A set of protocols support a common script object model for document interaction that crosses document types and runtime environments. A cross frame browser-based protocol may provide a secure, scalable, and asynchronous mechanism for transmitting script object model requests to document hosts and managing responses to developer code in standards-compliant browsers. A hostable runtime Application Programming Interface (API) may provide a secure, scalable, and asynchronous protocol to transmit script object model requests across process boundaries to document hosts back to developer code with minimum performance impact on the document host.