Comment by hanez

• We default to isolates for safety and scaling.

• Zero‑copy sharing is done with fun_shared_buffer, an off‑heap, GC‑untracked, pointer‑free block that’s immutable from the VM’s point of view.

• Lifetime is managed with plain reference counting (retain/release).

• For hot paths, we also support an adoption (ownership‑transfer) pattern during message passing so the sender can drop its ref without copying.