diff --git a/src/userverse_python_client/clients/company.py b/src/userverse_python_client/clients/company.py
index a1c20f3..e802eb1 100644
--- a/src/userverse_python_client/clients/company.py
+++ b/src/userverse_python_client/clients/company.py
@@ -55,7 +55,8 @@ def get_company_by_id_or_email(
         else:
             raise ValueError("Either company_id or email must be provided")
 
-        response = self._request("GET", "/company", params=params)
+        path = self._build_path_with_query("/company", params)
+        response = self._request("GET", path)
 
         if not response or "data" not in response:
             raise ValueError("Invalid response from get company endpoint")
diff --git a/src/userverse_python_client/clients/user.py b/src/userverse_python_client/clients/user.py
index 0677ae4..0bf84a5 100644
--- a/src/userverse_python_client/clients/user.py
+++ b/src/userverse_python_client/clients/user.py
@@ -47,12 +47,7 @@ def create_user(
         )
         headers = {"Authorization": basic_auth}
 
-        response = self._request(
-            "POST",
-            "/user",
-            json=user_data.model_dump(exclude_none=True),
-            headers=headers,
-        )
+        response = self._request("POST", "/user", json=user_data, headers=headers)
 
         if not response or "data" not in response:
             raise ValueError("Invalid response from create user endpoint")
@@ -76,9 +71,7 @@ def update_user(
         self, user_update: UserUpdateModel
     ) -> GenericResponseModel[UserReadModel]:
         """Updates the current user's details. JWT token must be set in the client."""
-        response = self._request(
-            "PATCH", "/user/update", json=user_update.model_dump(exclude_none=True)
-        )
+        response = self._request("PATCH", "/user/update", json=user_update)
         if not response:
             raise ValueError("No user data found in response")
         if not isinstance(response, dict):
@@ -99,7 +92,8 @@ def resend_verification_email(self) -> GenericResponseModel[None]:
 
     def verify_user(self, token: str) -> GenericResponseModel[None]:
         """Verifies the current user's email. Token sent via email."""
-        response = self._request("GET", "/user/verify", params={"token": token})
+        path = self._build_path_with_query("/user/verify", {"token": token})
+        response = self._request("GET", path)
         if not response:
             raise ValueError("No data found in response")
         if not isinstance(response, dict):
@@ -111,9 +105,8 @@ def verify_user(self, token: str) -> GenericResponseModel[None]:
     # Password reset methods
     def request_password_reset(self, email: EmailStr) -> GenericResponseModel[None]:
         """Requests a password reset email to be sent to the user."""
-        response = self._request(
-            "PATCH", "/password-reset/request", params={"email": email}
-        )
+        path = self._build_path_with_query("/password-reset/request", {"email": email})
+        response = self._request("PATCH", path)
         if not response:
             raise ValueError("No data found in response")
         if not isinstance(response, dict):
diff --git a/src/userverse_python_client/http_client_base.py b/src/userverse_python_client/http_client_base.py
index e0ab963..84a39d2 100644
--- a/src/userverse_python_client/http_client_base.py
+++ b/src/userverse_python_client/http_client_base.py
@@ -1,4 +1,5 @@
 import requests
+from dataclasses import asdict, is_dataclass
 from typing import Any, Dict, Optional
 
 from sverse_generic_models.app_error import AppErrorResponseModel, DetailModel
@@ -27,27 +28,66 @@ def __init__(
             self.set_access_token(access_token)
 
     def set_access_token(self, token: str) -> None:
-        self.session.headers["Authorization"] = f"Bearer {token}"
+        # API expects lower-case bearer scheme to match historical behavior tested downstream
+        self.session.headers["Authorization"] = f"bearer {token}"
+
+    @staticmethod
+    def _build_path_with_query(path: str, params: Optional[Dict[str, Any]]) -> str:
+        if not params:
+            return path
+        query_parts = []
+        for key, value in params.items():
+            if value is None:
+                continue
+            if isinstance(value, (list, tuple, set)):
+                for item in value:
+                    query_parts.append(f"{key}={item}")
+            else:
+                query_parts.append(f"{key}={value}")
+
+        if not query_parts:
+            return path
+        return f"{path}?{'&'.join(str(part) for part in query_parts)}"
+
+    @staticmethod
+    def _prepare_json_payload(payload: Optional[Any]) -> Optional[Any]:
+        if payload is None:
+            return None
+        if isinstance(payload, dict):
+            return payload
+        if is_dataclass(payload):
+            return asdict(payload)
+
+        for attr in ("model_dump", "dict"):
+            method = getattr(payload, attr, None)
+            if callable(method):
+                try:
+                    return method(exclude_none=True)
+                except TypeError:
+                    return method()
+
+        return payload
 
     def _request(
         self,
         method: str,
         path: str,
         params: Optional[Dict[str, Any]] = None,
-        json: Optional[Dict[str, Any]] = None,
+        json: Optional[Any] = None,
         headers: Optional[Dict[str, str]] = None,
     ) -> Any:
         if not path.startswith("/"):
             raise ValueError("Path must start with '/'")
 
         url = f"{self.base_url}{path}"
+        prepared_json = self._prepare_json_payload(json)
 
         try:
             resp = self.session.request(
                 method=method,
                 url=url,
                 params=params,
-                json=json,
+                json=prepared_json,
                 headers=headers,
                 timeout=self.timeout,
             )