Strategy Pattern
Define a family of algorithms as interchangeable function pointers. Clients select which algorithm to use at runtime without changing calling code.
ikigai Application
LLM Provider abstraction: Each provider (OpenAI, Anthropic, Google) implements same interface:
typedef struct {
res_t (*send)(void *ctx, ik_message_t **msgs, size_t count);
res_t (*stream)(void *ctx, ik_message_t **msgs, chunk_cb cb);
} ik_llm_provider_t;
Selection: Config determines which provider vtable is used. REPL calls through interface, unaware of provider.
Testing: Inject mock provider that returns canned responses.
Future: Tool execution strategies, different database backends.