2026-05-31 · XingAI Travel AI — `xingai-travel-ai`

Travel AI as a Decision System: Compare First, Book Second

UI는 한국어입니다. 글 본문은 아직 영어 또는 중국어만 있습니다.

The problem we refused to solve

Most travel sites answer: “Here are 400 flights.”

Our user is stuck earlier: “Should I even go to Lisbon — really?”

Booking inventory is a solved UX pattern. Destination choice under real constraints is not. XingAI Travel AI (travel.xingai.app) is built for that moment — same decision-system instinct as Meal Coach and Invest AI, applied to trips.

Product shorthand: compare first, plan second. Not another OTA wall.

What shipped in the app

flowchart TB
  subgraph decide["/decide"]
    H["Hero + help accordion"]
    M{"Mode toggle"}
    T["TripForm + style/pace"]
    I["InspireForm · Surprise me"]
    C["Compare CTA"]
  end

  M -->|Know trip| T
  M -->|Surprise me| I
  T --> C
  I --> C
  C --> API["/api/compare or /api/inspire"]
  API --> S["sessionStorage"]
  S --> R["/result · winner + table + book-first + itinerary"]
  API --> P["/api/plan · background"]
  P --> S

Three API routes, one JSON contract

We use OpenAI Chat Completions with response_format: { type: "json_object" }:

Route	When	Output
`/api/compare`	User has trip constraints	`CompareResult` — 3 cities, 1 winner
`/api/inspire`	“Surprise me” mode	Same shape, model picks candidates
`/api/plan`	After compare succeeds	`PlanResult` — book-first + days + warnings

No API key? Routes return Lisbon demo data from lib/mock-data.ts. Local dev and design review never block on keys.

Production demo cap: 3 compare/inspire calls per IP per day (TRAVEL_DEMO_DAILY_LIMIT). Plan does not double-charge the limit — it rides along after compare.

Prompts live in lib/prompts.ts. Response language follows locale (en, zh, ko, es).

UX decisions that matter

Headline voice: “I”, not “you”

Hero copy: “Where should I go — really?”

The doubt is internal. It matches “Start with my trip” and “I know where I want to go.” Advisor-voice “you” felt like marketing; first-person reads like the user’s own question.

Surprise me is optional, not default

Gold-accent tab + legal banner when inspire mode is on. Same result components — we did not fork /result. AI suggestions are labeled; user still sees a comparison table and trade-offs.

Column tap = photo preview only

On the compare table, tapping a city column swaps the hero photo. Winner copy, confidence, and book-first stay on the top pick. Users explore alternatives visually without pretending the recommendation changed.

Book-first is where affiliate lives

Monetization rule: decision quality first, affiliate after.

lib/affiliate.ts builds Skyscanner / Booking / Expedia / Viator / GetYourGuide URLs with optional partner IDs. Links only render in BookFirst on /result, with rel="sponsored nofollow". Compare prompts never mention partners.

See ADR 0004.

React 19 + Next.js 16: hydration we hit twice

Session-backed UI is convenient until SSR.

Bug class: useState(() => readSessionStorage()) — server renders defaults, client first paint reads storage → mismatch. We saw it on the sidebar “Continue your last trip” card (<div> vs <Link>).

Fix:

Stable SSR defaults (null, defaultTrip, "en", "light").
Load storage in useEffect after mount.
Gate persistence effects with a ready flag so mount does not overwrite stored values.

Theme: dropped next-themes inline <script> (React 19 warns and will not execute scripts in the component tree). Custom ThemeProvider + <html class="light"> default. Brief dark-mode flash beats console errors.

JSON-LD moved to next/script (afterInteractive) instead of raw <script> in JSX.

Full write-up: ADR 0003.

Mobile chrome

Same foundation contract as other XingAI apps:

Sticky top bar · hamburger drawer · fixed bottom nav (primary routes)
Collapsible desktop sidebar with logo mark; brand text in header
LEGAL + Help accordions pinned to bottom of mobile drawer (default closed)
Locale + theme reachable on mobile without opening the drawer

Sky-blue primary (#2563eb), oklch tokens in globals.css, hero photo with brighter dark-mode treatment.

What we deliberately did not build (V1)

User accounts or saved trips DB
Live fare scraping
Shareable /result URLs (session-only; excluded from sitemap)
Chat UI

/llms.txt, FAQ JSON-LD, and product principles doc tell crawlers and partners what we are.

Files worth reading

Path	Why
`components/decide-page.tsx`	Mode toggle, compare flow, plan prefetch
`components/destination-compare.tsx`	Winner + column preview
`components/book-first.tsx`	Affiliate boundary in UI
`lib/prompts.ts`	Structured AI contracts
`docs/adr/`	Bilingual ADRs 0001–0005
`docs/PRODUCT-PRINCIPLES.md`	Monetization rules

Next likely steps

Cookie-backed theme/locale for zero-flash SSR
KV-backed rate limits + affiliate click analytics
Saved trips (requires auth + DB — only after compare flow proves retention)
Stricter JSON schema validation on model output

Repo: xingai-travel-ai · Domain: travel.xingai.app

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