sequenceDiagram
    actor User
    participant UI as WealthLedger frontend
    participant API as WealthLedger backend
    participant Store as Saved investment data
    participant Broker as T-Bank
    User->>UI: Open income page / apply from,to
    UI->>API: GET income-analytics(accountId or all, from, to)
    API->>Store: Verify session, membership, selected-period coverage and operations
    alt Access denied or invalid period
        API-->>UI: Problem Details (access/input error)
        UI-->>User: Account/period error; preserve last applied data on invalid draft
    else Selected period complete
        Store-->>API: Confirmed selected operations and source state
        API-->>UI: data with selected totals/entries + meta(selected)
        UI-->>User: Totals and executed payment cards, no comparisons
    else Selected period missing or incomplete
        Store-->>API: Incomplete coverage + resource state
        API-->>UI: data null + meta(selected)
        UI-->>User: Loading or recoverable error, no partial final totals
        opt First read of missing historical interval
            API->>Broker: Begin bounded acquisition of missing selected interval
            Broker-->>Store: Publish only confirmed complete result
        end
    end
    Note over API,Store: No previous/year-ago interval is requested for comparison