Version 2.0.0

* refactor: remove deprecated parameter and function

* refactor: centralize type aliases in types.py and simplify crud layer

* test: add missing tests for fixtures/utils.py

* refactor: simplify and deduplicate across crud, metrics, cli, and
exceptions

* docs: fix old Paginate references

* docs: add migration + fix icon

* docs: update README/migration to v2

README.md

@@ -20,7 +20,7 @@ A modular collection of production-ready utilities for FastAPI. Install only wha
 
 ## Installation
 
-The base package includes the core modules (CRUD, database, schemas, exceptions, fixtures, dependencies, logging):
+The base package includes the core modules (CRUD, database, schemas, exceptions, fixtures, dependencies, model mixins, logging):
 
 ```bash
 uv add fastapi-toolsets
@@ -29,9 +29,9 @@ uv add fastapi-toolsets
 Install only the extras you need:
 
 ```bash
-uv add "fastapi-toolsets[cli]"      # CLI (typer)
+uv add "fastapi-toolsets[cli]"
-uv add "fastapi-toolsets[metrics]"  # Prometheus metrics (prometheus_client)
+uv add "fastapi-toolsets[metrics]"
-uv add "fastapi-toolsets[pytest]"   # Pytest helpers (httpx, pytest-xdist)
+uv add "fastapi-toolsets[pytest]"
 ```
 
 Or install everything:
@@ -48,6 +48,7 @@ uv add "fastapi-toolsets[all]"
 - **Database**: Session management, transaction helpers, table locking, and polling-based row change detection
 - **Dependencies**: FastAPI dependency factories (`PathDependency`, `BodyDependency`) for automatic DB lookups from path or body parameters
 - **Fixtures**: Fixture system with dependency management, context support, and pytest integration
+- **Model Mixins**: SQLAlchemy mixins for common column patterns (`UUIDMixin`, `CreatedAtMixin`, `UpdatedAtMixin`, `TimestampMixin`)
 - **Standardized API Responses**: Consistent response format with `Response`, `PaginatedResponse`, and `PydanticBase`
 - **Exception Handling**: Structured error responses with automatic OpenAPI documentation
 - **Logging**: Logging configuration with uvicorn integration via `configure_logging` and `get_logger`

docs/index.md

@@ -20,7 +20,7 @@ A modular collection of production-ready utilities for FastAPI. Install only wha
 
 ## Installation
 
-The base package includes the core modules (CRUD, database, schemas, exceptions, fixtures, dependencies, logging):
+The base package includes the core modules (CRUD, database, schemas, exceptions, fixtures, dependencies, model mixins, logging):
 
 ```bash
 uv add fastapi-toolsets
@@ -29,9 +29,9 @@ uv add fastapi-toolsets
 Install only the extras you need:
 
 ```bash
-uv add "fastapi-toolsets[cli]"      # CLI (typer)
+uv add "fastapi-toolsets[cli]"
-uv add "fastapi-toolsets[metrics]"  # Prometheus metrics (prometheus_client)
+uv add "fastapi-toolsets[metrics]"
-uv add "fastapi-toolsets[pytest]"   # Pytest helpers (httpx, pytest-xdist)
+uv add "fastapi-toolsets[pytest]"
 ```
 
 Or install everything:
@@ -44,10 +44,11 @@ uv add "fastapi-toolsets[all]"
 
 ### Core
 
-- **CRUD**: Generic async CRUD operations with `CrudFactory`, built-in full-text/faceted search and offset/cursor pagination.
+- **CRUD**: Generic async CRUD operations with `CrudFactory`, built-in full-text/faceted search and Offset/Cursor pagination.
 - **Database**: Session management, transaction helpers, table locking, and polling-based row change detection
 - **Dependencies**: FastAPI dependency factories (`PathDependency`, `BodyDependency`) for automatic DB lookups from path or body parameters
 - **Fixtures**: Fixture system with dependency management, context support, and pytest integration
+- **Model Mixins**: SQLAlchemy mixins for common column patterns (`UUIDMixin`, `CreatedAtMixin`, `UpdatedAtMixin`, `TimestampMixin`)
 - **Standardized API Responses**: Consistent response format with `Response`, `PaginatedResponse`, and `PydanticBase`
 - **Exception Handling**: Structured error responses with automatic OpenAPI documentation
 - **Logging**: Logging configuration with uvicorn integration via `configure_logging` and `get_logger`

docs/migration/v2.md

@@ -0,0 +1,137 @@
+# Migrating to v2.0
+
+This page covers every breaking change introduced in **v2.0** and the steps required to update your code.
+
+---
+
+## CRUD
+
+### `schema` is now required in `offset_paginate()` and `cursor_paginate()`
+
+Calls that omit `schema` will now raise a `TypeError` at runtime.
+
+Previously `schema` was optional; omitting it returned raw SQLAlchemy model instances inside the response. It is now a required keyword argument and the response always contains serialized schema instances.
+
+=== "Before (`v1`)"
+
+    ```python
+    # schema omitted — returned raw model instances
+    result = await UserCrud.offset_paginate(session=session, page=1)
+    result = await UserCrud.cursor_paginate(session=session, cursor=token)
+    ```
+
+=== "Now (`v2`)"
+
+    ```python
+    result = await UserCrud.offset_paginate(session=session, page=1, schema=UserRead)
+    result = await UserCrud.cursor_paginate(session=session, cursor=token, schema=UserRead)
+    ```
+
+### `as_response` removed from `create()`, `get()`, and `update()`
+
+Passing `as_response` to these methods will raise a `TypeError` at runtime.
+
+The `as_response=True` shorthand is replaced by passing a `schema` directly. The return value is a `Response[schema]` when `schema` is provided, or the raw model instance when it is not.
+
+=== "Before (`v1`)"
+
+    ```python
+    user = await UserCrud.create(session=session, obj=data, as_response=True)
+    user = await UserCrud.get(session=session, filters=filters, as_response=True)
+    user = await UserCrud.update(session=session, obj=data, filters, as_response=True)
+    ```
+
+=== "Now (`v2`)"
+
+    ```python
+    user = await UserCrud.create(session=session, obj=data, schema=UserRead)
+    user = await UserCrud.get(session=session, filters=filters, schema=UserRead)
+    user = await UserCrud.update(session=session, obj=data, filters, schema=UserRead)
+    ```
+
+### `delete()`: `as_response` renamed and return type changed
+
+`as_response` is gone, and the plain (non-response) call no longer returns `True`.
+
+Two changes were made to `delete()`:
+
+1. The `as_response` parameter is renamed to `return_response`.
+2. When called without `return_response=True`, the method now returns `None` on success instead of `True`.
+
+=== "Before (`v1`)"
+
+    ```python
+    ok = await UserCrud.delete(session=session, filters=filters)
+    if ok:  # True on success
+        ...
+
+    response = await UserCrud.delete(session=session, filters=filters, as_response=True)
+    ```
+
+=== "Now (`v2`)"
+
+    ```python
+    await UserCrud.delete(session=session, filters=filters)  # returns None
+
+    response = await UserCrud.delete(session=session, filters=filters, return_response=True)
+    ```
+
+### `paginate()` alias removed
+
+Any call to `crud.paginate(...)` will raise `AttributeError` at runtime.
+
+The `paginate` shorthand was an alias for `offset_paginate`. It has been removed; call `offset_paginate` directly.
+
+=== "Before (`v1`)"
+
+    ```python
+    result = await UserCrud.paginate(session=session, page=2, items_per_page=20, schema=UserRead)
+    ```
+
+=== "Now (`v2`)"
+
+    ```python
+    result = await UserCrud.offset_paginate(session=session, page=2, items_per_page=20, schema=UserRead)
+    ```
+
+---
+
+## Exceptions
+
+### Missing `api_error` raises `TypeError` at class definition time
+
+Unfinished or stub exception subclasses that previously compiled fine will now fail on import.
+
+In `v1`, a subclass without `api_error` would only fail when the exception was raised. In `v2`, `__init_subclass__` validates this at class definition time.
+
+=== "Before (`v1`)"
+
+    ```python
+    class MyError(ApiException):
+        pass  # fine until raised
+    ```
+
+=== "Now (`v2`)"
+
+    ```python
+    class MyError(ApiException):
+        pass  # TypeError: MyError must define an 'api_error' class attribute.
+    ```
+
+For shared base classes that are not meant to be raised directly, use `abstract=True`:
+
+```python
+class BillingError(ApiException, abstract=True):
+    """Base for all billing-related errors — not raised directly."""
+
+class PaymentRequiredError(BillingError):
+    api_error = ApiError(code=402, msg="Payment Required", desc="...", err_code="BILLING-402")
+```
+
+---
+
+## Schemas
+
+### `Pagination` alias removed
+
+`Pagination` was already deprecated in `v1` and is fully removed in `v2`, you now need to use [`OffsetPagination`](../reference/schemas.md#fastapi_toolsets.schemas.OffsetPagination) or [`CursorPagination`](../reference/schemas.md#fastapi_toolsets.schemas.CursorPagination).

docs/module/exceptions.md

@@ -21,30 +21,37 @@ init_exceptions_handlers(app=app)
 This registers handlers for:
 
 - [`ApiException`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.ApiException) — all custom exceptions below
+- `HTTPException` — Starlette/FastAPI HTTP errors
 - `RequestValidationError` — Pydantic request validation (422)
 - `ResponseValidationError` — Pydantic response validation (422)
 - `Exception` — unhandled errors (500)
 
+It also patches `app.openapi()` to replace the default Pydantic 422 schema with a structured example matching the `ErrorResponse` format.
+
 ## Built-in exceptions
 
 | Exception | Status | Default message |
 |-----------|--------|-----------------|
 | [`UnauthorizedError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.UnauthorizedError) | 401 | Unauthorized |
 | [`ForbiddenError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.ForbiddenError) | 403 | Forbidden |
-| [`NotFoundError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.NotFoundError) | 404 | Not found |
+| [`NotFoundError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.NotFoundError) | 404 | Not Found |
 | [`ConflictError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.ConflictError) | 409 | Conflict |
-| [`NoSearchableFieldsError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.NoSearchableFieldsError) | 400 | No searchable fields |
+| [`NoSearchableFieldsError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.NoSearchableFieldsError) | 400 | No Searchable Fields |
-| [`InvalidFacetFilterError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidFacetFilterError) | 400 | Invalid facet filter |
+| [`InvalidFacetFilterError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidFacetFilterError) | 400 | Invalid Facet Filter |
+| [`InvalidOrderFieldError`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.InvalidOrderFieldError) | 422 | Invalid Order Field |
+
+### Per-instance overrides
+
+All built-in exceptions accept optional keyword arguments to customise the response for a specific raise site without changing the class defaults:
+
+| Argument | Effect |
+|----------|--------|
+| `detail` | Overrides both `str(exc)` (log output) and the `message` field in the response body |
+| `desc` | Overrides the `description` field |
+| `data` | Overrides the `data` field |
 
 ```python
-from fastapi_toolsets.exceptions import NotFoundError
+raise NotFoundError(detail="User 42 not found", desc="No user with that ID exists in the database.")
-
-@router.get("/users/{id}")
-async def get_user(id: int, session: AsyncSession = Depends(get_db)):
-    user = await UserCrud.first(session=session, filters=[User.id == id])
-    if not user:
-        raise NotFoundError
-    return user
 ```
 
 ## Custom exceptions
@@ -58,12 +65,51 @@ from fastapi_toolsets.schemas import ApiError
 class PaymentRequiredError(ApiException):
     api_error = ApiError(
         code=402,
-        msg="Payment required",
+        msg="Payment Required",
         desc="Your subscription has expired.",
-        err_code="PAYMENT_REQUIRED",
+        err_code="BILLING-402",
     )
 ```
 
+!!! warning
+    Subclasses that do not define `api_error` raise a `TypeError` at **class creation time**, not at raise time.
+
+### Custom `__init__`
+
+Override `__init__` to compute `detail`, `desc`, or `data` dynamically, then delegate to `super().__init__()`:
+
+```python
+class OrderValidationError(ApiException):
+    api_error = ApiError(
+        code=422,
+        msg="Order Validation Failed",
+        desc="One or more order fields are invalid.",
+        err_code="ORDER-422",
+    )
+
+    def __init__(self, *field_errors: str) -> None:
+        super().__init__(
+            f"{len(field_errors)} validation error(s)",
+            desc=", ".join(field_errors),
+            data={"errors": [{"message": e} for e in field_errors]},
+        )
+```
+
+### Intermediate base classes
+
+Use `abstract=True` when creating a shared base that is not meant to be raised directly:
+
+```python
+class BillingError(ApiException, abstract=True):
+    """Base for all billing-related errors."""
+
+class PaymentRequiredError(BillingError):
+    api_error = ApiError(code=402, msg="Payment Required", desc="...", err_code="BILLING-402")
+
+class SubscriptionExpiredError(BillingError):
+    api_error = ApiError(code=402, msg="Subscription Expired", desc="...", err_code="BILLING-402-EXP")
+```
+
 ## OpenAPI response documentation
 
 Use [`generate_error_responses`](../reference/exceptions.md#fastapi_toolsets.exceptions.exceptions.generate_error_responses) to add error schemas to your endpoint's OpenAPI spec:
@@ -78,8 +124,7 @@ from fastapi_toolsets.exceptions import generate_error_responses, NotFoundError,
 async def get_user(...): ...
 ```
 
-!!! info
+Multiple exceptions sharing the same HTTP status code are grouped under one entry, each appearing as a named example keyed by its `err_code`. This keeps the OpenAPI UI readable when several error variants map to the same status.
-    The pydantic validation error is automatically added by FastAPI.
 
 ---
 

docs/module/models.md

@@ -0,0 +1,113 @@
+# Models
+
+!!! info "Added in `v2.0`"
+
+Reusable SQLAlchemy 2.0 mixins for common column patterns, designed to be composed freely on any `DeclarativeBase` model.
+
+## Overview
+
+The `models` module provides mixins that each add a single, well-defined column behaviour. They work with standard SQLAlchemy 2.0 declarative syntax and are fully compatible with `AsyncSession`.
+
+```python
+from fastapi_toolsets.models import UUIDMixin, TimestampMixin
+
+class Article(Base, UUIDMixin, TimestampMixin):
+    __tablename__ = "articles"
+
+    title: Mapped[str]
+    content: Mapped[str]
+```
+
+All timestamp columns are timezone-aware (`TIMESTAMPTZ`). All defaults are server-side, so they are also applied when inserting rows via raw SQL outside the ORM.
+
+## Mixins
+
+### [`UUIDMixin`](../reference/models.md#fastapi_toolsets.models.UUIDMixin)
+
+Adds a `id: UUID` primary key generated server-side by PostgreSQL using `gen_random_uuid()` (requires PostgreSQL 13+). The value is retrieved via `RETURNING` after insert, so it is available on the Python object immediately after `flush()`.
+
+```python
+from fastapi_toolsets.models import UUIDMixin
+
+class User(Base, UUIDMixin):
+    __tablename__ = "users"
+
+    username: Mapped[str]
+
+# id is None before flush
+user = User(username="alice")
+await session.flush()
+print(user.id)  # UUID('...')
+```
+
+### [`CreatedAtMixin`](../reference/models.md#fastapi_toolsets.models.CreatedAtMixin)
+
+Adds a `created_at: datetime` column set to `NOW()` on insert. The column has no `onupdate` hook — it is intentionally immutable after the row is created.
+
+```python
+from fastapi_toolsets.models import UUIDMixin, CreatedAtMixin
+
+class Order(Base, UUIDMixin, CreatedAtMixin):
+    __tablename__ = "orders"
+
+    total: Mapped[float]
+```
+
+### [`UpdatedAtMixin`](../reference/models.md#fastapi_toolsets.models.UpdatedAtMixin)
+
+Adds an `updated_at: datetime` column set to `NOW()` on insert and automatically updated to `NOW()` on every ORM-level update (via SQLAlchemy's `onupdate` hook).
+
+```python
+from fastapi_toolsets.models import UUIDMixin, UpdatedAtMixin
+
+class Post(Base, UUIDMixin, UpdatedAtMixin):
+    __tablename__ = "posts"
+
+    title: Mapped[str]
+
+post = Post(title="Hello")
+await session.flush()
+await session.refresh(post)
+
+post.title = "Hello World"
+await session.flush()
+await session.refresh(post)
+print(post.updated_at)
+```
+
+!!! note
+    `updated_at` is updated by SQLAlchemy at ORM flush time. If you update rows via raw SQL (e.g. `UPDATE posts SET ...`), the column will **not** be updated automatically — use a database trigger if you need that guarantee.
+
+### [`TimestampMixin`](../reference/models.md#fastapi_toolsets.models.TimestampMixin)
+
+Convenience mixin that combines [`CreatedAtMixin`](../reference/models.md#fastapi_toolsets.models.CreatedAtMixin) and [`UpdatedAtMixin`](../reference/models.md#fastapi_toolsets.models.UpdatedAtMixin). Equivalent to inheriting both.
+
+```python
+from fastapi_toolsets.models import UUIDMixin, TimestampMixin
+
+class Article(Base, UUIDMixin, TimestampMixin):
+    __tablename__ = "articles"
+
+    title: Mapped[str]
+```
+
+## Composing mixins
+
+All mixins can be combined in any order. The only constraint is that exactly one primary key must be defined — either via `UUIDMixin` or directly on the model.
+
+```python
+from fastapi_toolsets.models import UUIDMixin, TimestampMixin
+
+class Event(Base, UUIDMixin, TimestampMixin):
+    __tablename__ = "events"
+    name: Mapped[str]
+
+class Counter(Base, UpdatedAtMixin):
+    __tablename__ = "counters"
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    value: Mapped[int]
+```
+
+---
+
+[:material-api: API Reference](../reference/models.md)

docs/module/schemas.md

@@ -22,16 +22,20 @@ async def get_user(user: User = UserDep) -> Response[UserSchema]:
 
 ### [`PaginatedResponse[T]`](../reference/schemas.md#fastapi_toolsets.schemas.PaginatedResponse)
 
-Wraps a list of items with pagination metadata and optional facet values.
+Wraps a list of items with pagination metadata and optional facet values. The `pagination` field accepts either [`OffsetPagination`](../reference/schemas.md#fastapi_toolsets.schemas.OffsetPagination) or [`CursorPagination`](../reference/schemas.md#fastapi_toolsets.schemas.CursorPagination) depending on the strategy used.
+
+#### [`OffsetPagination`](../reference/schemas.md#fastapi_toolsets.schemas.OffsetPagination)
+
+Page-number based. Requires `total_count` so clients can compute the total number of pages.
 
 ```python
-from fastapi_toolsets.schemas import PaginatedResponse, Pagination
+from fastapi_toolsets.schemas import PaginatedResponse, OffsetPagination
 
 @router.get("/users")
 async def list_users() -> PaginatedResponse[UserSchema]:
     return PaginatedResponse(
         data=users,
-        pagination=Pagination(
+        pagination=OffsetPagination(
             total_count=100,
             items_per_page=10,
             page=1,
@@ -40,6 +44,26 @@ async def list_users() -> PaginatedResponse[UserSchema]:
     )
 ```
 
+#### [`CursorPagination`](../reference/schemas.md#fastapi_toolsets.schemas.CursorPagination)
+
+Cursor based. Efficient for large or frequently updated datasets where offset pagination is impractical. Provides opaque `next_cursor` / `prev_cursor` tokens; no total count is exposed.
+
+```python
+from fastapi_toolsets.schemas import PaginatedResponse, CursorPagination
+
+@router.get("/events")
+async def list_events() -> PaginatedResponse[EventSchema]:
+    return PaginatedResponse(
+        data=events,
+        pagination=CursorPagination(
+            next_cursor="eyJpZCI6IDQyfQ==",
+            prev_cursor=None,
+            items_per_page=20,
+            has_more=True,
+        ),
+    )
+```
+
 The optional `filter_attributes` field is populated when `facet_fields` are configured on the CRUD class (see [Filter attributes](crud.md#filter-attributes-facets)). It is `None` by default and can be hidden from API responses with `response_model_exclude_none=True`.
 
 ### [`ErrorResponse`](../reference/schemas.md#fastapi_toolsets.schemas.ErrorResponse)

docs/reference/models.md

@@ -0,0 +1,22 @@
+# `models`
+
+Here's the reference for the SQLAlchemy model mixins provided by the `models` module.
+
+You can import them directly from `fastapi_toolsets.models`:
+
+```python
+from fastapi_toolsets.models import (
+    UUIDMixin,
+    CreatedAtMixin,
+    UpdatedAtMixin,
+    TimestampMixin,
+)
+```
+
+## ::: fastapi_toolsets.models.UUIDMixin
+
+## ::: fastapi_toolsets.models.CreatedAtMixin
+
+## ::: fastapi_toolsets.models.UpdatedAtMixin
+
+## ::: fastapi_toolsets.models.TimestampMixin

docs/reference/schemas.md

@@ -1,4 +1,4 @@
-# `schemas` module
+# `schemas`
 
 Here's the reference for all response models and types provided by the `schemas` module.
 
@@ -12,7 +12,8 @@ from fastapi_toolsets.schemas import (
     BaseResponse,
     Response,
     ErrorResponse,
-    Pagination,
+    OffsetPagination,
+    CursorPagination,
     PaginatedResponse,
 )
 ```
@@ -29,6 +30,8 @@ from fastapi_toolsets.schemas import (
 
 ## ::: fastapi_toolsets.schemas.ErrorResponse
 
-## ::: fastapi_toolsets.schemas.Pagination
+## ::: fastapi_toolsets.schemas.OffsetPagination
+
+## ::: fastapi_toolsets.schemas.CursorPagination
 
 ## ::: fastapi_toolsets.schemas.PaginatedResponse

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "fastapi-toolsets"
-version = "1.3.0"
+version = "2.0.0"
 description = "Production-ready utilities for FastAPI applications"
 readme = "README.md"
 license = "MIT"

src/fastapi_toolsets/__init__.py

@@ -21,4 +21,4 @@ Example usage:
         return Response(data={"user": user.username}, message="Success")
 """
 
-__version__ = "1.3.0"
+__version__ = "2.0.0"

src/fastapi_toolsets/crud/__init__.py

@@ -1,7 +1,13 @@
 """Generic async CRUD operations for SQLAlchemy models."""
 
 from ..exceptions import InvalidFacetFilterError, NoSearchableFieldsError
-from ..types import FacetFieldType, JoinType, M2MFieldType, OrderByClause
+from ..types import (
+    FacetFieldType,
+    JoinType,
+    M2MFieldType,
+    OrderByClause,
+    SearchFieldType,
+)
 from .factory import CrudFactory
 from .search import SearchConfig, get_searchable_fields
 
@@ -15,4 +21,5 @@ __all__ = [
     "NoSearchableFieldsError",
     "OrderByClause",
     "SearchConfig",
+    "SearchFieldType",
 ]

src/fastapi_toolsets/db.py

@@ -10,6 +10,8 @@ from sqlalchemy import text
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
 from sqlalchemy.orm import DeclarativeBase
 
+from .exceptions import NotFoundError
+
 __all__ = [
     "LockMode",
     "create_db_context",
@@ -216,7 +218,7 @@ async def wait_for_row_change(
         The refreshed model instance with updated values
 
     Raises:
-        LookupError: If the row does not exist or is deleted during polling
+        NotFoundError: If the row does not exist or is deleted during polling
         TimeoutError: If timeout expires before a change is detected
 
     Example:
@@ -237,7 +239,7 @@ async def wait_for_row_change(
     """
     instance = await session.get(model, pk_value)
     if instance is None:
-        raise LookupError(f"{model.__name__} with pk={pk_value!r} not found")
+        raise NotFoundError(f"{model.__name__} with pk={pk_value!r} not found")
 
     if columns is not None:
         watch_cols = columns
@@ -261,7 +263,7 @@ async def wait_for_row_change(
         instance = await session.get(model, pk_value)
 
         if instance is None:
-            raise LookupError(f"{model.__name__} with pk={pk_value!r} was deleted")
+            raise NotFoundError(f"{model.__name__} with pk={pk_value!r} was deleted")
 
         current = {col: getattr(instance, col) for col in watch_cols}
         if current != initial:

src/fastapi_toolsets/exceptions/exceptions.py

@@ -6,32 +6,46 @@ from ..schemas import ApiError, ErrorResponse, ResponseStatus
 
 
 class ApiException(Exception):
-    """Base exception for API errors with structured response.
+    """Base exception for API errors with structured response."""
-
-    Subclass this to create custom API exceptions with consistent error format.
-    The exception handler will use api_error to generate the response.
-
-    Example:
-        ```python
-        class CustomError(ApiException):
-            api_error = ApiError(
-                code=400,
-                msg="Bad Request",
-                desc="The request was invalid.",
-                err_code="CUSTOM-400",
-            )
-        ```
-    """
 
     api_error: ClassVar[ApiError]
 
-    def __init__(self, detail: str | None = None):
+    def __init_subclass__(cls, abstract: bool = False, **kwargs: Any) -> None:
+        super().__init_subclass__(**kwargs)
+        if not abstract and not hasattr(cls, "api_error"):
+            raise TypeError(
+                f"{cls.__name__} must define an 'api_error' class attribute. "
+                "Pass abstract=True when creating intermediate base classes."
+            )
+
+    def __init__(
+        self,
+        detail: str | None = None,
+        *,
+        desc: str | None = None,
+        data: Any = None,
+    ) -> None:
         """Initialize the exception.
 
         Args:
-            detail: Optional override for the error message
+            detail: Optional human-readable message
+            desc: Optional per-instance override for the ``description`` field
+                in the HTTP response body.
+            data: Optional per-instance override for the ``data`` field in the
+                HTTP response body.
         """
-        super().__init__(detail or self.api_error.msg)
+        updates: dict[str, Any] = {}
+        if detail is not None:
+            updates["msg"] = detail
+        if desc is not None:
+            updates["desc"] = desc
+        if data is not None:
+            updates["data"] = data
+        if updates:
+            object.__setattr__(
+                self, "api_error", self.__class__.api_error.model_copy(update=updates)
+            )
+        super().__init__(self.api_error.msg)
 
 
 class UnauthorizedError(ApiException):
@@ -92,14 +106,15 @@ class NoSearchableFieldsError(ApiException):
         """Initialize the exception.
 
         Args:
-            model: The SQLAlchemy model class that has no searchable fields
+            model: The model class that has no searchable fields configured.
         """
         self.model = model
-        detail = (
+        super().__init__(
+            desc=(
                 f"No searchable fields found for model '{model.__name__}'. "
                 "Provide 'search_fields' parameter or set 'searchable_fields' on the CRUD class."
             )
-        super().__init__(detail)
+        )
 
 
 class InvalidFacetFilterError(ApiException):
@@ -116,16 +131,17 @@ class InvalidFacetFilterError(ApiException):
         """Initialize the exception.
 
         Args:
-            key: The unknown filter key provided by the caller
+            key: The unknown filter key provided by the caller.
-            valid_keys: Set of valid keys derived from the declared facet_fields
+            valid_keys: Set of valid keys derived from the declared facet_fields.
         """
         self.key = key
         self.valid_keys = valid_keys
-        detail = (
+        super().__init__(
+            desc=(
                 f"'{key}' is not a declared facet field. "
                 f"Valid keys: {sorted(valid_keys) or 'none — set facet_fields on the CRUD class'}."
             )
-        super().__init__(detail)
+        )
 
 
 class InvalidOrderFieldError(ApiException):
@@ -142,15 +158,14 @@ class InvalidOrderFieldError(ApiException):
         """Initialize the exception.
 
         Args:
-            field: The unknown order field provided by the caller
+            field: The unknown order field provided by the caller.
-            valid_fields: List of valid field names
+            valid_fields: List of valid field names.
         """
         self.field = field
         self.valid_fields = valid_fields
-        detail = (
+        super().__init__(
-            f"'{field}' is not an allowed order field. Valid fields: {valid_fields}."
+            desc=f"'{field}' is not an allowed order field. Valid fields: {valid_fields}."
         )
-        super().__init__(detail)
 
 
 def generate_error_responses(
@@ -158,44 +173,39 @@ def generate_error_responses(
 ) -> dict[int | str, dict[str, Any]]:
     """Generate OpenAPI response documentation for exceptions.
 
-    Use this to document possible error responses for an endpoint.
-
     Args:
-        *errors: Exception classes that inherit from ApiException
+        *errors: Exception classes that inherit from ApiException.
 
     Returns:
-        Dict suitable for FastAPI's responses parameter
+        Dict suitable for FastAPI's ``responses`` parameter.
-
-    Example:
-        ```python
-        from fastapi_toolsets.exceptions import generate_error_responses, UnauthorizedError, ForbiddenError
-
-        @app.get(
-            "/admin",
-            responses=generate_error_responses(UnauthorizedError, ForbiddenError)
-        )
-        async def admin_endpoint():
-            ...
-        ```
     """
     responses: dict[int | str, dict[str, Any]] = {}
 
     for error in errors:
         api_error = error.api_error
+        code = api_error.code
 
-        responses[api_error.code] = {
+        if code not in responses:
+            responses[code] = {
                 "model": ErrorResponse,
                 "description": api_error.msg,
                 "content": {
                     "application/json": {
-                    "example": {
+                        "examples": {},
+                    }
+                },
+            }
+
+        responses[code]["content"]["application/json"]["examples"][
+            api_error.err_code
+        ] = {
+            "summary": api_error.msg,
+            "value": {
                 "data": api_error.data,
                 "status": ResponseStatus.FAIL.value,
                 "message": api_error.msg,
                 "description": api_error.desc,
                 "error_code": api_error.err_code,
-                    }
-                }
             },
         }
 

src/fastapi_toolsets/exceptions/handler.py

@@ -1,10 +1,14 @@
 """Exception handlers for FastAPI applications."""
 
+from collections.abc import Callable
 from typing import Any
 
 from fastapi import FastAPI, Request, Response, status
-from fastapi.exceptions import RequestValidationError, ResponseValidationError
+from fastapi.exceptions import (
-from fastapi.openapi.utils import get_openapi
+    HTTPException,
+    RequestValidationError,
+    ResponseValidationError,
+)
 from fastapi.responses import JSONResponse
 
 from ..schemas import ErrorResponse, ResponseStatus
@@ -18,43 +22,20 @@ _VALIDATION_LOCATION_PARAMS: frozenset[str] = frozenset(
 def init_exceptions_handlers(app: FastAPI) -> FastAPI:
     """Register exception handlers and custom OpenAPI schema on a FastAPI app.
 
-    Installs handlers for :class:`ApiException`, validation errors, and
-    unhandled exceptions, and replaces the default 422 schema with a
-    consistent error format.
-
     Args:
-        app: FastAPI application instance
+        app: FastAPI application instance.
 
     Returns:
-        The same FastAPI instance (for chaining)
+        The same FastAPI instance (for chaining).
-
-    Example:
-        ```python
-        from fastapi import FastAPI
-        from fastapi_toolsets.exceptions import init_exceptions_handlers
-
-        app = FastAPI()
-        init_exceptions_handlers(app)
-        ```
     """
     _register_exception_handlers(app)
-    app.openapi = lambda: _custom_openapi(app)  # type: ignore[method-assign]
+    _original_openapi = app.openapi
+    app.openapi = lambda: _patched_openapi(app, _original_openapi)  # type: ignore[method-assign]
     return app
 
 
 def _register_exception_handlers(app: FastAPI) -> None:
-    """Register all exception handlers on a FastAPI application.
+    """Register all exception handlers on a FastAPI application."""
-
-    Args:
-        app: FastAPI application instance
-
-    Example:
-        from fastapi import FastAPI
-        from fastapi_toolsets.exceptions import init_exceptions_handlers
-
-        app = FastAPI()
-        init_exceptions_handlers(app)
-    """
 
     @app.exception_handler(ApiException)
     async def api_exception_handler(request: Request, exc: ApiException) -> Response:
@@ -66,12 +47,25 @@ def _register_exception_handlers(app: FastAPI) -> None:
             description=api_error.desc,
             error_code=api_error.err_code,
         )
-
         return JSONResponse(
             status_code=api_error.code,
             content=error_response.model_dump(),
         )
 
+    @app.exception_handler(HTTPException)
+    async def http_exception_handler(request: Request, exc: HTTPException) -> Response:
+        """Handle Starlette/FastAPI HTTPException with a consistent error format."""
+        detail = exc.detail if isinstance(exc.detail, str) else "HTTP Error"
+        error_response = ErrorResponse(
+            message=detail,
+            error_code=f"HTTP-{exc.status_code}",
+        )
+        return JSONResponse(
+            status_code=exc.status_code,
+            content=error_response.model_dump(),
+            headers=getattr(exc, "headers", None),
+        )
+
     @app.exception_handler(RequestValidationError)
     async def request_validation_handler(
         request: Request, exc: RequestValidationError
@@ -94,7 +88,6 @@ def _register_exception_handlers(app: FastAPI) -> None:
             description="An unexpected error occurred. Please try again later.",
             error_code="SERVER-500",
         )
-
         return JSONResponse(
             status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
             content=error_response.model_dump(),
@@ -109,9 +102,10 @@ def _format_validation_error(
     formatted_errors = []
 
     for error in errors:
-        field_path = ".".join(
+        locs = error["loc"]
-            str(loc) for loc in error["loc"] if loc not in _VALIDATION_LOCATION_PARAMS
+        if locs and locs[0] in _VALIDATION_LOCATION_PARAMS:
-        )
+            locs = locs[1:]
+        field_path = ".".join(str(loc) for loc in locs)
         formatted_errors.append(
             {
                 "field": field_path or "root",
@@ -133,34 +127,22 @@ def _format_validation_error(
     )
 
 
-def _custom_openapi(app: FastAPI) -> dict[str, Any]:
+def _patched_openapi(
-    """Generate custom OpenAPI schema with standardized error format.
+    app: FastAPI, original_openapi: Callable[[], dict[str, Any]]
-
+) -> dict[str, Any]:
-    Replaces default 422 validation error responses with the custom format.
+    """Generate the OpenAPI schema and replace default 422 responses.
 
     Args:
-        app: FastAPI application instance
+        app: FastAPI application instance.
+        original_openapi: The previous ``app.openapi`` callable to delegate to.
 
     Returns:
-        OpenAPI schema dict
+        Patched OpenAPI schema dict.
-
-    Example:
-        from fastapi import FastAPI
-        from fastapi_toolsets.exceptions import init_exceptions_handlers
-
-        app = FastAPI()
-        init_exceptions_handlers(app)  # Automatically sets custom OpenAPI
     """
     if app.openapi_schema:
         return app.openapi_schema
 
-    openapi_schema = get_openapi(
+    openapi_schema = original_openapi()
-        title=app.title,
-        version=app.version,
-        openapi_version=app.openapi_version,
-        description=app.description,
-        routes=app.routes,
-    )
 
     for path_data in openapi_schema.get("paths", {}).values():
         for operation in path_data.values():
@@ -170,7 +152,10 @@ def _custom_openapi(app: FastAPI) -> dict[str, Any]:
                         "description": "Validation Error",
                         "content": {
                             "application/json": {
-                                "example": {
+                                "examples": {
+                                    "VAL-422": {
+                                        "summary": "Validation Error",
+                                        "value": {
                                             "data": {
                                                 "errors": [
                                                     {
@@ -184,6 +169,8 @@ def _custom_openapi(app: FastAPI) -> dict[str, Any]:
                                             "message": "Validation Error",
                                             "description": "1 validation error(s) detected",
                                             "error_code": "VAL-422",
+                                        },
+                                    }
                                 }
                             }
                         },

src/fastapi_toolsets/models.py

@@ -0,0 +1,47 @@
+"""SQLAlchemy model mixins for common column patterns."""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, Uuid, func, text
+from sqlalchemy.orm import Mapped, mapped_column
+
+__all__ = [
+    "UUIDMixin",
+    "CreatedAtMixin",
+    "UpdatedAtMixin",
+    "TimestampMixin",
+]
+
+
+class UUIDMixin:
+    """Mixin that adds a UUID primary key auto-generated by the database."""
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        Uuid,
+        primary_key=True,
+        server_default=text("gen_random_uuid()"),
+    )
+
+
+class CreatedAtMixin:
+    """Mixin that adds a ``created_at`` timestamp column."""
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+    )
+
+
+class UpdatedAtMixin:
+    """Mixin that adds an ``updated_at`` timestamp column."""
+
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        server_default=func.now(),
+        onupdate=func.now(),
+    )
+
+
+class TimestampMixin(CreatedAtMixin, UpdatedAtMixin):
+    """Mixin that combines ``created_at`` and ``updated_at`` timestamp columns."""

tests/test_crud_search.py

@@ -430,7 +430,7 @@ class TestNoSearchableFieldsError:
         from fastapi_toolsets.exceptions import NoSearchableFieldsError
 
         error = NoSearchableFieldsError(User)
-        assert "User" in str(error)
+        assert "User" in error.api_error.desc
         assert error.model is User
 
     def test_error_raised_when_no_fields(self):
@@ -454,7 +454,7 @@ class TestNoSearchableFieldsError:
             build_search_filters(NoStringModel, "test")
 
         assert exc_info.value.model is NoStringModel
-        assert "NoStringModel" in str(exc_info.value)
+        assert "NoStringModel" in exc_info.value.api_error.desc
 
 
 class TestGetSearchableFields:

tests/test_db.py

@@ -14,6 +14,7 @@ from fastapi_toolsets.db import (
     lock_tables,
     wait_for_row_change,
 )
+from fastapi_toolsets.exceptions import NotFoundError
 
 from .conftest import DATABASE_URL, Base, Role, RoleCrud, User
 
@@ -307,9 +308,9 @@ class TestWaitForRowChange:
 
     @pytest.mark.anyio
     async def test_nonexistent_row_raises(self, db_session: AsyncSession):
-        """Raises LookupError when the row does not exist."""
+        """Raises NotFoundError when the row does not exist."""
         fake_id = uuid.uuid4()
-        with pytest.raises(LookupError, match="not found"):
+        with pytest.raises(NotFoundError, match="not found"):
             await wait_for_row_change(db_session, Role, fake_id, interval=0.05)
 
     @pytest.mark.anyio
@@ -326,7 +327,7 @@ class TestWaitForRowChange:
 
     @pytest.mark.anyio
     async def test_deleted_row_raises(self, db_session: AsyncSession, engine):
-        """Raises LookupError when the row is deleted during polling."""
+        """Raises NotFoundError when the row is deleted during polling."""
         role = Role(name="delete_role")
         db_session.add(role)
         await db_session.commit()
@@ -340,6 +341,6 @@ class TestWaitForRowChange:
                 await other.commit()
 
         delete_task = asyncio.create_task(delete_later())
-        with pytest.raises(LookupError):
+        with pytest.raises(NotFoundError):
             await wait_for_row_change(db_session, Role, role.id, interval=0.05)
         await delete_task

tests/test_exceptions.py

@@ -2,6 +2,7 @@
 
 import pytest
 from fastapi import FastAPI
+from fastapi.exceptions import HTTPException
 from fastapi.testclient import TestClient
 
 from fastapi_toolsets.exceptions import (
@@ -36,8 +37,8 @@ class TestApiException:
         assert error.api_error.msg == "I'm a teapot"
         assert str(error) == "I'm a teapot"
 
-    def test_custom_detail_message(self):
+    def test_detail_overrides_msg_and_str(self):
-        """Custom detail overrides default message."""
+        """detail sets both str(exc) and api_error.msg; class-level msg is unchanged."""
 
         class CustomError(ApiException):
             api_error = ApiError(
@@ -47,8 +48,172 @@ class TestApiException:
                 err_code="BAD-400",
             )
 
-        error = CustomError("Custom message")
+        error = CustomError("Widget not found")
-        assert str(error) == "Custom message"
+        assert str(error) == "Widget not found"
+        assert error.api_error.msg == "Widget not found"
+        assert CustomError.api_error.msg == "Bad Request"  # class unchanged
+
+    def test_desc_override(self):
+        """desc kwarg overrides api_error.desc on the instance only."""
+
+        class MyError(ApiException):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Default.", err_code="ERR-400"
+            )
+
+        err = MyError(desc="Custom desc.")
+        assert err.api_error.desc == "Custom desc."
+        assert MyError.api_error.desc == "Default."  # class unchanged
+
+    def test_data_override(self):
+        """data kwarg sets api_error.data on the instance only."""
+
+        class MyError(ApiException):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Default.", err_code="ERR-400"
+            )
+
+        err = MyError(data={"key": "value"})
+        assert err.api_error.data == {"key": "value"}
+        assert MyError.api_error.data is None  # class unchanged
+
+    def test_desc_and_data_override(self):
+        """detail, desc and data can all be overridden together."""
+
+        class MyError(ApiException):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Default.", err_code="ERR-400"
+            )
+
+        err = MyError("custom msg", desc="New desc.", data={"x": 1})
+        assert str(err) == "custom msg"
+        assert err.api_error.msg == "custom msg"  # detail also updates msg
+        assert err.api_error.desc == "New desc."
+        assert err.api_error.data == {"x": 1}
+        assert err.api_error.code == 400  # other fields unchanged
+
+    def test_class_api_error_not_mutated_after_instance_override(self):
+        """Raising with desc/data does not mutate the class-level api_error."""
+
+        class MyError(ApiException):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Default.", err_code="ERR-400"
+            )
+
+        MyError(desc="Changed", data={"x": 1})
+        assert MyError.api_error.desc == "Default."
+        assert MyError.api_error.data is None
+
+    def test_subclass_uses_super_with_desc_and_data(self):
+        """Subclasses can delegate detail/desc/data to super().__init__()."""
+
+        class BuildValidationError(ApiException):
+            api_error = ApiError(
+                code=422,
+                msg="Build Validation Error",
+                desc="The build configuration is invalid.",
+                err_code="BUILD-422",
+            )
+
+            def __init__(self, *errors: str) -> None:
+                super().__init__(
+                    f"{len(errors)} validation error(s)",
+                    desc=", ".join(errors),
+                    data={"errors": [{"message": e} for e in errors]},
+                )
+
+        err = BuildValidationError("Field A is required", "Field B is invalid")
+        assert str(err) == "2 validation error(s)"
+        assert err.api_error.msg == "2 validation error(s)"  # detail set msg
+        assert err.api_error.desc == "Field A is required, Field B is invalid"
+        assert err.api_error.data == {
+            "errors": [
+                {"message": "Field A is required"},
+                {"message": "Field B is invalid"},
+            ]
+        }
+        assert err.api_error.code == 422  # other fields unchanged
+
+    def test_detail_desc_data_in_http_response(self):
+        """detail/desc/data overrides all appear correctly in the FastAPI HTTP response."""
+
+        class DynamicError(ApiException):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Default.", err_code="ERR-400"
+            )
+
+            def __init__(self, message: str) -> None:
+                super().__init__(
+                    message,
+                    desc=f"Detail: {message}",
+                    data={"reason": message},
+                )
+
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/error")
+        async def raise_error():
+            raise DynamicError("something went wrong")
+
+        client = TestClient(app)
+        response = client.get("/error")
+
+        assert response.status_code == 400
+        body = response.json()
+        assert body["message"] == "something went wrong"
+        assert body["description"] == "Detail: something went wrong"
+        assert body["data"] == {"reason": "something went wrong"}
+
+
+class TestApiExceptionGuard:
+    """Tests for the __init_subclass__ api_error guard."""
+
+    def test_missing_api_error_raises_type_error(self):
+        """Defining a subclass without api_error raises TypeError at class creation time."""
+        with pytest.raises(
+            TypeError, match="must define an 'api_error' class attribute"
+        ):
+
+            class BrokenError(ApiException):
+                pass
+
+    def test_abstract_subclass_skips_guard(self):
+        """abstract=True allows intermediate base classes without api_error."""
+
+        class BaseGroupError(ApiException, abstract=True):
+            pass
+
+        # Concrete child must still define it
+        class ConcreteError(BaseGroupError):
+            api_error = ApiError(
+                code=400, msg="Error", desc="Desc.", err_code="ERR-400"
+            )
+
+        err = ConcreteError()
+        assert err.api_error.code == 400
+
+    def test_abstract_child_still_requires_api_error_on_concrete(self):
+        """Concrete subclass of an abstract class must define api_error."""
+
+        class Base(ApiException, abstract=True):
+            pass
+
+        with pytest.raises(
+            TypeError, match="must define an 'api_error' class attribute"
+        ):
+
+            class Concrete(Base):
+                pass
+
+    def test_inherited_api_error_satisfies_guard(self):
+        """Subclass that inherits api_error from a parent does not need its own."""
+
+        class ConcreteError(NotFoundError):
+            pass
+
+        err = ConcreteError()
+        assert err.api_error.code == 404
 
 
 class TestBuiltInExceptions:
@@ -90,7 +255,7 @@ class TestGenerateErrorResponses:
         assert responses[404]["description"] == "Not Found"
 
     def test_generates_multiple_responses(self):
-        """Generates responses for multiple exceptions."""
+        """Generates responses for multiple exceptions with distinct status codes."""
         responses = generate_error_responses(
             UnauthorizedError,
             ForbiddenError,
@@ -101,15 +266,24 @@ class TestGenerateErrorResponses:
         assert 403 in responses
         assert 404 in responses
 
-    def test_response_has_example(self):
+    def test_response_has_named_example(self):
-        """Generated response includes example."""
+        """Generated response uses named examples keyed by err_code."""
         responses = generate_error_responses(NotFoundError)
-        example = responses[404]["content"]["application/json"]["example"]
+        examples = responses[404]["content"]["application/json"]["examples"]
 
-        assert example["status"] == "FAIL"
+        assert "RES-404" in examples
-        assert example["error_code"] == "RES-404"
+        value = examples["RES-404"]["value"]
-        assert example["message"] == "Not Found"
+        assert value["status"] == "FAIL"
-        assert example["data"] is None
+        assert value["error_code"] == "RES-404"
+        assert value["message"] == "Not Found"
+        assert value["data"] is None
+
+    def test_response_example_has_summary(self):
+        """Each named example carries a summary equal to api_error.msg."""
+        responses = generate_error_responses(NotFoundError)
+        example = responses[404]["content"]["application/json"]["examples"]["RES-404"]
+
+        assert example["summary"] == "Not Found"
 
     def test_response_example_with_data(self):
         """Generated response includes data when set on ApiError."""
@@ -124,9 +298,49 @@ class TestGenerateErrorResponses:
             )
 
         responses = generate_error_responses(ErrorWithData)
-        example = responses[400]["content"]["application/json"]["example"]
+        value = responses[400]["content"]["application/json"]["examples"]["BAD-400"][
+            "value"
+        ]
 
-        assert example["data"] == {"details": "some context"}
+        assert value["data"] == {"details": "some context"}
+
+    def test_two_errors_same_code_both_present(self):
+        """Two exceptions with the same HTTP code produce two named examples."""
+
+        class BadRequestA(ApiException):
+            api_error = ApiError(
+                code=400, msg="Bad A", desc="Reason A.", err_code="ERR-A"
+            )
+
+        class BadRequestB(ApiException):
+            api_error = ApiError(
+                code=400, msg="Bad B", desc="Reason B.", err_code="ERR-B"
+            )
+
+        responses = generate_error_responses(BadRequestA, BadRequestB)
+
+        assert 400 in responses
+        examples = responses[400]["content"]["application/json"]["examples"]
+        assert "ERR-A" in examples
+        assert "ERR-B" in examples
+        assert examples["ERR-A"]["value"]["message"] == "Bad A"
+        assert examples["ERR-B"]["value"]["message"] == "Bad B"
+
+    def test_two_errors_same_code_single_top_level_entry(self):
+        """Two exceptions with the same HTTP code produce exactly one top-level entry."""
+
+        class BadRequestA(ApiException):
+            api_error = ApiError(
+                code=400, msg="Bad A", desc="Reason A.", err_code="ERR-A"
+            )
+
+        class BadRequestB(ApiException):
+            api_error = ApiError(
+                code=400, msg="Bad B", desc="Reason B.", err_code="ERR-B"
+            )
+
+        responses = generate_error_responses(BadRequestA, BadRequestB)
+        assert len([k for k in responses if k == 400]) == 1
 
 
 class TestInitExceptionsHandlers:
@@ -250,13 +464,68 @@ class TestInitExceptionsHandlers:
         assert data["status"] == "FAIL"
         assert data["error_code"] == "SERVER-500"
 
-    def test_custom_openapi_schema(self):
+    def test_handles_http_exception(self):
-        """Customizes OpenAPI schema for 422 responses."""
+        """Handles starlette HTTPException with consistent ErrorResponse envelope."""
         app = FastAPI()
         init_exceptions_handlers(app)
 
+        @app.get("/protected")
+        async def protected():
+            raise HTTPException(status_code=403, detail="Forbidden")
+
+        client = TestClient(app)
+        response = client.get("/protected")
+
+        assert response.status_code == 403
+        data = response.json()
+        assert data["status"] == "FAIL"
+        assert data["error_code"] == "HTTP-403"
+        assert data["message"] == "Forbidden"
+
+    def test_handles_http_exception_404_from_route(self):
+        """HTTPException(404) raised inside a route uses the consistent ErrorResponse envelope."""
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/items/{item_id}")
+        async def get_item(item_id: int):
+            raise HTTPException(status_code=404, detail="Item not found")
+
+        client = TestClient(app)
+        response = client.get("/items/99")
+
+        assert response.status_code == 404
+        data = response.json()
+        assert data["status"] == "FAIL"
+        assert data["error_code"] == "HTTP-404"
+        assert data["message"] == "Item not found"
+
+    def test_handles_http_exception_forwards_headers(self):
+        """HTTPException with WWW-Authenticate header forwards it in the response."""
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/secure")
+        async def secure():
+            raise HTTPException(
+                status_code=401,
+                detail="Not authenticated",
+                headers={"WWW-Authenticate": "Bearer"},
+            )
+
+        client = TestClient(app)
+        response = client.get("/secure")
+
+        assert response.status_code == 401
+        assert response.headers.get("www-authenticate") == "Bearer"
+
+    def test_custom_openapi_schema(self):
+        """Customises OpenAPI schema for 422 responses using named examples."""
         from pydantic import BaseModel
 
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
         class Item(BaseModel):
             name: str
 
@@ -269,8 +538,128 @@ class TestInitExceptionsHandlers:
         post_op = openapi["paths"]["/items"]["post"]
         assert "422" in post_op["responses"]
         resp_422 = post_op["responses"]["422"]
-        example = resp_422["content"]["application/json"]["example"]
+        examples = resp_422["content"]["application/json"]["examples"]
-        assert example["error_code"] == "VAL-422"
+        assert "VAL-422" in examples
+        assert examples["VAL-422"]["value"]["error_code"] == "VAL-422"
+
+    def test_custom_openapi_preserves_app_metadata(self):
+        """_patched_openapi preserves custom FastAPI app-level metadata."""
+        app = FastAPI(
+            title="My API",
+            version="2.0.0",
+            description="Custom description",
+        )
+        init_exceptions_handlers(app)
+
+        schema = app.openapi()
+        assert schema["info"]["title"] == "My API"
+        assert schema["info"]["version"] == "2.0.0"
+
+    def test_handles_response_validation_error(self):
+        """Handles ResponseValidationError with a structured 422 response."""
+        from pydantic import BaseModel
+
+        class CountResponse(BaseModel):
+            count: int
+
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/broken", response_model=CountResponse)
+        async def broken():
+            return {"count": "not-a-number"}  # triggers ResponseValidationError
+
+        client = TestClient(app, raise_server_exceptions=False)
+        response = client.get("/broken")
+
+        assert response.status_code == 422
+        data = response.json()
+        assert data["status"] == "FAIL"
+        assert data["error_code"] == "VAL-422"
+        assert "errors" in data["data"]
+
+    def test_handles_validation_error_with_non_standard_loc(self):
+        """Validation error with empty loc tuple maps the field to 'root'."""
+        from fastapi.exceptions import RequestValidationError
+
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/root-error")
+        async def root_error():
+            raise RequestValidationError(
+                [
+                    {
+                        "type": "custom",
+                        "loc": (),
+                        "msg": "root level error",
+                        "input": None,
+                        "url": "",
+                    }
+                ]
+            )
+
+        client = TestClient(app)
+        response = client.get("/root-error")
+
+        assert response.status_code == 422
+        data = response.json()
+        assert data["data"]["errors"][0]["field"] == "root"
+
+    def test_openapi_schema_cached_after_first_call(self):
+        """app.openapi() returns the cached schema on subsequent calls."""
+        from pydantic import BaseModel
+
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        class Item(BaseModel):
+            name: str
+
+        @app.post("/items")
+        async def create_item(item: Item):
+            return item
+
+        schema_first = app.openapi()
+        schema_second = app.openapi()
+        assert schema_first is schema_second
+
+    def test_openapi_skips_operations_without_422(self):
+        """_patched_openapi leaves operations that have no 422 response unchanged."""
+        app = FastAPI()
+        init_exceptions_handlers(app)
+
+        @app.get("/ping")
+        async def ping():
+            return {"ok": True}
+
+        schema = app.openapi()
+        get_op = schema["paths"]["/ping"]["get"]
+        assert "422" not in get_op["responses"]
+        assert "200" in get_op["responses"]
+
+    def test_openapi_skips_non_dict_path_item_values(self):
+        """_patched_openapi ignores non-dict values in path items (e.g. path-level parameters)."""
+        from fastapi_toolsets.exceptions.handler import _patched_openapi
+
+        app = FastAPI()
+
+        def fake_openapi() -> dict:
+            return {
+                "paths": {
+                    "/items": {
+                        "parameters": [
+                            {"name": "q", "in": "query"}
+                        ],  # list, not a dict
+                        "get": {"responses": {"200": {"description": "OK"}}},
+                    }
+                }
+            }
+
+        schema = _patched_openapi(app, fake_openapi)
+        # The list value was skipped without error; the GET operation is intact
+        assert schema["paths"]["/items"]["parameters"] == [{"name": "q", "in": "query"}]
+        assert "422" not in schema["paths"]["/items"]["get"]["responses"]
 
 
 class TestExceptionIntegration:
@@ -352,12 +741,12 @@ class TestInvalidOrderFieldError:
         assert error.field == "unknown"
         assert error.valid_fields == ["name", "created_at"]
 
-    def test_message_contains_field_and_valid_fields(self):
+    def test_description_contains_field_and_valid_fields(self):
-        """Exception message mentions the bad field and valid options."""
+        """api_error.desc mentions the bad field and valid options."""
         error = InvalidOrderFieldError("bad_field", ["name", "email"])
-        assert "bad_field" in str(error)
+        assert "bad_field" in error.api_error.desc
-        assert "name" in str(error)
+        assert "name" in error.api_error.desc
-        assert "email" in str(error)
+        assert "email" in error.api_error.desc
 
     def test_handled_as_422_by_exception_handler(self):
         """init_exceptions_handlers turns InvalidOrderFieldError into a 422 response."""

tests/test_models.py

@@ -0,0 +1,247 @@
+"""Tests for fastapi_toolsets.models mixins."""
+
+import uuid
+
+import pytest
+from sqlalchemy import String
+from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
+
+from fastapi_toolsets.models import (
+    CreatedAtMixin,
+    TimestampMixin,
+    UUIDMixin,
+    UpdatedAtMixin,
+)
+
+from .conftest import DATABASE_URL
+
+
+class MixinBase(DeclarativeBase):
+    pass
+
+
+class UUIDModel(MixinBase, UUIDMixin):
+    __tablename__ = "mixin_uuid_models"
+
+    name: Mapped[str] = mapped_column(String(50))
+
+
+class UpdatedAtModel(MixinBase, UpdatedAtMixin):
+    __tablename__ = "mixin_updated_at_models"
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    name: Mapped[str] = mapped_column(String(50))
+
+
+class CreatedAtModel(MixinBase, CreatedAtMixin):
+    __tablename__ = "mixin_created_at_models"
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    name: Mapped[str] = mapped_column(String(50))
+
+
+class TimestampModel(MixinBase, TimestampMixin):
+    __tablename__ = "mixin_timestamp_models"
+
+    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
+    name: Mapped[str] = mapped_column(String(50))
+
+
+class FullMixinModel(MixinBase, UUIDMixin, UpdatedAtMixin):
+    __tablename__ = "mixin_full_models"
+
+    name: Mapped[str] = mapped_column(String(50))
+
+
+@pytest.fixture(scope="function")
+async def mixin_session():
+    engine = create_async_engine(DATABASE_URL, echo=False)
+    async with engine.begin() as conn:
+        await conn.run_sync(MixinBase.metadata.create_all)
+
+    session_factory = async_sessionmaker(engine, expire_on_commit=False)
+    session = session_factory()
+
+    try:
+        yield session
+    finally:
+        await session.close()
+        async with engine.begin() as conn:
+            await conn.run_sync(MixinBase.metadata.drop_all)
+        await engine.dispose()
+
+
+class TestUUIDMixin:
+    @pytest.mark.anyio
+    async def test_uuid_generated_by_db(self, mixin_session):
+        """UUID is generated server-side and populated after flush."""
+        obj = UUIDModel(name="test")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+
+        assert obj.id is not None
+        assert isinstance(obj.id, uuid.UUID)
+
+    @pytest.mark.anyio
+    async def test_uuid_is_primary_key(self):
+        """UUIDMixin adds id as primary key column."""
+        pk_cols = [c.name for c in UUIDModel.__table__.primary_key]
+        assert pk_cols == ["id"]
+
+    @pytest.mark.anyio
+    async def test_each_row_gets_unique_uuid(self, mixin_session):
+        """Each inserted row gets a distinct UUID."""
+        a = UUIDModel(name="a")
+        b = UUIDModel(name="b")
+        mixin_session.add_all([a, b])
+        await mixin_session.flush()
+
+        assert a.id != b.id
+
+    @pytest.mark.anyio
+    async def test_uuid_server_default_set(self):
+        """Column has gen_random_uuid() as server default."""
+        col = UUIDModel.__table__.c["id"]
+        assert col.server_default is not None
+        assert "gen_random_uuid" in str(col.server_default.arg)
+
+
+class TestUpdatedAtMixin:
+    @pytest.mark.anyio
+    async def test_updated_at_set_on_insert(self, mixin_session):
+        """updated_at is populated after insert."""
+        obj = UpdatedAtModel(name="initial")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.updated_at is not None
+        assert obj.updated_at.tzinfo is not None  # timezone-aware
+
+    @pytest.mark.anyio
+    async def test_updated_at_changes_on_update(self, mixin_session):
+        """updated_at is updated when the row is modified."""
+        obj = UpdatedAtModel(name="initial")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        original_ts = obj.updated_at
+
+        obj.name = "modified"
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.updated_at >= original_ts
+
+    @pytest.mark.anyio
+    async def test_updated_at_column_is_not_nullable(self):
+        """updated_at column is non-nullable."""
+        col = UpdatedAtModel.__table__.c["updated_at"]
+        assert not col.nullable
+
+    @pytest.mark.anyio
+    async def test_updated_at_has_server_default(self):
+        """updated_at column has a server-side default."""
+        col = UpdatedAtModel.__table__.c["updated_at"]
+        assert col.server_default is not None
+
+    @pytest.mark.anyio
+    async def test_updated_at_has_onupdate(self):
+        """updated_at column has an onupdate clause."""
+        col = UpdatedAtModel.__table__.c["updated_at"]
+        assert col.onupdate is not None
+
+
+class TestCreatedAtMixin:
+    @pytest.mark.anyio
+    async def test_created_at_set_on_insert(self, mixin_session):
+        """created_at is populated after insert."""
+        obj = CreatedAtModel(name="new")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.created_at is not None
+        assert obj.created_at.tzinfo is not None  # timezone-aware
+
+    @pytest.mark.anyio
+    async def test_created_at_not_changed_on_update(self, mixin_session):
+        """created_at is not modified when the row is updated."""
+        obj = CreatedAtModel(name="original")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        original_ts = obj.created_at
+
+        obj.name = "updated"
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.created_at == original_ts
+
+    @pytest.mark.anyio
+    async def test_created_at_column_is_not_nullable(self):
+        """created_at column is non-nullable."""
+        col = CreatedAtModel.__table__.c["created_at"]
+        assert not col.nullable
+
+    @pytest.mark.anyio
+    async def test_created_at_has_no_onupdate(self):
+        """created_at column has no onupdate clause."""
+        col = CreatedAtModel.__table__.c["created_at"]
+        assert col.onupdate is None
+
+
+class TestTimestampMixin:
+    @pytest.mark.anyio
+    async def test_both_columns_set_on_insert(self, mixin_session):
+        """created_at and updated_at are both populated after insert."""
+        obj = TimestampModel(name="new")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.created_at is not None
+        assert obj.updated_at is not None
+
+    @pytest.mark.anyio
+    async def test_created_at_stable_updated_at_changes_on_update(self, mixin_session):
+        """On update: created_at stays the same, updated_at advances."""
+        obj = TimestampModel(name="original")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        original_created = obj.created_at
+        original_updated = obj.updated_at
+
+        obj.name = "modified"
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert obj.created_at == original_created
+        assert obj.updated_at >= original_updated
+
+    @pytest.mark.anyio
+    async def test_timestamp_mixin_has_both_columns(self):
+        """TimestampModel exposes both created_at and updated_at columns."""
+        col_names = {c.name for c in TimestampModel.__table__.columns}
+        assert "created_at" in col_names
+        assert "updated_at" in col_names
+
+
+class TestFullMixinModel:
+    @pytest.mark.anyio
+    async def test_combined_mixins_work_together(self, mixin_session):
+        """UUIDMixin and UpdatedAtMixin can be combined on the same model."""
+        obj = FullMixinModel(name="combined")
+        mixin_session.add(obj)
+        await mixin_session.flush()
+        await mixin_session.refresh(obj)
+
+        assert isinstance(obj.id, uuid.UUID)
+        assert obj.updated_at is not None
+        assert obj.updated_at.tzinfo is not None

uv.lock

@@ -251,7 +251,7 @@ wheels = [
 
 [[package]]
 name = "fastapi-toolsets"
-version = "1.3.0"
+version = "2.0.0"
 source = { editable = "." }
 dependencies = [
     { name = "asyncpg" },

zensical.toml

@@ -77,6 +77,10 @@ md_in_html = {}
 "pymdownx.tasklist" = {custom_checkbox = true}
 "pymdownx.tilde" = {}
 
+[project.markdown_extensions.pymdownx.emoji]
+emoji_index = "zensical.extensions.emoji.twemoji"
+emoji_generator = "zensical.extensions.emoji.to_svg"
+
 [project.markdown_extensions."pymdownx.highlight"]
 anchor_linenums = true
 line_spans = "__span"
@@ -95,3 +99,49 @@ permalink = true
 [project.markdown_extensions."pymdownx.snippets"]
 base_path = ["."]
 check_paths = true
+
+[[project.nav]]
+Home = "index.md"
+
+[[project.nav]]
+Modules = [
+    {CLI = "module/cli.md"},
+    {CRUD = "module/crud.md"},
+    {Database = "module/db.md"},
+    {Dependencies = "module/dependencies.md"},
+    {Exceptions = "module/exceptions.md"},
+    {Fixtures = "module/fixtures.md"},
+    {Logger = "module/logger.md"},
+    {Metrics = "module/metrics.md"},
+    {Models = "module/models.md"},
+    {Pytest = "module/pytest.md"},
+    {Schemas = "module/schemas.md"},
+]
+
+[[project.nav]]
+Reference = [
+    {CLI = "reference/cli.md"},
+    {CRUD = "reference/crud.md"},
+    {Database = "reference/db.md"},
+    {Dependencies = "reference/dependencies.md"},
+    {Exceptions = "reference/exceptions.md"},
+    {Fixtures = "reference/fixtures.md"},
+    {Logger = "reference/logger.md"},
+    {Metrics = "reference/metrics.md"},
+    {Models = "reference/models.md"},
+    {Pytest = "reference/pytest.md"},
+    {Schemas = "reference/schemas.md"},
+]
+
+[[project.nav]]
+Examples = [
+    {"Pagination & Search" = "examples/pagination-search.md"},
+]
+
+[[project.nav]]
+Migration = [
+    {"v2.0" = "migration/v2.md"},
+]
+
+[[project.nav]]
+"Changelog ↗" = "https://github.com/d3vyce/fastapi-toolsets/releases"