> ## Content Index > Fetch the complete content index at: https://blog.arbitrum.foundation/llms.txt > Use this file to discover other available public pages before exploring further. # Builder's Block #015: Apply for Open House London & New Wallet Standards on Arbitrum - URL: https://blog.arbitrum.foundation/builders-block-015-apply-for-open-house-london-new-wallet-standards-on-arbitrum/ - Published: 2026-04-15T12:03:35.000Z - Updated: 2026-04-15T12:03:35.000Z - Author: Arbitrum Foundation - Tags: Builder Newsletter 💡 ****What's Important This Week** 🇬🇧 Open House London Buildathon kicks off May 25th. Apply today. 📚 Arbitrum Mentorship Program Applications Closed with 900 Submissions ⚡ ERC-7715 and Open Wallet Standard are now live on Arbitrum ## 📣 Announcements *Key updates from the Arbitrum ecosystem and Foundation.* ### Open House London: Buildathon Applications Now Open ![0426_OpenHouse_London_1920x1080.png](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/0426_OpenHouse_London_1920x1080.png) 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](https://openhouse.arbitrum.io/?utm%5Fsource=builder-block&utm%5Fmedium=newsletter&utm%5Fcampaign=oh-london-buildathon) ### 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 ![agentic_bounty.jpeg](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/agentic_bounty.jpeg) 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](https://x.com/ArbitrumDevs?ref=blog.arbitrum.foundation) --- ## 📚 Learn & Build *New learning drops and hands-on resources from across the Arbitrum ecosystem.* ### Best Practices for Agentic Wallets with MoonPay OWS [![open_wallet_standard.jpeg](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/open_wallet_standard.jpeg)](https://x.com/blockbyvlog/status/2041518606320640099?s=20&ref=blog.arbitrum.foundation) 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](https://x.com/blockbyvlog/status/2041518606320640099?s=20&ref=blog.arbitrum.foundation) ### Rust Onchain: A Backend Engineer's Guide to Stylus [![0326_Arbitrum_Blog_Stylus_BackednEngineers_1200x600.jpg](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/0326_Arbitrum_Blog_Stylus_BackednEngineers_1200x600.jpg)](https://blog.arbitrum.foundation/rust-onchain-a-backend-engineers-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](https://blog.arbitrum.foundation/rust-onchain-a-backend-engineers-guide-to-stylus/) --- ## 🔦 Ecosystem Highlights *Fresh launches and standout threads from around the Arbitrum ecosystem.* ### Advanced Permissions (ERC-7715) is now live on Arbitrum [![Metamask_Advanced_Permissions.png](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/Metamask_Advanced_Permissions.png)](https://x.com/MetaMaskDev/status/2041139203241545959?s=20&ref=blog.arbitrum.foundation) Agents and apps can now request scoped permissions from MetaMask users to execute transactions on their behalf. ➡️ [Learn More Here](https://x.com/MetaMaskDev/status/2041139203241545959?s=20&ref=blog.arbitrum.foundation) ### 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](https://youtu.be/hjg9wLxypDs?si=UuToTmuENHQlFBWj&ref=blog.arbitrum.foundation) --- ## 🗓️ Events *Workshops, hackathons, and ecosystem meetups to watch.* ### ArbiLink Highlights in EthCC Cannes [![arbilink_cannes.jpeg](https://storage.ghost.io/c/d4/cc/d4cc8040-691e-4dd2-8282-0c08d45fc5a8/content/images/2026/04/arbilink_cannes.jpeg)](https://x.com/arbitrum/status/2041603477953011925?s=20&ref=blog.arbitrum.foundation) ArbiLink Cannes was incredible! 🇫🇷 So many great conversations with founders and investors on agentic DeFi, payments, tokenization and infrastructure. ➡️ [Check out the Recap Video](https://x.com/arbitrum/status/2041603477953011925?s=20&ref=blog.arbitrum.foundation) --- That’s all from Builder’s Block #015\. Thank you for reading, and keep building. Arbitrum Everywhere.