Concurrency Layer 1: Language Mechanics Core Question Is this CPU-bound or I/O-bound, and what's the sharing model? Before choosing concurrency primitives: - What's the workload type? - What data needs to be shared? - What's the thread safety requirement? --- Error → Design Question | Error | Don't Just Say | Ask Instead | |-------|----------------|-------------| | E0277 Send | "Add Send bound" | Should this type cross threads? | | E0277 Sync | "Wrap in Mutex" | Is shared access really needed? | | Future not Send | "Use spawn local" | Is async the right choice? | | Deadlock | "Reorder locks"…