In Brief:
- Arbitrum’s Open House Singapore kicks off a three-week online Buildathon on Sept. 14, offering $115K in prizes and seats at an in-person Founder House in Singapore.
- The Arbitrum Foundation and Robinhood Chain are jointly funding $415K across both phases, with at least one of the top three Buildathon spots reserved for a project building on Robinhood Chain.
- The brief skews toward financial products, AI agents and new financial primitives, extending a program that paid out $340K in New York and $300K in London earlier this year.
Arbitrum opened applications for the Singapore leg of its Open House founder program, with a three-week online Buildathon running Sept. 14 to Oct. 4 and $115K in prizes attached to it.
Winners get more than cash. The top teams take seats at a three-day, in-person Founder House in Singapore roughly a month after the Buildathon closes.
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.
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How the money splits
The top three Buildathon finishers share a $70K pool. A minimum of one of those three spots is reserved for a project building on Robinhood Chain.
A separate Promising Products category carries $15K split among its top three, aimed at teams working on frontier areas like AI agents and new financial primitives. At least one spot there is also reserved for Robinhood Chain builds.
The Arbitrum Foundation has set aside another $30K in USDC as grants, awarded to winning teams case by case. Those grants aren’t guaranteed. Selection sits at the Foundation’s sole discretion and it reserves the right not to pick any projects at all.
Payouts come with strings. Except in the Promising Products track, prize amounts are split 50/50 between upfront payments and milestone-based payouts.
Across the Buildathon and the Founder House, $415K has been earmarked for Singapore.
Robinhood Chain’s stake
Robinhood Chain is co-sponsoring the prize pool. It committed $1 million to the 2026 Open House program in February, covering 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.
The chain’s public testnet went live Feb. 10 and processed 4 million transactions in its first week. Mainnet followed on July 1.
Johann Kerbrat, SVP and general manager of crypto and international at Robinhood, said at the testnet launch that it “lays the groundwork for an ecosystem that will define the future of tokenized real-world assets.”
What teams actually do
Builders develop an existing project or codebase through the online phase, with feedback sessions and technical support from ecosystem partners. Founder-focused workshops cover product development, go-to-market strategy, user experience, agentic commerce, wallet infrastructure and emerging market opportunities.
At the Founder House, the emphasis shifts to product direction, value proposition, customer discovery and go-to-market work, plus mentorship and live pitches. Founders work directly with teams from the Arbitrum Foundation, Offchain and ecosystem partners.
Judging across Open House Buildathons runs on four criteria: smart contract quality, product-market fit, innovation and creativity, and whether the project solves a real problem. Contracts need to be deployed on Arbitrum Sepolia at minimum, and on Arbitrum One if possible.
Applications run through openhouse.arbitrum.io.
The two prior editions
New York came first. Its Buildathon ran Feb. 5 to 26 and drew 512 builders from more than 40 countries. Tilt Protocol won $15,000, Fangorn took $10,000 and EquelFi got $5,000.
The NYC Founder House followed March 6 to 8, where 88 teams shipped 55 projects over three days and $340K went out across five categories. Counting both phases, 1,712 builders engaged and 177 projects were submitted.
London’s Buildathon pulled 782 builders and 278 submissions across DeFi, AI, RWAs, payments and privacy, with $85K awarded. Its Founder House ran July 10 to 12 at Encode Hub, drawing 140 selected builders out of more than 490 registrations. Sixty-four projects competed for $300,000, and four teams took the prizes. One of them, Agama, lets users earn yield on tokenized equities through automated lending and yield strategies.
Tilt Protocol’s haul went further than the Buildathon check. The team walked away with $100K in Robinhood Founder in Residence seed funding for an AI-driven management layer on tokenized real-world assets, built natively on Robinhood Chain.
