In Brief:
- On Sept. 14 Arbitrum kicked off a three-week online Buildathon, the opening phase of Open House Singapore, dangling $115K in prizes and grants until Oct. 4.
- Anyone who wins is guaranteed a seat at Founder House in Singapore on Oct. 23-25, an event with another $300K attached. Combined across the two phases: $415K, paid entirely in USDC.
- One of the three podium finishes in the Buildathon, at minimum, is earmarked for a Robinhood Chain project — the chain helps fund the program. No gaming track exists.
The online Buildathon from Arbitrum went live Sept. 14, dangling $115K in prizes and grants in front of early-stage teams for the next three weeks.
Running until Oct. 4, it serves as phase one of Open House Singapore. Anyone who places in the Buildathon locks in a seat at phase two — a three-day, in-person Founder House held in Singapore Oct. 23-25, with its own separate $300K pool on the line.
Our online Buildathon program kicks off today
Over the next 3 weeks, early-stage teams will:
> sharpen their ideas, MVPs and prototypes
> get technical, product and GTM support
> compete for $115K in prizes & spots to our in-person Founder House in Singapore
On top of that,@ArbitrumView on X ↗
Applications are open to one phase or both. Funding for the pair comes jointly from the Arbitrum Foundation and Robinhood Chain, totaling $415K and settled in USDC.
How the $115K splits
The three teams that finish highest share a $70K pool. Of those three slots, at least one is held for something built on Robinhood Chain.
Promising Products, the second category, puts $15K in play across its own top three. Its focus: teams building AI agents and novel financial primitives.
Beyond that, the Foundation has earmarked another $30K in USDC for grants, handed to winning teams on a case-by-case basis.
Winners don’t collect the money all at once. Everywhere except the Promising Products track, awards break down 50/50 — half paid upfront, half released against milestones covering technical development, product roadmap, go-to-market and user growth goals set with the Arbitrum ecosystem team.
Finance, not games
Gaming isn’t the target of either named category. The Buildathon addresses teams building novel financial applications on Arbitrum, while the frontier category names AI agents outright.
Across the three weeks, workshops run through product development, go-to-market strategy, user experience, agentic commerce, wallet infrastructure and emerging market opportunities. Rather than starting from scratch, teams show up with an idea, MVP or codebase already in hand and iterate through repeated feedback sessions.
Where the Robinhood money comes from
Back in February, alongside its testnet launch, Robinhood Chain committed $1 million to the 2026 Open House program. Those funds are spread across Buildathons in New York City, London, Singapore and Dubai.
February also saw the chain’s public testnet go live; it handled upwards of 200 million transactions ahead of the July 1 mainnet launch.
Third stop on the circuit
For the 2026 founder program, Singapore serves as the Southeast Asia hub. New York City and London preceded it, and Bengaluru has hosted as well.
Between them, those two editions pulled in 2,160 builders across online and in-person activations. Project submissions reached 177 in New York and 273 in London.
Earlier this year, Arbitrum paid out $340K in New York and $300K in London.
Every edition follows the same Founder House template. The first day tackles product-market fit, product direction and finding a wedge, with feedback coming from the Arbitrum Foundation, Offchain and ecosystem partners. Day two shifts to go-to-market strategy, positioning and distribution. The third day is live pitches, after which winners are announced.
Both phases take registrations via openhouse.arbitrum.io.
There’s a detail in the rules that’s simple to overlook. That $30K grant pool rests wholly at the Foundation’s discretion — and it reserves the right to pick nothing at all.