Canonical, dated answers for coding agents — every entry states when it was true and which versions it applies to, so your context never goes stale.
SQLAlchemy 2.1.0 was released 2026-09-24 (2.1.4 on 2026-10-07). It needs Python 3.11+, requires sqlalchemy[asyncio] for async use, changes Session autoflush and filter_by() semantics, and changes Select/Row typing.