Builder's Block #015: Apply for Open House London & New Wallet Standards on Arbitrum

📣 Announcements

Key updates from the Arbitrum ecosystem and Foundation.

Open House London: Buildathon Applications Now Open

Open House London kicks off May 25th with an online buildathon. Connect with top teams, get hands-on support, and showcase what you're building on Arbitrum. NYC saw 1,700+ builders, 177 projects, and $340K awarded across payment rails, agentic commerce, prediction markets, and tokenized assets. London is next.
➡️ Apply to Open House London

First Arbitrum Mentorship Program Applications are Now Closed

Applications for the Arbitrum Mentorship Program are now closed as of April 7th. We saw strong interest from early-stage teams looking to build on Arbitrum, and we’re excited about the cohort taking shape. Selected teams will undergo eight weeks of hands-on mentorship with industry experts, culminating in a Demo Day in front of top-tier investors.

Stay tuned - we’ll be sharing more on the final cohort soon.

Agentic Bounty Challenge Has Concluded with 30+ Applications

The ArbiLink Agentic Bounty has ended on April 3rd, and we're no longer accepting submissions. Huge thank you to everyone who built and participated - we’ve seen some really strong submissions come through!

We’ll be reviewing entries and announcing results soon. Stay tuned!
➡️ Follow us for the latest updates

📚 Learn & Build

New learning drops and hands-on resources from across the Arbitrum ecosystem.

Best Practices for Agentic Wallets with MoonPay OWS

Learn how to design secure agent wallets using the Open Wallet Standard (OWS) by MoonPay, with encrypted local vaults and a policy engine to manage permissions safely. Covers why current setups fall short and how to implement a more robust architecture for AI agents in practice.
➡️ Watch the Video

Rust Onchain: A Backend Engineer's Guide to Stylus

Learn how to move backend computation onchain with Arbitrum Stylus, using Rust to build verifiable, tamper-proof logic without changing your stack. Walks through a real scoring engine architecture, shared types across onchain/offchain, and why WASM unlocks major compute savings.
➡️ Read the Blog

🔦 Ecosystem Highlights

Fresh launches and standout threads from around the Arbitrum ecosystem.

Advanced Permissions (ERC-7715) is now live on Arbitrum

Agents and apps can now request scoped permissions from MetaMask users to execute transactions on their behalf.
➡️ Learn More Here

L1 vs L2: Choosing The Right Chain

Understand why choosing between L1 and L2 is a critical decision when building onchain, from cost and scalability to long-term architecture. Here’s why Robinhood chose to launch on Arbitrum.
➡️ Watch the Full Video

🗓️ Events

Workshops, hackathons, and ecosystem meetups to watch.

ArbiLink Highlights in EthCC Cannes

ArbiLink Cannes was incredible! 🇫🇷

So many great conversations with founders and investors on agentic DeFi, payments, tokenization and infrastructure.
➡️ Check out the Recap Video

That’s all from Builder’s Block #015. Thank you for reading, and keep building. Arbitrum Everywhere.