diff --git a/Makefile b/Makefile
index 44199243..a6f3f70b 100644
--- a/Makefile
+++ b/Makefile
@@ -3,5 +3,5 @@
 docs:
 	poetry install --with dev
 	poetry run sphinx-apidoc -o docs src/imednet \
-	    src/imednet/core/__init__.py src/imednet/models/base.py
+	    src/imednet/errors/__init__.py src/imednet/models/base.py
 	poetry run sphinx-build -b html --keep-going docs docs/_build/html
diff --git a/docs/api_overview.rst b/docs/api_overview.rst
index 538d1ba6..8020b81f 100644
--- a/docs/api_overview.rst
+++ b/docs/api_overview.rst
@@ -29,12 +29,12 @@ HTTP methods and errors
 The API primarily supports ``GET`` and ``POST`` requests. Non‐successful status
 codes raise typed exceptions:
 
-* ``400`` – :class:`~imednet.core.exceptions.ValidationError`
-* ``401`` – :class:`~imednet.core.exceptions.AuthenticationError`
-* ``403`` – :class:`~imednet.core.exceptions.AuthorizationError`
-* ``404`` – :class:`~imednet.core.exceptions.NotFoundError`
-* ``429`` – :class:`~imednet.core.exceptions.RateLimitError`
-* ``5xx`` – :class:`~imednet.core.exceptions.ServerError`
+* ``400`` – :class:`~imednet.errors.ValidationError`
+* ``401`` – :class:`~imednet.errors.AuthenticationError`
+* ``403`` – :class:`~imednet.errors.AuthorizationError`
+* ``404`` – :class:`~imednet.errors.NotFoundError`
+* ``429`` – :class:`~imednet.errors.RateLimitError`
+* ``5xx`` – :class:`~imednet.errors.ServerError`
 
 See :doc:`retry_policy` for examples of handling these errors and configuring
 custom retry logic.
diff --git a/docs/imednet.core.rst b/docs/imednet.core.rst
index 40790e7e..4443ad75 100644
--- a/docs/imednet.core.rst
+++ b/docs/imednet.core.rst
@@ -59,13 +59,6 @@ HTTPX requests used by the SDK:
    :show-inheritance:
    :noindex:
 
-imednet.core.exceptions module
-------------------------------
-
-.. automodule:: imednet.core.exceptions
-   :members:
-   :undoc-members:
-   :show-inheritance:
 
 imednet.core.paginator module
 -----------------------------
@@ -87,7 +80,7 @@ requests should be retried. The SDK uses
 
    from imednet.core.client import Client
    from imednet.core.retry import RetryPolicy, RetryState
-   from imednet.core.exceptions import ServerError
+   from imednet.errors import ServerError
 
    class ServerRetry(RetryPolicy):
        def should_retry(self, state: RetryState) -> bool:
diff --git a/docs/quick_start.rst b/docs/quick_start.rst
index 820b58d7..e2863449 100644
--- a/docs/quick_start.rst
+++ b/docs/quick_start.rst
@@ -47,7 +47,7 @@ Custom retry logic can be provided via a ``RetryPolicy``:
 .. code-block:: python
 
    from imednet.core.retry import RetryPolicy, RetryState
-   from imednet.core.exceptions import ServerError
+   from imednet.errors import ServerError
 
    class ServerRetry(RetryPolicy):
        def should_retry(self, state: RetryState) -> bool:
diff --git a/docs/retry_policy.rst b/docs/retry_policy.rst
index 2a060b32..97ea02b4 100644
--- a/docs/retry_policy.rst
+++ b/docs/retry_policy.rst
@@ -13,7 +13,7 @@ Use typed exceptions to respond to different failure modes:
 .. code-block:: python
 
    from imednet import ImednetSDK
-   from imednet.core.exceptions import RateLimitError, ServerError, NotFoundError
+   from imednet.errors import RateLimitError, ServerError, NotFoundError
 
    sdk = ImednetSDK()
    try:
@@ -35,7 +35,7 @@ Retry policies decide if a request should be retried. To retry on
 
    from imednet.core.client import Client
    from imednet.core.retry import RetryPolicy, RetryState
-   from imednet.core.exceptions import RateLimitError, ServerError
+   from imednet.errors import RateLimitError, ServerError
 
    class RateLimitServerRetry(RetryPolicy):
        def should_retry(self, state: RetryState) -> bool:
diff --git a/docs/schema_validation.rst b/docs/schema_validation.rst
index 3c4a3358..118fbfb3 100644
--- a/docs/schema_validation.rst
+++ b/docs/schema_validation.rst
@@ -7,7 +7,7 @@ submitting it to the API. The validator checks that all variables exist,
 required fields are present, and that values match the expected types.
 If the variable metadata for a form is missing, ``SchemaValidator`` automatically
 loads it from the API using :class:`~imednet.endpoints.variables.VariablesEndpoint`.
-Any problems raise :class:`~imednet.core.exceptions.ValidationError` before the
+Any problems raise :class:`~imednet.errors.ValidationError` before the
 record is sent to the server.
 
 ``SchemaValidator`` works with both synchronous and asynchronous SDK clients.
diff --git a/examples/custom_retry.py b/examples/custom_retry.py
index 64f15288..ff7ba241 100644
--- a/examples/custom_retry.py
+++ b/examples/custom_retry.py
@@ -6,9 +6,10 @@
 
 import httpx
 
+from imednet.auth.strategy import AuthStrategy
 from imednet.core.client import Client
-from imednet.core.exceptions import RateLimitError, ServerError
 from imednet.core.retry import RetryPolicy, RetryState
+from imednet.errors import RateLimitError, ServerError
 from imednet.utils import configure_json_logging
 
 """Demonstrate custom retry logic with simulated rate limit and server errors.
@@ -49,14 +50,13 @@ def responder(_: httpx.Request) -> httpx.Response:
 
 
 class MockClient(Client):
-    def _create_client(self, api_key: str, security_key: str) -> httpx.Client:  # type: ignore[override]
+    def _create_client(self, auth: AuthStrategy) -> httpx.Client:  # type: ignore[override]
         return httpx.Client(
             base_url=self.base_url,
             headers={
                 "Accept": "application/json",
                 "Content-Type": "application/json",
-                "x-api-key": api_key,
-                "x-imn-security-key": security_key,
+                **auth.get_headers(),
             },
             timeout=self.timeout,
             transport=httpx.MockTransport(responder),