sYnFi is a modern, mobile-first personal and family finance application in the sYnVerse ecosystem designed for tracking peer and family loans, generating formal promissory agreements, and managing group vacation travel expenses with automated debt simplification. Built with React Native and Expo for iOS, Android, and Web, sYnFi runs on a 100% serverless Cloudflare stack (Workers, D1 SQLite database, and Static Assets). Authentication is unified across the ecosystem through sYnID Single Sign-On.

sYnFi is developed as a private, proprietary personal finance application within the sYnVerse ecosystem, purpose-built for secure family lending, peer agreements, and collaborative travel ledgers.

Technical Stack

Core Features

• Family & Peer Loan Management — Manage loans from either perspective: “Money I’ve Lent” (Lender) or “Money I’ve Borrowed” (Borrower), with real-time principal balance tracking, payment progress rings, and remaining installment counters.
• 0% Family Courtesy Rate & Custom APR — Standard zero-interest family loan support with exact-cent penny distribution to eliminate fractional rounding errors. Also supports customizable APR amortization terms with monthly, bi-weekly, or lump-sum repayments extending up to 72 months.
• Promissory Agreement Generator — Create formal yet respectful promissory agreements tailored for family and friends. Borrowers and lenders can review terms, interest details, and payment schedules, then digitally acknowledge the agreement directly in the app.
• Immutable Payment Ledger — Record repayments via Zelle, Venmo, Bank Transfer, Cash, or Check. Includes custom transaction date pickers, notes, and real-time principal recalculation backed by an immutable audit trail.
• Vacation Trip Ledger (v2.0) — A dedicated group travel expense tracker for vacations and group outings. Create trips, invite travel companions, record split expenses across categories (Flights, Lodging, Dining, Transit, Activities, Shopping), and view real-time net balances.
• Smart Settle Debt Simplification — Built-in greedy minimal cash-flow engine that minimizes cross-debts among travelers into the smallest possible number of direct settlement transfers.
• Plaid Bank Linking (Dual-Mode) — Seamless account linking with a built-in mock sandbox engine for immediate testing without API keys, plus seamless developer tier integration for linking real institutions with masked account numbers and encrypted tokens.
• Glassmorphic Multi-Module Navigation — Universal floating glassmorphic tab bar with haptic feedback, dark obsidian and warm cream light themes, and an interactive Dashboard module switcher pill ([ 🤝 Family Loans | ✈️ Vacation Trips ]).
• Over-The-Air (OTA) Updates — Native mobile improvements and fixes deploy over-the-air through expo-updates. The EAS workflow computes native runtime fingerprints, automatically deploying OTA updates for JavaScript changes and building preview APKs only when native binary dependencies change.
• Single Sign-On (sYnID) — Seamless authentication powered by sYnID OpenAuth with PKCE S256, strict audience (aud) validation to prevent cross-app token reuse, and hardware-backed credential storage via iOS Keychain and Android Keystore.
• Automated E2E Testing — Comprehensive Playwright automated test suite verifying critical loan calculation workflows, trip ledger splits, and responsive viewports across desktop and mobile.

What’s Next

Upcoming roadmap enhancements include automated push reminders for scheduled loan installments, recurring trip expense templates, exportable PDF promissory agreements and tax documentation, and enhanced multi-currency support for international travel.