Wire cross-section filter hydration into Board/Schedule/Map per TZ 4.1.8 Table 10

src/features/flights-map/components/FlightsMapStartPage.test.tsx

@@ -9,6 +9,15 @@ import type * as DictionariesModuleNS from "@/shared/dictionaries/index.js";
 import { transformDictionaries } from "@/shared/dictionaries/index.js";
 import type { IDictionaries, IRawDictionaries } from "@/shared/dictionaries/index.js";
 import type { FlightsMapSearchParams } from "../types.js";
+import {
+  resetCrossSectionStore,
+  setMapFilter,
+  setBoardFilter,
+  setScheduleFilter,
+  type MapFilterSnapshot,
+  type BoardFilterSnapshot,
+  type ScheduleFilterSnapshot,
+} from "@/shared/state/crossSectionNavigation.js";
 
 type DictionariesModule = typeof DictionariesModuleNS;
 
@@ -44,8 +53,12 @@ vi.mock("./MapCanvas.js", () => ({
   },
 }));
 
+let lastMapFilterProps: Record<string, unknown> | null = null;
 vi.mock("./FlightsMapFilter.js", () => ({
-  FlightsMapFilter: () => <div data-testid="flights-map-filter" />,
+  FlightsMapFilter: (props: Record<string, unknown>) => {
+    lastMapFilterProps = props;
+    return <div data-testid="flights-map-filter" />;
+  },
 }));
 
 vi.mock("@/env/index.js", () => ({
@@ -491,3 +504,77 @@ describe("FlightsMapStartPage — C.4 integration", () => {
     expect(last?.connections).toBe(1);
   });
 });
+
+// ---------------------------------------------------------------------------
+// TZ §4.1.8 / §4.1.1-R26: Map filter cross-section isolation tests
+// ---------------------------------------------------------------------------
+
+describe("4.1.8 / 4.1.1-R26: Flight-Map filter cross-section isolation", () => {
+  beforeEach(() => {
+    lastMapFilterProps = null;
+    lastMapCanvasProps = null;
+    dictState.dictionaries = buildDictionaries();
+    dictState.loading = false;
+    dictState.error = null;
+    searchState.routes = [];
+    searchState.loading = false;
+    searchState.error = null;
+    resetCrossSectionStore();
+  });
+
+  it("4.1.8: hydrates map filter from map snapshot on mount", () => {
+    const mapSnap: MapFilterSnapshot = {
+      departure: "MOW", arrival: "LED", date: "20260515",
+      showInternal: true, showInternational: false, showTransfers: true,
+    };
+    setMapFilter(mapSnap);
+    render(<FlightsMapStartPage />);
+    const filterValue = lastMapFilterProps!["value"] as Record<string, unknown>;
+    expect(filterValue["departure"]).toBe("MOW");
+    expect(filterValue["arrival"]).toBe("LED");
+    expect(filterValue["domestic"]).toBe(true);
+    expect(filterValue["international"]).toBe(false);
+    expect(filterValue["connections"]).toBe(true);
+  });
+
+  it("4.1.1-R26: Board filter does NOT hydrate flight map", () => {
+    const boardSnap: BoardFilterSnapshot = {
+      mode: "route", departure: "SVO", arrival: "VVO",
+      date: "20260515", timeFrom: "0000", timeTo: "2400",
+      searchExecuted: true,
+    };
+    setBoardFilter(boardSnap);
+    // No map snapshot set
+    render(<FlightsMapStartPage />);
+    const filterValue = lastMapFilterProps!["value"] as Record<string, unknown>;
+    // Map filter should be at defaults, not seeded from board
+    expect(filterValue["departure"]).toBeUndefined();
+    expect(filterValue["arrival"]).toBeUndefined();
+  });
+
+  it("4.1.1-R26: Schedule filter does NOT hydrate flight map", () => {
+    const schedSnap: ScheduleFilterSnapshot = {
+      mode: "route", departure: "KZN", arrival: "AER",
+      dateFrom: "20260511", dateTo: "20260517",
+      timeFrom: "0000", timeTo: "2400",
+      onlyDirect: false, showReturn: false, searchExecuted: true,
+    };
+    setScheduleFilter(schedSnap);
+    // No map snapshot set
+    render(<FlightsMapStartPage />);
+    const filterValue = lastMapFilterProps!["value"] as Record<string, unknown>;
+    // Map filter should be at defaults, not seeded from schedule
+    expect(filterValue["departure"]).toBeUndefined();
+    expect(filterValue["arrival"]).toBeUndefined();
+  });
+
+  it("4.1.8: renders empty filter when no map snapshot is in store", () => {
+    // Store is empty (resetCrossSectionStore called in beforeEach)
+    render(<FlightsMapStartPage />);
+    const filterValue = lastMapFilterProps!["value"] as Record<string, unknown>;
+    expect(filterValue["departure"]).toBeUndefined();
+    expect(filterValue["arrival"]).toBeUndefined();
+    expect(filterValue["domestic"]).toBe(false);
+    expect(filterValue["international"]).toBe(false);
+  });
+});

src/features/flights-map/components/FlightsMapStartPage.tsx

@@ -24,6 +24,10 @@ import { filterRoutes } from "../filterRoutes.js";
 import { buildBuyTicketUrl, escapeHtml } from "../buyTicketUrl.js";
 import { useDictionaries, getCityCodeByAirportCode } from "@/shared/dictionaries/index.js";
 import { getCityZoomLevel } from "../cityCategory.js";
+import {
+  getMapFilter,
+  setMapFilter,
+} from "@/shared/state/crossSectionNavigation.js";
 import type {
   IFlightsMapFilterState,
   FlightsMapSearchParams,
@@ -89,10 +93,25 @@ export const FlightsMapStartPage: FC<FlightsMapStartPageProps> = ({
     error: dictionariesError,
   } = useDictionaries(language);
 
-  const [filterState, setFilterState] = useState<IFlightsMapFilterState>({
-    connections: false,
-    domestic: false,
-    international: false,
+  const [filterState, setFilterState] = useState<IFlightsMapFilterState>(() => {
+    // TZ §4.1.8 / 4.1.1-R26: Map filter is stored independently and NEVER
+    // projected from/to Board or Schedule.
+    const mapSnap = getMapFilter();
+    if (mapSnap) {
+      return {
+        departure: mapSnap.departure ?? undefined,
+        arrival: mapSnap.arrival ?? undefined,
+        date: mapSnap.date ?? undefined,
+        connections: mapSnap.showTransfers,
+        domestic: mapSnap.showInternal,
+        international: mapSnap.showInternational,
+      };
+    }
+    return {
+      connections: false,
+      domestic: false,
+      international: false,
+    };
   });
 
   useGeolocationDefault(dictionaries, filterState, setFilterState);
@@ -161,6 +180,15 @@ export const FlightsMapStartPage: FC<FlightsMapStartPageProps> = ({
 
   const handleFilterChange = useCallback((newState: IFlightsMapFilterState) => {
     setFilterState(newState);
+    // TZ §4.1.8 / 4.1.1-R26: persist map filter independently from Board/Schedule.
+    setMapFilter({
+      departure: newState.departure ?? null,
+      arrival: newState.arrival ?? null,
+      date: newState.date ?? null,
+      showInternal: newState.domestic,
+      showInternational: newState.international,
+      showTransfers: newState.connections,
+    });
   }, []);
 
   const handleMarkerClick = useCallback(

src/features/online-board/components/OnlineBoardFilter.tsx

@@ -18,6 +18,7 @@ import { CityAutocomplete } from "@/ui/city-autocomplete/index.js";
 import { DayQuickPick } from "@/ui/calendar/DayQuickPick.js";
 import { useDictionaries } from "@/shared/dictionaries/index.js";
 import { buildOnlineBoardUrl } from "../url.js";
+import { setBoardFilter } from "@/shared/state/crossSectionNavigation.js";
 import "./OnlineBoardFilter.scss";
 
 function minutesToTime(minutes: number): string {
@@ -233,6 +234,17 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
       const carrier = "SU";
       const num = cleaned;
       if (!num) return;
+
+      // TZ §4.1.8: persist filter snapshot for cross-section hydration.
+      setBoardFilter({
+        mode: "flight-number",
+        flightNumber: `${carrier}${num}`,
+        date: dateParam,
+        timeFrom: "0000",
+        timeTo: "2400",
+        searchExecuted: true,
+      });
+
       const url = buildOnlineBoardUrl({ type: "flight", carrier, flightNumber: num, date: dateParam });
       void navigate(`/${locale}/${url}`);
     },
@@ -273,10 +285,38 @@ export const OnlineBoardFilter: FC<OnlineBoardFilterProps> = ({
 
       let url: string;
       if (depCode && !arrCode) {
+        // TZ §4.1.8: persist filter snapshot for cross-section hydration.
+        setBoardFilter({
+          mode: "departure",
+          departure: depCode,
+          date: dateParam,
+          timeFrom: timeExtras.timeFrom ?? "0000",
+          timeTo: timeExtras.timeTo ?? "2400",
+          searchExecuted: true,
+        });
         url = buildOnlineBoardUrl({ type: "departure", station: depCode, date: dateParam, ...timeExtras });
       } else if (!depCode && arrCode) {
+        // TZ §4.1.8: persist filter snapshot for cross-section hydration.
+        setBoardFilter({
+          mode: "arrival",
+          arrival: arrCode,
+          date: dateParam,
+          timeFrom: timeExtras.timeFrom ?? "0000",
+          timeTo: timeExtras.timeTo ?? "2400",
+          searchExecuted: true,
+        });
         url = buildOnlineBoardUrl({ type: "arrival", station: arrCode, date: dateParam, ...timeExtras });
       } else {
+        // TZ §4.1.8: persist filter snapshot for cross-section hydration.
+        setBoardFilter({
+          mode: "route",
+          departure: depCode,
+          arrival: arrCode,
+          date: dateParam,
+          timeFrom: timeExtras.timeFrom ?? "0000",
+          timeTo: timeExtras.timeTo ?? "2400",
+          searchExecuted: true,
+        });
         url = buildOnlineBoardUrl({ type: "route", departure: depCode, arrival: arrCode, date: dateParam, ...timeExtras });
       }
       void navigate(`/${locale}/${url}`);

src/features/online-board/components/OnlineBoardStartPage.test.tsx

@@ -11,6 +11,13 @@ import { describe, it, expect, vi, beforeEach } from "vitest";
 import { render, screen, fireEvent } from "@testing-library/react";
 import { OnlineBoardStartPage, buildOnlineBoardPrefillState } from "./OnlineBoardStartPage.js";
 import type { PopularRequest } from "@/features/popular-requests/types.js";
+import {
+  resetCrossSectionStore,
+  setScheduleFilter,
+  setBoardFilter,
+  type ScheduleFilterSnapshot,
+  type BoardFilterSnapshot,
+} from "@/shared/state/crossSectionNavigation.js";
 
 const mockNavigate = vi.fn();
 
@@ -58,6 +65,7 @@ vi.mock("@/ui/city-autocomplete/index.js", () => ({
     <input
       data-testid={`${(props["testIdPrefix"] as string) ?? "city-autocomplete"}-input`}
       placeholder={props["placeholder"] as string}
+      defaultValue={(props["value"] as string) ?? ""}
     />
   ),
 }));
@@ -181,3 +189,56 @@ describe("OnlineBoardStartPage", () => {
     expect(mockNavigate).not.toHaveBeenCalled();
   });
 });
+
+// ---------------------------------------------------------------------------
+// TZ §4.1.8: cross-section hydration tests (Board ↔ Schedule)
+// ---------------------------------------------------------------------------
+
+describe("4.1.8: Online-Board hydrates from cross-section store on mount", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    resetCrossSectionStore();
+  });
+
+  it("4.1.8: hydrates departure + arrival from Schedule filter (projected) when no own state", () => {
+    const schedSnap: ScheduleFilterSnapshot = {
+      mode: "route", departure: "MOW", arrival: "LED",
+      dateFrom: "20260511", dateTo: "20260517",
+      timeFrom: "0000", timeTo: "2400",
+      onlyDirect: false, showReturn: false, searchExecuted: true,
+    };
+    setScheduleFilter(schedSnap);
+    render(<OnlineBoardStartPage />);
+    // departure input should be seeded with "MOW"
+    const depInput = screen.getByTestId("route-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("MOW");
+    const arrInput = screen.getByTestId("route-arrival-input") as HTMLInputElement;
+    expect(arrInput.defaultValue).toBe("LED");
+  });
+
+  it("4.1.8: uses own board snapshot (not schedule) when board state is set", () => {
+    // Set board first (own state)
+    setBoardFilter({
+      mode: "route", departure: "KZN", arrival: "AER",
+      date: "20260515", timeFrom: "0000", timeTo: "2400",
+      searchExecuted: false,
+    });
+    // Also set schedule — it should be ignored since board is present
+    setScheduleFilter({
+      mode: "route", departure: "SVO", arrival: "VVO",
+      dateFrom: "20260511", dateTo: "20260517",
+      timeFrom: "0000", timeTo: "2400",
+      onlyDirect: false, showReturn: false, searchExecuted: true,
+    });
+    render(<OnlineBoardStartPage />);
+    const depInput = screen.getByTestId("route-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("KZN");
+  });
+
+  it("4.1.8: renders empty filter when both board and schedule store are empty", () => {
+    // No cross-section state set
+    render(<OnlineBoardStartPage />);
+    const depInput = screen.getByTestId("route-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("");
+  });
+});

src/features/online-board/components/OnlineBoardStartPage.tsx

@@ -12,7 +12,7 @@
  * @module
  */
 
-import { type FC, useCallback, useState } from "react";
+import { type FC, useCallback, useState, useEffect } from "react";
 import { useNavigate } from "@modern-js/runtime/router";
 import { useLocale } from "@/i18n/useLocale.js";
 import { useTranslation } from "@/i18n/provider.js";
@@ -26,6 +26,12 @@ import {
   readAndClearTransientPrefill,
   writeTransientPrefill,
 } from "@/shared/state/transientPrefill.js";
+import {
+  getBoardFilter,
+  getScheduleFilter,
+  setBoardFilter,
+  projectScheduleToBoard,
+} from "@/shared/state/crossSectionNavigation.js";
 import {
   useDictionaries,
   getCityCodeByAirportCode,
@@ -97,12 +103,34 @@ export const OnlineBoardStartPage: FC = () => {
   // Read-and-clear any prefill the previous page wrote. Stored in
   // useState (with a one-shot initializer) so React strict mode's
   // double-render doesn't lose the value on the second pass.
-  const [prefill, setPrefill] = useState<OnlineBoardPrefillState>(
-    () =>
-      readAndClearTransientPrefill<OnlineBoardPrefillState>(
-        ONLINE_BOARD_PREFILL_SLOT,
-      ) ?? {},
-  );
+  // Falls back to cross-section store projection (Schedule → Board) per
+  // TZ §4.1.8 Table 10 when no transient prefill is present.
+  const [prefill, setPrefill] = useState<OnlineBoardPrefillState>(() => {
+    const transient = readAndClearTransientPrefill<OnlineBoardPrefillState>(
+      ONLINE_BOARD_PREFILL_SLOT,
+    );
+    if (transient) return transient;
+
+    // TZ §4.1.8: try own snapshot first, then project from Schedule.
+    const boardSnap = getBoardFilter();
+    if (boardSnap) {
+      return {
+        tab: "route",
+        departure: boardSnap.departure,
+        arrival: boardSnap.arrival,
+      };
+    }
+    const schedSnap = getScheduleFilter();
+    if (schedSnap) {
+      const projected = projectScheduleToBoard(schedSnap);
+      return {
+        tab: "route",
+        departure: projected.departure,
+        arrival: projected.arrival,
+      };
+    }
+    return {};
+  });
   // Same-page popular clicks need to re-mount the filter so its
   // useState initial values pick up the new prefill. Key bump does it.
   const [filterKey, setFilterKey] = useState(0);

src/features/schedule/components/ScheduleStartPage.test.tsx

@@ -12,6 +12,13 @@ import { render, screen, fireEvent } from "@testing-library/react";
 import { ScheduleStartPage } from "./ScheduleStartPage.js";
 import { sessionStore } from "@/shared/storage.js";
 import type { PopularRequest } from "@/features/popular-requests/types.js";
+import {
+  resetCrossSectionStore,
+  setBoardFilter,
+  setScheduleFilter,
+  type BoardFilterSnapshot,
+  type ScheduleFilterSnapshot,
+} from "@/shared/state/crossSectionNavigation.js";
 
 const mockNavigate = vi.fn();
 
@@ -63,6 +70,15 @@ vi.mock("@/shared/hooks/useCitySearch.js", () => ({
   useCitySearch: () => ({ suggestions: [], search: vi.fn() }),
 }));
 
+vi.mock("@/ui/city-autocomplete/index.js", () => ({
+  CityAutocomplete: (props: Record<string, unknown>) => (
+    <input
+      data-testid={`${(props["testIdPrefix"] as string) ?? "city-autocomplete"}-input`}
+      defaultValue={(props["value"] as string) ?? ""}
+    />
+  ),
+}));
+
 vi.mock("@/ui/layout/SearchHistory.js", () => ({
   SearchHistory: () => <div data-testid="search-history" />,
 }));
@@ -114,3 +130,53 @@ describe("ScheduleStartPage", () => {
     expect((roundTripCheckbox as HTMLInputElement).checked).toBe(true);
   });
 });
+
+// ---------------------------------------------------------------------------
+// TZ §4.1.8: cross-section hydration tests (Board → Schedule)
+// ---------------------------------------------------------------------------
+
+describe("4.1.8: Schedule hydrates from cross-section store on mount", () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+    sessionStore.clear();
+    resetCrossSectionStore();
+  });
+
+  it("4.1.8: hydrates departure + arrival from Board filter (projected) when no own state", () => {
+    const boardSnap: BoardFilterSnapshot = {
+      mode: "route", departure: "MOW", arrival: "LED",
+      date: "20260515", timeFrom: "0600", timeTo: "2200",
+      searchExecuted: true,
+    };
+    setBoardFilter(boardSnap);
+    render(<ScheduleStartPage />);
+    const depInput = screen.getByTestId("schedule-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("MOW");
+    const arrInput = screen.getByTestId("schedule-arrival-input") as HTMLInputElement;
+    expect(arrInput.defaultValue).toBe("LED");
+  });
+
+  it("4.1.8: uses own schedule snapshot (not board) when schedule state is set", () => {
+    setScheduleFilter({
+      mode: "route", departure: "KZN", arrival: "AER",
+      dateFrom: "20260511", dateTo: "20260517",
+      timeFrom: "0000", timeTo: "2400",
+      onlyDirect: false, showReturn: false, searchExecuted: false,
+    });
+    // Also set board — it should be ignored since schedule snapshot is present
+    setBoardFilter({
+      mode: "route", departure: "SVO", arrival: "VVO",
+      date: "20260515", timeFrom: "0000", timeTo: "2400",
+      searchExecuted: true,
+    });
+    render(<ScheduleStartPage />);
+    const depInput = screen.getByTestId("schedule-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("KZN");
+  });
+
+  it("4.1.8: renders empty filter when both schedule and board store are empty", () => {
+    render(<ScheduleStartPage />);
+    const depInput = screen.getByTestId("schedule-departure-input") as HTMLInputElement;
+    expect(depInput.defaultValue).toBe("");
+  });
+});

src/features/schedule/components/ScheduleStartPage.tsx

@@ -28,6 +28,12 @@ import {
   readAndClearTransientPrefill,
   writeTransientPrefill,
 } from "@/shared/state/transientPrefill.js";
+import {
+  getScheduleFilter,
+  getBoardFilter,
+  setScheduleFilter,
+  projectBoardToSchedule,
+} from "@/shared/state/crossSectionNavigation.js";
 import {
   useDictionaries,
   getCityCodeByAirportCode,
@@ -92,12 +98,34 @@ export const ScheduleStartPage: FC = () => {
   const { dictionaries } = useDictionaries(language);
 
   // One-shot read of any prefill the previous page wrote.
-  const [prefill] = useState<SchedulePrefillState>(
-    () =>
-      readAndClearTransientPrefill<SchedulePrefillState>(
-        SCHEDULE_PREFILL_SLOT,
-      ) ?? {},
-  );
+  // Falls back to cross-section store projection (Board → Schedule) per
+  // TZ §4.1.8 Table 10 when no transient prefill is present.
+  const [prefill] = useState<SchedulePrefillState>(() => {
+    const transient = readAndClearTransientPrefill<SchedulePrefillState>(
+      SCHEDULE_PREFILL_SLOT,
+    );
+    if (transient) return transient;
+
+    // TZ §4.1.8: try own snapshot first, then project from Board.
+    const schedSnap = getScheduleFilter();
+    if (schedSnap) {
+      return {
+        departure: schedSnap.departure,
+        arrival: schedSnap.arrival,
+        withReturn: schedSnap.showReturn,
+      };
+    }
+    const boardSnap = getBoardFilter();
+    if (boardSnap) {
+      const projected = projectBoardToSchedule(boardSnap);
+      return {
+        departure: projected.departure,
+        arrival: projected.arrival,
+        withReturn: false,
+      };
+    }
+    return {};
+  });
 
   const today = new Date();
 
@@ -184,6 +212,20 @@ export const ScheduleStartPage: FC = () => {
         });
       }
 
+      // TZ §4.1.8: persist filter snapshot for cross-section hydration.
+      setScheduleFilter({
+        mode: "route",
+        departure: dep,
+        arrival: arr,
+        dateFrom: dateFromParam,
+        dateTo: dateToParam,
+        timeFrom: outbound.timeFrom ?? "0000",
+        timeTo: outbound.timeTo ?? "2400",
+        onlyDirect: directOnly,
+        showReturn: isRoundTrip,
+        searchExecuted: true,
+      });
+
       void navigate(`/${locale}/${url}`);
     },
     [departureCode, arrivalCode, dateFrom, dateTo, timeRange, directOnly, isRoundTrip, returnDateFrom, returnDateTo, returnTimeRange, navigate, locale],