✨ Add SQLModel Agent Library Skill, install with uvx library-skills (#2017)

Author: tiangolo

sqlmodel/.agents/skills/sqlmodel/SKILL.md

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+---
+name: sqlmodel
+description: Use when writing or reviewing Python code with SQLModel, especially models, sessions, queries, FastAPI integration, relationships, link models, creates, updates, and deletes.
+---
+
+# SQLModel Patterns
+
+Use SQLModel's API first. Do not default to raw SQLAlchemy patterns unless the task explicitly needs a SQLAlchemy-only feature.
+
+## Imports
+
+Prefer imports from `sqlmodel`:
+
+```python
+from sqlmodel import Field, Relationship, Session, SQLModel, create_engine, select
+```
+
+Do not use SQLAlchemy declarative defaults such as `declarative_base()`, `Mapped[...]`, `mapped_column()`, `relationship()`, or `sessionmaker()` for normal SQLModel code.
+
+## Models
+
+Define table models with `SQLModel, table=True` and `Field()`:
+
+```python
+class Hero(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    name: str = Field(index=True)
+    team_id: int | None = Field(default=None, foreign_key="team.id")
+```
+
+Use `Field(default_factory=...)` for generated values:
+
+```python
+id: uuid.UUID = Field(default_factory=uuid.uuid4, primary_key=True)
+```
+
+Use non-table `SQLModel` classes for create/update/public API schemas instead of mixing request/response-only fields into table models.
+
+## Sessions and Queries
+
+Open sessions directly with the engine:
+
+```python
+with Session(engine) as session:
+    heroes = session.exec(select(Hero)).all()
+```
+
+Do not create a `sessionmaker()` for typical SQLModel examples.
+
+Use `session.exec(select(...))`, not `session.execute(...)` and not `session.query(...)`. SQLModel's `exec()` handles scalar results so agents should not add `.scalars()` after selects of models.
+
+Use `session.get(Model, id)` for primary-key lookups.
+
+Use normal result methods after `session.exec(...)`: `.all()` for lists, `.first()` for optional first rows, `.one()` when exactly one row must exist, and `.one_or_none()` when zero or one row is valid.
+
+After creating or mutating objects, commit and refresh when returned data needs DB defaults or generated IDs:
+
+```python
+session.add(hero)
+session.commit()
+session.refresh(hero)
+```
+
+## Relationships
+
+Use SQLModel relationship attributes, not ad-hoc SQLAlchemy tables or `secondary=`.
+
+One-to-many:
+
+```python
+class Team(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    heroes: list["Hero"] = Relationship(back_populates="team")
+
+
+class Hero(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    team_id: int | None = Field(default=None, foreign_key="team.id")
+    team: Team | None = Relationship(back_populates="heroes")
+```
+
+Many-to-many:
+
+```python
+class HeroTeamLink(SQLModel, table=True):
+    team_id: int | None = Field(default=None, foreign_key="team.id", primary_key=True)
+    hero_id: int | None = Field(default=None, foreign_key="hero.id", primary_key=True)
+
+
+class Team(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    heroes: list["Hero"] = Relationship(back_populates="teams", link_model=HeroTeamLink)
+
+
+class Hero(SQLModel, table=True):
+    id: int | None = Field(default=None, primary_key=True)
+    teams: list[Team] = Relationship(back_populates="heroes", link_model=HeroTeamLink)
+```
+
+If the link table has extra fields, model it as a full SQLModel table with relationships to both sides, and interact with the link objects directly.
+
+When starting a new app, prefer keeping related SQLModel table models in one file to simplify relationship annotations and metadata ordering. If models must be split across files, use `TYPE_CHECKING` imports plus string annotations:
+
+```python
+if TYPE_CHECKING:
+    from .team_model import Team
+
+team: Optional["Team"] = Relationship(back_populates="heroes")
+```
+
+For SQLAlchemy relationship options not exposed as first-class SQLModel parameters, prefer `Relationship(sa_relationship_kwargs={...})` or `Relationship(sa_relationship_args=[...])`. Use `sa_relationship=relationship(...)` only as an escape hatch when SQLModel's relationship wrapper cannot express the mapping.
+
+## Creates and Updates
+
+Use direct construction for trusted internal values:
+
+```python
+hero = Hero(name="Deadpond", secret_name="Dive Wilson")
+```
+
+Build table objects from data models with `Model.model_validate(...)`:
+
+```python
+db_hero = Hero.model_validate(hero_create)
+```
+
+For FastAPI, use a split model pattern: `HeroBase` for shared fields, `Hero(HeroBase, table=True)` for the table, `HeroCreate` for input, `HeroUpdate` with all-optional fields for PATCH, `HeroPublic` for output, and relationship-specific public models such as `HeroPublicWithTeam` only where needed.
+
+For partial updates, dump only provided fields and update in place:
+
+```python
+hero_data = hero_update.model_dump(exclude_unset=True)
+db_hero.sqlmodel_update(hero_data)
+session.add(db_hero)
+session.commit()
+session.refresh(db_hero)
+```
+
+## Metadata and App Setup
+
+Call `SQLModel.metadata.create_all(engine)` only after all table model classes have been imported. In FastAPI examples, use a dependency that yields `Session(engine)`.
+
+For tests and small examples, SQLite is a common option; when using it, create metadata explicitly and use direct sessions:
+
+```python
+engine = create_engine("sqlite:///:memory:")
+SQLModel.metadata.create_all(engine)
+with Session(engine) as session:
+    ...
+```
+
+When using SQLite with FastAPI, include:
+
+```python
+connect_args = {"check_same_thread": False}
+engine = create_engine(sqlite_url, connect_args=connect_args)
+```
+
+## Deletes
+
+Use SQLModel's relationship helpers for cascades:
+
+```python
+heroes: list["Hero"] = Relationship(back_populates="team", cascade_delete=True)
+team_id: int | None = Field(default=None, foreign_key="team.id", ondelete="CASCADE")
+```
+
+For database-level delete behavior such as `SET NULL`, pair `ondelete` with a nullable foreign key and use `passive_deletes` on the relationship when appropriate.
+
+`ondelete="SET NULL"` requires a nullable foreign key:
+
+```python
+team_id: int | None = Field(default=None, foreign_key="team.id", ondelete="SET NULL")
+```
+
+## SQLAlchemy Escape Hatches
+
+Use SQLModel's `Field(sa_type=...)`, `Field(sa_column=...)`, `Field(sa_column_args=...)`, or `Field(sa_column_kwargs=...)` only when normal `Field()` parameters do not cover a column or type requirement. Do not switch the whole model to SQLAlchemy declarative style for one custom column.