Most hackathons follow the same script: show up Friday night, caffeinate through the weekend, demo something half-built on Sunday, collect swag, go home. Maybe you win a prize. Probably you never touch the code again.
The projects that actually ship rarely come from that format. They come from sustained focus, feedback loops, and access to people who've done it before.
That's the thesis behind Arbitrum Open House.
What Open House actually is
Open House is a three-phase program that runs online first, then moves to an in-person founder house for teams that are ready.
Phase 1: Online Buildathon (Feb 5-26)
Three weeks of building with structured feedback sessions and workshops. You can bring an existing project or start fresh. The goal isn't a flashy demo; it's getting from idea to working MVP with hands-on support along the way. Expect deep technical sessions on the Arbitrum stack, live coding demos, and founder-focused workshops on GTM and shipping.
Phase 2: IRL Founder House (Mar 6-8, NYC)
An application-based, in-person sprint in Manhattan. You work alongside Arbitrum engineers and ecosystem partners to push past MVP stage. Quick pitch sessions help shape your product and prepare you for early fundraising conversations.
Phase 3: Mentorship
Top teams continue working with the Arbitrum Foundation directly, with access to funding opportunities and a path to grow inside the ecosystem.
For more details on the NYC program specifically, check out this breakdown on dev.to.
Why it works
The first Open House ran in Bengaluru last fall. The winning team, Orbital AMM Protocol, built a multi-asset AMM using Stylus (Arbitrum's support for Rust/C/C++ smart contracts) with production-grade math that would've been impractical in a weekend sprint. Second place went to Shinobi.Cash, a cross-chain privacy protocol. Third was GuardChain.ai, blockchain-native insurance for gig workers.
These weren't proof-of-concepts. They were products with architecture decisions, user flows, and go-to-market plans.
The difference: time to think, people to ask, and a structure that rewards shipping over demoing.
NYC numbers
The New York program has $30K in prizes and $30K in grants. Open House as a whole is distributing up to $800K across four cities this year: NYC, London, Dubai, and Singapore.
Who should apply
If you're building on Arbitrum (or want to), have an idea worth testing, and want focused time with engineers and mentors who can actually help, this is the format.
Sign up: openhouse.arbitrum.io