diff --git a/frappe/oauth.py b/frappe/oauth.py
index 5e170db5d2..67595555f9 100644
--- a/frappe/oauth.py
+++ b/frappe/oauth.py
@@ -2,13 +2,14 @@ import base64
 import datetime
 import hashlib
 import re
-from http import cookies
-from urllib.parse import unquote, urljoin, urlparse
+from urllib.parse import urljoin, urlparse
 
+from oauthlib.common import Request
 from oauthlib.openid import RequestValidator
 
 import frappe
 from frappe.auth import LoginManager
+from frappe.integrations.doctype.oauth_client.oauth_client import OAuthClient
 from frappe.utils.data import cstr, get_system_timezone, now_datetime
 
 
@@ -73,13 +74,11 @@ class OAuthWebRequestValidator(RequestValidator):
 	# Post-authorization
 
 	def save_authorization_code(self, client_id, code, request, *args, **kwargs):
-		cookie_dict = get_cookie_dict_from_headers(request)
-
 		oac = frappe.new_doc("OAuth Authorization Code")
 		oac.scopes = get_url_delimiter().join(request.scopes)
 		oac.redirect_uri_bound_to_authorization_code = request.redirect_uri
 		oac.client = client_id
-		oac.user = unquote(cookie_dict["user_id"].value)
+		oac.user = frappe.session.user
 		oac.authorization_code = code["code"]
 
 		if request.nonce:
@@ -92,43 +91,32 @@ class OAuthWebRequestValidator(RequestValidator):
 		oac.save(ignore_permissions=True)
 		frappe.db.commit()
 
-	def authenticate_client(self, request, *args, **kwargs):
+	def authenticate_client(self, request: Request, *args, **kwargs) -> bool | None:
+		"""
+		Loads the client based on request parameters and sets in oauth request.
+		Returns True on success, None on error.
+		"""
 		# Get ClientID in URL
 		if request.client_id:
-			oc = frappe.get_doc("OAuth Client", request.client_id)
+			client_name = request.client_id
 		else:
 			# Extract token, instantiate OAuth Bearer Token and use clientid from there.
 			if "refresh_token" in frappe.form_dict:
-				oc = frappe.get_doc(
-					"OAuth Client",
-					frappe.db.get_value(
-						"OAuth Bearer Token",
-						{"refresh_token": frappe.form_dict["refresh_token"]},
-						"client",
-					),
-				)
+				token_filters = {"refresh_token": frappe.form_dict["refresh_token"]}
 			elif "token" in frappe.form_dict:
-				oc = frappe.get_doc(
-					"OAuth Client",
-					frappe.db.get_value("OAuth Bearer Token", frappe.form_dict["token"], "client"),
-				)
+				token_filters = {"name": frappe.form_dict["token"]}
 			else:
-				oc = frappe.get_doc(
-					"OAuth Client",
-					frappe.db.get_value(
-						"OAuth Bearer Token",
-						frappe.get_request_header("Authorization").split(" ")[1],
-						"client",
-					),
-				)
+				token_filters = {"name": frappe.get_request_header("Authorization").split(" ")[1]}
+
+			client_name = frappe.db.get_value("OAuth Bearer Token", filters=token_filters, fieldname="client")
+
+		oc: OAuthClient = frappe.get_doc("OAuth Client", client_name)
 		try:
 			request.client = request.client or oc.as_dict()
 		except Exception as e:
 			return generate_json_error_response(e)
 
-		cookie_dict = get_cookie_dict_from_headers(request)
-		user_id = unquote(cookie_dict.get("user_id").value) if "user_id" in cookie_dict else "Guest"
-		return frappe.session.user == user_id
+		return True
 
 	def authenticate_client_id(self, client_id, request, *args, **kwargs):
 		cli_id = frappe.db.get_value("OAuth Client", client_id, "name")
@@ -506,13 +494,6 @@ class OAuthWebRequestValidator(RequestValidator):
 		return True
 
 
-def get_cookie_dict_from_headers(r):
-	cookie = cookies.BaseCookie()
-	if r.headers.get("Cookie"):
-		cookie.load(r.headers.get("Cookie"))
-	return cookie
-
-
 def calculate_at_hash(access_token, hash_alg):
 	"""Helper method for calculating an access token
 	hash, as described in http://openid.net/specs/openid-connect-core-1_0.html#CodeIDToken