Design Pattern Cheatsheet (English)

Python equivalents are illustrative. Example source points to Claude Code (TypeScript) or this repo’s experiments/ where the idea shows up clearly.

Pattern	One-liner	Python sketch	Example source
Async iterator / generator	Stream events asynchronously; consumer pulls the next step.	async def loop(): yield event	src/query.ts; experiments/exp_03_core_agent_loop/main.py
Immutable snapshot	Replace state with a new object each turn; no in-place mutation.	@dataclass(frozen=True) + replace()	experiments/exp_03_core_agent_loop/main.py
Strategy	Pluggable algorithms (e.g., LLM providers).	ABC + multiple implementations	experiments/shared/llm_client.py
Registry	Map names to tools or handlers.	dict[str, Callable]	src/utils/toolSearch.ts; experiments/exp_04_tool_system/main.py
Chain of responsibility	Pass a request along handlers until one accepts (e.g., permissions).	List of handle(req)	src/utils/permissions/; experiments/exp_05_permission_engine/main.py
Facade	One entrypoint over a complex subsystem.	Wrapper class	experiments/shared/llm_client.py; src/utils/model/model.ts
Adapter	Translate an external protocol to an internal interface.	Thin wrapper over a SDK	tools/MCPTool/MCPTool.ts; experiments/exp_09_mcp_client/main.py
Observer / pub-sub	Subscribers react to streamed events.	asyncio.Queue + consumers	src/utils/stream.ts; experiments/exp_12_streaming_api/main.py
State	Explicit states and transitions for loop control.	Enum + branching	experiments/exp_03_core_agent_loop/main.py
Command	Encapsulate an action for queueing or retry.	dataclass + run(ctx)	src/commands/; experiments/exp_15_command_system/main.py
Template method	Fixed skeleton; subclasses override steps.	Base run() calling _step_*	src/services/compact/compact.ts
Leader–worker / queue	Coordinator enqueues; workers dequeue.	asyncio.Queue	src/utils/swarm/; experiments/exp_10_multi_agent/main.py