Hey Product Hunt 👋

I'm Bruno from Cumbuca. We're a Payment Institution authorized by Brazil's Central Bank, and we've been implementing Open Finance since the beginning of the ecosystem.

Here's the problem we kept running into: Brazil's Open Finance is the largest in the world, but the official documentation was built to describe what the system requires, not to teach how to build on it. Every company entering the ecosystem spends weeks on what we call "technical archaeology" — figuring out undocumented requirements, bank-specific quirks, and security details that aren't in the specs.

We partnered with Juspay, who built Open Finance integrations end-to-end in Brazil and was pivotal in the rise of UPI in India. Together, we started documenting everything we learned. What began as internal notes became a structured guide. When we realized the pain was universal, we open-sourced it. What began as internal notes became a structured guide. When we realized the pain was universal, we open-sourced it.

The Playground includes:

Implementation guides — step-by-step, organized by flow (consent, payment initiation, data access)
Live simulator — see every API call behind each step of the UX
Bank-specific quirks — the things you only learn after months of implementation
It complements the official documentation — it doesn't replace it. Think of it as the "getting started guide" that every complex technical ecosystem needs.

🔗 Documentation: juspay-2.gitbook.io/open-finance/pt
🔗 GitHub: github.com/juspay/open-finance
🔗 Simulator: juspay.io/open-finance/mobileViewContainer

We'd love to hear from you:

What's the hardest part of integrating with Open Finance for you?
If you've built on Open Finance, what surprised you most about the implementation?
For developers outside Brazil — does your country's Open Banking/Finance have good dev docs?

Open Finance Playground

Open-source dev guide for Brazil's Open Finance

Open-source dev guide for Brazil's Open Finance