diff --git a/src/oci_openai/oci_openai.py b/src/oci_openai/oci_openai.py
index 650dd4c..385c0c0 100644
--- a/src/oci_openai/oci_openai.py
+++ b/src/oci_openai/oci_openai.py
@@ -182,12 +182,63 @@ class OciSessionAuth(HttpxOciAuth):
     """
 
     def __init__(
-        self, config_file: str = DEFAULT_LOCATION, profile_name: str = DEFAULT_PROFILE
+        self,
+        config_file: str = DEFAULT_LOCATION,
+        profile_name: str = DEFAULT_PROFILE,
+        **kwargs: Mapping[str, Any],
     ):
+        """
+        Initialize a Security Token-based OCI signer.
+
+        Parameters
+        ----------
+        config_file : str, optional
+            Path to the OCI configuration file. Defaults to `~/.oci/config`.
+        profile_name : str, optional
+            Profile name inside the OCI configuration file to use. Defaults to "DEFAULT".
+        **kwargs : Mapping[str, Any]
+            Optional keyword arguments:
+              - `generic_headers`: Optional[Dict[str, str]]
+                    Headers to be used for generic requests.
+                    Default: `["date", "(request-target)", "host"]`
+              - `body_headers`: Optional[Dict[str, str]]
+                    Headers to be used for signed request bodies.
+                    Default: `["content-length", "content-type", "x-content-sha256"]`
+
+        Raises
+        ------
+        oci.exceptions.ConfigFileNotFound
+            If the configuration file cannot be found.
+        KeyError
+            If a required key such as `"key_file"` is missing in the config.
+        Exception
+            For any other initialization errors.
+        """
+        # Load OCI configuration and token
         config = oci.config.from_file(config_file, profile_name)
         token = self._load_token(config)
-        private_key = oci.signer.load_private_key_from_file(config["key_file"])  # type: ignore
-        self.signer = oci.auth.signers.SecurityTokenSigner(token, private_key)
+
+        # Load the private key from config
+        key_path = config.get("key_file")
+        if not key_path:
+            raise KeyError(
+                f"Missing 'key_file' entry in OCI config profile '{profile_name}'."
+            )
+        private_key = oci.signer.load_private_key_from_file(key_path)
+
+        # Optional signer header customization
+        generic_headers = kwargs.pop("generic_headers", None)
+        body_headers = kwargs.pop("body_headers", None)
+
+        additional_kwargs = {}
+        if generic_headers:
+            additional_kwargs["generic_headers"] = generic_headers
+        if body_headers:
+            additional_kwargs["body_headers"] = body_headers
+
+        self.signer = oci.auth.signers.SecurityTokenSigner(
+            token, private_key, **additional_kwargs
+        )
 
     def _load_token(self, config: Mapping[str, Any]) -> str:
         token_file = config["security_token_file"]