diff --git a/litellm/proxy/_types.py b/litellm/proxy/_types.py
index 95739834a9a9..f453ef28c5dc 100644
--- a/litellm/proxy/_types.py
+++ b/litellm/proxy/_types.py
@@ -676,6 +676,11 @@ class LiteLLMRoutes(enum.Enum):
     )
 
 
+# Pre-computed tuple for fast startswith() checks against mapped pass-through routes.
+# Defined once here and imported by auth/route_checks modules.
+MAPPED_PASS_THROUGH_PREFIXES = tuple(LiteLLMRoutes.mapped_pass_through_routes.value)
+
+
 class LiteLLMPromptInjectionParams(LiteLLMPydanticObjectBase):
     heuristics_check: bool = False
     vector_db_check: bool = False
diff --git a/litellm/proxy/auth/route_checks.py b/litellm/proxy/auth/route_checks.py
index a00401008fcb..ddf19f67f1a6 100644
--- a/litellm/proxy/auth/route_checks.py
+++ b/litellm/proxy/auth/route_checks.py
@@ -5,6 +5,7 @@
 
 from litellm._logging import verbose_proxy_logger
 from litellm.proxy._types import (
+    MAPPED_PASS_THROUGH_PREFIXES,
     CommonProxyErrors,
     LiteLLM_UserTable,
     LiteLLMRoutes,
@@ -346,9 +347,8 @@ def is_llm_api_route(route: str) -> bool:
         if RouteChecks._is_azure_openai_route(route=route):
             return True
 
-        for _llm_passthrough_route in LiteLLMRoutes.mapped_pass_through_routes.value:
-            if _llm_passthrough_route in route:
-                return True
+        if route.startswith(MAPPED_PASS_THROUGH_PREFIXES):
+            return True
         return False
 
     @staticmethod
diff --git a/litellm/proxy/auth/user_api_key_auth.py b/litellm/proxy/auth/user_api_key_auth.py
index 138f9bab2c42..11d6ebe774e0 100644
--- a/litellm/proxy/auth/user_api_key_auth.py
+++ b/litellm/proxy/auth/user_api_key_auth.py
@@ -78,6 +78,9 @@
 
 user_api_key_service_logger_obj = ServiceLogging()  # used for tracking latency on OTEL
 
+# Pre-computed constants to avoid repeated enum attribute access
+_PUBLIC_ROUTES = LiteLLMRoutes.public_routes.value
+
 custom_litellm_key_header = APIKeyHeader(
     name=SpecialHeaders.custom_litellm_api_key.value,
     auto_error=False,
@@ -358,15 +361,6 @@ def get_api_key(
         google_auth_key: str = _safe_get_request_query_params(request).get("key") or ""
         passed_in_key = google_auth_key
         api_key = google_auth_key
-    elif pass_through_endpoints is not None:
-        for endpoint in pass_through_endpoints:
-            if endpoint.get("path", "") == route:
-                headers: Optional[dict] = endpoint.get("headers", None)
-                if headers is not None:
-                    header_key: str = headers.get("litellm_user_api_key", "")
-                    if request.headers.get(header_key) is not None:
-                        api_key = request.headers.get(header_key) or ""
-                        passed_in_key = api_key
     return api_key, passed_in_key
 
 
@@ -376,29 +370,22 @@ async def check_api_key_for_custom_headers_or_pass_through_endpoints(
     pass_through_endpoints: Optional[List[dict]],
     api_key: str,
 ) -> Union[UserAPIKeyAuth, str]:
-    is_mapped_pass_through_route: bool = False
-    for mapped_route in LiteLLMRoutes.mapped_pass_through_routes.value:  # type: ignore
-        if route.startswith(mapped_route):
-            is_mapped_pass_through_route = True
-    if is_mapped_pass_through_route:
-        if request.headers.get("litellm_user_api_key") is not None:
-            api_key = request.headers.get("litellm_user_api_key") or ""
+    # Fast path: nothing to check
+    is_mapped = route.startswith(MAPPED_PASS_THROUGH_PREFIXES)
+    if not is_mapped and pass_through_endpoints is None:
+        return api_key
+
+    if is_mapped:
+        value = request.headers.get("litellm_user_api_key")
+        if value is not None:
+            api_key = value
+
     if pass_through_endpoints is not None:
         for endpoint in pass_through_endpoints:
             if isinstance(endpoint, dict) and endpoint.get("path", "") == route:
-                ## IF AUTH DISABLED
                 if endpoint.get("auth") is not True:
                     return UserAPIKeyAuth()
-                ## IF AUTH ENABLED
-                ### IF CUSTOM PARSER REQUIRED
-                if (
-                    endpoint.get("custom_auth_parser") is not None
-                    and endpoint.get("custom_auth_parser") == "langfuse"
-                ):
-                    """
-                    - langfuse returns {'Authorization': 'Basic YW55dGhpbmc6YW55dGhpbmc'}
-                    - check the langfuse public key if it contains the litellm api key
-                    """
+                if endpoint.get("custom_auth_parser") == "langfuse":
                     import base64
 
                     api_key = api_key.replace("Basic ", "").strip()
@@ -409,11 +396,10 @@ async def check_api_key_for_custom_headers_or_pass_through_endpoints(
                     headers = endpoint.get("headers", None)
                     if headers is not None:
                         header_key = headers.get("litellm_user_api_key", "")
-                        if (
-                            isinstance(request.headers, dict)
-                            and request.headers.get(key=header_key) is not None  # type: ignore
-                        ):
-                            api_key = request.headers.get(key=header_key)  # type: ignore
+                        value = request.headers.get(header_key)
+                        if value is not None:
+                            api_key = value
+                break  # found matching endpoint, stop looping
     return api_key
 
 
@@ -426,6 +412,7 @@ async def _user_api_key_auth_builder(  # noqa: PLR0915
     azure_apim_header: Optional[str],
     request_data: dict,
     custom_litellm_key_header: Optional[str] = None,
+    route: Optional[str] = None,
 ) -> UserAPIKeyAuth:
     from litellm.proxy.proxy_server import (
         general_settings,
@@ -444,7 +431,8 @@ async def _user_api_key_auth_builder(  # noqa: PLR0915
 
     parent_otel_span: Optional[Span] = None
     start_time = datetime.now()
-    route: str = get_request_route(request=request)
+    if route is None:
+        route = get_request_route(request=request)
     valid_token: Optional[UserAPIKeyAuth] = None
     custom_auth_api_key: bool = False
 
@@ -483,7 +471,7 @@ async def _user_api_key_auth_builder(  # noqa: PLR0915
             parent_otel_span = (
                 open_telemetry_logger.create_litellm_proxy_request_started_span(
                     start_time=start_time,
-                    headers=dict(request.headers),
+                    headers=_safe_get_request_headers(request),
                 )
             )
 
@@ -515,7 +503,7 @@ async def _user_api_key_auth_builder(  # noqa: PLR0915
 
         ######## Route Checks Before Reading DB / Cache for "token" ################
         if (
-            route in LiteLLMRoutes.public_routes.value  # type: ignore
+            route in _PUBLIC_ROUTES
             or route_in_additonal_public_routes(current_route=route)
         ):
             # check if public endpoint
@@ -1371,6 +1359,7 @@ async def user_api_key_auth(
         azure_apim_header=azure_apim_header,
         request_data=request_data,
         custom_litellm_key_header=custom_litellm_key_header,
+        route=route,
     )
 
     ## ENSURE DISABLE ROUTE WORKS ACROSS ALL USER AUTH FLOWS ##
diff --git a/litellm/proxy/common_utils/http_parsing_utils.py b/litellm/proxy/common_utils/http_parsing_utils.py
index e1bca6e905f6..8d179a9caed0 100644
--- a/litellm/proxy/common_utils/http_parsing_utils.py
+++ b/litellm/proxy/common_utils/http_parsing_utils.py
@@ -135,17 +135,29 @@ def _safe_set_request_parsed_body(
 
 def _safe_get_request_headers(request: Optional[Request]) -> dict:
     """
-    [Non-Blocking] Safely get the request headers
+    [Non-Blocking] Safely get the request headers.
+    Caches the result on request.state to avoid re-creating dict(request.headers) per call.
+
+    Warning: Callers must NOT mutate the returned dict — it is shared across
+    all callers within the same request via the cache.
     """
+    if request is None:
+        return {}
+    cached = getattr(request.state, "_cached_headers", None)
+    if cached is not None:
+        return cached
     try:
-        if request is None:
-            return {}
-        return dict(request.headers)
+        headers = dict(request.headers)
     except Exception as e:
         verbose_proxy_logger.debug(
             "Unexpected error reading request headers - {}".format(e)
         )
-        return {}
+        headers = {}
+    try:
+        request.state._cached_headers = headers
+    except Exception:
+        pass  # request.state may not be available in all contexts
+    return headers
 
 
 def check_file_size_under_limit(
diff --git a/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py b/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
index d1c4b8b34036..71e2cb9c42c2 100644
--- a/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
+++ b/litellm/proxy/pass_through_endpoints/pass_through_endpoints.py
@@ -40,9 +40,9 @@
 from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
 from litellm.passthrough import BasePassthroughUtils
 from litellm.proxy._types import (
+    MAPPED_PASS_THROUGH_PREFIXES,
     ConfigFieldInfo,
     ConfigFieldUpdate,
-    LiteLLMRoutes,
     PassThroughEndpointResponse,
     PassThroughGenericEndpoint,
     ProxyException,
@@ -2058,9 +2058,8 @@ def is_registered_pass_through_route(route: str) -> bool:
             bool: True if route is a registered pass-through endpoint, False otherwise
         """
         ## CHECK IF MAPPED PASS THROUGH ENDPOINT
-        for mapped_route in LiteLLMRoutes.mapped_pass_through_routes.value:
-            if route.startswith(mapped_route):
-                return True
+        if route.startswith(MAPPED_PASS_THROUGH_PREFIXES):
+            return True
 
         # Fast path: check if any registered route key contains this path
         # Keys are in format: "{endpoint_id}:exact:{path}:{methods}" or "{endpoint_id}:subpath:{path}:{methods}"
diff --git a/tests/test_litellm/proxy/auth/test_user_api_key_auth.py b/tests/test_litellm/proxy/auth/test_user_api_key_auth.py
index 79c2ed4158b7..f90cb5922cd6 100644
--- a/tests/test_litellm/proxy/auth/test_user_api_key_auth.py
+++ b/tests/test_litellm/proxy/auth/test_user_api_key_auth.py
@@ -443,6 +443,166 @@ async def test_return_user_api_key_auth_obj_user_spend_and_budget():
     assert result.user_email == "test@example.com"
 
 
+# ── Regression tests for auth optimizations ──────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_check_api_key_normal_route_returns_api_key():
+    """Normal route, no pass-through config -> returns api_key unchanged."""
+    from litellm.proxy.auth.user_api_key_auth import (
+        check_api_key_for_custom_headers_or_pass_through_endpoints,
+    )
+
+    request = MagicMock()
+    request.headers = {}
+    result = await check_api_key_for_custom_headers_or_pass_through_endpoints(
+        request=request,
+        route="/chat/completions",
+        pass_through_endpoints=None,
+        api_key="sk-test123",
+    )
+    assert result == "sk-test123"
+
+
+@pytest.mark.asyncio
+async def test_check_api_key_mapped_pass_through_with_header():
+    """Route /anthropic/v1/messages, header litellm_user_api_key set -> extracts key."""
+    from litellm.proxy.auth.user_api_key_auth import (
+        check_api_key_for_custom_headers_or_pass_through_endpoints,
+    )
+
+    request = MagicMock()
+    request.headers = {"litellm_user_api_key": "sk-from-header"}
+    result = await check_api_key_for_custom_headers_or_pass_through_endpoints(
+        request=request,
+        route="/anthropic/v1/messages",
+        pass_through_endpoints=None,
+        api_key="sk-original",
+    )
+    assert result == "sk-from-header"
+
+
+@pytest.mark.asyncio
+async def test_check_api_key_configured_endpoint_auth_disabled():
+    """Pass-through endpoint with auth: false -> returns UserAPIKeyAuth()."""
+    from litellm.proxy._types import UserAPIKeyAuth
+    from litellm.proxy.auth.user_api_key_auth import (
+        check_api_key_for_custom_headers_or_pass_through_endpoints,
+    )
+
+    request = MagicMock()
+    request.headers = {}
+    endpoints = [{"path": "/custom/endpoint", "auth": False}]
+    result = await check_api_key_for_custom_headers_or_pass_through_endpoints(
+        request=request,
+        route="/custom/endpoint",
+        pass_through_endpoints=endpoints,
+        api_key="sk-test",
+    )
+    assert isinstance(result, UserAPIKeyAuth)
+
+
+@pytest.mark.asyncio
+async def test_check_api_key_configured_endpoint_langfuse_parser():
+    """Langfuse endpoint with Base64 auth -> parses correctly."""
+    import base64
+
+    from litellm.proxy.auth.user_api_key_auth import (
+        check_api_key_for_custom_headers_or_pass_through_endpoints,
+    )
+
+    public_key = "sk-lf-public"
+    secret_key = "sk-lf-secret"
+    basic_auth = base64.b64encode(f"{public_key}:{secret_key}".encode()).decode()
+
+    request = MagicMock()
+    request.headers = {}
+    endpoints = [
+        {"path": "/langfuse/api", "auth": True, "custom_auth_parser": "langfuse"}
+    ]
+    result = await check_api_key_for_custom_headers_or_pass_through_endpoints(
+        request=request,
+        route="/langfuse/api",
+        pass_through_endpoints=endpoints,
+        api_key=f"Basic {basic_auth}",
+    )
+    assert result == public_key
+
+
+@pytest.mark.asyncio
+async def test_check_api_key_configured_endpoint_custom_header():
+    """Pass-through endpoint with custom header config -> extracts from configured header."""
+    from litellm.proxy.auth.user_api_key_auth import (
+        check_api_key_for_custom_headers_or_pass_through_endpoints,
+    )
+
+    request = MagicMock()
+    request.headers = {"x-custom-key": "sk-custom-value"}
+    endpoints = [
+        {
+            "path": "/custom/endpoint",
+            "auth": True,
+            "headers": {"litellm_user_api_key": "x-custom-key"},
+        }
+    ]
+    result = await check_api_key_for_custom_headers_or_pass_through_endpoints(
+        request=request,
+        route="/custom/endpoint",
+        pass_through_endpoints=endpoints,
+        api_key="sk-original",
+    )
+    assert result == "sk-custom-value"
+
+
+def test_get_api_key_without_pass_through_branch():
+    """
+    Regression test for Round 2: after removing the elif pass_through_endpoints branch
+    from get_api_key, the key should still be extractable via Bearer token even when
+    pass_through_endpoints is configured (the later check_api_key_for_... call handles it).
+    """
+    endpoints = [
+        {
+            "path": "/custom/endpoint",
+            "auth": True,
+            "headers": {"litellm_user_api_key": "x-custom-key"},
+        }
+    ]
+    request = MagicMock()
+    request.headers = {"x-custom-key": "sk-custom-value"}
+
+    api_key, passed_in_key = get_api_key(
+        custom_litellm_key_header=None,
+        api_key="Bearer sk-test-key",
+        azure_api_key_header=None,
+        anthropic_api_key_header=None,
+        google_ai_studio_api_key_header=None,
+        azure_apim_header=None,
+        pass_through_endpoints=endpoints,
+        route="/custom/endpoint",
+        request=request,
+    )
+    # Bearer token should be extracted normally regardless of pass_through_endpoints
+    assert api_key == "sk-test-key"
+    assert passed_in_key == "Bearer sk-test-key"
+
+
+def test_safe_get_request_headers_caching():
+    """Call _safe_get_request_headers twice on same request, assert returns same dict object."""
+    from starlette.datastructures import State
+
+    from litellm.proxy.common_utils.http_parsing_utils import (
+        _safe_get_request_headers,
+    )
+
+    request = MagicMock()
+    request.headers = {"content-type": "application/json", "authorization": "Bearer sk-123"}
+    request.state = State()  # real State object that supports attribute setting
+
+    result1 = _safe_get_request_headers(request)
+    result2 = _safe_get_request_headers(request)
+    assert result1 is result2, "Second call should return the same cached dict object"
+
+
 def test_proxy_admin_jwt_auth_includes_identity_fields():
     """
     Test that the proxy admin early-return path in JWT auth populates
diff --git a/tests/test_litellm/proxy/common_utils/test_http_parsing_utils.py b/tests/test_litellm/proxy/common_utils/test_http_parsing_utils.py
index af366b082a07..16f934d8d464 100644
--- a/tests/test_litellm/proxy/common_utils/test_http_parsing_utils.py
+++ b/tests/test_litellm/proxy/common_utils/test_http_parsing_utils.py
@@ -7,6 +7,7 @@
 import pytest
 from fastapi import Request
 from fastapi.testclient import TestClient
+from starlette.datastructures import State
 
 sys.path.insert(
     0, os.path.abspath("../../../..")
@@ -36,6 +37,7 @@ async def test_request_body_caching():
     """
     # Create a mock request with a JSON body
     mock_request = MagicMock()
+    mock_request.state = State()
     test_data = {"key": "value"}
     # Use AsyncMock for the body method
     mock_request.body = AsyncMock(return_value=orjson.dumps(test_data))
@@ -69,6 +71,7 @@ async def test_form_data_parsing():
     """
     # Create a mock request with form data
     mock_request = MagicMock()
+    mock_request.state = State()
     test_data = {"name": "test_user", "message": "hello world"}
 
     # Mock the form method to return the test data as an awaitable
@@ -104,7 +107,8 @@ async def test_form_data_with_json_metadata():
     """
     # Create a mock request with form data containing JSON metadata
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     # Metadata is sent as a JSON string in form data
     metadata_json_string = json.dumps({
         "user_id": "12345",
@@ -152,7 +156,8 @@ async def test_form_data_with_invalid_json_metadata():
     """
     # Create a mock request with form data containing invalid JSON metadata
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     test_data = {
         "model": "whisper-1",
         "file": "audio.mp3",
@@ -178,7 +183,8 @@ async def test_form_data_without_metadata():
     """
     # Create a mock request with form data without metadata
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     test_data = {
         "model": "whisper-1",
         "file": "audio.mp3",
@@ -208,7 +214,8 @@ async def test_form_data_with_empty_metadata():
     """
     # Create a mock request with form data containing empty metadata
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     test_data = {
         "model": "whisper-1",
         "file": "audio.mp3",
@@ -240,7 +247,8 @@ async def test_form_data_with_dict_metadata():
     """
     # Create a mock request with form data where metadata is already a dict
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     metadata_dict = {
         "user_id": "12345",
         "tags": ["test"]
@@ -275,7 +283,8 @@ async def test_form_data_with_none_metadata():
     """
     # Create a mock request with form data where metadata is None
     mock_request = MagicMock()
-    
+    mock_request.state = State()
+
     test_data = {
         "model": "whisper-1",
         "file": "audio.mp3",
@@ -303,6 +312,7 @@ async def test_empty_request_body():
     """
     # Create a mock request with an empty body
     mock_request = MagicMock()
+    mock_request.state = State()
     mock_request.body = AsyncMock(return_value=b"")  # Empty bytes as an awaitable
     mock_request.headers = {"content-type": "application/json"}
     mock_request.scope = {}
@@ -327,6 +337,7 @@ async def test_circular_reference_handling():
     """
     # Create a mock request with initial data
     mock_request = MagicMock()
+    mock_request.state = State()
     initial_body = {
         "model": "gpt-4",
         "messages": [{"role": "user", "content": "Hello"}],
@@ -366,6 +377,7 @@ async def test_json_parsing_error_handling():
     """
     # Test case 1: Trailing comma error
     mock_request = MagicMock()
+    mock_request.state = State()
     invalid_json_with_trailing_comma = b'''{
         "model": "gpt-4o",
         "tools": [
@@ -394,6 +406,7 @@ async def test_json_parsing_error_handling():
 
     # Test case 2: Unquoted property name error
     mock_request2 = MagicMock()
+    mock_request2.state = State()
     invalid_json_unquoted_property = b'''{
         "model": "gpt-4o",
         "tools": [
@@ -418,6 +431,7 @@ async def test_json_parsing_error_handling():
 
     # Test case 3: Valid JSON should work normally
     mock_request3 = MagicMock()
+    mock_request3.state = State()
     valid_json = b'''{
         "model": "gpt-4o",
         "tools": [
@@ -749,6 +763,7 @@ async def test_request_body_with_html_script_tags():
         }
 
         mock_request = MagicMock()
+        mock_request.state = State()
         mock_request.body = AsyncMock(return_value=orjson.dumps(test_payload))
         mock_request.headers = {"content-type": "application/json"}
         mock_request.scope = {}