In Brief:
- Arbitrum’s Open House heads to Singapore with a three-week online Buildathon beginning Sept. 14, putting up $115K in prizes plus invitations to an in-person Founder House in the city.
- Both phases are being bankrolled jointly by the Arbitrum Foundation and Robinhood Chain to the tune of $415K, and at least one of the Buildathon’s three top slots is set aside for a team building on Robinhood Chain.
- Financial products, AI agents and new financial primitives dominate the brief, continuing a program that already distributed $340K in New York and $300K in London earlier this year.
Applications are now open for the Singapore stop on Arbitrum’s Open House founder program, which pairs a three-week online Buildathon running from Sept. 14 to Oct. 4 with a $115K prize pot.
Cash isn’t the only reward on offer. Roughly a month after the Buildathon wraps, the leading teams earn places at a three-day, in-person Founder House in Singapore.
Bring your boldest ideas onchain with the right support at Arbitrum's Open House.
Starting September 14th, our 3-week online Buildathon gives early-stage teams product mentorship, technical support and a shot at $115K in prizes + spots to our Founder House in Singapore.
Hear@ArbitrumView on X ↗
How the money splits
A $70K pool is divided among the three highest-placing Buildathon teams, and at minimum one of those three positions is reserved for a project built on Robinhood Chain.
Sitting alongside it is a Promising Products category worth $15K, shared by its own top three and targeted at teams exploring frontier territory such as AI agents and new financial primitives. Here too, at least one slot is held for Robinhood Chain builds.
The Arbitrum Foundation has set aside another $30K in USDC as grants, handed to winning teams on a case-by-case basis. Nothing about those grants is guaranteed: selection rests entirely with the Foundation, which reserves the right to choose no projects whatsoever.
There are conditions attached to the payouts. Outside of the Promising Products track, prize money arrives as a 50/50 split between upfront payments and milestone-based payouts.
Combined, the Buildathon and Founder House account for $415K earmarked for Singapore.
Robinhood Chain’s stake
Co-sponsoring the prize pool is Robinhood Chain, which pledged $1 million to the 2026 Open House program back in February — money spread across Buildathons in New York City, London, Singapore and Dubai.
“We’re supporting builders, globally. Robinhood Chain is supporting the Arbitrum Open House 2026 with $1 million of prizes for builders, backing teams building on the Robinhood Chain testnet, across New York, London, Singapore, and Dubai,” the company said when it announced the sponsorship.
Its public testnet launched Feb. 10 and handled 4 million transactions within the opening week, with mainnet arriving on July 1.
Speaking at the testnet launch, Johann Kerbrat, SVP and general manager of crypto and international at Robinhood, said it “lays the groundwork for an ecosystem that will define the future of tokenized real-world assets.”
What teams actually do
Throughout the online phase, participants build out an existing project or codebase while receiving feedback sessions and technical support from ecosystem partners. Workshops geared toward founders tackle product development, go-to-market strategy, user experience, agentic commerce, wallet infrastructure and emerging market opportunities.
The Founder House pivots toward product direction, value proposition, customer discovery and go-to-market work, rounded out with mentorship and live pitches. Founders collaborate hands-on with people from the Arbitrum Foundation, Offchain and ecosystem partners.
Every Open House Buildathon is judged on the same four measures: smart contract quality, product-market fit, innovation and creativity, and whether the project solves a real problem. Deployment on Arbitrum Sepolia is the baseline requirement, with Arbitrum One preferred where possible.
Applications run through openhouse.arbitrum.io.
The two prior editions
New York was the opening edition. Held Feb. 5 to 26, its Buildathon attracted 512 builders representing more than 40 countries. Tilt Protocol claimed $15,000, with Fangorn taking $10,000 and EquelFi $5,000.
From March 6 to 8, the NYC Founder House saw 88 teams ship 55 projects in three days, with $340K paid out across five categories. Tallying both phases, 1,712 builders took part and 177 projects were submitted.
In London, the Buildathon attracted 782 builders and 278 submissions spanning DeFi, AI, RWAs, payments and privacy, with $85K awarded. From July 10 to 12, its Founder House at Encode Hub hosted 140 selected builders picked from more than 490 registrations. Four teams shared the prizes as 64 projects competed for $300,000. Among the winners was Agama, which lets users earn yield on tokenized equities through automated lending and yield strategies.
For Tilt Protocol, the Buildathon check was only part of the story. The team also secured $100K in Robinhood Founder in Residence seed funding to build an AI-driven management layer for tokenized real-world assets, natively on Robinhood Chain.