diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 68c3b8567..4c77f0967 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -5,3 +5,13 @@ repos:
       - id: ruff
         args: [--fix, --exit-non-zero-on-fix]
       - id: ruff-format
+
+  - repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.15.0
+    hooks:
+      - id: mypy
+        language_version: python
+        exclude: tests/.*
+        additional_dependencies:
+        - types-attrs
+        - pydantic
diff --git a/CHANGES.md b/CHANGES.md
index c1020119d..172882cb1 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -2,8 +2,18 @@
 
 ## [Unreleased]
 
+### Changed
+
+- switched from `attr.s` to `attrs.define` for dataclasses definition.
+- Extension's classes now HAVE TO be defined with `@define(slots=False)`
+- switched from `attr.id` to `attrs.field` for dataclasses's attributes definition
 - remove support of `cql-json` in Filter extension
 
+### Added
+
+- `py.typed` files for each sub-modules
+- type checking in `pre-commit`
+
 ## [5.2.1] - 2025-04-18
 
 ### Fixed
diff --git a/pyproject.toml b/pyproject.toml
index 12b4afbd5..d6d50b810 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,6 +23,12 @@ section-order = ["future", "standard-library", "third-party", "first-party", "lo
 [tool.ruff.format]
 quote-style = "double"
 
+[tool.mypy]
+ignore_missing_imports = true
+namespace_packages = true
+explicit_package_bases = true
+exclude = ["tests", ".venv"]
+
 [tool.bumpversion]
 current_version = "5.2.1"
 parse = """(?x)
diff --git a/stac_fastapi/api/stac_fastapi/api/app.py b/stac_fastapi/api/stac_fastapi/api/app.py
index ed39c31a7..206b1aa96 100644
--- a/stac_fastapi/api/stac_fastapi/api/app.py
+++ b/stac_fastapi/api/stac_fastapi/api/app.py
@@ -3,7 +3,7 @@
 
 from typing import Awaitable, Callable, Dict, List, Optional, Tuple, Type, Union
 
-import attr
+import attrs
 from brotli_asgi import BrotliMiddleware
 from fastapi import APIRouter, FastAPI
 from fastapi.params import Depends
@@ -39,7 +39,7 @@
 from stac_fastapi.types.search import BaseSearchGetRequest, BaseSearchPostRequest
 
 
-@attr.s
+@attrs.define
 class StacApi:
     """StacApi factory.
 
@@ -75,30 +75,30 @@ class StacApi:
 
     """
 
-    settings: ApiSettings = attr.ib()
-    client: Union[AsyncBaseCoreClient, BaseCoreClient] = attr.ib()
-    extensions: List[ApiExtension] = attr.ib(default=attr.Factory(list))
-    exceptions: Dict[Type[Exception], int] = attr.ib(
-        default=attr.Factory(lambda: DEFAULT_STATUS_CODES)
+    settings: ApiSettings = attrs.field()
+    client: Union[AsyncBaseCoreClient, BaseCoreClient] = attrs.field()
+    extensions: List[ApiExtension] = attrs.field(factory=list)
+    exceptions: Dict[Type[Exception], int] = attrs.field(
+        factory=lambda: DEFAULT_STATUS_CODES
     )
-    title: str = attr.ib(
-        default=attr.Factory(
+    title: str = attrs.field(
+        default=attrs.Factory(
             lambda self: self.settings.stac_fastapi_title, takes_self=True
         )
     )
-    api_version: str = attr.ib(
-        default=attr.Factory(
+    api_version: str = attrs.field(
+        default=attrs.Factory(
             lambda self: self.settings.stac_fastapi_version, takes_self=True
         )
     )
-    stac_version: str = attr.ib(default=STAC_VERSION)
-    description: str = attr.ib(
-        default=attr.Factory(
+    stac_version: str = attrs.field(default=STAC_VERSION)
+    description: str = attrs.field(
+        default=attrs.Factory(
             lambda self: self.settings.stac_fastapi_description, takes_self=True
         )
     )
-    app: FastAPI = attr.ib(
-        default=attr.Factory(
+    app: FastAPI = attrs.field(
+        default=attrs.Factory(
             lambda self: FastAPI(
                 openapi_url=self.settings.openapi_url,
                 docs_url=self.settings.docs_url,
@@ -112,20 +112,20 @@ class StacApi:
         ),
         converter=update_openapi,
     )
-    router: APIRouter = attr.ib(default=attr.Factory(APIRouter))
-    search_get_request_model: Type[BaseSearchGetRequest] = attr.ib(
+    router: APIRouter = attrs.field(default=attrs.Factory(APIRouter))
+    search_get_request_model: Type[BaseSearchGetRequest] = attrs.field(
         default=BaseSearchGetRequest
     )
-    search_post_request_model: Type[BaseSearchPostRequest] = attr.ib(
+    search_post_request_model: Type[BaseSearchPostRequest] = attrs.field(
         default=BaseSearchPostRequest
     )
-    collections_get_request_model: Type[APIRequest] = attr.ib(default=EmptyRequest)
-    collection_get_request_model: Type[APIRequest] = attr.ib(default=CollectionUri)
-    items_get_request_model: Type[APIRequest] = attr.ib(default=ItemCollectionUri)
-    item_get_request_model: Type[APIRequest] = attr.ib(default=ItemUri)
-    response_class: Type[Response] = attr.ib(default=JSONResponse)
-    middlewares: List[Middleware] = attr.ib(
-        default=attr.Factory(
+    collections_get_request_model: Type[APIRequest] = attrs.field(default=EmptyRequest)
+    collection_get_request_model: Type[APIRequest] = attrs.field(default=CollectionUri)
+    items_get_request_model: Type[APIRequest] = attrs.field(default=ItemCollectionUri)
+    item_get_request_model: Type[APIRequest] = attrs.field(default=ItemUri)
+    response_class: Type[Response] = attrs.field(default=JSONResponse)
+    middlewares: List[Middleware] = attrs.field(
+        default=attrs.Factory(
             lambda: [
                 Middleware(BrotliMiddleware),
                 Middleware(CORSMiddleware),
@@ -133,8 +133,8 @@ class StacApi:
             ]
         )
     )
-    route_dependencies: List[Tuple[List[Scope], List[Depends]]] = attr.ib(default=[])
-    health_check: Union[Callable[[], Dict], Callable[[], Awaitable[Dict]]] = attr.ib(
+    route_dependencies: List[Tuple[List[Scope], List[Depends]]] = attrs.field(default=[])
+    health_check: Union[Callable[[], Dict], Callable[[], Awaitable[Dict]]] = attrs.field(
         default=lambda: {"status": "UP"}
     )
 
diff --git a/stac_fastapi/api/stac_fastapi/api/models.py b/stac_fastapi/api/stac_fastapi/api/models.py
index fc764efe1..ba1405dd0 100644
--- a/stac_fastapi/api/stac_fastapi/api/models.py
+++ b/stac_fastapi/api/stac_fastapi/api/models.py
@@ -2,7 +2,7 @@
 
 from typing import List, Literal, Optional, Type, Union
 
-import attr
+import attrs
 from fastapi import Path, Query
 from pydantic import BaseModel, create_model
 from stac_pydantic.shared import BBox
@@ -49,14 +49,19 @@ def create_request_model(
 
     # Handle GET requests
     if all([issubclass(m, APIRequest) for m in models]):
-        return attr.make_class(model_name, attrs={}, bases=tuple(models))
+        return attrs.make_class(
+            model_name,
+            attrs={**{}},
+            bases=tuple(models),
+        )
 
     # Handle POST requests
     elif all([issubclass(m, BaseModel) for m in models]):
         for model in models:
             for k, field_info in model.model_fields.items():
                 fields[k] = (field_info.annotation, field_info)
-        return create_model(model_name, **fields, __base__=base_model)
+
+        return create_model(model_name, **fields, __base__=base_model)  # type: ignore
 
     raise TypeError("Mixed Request Model types. Check extension request types.")
 
@@ -88,41 +93,41 @@ def create_post_request_model(
     )
 
 
-@attr.s
+@attrs.define
 class CollectionUri(APIRequest):
     """Get or delete collection."""
 
-    collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
+    collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
 
 
-@attr.s
+@attrs.define
 class ItemUri(APIRequest):
     """Get or delete item."""
 
-    collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
-    item_id: Annotated[str, Path(description="Item ID")] = attr.ib()
+    collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
+    item_id: Annotated[str, Path(description="Item ID")] = attrs.field()
 
 
-@attr.s
+@attrs.define
 class EmptyRequest(APIRequest):
     """Empty request."""
 
     ...
 
 
-@attr.s
+@attrs.define
 class ItemCollectionUri(APIRequest, DatetimeMixin):
     """Get item collection."""
 
-    collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
+    collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
     limit: Annotated[
         Optional[Limit],
         Query(
             description="Limits the number of results that are included in each page of the response (capped to 10_000)."  # noqa: E501
         ),
-    ] = attr.ib(default=10)
-    bbox: Optional[BBox] = attr.ib(default=None, converter=_bbox_converter)
-    datetime: DateTimeQueryType = attr.ib(default=None, validator=_validate_datetime)
+    ] = attrs.field(default=10)
+    bbox: Optional[BBox] = attrs.field(default=None, converter=_bbox_converter)
+    datetime: DateTimeQueryType = attrs.field(default=None, validator=_validate_datetime)
 
 
 class GeoJSONResponse(JSONResponse):
diff --git a/stac_fastapi/api/stac_fastapi/api/py.typed b/stac_fastapi/api/stac_fastapi/api/py.typed
new file mode 100644
index 000000000..e69de29bb
diff --git a/stac_fastapi/api/stac_fastapi/api/routes.py b/stac_fastapi/api/stac_fastapi/api/routes.py
index 79150c473..9235ef54a 100644
--- a/stac_fastapi/api/stac_fastapi/api/routes.py
+++ b/stac_fastapi/api/stac_fastapi/api/routes.py
@@ -3,7 +3,7 @@
 import copy
 import functools
 import inspect
-from typing import Any, Callable, Dict, List, Optional, Type, TypedDict, Union
+from typing import Any, Awaitable, Callable, Dict, List, Optional, Type, TypedDict, Union
 
 from fastapi import Depends, FastAPI, params
 from fastapi.datastructures import DefaultPlaceholder
@@ -48,30 +48,26 @@ def create_async_endpoint(
     if not inspect.iscoroutinefunction(func):
         func = sync_to_async(func)
 
-    if issubclass(request_model, APIRequest):
+    _endpoint: Callable[[Any, Any], Awaitable[Any]]
+
+    if isinstance(request_model, dict):
 
         async def _endpoint(
             request: Request,
-            request_data: request_model = Depends(),  # type:ignore
+            request_data: Dict[str, Any],
         ):
             """Endpoint."""
-            return _wrap_response(await func(request=request, **request_data.kwargs()))
+            return _wrap_response(await func(request_data, request=request))
 
-    elif issubclass(request_model, BaseModel):
+    elif issubclass(request_model, APIRequest):
 
-        async def _endpoint(
-            request: Request,
-            request_data: request_model,  # type:ignore
-        ):
+        async def _endpoint(request: Request, request_data=Depends(request_model)):
             """Endpoint."""
-            return _wrap_response(await func(request_data, request=request))
+            return _wrap_response(await func(request=request, **request_data.kwargs()))
 
-    else:
+    elif issubclass(request_model, BaseModel):
 
-        async def _endpoint(
-            request: Request,
-            request_data: Dict[str, Any],  # type:ignore
-        ):
+        async def _endpoint(request: Request, request_data: request_model):  # type: ignore
             """Endpoint."""
             return _wrap_response(await func(request_data, request=request))
 
diff --git a/stac_fastapi/api/tests/test_app.py b/stac_fastapi/api/tests/test_app.py
index 5500303ef..41cb1b9fb 100644
--- a/stac_fastapi/api/tests/test_app.py
+++ b/stac_fastapi/api/tests/test_app.py
@@ -1,6 +1,6 @@
 from typing import List, Optional, Union
 
-import attr
+import attrs
 import pytest
 from fastapi import Path, Query
 from fastapi.testclient import TestClient
@@ -385,25 +385,25 @@ def item_collection(
 def test_request_model(AsyncTestCoreClient):
     """Test if request models are passed correctly."""
 
-    @attr.s
+    @attrs.define
     class CollectionsRequest(APIRequest):
-        user: Annotated[str, Query(...)] = attr.ib()
+        user: Annotated[str, Query(...)] = attrs.field()
 
-    @attr.s
+    @attrs.define
     class CollectionRequest(APIRequest):
-        collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
-        user: Annotated[str, Query(...)] = attr.ib()
+        collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
+        user: Annotated[str, Query(...)] = attrs.field()
 
-    @attr.s
+    @attrs.define
     class ItemsRequest(APIRequest):
-        collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
-        user: Annotated[str, Query(...)] = attr.ib()
+        collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
+        user: Annotated[str, Query(...)] = attrs.field()
 
-    @attr.s
+    @attrs.define
     class ItemRequest(APIRequest):
-        collection_id: Annotated[str, Path(description="Collection ID")] = attr.ib()
-        item_id: Annotated[str, Path(description="Item ID")] = attr.ib()
-        user: Annotated[str, Query(...)] = attr.ib()
+        collection_id: Annotated[str, Path(description="Collection ID")] = attrs.field()
+        item_id: Annotated[str, Path(description="Item ID")] = attrs.field()
+        user: Annotated[str, Query(...)] = attrs.field()
 
     test_app = app.StacApi(
         settings=ApiSettings(),
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/aggregation.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/aggregation.py
index c6e892914..35b97f266 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/aggregation.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/aggregation.py
@@ -2,7 +2,7 @@
 from enum import Enum
 from typing import List, Union
 
-import attr
+import attrs
 from fastapi import APIRouter, FastAPI
 
 from stac_fastapi.api.models import CollectionUri, EmptyRequest
@@ -23,7 +23,7 @@ class AggregationConformanceClasses(str, Enum):
     AGGREGATION = "https://api.stacspec.org/v0.3.0/aggregation"
 
 
-@attr.s
+@attrs.define
 class AggregationExtension(ApiExtension):
     """Aggregation Extension.
 
@@ -53,14 +53,14 @@ class AggregationExtension(ApiExtension):
     GET = AggregationExtensionGetRequest
     POST = AggregationExtensionPostRequest
 
-    client: Union[AsyncBaseAggregationClient, BaseAggregationClient] = attr.ib(
+    client: Union[AsyncBaseAggregationClient, BaseAggregationClient] = attrs.field(
         factory=BaseAggregationClient
     )
 
-    conformance_classes: List[str] = attr.ib(
-        default=[AggregationConformanceClasses.AGGREGATION]
+    conformance_classes: List[str] = attrs.field(
+        default=[AggregationConformanceClasses.AGGREGATION.value]
     )
-    router: APIRouter = attr.ib(factory=APIRouter)
+    router: APIRouter = attrs.field(factory=APIRouter)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/client.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/client.py
index 23d90fb28..9d8c8f65a 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/client.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/client.py
@@ -3,7 +3,7 @@
 import abc
 from typing import List, Optional, Union
 
-import attr
+import attrs
 from geojson_pydantic.geometries import Geometry
 from stac_pydantic.shared import BBox
 
@@ -12,7 +12,7 @@
 from .types import Aggregation, AggregationCollection
 
 
-@attr.s
+@attrs.define
 class BaseAggregationClient(abc.ABC):
     """Defines a pattern for implementing the STAC aggregation extension."""
 
@@ -67,7 +67,7 @@ def aggregate(
         )
 
 
-@attr.s
+@attrs.define
 class AsyncBaseAggregationClient(abc.ABC):
     """Defines an async pattern for implementing the STAC aggregation extension."""
 
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/request.py
index 4e72e0005..f73df9f8f 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/aggregation/request.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import Field
 from typing_extensions import Annotated
@@ -23,11 +23,13 @@ def _agg_converter(
     return str2list(val)
 
 
-@attr.s
+@attrs.define(slots=False)
 class AggregationExtensionGetRequest(BaseSearchGetRequest):
     """Aggregation Extension GET request model."""
 
-    aggregations: Optional[List[str]] = attr.ib(default=None, converter=_agg_converter)
+    aggregations: Optional[List[str]] = attrs.field(
+        default=None, converter=_agg_converter
+    )
 
 
 class AggregationExtensionPostRequest(BaseSearchPostRequest):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/client.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/client.py
index ac148dfb4..b8b0d3a23 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/client.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/client.py
@@ -2,14 +2,14 @@
 
 import abc
 
-import attr
+import attrs
 
-from stac_fastapi.types import stac
+from stac_fastapi.types.stac import ItemCollection
 
 from .request import BaseCollectionSearchPostRequest
 
 
-@attr.s
+@attrs.define
 class AsyncBaseCollectionSearchClient(abc.ABC):
     """Defines a pattern for implementing the STAC collection-search POST extension."""
 
@@ -18,7 +18,7 @@ async def post_all_collections(
         self,
         search_request: BaseCollectionSearchPostRequest,
         **kwargs,
-    ) -> stac.ItemCollection:
+    ) -> ItemCollection:
         """Get all available collections.
 
         Called with `POST /collections`.
@@ -30,14 +30,14 @@ async def post_all_collections(
         ...
 
 
-@attr.s
+@attrs.define
 class BaseCollectionSearchClient(abc.ABC):
     """Defines a pattern for implementing the STAC collection-search POST extension."""
 
     @abc.abstractmethod
     def post_all_collections(
         self, search_request: BaseCollectionSearchPostRequest, **kwargs
-    ) -> stac.ItemCollection:
+    ) -> ItemCollection:
         """Get all available collections.
 
         Called with `POST /collections`.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/collection_search.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/collection_search.py
index e5ab77b50..ba7b563cd 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/collection_search.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/collection_search.py
@@ -1,9 +1,9 @@
 """Collection-Search extension."""
 
 from enum import Enum
-from typing import List, Optional, Union
+from typing import Any, List, Optional, Sequence, Union
 
-import attr
+import attrs
 from fastapi import APIRouter, FastAPI
 from stac_pydantic.api.collections import Collections
 from stac_pydantic.shared import MimeTypes
@@ -28,7 +28,7 @@ class CollectionSearchConformanceClasses(str, Enum):
     BASIS = "http://www.opengis.net/spec/ogcapi-common-2/1.0/conf/simple-query"
 
 
-@attr.s
+@attrs.define
 class CollectionSearchExtension(ApiExtension):
     """Collection-Search Extension.
 
@@ -47,16 +47,18 @@ class CollectionSearchExtension(ApiExtension):
             the extension
     """
 
-    GET: BaseCollectionSearchGetRequest = attr.ib(default=BaseCollectionSearchGetRequest)
-    POST = None
+    GET: BaseCollectionSearchGetRequest = attrs.field(
+        default=BaseCollectionSearchGetRequest
+    )
+    POST = attrs.field(default=None, init=False)
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: Sequence[str] = attrs.field(
         default=[
-            CollectionSearchConformanceClasses.COLLECTIONSEARCH,
-            CollectionSearchConformanceClasses.BASIS,
+            CollectionSearchConformanceClasses.COLLECTIONSEARCH.value,
+            CollectionSearchConformanceClasses.BASIS.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
@@ -73,13 +75,15 @@ def register(self, app: FastAPI) -> None:
     def from_extensions(
         cls,
         extensions: List[ApiExtension],
+        *,
         schema_href: Optional[str] = None,
+        **kwargs: Any,
     ) -> "CollectionSearchExtension":
         """Create CollectionSearchExtension object from extensions."""
 
         conformance_classes = [
-            CollectionSearchConformanceClasses.COLLECTIONSEARCH,
-            CollectionSearchConformanceClasses.BASIS,
+            CollectionSearchConformanceClasses.COLLECTIONSEARCH.value,
+            CollectionSearchConformanceClasses.BASIS.value,
         ]
         for ext in extensions:
             conformance_classes.extend(ext.conformance_classes)
@@ -98,7 +102,7 @@ def from_extensions(
         )
 
 
-@attr.s
+@attrs.define
 class CollectionSearchPostExtension(CollectionSearchExtension):
     """Collection-Search Extension.
 
@@ -115,19 +119,23 @@ class CollectionSearchPostExtension(CollectionSearchExtension):
             the extension
     """
 
-    client: Union[AsyncBaseCollectionSearchClient, BaseCollectionSearchClient] = attr.ib()
-    settings: ApiSettings = attr.ib()
-    conformance_classes: List[str] = attr.ib(
+    client: Union[
+        AsyncBaseCollectionSearchClient, BaseCollectionSearchClient
+    ] = attrs.field()
+    settings: ApiSettings = attrs.field()
+    conformance_classes: Sequence[str] = attrs.field(
         default=[
-            CollectionSearchConformanceClasses.COLLECTIONSEARCH,
-            CollectionSearchConformanceClasses.BASIS,
+            CollectionSearchConformanceClasses.COLLECTIONSEARCH.value,
+            CollectionSearchConformanceClasses.BASIS.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
-    router: APIRouter = attr.ib(factory=APIRouter)
+    schema_href: Optional[str] = attrs.field(default=None)
+    router: APIRouter = attrs.field(factory=APIRouter)
 
-    GET: BaseCollectionSearchGetRequest = attr.ib(default=BaseCollectionSearchGetRequest)
-    POST: BaseCollectionSearchPostRequest = attr.ib(
+    GET: BaseCollectionSearchGetRequest = attrs.field(
+        default=BaseCollectionSearchGetRequest
+    )
+    POST: BaseCollectionSearchPostRequest = attrs.field(
         default=BaseCollectionSearchPostRequest
     )
 
@@ -163,19 +171,19 @@ def register(self, app: FastAPI) -> None:
         app.include_router(self.router)
 
     @classmethod
-    def from_extensions(
+    def from_extensions(  # type: ignore
         cls,
         extensions: List[ApiExtension],
         *,
+        schema_href: Optional[str] = None,
         client: Union[AsyncBaseCollectionSearchClient, BaseCollectionSearchClient],
         settings: ApiSettings,
-        schema_href: Optional[str] = None,
         router: Optional[APIRouter] = None,
     ) -> "CollectionSearchPostExtension":
         """Create CollectionSearchPostExtension object from extensions."""
         conformance_classes = [
-            CollectionSearchConformanceClasses.COLLECTIONSEARCH,
-            CollectionSearchConformanceClasses.BASIS,
+            CollectionSearchConformanceClasses.COLLECTIONSEARCH.value,
+            CollectionSearchConformanceClasses.BASIS.value,
         ]
         for ext in extensions:
             conformance_classes.extend(ext.conformance_classes)
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/request.py
index 2ac4b608d..716b5a827 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/collection_search/request.py
@@ -3,7 +3,7 @@
 from datetime import datetime as dt
 from typing import List, Optional, Tuple, cast
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field, PrivateAttr, ValidationInfo, field_validator
 from stac_pydantic.api.search import SearchDatetime
@@ -20,18 +20,18 @@
 )
 
 
-@attr.s
+@attrs.define(slots=False)
 class BaseCollectionSearchGetRequest(APIRequest, DatetimeMixin):
     """Basics additional Collection-Search parameters for the GET request."""
 
-    bbox: Optional[BBox] = attr.ib(default=None, converter=_bbox_converter)
-    datetime: DateTimeQueryType = attr.ib(default=None, validator=_validate_datetime)
+    bbox: Optional[BBox] = attrs.field(default=None, converter=_bbox_converter)
+    datetime: DateTimeQueryType = attrs.field(default=None, validator=_validate_datetime)
     limit: Annotated[
         Optional[Limit],
         Query(
             description="Limits the number of results that are included in each page of the response."  # noqa: E501
         ),
-    ] = attr.ib(default=10)
+    ] = attrs.field(default=10)
 
 
 class BaseCollectionSearchPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/fields.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/fields.py
index 0b6e4177d..f4939d43b 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/fields.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/fields.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -23,7 +23,7 @@ class FieldsConformanceClasses(str, Enum):
     COLLECTIONS = "https://api.stacspec.org/v1.0.0-rc.1/collection-search#fields"
 
 
-@attr.s
+@attrs.define
 class FieldsExtension(ApiExtension):
     """Fields Extension.
 
@@ -45,12 +45,12 @@ class FieldsExtension(ApiExtension):
     GET = FieldsExtensionGetRequest
     POST = FieldsExtensionPostRequest
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         factory=lambda: [
-            FieldsConformanceClasses.SEARCH,
+            FieldsConformanceClasses.SEARCH.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/request.py
index 28b0003d6..2ca2f9f4d 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/fields/request.py
@@ -2,7 +2,7 @@
 
 from typing import Dict, List, Optional, Set
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
@@ -59,11 +59,11 @@ def _fields_converter(
     return str2list(val)
 
 
-@attr.s
+@attrs.define(slots=False)
 class FieldsExtensionGetRequest(APIRequest):
     """Additional fields for the GET request."""
 
-    fields: Optional[List[str]] = attr.ib(default=None, converter=_fields_converter)
+    fields: Optional[List[str]] = attrs.field(default=None, converter=_fields_converter)
 
 
 class FieldsExtensionPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/client.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/client.py
index 2ee59b770..d8d0662f9 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/client.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/client.py
@@ -3,10 +3,10 @@
 import abc
 from typing import Any, Dict, Optional
 
-import attr
+import attrs
 
 
-@attr.s
+@attrs.define
 class AsyncBaseFiltersClient(abc.ABC):
     """Defines a pattern for implementing the STAC filter extension."""
 
@@ -32,7 +32,7 @@ async def get_queryables(
         }
 
 
-@attr.s
+@attrs.define
 class BaseFiltersClient(abc.ABC):
     """Defines a pattern for implementing the STAC filter extension."""
 
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/filter.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/filter.py
index 7e8d7f57c..7fa97b23a 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/filter.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/filter.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Type, Union
 
-import attr
+import attrs
 from fastapi import APIRouter, FastAPI
 from starlette.responses import Response
 
@@ -48,7 +48,7 @@ class FilterConformanceClasses(str, Enum):
     )
 
 
-@attr.s
+@attrs.define
 class FilterExtension(ApiExtension):
     """Filter Extension.
 
@@ -68,21 +68,21 @@ class FilterExtension(ApiExtension):
     GET = FilterExtensionGetRequest
     POST = FilterExtensionPostRequest
 
-    client: Union[AsyncBaseFiltersClient, BaseFiltersClient] = attr.ib(
+    client: Union[AsyncBaseFiltersClient, BaseFiltersClient] = attrs.field(
         factory=BaseFiltersClient
     )
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FilterConformanceClasses.FILTER,
-            FilterConformanceClasses.SEARCH,
-            FilterConformanceClasses.ITEMS,
-            FilterConformanceClasses.BASIC_CQL2,
-            FilterConformanceClasses.CQL2_JSON,
-            FilterConformanceClasses.CQL2_TEXT,
+            FilterConformanceClasses.FILTER.value,
+            FilterConformanceClasses.SEARCH.value,
+            FilterConformanceClasses.ITEMS.value,
+            FilterConformanceClasses.BASIC_CQL2.value,
+            FilterConformanceClasses.CQL2_JSON.value,
+            FilterConformanceClasses.CQL2_TEXT.value,
         ]
     )
-    router: APIRouter = attr.ib(factory=APIRouter)
-    response_class: Type[Response] = attr.ib(default=JSONSchemaResponse)
+    router: APIRouter = attrs.field(factory=APIRouter)
+    response_class: Type[Response] = attrs.field(default=JSONSchemaResponse)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
@@ -127,17 +127,17 @@ def register(self, app: FastAPI) -> None:
         app.include_router(self.router, tags=["Filter Extension"])
 
 
-@attr.s
+@attrs.define
 class SearchFilterExtension(FilterExtension):
     """Item Search Filter Extension."""
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FilterConformanceClasses.FILTER,
-            FilterConformanceClasses.SEARCH,
-            FilterConformanceClasses.BASIC_CQL2,
-            FilterConformanceClasses.CQL2_JSON,
-            FilterConformanceClasses.CQL2_TEXT,
+            FilterConformanceClasses.FILTER.value,
+            FilterConformanceClasses.SEARCH.value,
+            FilterConformanceClasses.BASIC_CQL2.value,
+            FilterConformanceClasses.CQL2_JSON.value,
+            FilterConformanceClasses.CQL2_TEXT.value,
         ]
     )
 
@@ -169,17 +169,17 @@ def register(self, app: FastAPI) -> None:
         app.include_router(self.router, tags=["Filter Extension"])
 
 
-@attr.s
+@attrs.define
 class ItemCollectionFilterExtension(FilterExtension):
     """Item Collection Filter Extension."""
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FilterConformanceClasses.FILTER,
-            FilterConformanceClasses.ITEMS,
-            FilterConformanceClasses.BASIC_CQL2,
-            FilterConformanceClasses.CQL2_JSON,
-            FilterConformanceClasses.CQL2_TEXT,
+            FilterConformanceClasses.FILTER.value,
+            FilterConformanceClasses.ITEMS.value,
+            FilterConformanceClasses.BASIC_CQL2.value,
+            FilterConformanceClasses.CQL2_JSON.value,
+            FilterConformanceClasses.CQL2_TEXT.value,
         ]
     )
 
@@ -211,17 +211,17 @@ def register(self, app: FastAPI) -> None:
         app.include_router(self.router, tags=["Filter Extension"])
 
 
-@attr.s
+@attrs.define
 class CollectionSearchFilterExtension(FilterExtension):
     """Collection Search Filter Extension."""
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FilterConformanceClasses.FILTER,
-            FilterConformanceClasses.COLLECTIONS,
-            FilterConformanceClasses.BASIC_CQL2,
-            FilterConformanceClasses.CQL2_JSON,
-            FilterConformanceClasses.CQL2_TEXT,
+            FilterConformanceClasses.FILTER.value,
+            FilterConformanceClasses.COLLECTIONS.value,
+            FilterConformanceClasses.BASIC_CQL2.value,
+            FilterConformanceClasses.CQL2_JSON.value,
+            FilterConformanceClasses.CQL2_TEXT.value,
         ]
     )
 
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
index 08514e4fc..051e51e50 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/filter/request.py
@@ -2,7 +2,7 @@
 
 from typing import Any, Dict, Literal, Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
@@ -12,7 +12,7 @@
 FilterLang = Literal["cql2-json", "cql2-text"]
 
 
-@attr.s
+@attrs.define(slots=False)
 class FilterExtensionGetRequest(APIRequest):
     """Filter extension GET request model."""
 
@@ -30,21 +30,21 @@ class FilterExtensionGetRequest(APIRequest):
                 },
             },
         ),
-    ] = attr.ib(default=None)
+    ] = attrs.field(default=None)
     filter_crs: Annotated[
         Optional[str],
         Query(
             alias="filter-crs",
             description="The coordinate reference system (CRS) used by spatial literals in the 'filter' value. Default is `http://www.opengis.net/def/crs/OGC/1.3/CRS84`",  # noqa: E501
         ),
-    ] = attr.ib(default=None)
+    ] = attrs.field(default=None)
     filter_lang: Annotated[
         Optional[FilterLang],
         Query(
             alias="filter-lang",
             description="The CQL filter encoding that the 'filter' value uses.",
         ),
-    ] = attr.ib(default="cql2-text")
+    ] = attrs.field(default="cql2-text")
 
 
 class FilterExtensionPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/free_text.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/free_text.py
index 67aaa2b27..0ec13dfb5 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/free_text.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/free_text.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -40,7 +40,7 @@ class FreeTextConformanceClasses(str, Enum):
     )
 
 
-@attr.s
+@attrs.define
 class FreeTextExtension(ApiExtension):
     """Free-text Extension.
 
@@ -54,12 +54,12 @@ class FreeTextExtension(ApiExtension):
     GET = FreeTextExtensionGetRequest
     POST = FreeTextExtensionPostRequest
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FreeTextConformanceClasses.SEARCH,
+            FreeTextConformanceClasses.SEARCH.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
@@ -73,7 +73,7 @@ def register(self, app: FastAPI) -> None:
         pass
 
 
-@attr.s
+@attrs.define
 class FreeTextAdvancedExtension(ApiExtension):
     """Free-text Extension.
 
@@ -87,12 +87,12 @@ class FreeTextAdvancedExtension(ApiExtension):
     GET = FreeTextAdvancedExtensionGetRequest
     POST = FreeTextAdvancedExtensionPostRequest
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         default=[
-            FreeTextConformanceClasses.SEARCH_ADVANCED,
+            FreeTextConformanceClasses.SEARCH_ADVANCED.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/request.py
index 67de422d3..54706f061 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/free_text/request.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
@@ -27,11 +27,11 @@ def _ft_converter(
     return None
 
 
-@attr.s
+@attrs.define(slots=False)
 class FreeTextExtensionGetRequest(APIRequest):
     """Free-text Extension GET request model."""
 
-    q: Optional[List[str]] = attr.ib(default=None, converter=_ft_converter)
+    q: Optional[List[str]] = attrs.field(default=None, converter=_ft_converter)
 
 
 class FreeTextExtensionPostRequest(BaseModel):
@@ -43,7 +43,7 @@ class FreeTextExtensionPostRequest(BaseModel):
     )
 
 
-@attr.s
+@attrs.define(slots=False)
 class FreeTextAdvancedExtensionGetRequest(APIRequest):
     """Free-text Extension GET request model."""
 
@@ -56,7 +56,7 @@ class FreeTextAdvancedExtensionGetRequest(APIRequest):
                 "Coastal": {"value": "ocean,coast"},
             },
         ),
-    ] = attr.ib(default=None)
+    ] = attrs.field(default=None)
 
 
 class FreeTextAdvancedExtensionPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/offset_pagination.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/offset_pagination.py
index 81c1429dc..ee54062c8 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/offset_pagination.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/offset_pagination.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -10,7 +10,7 @@
 from .request import GETOffsetPagination, POSTOffsetPagination
 
 
-@attr.s
+@attrs.define
 class OffsetPaginationExtension(ApiExtension):
     """Offset Pagination.
 
@@ -23,8 +23,8 @@ class OffsetPaginationExtension(ApiExtension):
     GET = GETOffsetPagination
     POST = POSTOffsetPagination
 
-    conformance_classes: List[str] = attr.ib(factory=list)
-    schema_href: Optional[str] = attr.ib(default=None)
+    conformance_classes: List[str] = attrs.field(factory=list)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/pagination.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/pagination.py
index 7959b0357..005ecc8aa 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/pagination.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/pagination.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -10,7 +10,7 @@
 from .request import GETPagination, POSTPagination
 
 
-@attr.s
+@attrs.define
 class PaginationExtension(ApiExtension):
     """Token Pagination.
 
@@ -23,8 +23,8 @@ class PaginationExtension(ApiExtension):
     GET = GETPagination
     POST = POSTPagination
 
-    conformance_classes: List[str] = attr.ib(factory=list)
-    schema_href: Optional[str] = attr.ib(default=None)
+    conformance_classes: List[str] = attrs.field(factory=list)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/request.py
index ffa2e3225..8ab2c0b67 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/request.py
@@ -2,7 +2,7 @@
 
 from typing import Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel
 from typing_extensions import Annotated
@@ -10,11 +10,11 @@
 from stac_fastapi.types.search import APIRequest
 
 
-@attr.s
+@attrs.define(slots=False)
 class GETTokenPagination(APIRequest):
     """Token pagination for GET requests."""
 
-    token: Annotated[Optional[str], Query()] = attr.ib(default=None)
+    token: Annotated[Optional[str], Query()] = attrs.field(default=None)
 
 
 class POSTTokenPagination(BaseModel):
@@ -23,11 +23,11 @@ class POSTTokenPagination(BaseModel):
     token: Optional[str] = None
 
 
-@attr.s
+@attrs.define(slots=False)
 class GETPagination(APIRequest):
     """Page based pagination for GET requests."""
 
-    page: Annotated[Optional[str], Query()] = attr.ib(default=None)
+    page: Annotated[Optional[str], Query()] = attrs.field(default=None)
 
 
 class POSTPagination(BaseModel):
@@ -36,11 +36,11 @@ class POSTPagination(BaseModel):
     page: Optional[str] = None
 
 
-@attr.s
+@attrs.define(slots=False)
 class GETOffsetPagination(APIRequest):
     """Offset pagination for GET requests."""
 
-    offset: Annotated[Optional[int], Query()] = attr.ib(default=None)
+    offset: Annotated[Optional[int], Query()] = attrs.field(default=None)
 
 
 class POSTOffsetPagination(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/token_pagination.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/token_pagination.py
index 11ccfb35b..945f12b99 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/token_pagination.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/pagination/token_pagination.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -10,7 +10,7 @@
 from .request import GETTokenPagination, POSTTokenPagination
 
 
-@attr.s
+@attrs.define
 class TokenPaginationExtension(ApiExtension):
     """Token Pagination.
 
@@ -23,8 +23,8 @@ class TokenPaginationExtension(ApiExtension):
     GET = GETTokenPagination
     POST = POSTTokenPagination
 
-    conformance_classes: List[str] = attr.ib(factory=list)
-    schema_href: Optional[str] = attr.ib(default=None)
+    conformance_classes: List[str] = attrs.field(factory=list)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/query/query.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/query/query.py
index 9f4c8cb0c..56b39c837 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/query/query.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/query/query.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -22,7 +22,7 @@ class QueryConformanceClasses(str, Enum):
     COLLECTIONS = "https://api.stacspec.org/v1.0.0-rc.1/collection-search#query"
 
 
-@attr.s
+@attrs.define(slots=False)
 class QueryExtension(ApiExtension):
     """Query Extension.
 
@@ -35,12 +35,12 @@ class QueryExtension(ApiExtension):
     GET = QueryExtensionGetRequest
     POST = QueryExtensionPostRequest
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         factory=lambda: [
-            QueryConformanceClasses.SEARCH,
+            QueryConformanceClasses.SEARCH.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/query/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/query/request.py
index c18e2e37d..b37dc051a 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/query/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/query/request.py
@@ -2,7 +2,7 @@
 
 from typing import Any, Dict, Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field
 from typing_extensions import Annotated
@@ -10,7 +10,7 @@
 from stac_fastapi.types.search import APIRequest
 
 
-@attr.s
+@attrs.define
 class QueryExtensionGetRequest(APIRequest):
     """Query Extension GET request model."""
 
@@ -23,7 +23,7 @@ class QueryExtensionGetRequest(APIRequest):
                 "cloudy": {"value": '{"eo:cloud_cover": {"gte": 95}}'},
             },
         ),
-    ] = attr.ib(default=None)
+    ] = attrs.field(default=None)
 
 
 class QueryExtensionPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/request.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/request.py
index fc38ab772..ecbda9142 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/request.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/request.py
@@ -2,7 +2,7 @@
 
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import Query
 from pydantic import BaseModel, Field
 from stac_pydantic.api.extensions.sort import SortExtension as PostSortModel
@@ -27,11 +27,11 @@ def _sort_converter(
     return str2list(val)
 
 
-@attr.s
+@attrs.define(slots=False)
 class SortExtensionGetRequest(APIRequest):
     """Sortby Parameter for GET requests."""
 
-    sortby: Optional[List[str]] = attr.ib(default=None, converter=_sort_converter)
+    sortby: Optional[List[str]] = attrs.field(default=None, converter=_sort_converter)
 
 
 class SortExtensionPostRequest(BaseModel):
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/sort.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/sort.py
index 77984719f..fae872754 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/sort.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/sort/sort.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 
 from stac_fastapi.types.extension import ApiExtension
@@ -23,7 +23,7 @@ class SortConformanceClasses(str, Enum):
     COLLECTIONS = "https://api.stacspec.org/v1.0.0-rc.1/collection-search#sort"
 
 
-@attr.s
+@attrs.define
 class SortExtension(ApiExtension):
     """Sort Extension.
 
@@ -35,12 +35,12 @@ class SortExtension(ApiExtension):
     GET = SortExtensionGetRequest
     POST = SortExtensionPostRequest
 
-    conformance_classes: List[str] = attr.ib(
+    conformance_classes: List[str] = attrs.field(
         factory=lambda: [
-            SortConformanceClasses.SEARCH,
+            SortConformanceClasses.SEARCH.value,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/core/transaction.py b/stac_fastapi/extensions/stac_fastapi/extensions/core/transaction.py
index 2287bc8b0..258c8424b 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/core/transaction.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/core/transaction.py
@@ -3,7 +3,7 @@
 from enum import Enum
 from typing import List, Optional, Type, Union
 
-import attr
+import attrs
 from fastapi import APIRouter, Body, FastAPI
 from stac_pydantic import Collection, Item, ItemCollection
 from stac_pydantic.shared import MimeTypes
@@ -28,28 +28,28 @@ class TransactionConformanceClasses(str, Enum):
     COLLECTIONS = "https://api.stacspec.org/v1.0.0/collections/extensions/transaction"
 
 
-@attr.s
+@attrs.define
 class PostItem(CollectionUri):
     """Create Item."""
 
-    item: Annotated[Union[Item, ItemCollection], Body()] = attr.ib(default=None)
+    item: Annotated[Union[Item, ItemCollection], Body()] = attrs.field(default=None)
 
 
-@attr.s
+@attrs.define
 class PutItem(ItemUri):
     """Update Item."""
 
-    item: Annotated[Item, Body()] = attr.ib(default=None)
+    item: Annotated[Item, Body()] = attrs.field(default=None)
 
 
-@attr.s
+@attrs.define
 class PutCollection(CollectionUri):
     """Update Collection."""
 
-    collection: Annotated[Collection, Body()] = attr.ib(default=None)
+    collection: Annotated[Collection, Body()] = attrs.field(default=None)
 
 
-@attr.s
+@attrs.define
 class TransactionExtension(ApiExtension):
     """Transaction Extension.
 
@@ -70,17 +70,17 @@ class TransactionExtension(ApiExtension):
 
     """
 
-    client: Union[AsyncBaseTransactionsClient, BaseTransactionsClient] = attr.ib()
-    settings: ApiSettings = attr.ib()
-    conformance_classes: List[str] = attr.ib(
+    client: Union[AsyncBaseTransactionsClient, BaseTransactionsClient] = attrs.field()
+    settings: ApiSettings = attrs.field()
+    conformance_classes: List[str] = attrs.field(
         factory=lambda: [
             TransactionConformanceClasses.ITEMS,
             TransactionConformanceClasses.COLLECTIONS,
         ]
     )
-    schema_href: Optional[str] = attr.ib(default=None)
-    router: APIRouter = attr.ib(factory=APIRouter)
-    response_class: Type[Response] = attr.ib(default=JSONResponse)
+    schema_href: Optional[str] = attrs.field(default=None)
+    router: APIRouter = attrs.field(factory=APIRouter)
+    response_class: Type[Response] = attrs.field(default=JSONResponse)
 
     def register_create_item(self):
         """Register create item endpoint (POST /collections/{collection_id}/items)."""
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/py.typed b/stac_fastapi/extensions/stac_fastapi/extensions/py.typed
new file mode 100644
index 000000000..e69de29bb
diff --git a/stac_fastapi/extensions/stac_fastapi/extensions/third_party/bulk_transactions.py b/stac_fastapi/extensions/stac_fastapi/extensions/third_party/bulk_transactions.py
index d1faa5c0f..16ec56121 100644
--- a/stac_fastapi/extensions/stac_fastapi/extensions/third_party/bulk_transactions.py
+++ b/stac_fastapi/extensions/stac_fastapi/extensions/third_party/bulk_transactions.py
@@ -4,7 +4,7 @@
 from enum import Enum
 from typing import Any, Dict, List, Optional, Union
 
-import attr
+import attrs
 from fastapi import APIRouter, FastAPI
 from pydantic import BaseModel
 
@@ -31,7 +31,7 @@ def __iter__(self):
         return iter(self.items.values())
 
 
-@attr.s  # type: ignore
+@attrs.define
 class BaseBulkTransactionsClient(abc.ABC):
     """BulkTransactionsClient."""
 
@@ -63,7 +63,7 @@ def bulk_item_insert(
         raise NotImplementedError
 
 
-@attr.s  # type: ignore
+@attrs.define
 class AsyncBaseBulkTransactionsClient(abc.ABC):
     """BulkTransactionsClient."""
 
@@ -84,7 +84,7 @@ async def bulk_item_insert(
         raise NotImplementedError
 
 
-@attr.s
+@attrs.define
 class BulkTransactionExtension(ApiExtension):
     """Bulk Transaction Extension.
 
@@ -110,9 +110,11 @@ class BulkTransactionExtension(ApiExtension):
         }
     """
 
-    client: Union[AsyncBaseBulkTransactionsClient, BaseBulkTransactionsClient] = attr.ib()
-    conformance_classes: List[str] = attr.ib(default=list())
-    schema_href: Optional[str] = attr.ib(default=None)
+    client: Union[
+        AsyncBaseBulkTransactionsClient, BaseBulkTransactionsClient
+    ] = attrs.field()
+    conformance_classes: List[str] = attrs.field(default=list())
+    schema_href: Optional[str] = attrs.field(default=None)
 
     def register(self, app: FastAPI) -> None:
         """Register the extension with a FastAPI application.
diff --git a/stac_fastapi/extensions/tests/test_collection_search.py b/stac_fastapi/extensions/tests/test_collection_search.py
index 50fa79be7..cb378467d 100644
--- a/stac_fastapi/extensions/tests/test_collection_search.py
+++ b/stac_fastapi/extensions/tests/test_collection_search.py
@@ -2,7 +2,7 @@
 from datetime import datetime, timezone
 from urllib.parse import quote_plus
 
-import attr
+import attrs
 import pytest
 from starlette.testclient import TestClient
 
@@ -80,7 +80,7 @@ def item_collection(self, *args, **kwargs):
         raise NotImplementedError
 
 
-@attr.s
+@attrs.define
 class DummyPostClient(BaseCollectionSearchClient):
     def post_all_collections(
         self, search_request: BaseCollectionSearchPostRequest, **kwargs
diff --git a/stac_fastapi/extensions/tests/test_pagination.py b/stac_fastapi/extensions/tests/test_pagination.py
index ba1d5b31c..9c549a7d9 100644
--- a/stac_fastapi/extensions/tests/test_pagination.py
+++ b/stac_fastapi/extensions/tests/test_pagination.py
@@ -45,38 +45,37 @@ def item_collection(self, *args, **kwargs):
         return args, kwargs
 
 
-collections_get_request_model = create_request_model(
-    model_name="CollectionsGetRequest",
-    base_model=EmptyRequest,
-    mixins=[
-        OffsetPaginationExtension().GET,
-    ],
-    request_type="GET",
-)
-
-items_get_request_model = create_request_model(
-    model_name="ItemsGetRequest",
-    base_model=EmptyRequest,
-    mixins=[
-        PaginationExtension().GET,
-    ],
-    request_type="GET",
-)
-
-search_get_request_model = create_request_model(
-    model_name="SearchGetRequest",
-    base_model=BaseSearchGetRequest,
-    mixins=[
-        TokenPaginationExtension().GET,
-    ],
-    request_type="GET",
-)
-
-
 @pytest.fixture
 def client() -> Iterator[TestClient]:
     settings = ApiSettings()
 
+    collections_get_request_model = create_request_model(
+        model_name="CollectionsGetRequest",
+        base_model=EmptyRequest,
+        mixins=[
+            OffsetPaginationExtension().GET,
+        ],
+        request_type="GET",
+    )
+
+    items_get_request_model = create_request_model(
+        model_name="ItemsGetRequest",
+        base_model=EmptyRequest,
+        mixins=[
+            PaginationExtension().GET,
+        ],
+        request_type="GET",
+    )
+
+    search_get_request_model = create_request_model(
+        model_name="SearchGetRequest",
+        base_model=BaseSearchGetRequest,
+        mixins=[
+            TokenPaginationExtension().GET,
+        ],
+        request_type="GET",
+    )
+
     api = StacApi(
         settings=settings,
         client=DummyCoreClient(),
diff --git a/stac_fastapi/types/stac_fastapi/types/core.py b/stac_fastapi/types/stac_fastapi/types/core.py
index f90b72823..731a6adf0 100644
--- a/stac_fastapi/types/stac_fastapi/types/core.py
+++ b/stac_fastapi/types/stac_fastapi/types/core.py
@@ -4,7 +4,7 @@
 from typing import Any, Dict, List, Optional, Union
 from urllib.parse import urljoin
 
-import attr
+import attrs
 from fastapi import Request
 from geojson_pydantic.geometries import Geometry
 from stac_pydantic import Collection, Item, ItemCollection
@@ -13,12 +13,12 @@
 from stac_pydantic.version import STAC_VERSION
 from starlette.responses import Response
 
-from stac_fastapi.types import stac
-from stac_fastapi.types.config import ApiSettings
-from stac_fastapi.types.conformance import BASE_CONFORMANCE_CLASSES
-from stac_fastapi.types.extension import ApiExtension
-from stac_fastapi.types.requests import get_base_url
-from stac_fastapi.types.search import BaseSearchPostRequest
+from . import stac
+from .config import ApiSettings
+from .conformance import BASE_CONFORMANCE_CLASSES
+from .extension import ApiExtension
+from .requests import get_base_url
+from .search import BaseSearchPostRequest
 
 __all__ = [
     "NumType",
@@ -36,7 +36,7 @@
 api_settings = ApiSettings()
 
 
-@attr.s  # type:ignore
+@attrs.define  # type:ignore
 class BaseTransactionsClient(abc.ABC):
     """Defines a pattern for implementing the STAC API Transaction Extension."""
 
@@ -150,7 +150,7 @@ def delete_collection(
         ...
 
 
-@attr.s  # type:ignore
+@attrs.define  # type:ignore
 class AsyncBaseTransactionsClient(abc.ABC):
     """Defines a pattern for implementing the STAC transaction extension."""
 
@@ -263,14 +263,14 @@ async def delete_collection(
         ...
 
 
-@attr.s
+@attrs.define
 class LandingPageMixin(abc.ABC):
     """Create a STAC landing page (GET /)."""
 
-    stac_version: str = attr.ib(default=STAC_VERSION)
-    landing_page_id: str = attr.ib(default=api_settings.stac_fastapi_landing_id)
-    title: str = attr.ib(default=api_settings.stac_fastapi_title)
-    description: str = attr.ib(default=api_settings.stac_fastapi_description)
+    stac_version: str = attrs.field(default=STAC_VERSION)
+    landing_page_id: str = attrs.field(default=api_settings.stac_fastapi_landing_id)
+    title: str = attrs.field(default=api_settings.stac_fastapi_title)
+    description: str = attrs.field(default=api_settings.stac_fastapi_description)
 
     def _landing_page(
         self,
@@ -331,7 +331,7 @@ def _landing_page(
         return landing_page
 
 
-@attr.s  # type:ignore
+@attrs.define  # type:ignore
 class BaseCoreClient(LandingPageMixin, abc.ABC):
     """Defines a pattern for implementing STAC api core endpoints.
 
@@ -339,10 +339,10 @@ class BaseCoreClient(LandingPageMixin, abc.ABC):
         extensions: list of registered api extensions.
     """
 
-    base_conformance_classes: List[str] = attr.ib(
+    base_conformance_classes: List[str] = attrs.field(
         factory=lambda: BASE_CONFORMANCE_CLASSES
     )
-    extensions: List[ApiExtension] = attr.ib(default=attr.Factory(list))
+    extensions: List[ApiExtension] = attrs.field(default=attrs.Factory(list))
 
     def conformance_classes(self) -> List[str]:
         """Generate conformance classes by adding extension conformance to base
@@ -551,7 +551,7 @@ def item_collection(
         ...
 
 
-@attr.s  # type:ignore
+@attrs.define  # type:ignore
 class AsyncBaseCoreClient(LandingPageMixin, abc.ABC):
     """Defines a pattern for implementing STAC api core endpoints.
 
@@ -559,10 +559,10 @@ class AsyncBaseCoreClient(LandingPageMixin, abc.ABC):
         extensions: list of registered api extensions.
     """
 
-    base_conformance_classes: List[str] = attr.ib(
+    base_conformance_classes: List[str] = attrs.field(
         factory=lambda: BASE_CONFORMANCE_CLASSES
     )
-    extensions: List[ApiExtension] = attr.ib(default=attr.Factory(list))
+    extensions: List[ApiExtension] = attrs.field(default=attrs.Factory(list))
 
     def conformance_classes(self) -> List[str]:
         """Generate conformance classes by adding extension conformance to base
diff --git a/stac_fastapi/types/stac_fastapi/types/extension.py b/stac_fastapi/types/stac_fastapi/types/extension.py
index 22fed6068..0f4bcd863 100644
--- a/stac_fastapi/types/stac_fastapi/types/extension.py
+++ b/stac_fastapi/types/stac_fastapi/types/extension.py
@@ -3,12 +3,12 @@
 import abc
 from typing import List, Optional
 
-import attr
+import attrs
 from fastapi import FastAPI
 from pydantic import BaseModel
 
 
-@attr.s
+@attrs.define
 class ApiExtension(abc.ABC):
     """Abstract base class for defining API extensions."""
 
@@ -22,8 +22,8 @@ def get_request_model(self, verb: str = "GET") -> Optional[BaseModel]:
         """
         return getattr(self, verb)
 
-    conformance_classes: List[str] = attr.ib(factory=list)
-    schema_href: Optional[str] = attr.ib(default=None)
+    conformance_classes: List[str] = attrs.field(factory=list)
+    schema_href: Optional[str] = attrs.field(default=None)
 
     @abc.abstractmethod
     def register(self, app: FastAPI) -> None:
diff --git a/stac_fastapi/types/stac_fastapi/types/links.py b/stac_fastapi/types/stac_fastapi/types/links.py
index 28f05d6c0..7af4563a5 100644
--- a/stac_fastapi/types/stac_fastapi/types/links.py
+++ b/stac_fastapi/types/stac_fastapi/types/links.py
@@ -3,7 +3,7 @@
 from typing import Any, Dict, List
 from urllib.parse import urljoin
 
-import attr
+import attrs
 from stac_pydantic.links import Relations
 from stac_pydantic.shared import MimeTypes
 
@@ -26,19 +26,19 @@ def resolve_links(links: list, base_url: str) -> List[Dict]:
     return filtered_links
 
 
-@attr.s
+@attrs.define
 class BaseLinks:
     """Create inferred links common to collections and items."""
 
-    collection_id: str = attr.ib()
-    base_url: str = attr.ib()
+    collection_id: str = attrs.field()
+    base_url: str = attrs.field()
 
     def root(self) -> Dict[str, Any]:
         """Return the catalog root."""
         return dict(rel=Relations.root, type=MimeTypes.json, href=self.base_url)
 
 
-@attr.s
+@attrs.define
 class CollectionLinks(BaseLinks):
     """Create inferred links specific to collections."""
 
@@ -67,11 +67,11 @@ def create_links(self) -> List[Dict[str, Any]]:
         return [self.self(), self.parent(), self.items(), self.root()]
 
 
-@attr.s
+@attrs.define
 class ItemLinks(BaseLinks):
     """Create inferred links specific to items."""
 
-    item_id: str = attr.ib()
+    item_id: str = attrs.field()
 
     def self(self) -> Dict[str, Any]:
         """Create the `self` link."""
diff --git a/stac_fastapi/types/stac_fastapi/types/py.typed b/stac_fastapi/types/stac_fastapi/types/py.typed
new file mode 100644
index 000000000..e69de29bb
diff --git a/stac_fastapi/types/stac_fastapi/types/search.py b/stac_fastapi/types/stac_fastapi/types/search.py
index 01e622738..4bf9f1850 100644
--- a/stac_fastapi/types/stac_fastapi/types/search.py
+++ b/stac_fastapi/types/stac_fastapi/types/search.py
@@ -4,7 +4,7 @@
 from datetime import datetime as dt
 from typing import Dict, List, Optional, Union
 
-import attr
+import attrs
 from fastapi import HTTPException, Query
 from pydantic import Field, PositiveInt
 from pydantic.functional_validators import AfterValidator
@@ -12,7 +12,7 @@
 from stac_pydantic.shared import BBox
 from typing_extensions import Annotated
 
-from stac_fastapi.types.rfc3339 import DateTimeType, str_to_interval
+from .rfc3339 import DateTimeType, str_to_interval
 
 
 def crop(v: PositiveInt) -> PositiveInt:
@@ -128,21 +128,21 @@ def _validate_datetime(instance, attribute, value):
 ]
 
 
-@attr.s
+@attrs.define(slots=False)
 class APIRequest:
     """Generic API Request base class."""
 
     def kwargs(self) -> Dict:
         """Transform api request params into format which matches the signature of the
         endpoint."""
-        return self.__dict__
+        return attrs.asdict(self)
 
 
-@attr.s
+@attrs.define(slots=False)
 class DatetimeMixin:
     """Datetime Mixin."""
 
-    datetime: DateTimeQueryType = attr.ib(default=None, validator=_validate_datetime)
+    datetime: DateTimeQueryType = attrs.field(default=None, validator=_validate_datetime)
 
     def parse_datetime(self) -> Optional[DateTimeType]:
         """Return Datetime objects."""
@@ -167,15 +167,15 @@ def end_date(self) -> Optional[dt]:
         return parsed[1] if isinstance(parsed, tuple) else None
 
 
-@attr.s
+@attrs.define(slots=False)
 class BaseSearchGetRequest(APIRequest, DatetimeMixin):
     """Base arguments for GET Request."""
 
-    collections: Optional[List[str]] = attr.ib(
+    collections: Optional[List[str]] = attrs.field(
         default=None, converter=_collection_converter
     )
-    ids: Optional[List[str]] = attr.ib(default=None, converter=_ids_converter)
-    bbox: Optional[BBox] = attr.ib(default=None, converter=_bbox_converter)
+    ids: Optional[List[str]] = attrs.field(default=None, converter=_ids_converter)
+    bbox: Optional[BBox] = attrs.field(default=None, converter=_bbox_converter)
     intersects: Annotated[
         Optional[str],
         Query(
@@ -221,14 +221,14 @@ class BaseSearchGetRequest(APIRequest, DatetimeMixin):
                 },
             },
         ),
-    ] = attr.ib(default=None)
-    datetime: DateTimeQueryType = attr.ib(default=None, validator=_validate_datetime)
+    ] = attrs.field(default=None)
+    datetime: DateTimeQueryType = attrs.field(default=None, validator=_validate_datetime)
     limit: Annotated[
         Optional[Limit],
         Query(
             description="Limits the number of results that are included in each page of the response (capped to 10_000)."  # noqa: E501
         ),
-    ] = attr.ib(default=10)
+    ] = attrs.field(default=10)
 
 
 class BaseSearchPostRequest(Search):
diff --git a/stac_fastapi/types/tests/test_limit.py b/stac_fastapi/types/tests/test_limit.py
index d4c03f33e..5e5419c86 100644
--- a/stac_fastapi/types/tests/test_limit.py
+++ b/stac_fastapi/types/tests/test_limit.py
@@ -1,4 +1,5 @@
 import pytest
+from attrs import asdict
 from fastapi import Depends, FastAPI
 from fastapi.testclient import TestClient
 from pydantic import ValidationError
@@ -31,7 +32,7 @@ def test_limit_get_request():
 
     @app.get("/test")
     def route(model=Depends(BaseSearchGetRequest)):
-        return model
+        return asdict(model)
 
     with TestClient(app) as client:
         resp = client.get(