Cross-Program Invocation (CPI)
Plain English
When one Solana program calls functions in another program, like apps working together. This allows complex interactions - a trading program might call a token program to transfer assets, creating powerful composable applications.
Technical
Mechanism enabling Solana programs to invoke instructions from other programs within the same transaction. CPI enables composability by allowing programs to interact with SPL Token, associated token accounts, and other programs. Critical for building complex applications that leverage existing program functionality while maintaining security through the runtime’s privilege model.