew between the stored record and the pushed payload.
Eight panels, zero custom components
The trading desk now has eighteen panels — ten from C1-C3 and eight from C4. The C4 panels sit in the right zone as defaultOpen: false, available when an operator opens them. C5b will move them to a dedicated Ops Centre page with proper zone assignments.
Every panel is either a pages-ui DSL composition or a blocks-ui web component. No custom Lit code in this branch. The platform’s component library did the work — we just had to wire the plumbing underneath.