diff --git a/README.md b/README.md
index 9981e1b9..7a599b1c 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ It is generated with [Stainless](https://www.stainlessapi.com/).
 
 ## Documentation
 
-The REST API documentation can be found on [docs.brainbase.com](https://docs.brainbase.com). The full API of this library can be found in [api.md](api.md).
+The REST API documentation can be found on [docs.usebrainbase.com](https://docs.usebrainbase.com). The full API of this library can be found in [api.md](api.md).
 
 ## Installation
 
@@ -24,25 +24,32 @@ pip install --pre brainbase-labs
 The full API of this library can be found in [api.md](api.md).
 
 ```python
+import os
 from brainbase import Brainbase
 
 client = Brainbase(
-    bearer_token="My Bearer Token",
+    api_key=os.environ.get("BRAINBASE_API_KEY"),  # This is the default and can be omitted
 )
 
 client.workers.list()
 ```
 
+While you can provide an `api_key` keyword argument,
+we recommend using [python-dotenv](https://pypi.org/project/python-dotenv/)
+to add `BRAINBASE_API_KEY="My API Key"` to your `.env` file
+so that your API Key is not stored in source control.
+
 ## Async usage
 
 Simply import `AsyncBrainbase` instead of `Brainbase` and use `await` with each API call:
 
 ```python
+import os
 import asyncio
 from brainbase import AsyncBrainbase
 
 client = AsyncBrainbase(
-    bearer_token="My Bearer Token",
+    api_key=os.environ.get("BRAINBASE_API_KEY"),  # This is the default and can be omitted
 )
 
 
@@ -77,9 +84,7 @@ All errors inherit from `brainbase.APIError`.
 import brainbase
 from brainbase import Brainbase
 
-client = Brainbase(
-    bearer_token="My Bearer Token",
-)
+client = Brainbase()
 
 try:
     client.workers.list()
@@ -122,7 +127,6 @@ from brainbase import Brainbase
 client = Brainbase(
     # default is 2
     max_retries=0,
-    bearer_token="My Bearer Token",
 )
 
 # Or, configure per-request:
@@ -141,13 +145,11 @@ from brainbase import Brainbase
 client = Brainbase(
     # 20 seconds (default is 1 minute)
     timeout=20.0,
-    bearer_token="My Bearer Token",
 )
 
 # More granular control:
 client = Brainbase(
     timeout=httpx.Timeout(60.0, read=5.0, write=10.0, connect=2.0),
-    bearer_token="My Bearer Token",
 )
 
 # Override per-request:
@@ -191,9 +193,7 @@ The "raw" Response object can be accessed by prefixing `.with_raw_response.` to
 ```py
 from brainbase import Brainbase
 
-client = Brainbase(
-    bearer_token="My Bearer Token",
-)
+client = Brainbase()
 response = client.workers.with_raw_response.list()
 print(response.headers.get('X-My-Header'))
 
@@ -274,7 +274,6 @@ client = Brainbase(
         proxy="http://my.test.proxy.example.com",
         transport=httpx.HTTPTransport(local_address="0.0.0.0"),
     ),
-    bearer_token="My Bearer Token",
 )
 ```
 
@@ -291,9 +290,7 @@ By default the library closes underlying HTTP connections whenever the client is
 ```py
 from brainbase import Brainbase
 
-with Brainbase(
-    bearer_token="My Bearer Token",
-) as client:
+with Brainbase() as client:
   # make requests here
   ...
 
diff --git a/src/brainbase/_client.py b/src/brainbase/_client.py
index 3c4f9565..9192a946 100644
--- a/src/brainbase/_client.py
+++ b/src/brainbase/_client.py
@@ -51,12 +51,12 @@ class Brainbase(SyncAPIClient):
     with_streaming_response: BrainbaseWithStreamedResponse
 
     # client options
-    bearer_token: str
+    api_key: str
 
     def __init__(
         self,
         *,
-        bearer_token: str | None = None,
+        api_key: str | None = None,
         base_url: str | httpx.URL | None = None,
         timeout: Union[float, Timeout, None, NotGiven] = NOT_GIVEN,
         max_retries: int = DEFAULT_MAX_RETRIES,
@@ -78,15 +78,15 @@ def __init__(
     ) -> None:
         """Construct a new synchronous brainbase client instance.
 
-        This automatically infers the `bearer_token` argument from the `BEARER_TOKEN` environment variable if it is not provided.
+        This automatically infers the `api_key` argument from the `BRAINBASE_API_KEY` environment variable if it is not provided.
         """
-        if bearer_token is None:
-            bearer_token = os.environ.get("BEARER_TOKEN")
-        if bearer_token is None:
+        if api_key is None:
+            api_key = os.environ.get("BRAINBASE_API_KEY")
+        if api_key is None:
             raise BrainbaseError(
-                "The bearer_token client option must be set either by passing bearer_token to the client or by setting the BEARER_TOKEN environment variable"
+                "The api_key client option must be set either by passing api_key to the client or by setting the BRAINBASE_API_KEY environment variable"
             )
-        self.bearer_token = bearer_token
+        self.api_key = api_key
 
         if base_url is None:
             base_url = os.environ.get("BRAINBASE_BASE_URL")
@@ -113,6 +113,12 @@ def __init__(
     def qs(self) -> Querystring:
         return Querystring(array_format="comma")
 
+    @property
+    @override
+    def auth_headers(self) -> dict[str, str]:
+        api_key = self.api_key
+        return {"x-api-key": api_key}
+
     @property
     @override
     def default_headers(self) -> dict[str, str | Omit]:
@@ -125,7 +131,7 @@ def default_headers(self) -> dict[str, str | Omit]:
     def copy(
         self,
         *,
-        bearer_token: str | None = None,
+        api_key: str | None = None,
         base_url: str | httpx.URL | None = None,
         timeout: float | Timeout | None | NotGiven = NOT_GIVEN,
         http_client: httpx.Client | None = None,
@@ -159,7 +165,7 @@ def copy(
 
         http_client = http_client or self._client
         return self.__class__(
-            bearer_token=bearer_token or self.bearer_token,
+            api_key=api_key or self.api_key,
             base_url=base_url or self.base_url,
             timeout=self.timeout if isinstance(timeout, NotGiven) else timeout,
             http_client=http_client,
@@ -213,12 +219,12 @@ class AsyncBrainbase(AsyncAPIClient):
     with_streaming_response: AsyncBrainbaseWithStreamedResponse
 
     # client options
-    bearer_token: str
+    api_key: str
 
     def __init__(
         self,
         *,
-        bearer_token: str | None = None,
+        api_key: str | None = None,
         base_url: str | httpx.URL | None = None,
         timeout: Union[float, Timeout, None, NotGiven] = NOT_GIVEN,
         max_retries: int = DEFAULT_MAX_RETRIES,
@@ -240,15 +246,15 @@ def __init__(
     ) -> None:
         """Construct a new async brainbase client instance.
 
-        This automatically infers the `bearer_token` argument from the `BEARER_TOKEN` environment variable if it is not provided.
+        This automatically infers the `api_key` argument from the `BRAINBASE_API_KEY` environment variable if it is not provided.
         """
-        if bearer_token is None:
-            bearer_token = os.environ.get("BEARER_TOKEN")
-        if bearer_token is None:
+        if api_key is None:
+            api_key = os.environ.get("BRAINBASE_API_KEY")
+        if api_key is None:
             raise BrainbaseError(
-                "The bearer_token client option must be set either by passing bearer_token to the client or by setting the BEARER_TOKEN environment variable"
+                "The api_key client option must be set either by passing api_key to the client or by setting the BRAINBASE_API_KEY environment variable"
             )
-        self.bearer_token = bearer_token
+        self.api_key = api_key
 
         if base_url is None:
             base_url = os.environ.get("BRAINBASE_BASE_URL")
@@ -275,6 +281,12 @@ def __init__(
     def qs(self) -> Querystring:
         return Querystring(array_format="comma")
 
+    @property
+    @override
+    def auth_headers(self) -> dict[str, str]:
+        api_key = self.api_key
+        return {"x-api-key": api_key}
+
     @property
     @override
     def default_headers(self) -> dict[str, str | Omit]:
@@ -287,7 +299,7 @@ def default_headers(self) -> dict[str, str | Omit]:
     def copy(
         self,
         *,
-        bearer_token: str | None = None,
+        api_key: str | None = None,
         base_url: str | httpx.URL | None = None,
         timeout: float | Timeout | None | NotGiven = NOT_GIVEN,
         http_client: httpx.AsyncClient | None = None,
@@ -321,7 +333,7 @@ def copy(
 
         http_client = http_client or self._client
         return self.__class__(
-            bearer_token=bearer_token or self.bearer_token,
+            api_key=api_key or self.api_key,
             base_url=base_url or self.base_url,
             timeout=self.timeout if isinstance(timeout, NotGiven) else timeout,
             http_client=http_client,
diff --git a/tests/conftest.py b/tests/conftest.py
index 9a8b7c7c..8e89d982 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -28,7 +28,7 @@ def pytest_collection_modifyitems(items: list[pytest.Function]) -> None:
 
 base_url = os.environ.get("TEST_API_BASE_URL", "http://127.0.0.1:4010")
 
-bearer_token = "My Bearer Token"
+api_key = "My API Key"
 
 
 @pytest.fixture(scope="session")
@@ -37,7 +37,7 @@ def client(request: FixtureRequest) -> Iterator[Brainbase]:
     if not isinstance(strict, bool):
         raise TypeError(f"Unexpected fixture parameter type {type(strict)}, expected {bool}")
 
-    with Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=strict) as client:
+    with Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=strict) as client:
         yield client
 
 
@@ -47,7 +47,5 @@ async def async_client(request: FixtureRequest) -> AsyncIterator[AsyncBrainbase]
     if not isinstance(strict, bool):
         raise TypeError(f"Unexpected fixture parameter type {type(strict)}, expected {bool}")
 
-    async with AsyncBrainbase(
-        base_url=base_url, bearer_token=bearer_token, _strict_response_validation=strict
-    ) as client:
+    async with AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=strict) as client:
         yield client
diff --git a/tests/test_client.py b/tests/test_client.py
index fa4581c7..4bf71630 100644
--- a/tests/test_client.py
+++ b/tests/test_client.py
@@ -25,7 +25,7 @@
 from brainbase._types import Omit
 from brainbase._models import BaseModel, FinalRequestOptions
 from brainbase._constants import RAW_RESPONSE_HEADER
-from brainbase._exceptions import APIStatusError, APITimeoutError, APIResponseValidationError
+from brainbase._exceptions import APIStatusError, BrainbaseError, APITimeoutError, APIResponseValidationError
 from brainbase._base_client import (
     DEFAULT_TIMEOUT,
     HTTPX_DEFAULT_TIMEOUT,
@@ -36,7 +36,7 @@
 from .utils import update_env
 
 base_url = os.environ.get("TEST_API_BASE_URL", "http://127.0.0.1:4010")
-bearer_token = "My Bearer Token"
+api_key = "My API Key"
 
 
 def _get_params(client: BaseClient[Any, Any]) -> dict[str, str]:
@@ -58,7 +58,7 @@ def _get_open_connections(client: Brainbase | AsyncBrainbase) -> int:
 
 
 class TestBrainbase:
-    client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+    client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
     @pytest.mark.respx(base_url=base_url)
     def test_raw_response(self, respx_mock: MockRouter) -> None:
@@ -84,9 +84,9 @@ def test_copy(self) -> None:
         copied = self.client.copy()
         assert id(copied) != id(self.client)
 
-        copied = self.client.copy(bearer_token="another My Bearer Token")
-        assert copied.bearer_token == "another My Bearer Token"
-        assert self.client.bearer_token == "My Bearer Token"
+        copied = self.client.copy(api_key="another My API Key")
+        assert copied.api_key == "another My API Key"
+        assert self.client.api_key == "My API Key"
 
     def test_copy_default_options(self) -> None:
         # options that have a default are overridden correctly
@@ -106,10 +106,7 @@ def test_copy_default_options(self) -> None:
 
     def test_copy_default_headers(self) -> None:
         client = Brainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_headers={"X-Foo": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_headers={"X-Foo": "bar"}
         )
         assert client.default_headers["X-Foo"] == "bar"
 
@@ -143,7 +140,7 @@ def test_copy_default_headers(self) -> None:
 
     def test_copy_default_query(self) -> None:
         client = Brainbase(
-            base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, default_query={"foo": "bar"}
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_query={"foo": "bar"}
         )
         assert _get_params(client)["foo"] == "bar"
 
@@ -268,7 +265,7 @@ def test_request_timeout(self) -> None:
 
     def test_client_timeout_option(self) -> None:
         client = Brainbase(
-            base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, timeout=httpx.Timeout(0)
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, timeout=httpx.Timeout(0)
         )
 
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -279,7 +276,7 @@ def test_http_client_timeout_option(self) -> None:
         # custom timeout given to the httpx client should be used
         with httpx.Client(timeout=None) as http_client:
             client = Brainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -289,7 +286,7 @@ def test_http_client_timeout_option(self) -> None:
         # no timeout given to the httpx client should not use the httpx default
         with httpx.Client() as http_client:
             client = Brainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -299,7 +296,7 @@ def test_http_client_timeout_option(self) -> None:
         # explicitly passing the default timeout currently results in it being ignored
         with httpx.Client(timeout=HTTPX_DEFAULT_TIMEOUT) as http_client:
             client = Brainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -311,17 +308,14 @@ async def test_invalid_http_client(self) -> None:
             async with httpx.AsyncClient() as http_client:
                 Brainbase(
                     base_url=base_url,
-                    bearer_token=bearer_token,
+                    api_key=api_key,
                     _strict_response_validation=True,
                     http_client=cast(Any, http_client),
                 )
 
     def test_default_headers_option(self) -> None:
         client = Brainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_headers={"X-Foo": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_headers={"X-Foo": "bar"}
         )
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
         assert request.headers.get("x-foo") == "bar"
@@ -329,7 +323,7 @@ def test_default_headers_option(self) -> None:
 
         client2 = Brainbase(
             base_url=base_url,
-            bearer_token=bearer_token,
+            api_key=api_key,
             _strict_response_validation=True,
             default_headers={
                 "X-Foo": "stainless",
@@ -340,12 +334,19 @@ def test_default_headers_option(self) -> None:
         assert request.headers.get("x-foo") == "stainless"
         assert request.headers.get("x-stainless-lang") == "my-overriding-header"
 
+    def test_validate_headers(self) -> None:
+        client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
+        request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
+        assert request.headers.get("x-api-key") == api_key
+
+        with pytest.raises(BrainbaseError):
+            with update_env(**{"BRAINBASE_API_KEY": Omit()}):
+                client2 = Brainbase(base_url=base_url, api_key=None, _strict_response_validation=True)
+            _ = client2
+
     def test_default_query_option(self) -> None:
         client = Brainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_query={"query_param": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_query={"query_param": "bar"}
         )
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
         url = httpx.URL(request.url)
@@ -545,9 +546,7 @@ class Model(BaseModel):
         assert response.foo == 2
 
     def test_base_url_setter(self) -> None:
-        client = Brainbase(
-            base_url="https://example.com/from_init", bearer_token=bearer_token, _strict_response_validation=True
-        )
+        client = Brainbase(base_url="https://example.com/from_init", api_key=api_key, _strict_response_validation=True)
         assert client.base_url == "https://example.com/from_init/"
 
         client.base_url = "https://example.com/from_setter"  # type: ignore[assignment]
@@ -556,20 +555,16 @@ def test_base_url_setter(self) -> None:
 
     def test_base_url_env(self) -> None:
         with update_env(BRAINBASE_BASE_URL="http://localhost:5000/from/env"):
-            client = Brainbase(bearer_token=bearer_token, _strict_response_validation=True)
+            client = Brainbase(api_key=api_key, _strict_response_validation=True)
             assert client.base_url == "http://localhost:5000/from/env/"
 
     @pytest.mark.parametrize(
         "client",
         [
+            Brainbase(base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True),
             Brainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
-            ),
-            Brainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.Client(),
             ),
@@ -589,14 +584,10 @@ def test_base_url_trailing_slash(self, client: Brainbase) -> None:
     @pytest.mark.parametrize(
         "client",
         [
+            Brainbase(base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True),
             Brainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
-            ),
-            Brainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.Client(),
             ),
@@ -616,14 +607,10 @@ def test_base_url_no_trailing_slash(self, client: Brainbase) -> None:
     @pytest.mark.parametrize(
         "client",
         [
+            Brainbase(base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True),
             Brainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
-            ),
-            Brainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.Client(),
             ),
@@ -641,7 +628,7 @@ def test_absolute_request_url(self, client: Brainbase) -> None:
         assert request.url == "https://myapi.com/foo"
 
     def test_copied_client_does_not_close_http(self) -> None:
-        client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
         assert not client.is_closed()
 
         copied = client.copy()
@@ -652,7 +639,7 @@ def test_copied_client_does_not_close_http(self) -> None:
         assert not client.is_closed()
 
     def test_client_context_manager(self) -> None:
-        client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
         with client as c2:
             assert c2 is client
             assert not c2.is_closed()
@@ -673,12 +660,7 @@ class Model(BaseModel):
 
     def test_client_max_retries_validation(self) -> None:
         with pytest.raises(TypeError, match=r"max_retries cannot be None"):
-            Brainbase(
-                base_url=base_url,
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
-                max_retries=cast(Any, None),
-            )
+            Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True, max_retries=cast(Any, None))
 
     @pytest.mark.respx(base_url=base_url)
     def test_received_text_for_expected_json(self, respx_mock: MockRouter) -> None:
@@ -687,12 +669,12 @@ class Model(BaseModel):
 
         respx_mock.get("/foo").mock(return_value=httpx.Response(200, text="my-custom-format"))
 
-        strict_client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        strict_client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
         with pytest.raises(APIResponseValidationError):
             strict_client.get("/foo", cast_to=Model)
 
-        client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=False)
+        client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=False)
 
         response = client.get("/foo", cast_to=Model)
         assert isinstance(response, str)  # type: ignore[unreachable]
@@ -720,7 +702,7 @@ class Model(BaseModel):
     )
     @mock.patch("time.time", mock.MagicMock(return_value=1696004797))
     def test_parse_retry_after_header(self, remaining_retries: int, retry_after: str, timeout: float) -> None:
-        client = Brainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = Brainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
         headers = httpx.Headers({"retry-after": retry_after})
         options = FinalRequestOptions(method="get", url="/foo", max_retries=3)
@@ -830,7 +812,7 @@ def retry_handler(_request: httpx.Request) -> httpx.Response:
 
 
 class TestAsyncBrainbase:
-    client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+    client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
     @pytest.mark.respx(base_url=base_url)
     @pytest.mark.asyncio
@@ -858,9 +840,9 @@ def test_copy(self) -> None:
         copied = self.client.copy()
         assert id(copied) != id(self.client)
 
-        copied = self.client.copy(bearer_token="another My Bearer Token")
-        assert copied.bearer_token == "another My Bearer Token"
-        assert self.client.bearer_token == "My Bearer Token"
+        copied = self.client.copy(api_key="another My API Key")
+        assert copied.api_key == "another My API Key"
+        assert self.client.api_key == "My API Key"
 
     def test_copy_default_options(self) -> None:
         # options that have a default are overridden correctly
@@ -880,10 +862,7 @@ def test_copy_default_options(self) -> None:
 
     def test_copy_default_headers(self) -> None:
         client = AsyncBrainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_headers={"X-Foo": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_headers={"X-Foo": "bar"}
         )
         assert client.default_headers["X-Foo"] == "bar"
 
@@ -917,7 +896,7 @@ def test_copy_default_headers(self) -> None:
 
     def test_copy_default_query(self) -> None:
         client = AsyncBrainbase(
-            base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, default_query={"foo": "bar"}
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_query={"foo": "bar"}
         )
         assert _get_params(client)["foo"] == "bar"
 
@@ -1042,7 +1021,7 @@ async def test_request_timeout(self) -> None:
 
     async def test_client_timeout_option(self) -> None:
         client = AsyncBrainbase(
-            base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, timeout=httpx.Timeout(0)
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, timeout=httpx.Timeout(0)
         )
 
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -1053,7 +1032,7 @@ async def test_http_client_timeout_option(self) -> None:
         # custom timeout given to the httpx client should be used
         async with httpx.AsyncClient(timeout=None) as http_client:
             client = AsyncBrainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -1063,7 +1042,7 @@ async def test_http_client_timeout_option(self) -> None:
         # no timeout given to the httpx client should not use the httpx default
         async with httpx.AsyncClient() as http_client:
             client = AsyncBrainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -1073,7 +1052,7 @@ async def test_http_client_timeout_option(self) -> None:
         # explicitly passing the default timeout currently results in it being ignored
         async with httpx.AsyncClient(timeout=HTTPX_DEFAULT_TIMEOUT) as http_client:
             client = AsyncBrainbase(
-                base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True, http_client=http_client
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, http_client=http_client
             )
 
             request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
@@ -1085,17 +1064,14 @@ def test_invalid_http_client(self) -> None:
             with httpx.Client() as http_client:
                 AsyncBrainbase(
                     base_url=base_url,
-                    bearer_token=bearer_token,
+                    api_key=api_key,
                     _strict_response_validation=True,
                     http_client=cast(Any, http_client),
                 )
 
     def test_default_headers_option(self) -> None:
         client = AsyncBrainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_headers={"X-Foo": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_headers={"X-Foo": "bar"}
         )
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
         assert request.headers.get("x-foo") == "bar"
@@ -1103,7 +1079,7 @@ def test_default_headers_option(self) -> None:
 
         client2 = AsyncBrainbase(
             base_url=base_url,
-            bearer_token=bearer_token,
+            api_key=api_key,
             _strict_response_validation=True,
             default_headers={
                 "X-Foo": "stainless",
@@ -1114,12 +1090,19 @@ def test_default_headers_option(self) -> None:
         assert request.headers.get("x-foo") == "stainless"
         assert request.headers.get("x-stainless-lang") == "my-overriding-header"
 
+    def test_validate_headers(self) -> None:
+        client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
+        request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
+        assert request.headers.get("x-api-key") == api_key
+
+        with pytest.raises(BrainbaseError):
+            with update_env(**{"BRAINBASE_API_KEY": Omit()}):
+                client2 = AsyncBrainbase(base_url=base_url, api_key=None, _strict_response_validation=True)
+            _ = client2
+
     def test_default_query_option(self) -> None:
         client = AsyncBrainbase(
-            base_url=base_url,
-            bearer_token=bearer_token,
-            _strict_response_validation=True,
-            default_query={"query_param": "bar"},
+            base_url=base_url, api_key=api_key, _strict_response_validation=True, default_query={"query_param": "bar"}
         )
         request = client._build_request(FinalRequestOptions(method="get", url="/foo"))
         url = httpx.URL(request.url)
@@ -1320,7 +1303,7 @@ class Model(BaseModel):
 
     def test_base_url_setter(self) -> None:
         client = AsyncBrainbase(
-            base_url="https://example.com/from_init", bearer_token=bearer_token, _strict_response_validation=True
+            base_url="https://example.com/from_init", api_key=api_key, _strict_response_validation=True
         )
         assert client.base_url == "https://example.com/from_init/"
 
@@ -1330,20 +1313,18 @@ def test_base_url_setter(self) -> None:
 
     def test_base_url_env(self) -> None:
         with update_env(BRAINBASE_BASE_URL="http://localhost:5000/from/env"):
-            client = AsyncBrainbase(bearer_token=bearer_token, _strict_response_validation=True)
+            client = AsyncBrainbase(api_key=api_key, _strict_response_validation=True)
             assert client.base_url == "http://localhost:5000/from/env/"
 
     @pytest.mark.parametrize(
         "client",
         [
             AsyncBrainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
+                base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True
             ),
             AsyncBrainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.AsyncClient(),
             ),
@@ -1364,13 +1345,11 @@ def test_base_url_trailing_slash(self, client: AsyncBrainbase) -> None:
         "client",
         [
             AsyncBrainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
+                base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True
             ),
             AsyncBrainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.AsyncClient(),
             ),
@@ -1391,13 +1370,11 @@ def test_base_url_no_trailing_slash(self, client: AsyncBrainbase) -> None:
         "client",
         [
             AsyncBrainbase(
-                base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
+                base_url="http://localhost:5000/custom/path/", api_key=api_key, _strict_response_validation=True
             ),
             AsyncBrainbase(
                 base_url="http://localhost:5000/custom/path/",
-                bearer_token=bearer_token,
+                api_key=api_key,
                 _strict_response_validation=True,
                 http_client=httpx.AsyncClient(),
             ),
@@ -1415,7 +1392,7 @@ def test_absolute_request_url(self, client: AsyncBrainbase) -> None:
         assert request.url == "https://myapi.com/foo"
 
     async def test_copied_client_does_not_close_http(self) -> None:
-        client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
         assert not client.is_closed()
 
         copied = client.copy()
@@ -1427,7 +1404,7 @@ async def test_copied_client_does_not_close_http(self) -> None:
         assert not client.is_closed()
 
     async def test_client_context_manager(self) -> None:
-        client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
         async with client as c2:
             assert c2 is client
             assert not c2.is_closed()
@@ -1450,10 +1427,7 @@ class Model(BaseModel):
     async def test_client_max_retries_validation(self) -> None:
         with pytest.raises(TypeError, match=r"max_retries cannot be None"):
             AsyncBrainbase(
-                base_url=base_url,
-                bearer_token=bearer_token,
-                _strict_response_validation=True,
-                max_retries=cast(Any, None),
+                base_url=base_url, api_key=api_key, _strict_response_validation=True, max_retries=cast(Any, None)
             )
 
     @pytest.mark.respx(base_url=base_url)
@@ -1464,12 +1438,12 @@ class Model(BaseModel):
 
         respx_mock.get("/foo").mock(return_value=httpx.Response(200, text="my-custom-format"))
 
-        strict_client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        strict_client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
         with pytest.raises(APIResponseValidationError):
             await strict_client.get("/foo", cast_to=Model)
 
-        client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=False)
+        client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=False)
 
         response = await client.get("/foo", cast_to=Model)
         assert isinstance(response, str)  # type: ignore[unreachable]
@@ -1498,7 +1472,7 @@ class Model(BaseModel):
     @mock.patch("time.time", mock.MagicMock(return_value=1696004797))
     @pytest.mark.asyncio
     async def test_parse_retry_after_header(self, remaining_retries: int, retry_after: str, timeout: float) -> None:
-        client = AsyncBrainbase(base_url=base_url, bearer_token=bearer_token, _strict_response_validation=True)
+        client = AsyncBrainbase(base_url=base_url, api_key=api_key, _strict_response_validation=True)
 
         headers = httpx.Headers({"retry-after": retry_after})
         options = FinalRequestOptions(method="get", url="/foo", max_retries=3)