priority: critical

Python Modern & Performance Standards

Python 3.10+ · Functional-first · msgspec · Fully async · Strongest typing

• Target Python 3.10+; match/case, union types (X | Y), structural pattern matching
• msgspec ONLY (NEVER pydantic); msgspec.Struct with slots=True, kw_only=True, frozen=True
• Full type hints: ParamSpec for decorators, TypeVar/Generic[T], Protocol for structural typing
• Enable mypy --strict --warn-unreachable --disallow-any-expr; never use Any
• Functional patterns: pure functions, composition, map/filter/reduce, immutability
• Walrus operator := in comprehensions; match/case for conditionals
• contextlib.suppress for intentional exception suppression
• O(1) optimization: dict/set lookups over if/elif chains
• Fully async: anyio.Path (not pathlib), httpx AsyncClient, asyncpg, asyncio.gather
• Function-based tests ONLY (*_test.py); pytest fixtures, 95% coverage, real PostgreSQL
• Never: class tests, pydantic, sync I/O in async, Any type, Optional[T] (use T | None)