PANews reported on February 13th that, according to a Hyperliquid announcement, cross-margin functionality for the HIP-3 permissionless perpetual contract market has been enabled on the testnet. While not yet available on the mainnet, it meets the requirements for mainnet-level vulnerability rewards. HIP-3 deployers must first enable this functionality for a specific asset before users can conduct cross-margin trading. Under a unified account, all cross-margin perpetual contracts using the same collateral asset can share margin, even across multiple DEXs. Assets on different DEXs will be protected up to their maintenance margin levels to prevent automatic liquidation due to significant fluctuations in other DEXs. This "protective cross-margin" system prioritizes both solvency and user experience. Cross-margin is not designed for DEX abstractions; related interfaces should not use this functionality through DEX abstractions.