One mobile app that handles the entire group-trip lifecycle — preference polling, AI-generated itineraries from aggregated tastes, multi-currency cost splitting, and one-click booking through Booking.com/Expedia affiliates — replacing the WhatsApp + Sheets + Splitwise + OTA tab chaos.

What we ship

**Core features (MVP)**

• Group creation + invite via shareable link → friends join in 60 seconds, no signup-friction.
• Preference polling: each person ranks 5 destinations + 5 must-do + 5 must-avoid + budget cap.
• AI itinerary generator: Claude reads aggregated preferences, returns 7-day plan optimized for the group's overlap zone with embedded hotel + activity recommendations.
• Stripe Connect multi-currency split: every expense added by anyone → auto-split with currency conversion, settle-up via Apple Pay/Google Pay/bank transfer at trip end.
• One-click booking via Booking.com + Expedia affiliate — group leader books, others see their share auto-debited at checkout.

**Primary user flow**

1. Sarah finds us via TikTok "group trip planning hack" video, downloads app.

2. Creates group "Tulum Bachelorette 2026", shares invite link in WhatsApp → 7 friends join in 2 minutes.

3. Everyone fills 90-second preference quiz; Claude generates 5-day Tulum itinerary using overlap zone (cenotes + beach club, NOT clubs which 3 vetoed).

4. Group votes Yes → Sarah books hotel through embedded Booking.com (we earn 6% affiliate); other 7 see their $185 share queued.

5. During trip, dinners + Ubers logged in app → auto-split. Trip ends → settle-up in 1 tap.

6. Sarah hits free-tier limit on second trip → upgrades to $4.99/trip Premium for AI itinerary + multi-currency.

**What it looks like**

• **Landing (web)**: hero with phone mockup playing 6-second loop of preference voting → AI itinerary → split → book. Tagline: "Stop planning trips in 5 group chats."
• **App home**: list of active trips (poll status, count of votes received, days until trip). Tap a trip → tabs (Itinerary | Expenses | Bookings | Chat).
• **Itinerary screen**: AI-generated day-by-day with thumbs-up/down on each item; Claude regenerates with feedback.
• **Notification format**: push notifications for "3 of 8 voted, waiting on Alex/Mira/Jordan", "Hotel locked in for Tulum — your share is $185", "Trip settling up — tap to send $42 to Sarah".

**MVP build plan (16 days)**

• Day 1-3: FastAPI + Postgres on Railway, group/trip data model, JWT + invite-link auth.
• Day 4-6: Flutter shell (iOS + Android), home + trip-detail screens, preference polling UI.
• Day 7-9: Claude integration for itinerary generation (RAG over Booking.com hotel data + Google Places).
• Day 10-12: Stripe Connect Express onboarding + multi-currency expense split + Apple Pay / Google Pay.
• Day 13: Booking.com + Expedia affiliate integration (deep links + commission tracking).
• Day 14: Cloudflare Pages landing, App Store + Play Store assets.
• Day 15: TikTok content batch (10 videos), Reddit launch posts.
• Day 16: TestFlight + Play closed-beta, fix critical bugs, ship to stores.

Source signals

• `SIG-20260504-global-life-event-planner-group-trip-coordination` — group travel surge post-pandemic, Gen Z largest spend cohort 2026, no dominant app, 50+ message threads + Splitwise + Sheets pattern, Stripe Connect multi-currency maturity validates feasibility

Reasoning

Three macro signals converge: Gen Z is the largest travel-spend cohort by 2026 (WTTC), and they are group-first not solo-first; Stripe Connect's multi-currency payouts hit maturity in 2024-2025 making cross-border split economically buildable for the first time; PhocusWire Hot 25 2026 explicitly flagged group travel as the largest unmet whitespace in consumer travel apps.

The whitespace is structural: incumbents are locked-in. Splitwise can't pivot to coordination without alienating its core money-split base. TripIt can't pivot to group without losing solo-traveler positioning. WhatsApp can't add structured decision tools without breaking messaging-first UX. None of them can credibly close the full lifecycle (poll → itinerary → split → book) — that gap is exploitable.

Defensive moat: network effect within a trip-group (once all 8 are in the app, switching cost = zero) + booking-data flywheel (recommendations improve with each trip). LTV math: $4.99/trip × 2-3 trips/yr × 3-yr retention = $30-45 plus booking commission of $200-400 per group trip on average → unit economics work at $5 CAC.

Primary risk: Booking.com affiliate API approval is not instant (~3 weeks lead time); fallback is Expedia Group + Hotels.com which have more open partner programs. Apple App Store policy is the secondary risk — we charge premium via web (Stripe) OR via in-app IAP, never bypass.

Quick competitive read

Direct competitor density is **medium** (4-5 named players). Splitwise = money-only, no coordination. TripIt = solo-first, weak group, no payments. Wanderlog = shared notebook, no decision tooling, no payments. WhatsApp = default fallback, no structure. Polarsteps = solo memoir, no planning. Nobody closes the full lifecycle in a single app — white-space exists.

Initial pricing hypothesis

$4.99/trip premium unlock (AI itinerary + multi-currency split + booking integration) plus 5-8% affiliate commission on bookings through embedded Booking.com / Expedia. Free tier supports basic polling + manual coordination for groups up to 4. Annual subscription ($24.99/yr unlimited trips) launches once free → premium conversion baseline established.

Distribution hypothesis

TikTok organic ("group trip planning hack" content) + Instagram Reels + Reddit r/travel + r/solotravel cross-post. Built-in K-factor >1 because each user invites 5-8 friends per trip on average. Paid acquisition deferred until product-market fit signal (>30% Day-7 retention on free tier).