feat(airtrail): import connecting flights as one multi-leg booking

AirTrail flights always imported as separate single-leg reservations, so a
layover could not be expressed and the connection country ended up counted
as visited in Atlas (#1535).

The import picker now detects connection chains among the listed flights —
each leg departing from the airport the previous one landed at, onward
within 24 hours, and never back to the origin (an out-and-back is a return,
not a connection) — and offers to import each chain as one flight with
layover stops, on by default. The joined booking keeps per-leg airline,
flight number, times and seat in metadata.legs, files every leg on its own
trip day, and mirrors the first/last leg flat, exactly like the manual
multi-leg form. With the connection stored as a stop endpoint, the existing
Atlas role filter excludes the layover country on its own.

AirTrail has no multi-leg flight a joined booking could round-trip to, so
it imports detached from live sync, with every source flight id recorded in
metadata.airtrail_ids — the picker and the server-side dedupe both treat
those legs as imported, per leg, even across trip members. The server
re-validates each requested chain and falls back to individual imports when
it does not actually connect.

client/src/components/Planner/AirTrailImportModal.test.tsx

@@ -0,0 +1,202 @@
+// FE-PLANNER-AIRTRAIL-001 to FE-PLANNER-AIRTRAIL-008
+import { render, screen, waitFor } from '../../../tests/helpers/render';
+import userEvent from '@testing-library/user-event';
+import { http, HttpResponse } from 'msw';
+import { server } from '../../../tests/helpers/msw/server';
+import { useAuthStore } from '../../store/authStore';
+import { useTripStore } from '../../store/tripStore';
+import { resetAllStores, seedStore } from '../../../tests/helpers/store';
+import { buildUser, buildTrip, buildReservation } from '../../../tests/helpers/factories';
+import type { AirtrailFlight } from '@trek/shared';
+import AirTrailImportModal, { detectConnections } from './AirTrailImportModal';
+
+const flight = (over: Partial<AirtrailFlight> = {}): AirtrailFlight => ({
+  id: '101',
+  fromCode: 'BRU',
+  fromName: 'Brussels',
+  toCode: 'HEL',
+  toName: 'Helsinki-Vantaa',
+  date: '2026-08-01',
+  departure: '2026-08-01T06:00:00.000+00:00',
+  arrival: '2026-08-01T09:30:00.000+00:00',
+  airline: 'Finnair',
+  flightNumber: 'AY1502',
+  aircraft: null,
+  seatClass: 'economy',
+  ...over,
+});
+
+const legHelJfk = (): AirtrailFlight =>
+  flight({
+    id: '102',
+    fromCode: 'HEL',
+    fromName: 'Helsinki-Vantaa',
+    toCode: 'JFK',
+    toName: 'John F. Kennedy Intl.',
+    departure: '2026-08-01T11:00:00.000+00:00',
+    arrival: '2026-08-01T19:00:00.000+00:00',
+    flightNumber: 'AY15',
+  });
+
+const unrelatedFlight = (): AirtrailFlight =>
+  flight({
+    id: '103',
+    fromCode: 'LHR',
+    fromName: 'London Heathrow',
+    toCode: 'JFK',
+    toName: 'John F. Kennedy Intl.',
+    date: '2026-08-05',
+    departure: '2026-08-05T10:00:00.000+00:00',
+    arrival: '2026-08-05T18:00:00.000+00:00',
+    flightNumber: 'BA117',
+  });
+
+describe('detectConnections (#1535)', () => {
+  it('FE-PLANNER-AIRTRAIL-001: chains flights that connect at the same airport within 24h', () => {
+    const chains = detectConnections([legHelJfk(), flight(), unrelatedFlight()]);
+    expect(chains).toHaveLength(1);
+    expect(chains[0].map(f => f.id)).toEqual(['101', '102']);
+  });
+
+  it('FE-PLANNER-AIRTRAIL-002: does not chain when the layover exceeds 24h', () => {
+    const late = { ...legHelJfk(), date: '2026-08-03', departure: '2026-08-03T11:00:00.000+00:00', arrival: '2026-08-03T19:00:00.000+00:00' };
+    expect(detectConnections([flight(), late])).toHaveLength(0);
+  });
+
+  it('FE-PLANNER-AIRTRAIL-003: skips flights without instants instead of guessing', () => {
+    expect(detectConnections([flight({ departure: null, arrival: null }), legHelJfk()])).toHaveLength(0);
+  });
+
+  it('FE-PLANNER-AIRTRAIL-009: does not chain an out-and-back return into a bogus connection', () => {
+    const returnFlight = flight({
+      id: '105',
+      fromCode: 'HEL',
+      fromName: 'Helsinki-Vantaa',
+      toCode: 'BRU',
+      toName: 'Brussels',
+      departure: '2026-08-01T18:00:00.000+00:00',
+      arrival: '2026-08-01T21:30:00.000+00:00',
+      flightNumber: 'AY1503',
+    });
+    expect(detectConnections([flight(), returnFlight])).toHaveLength(0);
+  });
+});
+
+describe('AirTrailImportModal', () => {
+  const defaultProps = { isOpen: true, onClose: vi.fn(), tripId: 1 };
+
+  beforeEach(() => {
+    resetAllStores();
+    seedStore(useAuthStore, { user: buildUser(), isAuthenticated: true });
+    seedStore(useTripStore, {
+      trip: buildTrip({ id: 1, start_date: '2026-08-01', end_date: '2026-08-10' }),
+      reservations: [],
+    });
+    server.use(
+      http.get('/api/integrations/airtrail/flights', () =>
+        HttpResponse.json({ flights: [flight(), legHelJfk(), unrelatedFlight()] }),
+      ),
+      http.get('/api/trips/1/reservations', () => HttpResponse.json({ reservations: [] })),
+    );
+  });
+
+  it('FE-PLANNER-AIRTRAIL-004: offers to join a detected connection, on by default', async () => {
+    render(<AirTrailImportModal {...defaultProps} />);
+    const joinRow = await screen.findByText(/one flight with a layover in HEL/i);
+    expect(joinRow).toBeInTheDocument();
+    // No join offer for the unrelated flight.
+    expect(screen.queryByText(/layover in JFK/i)).not.toBeInTheDocument();
+  });
+
+  it('FE-PLANNER-AIRTRAIL-005: sends the chain as a connection on import', async () => {
+    const user = userEvent.setup();
+    let body: any = null;
+    server.use(
+      http.post('/api/trips/1/reservations/import/airtrail', async ({ request }) => {
+        body = await request.json();
+        return HttpResponse.json({ imported: body.flightIds, skipped: [] });
+      }),
+    );
+    render(<AirTrailImportModal {...defaultProps} />);
+    await screen.findByText(/one flight with a layover in HEL/i);
+    await user.click(screen.getByRole('button', { name: /Import 3/i }));
+    await waitFor(() => expect(body).not.toBeNull());
+    expect([...body.flightIds].sort()).toEqual(['101', '102', '103']);
+    expect(body.connections).toEqual([['101', '102']]);
+  });
+
+  it('FE-PLANNER-AIRTRAIL-006: sends no connection when the join is toggled off', async () => {
+    const user = userEvent.setup();
+    let body: any = null;
+    server.use(
+      http.post('/api/trips/1/reservations/import/airtrail', async ({ request }) => {
+        body = await request.json();
+        return HttpResponse.json({ imported: body.flightIds, skipped: [] });
+      }),
+    );
+    render(<AirTrailImportModal {...defaultProps} />);
+    await user.click(await screen.findByText(/one flight with a layover in HEL/i));
+    await user.click(screen.getByRole('button', { name: /Import 3/i }));
+    await waitFor(() => expect(body).not.toBeNull());
+    expect(body.connections).toBeUndefined();
+  });
+
+  it('FE-PLANNER-AIRTRAIL-007: re-enabling the join selects all of its legs', async () => {
+    const user = userEvent.setup();
+    render(<AirTrailImportModal {...defaultProps} />);
+    const joinRow = await screen.findByText(/one flight with a layover in HEL/i);
+    // Deselect one member — the join reads unchecked, one click brings both back.
+    await user.click(screen.getByText('Finnair AY15'));
+    expect(screen.getByRole('button', { name: /Import 2/i })).toBeInTheDocument();
+    await user.click(joinRow);
+    expect(screen.getByRole('button', { name: /Import 3/i })).toBeInTheDocument();
+  });
+
+  it('FE-PLANNER-AIRTRAIL-010: a surviving sub-chain keeps its join offer when a later leg was already imported', async () => {
+    const legJfkLax = flight({
+      id: '106',
+      fromCode: 'JFK',
+      fromName: 'John F. Kennedy Intl.',
+      toCode: 'LAX',
+      toName: 'Los Angeles Intl.',
+      departure: '2026-08-01T21:00:00.000+00:00',
+      arrival: '2026-08-02T00:30:00.000+00:00',
+      flightNumber: 'AY99',
+    });
+    seedStore(useTripStore, {
+      trip: buildTrip({ id: 1, start_date: '2026-08-01', end_date: '2026-08-10' }),
+      reservations: [
+        buildReservation({ type: 'flight', external_source: 'airtrail', external_id: '106' }) as any,
+      ],
+    });
+    server.use(
+      http.get('/api/integrations/airtrail/flights', () =>
+        HttpResponse.json({ flights: [flight(), legHelJfk(), legJfkLax] }),
+      ),
+    );
+    render(<AirTrailImportModal {...defaultProps} />);
+    // BRU→HEL→JFK still connects even though JFK→LAX is gone from the pool.
+    expect(await screen.findByText(/one flight with a layover in HEL/i)).toBeInTheDocument();
+    expect(screen.getByText(/^Imported$/)).toBeInTheDocument();
+  });
+
+  it('FE-PLANNER-AIRTRAIL-008: legs of a joined import are marked imported via metadata.airtrail_ids', async () => {
+    seedStore(useTripStore, {
+      trip: buildTrip({ id: 1, start_date: '2026-08-01', end_date: '2026-08-10' }),
+      reservations: [
+        buildReservation({
+          type: 'flight',
+          external_source: 'airtrail',
+          external_id: '101',
+          metadata: JSON.stringify({ airtrail_ids: ['101', '102'] }),
+        }) as any,
+      ],
+    });
+    render(<AirTrailImportModal {...defaultProps} />);
+    await screen.findByText('Finnair AY1502');
+    // Both legs disabled — including the one whose id only lives in the metadata.
+    expect(screen.getAllByText(/^Imported$/)).toHaveLength(2);
+    // A chain with an imported member cannot be joined again.
+    expect(screen.queryByText(/one flight with a layover/i)).not.toBeInTheDocument();
+  });
+});

client/src/components/Planner/AirTrailImportModal.tsx

@@ -7,6 +7,7 @@ import { useTranslation } from '../../i18n'
 import { useToast } from '../shared/Toast'
 import { airtrailApi, reservationsApi } from '../../api/client'
 import { useTripStore } from '../../store/tripStore'
+import { parseReservationMetadata } from '../../utils/flightLegs'
 
 interface AirTrailImportModalProps {
   isOpen: boolean
@@ -15,6 +16,40 @@ interface AirTrailImportModalProps {
   pushUndo?: (label: string, undoFn: () => Promise<void> | void) => void
 }
 
+/**
+ * Ordered chains of connecting flights — each arrives where the next departs,
+ * onward within 24 h — that the picker offers to import as ONE multi-leg
+ * booking with the connection as a layover stop (#1535). A flight landing back
+ * at the chain's origin is a return, not a connection, so a same-day
+ * out-and-back never gets a join offer. Same rules the server re-validates
+ * with.
+ */
+export function detectConnections(flights: AirtrailFlight[]): AirtrailFlight[][] {
+  const sorted = flights
+    .filter(f => f.departure && f.arrival && f.fromCode && f.toCode)
+    .sort((a, b) => Date.parse(a.departure!) - Date.parse(b.departure!))
+  const chains: AirtrailFlight[][] = []
+  let chain: AirtrailFlight[] = []
+  for (const f of sorted) {
+    const prev = chain[chain.length - 1]
+    if (prev) {
+      const gap = Date.parse(f.departure!) - Date.parse(prev.arrival!)
+      if (
+        prev.toCode!.toUpperCase() === f.fromCode!.toUpperCase() &&
+        f.toCode!.toUpperCase() !== chain[0].fromCode!.toUpperCase() &&
+        gap >= 0 && gap <= 24 * 3600 * 1000
+      ) {
+        chain.push(f)
+        continue
+      }
+    }
+    if (chain.length > 1) chains.push(chain)
+    chain = [f]
+  }
+  if (chain.length > 1) chains.push(chain)
+  return chains
+}
+
 /** Locale-aware date (e.g. de → 13.06.2026, en-US → 06/13/2026). */
 function fmtDate(d: string | null, locale: string): string {
   if (!d) return ''
@@ -44,11 +79,16 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
   const [flights, setFlights] = useState<AirtrailFlight[]>([])
   const [selected, setSelected] = useState<Set<string>>(() => new Set())
 
-  // AirTrail flight ids already linked to a reservation in this trip.
+  // AirTrail flight ids already linked to a reservation in this trip. A joined
+  // multi-leg import carries only its first leg in external_id — the other legs
+  // sit in metadata.airtrail_ids (#1535).
   const importedIds = useMemo(() => {
     const set = new Set<string>()
     for (const r of reservations) {
-      if (r.external_source === 'airtrail' && r.external_id) set.add(String(r.external_id))
+      if (r.external_source !== 'airtrail') continue
+      if (r.external_id) set.add(String(r.external_id))
+      const ids = parseReservationMetadata(r).airtrail_ids
+      if (Array.isArray(ids)) for (const id of ids) set.add(String(id))
     }
     return set
   }, [reservations])
@@ -56,10 +96,27 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
   const inRange = (f: AirtrailFlight): boolean =>
     !!(f.date && trip?.start_date && trip?.end_date && f.date >= trip.start_date && f.date <= trip.end_date)
 
+  // Detected connection chains that can still be joined. Already-imported
+  // flights are excluded BEFORE detection so a surviving sub-chain (e.g. the
+  // first two legs when the third was imported earlier) still gets its offer.
+  // Joining is on by default; joinOff remembers the chains the user opted out of.
+  const chains = useMemo(
+    () => detectConnections(flights.filter(f => !importedIds.has(f.id))),
+    [flights, importedIds],
+  )
+  const chainKey = (chain: AirtrailFlight[]) => chain.map(f => f.id).join('+')
+  const chainOf = useMemo(() => {
+    const map = new Map<string, AirtrailFlight[]>()
+    for (const chain of chains) for (const f of chain) map.set(f.id, chain)
+    return map
+  }, [chains])
+  const [joinOff, setJoinOff] = useState<Set<string>>(() => new Set())
+
   useEffect(() => {
     if (!isOpen) return
     setError('')
     setSelected(new Set())
+    setJoinOff(new Set())
     setLoading(true)
     airtrailApi
       .flights()
@@ -94,6 +151,28 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
     })
   }
 
+  const chainJoined = (chain: AirtrailFlight[]) =>
+    !joinOff.has(chainKey(chain)) && chain.every(f => selected.has(f.id))
+
+  const toggleJoin = (chain: AirtrailFlight[]) => {
+    const key = chainKey(chain)
+    if (chainJoined(chain)) {
+      setJoinOff(prev => new Set(prev).add(key))
+    } else {
+      // Turning the join on implies wanting all of its legs.
+      setJoinOff(prev => {
+        const next = new Set(prev)
+        next.delete(key)
+        return next
+      })
+      setSelected(prev => {
+        const next = new Set(prev)
+        for (const f of chain) next.add(f.id)
+        return next
+      })
+    }
+  }
+
   const handleClose = () => { onClose() }
 
   const handleImport = async () => {
@@ -102,7 +181,8 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
     setImporting(true)
     setError('')
     try {
-      const result: AirtrailImportResult = await airtrailApi.import(tripId, ids)
+      const connections = chains.filter(chainJoined).map(chain => chain.map(f => f.id))
+      const result: AirtrailImportResult = await airtrailApi.import(tripId, ids, connections)
       await loadReservations(tripId)
 
       const imported = result.imported ?? []
@@ -175,6 +255,58 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
     )
   }
 
+  const renderChain = (chain: AirtrailFlight[]) => {
+    const joined = chainJoined(chain)
+    const stops = chain.slice(0, -1).map(f => f.toCode ?? f.toName ?? '?').join(', ')
+    return (
+      <div key={chainKey(chain)} style={{ border: '1px solid var(--border-primary)', borderRadius: 12, padding: '8px 8px 0', marginBottom: 8 }}>
+        {chain.map(renderFlight)}
+        <button
+          onClick={() => toggleJoin(chain)}
+          className="bg-transparent"
+          style={{
+            display: 'flex', alignItems: 'center', gap: 10, width: '100%', textAlign: 'left',
+            border: 'none', borderTop: '1px solid var(--border-faint)', borderRadius: 0,
+            padding: '9px 4px 10px', cursor: 'pointer', fontFamily: 'inherit',
+          }}
+        >
+          <span style={{
+            flexShrink: 0, width: 16, height: 16, borderRadius: 5,
+            border: `1.5px solid ${joined ? 'var(--accent)' : 'var(--border-primary)'}`,
+            background: joined ? 'var(--accent)' : 'transparent',
+            display: 'flex', alignItems: 'center', justifyContent: 'center',
+          }}>
+            {joined && <Check size={11} color="var(--accent-text)" strokeWidth={3} />}
+          </span>
+          <span style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', color: 'var(--text-primary)' }}>
+            {t('reservations.airtrail.joinConnection', { stops })}
+          </span>
+        </button>
+      </div>
+    )
+  }
+
+  // A chain renders once as a group, at the position of its first listed leg —
+  // its other legs are swallowed wherever else they would appear. Computed per
+  // section up front so a chain straddling the trip range can't leave the other
+  // section holding nothing but its header.
+  const sectionItems = useMemo(() => {
+    const rendered = new Set<string>()
+    const build = (list: AirtrailFlight[]) =>
+      list.flatMap((f): Array<{ key: string; chain?: AirtrailFlight[]; flight?: AirtrailFlight }> => {
+        const chain = chainOf.get(f.id)
+        if (!chain) return [{ key: f.id, flight: f }]
+        const key = chain.map(c => c.id).join('+')
+        if (rendered.has(key)) return []
+        rendered.add(key)
+        return [{ key, chain }]
+      })
+    return { during: build(during), others: build(others) }
+  }, [during, others, chainOf])
+
+  const renderItem = (item: { chain?: AirtrailFlight[]; flight?: AirtrailFlight }) =>
+    item.chain ? renderChain(item.chain) : renderFlight(item.flight!)
+
   return ReactDOM.createPortal(
     <div
       className="bg-[rgba(0,0,0,0.4)]"
@@ -213,21 +345,21 @@ export default function AirTrailImportModal({ isOpen, onClose, tripId, pushUndo
             </div>
           )}
 
-          {!loading && during.length > 0 && (
+          {!loading && sectionItems.during.length > 0 && (
             <>
               <div style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', fontWeight: 700, color: 'var(--text-primary)', margin: '2px 0 8px' }}>
                 {t('reservations.airtrail.duringTrip')}
               </div>
-              {during.map(renderFlight)}
+              {sectionItems.during.map(renderItem)}
             </>
           )}
 
-          {!loading && others.length > 0 && (
+          {!loading && sectionItems.others.length > 0 && (
             <>
-              <div style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', fontWeight: 700, color: 'var(--text-faint)', margin: `${during.length > 0 ? 14 : 2}px 0 8px` }}>
+              <div style={{ fontSize: 'calc(12px * var(--fs-scale-body, 1))', fontWeight: 700, color: 'var(--text-faint)', margin: `${sectionItems.during.length > 0 ? 14 : 2}px 0 8px` }}>
                 {t('reservations.airtrail.otherFlights')}
               </div>
-              {others.map(renderFlight)}
+              {sectionItems.others.map(renderItem)}
             </>
           )}