Methods, apparatuses and storage medium associated with execution of application code having multiple ISAs, are disclosed. In various embodiments, a runtime environment may execute application code having multiple instruction set architectures. The runtime environment may be configured to execute first code of the application code according to a first instruction set architecture, while also configured to execute second code of the application code according to a second instruction set architecture that extends the first instruction set architecture. Using gates, the runtime environment may be adapted to adapt an interaction from the first code to the second instruction set architecture and/or adapt an interaction from the second code to the first instruction set architecture and, subsequently, return to executing the application code according to the first instruction set architecture or the second instruction set architecture, respectively. Other embodiments may be disclosed or claimed.