diff --git a/litellm/proxy/auth_v2/errors.py b/litellm/proxy/auth_v2/errors.py
index a7c5950790f..965589e3a58 100644
--- a/litellm/proxy/auth_v2/errors.py
+++ b/litellm/proxy/auth_v2/errors.py
@@ -3,6 +3,9 @@ from __future__ import annotations
 from typing import Optional
 
 from fastapi import HTTPException
+from fastapi.responses import JSONResponse
+
+SCIM_ERROR_SCHEMA = "urn:ietf:params:scim:api:messages:2.0:Error"
 
 
 class AuthError(HTTPException):
@@ -52,3 +55,16 @@ def forbidden_permission() -> AuthError:
 
 def account_disabled() -> AuthError:
     return AuthError(403, "Account disabled")
+
+
+def scim_error_response(exc: Exception) -> JSONResponse:
+    status_code = exc.status_code if isinstance(exc, HTTPException) else 500
+    detail = exc.detail if isinstance(exc, HTTPException) else "Internal server error"
+    return JSONResponse(
+        status_code=status_code,
+        content={
+            "schemas": [SCIM_ERROR_SCHEMA],
+            "status": str(status_code),
+            "detail": str(detail),
+        },
+    )
diff --git a/litellm/proxy/auth_v2/oidc/__init__.py b/litellm/proxy/auth_v2/oidc/__init__.py
index 0e9c3e12a15..1112293efd3 100644
--- a/litellm/proxy/auth_v2/oidc/__init__.py
+++ b/litellm/proxy/auth_v2/oidc/__init__.py
@@ -1,4 +1,9 @@
 from .config import OIDCProviderConfig
-from .router import build_oidc_router
+from .router import _provider_key, _user_from_userinfo, build_oidc_router
 
-__all__ = ["OIDCProviderConfig", "build_oidc_router"]
+__all__ = [
+    "OIDCProviderConfig",
+    "build_oidc_router",
+    "_provider_key",
+    "_user_from_userinfo",
+]
diff --git a/litellm/proxy/auth_v2/saml/__init__.py b/litellm/proxy/auth_v2/saml/__init__.py
index c6eb35a995e..c8e4e7548bb 100644
--- a/litellm/proxy/auth_v2/saml/__init__.py
+++ b/litellm/proxy/auth_v2/saml/__init__.py
@@ -1,4 +1,15 @@
 from .config import SAMLConfig
-from .router import build_saml_router
+from .router import (
+    _map_attributes,
+    _metadata_source,
+    _user_from_mapped,
+    build_saml_router,
+)
 
-__all__ = ["SAMLConfig", "build_saml_router"]
+__all__ = [
+    "SAMLConfig",
+    "build_saml_router",
+    "_map_attributes",
+    "_metadata_source",
+    "_user_from_mapped",
+]
diff --git a/litellm/proxy/auth_v2/saml/router.py b/litellm/proxy/auth_v2/saml/router.py
index c5018ac4169..20569d7324b 100644
--- a/litellm/proxy/auth_v2/saml/router.py
+++ b/litellm/proxy/auth_v2/saml/router.py
@@ -1,7 +1,7 @@
 from __future__ import annotations
 
 import time
-from typing import TYPE_CHECKING, Any, Dict, List, Optional, cast
+from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple, cast
 
 from fastapi import APIRouter, HTTPException, Request
 from fastapi.responses import RedirectResponse, Response
@@ -129,13 +129,44 @@ def build_sp_client(config: SAMLConfig) -> Saml2Client:
 
 
 class SAMLProtocolStore:
-    def __init__(self, replay_ttl_seconds: int) -> None:
-        self.outstanding: Dict[str, str] = {}
+    def __init__(
+        self,
+        replay_ttl_seconds: int,
+        outstanding_ttl_seconds: int = 300,
+        max_outstanding: int = 10000,
+    ) -> None:
+        self._outstanding: Dict[str, Tuple[float, str]] = {}
         self._seen_assertions: Dict[str, float] = {}
         self._replay_ttl = replay_ttl_seconds
+        self._outstanding_ttl = outstanding_ttl_seconds
+        self._max_outstanding = max_outstanding
 
     def remember_request(self, request_id: str, relay_state: str) -> None:
-        self.outstanding[request_id] = relay_state
+        now = time.time()
+        self._evict_outstanding(now)
+        self._outstanding[request_id] = (now + self._outstanding_ttl, relay_state)
+
+    def outstanding_relays(self) -> Dict[str, str]:
+        now = time.time()
+        return {
+            rid: relay for rid, (exp, relay) in self._outstanding.items() if exp >= now
+        }
+
+    def consume_request(self, request_id: str) -> Optional[str]:
+        entry = self._outstanding.pop(request_id, None)
+        if entry is None:
+            return None
+        expires_at, relay = entry
+        return relay if expires_at >= time.time() else None
+
+    def _evict_outstanding(self, now: float) -> None:
+        for rid in [r for r, (exp, _) in self._outstanding.items() if exp < now]:
+            self._outstanding.pop(rid, None)
+        overflow = len(self._outstanding) - self._max_outstanding + 1
+        if overflow > 0:
+            oldest = sorted(self._outstanding, key=lambda r: self._outstanding[r][0])
+            for rid in oldest[:overflow]:
+                self._outstanding.pop(rid, None)
 
     def consume_assertion(self, assertion_id: str) -> bool:
         now = time.time()
@@ -185,7 +216,7 @@ def build_saml_router(auth: "AuthSecurity") -> APIRouter:
             authn_response = client.parse_authn_request_response(
                 saml_response,
                 BINDING_HTTP_POST,
-                outstanding=protocol.outstanding or None,
+                outstanding=protocol.outstanding_relays() or None,
             )
         except Exception as exc:
             raise HTTPException(
@@ -196,7 +227,7 @@ def build_saml_router(auth: "AuthSecurity") -> APIRouter:
 
         in_response_to = getattr(authn_response, "in_response_to", None)
         bound_relay = (
-            protocol.outstanding.pop(in_response_to, None) if in_response_to else None
+            protocol.consume_request(in_response_to) if in_response_to else None
         )
 
         assertion = getattr(authn_response, "assertion", None)
diff --git a/litellm/proxy/auth_v2/scim/router.py b/litellm/proxy/auth_v2/scim/router.py
index e31cd2ce743..a106446f367 100644
--- a/litellm/proxy/auth_v2/scim/router.py
+++ b/litellm/proxy/auth_v2/scim/router.py
@@ -52,7 +52,9 @@ def _error(status_code: int, detail: str) -> JSONResponse:
 class _ScimRoute(APIRoute):
     """Render authentication failures with the SCIM Error schema (RFC 7644)."""
 
-    def get_route_handler(self) -> Callable[[Request], Coroutine[Any, Any, Response]]:
+    def get_route_handler(  # type: ignore[override]
+        self,
+    ) -> Callable[[Request], Coroutine[Any, Any, Response]]:
         handler = super().get_route_handler()
 
         async def scim_handler(request: Request) -> Response:
diff --git a/litellm/proxy/auth_v2/security.py b/litellm/proxy/auth_v2/security.py
index d311019bec2..ef0bc89e782 100644
--- a/litellm/proxy/auth_v2/security.py
+++ b/litellm/proxy/auth_v2/security.py
@@ -40,6 +40,9 @@ class AuthSecurity:
     uvicorn with ``--no-proxy-headers`` and let this module resolve the client IP,
     or leave ``trusted_proxy_cidrs`` empty and rely on uvicorn's
     ``--forwarded-allow-ips``. Do not enable both.
+
+    To return SCIM-shaped error bodies, register ``errors.scim_error_response`` as
+    the host app's exception handler for the SCIM routes.
     """
 
     def __init__(