12 Cursor rules that stop AI assistants writing outdated FastAPI code

A developer published a set of 12 Cursor project rules designed to steer AI coding assistants away from outdated FastAPI patterns such as `.dict()`, `orm_mode`, `session.query()` and SQLite-based tests, replacing them with Pydantic v2, SQLAlchemy 2.0 and async conventions. The rules are scoped `.mdc` files in `.cursor/rules/` that load only for matching globs, and the same conventions can be applied to Claude Code via a repo-root `CLAUDE.md`. The author sells a $12 rules pack with seven scoped files, two of which are offered as a free download.

AI coding assistants still reach for FastAPI patterns from a few years ago: .dict , orm mode , session.query , HTTPException raised deep inside service code, SQLite in tests. The code runs, but it isn't the code you'd write today. Cursor's project rules fix most of this. A rule is a small .mdc file in .cursor/rules/ with a glob, so it loads only when you edit matching files: --- description: "FastAPI routers, dependencies and Pydantic v2 schemas" globs: src/app/ /router.py,src/app/ /schemas.py,src/app/ /deps.py alwaysApply: false --- - One APIRouter prefix="/<plural-resource " per feature ... These are the 12 conventions that made the biggest difference for me. model validate , model dump , ConfigDict , field validator . Never .dict , parse obj , orm mode , class Config or the v1 validator decorator. response model status code : 201 for create, 204 for delete. XCreate / XUpdate / XRead . ConfigDict extra="forbid" so a sneaky "is admin": true is rejected. Apply updates with model dump exclude unset=True . Mapped ... , mapped column , select . Never session.query or declarative base . async with session.begin : . Repositories never commit. Use async sessionmaker expire on commit=False . lazy="raise" . selectinload or joinedload , so there's no hidden IO in async code. MetaData naming convention=... on your Base AppError subclasses, never HTTPException . {"error": {"code": ..., "message": ...}} . get settings os.environ elsewhere, and keep secrets as SecretStr . text ... .bindparams . httpx.AsyncClient transport=ASGITransport app=app app.dependency overrides after each test. No SQLite stand-in. Drop rules like these into .cursor/rules/ , one file per area, with globs that match your layout. For Claude Code, the same conventions work as a short CLAUDE.md at the repo root. Disclosure: I made a FastAPI rules pack with these conventions written out as 7 scoped .mdc files plus a CLAUDE.md , and I sell it for $12 at codebaserules.com https://codebaserules.com . Two of the files are a free download https://codebaserules.com/packs/fastapi.html , no email needed. Everything above works without buying anything. I'd like to hear which of these you'd change.