Open Transaction Layer, or OTL, is being developed as a unified transaction coordination protocol for onchain finance, with participants including Robinhood, MetaMask, eToro, Fireblocks, Checkout.com, Cross River Bank, Securitize, Wintermute, TON, Solana, Stellar and Polygon. The initiative aims to provide an open protocol stack that coordinates identity, compliance, transaction messaging and execution across wallets, institutions and AI agents. This expands the previously reported participant list and further positions OTL as infrastructure intended to improve interoperability and reduce operational complexity in digital finance.