"""
MCP Client Manager

This class is responsible for managing MCP clients with support for both SSE and HTTP streamable transports.

This is a Proxy
"""

import asyncio
import datetime
import hashlib
import json
import os
import re
import time
from collections.abc import AsyncIterator, Awaitable, Callable, Mapping, Sequence
from contextlib import asynccontextmanager
from dataclasses import dataclass, replace
from typing import TYPE_CHECKING, Any, Final, Literal, TypeAlias, TypedDict, cast
from urllib.parse import ParseResult, urlparse

import anyio
import httpx
from fastapi import HTTPException
from httpx import HTTPStatusError
from mcp import ReadResourceResult, Resource
from mcp.types import CallToolRequestParams as MCPCallToolRequestParams
from mcp.types import (
    CallToolResult,
    GetPromptRequestParams,
    GetPromptResult,
    Prompt,
    ResourceTemplate,
)
from mcp.types import Tool as MCPTool
from pydantic import AnyUrl, BaseModel
from typing_extensions import ReadOnly

import litellm
from litellm._logging import verbose_logger
from litellm.constants import (
    MCP_CLIENT_TIMEOUT,
    MCP_HEALTH_CHECK_TIMEOUT,
    MCP_METADATA_TIMEOUT,
    MCP_NPM_CACHE_DIR,
    MCP_STDIO_ALLOWED_COMMANDS,
    MCP_TOOL_LISTING_TIMEOUT,
)
from litellm.exceptions import BlockedPiiEntityError, GuardrailRaisedException
from litellm.experimental_mcp_client.client import MCPClient, MCPSigV4Auth, strip_auth_scheme
from litellm.integrations.custom_guardrail import (
    _sync_guardrail_info_to_logging_obj,  # pyright: ignore[reportPrivateUsage] - the same bridge @log_guardrail_information uses; reimplementing it here would fork the metadata-key logic
)
from litellm.litellm_core_utils.url_utils import SSRFError, async_safe_get
from litellm.llms.custom_httpx.http_handler import get_async_httpx_client
from litellm.proxy._experimental.mcp_server.auth.user_api_key_auth_mcp import (
    MCPRequestHandler,
    _is_mcp_admitted_user_subject,
)
from litellm.proxy._experimental.mcp_server.elicitation_handler import (
    MCP_ELICITATION_AVAILABLE,
)
from litellm.proxy._experimental.mcp_server.exceptions import (
    MCPServerListError,
    MCPUpstreamAuthError,
)
from litellm.proxy._experimental.mcp_server.faults.list_outcomes import (
    ServerListFault,
    raise_classified_list_failure,
    upstream_auth_challenge,
)
from litellm.proxy._experimental.mcp_server.oauth2_token_cache import (
    MCPPerUserTokenCache,
    mcp_per_user_token_cache,
    resolve_mcp_auth,
    resolved_token_header,
)
from litellm.proxy._experimental.mcp_server.oauth_utils import (
    _redact_mcp_resource_url,
    canonicalize_url_identity,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials import (
    Error,
    Ok,
    UpstreamCredentialProvider,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials.adapter import (
    raise_public,
    raise_token_exchange_challenge,
    raise_user_oauth_challenge,
    to_server_spec,
    to_subject,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials.oauth_token_store import (
    InvalidatableOAuthTokenStore,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials.per_user_oauth_store import (
    LazyPerUserOAuthTokenStore,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials.token_exchange_provider import (
    build_token_exchanger,
)
from litellm.proxy._experimental.mcp_server.outbound_credentials.types import (
    DEFAULT_CREDENTIAL_HEADER,
    AuthorizationCodeConfig,
    ClientCredentialsConfig,
    CredError,
    IdJagConfig,
    PassthroughConfig,
    ServerSpec,
    TokenExchangeConfig,
)
from litellm.proxy._experimental.mcp_server.sampling_handler import (
    MCP_SAMPLING_AVAILABLE,
)
from litellm.proxy._experimental.mcp_server.utils import (
    MCP_TOOL_PREFIX_SEPARATOR,
    MCPMissingUserEnvVarsError,
    add_server_prefix_to_name,
    build_env_var_setup_url,
    collect_env_var_references,
    compute_short_server_prefix,
    get_server_prefix,
    interpolate_headers,
    is_short_mcp_tool_prefix_enabled,
    iter_known_server_prefixes,
    iter_known_tool_name_spellings,
    logging_safe_mcp_headers,
    lookup_mcp_server_auth_in_headers,
    match_known_server_prefix,
    match_known_tool_name,
    merge_mcp_headers,
    normalize_server_name,
    openapi_tool_name,
    parse_admin_env_vars,
    strip_known_server_prefix,
    validate_mcp_server_name,
)
from litellm.proxy._types import (
    LiteLLM_MCPServerTable,
    MCPAuthType,
    MCPEnvVar,
    MCPTransport,
    MCPTransportType,
    SpecialMCPServerNames,
    UserAPIKeyAuth,
)
from litellm.proxy.auth.ip_address_utils import IPAddressUtils
from litellm.proxy.common_utils.encrypt_decrypt_utils import decrypt_value_helper
from litellm.proxy.common_utils.user_api_key_cache import get_management_object_ttl
from litellm.proxy.utils import PrismaClient, ProxyLogging, get_server_root_path
from litellm.repositories.table_repositories import MCPServerRepository
from litellm.types.llms.custom_http import httpxSpecialProvider
from litellm.types.mcp import (
    DEFAULT_SUBJECT_TOKEN_TYPE,
    MCPAuth,
    MCPStdioConfig,
    MCPTokenEndpointAuthMethod,
    has_header,
    without_header,
)
from litellm.types.mcp_server.mcp_server_manager import (
    MCPInfo,
    MCPOAuthMetadata,
    MCPServer,
)
from litellm.types.utils import CallTypes

if TYPE_CHECKING:
    from mcp.client.session import ClientSession
    from mcp.shared.context import RequestContext
    from mcp.types import CreateMessageRequestParams

    from litellm.caching.caching import InMemoryCache
    from litellm.litellm_core_utils.litellm_logging import Logging as LiteLLMLoggingObj
    from litellm.types.mcp_server.mcp_toolset import MCPToolset

try:
    from mcp.shared.tool_name_validation import (
        SEP_986_URL,
        validate_tool_name,  # pyright: ignore[reportAssignmentType]
    )
except ImportError:
    from pydantic import BaseModel

    SEP_986_URL = "https://github.com/modelcontextprotocol/protocol/blob/main/proposals/0001-tool-name-validation.md"

    class _ToolNameValidationResult(BaseModel):
        is_valid: bool = True
        warnings: list = []

    def validate_tool_name(name: str) -> _ToolNameValidationResult:
        return _ToolNameValidationResult()


# Probe includes characters on both sides of the separator to mimic real prefixed tool names.
_separator_probe_tool_name: Final = f"litellm{MCP_TOOL_PREFIX_SEPARATOR}probe"
_separator_probe: Final = validate_tool_name(_separator_probe_tool_name)
if not _separator_probe.is_valid:
    verbose_logger.warning(
        "MCP tool prefix separator '%s' violates SEP-986. See %s",
        MCP_TOOL_PREFIX_SEPARATOR,
        SEP_986_URL,
    )

_AZURE_ENTRA_HOSTS: Final = {
    "login.microsoftonline.com",  # Global
    "login.microsoftonline.us",  # US Government
    "login.chinacloudapi.cn",  # China
}

# Short-lived in-memory cache for per-user MCP env var values, mirroring the
# BYOK credential cache. Keyed by (user_id, server_id); value is
# (values_dict, monotonic_timestamp). Keeps the tool-call and tool-listing
# paths off the DB on every request within the TTL window.
_user_env_vars_cache: Final[dict[tuple[str, str], tuple[dict[str, str], float]]] = {}
_USER_ENV_VARS_CACHE_TTL: Final = 60  # seconds
_USER_ENV_VARS_CACHE_MAX_SIZE: Final = 4096  # cap to prevent unbounded growth

# Auth types whose upstream OAuth endpoints (protected-resource + authorization-server metadata) the
# gateway discovers from the upstream itself: interactive oauth2 and the two client-forwarded modes.
# OBO/M2M endpoint discovery is decided separately via _obo_needs_endpoint_discovery. Shared by the
# config-YAML and DB server loaders so the two paths cannot drift on which modes trigger discovery.
_UPSTREAM_OAUTH_DISCOVERY_AUTH_TYPES: Final[tuple[MCPAuth, ...]] = (
    MCPAuth.oauth2,
    MCPAuth.true_passthrough,
    MCPAuth.oauth_delegate,
)


_MCP_OAUTH_DISCOVERY_ON_STARTUP_ENV: Final = "LITELLM_MCP_OAUTH_DISCOVERY_ON_STARTUP"
_TRUE_ENV_VALUES: Final = frozenset(("1", "true", "yes", "on"))
_OAUTH_DISCOVERY_RETRY_DELAYS_SECONDS: Final = (0.05, 0.15)
_OAUTH_DISCOVERY_RETRY_BASE_SECONDS: Final = 30.0
_OAUTH_DISCOVERY_RETRY_MAX_SECONDS: Final = 900.0


def _oauth_discovery_now() -> float:
    return time.monotonic()


def _oauth_discovery_retry_delay(consecutive_failures: int) -> float:
    backoff_multiplier: Final[int] = 1 << max(consecutive_failures - 1, 0)
    return min(
        _OAUTH_DISCOVERY_RETRY_BASE_SECONDS * backoff_multiplier,
        _OAUTH_DISCOVERY_RETRY_MAX_SECONDS,
    )


def _mcp_oauth_discovery_on_startup_enabled() -> bool:
    """Return whether remote MCP OAuth metadata is discovered during registration.

    Discovery is deferred until the first admitted request unless explicitly
    enabled with ``1``, ``true``, ``yes``, or ``on``.
    """
    value: Final = os.getenv(_MCP_OAUTH_DISCOVERY_ON_STARTUP_ENV)
    return value is not None and value.strip().lower() in _TRUE_ENV_VALUES


def _requires_oauth_discovery(
    server_url: str | None,
    use_issuer_anchor: bool,
    server: MCPServer,
) -> bool:
    return _has_oauth_discovery_source(server_url, use_issuer_anchor) and _oauth_endpoints_unresolved(server)


_StringList: TypeAlias = list[str]
_StringMap: TypeAlias = dict[str, str]
_ToolParamMap: TypeAlias = dict[str, list[str]]
_EnvVarList: TypeAlias = list[dict[str, object]]
_InMemoryCacheDict: TypeAlias = dict[str, object]
_ToolArguments: TypeAlias = dict[str, object]


@dataclass(frozen=True, slots=True)
class _OAuthDiscoveryResolved:
    server: MCPServer


@dataclass(frozen=True, slots=True)
class _OAuthDiscoveryFailed:
    server_id: str
    timed_out: bool


@dataclass(frozen=True, slots=True)
class _OAuthDiscoveryStale:
    server_id: str


_OAuthDiscoveryOutcome: TypeAlias = _OAuthDiscoveryResolved | _OAuthDiscoveryFailed | _OAuthDiscoveryStale


@dataclass(frozen=True, slots=True)
class _OAuthDiscoverySlot:
    server_id: str
    generation: int
    task: asyncio.Task[_OAuthDiscoveryOutcome] | None = None
    consecutive_failures: int = 0
    retry_not_before: float = 0.0


class MCPServerConfig(TypedDict, total=False):
    """Shape of a single ``mcp_servers`` entry in config.yaml, as consumed by
    :meth:`MCPServerManager.load_servers_from_config`. Every key is optional: YAML supplies
    whatever the admin wrote, and each read applies its own default."""

    alias: str
    description: str
    mcp_info: MCPInfo
    url: str
    spec_path: str
    transport: MCPTransportType
    auth_type: MCPAuthType
    authentication_token: str
    auth_value: str
    instructions: str
    command: str
    args: _StringList
    env: _StringMap
    client_id: str
    client_secret: str
    oauth2_flow: str
    issuer: str
    authorization_url: str
    token_url: str
    registration_url: str
    token_endpoint_auth_method: MCPTokenEndpointAuthMethod
    scopes: str | Sequence[str]
    dcr_bridge: object
    extra_headers: _StringList
    allowed_tools: _StringList
    disallowed_tools: _StringList
    allowed_params: _ToolParamMap
    access_groups: _StringList
    static_headers: _StringMap
    env_vars: _EnvVarList
    allow_all_keys: bool
    available_on_public_internet: bool
    delegate_auth_to_upstream: bool
    oauth_passthrough: bool
    allow_sampling: bool
    allow_elicitation: bool
    aws_access_key_id: str
    aws_secret_access_key: str
    aws_session_token: str
    aws_region_name: str
    aws_service_name: str
    aws_role_name: str
    aws_session_name: str
    token_exchange_endpoint: str
    token_exchange_profile: str
    audience: str
    subject_token_type: str
    upstream_resource: str
    upstream_token_header: ReadOnly[str]
    id_jag_resource_token_endpoint: str
    id_jag_resource: str
    client_private_key: str
    client_private_key_id: str
    client_assertion_signing_alg: str
    timeout: float
    max_concurrent_requests: int


class _ProtectedResourceMetadataPayload(TypedDict, total=False):
    """The RFC 9728 protected-resource metadata document fields this gateway reads."""

    authorization_servers: Sequence[object]
    scopes_supported: Sequence[str]
    scopes: Sequence[str]


class _AuthorizationServerMetadataPayload(TypedDict, total=False):
    """The RFC 8414 / OpenID Discovery authorization-server metadata fields this gateway reads."""

    issuer: str
    authorization_endpoint: str
    token_endpoint: str
    registration_endpoint: str
    scopes_supported: Sequence[str]
    grant_types_supported: Sequence[str]
    token_endpoint_auth_methods_supported: Sequence[str]


def _blank_to_none(value: str | None) -> str | None:
    """Collapse an absent, empty, or whitespace-only string to ``None``.

    OAuth endpoint fields are consumed by truthiness-based merges (``row or discovered``) and by the
    corroboration gate. A whitespace-only value is truthy to ``or`` but is not a usable endpoint, so
    without this the merge would keep the blank value for redirects while the gate treats it as
    unpinned and backfills the other fields, yielding a broken half-discovered config. Normalizing
    the pinned fields once, at each build entry point, gives every downstream consumer a single
    notion of "blank" so those code paths cannot disagree.
    """
    if not isinstance(value, str):
        return None
    return value.strip() or None


def _uses_issuer_anchor(manual_issuer: str | None, is_discovery_auth_type: bool) -> bool:
    """Whether the endpoints are authoritatively anchored to an admin-pinned issuer (RFC 8414 §3.3).

    This is the trust/provenance property, distinct from whether the ``issuer`` field is merely
    populated: a trust-on-first-use discovered issuer sets ``issuer`` for token identity but is NOT
    anchored, so its endpoints stay resource-rooted. Anchoring holds only when the issuer was pinned
    (present on the row/config) on a discovery auth type. Every consumer of "is this anchored" reads
    this one definition, so the answer cannot diverge across build paths.
    """
    return _blank_to_none(manual_issuer) is not None and is_discovery_auth_type


def _has_oauth_discovery_source(server_url: str | None, use_issuer_anchor: bool) -> bool:
    """Whether the server has any source OAuth discovery can fetch metadata from.

    Resource-rooted discovery (RFC 9728) is fetched from the server ``url``, so spec-only
    (OpenAPI) and stdio servers, which have none, could never discover: their OAuth endpoints
    stayed unset unless entered manually and ``/authorize`` served its 400 with no hint of why.
    An admin-pinned issuer is a trust anchor in its own right (RFC 8414 section 3.3) whose
    metadata fetch does not touch the resource at all, so an anchored server can discover with
    no ``url``. Called by both build paths (config and DB) so the two cannot disagree on when
    discovery is reachable.
    """
    return bool(server_url) or use_issuer_anchor


def _endpoints_yield_to_issuer(
    issuer: str | None,
    is_discovery_auth_type: bool,
    authorization_url: str | None,
    token_url: str | None,
    registration_url: str | None,
    server_ref: str,
) -> tuple[str | None, str | None, str | None]:
    """The single rule that makes an admin-configured ``issuer`` the sole authoritative endpoint
    source (RFC 8414 §3.3): when it is set for a discovery auth type, the stored/manual
    ``authorization_url``/``token_url``/``registration_url`` do not apply. They neither anchor nor
    short-circuit discovery, never override the issuer document in the merge, and never substitute for
    it when the issuer fetch fails (fail-closed). Returns the endpoint values that remain in force,
    i.e. all ``None`` when issuer-anchored, else the inputs unchanged. Called at every resolution site
    so the invariant holds in one place instead of being re-derived per merge.
    """
    if issuer is None or not is_discovery_auth_type:
        return authorization_url, token_url, registration_url
    discarded: Final = sorted(
        label
        for label, value in (
            ("authorization_url", authorization_url),
            ("token_url", token_url),
            ("registration_url", registration_url),
        )
        if value
    )
    if discarded:
        verbose_logger.warning(
            "MCP server %s has a pinned Issuer, so its stored %s %s not used: an anchored issuer is the "
            "sole endpoint source (RFC 8414 section 3.3) and a failed issuer fetch fails closed rather "
            "than falling back to them. To use manually configured endpoints instead, clear the Issuer "
            "field and re-enter the endpoint urls (clearing the Issuer also clears endpoints that may "
            "have been resolved under it), or clear the Issuer alone to re-discover from the server url.",
            server_ref,
            ", ".join(discarded),
            "is" if len(discarded) == 1 else "are",
        )
    return None, None, None


def _normalized_authorize_endpoint(url: str) -> str:
    """Compare authorize endpoints / issuers on scheme, host, and path only, through the shared URL
    canonicalizer: the default port is elided and the host is lowercased so
    ``https://IDP.example.com:443/authorize/`` and ``https://idp.example.com/authorize`` are the same
    identity, while query, fragment and a trailing slash are dropped."""
    return canonicalize_url_identity(url)


def _issuer_matches(claimed_issuer: object, configured_issuer: str) -> bool:
    """RFC 8414 §3.3 issuer equality between the metadata document's self-attested ``issuer`` and the
    admin-configured issuer, tolerant only of URL-insignificant differences (scheme/host case, the
    default port, a trailing slash). A non-string or empty claimed issuer never matches, so a
    document that omits ``issuer`` fails closed under issuer-anchored discovery.
    """
    if not isinstance(claimed_issuer, str) or not claimed_issuer:
        return False
    return _normalized_authorize_endpoint(claimed_issuer) == _normalized_authorize_endpoint(configured_issuer)


def _flow_endpoints_missing(
    auth_type: MCPAuthType | None,
    oauth2_flow: str | None,
    authorization_url: str | None,
    token_url: str | None,
    token_exchange_endpoint: str | None = None,
) -> bool:
    """Whether a built server is missing an endpoint its flow needs to run at all.

    Used by the reload fast-path exemption: discovery runs at build time only, and the fast path
    reuses an unchanged row's registry entry verbatim, so a server whose discovery came back empty
    (transient upstream failure, rate limiting) would stay broken until some unrelated config write
    bumps ``updated_at``, serving its 400 the whole time. Rebuilding just these entries retries
    discovery on the normal reload cadence. It costs no extra fetch for servers that resolved, and
    none for those with no discovery source, since the build skips discovery for both.
    """
    if auth_type == MCPAuth.oauth2_token_exchange:
        # A configured exchange endpoint replaces discovery entirely; only a server that must
        # discover its token endpoint and still has none is unresolved.
        return token_exchange_endpoint is None and token_url is None
    if auth_type not in _UPSTREAM_OAUTH_DISCOVERY_AUTH_TYPES:
        return False
    if oauth2_flow == "client_credentials":
        return token_url is None
    return authorization_url is None or token_url is None


def _oauth_endpoints_unresolved(server: MCPServer) -> bool:
    """``_flow_endpoints_missing`` over a built registry entry, for the reload fast-path check.

    The flow comes from ``effective_oauth2_flow``, the one column-first, shape-fallback judge every
    flow decision uses, not from the raw column: a legacy row the startup backfill deliberately left
    unstamped (the ambiguous M2M shape) serves M2M at request time, and reading the bare column here
    would classify it as interactive-missing-endpoints and re-run discovery on every reload.
    """
    if (
        server.auth_type == MCPAuth.oauth2_token_exchange
        and server.token_exchange_profile == "entra_obo"
        and not server.scopes
    ):
        # entra_obo fails closed at exchange time without a scope (token_exchanger.py), and scopes
        # can come from resource discovery, so a server that resolved its endpoints but no scopes is
        # still unresolved for its flow.
        return True
    if server.is_dcr_bridge and not server.client_id and server.effective_registration_url is None:
        # A DCR bridge with no admin-configured client can only register callers through the
        # upstream's registration endpoint, so a build that resolved the authorize and token
        # endpoints but not registration_endpoint (partial metadata) is still unresolved for its
        # flow and must keep retrying; without this it silently degrades to the short-circuit arm
        # until an unrelated config write. Scopes are deliberately NOT part of completeness: they
        # are a request hint the authorization server bounds at consent (RFC 6749 section 3.3),
        # and a server without them is fully functional.
        return True
    return _flow_endpoints_missing(
        server.auth_type,
        MCPServerManager.effective_oauth2_flow(server),
        server.effective_authorization_url,
        server.effective_token_url,
        server.token_exchange_endpoint,
    )


def _endpoints_corroborate_authorization_url(
    source_authorization_url: str | None,
    trusted_authorization_url: str | None,
) -> bool:
    """Whether a source's ``token_url``/``registration_url`` may be paired with a trusted authorize
    endpoint. This is the single trust rule for adopting OAuth endpoints from any non-manual source.

    Discovery is rooted at the MCP resource (RFC 9728), so a compromised upstream can advertise an
    attacker-run authorization server. When ``authorization_url`` is admin-pinned, pairing it with a
    ``token_url`` from a different source is the RFC 9700 authorization-server mix-up: the user signs
    in at the trusted authorize endpoint while the gateway redeems the code, with the stored client
    secret and PKCE verifier, at the attacker's token endpoint. Endpoints are trustworthy together
    only when they share an authorization server, so a source's endpoints are adopted only when the
    same source advertised an ``authorization_endpoint`` matching the pinned value. With no pinned
    value (``trusted_authorization_url is None``) there is nothing to protect: the authorize endpoint
    comes from the same source as the token endpoint, so they corroborate each other by construction.
    """
    if not (trusted_authorization_url and trusted_authorization_url.strip()):
        return True
    return bool(source_authorization_url) and _normalized_authorize_endpoint(
        source_authorization_url
    ) == _normalized_authorize_endpoint(trusted_authorization_url)


def _carry_forward_resolved_oauth_endpoints(new_server: MCPServer, previous_server: MCPServer | None) -> None:
    """Keep the last known good OAuth endpoints when a rebuild's re-discovery comes back empty.

    A rebuild wholesale-replaces the registry entry, so without this a transient upstream outage
    during re-discovery downgrades a working server (``authorization_url`` set) to a broken one
    (``None``, /authorize 400s) with no configuration change. Mirrors the ``short_prefix``
    carry-forward. Skipped when the server's ``url`` or ``auth_type`` changed, since the previous
    endpoints may then belong to a different upstream. Discovery results live only on the in-memory
    registry entry; the gateway never writes them to the row, whose OAuth columns carry admin intent
    alone, so this carry is the sole last-known-good mechanism and restores exactly the values the
    previous build already ran with.

    Carry-forward is a non-manual endpoint source, so the same trust rule as discovery applies: the
    previous ``token_url``/``registration_url``/``scopes`` are carried only when the previous
    ``authorization_url`` corroborates the authorize endpoint this build will use, i.e. when the
    incoming build has no pinned authorize endpoint (``None`` -> we adopt the previous one too, a
    consistent group) or pins the same one. An admin re-pointing ``authorization_url`` to a different
    server must not keep serving the old server's token endpoint or granted scopes.

    When the server is issuer-anchored (``issuer_is_anchored`` -- a pinned issuer on a discovery auth
    type), the endpoints come solely from the §3.3-validated issuer document, so carry-forward is
    skipped entirely for its endpoints: a failed issuer fetch leaves them ``None`` and must stay
    ``None`` (fail-closed), never resurrected from the previous registry entry. A merely discovered
    (trust-on-first-use) issuer is NOT anchored -- ``issuer`` is set for token identity but the
    endpoints are resource-rooted, so they still carry forward as last-known-good, gated by the
    corroboration check below like any other resource-rooted server. Scopes stay resource-driven and
    can carry either way.
    """
    if previous_server is None:
        return
    if previous_server.url != new_server.url or previous_server.auth_type != new_server.auth_type:
        return
    if new_server.issuer_is_anchored:
        # Endpoints come solely from the §3.3-validated issuer document; a failed fetch stays
        # fail-closed and must not be resurrected from the previous entry. Only the resource-driven
        # scopes carry as last-known-good.
        if not new_server.scopes and previous_server.scopes:
            new_server.scopes = previous_server.scopes
        return
    may_carry: Final = _endpoints_corroborate_authorization_url(
        previous_server.authorization_url, new_server.authorization_url
    )
    if new_server.authorization_url is None and previous_server.authorization_url:
        new_server.authorization_url = previous_server.authorization_url
    if may_carry and new_server.token_url is None and previous_server.token_url:
        new_server.token_url = previous_server.token_url
    if may_carry and new_server.registration_url is None and previous_server.registration_url:
        new_server.registration_url = previous_server.registration_url
    if may_carry and not new_server.scopes and previous_server.scopes:
        new_server.scopes = previous_server.scopes


def _restrict_discovery_to_corroborated_authorization_server(
    metadata: MCPOAuthMetadata | None,
    manual_authorization_url: str | None,
    server_identifier: str,
    is_dcr_bridge: bool,
) -> MCPOAuthMetadata | None:
    """Reject discovered token/registration endpoints a manually pinned authorize endpoint cannot
    vouch for (the RFC 9700 authorization-server mix-up).

    Discovery is rooted at the MCP resource, so a compromised upstream can advertise an attacker
    ``token_endpoint``: with ``authorization_url`` admin-pinned but ``token_url`` blank, the merge
    would pair the trusted authorize endpoint with that attacker token endpoint, and the gateway would
    post the authorization code and client secret there. So the discovered ``token_url`` and
    ``registration_url`` are kept only if the document corroborates the pin (its
    ``authorization_endpoint`` matches). ``scopes`` are deliberately NOT gated here: per the MCP
    authorization spec Scope Selection Strategy and RFC 9700 §2.3, the scopes a client requests are
    resource-driven (the WWW-Authenticate challenge or the RFC 9728 protected-resource
    ``scopes_supported``), and scope inflation by a compromised resource is bounded by the
    authorization server and user consent (RFC 6749 §3.3), not by the client second-guessing the
    request. With no pin there is no trust anchor to protect, so discovery is returned as-is.
    """
    if metadata is None or not (manual_authorization_url and manual_authorization_url.strip()):
        return metadata
    if _endpoints_corroborate_authorization_url(metadata.authorization_url, manual_authorization_url):
        return metadata
    if not metadata.token_url and not metadata.registration_url:
        return metadata
    bridge_note: Final = (
        " The discovered registration_url is rejected with it, so this dcr_bridge server stays on the"
        " short-circuit registration arm."
        if is_dcr_bridge and metadata.registration_url
        else ""
    )
    verbose_logger.warning(
        "MCP OAuth discovery for server %s advertised authorization_endpoint %s, which does not match the "
        "manually configured authorization_url %s; rejecting the discovered token_url/registration_url so "
        "authorization codes and client credentials only follow the configured authorization server. "
        "Configure Token URL manually if the mismatch is intentional.%s",
        server_identifier,
        _normalized_authorize_endpoint(metadata.authorization_url) if metadata.authorization_url else "<absent>",
        _normalized_authorize_endpoint(manual_authorization_url),
        bridge_note,
    )
    return metadata.model_copy(update={"token_url": None, "registration_url": None})


def _redacted_origin_list(urls: Sequence[str]) -> str:
    return ", ".join(_redact_mcp_resource_url(url) or "<unparseable url>" for url in urls)


def _sanitized_error_text(exc: Exception) -> str:
    return re.sub(r"https?://\S+", "<url>", str(exc))[:200]


def _discovery_failure_leaves_needs_unresolved(
    *,
    needs_authorization_url: bool,
    needs_token_url: bool,
    manual_authorization_url: str | None,
    manual_token_url: str | None,
) -> bool:
    return (needs_authorization_url and not manual_authorization_url) or (needs_token_url and not manual_token_url)


def _warn_oauth_endpoints_unresolved(
    *,
    server_ref: str,
    server_url: str | None,
    discovery_attempted: bool,
    discovery_deferred: bool = False,
    issuer_anchored: bool,
    metadata: MCPOAuthMetadata | None,
    needs_authorization_url: bool,
    needs_token_url: bool,
    manual_authorization_url: str | None,
    manual_token_url: str | None,
) -> None:
    """Log one actionable warning when a server that depends on OAuth endpoint discovery finishes a
    build without the endpoints that its flows need (LIT-4658).

    This is the operator-facing signal for a misconfigured server url: discovery failures themselves
    are logged where they happen (``_descovery_metadata``), and this names WHICH server is affected,
    which endpoints stayed unresolved after manual configuration was considered, and the remedies.
    Scopes never trigger the warning on their own: scope-less metadata is normal for many servers and
    warning on it every rebuild would be noise. Callers own the per-flow policy of which endpoints
    are needed (client_credentials never needs authorization_url; OBO needs only token_url); the
    issuer-anchored arm is excluded here because it has its own RFC 8414 §3.3 warning.
    """
    if discovery_deferred or issuer_anchored:
        return
    unresolved: Final = tuple(
        field
        for field, needed, value in (
            (
                "authorization_url",
                needs_authorization_url,
                manual_authorization_url or (metadata.authorization_url if metadata else None),
            ),
            (
                "token_url",
                needs_token_url,
                manual_token_url or (metadata.token_url if metadata else None),
            ),
        )
        if needed and not value
    )
    if not unresolved:
        return
    if discovery_attempted:
        verbose_logger.warning(
            "MCP server %s: OAuth endpoint discovery left %s unresolved (server url origin: %s). OAuth flows "
            "that need them will fail with 'not configured' errors until they resolve. Check the preceding "
            "'MCP OAuth' log lines for why discovery failed, verify the configured server url, or set the "
            "unresolved endpoint urls manually, or set issuer to discover them from the identity provider "
            "(RFC 8414)",
            server_ref,
            ", ".join(unresolved),
            _redact_mcp_resource_url(server_url) or "<no url>",
        )
        return
    verbose_logger.warning(
        "MCP server %s uses OAuth but has no discovery source (no server url or pinned issuer), and %s not "
        "set manually. Set the missing endpoint urls on the server, or set issuer to discover them from the "
        "identity provider (RFC 8414)",
        server_ref,
        " and ".join(unresolved) + (" is" if len(unresolved) == 1 else " are"),
    )


def invalidate_user_env_vars_cache(user_id: str, server_id: str) -> None:
    """Drop a cached entry after the user stores or clears their env var values
    so the next request reads the fresh value instead of a stale one."""
    _user_env_vars_cache.pop((user_id, server_id), None)


def _write_user_env_vars_cache(user_id: str, server_id: str, values: dict[str, str]) -> None:
    cache_key: Final = (user_id, server_id)
    # Re-insert at the tail so eviction drops the oldest-written entry, not a
    # freshly refreshed one, and only sheds a single entry instead of wiping the
    # whole cache (which would stampede the DB).
    _user_env_vars_cache.pop(cache_key, None)
    if len(_user_env_vars_cache) >= _USER_ENV_VARS_CACHE_MAX_SIZE:
        _user_env_vars_cache.pop(next(iter(_user_env_vars_cache)), None)
    _user_env_vars_cache[cache_key] = (values, time.monotonic())


def _should_strip_caller_authorization(
    mcp_server: MCPServer,
    raw_headers: dict[str, str] | None,
    user_api_key_auth: UserAPIKeyAuth | None,
) -> bool:
    """Decide whether the caller's ``Authorization`` header must NOT be
    forwarded upstream when populating ``extra_headers`` for an MCP server.

    Centralized so ``_call_regular_mcp_tool`` (this module) and
    ``_prepare_mcp_server_headers`` (``server.py``) cannot drift apart on
    this security-sensitive decision.

    Strip rules:
    - **M2M (client_credentials) servers**: never forward the caller's
      ``Authorization`` — the proxy fetches its own upstream token.
    - **Migrated per-user OAuth (authorization_code) servers**: never forward
      the caller's ``Authorization`` — the v2 resolver injects the stored
      per-user token, so a caller-supplied bearer cannot override another
      user's stored credential. Delegate / pass-through keep forwarding it.
    - **OAuth pass-through servers**: strip when the ``Authorization``
      header is actually the LiteLLM API key — either because admission
      validated it (``user_api_key_auth.api_key`` is set) and the caller
      did NOT also supply ``x-litellm-api-key`` to disambiguate, or
      because the legacy ``user_api_key_auth is None`` call sites did
      not supply an explicit admission header.  In the anonymous /
      pass-through cold-start case (RFC 9728) the bearer in
      ``Authorization`` is the upstream OAuth token and must be
      forwarded, so we keep it.
    - **oauth_delegate servers**: admission always runs and there is no
      anonymous path, so the caller's separate ``Authorization`` is
      forwarded only when a distinct ``x-litellm-api-key`` carried
      admission. Without that header the ``Authorization`` *was* the
      admission credential — a virtual key, an IdP JWT, or an SSO / OIDC /
      session token whose ``api_key`` is ``None`` — and must never reach
      the upstream, so it is stripped regardless of the ``api_key`` value.
    """
    if mcp_server.auth_type == MCPAuth.oauth2_token_exchange:
        # OBO: the inbound Authorization is the subject token. It is exchanged at the IdP and only the
        # exchanged token is sent upstream, so the raw caller bearer must never be forwarded.
        return True
    if mcp_server.has_client_credentials:
        return True
    if mcp_server.auth_type == MCPAuth.oauth2 and to_server_spec(mcp_server) is not None:
        # Migrated per-user OAuth (authorization_code): the v2 resolver injects the
        # stored token, so a caller-forwarded Authorization must not be forwarded
        # upstream — it would override another user's stored credential. Delegate and
        # pass-through return None from to_server_spec and keep forwarding the bearer.
        return True
    if not (mcp_server.is_oauth_passthrough or mcp_server.is_oauth_delegate):
        return False

    normalized_raw_headers: Final = {str(k).lower(): v for k, v in (raw_headers or {}).items() if isinstance(k, str)}
    has_explicit_litellm_admission_header: Final = normalized_raw_headers.get("x-litellm-api-key") is not None
    if mcp_server.is_oauth_delegate:
        return not has_explicit_litellm_admission_header
    admission_consumed_authorization_as_litellm_key: Final = (
        user_api_key_auth is not None
        and bool(getattr(user_api_key_auth, "api_key", None))
        and not has_explicit_litellm_admission_header
    )
    return admission_consumed_authorization_as_litellm_key or (
        user_api_key_auth is None and not has_explicit_litellm_admission_header
    )


def _format_byok_openapi_auth_header(mcp_server: MCPServer, mcp_auth_header: str) -> str:
    """Format a raw BYOK credential for OpenAPI tool ``Authorization`` injection.

    A non-BYOK server short-circuits ``_resolve_byok_mcp_auth_header``, so the value here can also
    be the deprecated global ``x-mcp-auth``, which is a complete header value and would otherwise
    be given a second scheme.
    """
    if mcp_server.auth_type == MCPAuth.api_key:
        return f"ApiKey {strip_auth_scheme(mcp_auth_header, 'ApiKey')}"
    if mcp_server.auth_type == MCPAuth.basic:
        return f"Basic {strip_auth_scheme(mcp_auth_header, 'Basic')}"
    return f"Bearer {strip_auth_scheme(mcp_auth_header, 'Bearer')}"


def _openapi_forwarded_extra_headers(
    mcp_server: MCPServer,
    raw_headers: dict[str, str] | None,
    user_api_key_auth: UserAPIKeyAuth | None,
) -> dict[str, str] | None:
    if not mcp_server.extra_headers or not raw_headers:
        return None
    normalized_raw: Final = {str(k).lower(): v for k, v in raw_headers.items() if isinstance(k, str)}
    skip_caller_authorization: Final = _should_strip_caller_authorization(
        mcp_server=mcp_server,
        raw_headers=raw_headers,
        user_api_key_auth=user_api_key_auth,
    )
    forwarded: Final[dict[str, str]] = {}
    for header_name in mcp_server.extra_headers:
        if not isinstance(header_name, str):
            continue
        if skip_caller_authorization and header_name.lower() == "authorization":
            continue
        value = normalized_raw.get(header_name.lower())
        if value is not None:
            forwarded[header_name] = value
    return forwarded or None


def _resolve_openapi_tool_auth(
    mcp_server: MCPServer,
    mcp_auth_header: str | None,
    mcp_server_auth_headers: Mapping[str, str | dict[str, str]] | None,  # mutable-ok: sink shape
    raw_headers: dict[str, str] | None,  # mutable-ok: sink takes a concrete dict
    user_api_key_auth: UserAPIKeyAuth | None,
) -> tuple[str | None, dict[str, str] | None, str | dict[str, str] | None]:  # mutable-ok: sink shapes
    """The caller's upstream credential for one ``spec_path`` server, for both OpenAPI dispatch arms.

    A per-server ``x-mcp-{alias}-authorization`` wins over the deprecated global / BYOK
    ``mcp_auth_header``, the same precedence ``_call_regular_mcp_tool`` applies, so the OpenAPI and
    managed paths cannot disagree about which credential is authoritative. The two kinds are not
    interchangeable: a per-server value is already a complete header value and is forwarded verbatim,
    while a BYOK credential is a raw secret that takes the server's auth-type prefix. Formatting the
    former would ship ``Bearer Bearer <token>``.

    Returns the ``Authorization`` value to inject, the extra headers to forward, and the credential to
    hand ``resolve_openapi_upstream_auth``, whose passthrough arm reads it via
    ``_passthrough_token_from_mcp_auth_header``. The per-server Authorization travels only in the
    credential, never also in the forwarded headers, because the resolver pops Authorization out of
    those and would otherwise have two sources to reconcile.
    """
    forwarded: Final = _openapi_forwarded_extra_headers(mcp_server, raw_headers, user_api_key_auth)
    per_server: Final = (
        lookup_mcp_server_auth_in_headers(
            mcp_server_auth_headers,
            alias=mcp_server.alias,
            server_name=mcp_server.server_name,
        )
        if mcp_server_auth_headers
        else None
    )

    if isinstance(per_server, dict):
        authorization: Final = next((v for k, v in per_server.items() if k.lower() == "authorization"), None)
        merged: Final = merge_mcp_headers(
            extra_headers=forwarded, static_headers=without_header(per_server, DEFAULT_CREDENTIAL_HEADER)
        )
        if authorization is None:
            byok: Final = _format_byok_openapi_auth_header(mcp_server, mcp_auth_header) if mcp_auth_header else None
            return byok, merged, mcp_auth_header
        return authorization, merged, per_server
    if isinstance(per_server, str) and per_server:
        return per_server, forwarded, per_server
    if mcp_auth_header:
        return _format_byok_openapi_auth_header(mcp_server, mcp_auth_header), forwarded, mcp_auth_header
    return None, forwarded, None


async def _resolve_byok_mcp_auth_header(
    mcp_server: MCPServer,
    user_api_key_auth: UserAPIKeyAuth | None,
    mcp_auth_header: str | None,
) -> str | None:
    """Resolve BYOK credential for tool calls that bypass ``execute_mcp_tool``."""
    if not mcp_server.is_byok:
        return mcp_auth_header

    from litellm.proxy._experimental.mcp_server.server import (
        _check_byok_credential,
        _get_byok_credential,
    )

    if not mcp_auth_header:
        byok_cred: Final = await _get_byok_credential(mcp_server, user_api_key_auth)
        if byok_cred is None:
            raise HTTPException(
                status_code=401,
                detail={
                    "error": "byok_auth_required",
                    "server_id": mcp_server.server_id,
                    "server_name": mcp_server.server_name or mcp_server.name,
                    "message": (
                        "No stored credential found for this BYOK server. "
                        "Complete the OAuth authorization flow to provide your API key."
                    ),
                },
                headers={"WWW-Authenticate": 'Bearer resource_metadata="/.well-known/oauth-protected-resource"'},
            )
        return byok_cred

    await _check_byok_credential(mcp_server, user_api_key_auth)
    return mcp_auth_header


def _client_forwarded_authorization_headers(
    mcp_server: MCPServer,
    oauth2_headers: dict[str, str] | None,
    raw_headers: dict[str, str] | None,
    user_api_key_auth: UserAPIKeyAuth | None,
) -> dict[str, str] | None:
    """Egress headers for the client-forwarded-token modes (``true_passthrough`` / ``oauth_delegate``).

    Forwards the caller's ``Authorization`` to the upstream, stripped when
    ``_should_strip_caller_authorization`` says it was consumed as the LiteLLM admission key. Shared by
    ``_call_regular_mcp_tool`` and ``server.py``'s ``_prepare_mcp_server_headers`` so the two egress
    paths cannot drift, mirroring the ``_should_strip_caller_authorization`` split.
    """
    extra_headers: Final = oauth2_headers.copy() if oauth2_headers else None
    if extra_headers and _should_strip_caller_authorization(
        mcp_server=mcp_server,
        raw_headers=raw_headers,
        user_api_key_auth=user_api_key_auth,
    ):
        return without_header(extra_headers, DEFAULT_CREDENTIAL_HEADER)
    return extra_headers


def _take_forwarded_authorization(
    headers: dict[str, str] | None,
) -> tuple[str | None, dict[str, str] | None]:
    """Pop the ``Authorization`` value out of ``headers`` (case-insensitive), returning it with the
    remaining headers, so the passthrough resolver arm is the single Authorization source rather than
    the header also riding in ``extra_headers`` (which the resolved auth would then defer to)."""
    if not headers:
        return None, headers
    value: Final = next((v for k, v in headers.items() if k.lower() == "authorization"), None)
    return value, without_header(headers, DEFAULT_CREDENTIAL_HEADER)


def _passthrough_token_from_mcp_auth_header(
    mcp_auth_header: str | dict[str, str] | None,
) -> str | None:
    """The caller's per-server upstream credential for a passthrough-mode server, or None.

    Sourced from ``x-mcp-{alias}-authorization`` (string or per-header dict form) or the deprecated
    global ``x-mcp-auth`` fallback. Per-server headers are the multi-server shape: they bind one
    token to one server, so an aggregate scope with several passthrough-mode servers never replays
    a single credential across upstreams. The value is forwarded verbatim, so it must be the full
    header value (e.g. ``Bearer <upstream-token>``)."""
    if isinstance(mcp_auth_header, str):
        return mcp_auth_header or None
    if isinstance(mcp_auth_header, dict):
        return next((v for k, v in mcp_auth_header.items() if k.lower() == "authorization"), None)
    return None


async def _materialize_auth_headers(auth: httpx.Auth | None) -> dict[str, str] | None:
    """Extract the header a resolved ``httpx.Auth`` would set, as a plain dict, or None.

    OpenAPI tool closures egress through ``AsyncHTTPHandler`` methods that accept headers but no
    ``auth``, so a resolved credential must be materialized into a header value. Driving one step
    of the auth's own flow (against a throwaway request that is never sent) keeps this generic
    across every auth shape without per-class branching; ``header_name`` is the resolver-arm
    convention for "this auth sets a header" (``NoOpAuth`` has none and yields nothing to apply).
    The materialized value is point-in-time: flow behaviors past the first request, like the M2M
    one-shot 401 refetch, do not apply on this arm.
    """
    if auth is None:
        return None
    header_name: Final = getattr(auth, "header_name", None)
    if not isinstance(header_name, str) or not header_name:
        return None
    probe: Final = httpx.Request("GET", "http://localhost/")
    flow: Final = auth.async_auth_flow(probe)
    try:
        first_request: Final = await flow.__anext__()
    except StopAsyncIteration:
        return None
    finally:
        await flow.aclose()
    header_value: Final = first_request.headers.get(header_name)
    return {header_name: header_value} if header_value else None


def _consumes_caller_authorization(server: MCPServer) -> bool:
    """True when this server's egress forwards the caller's request-wide ``Authorization`` upstream:
    the client-forwarded token modes, legacy OAuth pass-through, and legacy upstream-delegated
    interactive oauth2. An unstamped oauth2 row (flow column not yet backfilled) reads as a consumer,
    which errs toward suppression — the fail-safe direction."""
    if server.is_true_passthrough or server.is_oauth_delegate or server.is_oauth_passthrough:
        return True
    return (
        server.auth_type == MCPAuth.oauth2
        and getattr(server, "delegate_auth_to_upstream", False) is True
        and not server.has_client_credentials
    )


_REGISTRY_DUMP_SECRET_FIELDS: Final = frozenset(
    {"authentication_token", "client_secret", "client_private_key", "aws_secret_access_key", "aws_session_token"}
)


def _redacted_registry_dump(servers: dict[str, MCPServer]) -> dict[str, dict[str, str]]:
    """A JSON-safe view of the server registry with credential fields masked, for debug logging.

    The registry holds long-lived secrets as plain strings (the static token, OAuth client secret,
    the ID-JAG signing key, AWS keys); dumping them verbatim hands the gateway's client identity to
    anyone who can read debug logs.
    """
    dumps: dict[str, dict[str, object]] = {server_id: server.model_dump() for server_id, server in servers.items()}
    return {
        server_id: {
            field: ("**REDACTED**" if field in _REGISTRY_DUMP_SECRET_FIELDS and value is not None else str(value))
            for field, value in dump.items()
        }
        for server_id, dump in dumps.items()
    }


def _to_server_spec_fail_closed(server: MCPServer) -> ServerSpec | None:
    """`to_server_spec`, except a half-configured `oauth2_id_jag` server refuses instead of deferring.

    ID-JAG has no v1 arm, so deferring to v1 would let `resolve_mcp_auth` honor a caller x-mcp-*
    override or fall through to the static `authentication_token`, both of which bypass the per-user
    identity assertion the mode promises. That is an operator misconfiguration, not a fallback.
    """
    spec: Final = to_server_spec(server)
    if spec is None and server.auth_type == MCPAuth.oauth2_id_jag:
        raise_public(
            CredError.of_misconfigured(
                "oauth2_id_jag requires token_exchange_endpoint, id_jag_resource_token_endpoint, "
                "client_id, and a client_secret or client_private_key; refusing to fall back to "
                "a static credential."
            )
        )
    return spec


def _caller_authorization_fans_out(
    server: MCPServer,
    scope_servers: list[MCPServer] | None,
) -> bool:
    """True when forwarding the caller's request-wide ``Authorization`` to ``server`` inside a
    listing fan-out would replay one credential against multiple upstreams: another server in the
    scope also consumes it (RFC 9700 cross-resource replay). ``scope_servers`` is None for
    explicitly-addressed operations (tool call, get_prompt, read_resource, single-server routes),
    where the client named the one target and the gateway is not choosing recipients."""
    if scope_servers is None:
        return False
    return any(
        other is not None and other.server_id != server.server_id and _consumes_caller_authorization(other)
        for other in scope_servers
    )


def _extract_upstream_auth_failure(
    exc: BaseException,
) -> tuple[int, str | None] | None:
    """The upstream 401/403 and its ``WWW-Authenticate`` header from the exception tree, or ``None``.

    Delegates to the shared traversal in ``faults`` so every consumer (tool listing,
    tool calls, the connect-time probe) selects the same response with the same deliberate order:
    explicit ``raise ... from`` causes first, ExceptionGroup members in raise order, the incidental
    ``__context__`` chain last. A response raised while handling the real failure can therefore never
    shadow the causal one."""
    return upstream_auth_challenge(exc)


def _obo_retry_applies(server: MCPServer, subject_token: str | None) -> bool:
    """Whether an upstream 401/403 should invalidate the minted credential and retry once.

    ``oauth2_token_exchange`` can only mint from an inbound subject token, so with no token there is
    nothing to re-mint and the plain single call is correct. ``oauth2_id_jag`` also sources its
    subject from the identity assertion stored for the user at SSO login, so it qualifies whether or
    not the caller presented a token of its own; gating it on the inbound token would leave a
    store-sourced bearer un-invalidated and replayed until its TTL.
    """
    if server.auth_type == MCPAuth.oauth2_id_jag:
        return True
    return server.auth_type == MCPAuth.oauth2_token_exchange and bool(subject_token)


def _warn_on_server_name_fields(
    *,
    server_id: str,
    alias: str | None,
    server_name: str | None,
):
    def _warn(field_name: str, value: str | None) -> None:
        if not value:
            return
        result: Final = validate_tool_name(value)
        if result.is_valid:
            return

        warning_text: Final = "; ".join(result.warnings) if result.warnings else "Validation failed"
        verbose_logger.warning(
            "MCP server '%s' has invalid %s '%s': %s",
            server_id,
            field_name,
            value,
            warning_text,
        )

    _warn("alias", alias)
    _warn("server_name", server_name)


def _warn_internal_delegate_pkce_if_applicable(server: MCPServer, *, source: str) -> None:
    """Surface internal + upstream PKCE delegate in logs for operators."""
    if server.auth_type != MCPAuth.oauth2:
        return
    if getattr(server, "delegate_auth_to_upstream", False) is not True:
        return
    if getattr(server, "available_on_public_internet", True):
        return
    if server.has_client_credentials:
        return
    label: Final = get_server_prefix(server)
    verbose_logger.warning(
        "MCP server %r (id=%s, source=%s): internal-only (available_on_public_internet=false) "
        "with delegate_auth_to_upstream=true. Anonymous callers can reach the upstream OAuth2 "
        "/authorize flow and complete PKCE without a LiteLLM API key session; ensure the "
        "upstream IdP and network enforce your access policy.",
        label,
        server.server_id,
        source,
    )


def _deserialize_json_dict(data: str | _StringMap | None) -> dict[str, str] | None:
    """
    Deserialize optional JSON mappings stored in the database.

    Accepts values kept as JSON strings or materialized dictionaries and
    returns None when the input is empty or cannot be decoded.
    """
    if not data:
        return None

    if isinstance(data, str):
        try:
            return json.loads(data)
        except (json.JSONDecodeError, TypeError):
            # If it's not valid JSON, return as-is (shouldn't happen but safety)
            return None
    else:
        # Already a dictionary
        return data


def _deserialize_json_list(data: object) -> list[dict[str, Any]] | None:
    """Deserialize a JSON array stored in the DB (``env_vars`` and friends).

    Returns ``None`` for empty / null / unparseable input. Accepts strings
    (raw JSON), already-materialized lists of dicts, and lists of Pydantic
    models (Prisma may hydrate a JSON column such as ``env_vars`` into
    ``MCPEnvVar`` objects); model entries are normalized to plain dicts so
    downstream consumers expecting ``List[Dict[str, Any]]`` validate.
    """
    if data is None or data == "" or data == []:
        return None
    if isinstance(data, str):
        try:
            parsed: Final[object] = json.loads(data)
        except (json.JSONDecodeError, TypeError):
            return None
        data = parsed
    if not isinstance(data, list):
        return None
    return [item.model_dump(mode="json") if hasattr(item, "model_dump") else item for item in data]


def _normalize_mcp_server_cost_info(mcp_info: MCPInfo) -> None:
    """Coerce ``mcp_server_cost_info`` numeric fields to ``float`` at ingest.

    YAML 1.1 parses scientific notation without a decimal point (e.g.
    ``7e-05``) as a string, and ``MCPServerCostInfo`` is a TypedDict with no
    runtime validation, so string-typed costs flow through to the UI and
    crash its ``.toFixed`` formatting. Values that cannot be coerced are
    dropped with a warning instead of failing the server load.
    """
    cost_info: Final = mcp_info.get("mcp_server_cost_info")
    if not isinstance(cost_info, dict):
        return

    server_name: Final = mcp_info.get("server_name")
    normalized: Final = dict(cost_info)

    default_cost: Final = normalized.get("default_cost_per_query")
    if default_cost is not None:
        try:
            normalized["default_cost_per_query"] = float(default_cost)
        except (TypeError, ValueError):
            verbose_logger.warning(
                "MCP server '%s' has non-numeric default_cost_per_query %r; ignoring it",
                server_name,
                default_cost,
            )
            del normalized["default_cost_per_query"]

    tool_costs: Final = normalized.get("tool_name_to_cost_per_query")
    if isinstance(tool_costs, dict):
        normalized_tool_costs: Final = {}
        for tool_name, cost in tool_costs.items():
            try:
                normalized_tool_costs[tool_name] = float(cost)
            except (TypeError, ValueError):
                verbose_logger.warning(
                    "MCP server '%s' has non-numeric cost %r for tool '%s'; ignoring it",
                    server_name,
                    cost,
                    tool_name,
                )
        normalized["tool_name_to_cost_per_query"] = normalized_tool_costs

    mcp_info["mcp_server_cost_info"] = normalized


def _create_sampling_callback(user_api_key_auth: UserAPIKeyAuth | None = None):
    """
    Create a sampling callback for MCP ClientSession.
    Returns a callable that handles sampling/createMessage requests from
    upstream MCP servers by routing them through litellm.acompletion().
    """
    if not MCP_SAMPLING_AVAILABLE:
        return None

    async def _sampling_callback(
        context: "RequestContext[ClientSession, object]",
        params: "CreateMessageRequestParams",
    ):
        import litellm
        from litellm.proxy._experimental.mcp_server.sampling_handler import (
            handle_sampling_create_message,
        )
        from litellm.proxy._experimental.mcp_server.server import (
            get_active_auth_context,
        )

        auth_context: Final = get_active_auth_context()
        resolved_auth: Final = user_api_key_auth or (auth_context.user_api_key_auth if auth_context else None)
        # Forward original HTTP headers and client IP so that
        # header-dependent guardrails, tag-based routing, trace
        # correlation, and forward_llm_provider_auth_headers work
        # correctly for sampling sub-calls.
        _raw_headers: Final = getattr(auth_context, "raw_headers", None)
        _client_ip: Final = getattr(auth_context, "client_ip", None)

        return await handle_sampling_create_message(
            context=context,
            params=params,
            default_model=getattr(litellm, "default_mcp_sampling_model", None),
            user_api_key_auth=resolved_auth,
            raw_headers=_raw_headers,
            client_ip=_client_ip,
        )

    return _sampling_callback


def _create_elicitation_callback():
    """
    Create an elicitation callback for MCP ClientSession.
    Returns a callable that handles elicitation/create requests from
    upstream MCP servers. In gateway mode, this relays to the downstream
    client; in tool bridge mode, it returns a decline response.
    """
    if not MCP_ELICITATION_AVAILABLE:
        return None

    async def _elicitation_callback(context, params):
        from litellm.proxy._experimental.mcp_server.elicitation_handler import (
            handle_elicitation_request,
        )
        from litellm.proxy._experimental.mcp_server.server import get_active_mcp_session

        # In Gateway mode, we relay the elicitation request to the downstream client
        # that triggered the current operation.
        downstream_session: Final = get_active_mcp_session()
        downstream_capabilities = getattr(downstream_session, "capabilities", None) if downstream_session else None

        return await handle_elicitation_request(
            context=context,
            params=params,
            downstream_session=downstream_session,
            downstream_capabilities=downstream_capabilities,
        )

    return _elicitation_callback


def _record_mcp_guardrail_evaluations(
    synthetic_llm_data: dict[str, Any],  # mutable-ok: `_sync_guardrail_info_to_logging_obj` takes a concrete dict
    litellm_logging_obj: "LiteLLMLoggingObj | None",
) -> None:
    """Bridge guardrail decision records off an MCP synthetic request onto the request's logger.

    MCP guardrails run against a throwaway LLM-shaped dict from
    ``ProxyLogging._convert_mcp_to_llm_format``, so ``@log_guardrail_information``
    files ``standard_logging_guardrail_information`` in that dict's metadata bucket,
    which ``get_standard_logging_object_payload`` never reads. Native (non-unified)
    guardrails receive no ``logging_obj`` kwarg, so the decorator cannot bridge on
    their behalf; this calls the same helper it would have.

    Only the decision records move. The synthetic request's messages and tool
    arguments stay behind: they can carry end-user data, and the monitor needs none
    of it.
    """
    if litellm_logging_obj is None:
        return

    try:
        _sync_guardrail_info_to_logging_obj(synthetic_llm_data, litellm_logging_obj)
    except Exception as e:  # noqa: BLE001  # callers run this from a `finally` on the block path
        # The breadth is the point. Narrowing to the knowable AttributeError/TypeError
        # would let an unexpected type escape that ``finally`` and replace the guardrail's
        # block with a bookkeeping error.
        verbose_logger.warning("Failed to record MCP guardrail evaluation for logging: %s", e)


class MCPServerManager:
    _STDIO_ENV_TEMPLATE_PATTERN = re.compile(r"^\$\{(X-[^}]+)\}$")

    @staticmethod
    def _explicit_oauth2_flow(
        oauth2_flow: str | None,
    ) -> Literal["client_credentials", "authorization_code"] | None:
        """DB rows persist their flow (write-time stamps plus the startup backfill) and
        config servers must declare it (validated at load), so both builds read the
        value verbatim: unknown or null resolves to None, which
        ``needs_user_oauth_token`` already treats as interactive. Field-shape inference
        survives only in the request-time security helpers (``effective_oauth2_flow`` /
        ``resolve_oauth2_flow_for_request``).
        """
        if oauth2_flow in ("client_credentials", "authorization_code"):
            return cast(Literal["client_credentials", "authorization_code"], oauth2_flow)
        return None

    @staticmethod
    def _resolve_oauth2_flow(
        *,
        auth_type: MCPAuthType | None,
        oauth2_flow: str | None,
        token_url: str | None,
        authorization_url: str | None,
        client_id: str | None,
        client_secret: str | None,
    ) -> Literal["client_credentials", "authorization_code"] | None:
        """Infer oauth2_flow from field shape when the value is omitted.

        SECURITY-SENSITIVE: this is the shape-inference engine both request-time security
        helpers delegate to, so it is what decides M2M-vs-interactive for an unstamped row.
        Always access it through ``effective_oauth2_flow`` (boolean/enum decisions) or
        ``resolve_oauth2_flow_for_request`` (the egress object backstop), which are the single
        choke points for request-time resolution; do not call it directly from security sites
        and do not weaken its M2M-shape branch without accounting for those callers. DB rows
        are stamped at write time and by the startup backfill, config servers must declare
        oauth2_flow (validated at load), and both builds read the value verbatim via
        ``_explicit_oauth2_flow``. Delete this whole request-time layer only once the backstop
        warning stays silent in production.
        """
        if oauth2_flow in ("client_credentials", "authorization_code"):
            return cast(Literal["client_credentials", "authorization_code"], oauth2_flow)
        if oauth2_flow:
            # Ignore unknown/untyped values and continue legacy inference.
            return None
        if auth_type != MCPAuth.oauth2:
            return None
        if authorization_url:
            return None
        if token_url and client_id and client_secret:
            return "client_credentials"
        return None

    @staticmethod
    def effective_oauth2_flow(server: "MCPServer") -> Literal["client_credentials", "authorization_code"] | None:
        """The oauth2_flow a security decision must use for ``server`` this request.

        Column-first, shape-fallback: a stamped row returns its explicit value; an
        unstamped (null) row whose fields carry the M2M shape resolves to
        ``client_credentials`` so it is treated as M2M and fails closed. Every
        security-sensitive reader (anonymous-delegate allowlist and gate, egress flow
        resolution) goes through this one helper rather than reading the bare
        ``has_client_credentials`` column, which is unreliable for null rows.
        """
        return MCPServerManager._resolve_oauth2_flow(
            auth_type=server.auth_type,
            oauth2_flow=server.oauth2_flow,
            token_url=server.token_url,
            authorization_url=server.authorization_url,
            client_id=server.client_id,
            client_secret=server.client_secret,
        )

    @staticmethod
    def resolve_oauth2_flow_for_request(server: "MCPServer") -> "MCPServer":
        """Return ``server`` with its effective oauth2_flow applied, for egress paths.

        A stamped row is returned unchanged (its effective flow equals the stored value).
        An unstamped M2M-shape row is returned as a per-request copy carrying
        ``oauth2_flow=client_credentials`` so downstream ``has_client_credentials`` /
        ``needs_user_oauth_token`` compute correctly and the stored client credentials are
        used instead of forwarding the caller's Authorization. Use this at every point that
        resolves an allowed server id into an ``MCPServer`` for a tool call or listing.
        """
        effective: Final = MCPServerManager.effective_oauth2_flow(server)
        if effective is None or effective == server.oauth2_flow:
            return server
        verbose_logger.warning(
            "MCP server %s has no persisted oauth2_flow but matches the %s shape; using the "
            "inferred flow for this request. The startup backfill leaves this ambiguous M2M "
            "shape unstamped on purpose, so it will NOT self-heal: set oauth2_flow explicitly "
            "in the dashboard or via PUT /v1/mcp/server (client_credentials for M2M, or "
            "authorization_code after an interactive sign-in).",
            server.server_id,
            effective,
        )
        return server.model_copy(update={"oauth2_flow": effective})

    @staticmethod
    def _obo_needs_endpoint_discovery(
        auth_type: MCPAuthType | None,
        token_exchange_endpoint: str | None,
        token_url: str | None,
    ) -> bool:
        """An ``oauth2_token_exchange`` server with no configured token endpoint can have it
        discovered (RFC 9728 -> RFC 8414) the same way the ``oauth2`` flow already does; an explicitly
        configured ``token_exchange_endpoint``/``token_url`` wins and skips the discovery round-trip.
        """
        return auth_type == MCPAuth.oauth2_token_exchange and not (token_exchange_endpoint or token_url)

    def __init__(
        self,
        cred_provider: UpstreamCredentialProvider | None = None,
        per_user_oauth_token_store: InvalidatableOAuthTokenStore | None = None,
        per_user_token_cache: MCPPerUserTokenCache | None = None,
    ):
        self._per_user_oauth_token_store = per_user_oauth_token_store or LazyPerUserOAuthTokenStore(
            self.get_mcp_server_by_id
        )
        self._per_user_token_cache = per_user_token_cache or mcp_per_user_token_cache
        self._cred_provider = cred_provider or UpstreamCredentialProvider(
            oauth_token_store=self._per_user_oauth_token_store,
            token_exchanger=build_token_exchanger(),
        )
        self.registry: dict[str, MCPServer] = {}
        self.config_mcp_servers: dict[str, MCPServer] = {}
        """
        eg.
        [
            "server-1": {
                "name": "zapier_mcp_server",
                "url": "https://actions.zapier.com/mcp/<your-api-key>/sse"
                "transport": "sse",
                "auth_type": "api_key"
            },
            "uuid-2": {
                "name": "google_drive_mcp_server",
                "url": "https://actions.zapier.com/mcp/<your-api-key>/sse"
            }
        ]
        """

        # Per-server outbound tool-call concurrency limiters, lazily created from
        # each server's max_concurrent_requests. Keyed by server_id so the cap
        # survives the registry atomic-swap on config reload; a missing key means
        # the server has no configured limit. The limit is cached alongside the
        # semaphore so an edited limit rebuilds it instead of keeping the old cap
        # until restart.
        self._server_call_semaphores: dict[str, tuple[int, asyncio.Semaphore]] = {}
        self.tool_name_to_mcp_server_name_mapping: dict[str, str] = {}
        """
        {
            "gmail_send_email": "zapier_mcp_server",
        }
        """
        self._upstream_initialize_instructions_by_server_id: dict[str, str] = {}
        # Per-server monotonic timestamp of last upstream prefetch attempt (success,
        # empty result, or failure). Used to throttle re-probes for servers that do
        # not return instructions, and to apply a short cooldown after failures.
        self._upstream_initialize_instructions_probed_at: dict[str, float] = {}
        self._oauth_discovery_on_startup = _mcp_oauth_discovery_on_startup_enabled()
        self._oauth_discovery_generation_counter = 0
        self._oauth_discovery_slots: tuple[_OAuthDiscoverySlot, ...] = ()

    def _oauth_discovery_slot(self, server_id: str) -> _OAuthDiscoverySlot | None:
        return next((slot for slot in self._oauth_discovery_slots if slot.server_id == server_id), None)

    def _remove_oauth_discovery_slot(self, server_id: str) -> None:
        self._oauth_discovery_slots = tuple(slot for slot in self._oauth_discovery_slots if slot.server_id != server_id)

    def _store_oauth_discovery_slot(self, slot: _OAuthDiscoverySlot) -> None:
        self._oauth_discovery_slots = (
            *(existing for existing in self._oauth_discovery_slots if existing.server_id != slot.server_id),
            slot,
        )

    def _set_oauth_discovery_deferred(self, server_id: str, discovery_deferred: bool) -> None:
        previous: Final = self._oauth_discovery_slot(server_id)
        self._remove_oauth_discovery_slot(server_id)
        if previous is not None and previous.task is not None and not previous.task.done():
            previous.task.cancel()
        if discovery_deferred:
            self._oauth_discovery_generation_counter += 1
            self._store_oauth_discovery_slot(
                _OAuthDiscoverySlot(
                    server_id=server_id,
                    generation=self._oauth_discovery_generation_counter,
                )
            )

    def _invalidate_oauth_discovery_state(self, server_id: str) -> None:
        previous: Final = self._oauth_discovery_slot(server_id)
        self._remove_oauth_discovery_slot(server_id)
        if previous is not None and previous.task is not None and not previous.task.done():
            previous.task.cancel()

    def _registered_server(self, server: MCPServer) -> MCPServer:
        return self.registry.get(server.server_id) or self.config_mcp_servers.get(server.server_id) or server

    async def _discover_oauth_metadata_for_server(self, server: MCPServer) -> MCPOAuthMetadata | None:
        manual_issuer: Final = _blank_to_none(server.issuer)
        manual_authorization_url: Final = _blank_to_none(server.authorization_url)
        manual_token_url: Final = _blank_to_none(server.token_url)
        is_discovery_auth_type: Final = server.auth_type in _UPSTREAM_OAUTH_DISCOVERY_AUTH_TYPES
        use_issuer_anchor: Final = server.issuer_is_anchored
        obo_needs_discovery: Final = self._obo_needs_endpoint_discovery(
            server.auth_type,
            server.token_exchange_endpoint,
            manual_token_url,
        )
        needs_authorization_url: Final = is_discovery_auth_type and server.oauth2_flow != "client_credentials"
        needs_token_url: Final = is_discovery_auth_type or obo_needs_discovery
        warn_on_empty_discovery: Final = _discovery_failure_leaves_needs_unresolved(
            needs_authorization_url=needs_authorization_url,
            needs_token_url=needs_token_url,
            manual_authorization_url=manual_authorization_url,
            manual_token_url=manual_token_url,
        )
        metadata: Final = await (
            self._fetch_issuer_anchored_oauth_metadata(manual_issuer, server.url)
            if use_issuer_anchor and manual_issuer is not None
            else self._descovery_metadata(
                server_url=server.url or "",
                allow_origin_fallback=is_discovery_auth_type,
                warn_when_no_metadata=warn_on_empty_discovery,
            )
        )
        if use_issuer_anchor:
            return metadata
        gated_metadata: Final = (
            _restrict_discovery_to_corroborated_authorization_server(
                metadata,
                manual_authorization_url,
                server.server_id,
                server.is_dcr_bridge,
            )
            if is_discovery_auth_type
            else metadata
        )
        _warn_oauth_endpoints_unresolved(
            server_ref=server.alias or server.server_name or server.server_id,
            server_url=server.url,
            discovery_attempted=True,
            issuer_anchored=False,
            metadata=gated_metadata,
            needs_authorization_url=needs_authorization_url,
            needs_token_url=needs_token_url,
            manual_authorization_url=manual_authorization_url,
            manual_token_url=manual_token_url,
        )
        return gated_metadata

    @staticmethod
    def _merge_discovered_oauth_metadata(server: MCPServer, metadata: MCPOAuthMetadata | None) -> MCPServer:
        if metadata is None:
            return server
        discovered_issuer: Final = metadata.discovered_issuer if not metadata.from_origin_fallback else None
        resolved: Final = server.model_copy()
        resolved.scopes = server.scopes or metadata.scopes
        resolved.issuer = server.issuer or discovered_issuer
        resolved.authorization_url = server.authorization_url or metadata.authorization_url
        resolved.token_url = server.token_url or metadata.token_url
        resolved.registration_url = server.registration_url or metadata.registration_url
        return resolved

    def _oauth_discovery_slot_is_current(self, server_id: str, generation: int) -> bool:
        slot: Final = self._oauth_discovery_slot(server_id)
        return slot is not None and slot.generation == generation

    def _publish_resolved_oauth_server(
        self,
        server: MCPServer,
        generation: int,
    ) -> MCPServer | None:
        if not self._oauth_discovery_slot_is_current(server.server_id, generation):
            return None
        if server.server_id in self.registry:
            self.registry[server.server_id] = server
        elif server.server_id in self.config_mcp_servers:
            self.config_mcp_servers[server.server_id] = server
        else:
            return None
        self._remove_oauth_discovery_slot(server.server_id)
        return server

    async def _attempt_oauth_metadata_once(
        self,
        server: MCPServer,
        generation: int,
    ) -> _OAuthDiscoveryOutcome | None:
        if not self._oauth_discovery_slot_is_current(server.server_id, generation):
            return _OAuthDiscoveryStale(server_id=server.server_id)
        current: Final = self._registered_server(server)
        if not _oauth_endpoints_unresolved(current):
            published: Final = self._publish_resolved_oauth_server(current, generation)
            return (
                _OAuthDiscoveryResolved(server=published)
                if published is not None
                else _OAuthDiscoveryStale(server_id=server.server_id)
            )
        metadata: Final = await self._discover_oauth_metadata_for_server(current)
        if not self._oauth_discovery_slot_is_current(server.server_id, generation):
            return _OAuthDiscoveryStale(server_id=server.server_id)
        candidate: Final = self._merge_discovered_oauth_metadata(self._registered_server(server), metadata)
        if _oauth_endpoints_unresolved(candidate):
            return None
        published_candidate: Final = self._publish_resolved_oauth_server(candidate, generation)
        return (
            _OAuthDiscoveryResolved(server=published_candidate)
            if published_candidate is not None
            else _OAuthDiscoveryStale(server_id=server.server_id)
        )

    async def _attempt_oauth_metadata_resolution(
        self,
        server: MCPServer,
        generation: int,
        retry_delays: tuple[float, ...] = _OAUTH_DISCOVERY_RETRY_DELAYS_SECONDS,
    ) -> _OAuthDiscoveryOutcome:
        outcome: Final = await self._attempt_oauth_metadata_once(server, generation)
        if outcome is not None:
            return outcome
        if not retry_delays:
            return _OAuthDiscoveryFailed(server_id=server.server_id, timed_out=False)
        await asyncio.sleep(retry_delays[0])
        return await self._attempt_oauth_metadata_resolution(server, generation, retry_delays[1:])

    async def _run_oauth_metadata_resolution(
        self,
        server: MCPServer,
        generation: int,
    ) -> _OAuthDiscoveryOutcome:
        try:
            outcome: Final = await asyncio.wait_for(
                self._attempt_oauth_metadata_resolution(server, generation),
                timeout=MCP_METADATA_TIMEOUT,
            )
        except asyncio.TimeoutError:
            verbose_logger.warning(
                "Deferred MCP OAuth discovery timed out after %ss for server %s",
                MCP_METADATA_TIMEOUT,
                server.server_id,
            )
            failure: Final = _OAuthDiscoveryFailed(server_id=server.server_id, timed_out=True)
            self._record_oauth_discovery_failure(server.server_id, generation)
            return failure
        if isinstance(outcome, _OAuthDiscoveryFailed):
            self._record_oauth_discovery_failure(server.server_id, generation)
        return outcome

    def _record_oauth_discovery_failure(self, server_id: str, generation: int) -> None:
        slot: Final = self._oauth_discovery_slot(server_id)
        if slot is None or slot.generation != generation:
            return
        consecutive_failures: Final = slot.consecutive_failures + 1
        self._store_oauth_discovery_slot(
            replace(
                slot,
                consecutive_failures=consecutive_failures,
                retry_not_before=_oauth_discovery_now() + _oauth_discovery_retry_delay(consecutive_failures),
            )
        )

    def _get_or_start_oauth_discovery_task(
        self,
        server: MCPServer,
    ) -> tuple[asyncio.Task[_OAuthDiscoveryOutcome], int] | None:
        slot: Final = self._oauth_discovery_slot(server.server_id)
        if slot is None:
            return None
        if slot.task is not None:
            if not slot.task.done() or _oauth_discovery_now() < slot.retry_not_before:
                return slot.task, slot.generation
        task: Final = asyncio.create_task(
            self._run_oauth_metadata_resolution(self._registered_server(server), slot.generation)
        )
        self._store_oauth_discovery_slot(replace(slot, task=task))
        return task, slot.generation

    def prime_oauth_metadata_discovery(self, server: MCPServer) -> None:
        """Start best-effort OAuth metadata discovery for ``server``.

        The call returns immediately and never delays registration. It is a no-op
        when the server has no deferred discovery slot.

        Args:
            server: The registered MCP server to warm metadata for.
        """
        self._get_or_start_oauth_discovery_task(server)

    def _prime_oauth_metadata_discovery_for_servers(self, servers: Sequence[MCPServer]) -> None:
        for server in servers:
            self.prime_oauth_metadata_discovery(server)

    def _reconcile_oauth_discovery_slots_for_servers(self, servers: Sequence[MCPServer]) -> None:
        """Align retry slots after an atomic registry replacement."""
        for server in servers:
            should_defer = _requires_oauth_discovery(server.url, server.issuer_is_anchored, server)
            has_slot = self._oauth_discovery_slot(server.server_id) is not None
            if should_defer != has_slot:
                self._set_oauth_discovery_deferred(server.server_id, should_defer)

    async def ensure_oauth_metadata_discovered(self, server: MCPServer) -> MCPServer:
        """Join the bounded discovery task and return the resolved server.

        Concurrent callers share one task per server. A failed attempt remains
        retryable after a per-server cooldown.

        Args:
            server: The MCP server whose OAuth metadata must be resolved.

        Returns:
            The resolved server; the registered server when no discovery is
            pending, or when discovery failed for a client-forwarded-token
            server, whose session consumes no discovered endpoint.

        Raises:
            HTTPException: Status 503 when discovery times out or returns
                incomplete metadata for a server whose OAuth flow the gateway
                runs itself.
        """
        acquisition: Final = self._get_or_start_oauth_discovery_task(server)
        if acquisition is None:
            return self._registered_server(server)
        task, generation = acquisition
        try:
            outcome: Final = await asyncio.shield(task)
        except asyncio.CancelledError:
            if task.cancelled() and not self._oauth_discovery_slot_is_current(server.server_id, generation):
                return await self.ensure_oauth_metadata_discovered(server)
            raise
        match outcome:
            case _OAuthDiscoveryResolved(resolved_server):
                return resolved_server
            case _OAuthDiscoveryStale():
                return await self.ensure_oauth_metadata_discovered(server)
            case _OAuthDiscoveryFailed(timed_out=timed_out):
                current: Final = self._registered_server(server)
                if current.is_client_forwarded_token:
                    return current
                server_ref: Final = current.alias or current.server_name or current.name or current.server_id
                reason: Final = "timed out" if timed_out else "returned incomplete metadata"
                raise HTTPException(
                    status_code=503,
                    detail=f"OAuth metadata discovery {reason} for MCP server {server_ref!r}",
                )

    def _remember_upstream_initialize_instructions(self, server: MCPServer, client: MCPClient) -> None:
        raw: Final[str | None] = getattr(client, "_last_initialize_instructions", None)
        if raw and str(raw).strip():
            self._upstream_initialize_instructions_by_server_id[server.server_id] = str(raw).strip()

    async def _ensure_upstream_initialize_instructions_cached(self, server: MCPServer) -> None:
        """
        Open one upstream session and cache InitializeResult.instructions if missing.

        No-op when:
          - YAML/DB instructions are set on the server record,
          - server is OpenAPI (spec_path),
          - non-empty upstream instructions are already cached,
          - auth preconditions match health_check_server's skip rules
            (per-user auth / missing static auth token / static headers that
            reference a per-user env var),
          - a prior probe attempt for this server is within
            MCP_HEALTH_CHECK_TIMEOUT seconds (the probe is a health-check-shaped
            op and already uses this knob for its inner call timeout; reusing it
            as the cooldown avoids reconnecting on every gateway initialize when
            upstream returns empty or fails).
        """
        if server.spec_path:
            return
        if server.instructions and server.instructions.strip():
            return
        if self._upstream_initialize_instructions_by_server_id.get(server.server_id):
            return
        if server.requires_per_user_auth:
            return
        if self._references_per_user_env_var(server):
            return
        if (
            server.auth_type
            and server.auth_type != MCPAuth.none
            and server.auth_type != MCPAuth.aws_sigv4
            and not server.authentication_token
        ):
            return

        last_probed_at: Final = self._upstream_initialize_instructions_probed_at.get(server.server_id)
        if last_probed_at is not None and (time.monotonic() - last_probed_at) < MCP_HEALTH_CHECK_TIMEOUT:
            return

        # Record the attempt up-front so that a failure / empty response does not
        # cause every subsequent initialize request to re-open the upstream session.
        self._upstream_initialize_instructions_probed_at[server.server_id] = time.monotonic()

        try:
            resolved_static_headers: Final = await self._resolve_static_headers_with_env_vars(
                server=server,
                user_api_key_auth=None,
                raise_on_missing=False,
            )
            extra_headers: dict[str, str] | None = dict(resolved_static_headers) if resolved_static_headers else None
            client: Final = await self._create_mcp_client(
                server=server,
                mcp_auth_header=None,
                extra_headers=extra_headers,
                stdio_env=None,
            )

            async def _noop(_session):
                return "ok"

            await asyncio.wait_for(client.run_with_session(_noop), timeout=MCP_HEALTH_CHECK_TIMEOUT)
            self._remember_upstream_initialize_instructions(server, client)
        except Exception as e:
            verbose_logger.debug(
                "Upstream initialize instructions prefetch failed for %s: %s",
                server.name,
                e,
            )

    def get_registry(self) -> dict[str, MCPServer]:
        """
        Get the registered MCP Servers from the registry and union with the config MCP Servers
        """
        return self.config_mcp_servers | self.registry

    def is_config_declared_server(self, server_id: str) -> bool:
        """True when server_id was declared in config.yaml (present in the in-memory config map).
        Config servers are rowless and persistent, so their DCR client belongs in the server-scoped
        store; a rowless server that is NOT config-declared is a throwaway temp/session server whose
        client must not be persisted. This never overrides the row-existence check: a server that has
        a LiteLLM_MCPServerTable row is always resolved to that row first."""
        return server_id in self.config_mcp_servers

    async def load_servers_from_config(
        self,
        mcp_servers_config: dict[str, MCPServerConfig],
        mcp_aliases: dict[str, str] | None = None,
    ):
        """
        Load the MCP Servers from the config

        Args:
            mcp_servers_config: Dictionary of MCP server configurations
            mcp_aliases: Optional dictionary mapping aliases to server names from litellm_settings
        """
        verbose_logger.debug("Loading MCP Servers from config-----")
        self._upstream_initialize_instructions_by_server_id.clear()
        self._upstream_initialize_instructions_probed_at.clear()

        # Track which aliases have been used to ensure only first occurrence is used
        used_aliases: Final = set()

        for server_name, raw_server_config in mcp_servers_config.items():
            server_config: MCPServerConfig = raw_server_config
            validate_mcp_server_name(server_name)
            _mcp_info: MCPInfo = server_config.get("mcp_info", None) or {}
            # Preserve all custom fields from config while setting defaults for core fields
            mcp_info: MCPInfo = _mcp_info.copy()
            # Set default values for core fields if not present
            if "server_name" not in mcp_info:
                mcp_info["server_name"] = server_name
            if "description" not in mcp_info and server_config.get("description"):
                mcp_info["description"] = server_config.get("description")
            _normalize_mcp_server_cost_info(mcp_info)

            # Use alias for name if present, else server_name
            alias = server_config.get("alias", None)

            # Apply mcp_aliases mapping if provided
            if mcp_aliases and alias is None:
                # Check if this server_name has an alias in mcp_aliases
                for alias_name, target_server_name in mcp_aliases.items():
                    if target_server_name == server_name and alias_name not in used_aliases:
                        alias = alias_name
                        used_aliases.add(alias_name)
                        verbose_logger.debug("Mapped alias '%s' to server '%s'", alias_name, server_name)
                        break

            # Create a temporary server object to use with get_server_prefix utility
            temp_server = type(
                "TempServer",
                (),
                {"alias": alias, "server_name": server_name, "server_id": None},
            )()
            name_for_prefix = get_server_prefix(temp_server)

            server_url = server_config.get("url", None) or ""
            # Generate stable server ID based on parameters
            server_id = self._generate_stable_server_id(
                server_name=server_name,
                url=server_url,
                transport=server_config.get("transport", MCPTransport.http),
                auth_type=server_config.get("auth_type", None),
                alias=alias,
            )

            _warn_on_server_name_fields(
                server_id=server_id,
                alias=alias,
                server_name=server_name,
            )

            auth_type = server_config.get("auth_type", None)
            manual_issuer = _blank_to_none(server_config.get("issuer"))
            manual_authorization_url = _blank_to_none(server_config.get("authorization_url"))
            manual_token_url = _blank_to_none(server_config.get("token_url"))
            manual_registration_url = _blank_to_none(server_config.get("registration_url"))
            is_discovery_auth_type = auth_type in _UPSTREAM_OAUTH_DISCOVERY_AUTH_TYPES
            obo_needs_discovery = self._obo_needs_endpoint_discovery(
                auth_type,
                server_config.get("token_exchange_endpoint"),
                manual_token_url,
            )
            use_issuer_anchor = _uses_issuer_anchor(manual_issuer, is_discovery_auth_type or obo_needs_discovery)
            configured_authorization_url = manual_authorization_url
            configured_token_url = manual_token_url
            configured_registration_url = manual_registration_url
            manual_authorization_url, manual_token_url, manual_registration_url = _endpoints_yield_to_issuer(
                manual_issuer,
                is_discovery_auth_type,
                manual_authorization_url,
                manual_token_url,
                manual_registration_url,
                server_name or server_id,
            )
            should_discover = _has_oauth_discovery_source(server_url, use_issuer_anchor) and (
                is_discovery_auth_type or obo_needs_discovery
            )
            config_oauth2_flow = server_config.get("oauth2_flow", None)
            needs_authorization_url = is_discovery_auth_type and config_oauth2_flow != "client_credentials"
            needs_token_url = is_discovery_auth_type or obo_needs_discovery
            warn_on_empty_discovery = _discovery_failure_leaves_needs_unresolved(
                needs_authorization_url=needs_authorization_url,
                needs_token_url=needs_token_url,
                manual_authorization_url=manual_authorization_url,
                manual_token_url=manual_token_url,
            )
            discovery_deferred = should_discover and not self._oauth_discovery_on_startup
            if not should_discover or discovery_deferred:
                mcp_oauth_metadata = None
            elif use_issuer_anchor and manual_issuer is not None:
                mcp_oauth_metadata = await self._fetch_issuer_anchored_oauth_metadata(manual_issuer, server_url)
            else:
                mcp_oauth_metadata = await self._descovery_metadata(
                    server_url=server_url,
                    allow_origin_fallback=is_discovery_auth_type,
                    warn_when_no_metadata=warn_on_empty_discovery,
                )

            if use_issuer_anchor:
                gated_oauth_metadata = mcp_oauth_metadata
            elif is_discovery_auth_type:
                gated_oauth_metadata = _restrict_discovery_to_corroborated_authorization_server(
                    mcp_oauth_metadata,
                    manual_authorization_url,
                    server_name or server_id,
                    bool(server_config.get("dcr_bridge")),
                )
            else:
                gated_oauth_metadata = mcp_oauth_metadata

            # Filter blank scopes (e.g. YAML ``scopes: [""]``) the same way the DB-build path does, so
            # an all-blank list normalizes to None rather than a ``("",)`` tuple that skips the
            # entra_obo fail-closed scope precondition and POSTs an empty scope to the IdP.
            resolved_scopes = self._extract_scopes(server_config.get("scopes")) or (
                gated_oauth_metadata.scopes if gated_oauth_metadata else None
            )
            resolved_authorization_url = manual_authorization_url or (
                gated_oauth_metadata.authorization_url if gated_oauth_metadata else None
            )
            resolved_token_url = manual_token_url or (gated_oauth_metadata.token_url if gated_oauth_metadata else None)
            resolved_registration_url = manual_registration_url or (
                gated_oauth_metadata.registration_url if gated_oauth_metadata else None
            )
            discovered_issuer = (
                gated_oauth_metadata.discovered_issuer
                if gated_oauth_metadata and not gated_oauth_metadata.from_origin_fallback
                else None
            )
            effective_issuer = manual_issuer or discovered_issuer

            if auth_type == MCPAuth.oauth2 and config_oauth2_flow not in (
                "client_credentials",
                "authorization_code",
            ):
                raise ValueError(
                    f"Invalid config for MCP server '{server_name or server_id}': auth_type oauth2 "
                    f"requires an explicit oauth2_flow (got {config_oauth2_flow!r}). Set "
                    "oauth2_flow: client_credentials for machine-to-machine servers (the proxy mints "
                    "a shared token at token_url using client_id/client_secret, no user interaction) "
                    "or oauth2_flow: authorization_code for interactive servers (per-user tokens via "
                    "browser sign-in, including delegate_auth_to_upstream)."
                )

            config_dcr_bridge = server_config.get("dcr_bridge", None)
            if config_dcr_bridge is not None and not isinstance(config_dcr_bridge, bool):
                raise ValueError(
                    f"Invalid config for MCP server '{server_name or server_id}': dcr_bridge "
                    f"must be a boolean (got {config_dcr_bridge!r})."
                )
            if config_dcr_bridge and auth_type not in (
                MCPAuth.true_passthrough,
                MCPAuth.oauth_delegate,
            ):
                raise ValueError(
                    f"Invalid config for MCP server '{server_name or server_id}': dcr_bridge is only "
                    f"supported for auth_type true_passthrough or oauth_delegate (got {auth_type!r}). "
                    "The DCR bridge serves gateway-hosted OAuth discovery for the client-forwarded "
                    "token modes; interactive oauth2 servers already run the gateway "
                    "authorization-code flow."
                )

            _warn_oauth_endpoints_unresolved(
                server_ref=server_name or server_id,
                server_url=server_url,
                discovery_attempted=should_discover,
                discovery_deferred=discovery_deferred,
                issuer_anchored=use_issuer_anchor,
                metadata=gated_oauth_metadata,
                needs_authorization_url=needs_authorization_url,
                needs_token_url=needs_token_url,
                manual_authorization_url=manual_authorization_url,
                manual_token_url=manual_token_url,
            )

            new_server = MCPServer(
                server_id=server_id,
                name=name_for_prefix,
                alias=alias,
                server_name=server_name,
                spec_path=server_config.get("spec_path", None),
                url=server_url,
                command=server_config.get("command", None) or "",
                args=server_config.get("args", None) or [],
                env=server_config.get("env", None) or {},
                # oauth specific fields
                client_id=server_config.get("client_id", None),
                client_secret=server_config.get("client_secret", None),
                oauth2_flow=self._explicit_oauth2_flow(config_oauth2_flow),
                scopes=resolved_scopes,
                issuer=effective_issuer,
                issuer_is_anchored=use_issuer_anchor,
                authorization_url=resolved_authorization_url,
                token_url=resolved_token_url,
                registration_url=resolved_registration_url,
                configured_authorization_url=configured_authorization_url,
                configured_token_url=configured_token_url,
                configured_registration_url=configured_registration_url,
                token_endpoint_auth_method=server_config.get("token_endpoint_auth_method", None),
                # TODO: utility fn the default values
                transport=server_config.get("transport", MCPTransport.http),
                auth_type=auth_type,
                authentication_token=server_config.get("authentication_token", server_config.get("auth_value", None)),
                mcp_info=mcp_info,
                extra_headers=server_config.get("extra_headers", None),
                allowed_tools=server_config.get("allowed_tools", None),
                disallowed_tools=server_config.get("disallowed_tools", None),
                allowed_params=server_config.get("allowed_params", None),
                access_groups=server_config.get("access_groups", None),
                static_headers=server_config.get("static_headers", None),
                env_vars=server_config.get("env_vars", None),
                allow_all_keys=bool(server_config.get("allow_all_keys", False)),
                available_on_public_internet=bool(server_config.get("available_on_public_internet", True)),
                delegate_auth_to_upstream=bool(server_config.get("delegate_auth_to_upstream", False)),
                oauth_passthrough=bool(server_config.get("oauth_passthrough", False)),
                dcr_bridge=config_dcr_bridge,
                # AWS SigV4 fields
                aws_access_key_id=server_config.get("aws_access_key_id", None),
                aws_secret_access_key=server_config.get("aws_secret_access_key", None),
                aws_session_token=server_config.get("aws_session_token", None),
                aws_region_name=server_config.get("aws_region_name", None),
                aws_service_name=server_config.get("aws_service_name", None),
                aws_role_name=server_config.get("aws_role_name", None),
                aws_session_name=server_config.get("aws_session_name", None),
                instructions=server_config.get("instructions", None),
                # Token Exchange (OBO) fields
                token_exchange_endpoint=server_config.get("token_exchange_endpoint", None),
                audience=server_config.get("audience", None),
                subject_token_type=server_config.get(
                    "subject_token_type",
                    DEFAULT_SUBJECT_TOKEN_TYPE,
                ),
                upstream_resource=server_config.get("upstream_resource", None),
                upstream_token_header=server_config.get("upstream_token_header", None),
                # ID-JAG fields
                id_jag_resource_token_endpoint=server_config.get("id_jag_resource_token_endpoint", None),
                id_jag_resource=server_config.get("id_jag_resource", None),
                client_private_key=server_config.get("client_private_key", None),
                client_private_key_id=server_config.get("client_private_key_id", None),
                client_assertion_signing_alg=server_config.get("client_assertion_signing_alg", "RS256"),
                token_exchange_profile=server_config.get("token_exchange_profile", "rfc8693"),
                allow_sampling=bool(server_config.get("allow_sampling", False)),
                allow_elicitation=bool(server_config.get("allow_elicitation", False)),
                timeout=server_config.get("timeout", None),
                max_concurrent_requests=server_config.get("max_concurrent_requests", None),
            )
            self._assign_unique_short_prefix(new_server)
            _warn_internal_delegate_pkce_if_applicable(new_server, source="config")
            self.config_mcp_servers[server_id] = new_server
            self._set_oauth_discovery_deferred(
                server_id,
                _requires_oauth_discovery(server_url, use_issuer_anchor, new_server),
            )

            # Check if this is an OpenAPI-based server
            spec_path = server_config.get("spec_path", None)
            if spec_path:
                verbose_logger.info("Loading OpenAPI spec from %s for server %s", spec_path, server_name)
                await self._register_openapi_tools(
                    spec_path=spec_path,
                    server=new_server,
                    base_url=server_config.get("url", ""),
                )

        verbose_logger.debug(
            "Loaded MCP Servers: %s", json.dumps(_redacted_registry_dump(self.config_mcp_servers), indent=4)
        )

        await self._hydrate_config_servers_dcr_clients()

        self._prime_oauth_metadata_discovery_for_servers(tuple(self.config_mcp_servers.values()))

        self.initialize_tool_name_to_mcp_server_name_mapping()

    async def _hydrate_config_servers_dcr_clients(self) -> None:
        """Overlay each config-declared server's persisted DCR client (from the server-scoped
        store) onto its in-memory object so token refresh authenticates after a restart. A
        best-effort no-op when the DB is unreachable at config-load time."""
        from litellm.proxy._experimental.mcp_server.discoverable_endpoints import (  # noqa: PLC0415  # circular import
            hydrate_config_server_dcr_client,
        )

        for server in self.config_mcp_servers.values():
            try:
                if await hydrate_config_server_dcr_client(server):
                    verbose_logger.debug(
                        "hydrated persisted DCR client onto config MCP server server_id=%s",
                        server.server_id,
                    )
            except Exception as exc:  # noqa: BLE001  # best-effort hydration; never fail config load
                verbose_logger.debug(
                    "load_servers_from_config: failed to hydrate DCR client for server_id=%s: %s",
                    server.server_id,
                    exc,
                )

    async def _register_openapi_tools(self, spec_path: str, server: MCPServer, base_url: str):
        """
        Register tools from an OpenAPI specification for a given server.

        This creates "virtual" MCP tools from OpenAPI endpoints that are:
        1. Registered in the global tool registry with server prefix
        2. Mapped to the server for routing
        3. Executed via the local tool handler

        Args:
            spec_path: Path to the OpenAPI specification file
            server: The MCPServer instance to register tools for
            base_url: Base URL for API calls
        """
        from litellm.proxy._experimental.mcp_server.openapi_to_mcp_generator import (
            build_input_schema,
            create_tool_function,
            load_openapi_spec_async,
            resolve_operation_params,
        )
        from litellm.proxy._experimental.mcp_server.openapi_to_mcp_generator import (
            get_base_url as get_openapi_base_url,
        )
        from litellm.proxy._experimental.mcp_server.tool_registry import (
            global_mcp_tool_registry,
        )

        try:
            # Load OpenAPI spec (async to avoid "called from within a running event loop")
            spec: Final = await load_openapi_spec_async(spec_path)

            # Use base_url from config if provided, otherwise extract from spec
            if not base_url:
                base_url = get_openapi_base_url(spec, spec_path)
            verbose_logger.info("Registering OpenAPI tools for server %s with base URL: %s", server.name, base_url)

            # Get server prefix for tool naming
            server_prefix: Final = get_server_prefix(server)

            # Build headers from server configuration
            headers: dict[str, str] = {}

            # Add authentication headers if configured
            if server.authentication_token:
                from litellm.types.mcp import MCPAuth

                if server.auth_type == MCPAuth.bearer_token:
                    headers["Authorization"] = f"Bearer {server.authentication_token}"
                elif server.auth_type == MCPAuth.api_key:
                    headers["Authorization"] = f"ApiKey {server.authentication_token}"
                elif server.auth_type == MCPAuth.basic:
                    headers["Authorization"] = f"Basic {server.authentication_token}"
                elif server.auth_type == MCPAuth.token:
                    headers["Authorization"] = f"token {server.authentication_token}"

            # Add any static headers from server config.
            #
            # Note: `extra_headers` on MCPServer is a List[str] of header names to forward
            # from each client MCP request; values are applied at call time via
            # `_request_extra_headers` in server.py (not baked in here).
            # `static_headers` is a dict of concrete headers to always send.
            headers = (
                merge_mcp_headers(
                    extra_headers=headers,
                    static_headers=server.static_headers,
                )
                or {}
            )

            verbose_logger.debug(
                "Using headers for OpenAPI tools (excluding sensitive values): %s", list(headers.keys())
            )

            # Extract and register tools from OpenAPI paths
            paths: Final = spec.get("paths", {})
            components: Final = spec.get("components", {})
            registered_count = 0

            verbose_logger.debug("Processing %s paths from OpenAPI spec", len(paths))

            for path, path_item in paths.items():
                for method in ["get", "post", "put", "delete", "patch"]:
                    if method not in path_item:
                        continue

                    operation = path_item[method]

                    # Resolve $ref params and merge path-level params into the operation.
                    resolved_operation = resolve_operation_params(operation, path_item, components)

                    # Generate tool name (without prefix initially)
                    operation_id = operation.get("operationId", f"{method}_{path.replace('/', '_')}")
                    base_tool_name = openapi_tool_name(operation_id)

                    # Add server prefix to tool name
                    prefixed_tool_name = add_server_prefix_to_name(base_tool_name, server_prefix)

                    # Get description
                    description = operation.get(
                        "summary",
                        operation.get("description", f"{method.upper()} {path}"),
                    )

                    # Build input schema using imported function
                    input_schema = build_input_schema(resolved_operation)

                    # Create tool function with headers using imported function
                    tool_func = create_tool_function(
                        path,
                        method,
                        resolved_operation,
                        base_url,
                        headers=headers,
                        server_label=server.name or server.server_name or server.alias or server.server_id,
                        relays_upstream_auth=server.is_client_forwarded_token,
                    )
                    tool_func.__name__ = prefixed_tool_name
                    tool_func.__doc__ = description

                    # Register tool with prefixed name in global registry
                    global_mcp_tool_registry.register_tool(
                        name=prefixed_tool_name,
                        description=description,
                        input_schema=input_schema,
                        handler=tool_func,
                    )

                    # Update tool name to server name mapping (for both prefixed and base names)
                    self.tool_name_to_mcp_server_name_mapping[base_tool_name] = server_prefix
                    self.tool_name_to_mcp_server_name_mapping[prefixed_tool_name] = server_prefix

                    registered_count += 1
                    verbose_logger.debug("Registered OpenAPI tool: %s for server %s", prefixed_tool_name, server.name)

            verbose_logger.info("Successfully registered %s OpenAPI tools for server %s", registered_count, server.name)

        except Exception as e:
            verbose_logger.error("Failed to register OpenAPI tools for server %s: %s", server.name, e)
            raise e

    def _cleanup_server_tool_routing_artifacts(self, server: MCPServer) -> None:
        """Drop OpenAPI global tools and name-mapping rows owned by ``server``.

        When a server leaves ``self.registry`` (eviction, ``remove_server``, etc.),
        OpenAPI tools remain in ``global_mcp_tool_registry`` and
        ``tool_name_to_mcp_server_name_mapping`` unless removed here. Stale
        mappings make ``_get_mcp_server_from_tool_name`` resolve to a prefix that
        no longer exists in the live registry.
        """
        from litellm.proxy._experimental.mcp_server.tool_registry import (
            global_mcp_tool_registry,
        )

        prefix_root: Final = normalize_server_name(get_server_prefix(server))
        if server.spec_path and prefix_root:
            openapi_key_prefix: Final = prefix_root + MCP_TOOL_PREFIX_SEPARATOR
            global_mcp_tool_registry.unregister_tools_with_prefix(openapi_key_prefix)

        owned_normalized: Final = self._owned_mapping_values(server)

        stale_mapping_keys: Final = tuple(
            tool_name
            for tool_name, mapped_server in self.tool_name_to_mcp_server_name_mapping.items()
            if normalize_server_name(str(mapped_server)) in owned_normalized
        )

        for key in stale_mapping_keys:
            del self.tool_name_to_mcp_server_name_mapping[key]

    def _owned_mapping_values(self, server: MCPServer) -> frozenset[str]:
        return frozenset(
            normalize_server_name(value) for value in (*iter_known_server_prefixes(server), server.name) if value
        )

    def _server_exposes_tool(self, server: MCPServer, tool_name: str) -> bool:
        owned: Final = self._owned_mapping_values(server)
        mapped_owners: Final = (
            self.tool_name_to_mcp_server_name_mapping.get(spelling)
            for spelling in iter_known_tool_name_spellings(tool_name, server)
        )
        return any(owner is not None and normalize_server_name(owner) in owned for owner in mapped_owners)

    def remove_server(self, mcp_server: LiteLLM_MCPServerTable):
        """
        Remove a server from the registry
        """
        evicted: MCPServer | None = self.registry.pop(mcp_server.server_id, None)
        if evicted is None and mcp_server.server_name:
            evicted = self.registry.pop(mcp_server.server_name, None)
        if evicted is not None:
            verbose_logger.debug("Removed MCP Server: %s", mcp_server.server_id or mcp_server.server_name)
            self._cleanup_server_tool_routing_artifacts(evicted)
            self._invalidate_oauth_discovery_state(evicted.server_id)
        else:
            verbose_logger.warning("Server ID %s not found in registry", mcp_server.server_id)

    def _resolve_env_vars_list(
        self,
        mcp_server: LiteLLM_MCPServerTable,
        *,
        env_vars_are_encrypted: bool,
    ) -> _EnvVarList | None:
        env_vars_list: Final = _deserialize_json_list(getattr(mcp_server, "env_vars", None))
        if env_vars_are_encrypted:
            from litellm.proxy._experimental.mcp_server.db import (  # noqa: PLC0415
                decrypt_global_env_var_values,
            )

            decrypt_global_env_var_values(env_vars_list)
        return env_vars_list

    async def _resolve_table_oauth_metadata(
        self,
        *,
        mcp_server: LiteLLM_MCPServerTable,
        auth_type: MCPAuthType,
        server_url: str | None,
        manual_issuer: str | None,
        manual_authorization_url: str | None,
        manual_token_url: str | None,
        is_discovery_auth_type: bool,
        use_issuer_anchor: bool,
        scopes: list[str] | None,
        token_exchange_endpoint: str | None,
    ) -> tuple[MCPOAuthMetadata | None, bool]:
        obo_needs_discovery = self._obo_needs_endpoint_discovery(auth_type, token_exchange_endpoint, manual_token_url)
        needs_authorization_url: Final = (
            is_discovery_auth_type and getattr(mcp_server, "oauth2_flow", None) != "client_credentials"
        )
        needs_token_url: Final = is_discovery_auth_type or obo_needs_discovery
        warn_on_empty_discovery: Final = _discovery_failure_leaves_needs_unresolved(
            needs_authorization_url=needs_authorization_url,
            needs_token_url=needs_token_url,
            manual_authorization_url=manual_authorization_url,
            manual_token_url=manual_token_url,
        )
        has_all_upstream_oauth_fields: Final = bool(manual_authorization_url and manual_token_url and scopes)
        needs_discovery: Final = _has_oauth_discovery_source(server_url, use_issuer_anchor) and (
            (is_discovery_auth_type and not has_all_upstream_oauth_fields) or obo_needs_discovery
        )
        discovery_deferred: Final = needs_discovery and not self._oauth_discovery_on_startup
        if not needs_discovery or discovery_deferred:
            mcp_oauth_metadata: MCPOAuthMetadata | None = None
        elif use_issuer_anchor and manual_issuer is not None:
            mcp_oauth_metadata = await self._fetch_issuer_anchored_oauth_metadata(manual_issuer, server_url)
        else:
            mcp_oauth_metadata = await self._descovery_metadata(
                server_url=server_url,
                allow_origin_fallback=is_discovery_auth_type,
                warn_when_no_metadata=warn_on_empty_discovery,
            )
        if use_issuer_anchor:
            return mcp_oauth_metadata, discovery_deferred
        gated_metadata: Final = (
            _restrict_discovery_to_corroborated_authorization_server(
                mcp_oauth_metadata,
                manual_authorization_url,
                mcp_server.server_id,
                bool(getattr(mcp_server, "dcr_bridge", None)),
            )
            if is_discovery_auth_type
            else mcp_oauth_metadata
        )
        _warn_oauth_endpoints_unresolved(
            server_ref=mcp_server.alias or mcp_server.server_name or mcp_server.server_id,
            server_url=server_url,
            discovery_attempted=needs_discovery,
            discovery_deferred=discovery_deferred,
            issuer_anchored=False,
            metadata=gated_metadata,
            needs_authorization_url=needs_authorization_url,
            needs_token_url=needs_token_url,
            manual_authorization_url=manual_authorization_url,
            manual_token_url=manual_token_url,
        )
        return gated_metadata, discovery_deferred

    async def build_mcp_server_from_table(
        self,
        mcp_server: LiteLLM_MCPServerTable,
        *,
        credentials_are_encrypted: bool = True,
        env_vars_are_encrypted: bool | None = None,
    ) -> MCPServer:
        _mcp_info: Final[MCPInfo] = mcp_server.mcp_info or {}
        env_dict: Final = _deserialize_json_dict(getattr(mcp_server, "env", None))
        static_headers_dict: Final = _deserialize_json_dict(getattr(mcp_server, "static_headers", None))
        env_vars_list: Final = self._resolve_env_vars_list(
            mcp_server,
            env_vars_are_encrypted=(
                credentials_are_encrypted if env_vars_are_encrypted is None else env_vars_are_encrypted
            ),
        )
        credentials_dict: Final = _deserialize_json_dict(getattr(mcp_server, "credentials", None))

        encrypted_auth_value: str | None = None
        encrypted_client_id: str | None = None
        encrypted_client_secret: str | None = None
        if credentials_dict:
            encrypted_auth_value = credentials_dict.get("auth_value")
            encrypted_client_id = credentials_dict.get("client_id")
            encrypted_client_secret = credentials_dict.get("client_secret")

        auth_value: str | None = None
        if encrypted_auth_value:
            if credentials_are_encrypted:
                auth_value = decrypt_value_helper(
                    value=encrypted_auth_value,
                    key="auth_value",
                    exception_type="debug",
                    return_original_value=True,
                )
            else:
                auth_value = encrypted_auth_value

        client_id_value: str | None = None
        if encrypted_client_id:
            if credentials_are_encrypted:
                client_id_value = decrypt_value_helper(
                    value=encrypted_client_id,
                    key="client_id",
                    exception_type="debug",
                    return_original_value=True,
                )
            else:
                client_id_value = encrypted_client_id

        client_secret_value: str | None = None
        if encrypted_client_secret:
            if credentials_are_encrypted:
                client_secret_value = decrypt_value_helper(
                    value=encrypted_client_secret,
                    key="client_secret",
                    exception_type="debug",
                    return_original_value=True,
                )
            else:
                client_secret_value = encrypted_client_secret

        # AWS SigV4 credential fields
        aws_creds: Final = self._extract_aws_credentials(credentials_dict, credentials_are_encrypted)

        scopes: list[str] | None = None
        if credentials_dict:
            scopes_value: Final = credentials_dict.get("scopes")
            if scopes_value is not None:
                scopes = self._extract_scopes(scopes_value)

        name_for_prefix: Final = mcp_server.alias or mcp_server.server_name or mcp_server.server_id

        mcp_info: Final[MCPInfo] = _mcp_info.copy()
        if "server_name" not in mcp_info:
            mcp_info["server_name"] = mcp_server.server_name or mcp_server.server_id
        if "description" not in mcp_info and mcp_server.description:
            mcp_info["description"] = mcp_server.description
        _normalize_mcp_server_cost_info(mcp_info)

        auth_type: Final = cast(MCPAuthType, mcp_server.auth_type)
        server_url: Final = mcp_server.url
        manual_issuer: Final = _blank_to_none(mcp_server.issuer)
        manual_authorization_url = _blank_to_none(mcp_server.authorization_url)
        manual_token_url = _blank_to_none(mcp_server.token_url)
        manual_registration_url = _blank_to_none(mcp_server.registration_url)
        is_discovery_auth_type: Final = auth_type in _UPSTREAM_OAUTH_DISCOVERY_AUTH_TYPES
        token_exchange_endpoint: Final = mcp_server.token_exchange_endpoint or (
            credentials_dict.get("token_exchange_endpoint") if credentials_dict else None
        )
        use_issuer_anchor: Final = _uses_issuer_anchor(
            manual_issuer,
            is_discovery_auth_type
            or self._obo_needs_endpoint_discovery(auth_type, token_exchange_endpoint, manual_token_url),
        )
        configured_authorization_url: Final = manual_authorization_url
        configured_token_url: Final = manual_token_url
        configured_registration_url: Final = manual_registration_url
        manual_authorization_url, manual_token_url, manual_registration_url = _endpoints_yield_to_issuer(
            manual_issuer,
            is_discovery_auth_type,
            manual_authorization_url,
            manual_token_url,
            manual_registration_url,
            mcp_server.alias or mcp_server.server_name or mcp_server.server_id,
        )
        gated_oauth_metadata, _ = await self._resolve_table_oauth_metadata(
            mcp_server=mcp_server,
            auth_type=auth_type,
            server_url=server_url,
            manual_issuer=manual_issuer,
            manual_authorization_url=manual_authorization_url,
            manual_token_url=manual_token_url,
            is_discovery_auth_type=is_discovery_auth_type,
            use_issuer_anchor=use_issuer_anchor,
            scopes=scopes,
            token_exchange_endpoint=token_exchange_endpoint,
        )

        resolved_scopes: Final = scopes or (gated_oauth_metadata.scopes if gated_oauth_metadata else None)
        discovered_issuer: Final = (
            gated_oauth_metadata.discovered_issuer
            if gated_oauth_metadata and not gated_oauth_metadata.from_origin_fallback
            else None
        )
        effective_issuer: Final = manual_issuer or discovered_issuer

        new_server: Final = MCPServer(
            server_id=mcp_server.server_id,
            name=name_for_prefix,
            alias=getattr(mcp_server, "alias", None),
            server_name=getattr(mcp_server, "server_name", None),
            url=mcp_server.url,
            spec_path=getattr(mcp_server, "spec_path", None),
            transport=cast(MCPTransportType, mcp_server.transport),
            auth_type=auth_type,
            authentication_token=auth_value,
            mcp_info=mcp_info,
            extra_headers=getattr(mcp_server, "extra_headers", None),
            static_headers=static_headers_dict,
            env_vars=env_vars_list,
            client_id=client_id_value or getattr(mcp_server, "client_id", None),
            client_secret=client_secret_value or getattr(mcp_server, "client_secret", None),
            oauth2_flow=self._explicit_oauth2_flow(getattr(mcp_server, "oauth2_flow", None)),
            scopes=resolved_scopes,
            issuer=effective_issuer,
            issuer_is_anchored=use_issuer_anchor,
            authorization_url=manual_authorization_url or getattr(gated_oauth_metadata, "authorization_url", None),
            token_url=manual_token_url or getattr(gated_oauth_metadata, "token_url", None),
            registration_url=manual_registration_url or getattr(gated_oauth_metadata, "registration_url", None),
            configured_authorization_url=configured_authorization_url,
            configured_token_url=configured_token_url,
            configured_registration_url=configured_registration_url,
            token_endpoint_auth_method=(
                credentials_dict.get("token_endpoint_auth_method") if credentials_dict else None
            ),
            command=getattr(mcp_server, "command", None),
            args=getattr(mcp_server, "args", None) or [],
            env=env_dict,
            access_groups=getattr(mcp_server, "mcp_access_groups", None),
            allowed_tools=getattr(mcp_server, "allowed_tools", None),
            disallowed_tools=getattr(mcp_server, "disallowed_tools", None),
            allow_all_keys=mcp_server.allow_all_keys,
            available_on_public_internet=bool(getattr(mcp_server, "available_on_public_internet", True)),
            delegate_auth_to_upstream=bool(getattr(mcp_server, "delegate_auth_to_upstream", False)),
            oauth_passthrough=bool(getattr(mcp_server, "oauth_passthrough", False)),
            dcr_bridge=getattr(mcp_server, "dcr_bridge", None),
            created_at=getattr(mcp_server, "created_at", None),
            updated_at=getattr(mcp_server, "updated_at", None),
            tool_name_to_display_name=_deserialize_json_dict(getattr(mcp_server, "tool_name_to_display_name", None)),
            tool_name_to_description=_deserialize_json_dict(getattr(mcp_server, "tool_name_to_description", None)),
            is_byok=bool(getattr(mcp_server, "is_byok", False)),
            byok_description=getattr(mcp_server, "byok_description", None) or [],
            byok_api_key_help_url=getattr(mcp_server, "byok_api_key_help_url", None),
            source_url=getattr(mcp_server, "source_url", None),
            # AWS SigV4 fields
            aws_access_key_id=aws_creds.get("aws_access_key_id"),
            aws_secret_access_key=aws_creds.get("aws_secret_access_key"),
            aws_session_token=aws_creds.get("aws_session_token"),
            aws_region_name=aws_creds.get("aws_region_name"),
            aws_service_name=aws_creds.get("aws_service_name"),
            aws_role_name=aws_creds.get("aws_role_name"),
            aws_session_name=aws_creds.get("aws_session_name"),
            instructions=mcp_server.instructions,
            # Token exchange (OBO) fields: dedicated columns, with the credentials blob as a
            # back-compat fallback for servers persisted before the columns existed.
            token_exchange_endpoint=mcp_server.token_exchange_endpoint
            or (credentials_dict.get("token_exchange_endpoint") if credentials_dict else None),
            audience=mcp_server.audience or (credentials_dict.get("audience") if credentials_dict else None),
            subject_token_type=mcp_server.subject_token_type
            or (credentials_dict.get("subject_token_type") if credentials_dict else None)
            or DEFAULT_SUBJECT_TOKEN_TYPE,
            upstream_resource=(credentials_dict.get("upstream_resource") if credentials_dict else None),
            upstream_token_header=(credentials_dict.get("upstream_token_header") if credentials_dict else None),
            # ID-JAG fields — read from credentials JSON blob
            id_jag_resource_token_endpoint=(
                credentials_dict.get("id_jag_resource_token_endpoint") if credentials_dict else None
            ),
            id_jag_resource=(credentials_dict.get("id_jag_resource") if credentials_dict else None),
            client_private_key=self._decrypt_credential_field(
                credentials_dict.get("client_private_key") if credentials_dict else None,
                "client_private_key",
                credentials_are_encrypted,
            ),
            client_private_key_id=(credentials_dict.get("client_private_key_id") if credentials_dict else None),
            client_assertion_signing_alg=(
                credentials_dict.get("client_assertion_signing_alg") if credentials_dict else None
            )
            or "RS256",
            token_exchange_profile=mcp_server.token_exchange_profile
            or (credentials_dict.get("token_exchange_profile") if credentials_dict else None)
            or "rfc8693",
            timeout=getattr(mcp_server, "timeout", None),
            max_concurrent_requests=getattr(mcp_server, "max_concurrent_requests", None),
        )
        _warn_internal_delegate_pkce_if_applicable(new_server, source="database")
        self._set_oauth_discovery_deferred(
            new_server.server_id,
            _requires_oauth_discovery(server_url, use_issuer_anchor, new_server),
        )
        return new_server

    async def _maybe_register_openapi_tools(self, server: MCPServer, *, initialize_mapping: bool = True):
        """Register OpenAPI tools if the server has a spec_path configured."""
        if server.spec_path:
            verbose_logger.info("Loading OpenAPI spec from %s for server %s", server.spec_path, server.name)
            await self._register_openapi_tools(
                spec_path=server.spec_path,
                server=server,
                base_url=server.url or "",
            )
            if initialize_mapping:
                self.initialize_tool_name_to_mcp_server_name_mapping()

    async def add_server(self, mcp_server: LiteLLM_MCPServerTable):
        # The runtime registry is the allowlist for tool calls and health
        # probes (which spawn the underlying transport, including stdio
        # subprocesses). Match the eligibility set used by the bulk DB
        # filter in reload_servers_from_database() — NULL is legacy and
        # "approved" is a legacy alias for "active".
        if mcp_server.approval_status not in (None, "active", "approved"):
            return
        try:
            if mcp_server.server_id not in self.registry:
                # Callers hand us a record returned by the db.py read/write
                # helpers, which already decrypt global env var values (the
                # `credentials` field is the only one still encrypted here).
                # Re-decrypting plaintext would zero the values, so build with
                # env_vars_are_encrypted=False.
                new_server: Final = await self.build_mcp_server_from_table(mcp_server, env_vars_are_encrypted=False)
                self._assign_unique_short_prefix(new_server)
                self.registry[mcp_server.server_id] = new_server
                await self._maybe_register_openapi_tools(new_server)
                self.prime_oauth_metadata_discovery(new_server)
                verbose_logger.debug("Added MCP Server: %s", new_server.name)

        except Exception as e:
            verbose_logger.debug("Failed to add MCP server: %s", e)
            raise e

    async def update_server(self, mcp_server: LiteLLM_MCPServerTable):
        # If a previously-active server has been moved out of the active
        # state, evict any stale registry entry so subsequent tool calls and
        # health probes can't reach it.
        if mcp_server.approval_status not in (None, "active", "approved"):
            evicted = self.registry.pop(mcp_server.server_id, None)
            if evicted is None and mcp_server.server_name:
                evicted = self.registry.pop(mcp_server.server_name, None)
            if evicted is not None:
                self._cleanup_server_tool_routing_artifacts(evicted)
                self._invalidate_oauth_discovery_state(evicted.server_id)
            return
        try:
            if mcp_server.server_id in self.registry:
                # See add_server: db.py helpers already decrypted env var
                # values, so don't decrypt them a second time here.
                new_server: Final = await self.build_mcp_server_from_table(mcp_server, env_vars_are_encrypted=False)
                # Carry the previously-resolved short prefix across so the
                # tool names stay stable for clients holding cached lists.
                existing_prefix: Final = self.registry[mcp_server.server_id].short_prefix
                if existing_prefix and not new_server.short_prefix:
                    new_server.short_prefix = existing_prefix
                _carry_forward_resolved_oauth_endpoints(
                    new_server=new_server,
                    previous_server=self.registry[mcp_server.server_id],
                )
                self._assign_unique_short_prefix(new_server)
                self.registry[mcp_server.server_id] = new_server
                await self._maybe_register_openapi_tools(new_server)
                self.prime_oauth_metadata_discovery(new_server)
                verbose_logger.debug("Updated MCP Server: %s", new_server.name)

        except Exception as e:
            verbose_logger.debug("Failed to udpate MCP server: %s", e)
            raise e

    def get_all_mcp_server_ids(self) -> set[str]:
        """
        Get all MCP server IDs
        """
        all_servers: Final = list(self.get_registry().values())
        return {server.server_id for server in all_servers}

    def get_allow_all_keys_server_ids(self) -> list[str]:
        """Return server IDs that bypass per-key restrictions."""
        return [server.server_id for server in self.get_registry().values() if server.allow_all_keys is True]

    @staticmethod
    def get_byom_submitted_servers_cache_key(user_id: str) -> str:
        return f"byom_submitted_servers:{user_id}"

    async def invalidate_byom_submitted_servers_cache(self, user_id: str | None) -> None:
        if not user_id:
            return
        try:
            from litellm.proxy.proxy_server import user_api_key_cache

            await user_api_key_cache.async_delete_cache(key=self.get_byom_submitted_servers_cache_key(user_id))
        except Exception as e:  # noqa: BLE001
            verbose_logger.warning("Failed to invalidate BYOM submitted MCP server cache: %s", e)

    async def _get_active_submitted_mcp_server_ids_for_user(
        self, user_api_key_auth: UserAPIKeyAuth | None
    ) -> list[str]:
        submitter_user_id: str | None = getattr(user_api_key_auth, "user_id", None) if user_api_key_auth else None
        if not submitter_user_id:
            return []

        try:
            from litellm.proxy._experimental.mcp_server.db import (  # noqa: PLC0415
                get_active_submitted_mcp_server_ids_for_user,
            )
            from litellm.proxy.proxy_server import prisma_client, user_api_key_cache
        except Exception as e:  # noqa: BLE001
            verbose_logger.warning("Failed to load BYOM submitted MCP server cache dependencies: %s", e)
            return []

        byom_cache_key: Final = self.get_byom_submitted_servers_cache_key(submitter_user_id)
        submitted_server_ids: list[str] | None = None
        try:
            cached_submitted_server_ids: Final = await user_api_key_cache.async_get_cache(key=byom_cache_key)
            if cached_submitted_server_ids is not None:
                submitted_server_ids = cast(list[str], cached_submitted_server_ids)
        except Exception as e:  # noqa: BLE001
            verbose_logger.warning("Failed to read BYOM submitted MCP server cache: %s", e)

        if submitted_server_ids is None:
            if prisma_client is None:
                submitted_server_ids = []
            else:
                try:
                    submitted_server_ids = await get_active_submitted_mcp_server_ids_for_user(
                        prisma_client, submitter_user_id
                    )
                except Exception as e:  # noqa: BLE001
                    verbose_logger.warning("Failed to read BYOM submitted MCP servers from database: %s", e)
                    submitted_server_ids = []
            try:
                await user_api_key_cache.async_set_cache(
                    key=byom_cache_key,
                    value=submitted_server_ids,
                    ttl=60,
                )
            except Exception as e:  # noqa: BLE001
                verbose_logger.warning("Failed to write BYOM submitted MCP server cache: %s", e)

        return [server_id for server_id in submitted_server_ids if self.get_mcp_server_by_id(server_id) is not None]

    async def operator_open_server_ids(
        self,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        *,
        allow_all_server_ids: list[str] | None = None,
        submitted_server_ids: list[str] | None = None,
    ) -> set:
        """Servers reachable through OPEN channels rather than a grant: operator-opened
        ``allow_all_keys`` servers, plus the caller's own active BYOM submissions when the caller
        carries no explicit ``mcp_servers`` scope.

        The single owner of that question for BOTH axes. The server union in
        ``get_allowed_mcp_servers`` adds these ids, and the admitted subject's tool resolution asks
        the same question to treat an open-channel server as default-open for tools — exactly how a
        virtual key experiences it. Encoding the channel membership twice is how a server ends up
        listable but uninvokable.

        Empty inside a toolset scope: toolset_mcp_route / dynamic_mcp_route set
        ``_mcp_active_toolset_id`` before calling the handler, pinning the request to the toolset's
        own servers (checking op.mcp_toolsets==[] instead would false-positive on DB-default rows
        where Postgres initialises the column to ARRAY[]::TEXT[]).

        ``allow_all_server_ids`` / ``submitted_server_ids`` are injectable so the server union,
        which precomputes both for its fallback path, does not compute them twice."""
        from litellm.proxy._experimental.mcp_server.mcp_context import (  # noqa: PLC0415
            _mcp_active_toolset_id,
        )

        if _mcp_active_toolset_id.get() is not None:
            return set()
        if allow_all_server_ids is None:
            allow_all_server_ids = self.get_allow_all_keys_server_ids()
        open_ids: Final = set(allow_all_server_ids)
        key_object_permission: Final = user_api_key_auth.object_permission if user_api_key_auth else None
        # "Explicitly scoped, so do not widen with BYOM" is a rule about a CREDENTIAL that carries
        # its own mcp_servers list. It does not describe a keyless admitted subject: its
        # object_permission is the user's own row, whose mcp_servers column is [] by DB default, so
        # applying this rule would hide almost every admitted user's OWN submitted servers. Their
        # submissions are theirs by authorship, and their scope comes from the per-source union.
        has_explicit_object_permission: Final = (
            not _is_mcp_admitted_user_subject(user_api_key_auth)
            and key_object_permission is not None
            and (key_object_permission.mcp_servers is not None)
        )
        if not has_explicit_object_permission:
            if submitted_server_ids is None:
                submitted_server_ids = await self._get_active_submitted_mcp_server_ids_for_user(user_api_key_auth)
            open_ids.update(submitted_server_ids)
        return open_ids

    @staticmethod
    def _admitted_session_resource_scope(user_api_key_auth: UserAPIKeyAuth | None) -> str | None:
        """The single server an admitted session subject's bearer was scoped to at authorize
        time (RFC 8707 resource), or None for every other principal shape and for unscoped
        sessions. Read at every return path of :meth:`get_allowed_mcp_servers`, including
        the exception fallback, and applied AFTER every union (grants, operator-open,
        submitted) because the scope is a ceiling over the whole reachable set; a resolver
        fault therefore never widens a scoped bearer to the allow-all set."""
        if user_api_key_auth is None or not _is_mcp_admitted_user_subject(user_api_key_auth):
            return None
        return user_api_key_auth.mcp_session_resource_server_id

    async def get_allowed_mcp_servers(self, user_api_key_auth: UserAPIKeyAuth | None = None) -> list[str]:
        """
        Get the allowed MCP Servers for the user.

        Priority:
        1. If object_permission.mcp_servers is explicitly set, use it (even for admins)
        2. If admin and no object_permission, return all servers
        3. Otherwise, use standard permission checks
        """
        allow_all_server_ids: Final = self.get_allow_all_keys_server_ids()

        # A keyless admitted subject is resolved per grant source, and channel decisions that are
        # absolute for a scoped KEY credential are not absolute for it: its own opt-out silences its
        # own source (handled per source in the resolver), never its teams' grants. Its admin role
        # rides the HUMAN, not the credential: an admin's session resolves the same registry their
        # dashboard shows (connect-page parity), bounded like an admin key by explicit
        # object_permission scope, the entitlement ceiling, and the session resource scope below.
        is_admitted_subject: Final = _is_mcp_admitted_user_subject(user_api_key_auth)

        # The key explicitly opted out of every MCP server. Return zero before
        # layering on allow_all_keys or submitted servers so the opt-out is absolute.
        key_object_permission: Final = user_api_key_auth.object_permission if user_api_key_auth else None
        if (
            not is_admitted_subject
            and key_object_permission is not None
            and (SpecialMCPServerNames.no_mcp_servers.value in (key_object_permission.mcp_servers or []))
        ):
            return []

        # Check if object_permission.mcp_servers is explicitly set (not None, empty list is valid)
        has_explicit_object_permission: Final = key_object_permission is not None and (
            key_object_permission.mcp_servers is not None
        )
        if has_explicit_object_permission:
            verbose_logger.debug("Object permission mcp_servers explicitly set: %s", key_object_permission.mcp_servers)

        # BYOM creator visibility never widens a key that was explicitly scoped:
        # only keys without their own mcp_servers list get submitted servers unioned in.
        submitted_server_ids: Final = (
            []
            if has_explicit_object_permission
            else await self._get_active_submitted_mcp_server_ids_for_user(user_api_key_auth)
        )

        try:
            # Admin view with no explicit object permission and no entitlement ceiling resolves the
            # whole registry, for keys AND admitted session subjects alike (one predicate owns the
            # question). Seeded into the union rather than returned early so the session resource
            # scope below still bounds a per-server envelope held by an admin.
            combined_servers: Final = (
                set(self.get_registry().keys())
                if await MCPRequestHandler.admin_view_unscoped(user_api_key_auth)
                else set(await MCPRequestHandler.get_allowed_mcp_servers(user_api_key_auth))
            )
            verbose_logger.debug("Allowed MCP Servers for user api key auth: %s", combined_servers)
            combined_servers.update(
                await self.operator_open_server_ids(
                    user_api_key_auth,
                    allow_all_server_ids=allow_all_server_ids,
                    submitted_server_ids=submitted_server_ids,
                )
            )

            # For anonymous callers (no user_id, no role), also surface any
            # servers the operator has opted into upstream-delegated auth.
            # These servers handle their own auth at the upstream level, so
            # LiteLLM granting access here does not bypass any security gate.
            is_anonymous: Final = not (
                user_api_key_auth
                and (
                    getattr(user_api_key_auth, "user_id", None)
                    or getattr(user_api_key_auth, "user_role", None)
                    or getattr(user_api_key_auth, "api_key", None)
                )
            )
            if is_anonymous:
                delegate_server_ids: Final = [
                    server.server_id
                    for server in self.get_registry().values()
                    if (
                        getattr(server, "auth_type", None) == MCPAuth.oauth2
                        and getattr(server, "delegate_auth_to_upstream", False) is True
                        # M2M servers must not be exposed anonymously: an
                        # unauthenticated caller would get LiteLLM to proxy tool
                        # calls using its stored client_credentials. Resolve the flow
                        # rather than reading has_client_credentials so an unstamped
                        # M2M-shape row (null column, verbatim-read as non-M2M) still
                        # fails closed here, matching the anonymous-delegate auth gate.
                        and MCPServerManager.effective_oauth2_flow(server) != "client_credentials"
                    )
                    or getattr(server, "auth_type", None) == MCPAuth.true_passthrough
                ]
                combined_servers.update(delegate_server_ids)

            if len(combined_servers) == 0:
                verbose_logger.debug("No allowed MCP Servers found for user api key auth.")
            scope = MCPServerManager._admitted_session_resource_scope(user_api_key_auth)
            return [server_id for server_id in combined_servers if scope is None or server_id == scope]
        except Exception:  # noqa: BLE001
            verbose_logger.exception(
                "Failed to get allowed MCP servers; team-level object_permission "
                "grants may be dropped. Falling back to global and submitted servers."
            )
            scope = MCPServerManager._admitted_session_resource_scope(user_api_key_auth)
            return [
                server_id
                for server_id in dict.fromkeys(allow_all_server_ids + submitted_server_ids)
                if scope is None or server_id == scope
            ]

    async def resolve_toolset_tool_permissions(
        self,
        toolset_ids: list[str],
    ) -> dict[str, list[str]]:
        """
        Resolve a list of toolset IDs into a mcp_tool_permissions dict.

        Returns: {server_id: [tool_name, ...]} — the union of all tools across
        the given toolsets.  Results are cached via ``user_api_key_cache`` (a
        Redis-backed ``DualCache`` in production) so that cache entries are
        shared across workers and cold-cache DB hits are minimised.

        A row names a tool on the server identified by ``server_id``, so the
        stored name is the tool's own name and is used as written.  It is never
        reduced by the server's wire prefix: that prefix is added on the way out
        and is not part of any tool's identity, so treating a leading segment as
        one silently renames the tool when a native name happens to begin with
        it (``greyhound_internal_events`` on a server prefixed ``greyhound``).
        """
        from litellm.proxy._experimental.mcp_server.toolset_db import list_mcp_toolsets
        from litellm.proxy.proxy_server import prisma_client, user_api_key_cache

        if not toolset_ids or prisma_client is None:
            return {}

        cache_key: Final = "toolset_perms:" + ",".join(sorted(toolset_ids))
        cached: Final[dict[str, list[str]] | None] = await user_api_key_cache.async_get_cache(key=cache_key)
        if cached is not None:
            return cached

        try:
            toolsets: Final = await list_mcp_toolsets(prisma_client, toolset_ids=toolset_ids)
            tool_permissions: Final[dict[str, list[str]]] = {}
            for toolset in toolsets:
                for tool in toolset.tools:
                    allowed_names = tool_permissions.setdefault(tool["server_id"], [])
                    if tool["tool_name"] not in allowed_names:
                        allowed_names.append(tool["tool_name"])
            await user_api_key_cache.async_set_cache(
                key=cache_key,
                value=tool_permissions,
                ttl=get_management_object_ttl(user_api_key_cache),
            )
            return tool_permissions
        except Exception as e:
            verbose_logger.warning("Failed to resolve toolset permissions: %s", e)
            return {}

    def invalidate_toolset_cache(self, toolset_id: str | None = None) -> None:
        """Evict cached toolset permission entries.

        Called after create/update/delete of a toolset so stale data is not served.
        The in-memory layer of ``user_api_key_cache`` is cleared immediately;
        Redis entries expire naturally after the configured TTL.
        Pass toolset_id to evict only entries containing that ID, or None to clear all.
        """
        # Clear the in-memory layer of the shared DualCache for affected keys.
        # We can't enumerate Redis keys by pattern, so Redis entries expire via TTL.
        try:
            from litellm.proxy.proxy_server import user_api_key_cache

            in_mem: Final[InMemoryCache | None] = getattr(user_api_key_cache, "in_memory_cache", None)
            if in_mem is None:
                return
            cache_dict: Final[_InMemoryCacheDict] = getattr(in_mem, "cache_dict", {})
            if toolset_id is None:
                keys_to_remove = [k for k in cache_dict if k.startswith("toolset_")]
            else:
                # Evict permission-cache entries that reference this toolset ID.
                # Also evict ALL name-cache entries (toolset_name:*): we can't map
                # toolset_id → toolset_name without a DB call, and the name may have
                # changed in an update anyway.
                keys_to_remove = [
                    k
                    for k in cache_dict
                    if (k.startswith("toolset_perms:") and toolset_id in k) or k.startswith("toolset_name:")
                ]
            for k in keys_to_remove:
                cache_dict.pop(k, None)
        except Exception as e:
            verbose_logger.warning("invalidate_toolset_cache: failed to evict in-memory entries: %s", e)

    async def get_toolset_by_name_cached(
        self,
        prisma_client: PrismaClient,
        toolset_name: str,
    ) -> "MCPToolset | None":
        """Return a toolset by name, cached in ``user_api_key_cache`` (Redis-backed
        ``DualCache`` in production) to avoid a DB hit on every routed request.

        Serialisation note: the cache value is stored as a plain JSON-safe dict via
        ``model_dump(mode="json")`` so that Redis round-trips correctly in multi-worker
        deployments.  On a cache hit we reconstruct the ``MCPToolset`` Pydantic object
        so callers can always use attribute access (e.g. ``toolset.toolset_id``).
        """
        from litellm.proxy.proxy_server import user_api_key_cache
        from litellm.types.mcp_server.mcp_toolset import MCPToolset

        cache_key: Final = f"toolset_name:{toolset_name}"
        cached: Final = await user_api_key_cache.async_get_cache(key=cache_key)
        if cached is not None:
            # Sentinel value used to cache "not found" so we don't re-query for
            # names that don't exist.
            if cached == "__not_found__":
                return None
            # Redis deserialises JSON back as a plain dict — reconstruct the model.
            if isinstance(cached, dict):
                return MCPToolset(**cached)
            return cached

        from litellm.proxy._experimental.mcp_server.toolset_db import (
            get_mcp_toolset_by_name,
        )

        toolset: Final = await get_mcp_toolset_by_name(prisma_client, toolset_name)
        await user_api_key_cache.async_set_cache(
            key=cache_key,
            value=(toolset.model_dump(mode="json") if toolset is not None else "__not_found__"),
            ttl=get_management_object_ttl(user_api_key_cache),
        )
        return toolset

    def filter_server_ids_by_ip(self, server_ids: list[str], client_ip: str | None) -> list[str]:
        """
        Filter server IDs by client IP — external callers only see public servers.

        Returns server_ids unchanged when client_ip is None (no filtering).
        """
        filtered, _ = self.filter_server_ids_by_ip_with_info(server_ids, client_ip)
        return filtered

    def filter_server_ids_by_ip_with_info(self, server_ids: list[str], client_ip: str | None) -> tuple[list[str], int]:
        """
        Filter server IDs by client IP — external callers only see public servers.

        Returns (filtered_ids, ip_blocked_count) where ip_blocked_count is the number
        of servers that were blocked because the client IP is not allowed to access them.
        Returns server_ids unchanged (with 0 blocked) when client_ip is None.
        """
        if client_ip is None:
            return server_ids, 0
        allowed: Final = []
        blocked = 0
        for sid in server_ids:
            s = self.get_mcp_server_by_id(sid)
            if s is not None and self._is_server_accessible_from_ip(s, client_ip):
                allowed.append(sid)
            elif s is not None:
                blocked += 1
        return allowed, blocked

    async def get_tools_for_server(self, server_id: str) -> list[MCPTool]:
        """
        Get the tools for a given server
        """
        try:
            server: Final = self.get_mcp_server_by_id(server_id)
            if server is None:
                verbose_logger.warning("MCP Server %s not found", server_id)
                return []
            return await self._get_tools_from_server(server)
        except Exception as e:
            verbose_logger.warning("Failed to get tools from server %s: %s", server_id, e)
            return []

    async def list_tools(
        self,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        mcp_auth_header: str | None = None,
        mcp_server_auth_headers: dict[str, str | dict[str, str]] | None = None,
    ) -> list[MCPTool]:
        """
        List all tools available across all MCP Servers.

        Args:
            user_api_key_auth: User authentication
            mcp_auth_header: MCP auth header (deprecated)
            mcp_server_auth_headers: Optional dict of server-specific auth headers {server_alias: auth_value}
            mcp_protocol_version: Optional MCP protocol version from request header

        Returns:
            List[MCPTool]: Combined list of tools from all servers
        """
        allowed_mcp_servers: Final = await self.get_allowed_mcp_servers(user_api_key_auth)

        verbose_logger.debug("SERVER MANAGER LISTING TOOLS")

        async def _fetch_server_tools(server_id: str) -> list[MCPTool]:
            """Fetch tools from a single server with error handling."""
            server: Final = self.get_mcp_server_by_id(server_id)
            if server is None:
                verbose_logger.warning("MCP Server %s not found", server_id)
                return []

            # Get server-specific auth header if available
            server_auth_header: str | dict[str, str] | None = None
            if mcp_server_auth_headers:
                server_auth_header = lookup_mcp_server_auth_in_headers(
                    mcp_server_auth_headers,
                    alias=server.alias,
                    server_name=server.server_name,
                )

            # Fall back to deprecated mcp_auth_header if no server-specific header found
            if server_auth_header is None:
                server_auth_header = mcp_auth_header

            try:
                tools: Final = await self._get_tools_from_server(
                    server=server,
                    mcp_auth_header=server_auth_header,
                    user_api_key_auth=user_api_key_auth,
                )
                return tools
            except Exception as e:
                verbose_logger.warning(
                    "Failed to list tools from server %s: %s. Continuing with other servers.", server.name, e
                )
                return []

        # Fetch tools from all servers in parallel
        tasks: Final = [_fetch_server_tools(server_id) for server_id in allowed_mcp_servers]
        results: Final = await asyncio.gather(*tasks)

        # Flatten results into single list
        list_tools_result: Final[list[MCPTool]] = [tool for tools in results for tool in tools]

        verbose_logger.info("Successfully fetched %s tools total from all servers", len(list_tools_result))
        return list_tools_result

    #########################################################
    # Methods that call the upstream MCP servers
    #########################################################
    @staticmethod
    def _extract_bearer_token(
        oauth2_headers: dict[str, str] | None,
        raw_headers: dict[str, str] | None,
    ) -> str | None:
        """Extract the bare Bearer token from oauth2_headers or raw_headers.

        Returns the token string without the ``Bearer `` prefix, or ``None``
        if no Authorization header is found.
        """
        auth_value: str | None = None
        if oauth2_headers and "Authorization" in oauth2_headers:
            auth_value = oauth2_headers["Authorization"]
        elif raw_headers:
            # raw_headers may have lowercase keys depending on the ASGI server
            normalized: Final = {k.lower(): v for k, v in raw_headers.items()}
            auth_value = normalized.get("authorization")
        if auth_value:
            if auth_value.startswith("Bearer "):
                return auth_value[len("Bearer ") :]
            return auth_value
        return None

    def _obo_subject_token(
        self,
        server: MCPServer,
        raw_headers: dict[str, str] | None,
    ) -> str | None:
        """The caller's bearer as the token_exchange (OBO) subject token, for that mode only.

        Prompts/resources discovery and reads on a token_exchange server must exchange the caller's
        token like the tools paths do, not connect with no credential. Other modes never read the
        inbound bearer, so return None to avoid forwarding it.
        """
        if server.auth_type != MCPAuth.oauth2_token_exchange:
            return None
        return self._extract_bearer_token(None, raw_headers)

    def _build_stdio_env(
        self,
        server: MCPServer,
        raw_headers: dict[str, str] | None = None,
    ) -> dict[str, str] | None:
        """Resolve stdio env values, supporting header-driven placeholders."""

        if server.transport != MCPTransport.stdio or not server.env:
            return None

        resolved_env: Final[dict[str, str]] = {}
        normalized_headers: Final = {k.lower(): v for k, v in (raw_headers or {}).items()}

        for env_key, env_value in server.env.items():
            stripped_value = env_value.strip()
            match = self._STDIO_ENV_TEMPLATE_PATTERN.match(stripped_value)
            if match:
                header_name = match.group(1)
                header_value = normalized_headers.get(header_name.lower())
                if header_value is None:
                    continue
                resolved_env[env_key] = header_value
            else:
                resolved_env[env_key] = env_value

        return resolved_env

    def _references_per_user_env_var(self, server: MCPServer) -> bool:
        """True when ``server.static_headers`` reference a per-user ``${NAME}`` env var.

        Such placeholders can only be filled from a calling user's stored values,
        so a userless probe (health check / instructions prefetch) would forward
        the literal ``${NAME}`` upstream and get rejected. Callers skip the probe
        and report ``unknown`` instead of a misleading ``unhealthy``.
        """
        static_headers: Final = server.static_headers
        env_vars: Final[_EnvVarList | None] = getattr(server, "env_vars", None)
        if not static_headers or not env_vars:
            return False
        _global_values, user_specs = parse_admin_env_vars(env_vars)
        user_var_names: Final = {spec["name"] for spec in user_specs}
        if not user_var_names:
            return False
        referenced: Final = collect_env_var_references(strings=static_headers.values())
        return bool(referenced & user_var_names)

    async def _resolve_static_headers_with_env_vars(
        self,
        server: MCPServer,
        user_api_key_auth: UserAPIKeyAuth | None,
        *,
        raise_on_missing: bool = True,
    ) -> dict[str, str] | None:
        """Return server.static_headers with ``${NAME}`` interpolated.

        Globals come from ``server.env_vars`` entries with ``scope=="global"``.
        Per-user values come from the ``LiteLLM_MCPUserEnvVars`` row for the
        calling user.

        When ``raise_on_missing`` is ``True`` (the tool-*call* path), raises
        ``MCPMissingUserEnvVarsError`` if ``static_headers`` reference a per-user
        variable the calling user has not yet supplied — converted into a
        user-facing 412 by the REST layer.

        When ``raise_on_missing`` is ``False`` (the tool-*list* path), missing
        per-user vars are non-blocking: we interpolate whatever is available and
        leave unfilled ``${NAME}`` references untouched, so the server's tools
        still appear in the listing. The user only hits the friendly error when
        they actually invoke a tool that needs the missing value.
        """
        static_headers: Final = server.static_headers
        env_vars: Final = getattr(server, "env_vars", None)
        if not static_headers and not env_vars:
            return static_headers

        global_values, user_specs = parse_admin_env_vars(env_vars)
        # An empty-valued global is treated as unset: it must not mask a per-user
        # var the user still has to supply, nor override a value the user did
        # supply. The unresolved ${NAME} is then left untouched, like any other
        # undefined reference.
        global_values = {name: value for name, value in global_values.items() if value}
        user_var_names: Final = {spec["name"] for spec in user_specs}

        # If no env vars are configured, return static_headers as-is.
        if not global_values and not user_specs:
            return static_headers

        # Figure out which user-scoped vars are actually referenced. A var that
        # also carries a global value is always covered by that global (globals
        # win in the merge below), so it can never be genuinely "missing" even if
        # the user hasn't filled it in -- only vars without a global fallback do.
        referenced: Final = collect_env_var_references(strings=(static_headers or {}).values())
        referenced_user_vars: Final = referenced & user_var_names
        required_user_vars: Final = {name for name in referenced_user_vars if name not in global_values}

        user_values: dict[str, str] = {}
        if required_user_vars:
            try:
                user_values = await self._load_user_env_vars(server, user_api_key_auth)
            except Exception as exc:
                # On the tool-call path a DB failure must surface as a real
                # server error, not a misleading "set up your credentials" 412.
                # On the listing path we stay best-effort and leave the
                # unfilled ${NAME} references untouched so tools still appear.
                if raise_on_missing:
                    raise
                verbose_logger.warning(
                    "MCPServerManager: best-effort user env var load failed for server=%s: %s",
                    server.server_id,
                    exc,
                )

            if raise_on_missing:
                missing = sorted(name for name in required_user_vars if not user_values.get(name))
                if missing:
                    # A cached negative must never produce a 412: cache
                    # invalidation is process-local, so a user who just stored
                    # values on another worker would otherwise be told their
                    # credentials are missing until the entry expires. Confirm
                    # against the DB before raising.
                    user_values = await self._load_user_env_vars(server, user_api_key_auth, force_refresh=True)
                    missing = sorted(name for name in required_user_vars if not user_values.get(name))
                if missing:
                    raise MCPMissingUserEnvVarsError(
                        server_id=server.server_id,
                        server_name=server.server_name or server.name,
                        missing=missing,
                        setup_url=build_env_var_setup_url(server.server_id),
                    )

        # Only honor stored user values for currently user-scoped vars, and let
        # admin globals win, so a stale row from when a var was user-scoped can
        # never override the global value the admin set after switching it.
        scoped_user_values: Final = {name: value for name, value in user_values.items() if name in user_var_names}
        merged_vars: Final[dict[str, str]] = {**scoped_user_values, **global_values}
        if not static_headers:
            return static_headers
        return interpolate_headers(static_headers, merged_vars)

    async def _load_user_env_vars(
        self,
        server: MCPServer,
        user_api_key_auth: UserAPIKeyAuth | None,
        *,
        force_refresh: bool = False,
    ) -> dict[str, str]:
        """Look up the calling user's env var values for ``server``.

        Returns an empty dict when no user is available. Results are cached in a
        short-lived in-memory map keyed by (user_id, server_id) so the tool-call
        and tool-listing paths avoid a DB round-trip per request within the TTL
        window; the cache is invalidated when the user stores or clears values.
        Pass ``force_refresh`` to bypass the cache read and re-fetch from the DB
        (used before raising a "missing credentials" error so a process-local
        stale entry cannot mask values stored on another worker). A missing DB
        connection and any other DB error propagate so the caller can decide
        between failing the request (tool-call path) and staying best-effort
        (listing path); they must never be mistaken for "user has no values",
        which would send the user a misleading "set up your credentials" 412.
        """
        if user_api_key_auth is None:
            return {}
        user_id: Final[str | None] = getattr(user_api_key_auth, "user_id", None)
        if not user_id:
            return {}

        cache_key: Final = (user_id, server.server_id)
        if not force_refresh:
            cached: Final = _user_env_vars_cache.get(cache_key)
            if cached is not None:
                values, ts = cached
                if time.monotonic() - ts < _USER_ENV_VARS_CACHE_TTL:
                    return values

        from litellm.proxy.proxy_server import prisma_client  # noqa: PLC0415

        if prisma_client is None:
            raise RuntimeError(
                "MCP per-user env vars require a database connection, but none "
                "is configured. Connect a database to your proxy to use per-user "
                "MCP env vars."
            )
        from litellm.proxy._experimental.mcp_server.db import (  # noqa: PLC0415
            get_user_env_vars,
        )

        values = await get_user_env_vars(prisma_client, user_id, server.server_id)
        _write_user_env_vars_cache(user_id, server.server_id, values)
        return values

    async def _resolve_v2_auth(
        self,
        *,
        server: MCPServer,
        spec: ServerSpec,
        provider: UpstreamCredentialProvider,
        subject_token: str | None,
        user_api_key_auth: UserAPIKeyAuth | None,
        extra_headers: dict[str, str] | None,
    ) -> tuple[httpx.Auth | None, dict[str, str] | None]:
        """Resolve a v2-owned server's upstream credential into ``(resolved_auth, extra_headers)``.

        On a missing/rejected per-user credential this raises the mode's discovery challenge
        (authorization_code's browser-OAuth 401, token_exchange's RFC 9728 challenge) or maps any
        other ``CredError`` onto its public HTTP status; it never returns an error as a value.
        """
        match await provider.resolve_credentials(to_subject(user_api_key_auth, subject_token), spec):
            case Ok(auth):
                # NoOpAuth has no header_name and so never conflicts.
                header_name: Final[str | None] = getattr(auth, "header_name", None)
                if header_name is None or not extra_headers:
                    return auth, extra_headers
                if not has_header(extra_headers, header_name):
                    return auth, extra_headers
                if isinstance(
                    spec.config,
                    (TokenExchangeConfig, AuthorizationCodeConfig, IdJagConfig, ClientCredentialsConfig),
                ):
                    # The resolver owns the credential here (token_exchange's exchanged token,
                    # authorization_code's stored token, id_jag's minted assertion,
                    # client_credentials' gateway-minted M2M token). It is authoritative: a
                    # guardrail such as MCPJWTSigner, static_headers, or any other injected
                    # Authorization must NOT shadow it (otherwise the upstream gets e.g. the
                    # signer's JWT instead of the minted token and rejects it, and for M2M the
                    # one-shot 401 refetch is lost with it). Drop only the header the resolved
                    # credential is about to occupy, so a static credential the operator aimed at a
                    # DIFFERENT header still reaches upstream.
                    return auth, without_header(extra_headers, header_name)
                # Other modes: an Authorization already supplied via extra_headers (a forwarded caller
                # header or static_headers) is intentional and wins; v1 applies those last.
                return None, extra_headers
            case Error(err):
                if err.tag == "unauthorized" and isinstance(spec.config, AuthorizationCodeConfig):
                    # authorization_code's missing per-user token -> the per-server browser-OAuth
                    # challenge, built here where the full MCPServer is in hand.
                    raise_user_oauth_challenge(server, root_path=get_server_root_path())
                if err.tag == "unauthorized" and isinstance(spec.config, TokenExchangeConfig):
                    # token_exchange (OBO): a missing/rejected subject token -> the RFC 9728 challenge
                    # pointing at the IdP the client must SSO with to obtain one, rather than an opaque
                    # 401. No gateway-side browser flow. An IdP step-up rejection (Entra Conditional
                    # Access) threads its claims blob into the challenge for the client to satisfy.
                    raise_token_exchange_challenge(
                        server,
                        root_path=get_server_root_path(),
                        claims=err.unauthorized.claims,
                    )
                raise_public(err)

    async def preflight_token_exchange(
        self,
        server: MCPServer,
        oauth2_headers: dict[str, str] | None,
        user_api_key_auth: UserAPIKeyAuth | None,
    ) -> None:
        """Run the OBO exchange for a caller-supplied subject at the transport edge.

        Single-server routes call this before the MCP session opens, where an HTTP status and
        ``WWW-Authenticate`` still reach the client. A rejected subject raises the RFC 9728
        challenge and any other ``CredError`` maps onto its public HTTP status, so an exchange
        failure surfaces as a failure instead of the session continuing into an empty tool list.
        A successful exchange is cached by the exchanger, so the session's list/call reuses it.
        """
        if server.auth_type != MCPAuth.oauth2_token_exchange:
            return
        subject_token: Final = self._extract_bearer_token(oauth2_headers, None)
        if not subject_token:
            return
        resolved_server: Final = await self.ensure_oauth_metadata_discovered(server)
        spec: Final = to_server_spec(resolved_server)
        if spec is None or not isinstance(spec.config, TokenExchangeConfig):
            return
        match await self._cred_provider.resolve_credentials(to_subject(user_api_key_auth, subject_token), spec):
            case Ok(_):
                return
            case Error(err):
                if err.tag == "unauthorized":
                    raise_token_exchange_challenge(
                        resolved_server,
                        root_path=get_server_root_path(),
                        claims=err.unauthorized.claims,
                    )
                raise_public(err)

    async def _create_mcp_client(
        self,
        server: MCPServer,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        stdio_env: dict[str, str] | None = None,
        subject_token: str | None = None,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        cred_provider: UpstreamCredentialProvider | None = None,
    ) -> MCPClient:
        """
        Create an MCPClient instance for the given server.

        Auth resolution (single place for all auth logic):
        1. ``mcp_auth_header`` — per-request/per-user override
        2. OAuth2 Token Exchange (OBO) — exchange user token for scoped token
        3. OAuth2 client_credentials token — auto-fetched and cached
        4. ``server.authentication_token`` — static token from config/DB

        Args:
            server: The server configuration.
            mcp_auth_header: Optional per-request auth override.
            extra_headers: Additional headers to forward.
            stdio_env: Environment variables for stdio transport.
            subject_token: Optional user JWT for token exchange (OBO) flow.
            user_api_key_auth: Optional auth context for sampling callbacks.

        Returns:
            Configured MCP client instance.
        """
        resolved_server: Final = await self.ensure_oauth_metadata_discovered(server)
        transport: Final = resolved_server.transport or MCPTransport.sse
        spec = None if transport == MCPTransport.stdio else _to_server_spec_fail_closed(resolved_server)
        provider: Final = cred_provider or self._cred_provider
        # A caller-supplied per-request override (mcp_auth_header / x-mcp-*) defers to the v1 path
        # so it wins - except for the modes the v2 resolver owns per-caller (authorization_code's
        # stored token, token_exchange's RFC 8693 minted token, id_jag's minted assertion, and the
        # passthrough modes' forwarded caller token). A caller must not be able to substitute another
        # user's stored credential, nor silently disable the OBO / ID-JAG exchange and forward an
        # arbitrary bearer upstream, so we keep the v2 spec and ignore the override for these; the
        # REST tools preview supplies its not-yet-persisted token through the resolver
        # (cred_provider), never this path.
        if (
            spec is not None
            and mcp_auth_header
            and not isinstance(
                spec.config,
                (AuthorizationCodeConfig, IdJagConfig, PassthroughConfig, TokenExchangeConfig),
            )
        ):
            spec = None
        auth_value: Final = await resolve_mcp_auth(resolved_server, mcp_auth_header) if spec is None else None
        auth_header_name: Final = resolved_token_header(resolved_server, mcp_auth_header) if spec is None else None

        # Create sampling and elicitation callbacks for this client
        sampling_cb = (
            _create_sampling_callback(user_api_key_auth=user_api_key_auth) if resolved_server.allow_sampling else None
        )
        elicitation_cb: Final = _create_elicitation_callback() if resolved_server.allow_elicitation else None

        # Handle stdio transport
        if transport == MCPTransport.stdio:
            resolved_env: Final = (
                stdio_env
                if stdio_env is not None
                else (dict(resolved_server.env) if resolved_server.env is not None else None)
            )

            # Ensure npm-based STDIO MCP servers have a writable cache dir.
            # In containers the default (~/.npm or /app/.npm) may not exist
            # or be read-only, causing npx to fail with ENOENT.
            if resolved_env is not None and "NPM_CONFIG_CACHE" not in resolved_env:
                resolved_env["NPM_CONFIG_CACHE"] = MCP_NPM_CACHE_DIR
            # Defense-in-depth: block commands not in the allowlist.
            # The Pydantic validator blocks new servers; this catches legacy
            # config/DB records predating the allowlist.
            if resolved_server.command:
                base_command: Final = os.path.basename(resolved_server.command)
                # Strip .exe/.cmd/.bat/.com suffix for Windows compatibility
                base_command_no_ext = base_command.lower()
                for ext in [".exe", ".cmd", ".bat", ".com"]:
                    if base_command.lower().endswith(ext):
                        base_command_no_ext = base_command[: -len(ext)].lower()
                        break
                if (
                    base_command.lower() not in MCP_STDIO_ALLOWED_COMMANDS
                    and base_command_no_ext not in MCP_STDIO_ALLOWED_COMMANDS
                ):
                    raise HTTPException(
                        status_code=403,
                        detail=f"MCP stdio command '{resolved_server.command}' is not in the allowlist ({sorted(MCP_STDIO_ALLOWED_COMMANDS)}). "
                        f"Add it to LITELLM_MCP_STDIO_EXTRA_COMMANDS to allow this command.",
                    )

            stdio_config: MCPStdioConfig | None = None
            if resolved_server.command and resolved_server.args is not None:
                stdio_config = MCPStdioConfig(
                    command=resolved_server.command,
                    args=resolved_server.args,
                    env=resolved_env,
                )

            return MCPClient(
                server_url="",  # Not used for stdio
                transport_type=transport,
                auth_type=resolved_server.auth_type,
                auth_value=auth_value,
                timeout=(resolved_server.timeout if resolved_server.timeout is not None else MCP_CLIENT_TIMEOUT),
                stdio_config=stdio_config,
                extra_headers=extra_headers,
                sampling_callback=sampling_cb,
                elicitation_callback=elicitation_cb,
            )
        else:
            # For HTTP/SSE transports
            server_url: Final = resolved_server.url or ""

            if spec is not None:
                inbound_token = subject_token
                if isinstance(spec.config, PassthroughConfig):
                    inbound_token, extra_headers = _take_forwarded_authorization(extra_headers)
                    per_server_token: Final = _passthrough_token_from_mcp_auth_header(mcp_auth_header)
                    if per_server_token is not None:
                        inbound_token = per_server_token
                resolved_auth, extra_headers = await self._resolve_v2_auth(
                    server=resolved_server,
                    spec=spec,
                    provider=provider,
                    subject_token=inbound_token,
                    user_api_key_auth=user_api_key_auth,
                    extra_headers=extra_headers,
                )
                return MCPClient(
                    server_url=server_url,
                    transport_type=transport,
                    auth_type=resolved_server.auth_type,
                    timeout=(resolved_server.timeout if resolved_server.timeout is not None else MCP_CLIENT_TIMEOUT),
                    extra_headers=extra_headers,
                    resolved_auth=resolved_auth,
                    sampling_callback=sampling_cb,
                    elicitation_callback=elicitation_cb,
                )

            # Create SigV4 auth if configured
            aws_auth = None
            if resolved_server.auth_type == MCPAuth.aws_sigv4:
                aws_auth = MCPSigV4Auth(
                    aws_access_key_id=resolved_server.aws_access_key_id,
                    aws_secret_access_key=resolved_server.aws_secret_access_key,
                    aws_session_token=resolved_server.aws_session_token,
                    aws_region_name=resolved_server.aws_region_name,
                    aws_service_name=resolved_server.aws_service_name,
                    aws_role_name=resolved_server.aws_role_name,
                    aws_session_name=resolved_server.aws_session_name,
                )

            return MCPClient(
                server_url=server_url,
                transport_type=transport,
                auth_type=resolved_server.auth_type,
                auth_value=auth_value,
                auth_header_name=auth_header_name,
                timeout=(resolved_server.timeout if resolved_server.timeout is not None else MCP_CLIENT_TIMEOUT),
                extra_headers=extra_headers,
                aws_auth=aws_auth,
                sampling_callback=sampling_cb,
                elicitation_callback=elicitation_cb,
            )

    async def _get_tools_from_server(
        self,
        server: MCPServer,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        add_prefix: bool = True,
        raw_headers: dict[str, str] | None = None,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        oauth2_headers: dict[str, str] | None = None,
    ) -> list[MCPTool]:
        """
        Helper method to get tools from a single MCP server with prefixed names.

        Args:
            server (MCPServer): The server to query tools from
            mcp_auth_header: Optional auth header for MCP server

        Returns:
            List[MCPTool]: List of tools available on the server with prefixed names
        """
        from litellm.proxy._experimental.mcp_server.tool_registry import (
            global_mcp_tool_registry,
        )

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("_get_tools_from_server for %s...", server.name)

        client = None

        try:
            # Tool *listing* must not be blocked by missing per-user env vars —
            # the server's tools should still appear so the client connects. The
            # friendly "missing vars" error is raised only on the tool-*call*
            # path (see _call_regular_mcp_tool).
            resolved_static_headers: Final = await self._resolve_static_headers_with_env_vars(
                server, user_api_key_auth, raise_on_missing=False
            )
            if resolved_static_headers:
                if extra_headers is None:
                    extra_headers = {}
                extra_headers.update(resolved_static_headers)

            # MCPJWTSigner: inject signed JWT for tools/list (list path skips pre_call_hook).
            # Skip entirely when the signer is not configured (avoid an unnecessary
            # dict copy on every list call), when the server has its own static
            # Authorization header, when a per-user mcp_auth_header has already
            # been resolved, or when the caller already supplied an Authorization
            # entry in extra_headers (e.g. a per-user OAuth token resolved
            # upstream) — admin-configured static auth and per-user OAuth must
            # take precedence so the signer doesn't silently overwrite e.g. an
            # upstream API key or a user's OAuth token (MCPClient._get_auth_headers
            # applies extra_headers after writing Authorization from auth_value, so
            # an injected JWT would otherwise clobber the per-user token).
            if user_api_key_auth is not None and not server.spec_path:
                from litellm.proxy.guardrails.guardrail_hooks.mcp_jwt_signer.mcp_jwt_signer import (
                    get_mcp_jwt_signer,
                    inject_mcp_jwt_headers_for_upstream,
                )

                static_headers: Final = server.static_headers or {}
                has_static_authorization: Final = any(
                    isinstance(k, str) and k.lower() == "authorization" for k in static_headers
                )
                has_extra_authorization: Final = bool(extra_headers) and any(
                    isinstance(k, str) and k.lower() == "authorization" for k in (extra_headers or {})
                )

                if (
                    get_mcp_jwt_signer() is not None
                    and not has_static_authorization
                    and not mcp_auth_header
                    and not has_extra_authorization
                ):
                    extra_headers = await inject_mcp_jwt_headers_for_upstream(
                        user_api_key_dict=user_api_key_auth,
                        extra_headers=extra_headers,
                        raw_headers=raw_headers,
                        for_list_tools=True,
                    )

            stdio_env: Final = self._build_stdio_env(server, raw_headers)

            # token_exchange (OBO) discovery needs the caller's token too: list it with the user's own
            # token (mirrors the call path), not v1's deleted client_credentials fallback. Other modes
            # never read the inbound bearer, so leave subject_token None to avoid forwarding it.
            subject_token: Final = (
                self._extract_bearer_token(oauth2_headers, raw_headers)
                if server.auth_type == MCPAuth.oauth2_token_exchange
                else None
            )

            client = await self._create_mcp_client(
                server=server,
                mcp_auth_header=mcp_auth_header,
                extra_headers=extra_headers,
                stdio_env=stdio_env,
                subject_token=subject_token,
                user_api_key_auth=user_api_key_auth,
            )

            ## HANDLE OPENAPI TOOLS
            if server.spec_path:
                # OpenAPI tools were stored in the registry under the prefix
                # active at registration time — fetch by that same prefix.
                _tools: Final = global_mcp_tool_registry.list_tools(tool_prefix=get_server_prefix(server))
                tools = global_mcp_tool_registry.convert_tools_to_mcp_sdk_tool_type(_tools)
                # OpenAPI tools are stored in the registry with their prefix already
                # applied (e.g. "test_petstore-getinventory").  Do NOT pass them
                # through _create_prefixed_tools — that would add the prefix a second
                # time producing "test_petstore-test_petstore-getinventory".
                if not add_prefix:
                    prefix: Final = get_server_prefix(server)
                    sep: Final = MCP_TOOL_PREFIX_SEPARATOR
                    tools = [
                        (
                            t.model_copy(update={"name": t.name[len(prefix) + len(sep) :]})
                            if t.name.startswith(f"{prefix}{sep}")
                            else t
                        )
                        for t in tools
                    ]
                return tools
            else:
                tools = await self._fetch_tools_with_timeout(client, server.name)
                self._remember_upstream_initialize_instructions(server, client)

            prefixed_or_original_tools: Final = self._create_prefixed_tools(tools, server, add_prefix=add_prefix)

            return prefixed_or_original_tools

        except MCPUpstreamAuthError as upstream_auth_error:
            # Pass-through 401 must surface to single-server routes so the
            # client triggers the upstream OAuth flow. The multi-server
            # aggregator catches this explicitly to keep absorbing.
            if server.is_dcr_bridge and upstream_auth_error.www_authenticate is not None:
                raise MCPUpstreamAuthError(
                    status_code=upstream_auth_error.status_code,
                    www_authenticate=None,
                    server_name=upstream_auth_error.server_name,
                ) from upstream_auth_error
            raise
        except HTTPException as e:
            # A v2 resolver auth challenge (token_exchange's RFC 9728 401, authorization_code's
            # browser-OAuth 401, or a 403) is raised at client-build time, inside this try. Route it
            # through the same MCPUpstreamAuthError channel as pass-through so single-server routes
            # surface the challenge (the client re-authenticates) while the aggregator keeps absorbing.
            # Non-auth HTTP errors stay absorbed so one misconfigured server can't blank the listing.
            if e.status_code in (401, 403):
                headers: Final = e.headers or {}
                challenge_header: Final = headers.get("WWW-Authenticate") or headers.get("www-authenticate")
                raise MCPUpstreamAuthError(
                    status_code=e.status_code,
                    www_authenticate=None if server.is_dcr_bridge else challenge_header,
                    server_name=server.name,
                ) from e
            verbose_logger.warning("Failed to get tools from server %s: %s", server.name, e)
            raise MCPServerListError(ServerListFault(tag="internal", status_code=e.status_code), server.name) from e
        except MCPServerListError:
            raise
        except Exception as e:
            verbose_logger.warning("Failed to get tools from server %s: %s", server.name, e)
            raise_classified_list_failure(e, server.name, suppress_challenge=server.is_dcr_bridge)

    async def get_prompts_from_server(
        self,
        server: MCPServer,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        add_prefix: bool = True,
        raw_headers: dict[str, str] | None = None,
    ) -> list[Prompt]:
        """
        Helper method to get prompts from a single MCP server with prefixed names.

        Args:
            server (MCPServer): The server to query prompts from
            mcp_auth_header: Optional auth header for MCP server

        Returns:
            List[Prompt]: List of prompts available on the server with prefixed names
        """

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("get_prompts_from_server for %s...", server.name)

        client = None

        try:
            if server.static_headers:
                if extra_headers is None:
                    extra_headers = {}
                extra_headers.update(server.static_headers)

            stdio_env: Final = self._build_stdio_env(server, raw_headers)
            subject_token: Final = self._obo_subject_token(server, raw_headers)

            client = await self._create_mcp_client(
                server=server,
                mcp_auth_header=mcp_auth_header,
                extra_headers=extra_headers,
                stdio_env=stdio_env,
                subject_token=subject_token,
            )

            prompts: Final = await client.list_prompts()

            prefixed_or_original_prompts: Final = self._create_prefixed_prompts(prompts, server, add_prefix=add_prefix)

            return prefixed_or_original_prompts

        except Exception as e:
            verbose_logger.warning("Failed to get prompts from server %s: %s", server.name, e)
            return []

    async def get_resources_from_server(
        self,
        server: MCPServer,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        add_prefix: bool = True,
        raw_headers: dict[str, str] | None = None,
    ) -> list[Resource]:
        """Fetch available resources from a single MCP server."""

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("get_resources_from_server for %s...", server.name)

        client = None

        try:
            if server.static_headers:
                if extra_headers is None:
                    extra_headers = {}
                extra_headers.update(server.static_headers)

            stdio_env: Final = self._build_stdio_env(server, raw_headers)
            subject_token: Final = self._obo_subject_token(server, raw_headers)

            client = await self._create_mcp_client(
                server=server,
                mcp_auth_header=mcp_auth_header,
                extra_headers=extra_headers,
                stdio_env=stdio_env,
                subject_token=subject_token,
            )

            resources: Final = await client.list_resources()

            prefixed_resources: Final = self._create_prefixed_resources(resources, server, add_prefix=add_prefix)

            return prefixed_resources

        except Exception as e:
            verbose_logger.warning("Failed to get resources from server %s: %s", server.name, e)
            return []

    async def get_resource_templates_from_server(
        self,
        server: MCPServer,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        add_prefix: bool = True,
        raw_headers: dict[str, str] | None = None,
    ) -> list[ResourceTemplate]:
        """Fetch available resource templates from a single MCP server."""

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("get_resource_templates_from_server for %s...", server.name)

        client = None

        try:
            if server.static_headers:
                if extra_headers is None:
                    extra_headers = {}
                extra_headers.update(server.static_headers)

            stdio_env: Final = self._build_stdio_env(server, raw_headers)
            subject_token: Final = self._obo_subject_token(server, raw_headers)

            client = await self._create_mcp_client(
                server=server,
                mcp_auth_header=mcp_auth_header,
                extra_headers=extra_headers,
                stdio_env=stdio_env,
                subject_token=subject_token,
            )

            resource_templates: Final = await client.list_resource_templates()

            prefixed_templates: Final = self._create_prefixed_resource_templates(
                resource_templates, server, add_prefix=add_prefix
            )

            return prefixed_templates

        except Exception as e:
            verbose_logger.warning("Failed to get resource templates from server %s: %s", server.name, e)
            return []

    async def read_resource_from_server(
        self,
        server: MCPServer,
        url: AnyUrl,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        raw_headers: dict[str, str] | None = None,
    ) -> ReadResourceResult:
        """Read resource contents from a specific MCP server."""

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("read_resource_from_server for %s...", server.name)

        if server.static_headers:
            if extra_headers is None:
                extra_headers = {}
            extra_headers.update(server.static_headers)

        stdio_env: Final = self._build_stdio_env(server, raw_headers)
        subject_token: Final = self._obo_subject_token(server, raw_headers)

        client: Final = await self._create_mcp_client(
            server=server,
            mcp_auth_header=mcp_auth_header,
            extra_headers=extra_headers,
            stdio_env=stdio_env,
            subject_token=subject_token,
        )

        return await client.read_resource(url)

    async def get_prompt_from_server(
        self,
        server: MCPServer,
        prompt_name: str,
        arguments: dict[str, str] | None = None,
        mcp_auth_header: str | dict[str, str] | None = None,
        extra_headers: dict[str, str] | None = None,
        raw_headers: dict[str, str] | None = None,
    ) -> GetPromptResult:
        """Fetch a specific prompt definition from a single MCP server."""

        verbose_logger.debug("Connecting to url: %s", server.url)
        verbose_logger.info("get_prompt_from_server for %s...", server.name)

        if server.static_headers:
            if extra_headers is None:
                extra_headers = {}
            extra_headers.update(server.static_headers)

        stdio_env: Final = self._build_stdio_env(server, raw_headers)
        subject_token: Final = self._obo_subject_token(server, raw_headers)

        client: Final = await self._create_mcp_client(
            server=server,
            mcp_auth_header=mcp_auth_header,
            extra_headers=extra_headers,
            stdio_env=stdio_env,
            subject_token=subject_token,
        )

        get_prompt_request_params: Final = GetPromptRequestParams(
            name=prompt_name,
            arguments=arguments,
        )
        return await client.get_prompt(get_prompt_request_params)

    @staticmethod
    def _is_same_authority_metadata_url(url: str, server_url: str) -> bool:
        """
        Whether ``url`` shares scheme, host, and port with ``server_url``.

        Same-authority metadata URLs are produced by our well-known discovery
        construction and by resource servers that publish protected-resource
        metadata on the resource origin. These must keep working for
        administrator-configured internal MCP servers, so they are fetched
        directly. Cross-origin URLs are fetched through ``async_safe_get``.
        """
        try:
            target: Final = urlparse(url)
            base: Final = urlparse(server_url)
        except Exception:
            return False

        if target.scheme not in ("http", "https") or not target.hostname:
            return False

        target_port: Final = target.port or (443 if target.scheme == "https" else 80)
        base_port: Final = base.port or (443 if base.scheme == "https" else 80)
        return (
            base.scheme == target.scheme
            and (base.hostname or "").lower() == target.hostname.lower()
            and base_port == target_port
        )

    async def _fetch_oauth_discovery_url(self, url: str, server_url: str) -> httpx.Response:
        client: Final = get_async_httpx_client(
            llm_provider=httpxSpecialProvider.MCP,
            params={"timeout": MCP_METADATA_TIMEOUT},
        )
        if self._is_same_authority_metadata_url(url, server_url):
            # Same-authority URLs may point at administrator-configured
            # internal MCP servers. Do not run them through user URL
            # validation, but also do not follow redirects because the
            # redirect target would not inherit the same-authority guarantee.
            return await client.get(url, follow_redirects=False)
        return await async_safe_get(client, url)

    async def _descovery_metadata(
        self,
        server_url: str,
        *,
        allow_origin_fallback: bool = True,
        warn_when_no_metadata: bool = False,
    ) -> MCPOAuthMetadata | None:
        """Discover OAuth metadata by following RFC 9728 (protected resource metadata discovery).

        ``allow_origin_fallback`` controls the last-resort guess that treats the resource server's own
        origin as its authorization server when nothing is advertised. The browser ``oauth2`` flow keeps
        it (a human sees the redirect), but token_exchange (OBO) sets it False so the gateway never
        exchanges a subject token against an endpoint it inferred rather than one explicitly configured
        or authoritatively advertised via RFC 9728 / RFC 8414.

        ``warn_when_no_metadata`` makes an all-empty result log one WARNING with the per-step attempt
        outcomes (LIT-4658), so a misconfigured server url is diagnosable from default-level logs. The
        server loaders set it; the issuer-anchored resource-scopes lookup keeps it off because empty
        scopes are not a fault there.
        """
        metadata, attempts = await self._discover_metadata_recording_attempts(
            server_url, allow_origin_fallback=allow_origin_fallback
        )
        if metadata is None and warn_when_no_metadata:
            verbose_logger.warning(
                "MCP OAuth endpoint discovery against %s found no authorization server metadata. Attempts: %s. "
                "The MCP server url may be misconfigured, or the upstream may not support OAuth discovery "
                "(RFC 9728 / RFC 8414)",
                _redact_mcp_resource_url(server_url) or "<unparseable url>",
                "; ".join(attempts) if attempts else "none recorded",
            )
        return metadata

    async def _discover_metadata_recording_attempts(
        self,
        server_url: str,
        *,
        allow_origin_fallback: bool,
    ) -> tuple[MCPOAuthMetadata | None, tuple[str, ...]]:
        origin: Final = _redact_mcp_resource_url(server_url) or "<unparseable url>"
        try:
            client: Final = get_async_httpx_client(
                llm_provider=httpxSpecialProvider.MCP,
                params={"timeout": MCP_METADATA_TIMEOUT},  # mutable-ok: HTTP client factory requires a dict
            )
            response: Final = await client.get(server_url)
            response.raise_for_status()
            (
                authorization_servers,
                resource_scopes,
            ) = await self._attempt_well_known_discovery(server_url)
            metadata: Final = await self._fetch_authorization_server_metadata(authorization_servers, server_url)
            if metadata is None and not resource_scopes and authorization_servers and response.status_code == 200:
                verbose_logger.warning(
                    "MCP OAuth discovery for %s received 200 OK without RFC 9728 challenge and no discoverable authorization metadata.",
                    origin,
                )
            attempts: Final = (
                f"GET {origin}: HTTP {response.status_code} (no RFC 9728 challenge)",
                *(
                    ("well-known protected-resource lookup found no authorization servers",)
                    if not authorization_servers
                    else ()
                ),
                *(
                    (f"authorization server metadata fetch failed for: {_redacted_origin_list(authorization_servers)}",)
                    if authorization_servers and metadata is None
                    else ()
                ),
            )
            if metadata is None and resource_scopes:
                return MCPOAuthMetadata(scopes=resource_scopes), attempts
            if metadata is not None and resource_scopes:
                metadata.scopes = resource_scopes
            return metadata, attempts
        except HTTPStatusError as exc:
            return await self._discover_after_status_error(server_url, exc, allow_origin_fallback=allow_origin_fallback)
        except Exception as exc:  # pragma: no cover - network/transient issues
            verbose_logger.debug("MCP OAuth discovery failed for %s: %s", server_url, exc)
            return None, (f"GET {origin}: {type(exc).__name__}: {_sanitized_error_text(exc)}",)

    async def _discover_after_status_error(
        self,
        server_url: str,
        exc: HTTPStatusError,
        *,
        allow_origin_fallback: bool,
    ) -> tuple[MCPOAuthMetadata | None, tuple[str, ...]]:
        origin: Final = _redact_mcp_resource_url(server_url) or "<unparseable url>"
        verbose_logger.debug(
            "MCP OAuth discovery for %s received status error: %s",
            server_url,
            exc,
        )

        header_value: str | None = None
        if exc.response is not None:
            header_value = exc.response.headers.get("WWW-Authenticate") or exc.response.headers.get("www-authenticate")
        status_attempt: Final = (
            f"GET {origin}: HTTP {exc.response.status_code}"
            if exc.response is not None
            else f"GET {origin}: status error"
        )

        resource_metadata_url, scopes = self._parse_www_authenticate_header(header_value)

        authorization_servers = []
        resource_scopes = None
        if resource_metadata_url:
            (
                authorization_servers,
                resource_scopes,
            ) = await self._fetch_oauth_metadata_from_resource(resource_metadata_url, server_url)
            lookup_attempt = (
                None
                if authorization_servers
                else "challenge-advertised resource metadata yielded no authorization servers"
            )
        else:
            (
                authorization_servers,
                resource_scopes,
            ) = await self._attempt_well_known_discovery(server_url)
            lookup_attempt = (
                None
                if authorization_servers
                else "no challenge-advertised resource metadata; well-known protected-resource lookup found no authorization servers"
            )

        metadata = None
        used_origin_fallback = False
        if allow_origin_fallback and not authorization_servers:
            try:
                parsed_url: Final = urlparse(server_url)
                if parsed_url.scheme and parsed_url.netloc:
                    authorization_servers = [f"{parsed_url.scheme}://{parsed_url.netloc}"]
                    used_origin_fallback = True
            except Exception:
                authorization_servers = []

        fallback_attempt = None
        if authorization_servers:
            metadata = await self._fetch_authorization_server_metadata(authorization_servers, server_url)
            if metadata is not None and used_origin_fallback:
                metadata.from_origin_fallback = True
            if metadata is None:
                fallback_attempt = (
                    f"origin fallback: no authorization server metadata at {origin}"
                    if used_origin_fallback
                    else f"authorization server metadata fetch failed for: {_redacted_origin_list(authorization_servers)}"
                )

        attempts: Final = tuple(entry for entry in (status_attempt, lookup_attempt, fallback_attempt) if entry)

        preferred_scopes: Final = scopes or resource_scopes
        if metadata is None and preferred_scopes:
            return MCPOAuthMetadata(scopes=preferred_scopes), attempts
        if metadata is not None and preferred_scopes:
            metadata.scopes = preferred_scopes

        return metadata, attempts

    def _parse_www_authenticate_header(self, header_value: str | None) -> tuple[str | None, list[str] | None]:
        if not header_value:
            return None, None

        _, _, params_section = header_value.partition(" ")
        params_section = params_section or header_value

        param_pattern: Final = re.compile(r"([a-zA-Z0-9_]+)\s*=\s*\"?([^\",]+)\"?")
        params: Final[dict[str, str]] = {
            match.group(1).lower(): match.group(2).strip() for match in param_pattern.finditer(params_section)
        }

        resource_metadata_url: Final = params.get("resource_metadata")

        scope_value: Final = params.get("scope")
        scopes_list: Final = [s for s in (scope_value.split() if scope_value else []) if s]
        scopes: Final = scopes_list or None

        return resource_metadata_url, scopes

    async def _fetch_oauth_metadata_from_resource(
        self, resource_metadata_url: str, server_url: str
    ) -> tuple[list[str], list[str] | None]:
        if not resource_metadata_url:
            return [], None

        try:
            response: Final = await self._fetch_oauth_discovery_url(resource_metadata_url, server_url)
            response.raise_for_status()
            data: Final[_ProtectedResourceMetadataPayload] = response.json()
        except SSRFError as exc:
            verbose_logger.warning(
                "MCP OAuth discovery: refusing to fetch resource metadata from %s "
                "(rejected by SSRF guard for server %s): %s",
                resource_metadata_url,
                server_url,
                exc,
            )
            return [], None
        except Exception as exc:  # pragma: no cover - network issues
            verbose_logger.debug(
                "Failed to fetch MCP OAuth metadata from %s: %s",
                resource_metadata_url,
                exc,
            )
            return [], None

        raw_servers: Final = data.get("authorization_servers")
        if isinstance(raw_servers, list):
            authorization_servers = [entry for entry in raw_servers if isinstance(entry, str) and entry.strip() != ""]
        else:
            authorization_servers = []

        scopes: Final = self._extract_scopes(data.get("scopes_supported") or data.get("scopes"))

        return authorization_servers, scopes

    async def _attempt_well_known_discovery(self, server_url: str) -> tuple[list[str], list[str] | None]:
        try:
            parsed: Final = urlparse(server_url)
        except Exception:
            return [], None

        if not parsed.scheme or not parsed.netloc:
            return [], None

        base: Final = f"{parsed.scheme}://{parsed.netloc}"
        path = parsed.path or ""
        path = path.strip("/")

        candidate_urls: Final[list[str]] = []
        if path:
            candidate_urls.append(f"{base}/.well-known/oauth-protected-resource/{path}")
        candidate_urls.append(f"{base}/.well-known/oauth-protected-resource")

        for url in candidate_urls:
            (
                authorization_servers,
                scopes,
            ) = await self._fetch_oauth_metadata_from_resource(url, server_url)
            if authorization_servers:
                return authorization_servers, scopes

        return [], None

    async def _fetch_authorization_server_metadata(
        self, authorization_servers: list[str], server_url: str
    ) -> MCPOAuthMetadata | None:
        for issuer in authorization_servers:
            metadata = await self._fetch_single_authorization_server_metadata(issuer, server_url)
            if metadata is not None:
                return metadata
        return None

    async def _fetch_issuer_anchored_oauth_metadata(
        self, issuer: str, server_url: str | None
    ) -> MCPOAuthMetadata | None:
        """RFC 8414 issuer-anchored discovery for the OAuth endpoints, with resource-driven scopes.

        Fetch authorization-server metadata from the admin-configured issuer's own origin and adopt
        its ``token_endpoint``/``registration_endpoint`` only when the document self-attests that same
        issuer (RFC 8414 §3.3). Because the trust anchor is the pinned issuer rather than anything the
        MCP resource advertises, the endpoints are authoritative for that issuer and cannot be
        substituted by a compromised resource. Fails closed (returns None) on a §3.3 mismatch or a
        fetch failure. The issuer is passed as its own ``server_url`` so the endpoint fetch is treated
        as same-authority and is not subject to the resource-scoped SSRF shortcut.

        Scopes are NOT taken from the issuer document. Per the MCP authorization spec Scope Selection
        Strategy and RFC 9728, the scopes a client requests are resource-driven (the WWW-Authenticate
        challenge or the protected-resource ``scopes_supported``), so the resource's advertised scopes
        are fetched separately and used; the resource can influence only the requested scope, which
        the authorization server and user consent bound (RFC 6749 §3.3), never the token endpoint.
        """
        metadata: Final = await self._fetch_single_authorization_server_metadata(issuer, issuer, require_issuer=issuer)
        if metadata is None:
            verbose_logger.warning(
                "MCP OAuth issuer-anchored discovery for issuer %s yielded no metadata whose issuer "
                "matched (RFC 8414 §3.3); OAuth endpoints stay unresolved until a rebuild succeeds",
                issuer,
            )
            return None
        resource_metadata: Final = (
            await self._descovery_metadata(server_url, allow_origin_fallback=False) if server_url else None
        )
        resource_scopes: Final = resource_metadata.scopes if resource_metadata else None
        return metadata.model_copy(update={"scopes": resource_scopes})

    async def _fetch_single_authorization_server_metadata(
        self, issuer_url: str, server_url: str, require_issuer: str | None = None
    ) -> MCPOAuthMetadata | None:
        try:
            parsed: Final = urlparse(issuer_url)
        except Exception:
            return None

        if not parsed.scheme or not parsed.netloc:
            return None

        base: Final = f"{parsed.scheme}://{parsed.netloc}"
        path: Final = (parsed.path or "").strip("/")

        candidate_urls: Final[list[str]] = []
        if path:
            candidate_urls.append(f"{base}/.well-known/oauth-authorization-server/{path}")
            candidate_urls.append(f"{base}/.well-known/openid-configuration/{path}")
            candidate_urls.append(f"{issuer_url.rstrip('/')}/.well-known/openid-configuration")
        candidate_urls.append(f"{base}/.well-known/oauth-authorization-server")
        candidate_urls.append(f"{base}/.well-known/openid-configuration")
        candidate_urls.append(issuer_url.rstrip("/"))

        for url in candidate_urls:
            try:
                response = await self._fetch_oauth_discovery_url(url, server_url)
                response.raise_for_status()
                data: _AuthorizationServerMetadataPayload = response.json()
            except SSRFError as exc:
                verbose_logger.warning(
                    "MCP OAuth discovery: refusing to fetch authorization-server "
                    "metadata from %s (rejected by SSRF guard for server %s): %s",
                    url,
                    server_url,
                    exc,
                )
                continue
            except Exception as exc:  # pragma: no cover - network issues
                verbose_logger.debug(
                    "Failed to fetch authorization metadata from %s: %s",
                    url,
                    exc,
                )
                continue

            claimed_issuer = data.get("issuer")
            verbose_logger.debug(
                "Authorization server metadata from %s: issuer=%s grant_types_supported=%s "
                "token_endpoint_auth_methods_supported=%s",
                url,
                claimed_issuer,
                data.get("grant_types_supported"),
                data.get("token_endpoint_auth_methods_supported"),
            )
            if require_issuer is not None and not _issuer_matches(claimed_issuer, require_issuer):
                verbose_logger.warning(
                    "MCP OAuth issuer-anchored discovery: metadata at %s self-attests issuer %r, which "
                    "does not match the configured issuer %r (RFC 8414 §3.3); rejecting so a compromised "
                    "resource cannot substitute an attacker authorization server",
                    url,
                    claimed_issuer,
                    require_issuer,
                )
                continue

            scopes = self._extract_scopes(data.get("scopes_supported"))
            metadata = MCPOAuthMetadata(
                scopes=scopes,
                authorization_url=data.get("authorization_endpoint"),
                token_url=data.get("token_endpoint"),
                registration_url=data.get("registration_endpoint"),
                discovered_issuer=claimed_issuer if isinstance(claimed_issuer, str) and claimed_issuer else None,
            )

            if any(
                [
                    metadata.scopes,
                    metadata.authorization_url,
                    metadata.token_url,
                    metadata.registration_url,
                ]
            ):
                return metadata

        return self._build_azure_authorization_server_metadata(parsed)

    @staticmethod
    def _build_azure_authorization_server_metadata(
        parsed_issuer_url: ParseResult,
    ) -> MCPOAuthMetadata | None:
        path_parts: Final = [part for part in (parsed_issuer_url.path or "").split("/") if part]
        if parsed_issuer_url.netloc not in _AZURE_ENTRA_HOSTS or len(path_parts) != 2 or path_parts[1] != "v2.0":
            return None

        tenant: Final = path_parts[0]
        base: Final = f"{parsed_issuer_url.scheme}://{parsed_issuer_url.netloc}/{tenant}"
        return MCPOAuthMetadata(
            authorization_url=f"{base}/oauth2/v2.0/authorize",
            token_url=f"{base}/oauth2/v2.0/token",
        )

    @staticmethod
    def _decrypt_credential_field(
        encrypted_value: str | None,
        key: str,
        credentials_are_encrypted: bool,
    ) -> str | None:
        """Decrypt a single credential field, or return as-is if not encrypted."""
        if not encrypted_value:
            return None
        if credentials_are_encrypted:
            return decrypt_value_helper(
                value=encrypted_value,
                key=key,
                exception_type="debug",
                return_original_value=True,
            )
        return encrypted_value

    def _extract_aws_credentials(
        self,
        credentials_dict: dict[str, str] | None,
        credentials_are_encrypted: bool,
    ) -> dict[str, str | None]:
        """Extract and decrypt AWS SigV4 credential fields from credentials dict."""
        if not credentials_dict:
            return {}
        return {
            "aws_access_key_id": self._decrypt_credential_field(
                credentials_dict.get("aws_access_key_id"),
                "aws_access_key_id",
                credentials_are_encrypted,
            ),
            "aws_secret_access_key": self._decrypt_credential_field(
                credentials_dict.get("aws_secret_access_key"),
                "aws_secret_access_key",
                credentials_are_encrypted,
            ),
            "aws_session_token": self._decrypt_credential_field(
                credentials_dict.get("aws_session_token"),
                "aws_session_token",
                credentials_are_encrypted,
            ),
            "aws_region_name": credentials_dict.get("aws_region_name"),
            "aws_service_name": credentials_dict.get("aws_service_name"),
            "aws_role_name": credentials_dict.get("aws_role_name"),
            "aws_session_name": credentials_dict.get("aws_session_name"),
        }

    def _extract_scopes(self, scopes_value: str | Sequence[object] | None) -> list[str] | None:
        if isinstance(scopes_value, str):
            scopes = [s.strip() for s in scopes_value.split() if s.strip()]
            return scopes or None
        if isinstance(scopes_value, list):
            scopes = [s for s in scopes_value if isinstance(s, str) and s.strip()]
            return scopes or None
        return None

    async def _fetch_tools_with_timeout(
        self,
        client: MCPClient,
        server_name: str,
    ) -> list[MCPTool]:
        """
        Fetch tools from MCP client with timeout and error handling.

        Uses anyio.fail_after() instead of asyncio.wait_for() to avoid conflicts
        with the MCP SDK's anyio TaskGroup. See GitHub issue #20715 for details.

        Failures never return an empty tool list. An upstream 401 or 403 raises
        :class:`MCPUpstreamAuthError` carrying the upstream's own
        ``WWW-Authenticate`` challenge when one was sent (a challenge is only
        ever fabricated at the HTTP edge, and only for a 401: a 403 means the
        caller is authenticated but not allowed, so prompting re-auth would be
        wrong, while an upstream-sent 403 challenge is the RFC 6750
        insufficient_scope step-up and relays verbatim). Every other failure
        raises :class:`MCPServerListError` with a classified fault. Each
        boundary then applies its own policy: single-server routes relay the
        truthful status, the multi-server aggregator absorbs the failure into
        that server's listing outcome.

        Args:
            client: MCP client instance
            server_name: Name of the server for logging

        Returns:
            List of tools from the server
        """
        try:
            with anyio.fail_after(MCP_TOOL_LISTING_TIMEOUT):
                tools: Final = await client.list_tools(raise_on_error=True)
                verbose_logger.debug("Tools from %s: %s", server_name, tools)
                return tools
        except TimeoutError as e:
            verbose_logger.warning("Timeout while listing tools from %s", server_name)
            raise MCPServerListError(ServerListFault(tag="timeout"), server_name) from e
        except asyncio.CancelledError as e:
            verbose_logger.warning("Task cancelled while listing tools from %s", server_name)
            raise MCPServerListError(ServerListFault(tag="internal"), server_name) from e
        except ConnectionError as e:
            verbose_logger.warning("Connection error while listing tools from %s: %s", server_name, e)
            raise MCPServerListError(ServerListFault(tag="unreachable"), server_name) from e
        except Exception as e:
            verbose_logger.warning("Error listing tools from %s: %s", server_name, e)
            raise_classified_list_failure(e, server_name)

    _SHORT_PREFIX_MAX_REHASH_ATTEMPTS = 1024

    def _assign_unique_short_prefix(
        self,
        server: MCPServer,
        registry: dict[str, MCPServer] | None = None,
    ) -> None:
        """Resolve and cache a collision-free short tool prefix on ``server``.

        Called at registration time for every MCP server entering the
        registry.  Mutates ``server.short_prefix`` in place.  No-ops when
        ``LITELLM_USE_SHORT_MCP_TOOL_PREFIX`` is disabled, when the server
        has no ``server_id`` (synthetic temp-server objects), or when a
        prefix is already cached.

        Collision strategy: take the natural hash; if it's already used by
        a *different* server in the combined registry, rehash with an
        incrementing attempt counter until we find an unused slot.  The
        attempt counter is folded into the hash so the resulting prefix is
        still deterministic for a given (server_id, set-of-other-server-ids)
        pair within one process.
        """
        if not is_short_mcp_tool_prefix_enabled():
            return
        if server.short_prefix:
            return
        if not server.server_id:
            return

        used: Final[dict[str, str]] = {}
        registry_for_collision_check: Final = registry or self.get_registry()
        for other in registry_for_collision_check.values():
            if other.server_id == server.server_id:
                continue
            if other.short_prefix:
                used[other.short_prefix] = other.server_id

        for attempt in range(self._SHORT_PREFIX_MAX_REHASH_ATTEMPTS):
            candidate = compute_short_server_prefix(server.server_id, attempt=attempt)
            if candidate not in used:
                server.short_prefix = candidate
                if attempt > 0:
                    verbose_logger.info(
                        "MCP short-prefix collision resolved for server %s: "
                        "natural hash collided with %s, using rehashed prefix "
                        "%s (attempt=%d).",
                        server.server_id,
                        used.get(
                            compute_short_server_prefix(server.server_id, attempt=0),
                            "<unknown>",
                        ),
                        candidate,
                        attempt,
                    )
                return

        raise RuntimeError(
            f"Unable to assign a unique short MCP tool prefix for server "
            f"{server.server_id} after {self._SHORT_PREFIX_MAX_REHASH_ATTEMPTS} "
            "attempts; the 3-character prefix space is too crowded."
        )

    def _create_prefixed_tools(self, tools: list[MCPTool], server: MCPServer, add_prefix: bool = True) -> list[MCPTool]:
        """
        Create prefixed tools and update tool mapping.

        Args:
            tools: List of original tools from server
            server: Server instance

        Returns:
            List of tools with prefixed names
        """
        prefixed_tools: Final = []
        prefix: Final = get_server_prefix(server)

        for tool in tools:
            tool_copy = tool.model_copy(deep=True)

            original_name = tool_copy.name
            prefixed_name = add_server_prefix_to_name(original_name, prefix)

            name_to_use = prefixed_name if add_prefix else original_name

            # Preserve all tool fields including metadata/_meta by avoiding mutation
            tool_copy.name = name_to_use
            prefixed_tools.append(tool_copy)

            # Register every known prefix form (alias, server_name, server_id,
            # short ID) so call_tool can resolve regardless of which form a
            # caller / cached client is using.
            for spelling in iter_known_tool_name_spellings(original_name, server):
                self.tool_name_to_mcp_server_name_mapping[spelling] = prefix

        verbose_logger.info("Successfully fetched %s tools from server %s", len(prefixed_tools), server.name)
        return prefixed_tools

    def _create_prefixed_prompts(
        self, prompts: list[Prompt], server: MCPServer, add_prefix: bool = True
    ) -> list[Prompt]:
        """
        Create prefixed prompts and update prompt mapping.

        Args:
            prompts: List of original prompts from server
            server: Server instance

        Returns:
            List of prompts with prefixed names
        """
        prefixed_prompts: Final = []
        prefix: Final = get_server_prefix(server)

        for prompt in prompts:
            prefixed_name = add_server_prefix_to_name(prompt.name, prefix)

            name_to_use = prefixed_name if add_prefix else prompt.name

            prompt.name = name_to_use
            prefixed_prompts.append(prompt)

        verbose_logger.info("Successfully fetched %s prompts from server %s", len(prefixed_prompts), server.name)
        return prefixed_prompts

    def _create_prefixed_resources(
        self, resources: list[Resource], server: MCPServer, add_prefix: bool = True
    ) -> list[Resource]:
        """Prefix resource names and track origin server for read requests."""

        prefixed_resources: Final[list[Resource]] = []
        prefix: Final = get_server_prefix(server)

        for resource in resources:
            name_to_use = add_server_prefix_to_name(resource.name, prefix) if add_prefix else resource.name
            resource.name = name_to_use
            prefixed_resources.append(resource)

        verbose_logger.info("Successfully fetched %s resources from server %s", len(prefixed_resources), server.name)
        return prefixed_resources

    def _create_prefixed_resource_templates(
        self,
        resource_templates: list[ResourceTemplate],
        server: MCPServer,
        add_prefix: bool = True,
    ) -> list[ResourceTemplate]:
        """Prefix resource template names for multi-server scenarios."""

        prefixed_templates: Final[list[ResourceTemplate]] = []
        prefix: Final = get_server_prefix(server)

        for resource_template in resource_templates:
            name_to_use = (
                add_server_prefix_to_name(resource_template.name, prefix) if add_prefix else resource_template.name
            )
            resource_template.name = name_to_use
            prefixed_templates.append(resource_template)

        verbose_logger.info(
            "Successfully fetched %s resource templates from server %s", len(prefixed_templates), server.name
        )
        return prefixed_templates

    def check_allowed_or_banned_tools(self, tool_name: str, server: MCPServer) -> bool:
        """
        Check if the tool is allowed or banned for the given server.

        ``tool_name`` is bare: every caller resolves the boundary against the server's
        registered prefixes before dispatch (``server.py``'s ``original_tool_name``, the
        Responses handler's ``sanitized_tool_name``). Configured entries are matched by
        deriving the spellings routing accepts, never by stripping the entry, which would
        cut a second boundary out of a native name that opens with the server prefix.
        """
        from litellm.proxy._experimental.mcp_server.utils import (
            server_applies_tool_allowlist,
        )

        if server_applies_tool_allowlist(server):
            return match_known_tool_name(tool_name, server, server.allowed_tools or ()) is not None
        return match_known_tool_name(tool_name, server, server.disallowed_tools or ()) is None

    def validate_allowed_params(self, tool_name: str, arguments: _ToolArguments, server: MCPServer) -> None:
        """
        Filter arguments to only include allowed parameters for the given tool.

        Args:
            tool_name: Bare tool name, already resolved against the server's
                registered prefixes by the caller
            arguments: Dictionary of arguments to filter
            server: MCPServer configuration

        Returns:
            Filtered dictionary containing only allowed parameters

        Raises:
            HTTPException: If allowed_params is configured for this tool but arguments contain disallowed params
        """
        allowed_params: Final = server.allowed_params or {}
        matched: Final = match_known_tool_name(tool_name, server, allowed_params)
        if matched is None:
            return

        allowed_params_list: Final = allowed_params[matched]

        # Filter arguments to only include allowed parameters
        disallowed_params: Final = [param for param in arguments if param not in allowed_params_list]

        if disallowed_params:
            raise HTTPException(
                status_code=403,
                detail={
                    "error": f"Parameters {disallowed_params} are not allowed for tool {tool_name}. "
                    f"Allowed parameters: {allowed_params_list}. "
                    f"Contact proxy admin to allow these parameters."
                },
            )

    async def check_tool_permission_for_key_team(
        self,
        tool_name: str,
        server: MCPServer,
        user_api_key_auth: UserAPIKeyAuth | None,
    ) -> None:
        """
        Check if a tool is allowed based on key/team object_permission.mcp_tool_permissions.
        Uses MCPRequestHandler.is_tool_allowed_for_server for consistent inheritance logic.
        Raises HTTPException if tool is not allowed.

        Args:
            tool_name: Name of the tool to check
            server: MCPServer object
            user_api_key_auth: User authentication

        Raises:
            HTTPException: If tool is not allowed for this key/team
        """
        from litellm.proxy._experimental.mcp_server.auth.user_api_key_auth_mcp import (
            MCPRequestHandler,
        )

        if not user_api_key_auth:
            return

        # Check if tool is allowed
        is_allowed: Final = await MCPRequestHandler.is_tool_allowed_for_server(
            tool_name=tool_name,
            server_id=server.server_id,
            user_api_key_auth=user_api_key_auth,
        )

        if not is_allowed:
            raise HTTPException(
                status_code=403,
                detail={
                    "error": f"Tool '{tool_name}' is not allowed for your key/team on server '{server.name}'. Contact proxy admin for access."
                },
            )

    async def _call_openapi_tool_handler(
        self,
        server: MCPServer,
        tool_name: str,
        arguments: _ToolArguments,
    ) -> CallToolResult:
        """
        Call an OpenAPI tool handler directly.

        For OpenAPI servers, instead of using MCP protocol, we call the tool handler
        that was registered during OpenAPI spec parsing. This handler makes direct
        HTTP requests to the API.

        Args:
            tool_name: The full tool name (with prefix) to call
            arguments: Tool arguments to pass to the handler

        Returns:
            CallToolResult with the response from the API
        """
        from mcp.types import TextContent

        from litellm.proxy._experimental.mcp_server.tool_registry import (
            global_mcp_tool_registry,
        )

        # Registration used add_server_prefix_to_name(base, get_server_prefix(server)),
        # and tool_name is the bare base name by the time call_tool reaches here, so
        # rebuilding the key the same way reproduces it exactly
        registry_key: Final = add_server_prefix_to_name(tool_name, get_server_prefix(server))
        tool: Final = global_mcp_tool_registry.get_tool(registry_key)
        if tool is None:
            # Tool not found in registry
            error_msg = f"OpenAPI tool {tool_name} not found in registry"
            verbose_logger.error(error_msg)
            return CallToolResult(
                content=[TextContent(type="text", text=error_msg)],
                isError=True,
            )

        try:
            # Call the tool handler with the arguments
            # The handler is an async function that makes the HTTP request
            handler_result: Final = await tool.handler(**arguments)

            # Convert the handler result (string response) to CallToolResult format
            result: Final = CallToolResult(
                content=[TextContent(type="text", text=str(handler_result))],
                isError=False,
            )

            return result

        except MCPUpstreamAuthError:
            # The caller must re-authenticate upstream, so this keeps its type all the way to the
            # renderers: the streamable path turns it into an isError result naming the status, and
            # the REST path relays a real 401 with the upstream's WWW-Authenticate. Flattening it
            # into the generic message below would lose both.
            raise
        except Exception as e:
            error_msg = f"Error calling OpenAPI tool {tool_name}: {e}"
            verbose_logger.error(error_msg)
            return CallToolResult(
                content=[TextContent(type="text", text=error_msg)],
                isError=True,
            )

    async def pre_call_tool_check(
        self,
        name: str,
        arguments: dict[str, Any],
        server_name: str,
        user_api_key_auth: UserAPIKeyAuth | None,
        proxy_logging_obj: ProxyLogging | None,
        server: MCPServer,
        raw_headers: dict[str, str] | None = None,
        litellm_logging_obj: "LiteLLMLoggingObj | None" = None,
    ) -> dict[str, Any]:
        """
        Run pre-call checks and guardrail hooks for an MCP tool call.

        Authorization runs unconditionally; only the guardrail hooks, which are
        dispatched through ``proxy_logging_obj``, depend on a logger being
        present. An absent logger must never be able to turn an authorization
        decision into a no-op.

        ``litellm_logging_obj`` is the request's logger, and it is what lands a
        ``pre_mcp_call`` evaluation (or a block) on the spend-log row the Guardrails
        Monitor counts. It stays optional so callers that do no logging are unchanged.

        Returns a dict that may contain:
        - "arguments": hook-modified tool arguments (only if changed)
        - "extra_headers": headers injected by pre_mcp_call guardrail hooks
        """
        ## check if the tool is allowed or banned for the given server
        if not self.check_allowed_or_banned_tools(name, server):
            raise HTTPException(
                status_code=403,
                detail={
                    "error": f"Tool {name} is not allowed for server {server.name}. Contact proxy admin to allow this tool."
                },
            )

        ## check tool-level permissions from object_permission
        await self.check_tool_permission_for_key_team(
            tool_name=name,
            server=server,
            user_api_key_auth=user_api_key_auth,
        )

        ## filter parameters based on allowed_params configuration
        self.validate_allowed_params(
            tool_name=name,
            arguments=arguments,
            server=server,
        )

        hook_result: Final[dict[str, Any]] = {}
        if proxy_logging_obj is None:
            return hook_result

        # Extract incoming Bearer token from raw request headers so
        # guardrails like MCPJWTSigner can verify + re-sign it (FR-5).
        normalized_raw: Final = {k.lower(): v for k, v in (raw_headers or {}).items()}
        incoming_bearer_token: str | None = None
        auth_hdr: Final = normalized_raw.get("authorization", "")
        if auth_hdr.lower().startswith("bearer "):
            incoming_bearer_token = auth_hdr[len("bearer ") :]

        pre_hook_kwargs: Final = {
            "name": name,
            "arguments": arguments,
            "server_name": server_name,
            "mcp_rate_limit_server_name": server.alias or server.server_name or server.name,
            "user_api_key_auth": user_api_key_auth,
            "user_api_key_user_id": (getattr(user_api_key_auth, "user_id", None) if user_api_key_auth else None),
            "user_api_key_team_id": (getattr(user_api_key_auth, "team_id", None) if user_api_key_auth else None),
            "user_api_key_end_user_id": (
                getattr(user_api_key_auth, "end_user_id", None) if user_api_key_auth else None
            ),
            "user_api_key_hash": (getattr(user_api_key_auth, "api_key_hash", None) if user_api_key_auth else None),
            "incoming_bearer_token": incoming_bearer_token,
            "headers": logging_safe_mcp_headers(raw_headers),
        }

        # Create MCP request object for processing
        mcp_request_obj: Final = proxy_logging_obj._create_mcp_request_object_from_kwargs(pre_hook_kwargs)

        # Convert to LLM format for existing guardrail compatibility.
        # Unified guardrails read the seeded logger off the request dict and pass it
        # into ``apply_guardrail``, so ``@log_guardrail_information`` bridges their
        # evaluations itself; the ``finally`` below covers native guardrails, which
        # never receive it. Same seeding the pass-through routes do.
        synthetic_llm_data: Final = proxy_logging_obj._convert_mcp_to_llm_format(mcp_request_obj, pre_hook_kwargs)
        synthetic_llm_data["litellm_logging_obj"] = litellm_logging_obj

        try:
            # Use standard pre_call_hook
            modified_data: Final = await proxy_logging_obj.pre_call_hook(
                user_api_key_dict=user_api_key_auth,
                data=synthetic_llm_data,
                call_type=CallTypes.call_mcp_tool.value,
            )
            if modified_data:
                # Convert response back to MCP format and apply modifications
                modified_kwargs = proxy_logging_obj._convert_mcp_hook_response_to_kwargs(modified_data, pre_hook_kwargs)
                if modified_kwargs.get("arguments") != arguments:
                    hook_result["arguments"] = modified_kwargs["arguments"]
                if modified_kwargs.get("extra_headers"):
                    hook_result["extra_headers"] = modified_kwargs["extra_headers"]

        except (
            BlockedPiiEntityError,
            GuardrailRaisedException,
            HTTPException,
        ) as e:
            # Re-raise guardrail exceptions to properly fail the MCP call
            verbose_logger.error("Guardrail blocked MCP tool call pre call: %s", e)
            raise e
        finally:
            # ``finally`` rather than after the ``try``: a block raises straight out of
            # here, and the failure spend-log row that "Total Blocked" counts is built
            # from this logger further up the stack, so the record has to be attached
            # before the exception leaves this frame.
            _record_mcp_guardrail_evaluations(synthetic_llm_data, litellm_logging_obj)

        return hook_result

    def _create_during_hook_task(
        self,
        name: str,
        arguments: _ToolArguments,
        server_name_from_prefix: str | None,
        user_api_key_auth: UserAPIKeyAuth | None,
        proxy_logging_obj: ProxyLogging,
        start_time: datetime.datetime,
        litellm_logging_obj: "LiteLLMLoggingObj | None" = None,
    ):
        """Create and return a during hook task for MCP tool calls.

        ``litellm_logging_obj`` is the request's logger; see ``pre_call_tool_check``.
        The task is awaited before the tool call's success logging runs, so a
        ``during_mcp_call`` evaluation recorded on it is serialized with that call.
        """
        from litellm.types.llms.base import HiddenParams
        from litellm.types.mcp import MCPDuringCallRequestObject

        request_obj: Final = MCPDuringCallRequestObject(
            tool_name=name,
            arguments=arguments,
            server_name=server_name_from_prefix,
            start_time=start_time.timestamp() if start_time else None,
            hidden_params=HiddenParams(),
        )

        during_hook_kwargs: Final = {
            "name": name,
            "arguments": arguments,
            "server_name": server_name_from_prefix,
            "user_api_key_auth": user_api_key_auth,
        }

        # Seeded for the same reason as in ``pre_call_tool_check``.
        synthetic_llm_data: Final = proxy_logging_obj._convert_mcp_to_llm_format(request_obj, during_hook_kwargs)
        synthetic_llm_data["litellm_logging_obj"] = litellm_logging_obj

        # Wrapped so the bridge runs inside the task: the caller only holds the task and
        # gathers it later, so there is no other point that still sees a block here.
        async def _run_during_call_hook() -> Mapping[str, object] | None:
            try:
                return await proxy_logging_obj.during_call_hook(
                    user_api_key_dict=user_api_key_auth,
                    data=synthetic_llm_data,
                    call_type=CallTypes.call_mcp_tool.value,
                )
            finally:
                _record_mcp_guardrail_evaluations(synthetic_llm_data, litellm_logging_obj)

        return asyncio.create_task(_run_during_call_hook())

    def _get_call_semaphore(self, mcp_server: MCPServer) -> asyncio.Semaphore | None:
        limit: Final = mcp_server.max_concurrent_requests
        if limit is None or limit <= 0:
            return None
        cached: Final = self._server_call_semaphores.get(mcp_server.server_id)
        if cached is not None and cached[0] == limit:
            return cached[1]
        semaphore: Final = asyncio.Semaphore(limit)
        self._server_call_semaphores[mcp_server.server_id] = (limit, semaphore)
        return semaphore

    @asynccontextmanager
    async def _limit_outbound_concurrency(self, mcp_server: MCPServer) -> AsyncIterator[None]:
        semaphore: Final = self._get_call_semaphore(mcp_server)
        if semaphore is None:
            yield
            return
        async with semaphore:
            yield

    async def _obo_call_tool_with_retry(
        self,
        *,
        client: MCPClient,
        call_tool_params: MCPCallToolRequestParams,
        host_progress_callback: Callable | None,
        mcp_server: MCPServer,
        server_auth_header: str | dict[str, str] | None,
        extra_headers: dict[str, str] | None,
        stdio_env: dict[str, str] | None,
        subject_token: str | None,
        user_api_key_auth: UserAPIKeyAuth | None,
    ) -> CallToolResult:
        """Call a token_exchange (OBO) tool; on an upstream 401/403 re-mint the token once and retry.

        The exchanged token is baked into the client at build time, so the retry invalidates the
        cached exchange and rebuilds the client (which re-exchanges). One retry only: a non-auth
        failure or a second auth failure degrades to the normal ``isError`` result, and a re-exchange
        that now fails surfaces its own 401 challenge from ``_create_mcp_client``.
        """
        try:
            return await client.call_tool(
                call_tool_params, host_progress_callback=host_progress_callback, raise_on_error=True
            )
        except Exception as exc:
            if _extract_upstream_auth_failure(exc) is None:
                return MCPClient.error_tool_result(exc)
            spec: Final = to_server_spec(mcp_server)
            if spec is not None:
                await self._cred_provider.invalidate_credentials(to_subject(user_api_key_auth, subject_token), spec)
            retry_client: Final = await self._create_mcp_client(
                server=mcp_server,
                mcp_auth_header=server_auth_header,
                extra_headers=extra_headers,
                stdio_env=stdio_env,
                subject_token=subject_token,
                user_api_key_auth=user_api_key_auth,
            )
            return await retry_client.call_tool(call_tool_params, host_progress_callback=host_progress_callback)

    async def _call_regular_mcp_tool(
        self,
        mcp_server: MCPServer,
        original_tool_name: str,
        arguments: _ToolArguments,
        tasks: list,
        mcp_auth_header: str | None,
        mcp_server_auth_headers: dict[str, dict[str, str]] | None,
        oauth2_headers: dict[str, str] | None,
        raw_headers: dict[str, str] | None,
        proxy_logging_obj: ProxyLogging | None,
        host_progress_callback: Callable | None = None,
        hook_extra_headers: dict[str, str] | None = None,
        user_api_key_auth: UserAPIKeyAuth | None = None,
    ) -> CallToolResult:
        """
        Call a regular MCP tool using the MCP client.

        Args:
            mcp_server: The MCP server configuration
            original_tool_name: The original tool name (without prefix)
            arguments: Tool arguments
            tasks: List of async tasks to append to (for during hooks)
            mcp_auth_header: MCP auth header (deprecated)
            mcp_server_auth_headers: Optional dict of server-specific auth headers
            oauth2_headers: Optional OAuth2 headers
            raw_headers: Optional raw headers from the request
            proxy_logging_obj: Optional ProxyLogging object for hook integration
            host_progress_callback: Optional callback for progress updates
            hook_extra_headers: Optional headers injected by pre_mcp_call guardrail
                hooks. Merged last into outbound request headers, except a hook
                Authorization header is dropped when an upstream credential already
                occupies the Authorization slot.

        Returns:
            CallToolResult from the MCP server

        Raises:
            BlockedPiiEntityError: If PII is blocked by guardrails
            GuardrailRaisedException: If guardrails block the call
            HTTPException: If an HTTP error occurs
        """
        # Get server-specific auth header if available (case-insensitive)
        # FIX: Added case-insensitive matching to handle auth header keys that may not match
        # the exact case of server alias/name (e.g., '1litellmagcgateway' vs '1LiteLLMAGCGateway')
        server_auth_header: dict[str, str] | str | None = None
        if mcp_server_auth_headers:
            server_auth_header = lookup_mcp_server_auth_in_headers(
                mcp_server_auth_headers,
                alias=mcp_server.alias,
                server_name=mcp_server.server_name,
            )

        # Fall back to deprecated mcp_auth_header if no server-specific header found
        if server_auth_header is None:
            server_auth_header = mcp_auth_header

        # Extract subject token for OAuth2 Token Exchange (OBO) and ID-JAG flows
        subject_token: str | None = None
        extra_headers: dict[str, str] | None = None
        if mcp_server.auth_type in (
            MCPAuth.oauth2_token_exchange,
            MCPAuth.oauth2_id_jag,
        ):
            subject_token = self._extract_bearer_token(oauth2_headers, raw_headers)
        elif mcp_server.auth_type == MCPAuth.oauth2:
            if mcp_server.has_client_credentials:
                # For M2M OAuth servers, Authorization must come from token fetch.
                extra_headers = None
            else:
                extra_headers = oauth2_headers
                # Migrated authorization_code: the v2 resolver injects the stored per-user
                # token, so drop the caller-forwarded Authorization (apply-if-absent would
                # otherwise let it shadow the resolved token). Delegate keeps it. Centralized
                # via _should_strip_caller_authorization to match _prepare_mcp_server_headers.
                if extra_headers and _should_strip_caller_authorization(
                    mcp_server=mcp_server,
                    raw_headers=raw_headers,
                    user_api_key_auth=user_api_key_auth,
                ):
                    extra_headers = without_header(extra_headers, DEFAULT_CREDENTIAL_HEADER)
        elif mcp_server.is_client_forwarded_token:
            extra_headers = _client_forwarded_authorization_headers(
                mcp_server=mcp_server,
                oauth2_headers=oauth2_headers,
                raw_headers=raw_headers,
                user_api_key_auth=user_api_key_auth,
            )

        if mcp_server.extra_headers and raw_headers:
            if extra_headers is None:
                extra_headers = {}

            normalized_raw_headers: Final = {str(k).lower(): v for k, v in raw_headers.items() if isinstance(k, str)}
            strip_caller_authorization: Final = _should_strip_caller_authorization(
                mcp_server=mcp_server,
                raw_headers=raw_headers,
                user_api_key_auth=user_api_key_auth,
            )

            for header in mcp_server.extra_headers:
                if not isinstance(header, str):
                    continue
                if header.lower() == "authorization" and strip_caller_authorization:
                    continue
                header_value = normalized_raw_headers.get(header.lower())
                if header_value is None:
                    continue
                extra_headers[header] = header_value

        # Interpolate env vars into static_headers. Raises
        # MCPMissingUserEnvVarsError when the calling user has not filled in
        # a required per-user variable — the REST layer converts that into
        # a friendly 412 with a setup URL.
        resolved_static_headers: Final = await self._resolve_static_headers_with_env_vars(mcp_server, user_api_key_auth)
        if resolved_static_headers:
            if extra_headers is None:
                extra_headers = {}
            extra_headers.update(resolved_static_headers)

        if hook_extra_headers:
            if extra_headers is None:
                extra_headers = {}
            hook_has_authorization: Final = any(k.lower() == "authorization" for k in hook_extra_headers)
            existing_has_authorization: Final = any(k.lower() == "authorization" for k in extra_headers)
            server_auth_occupies_authorization: Final = (
                any(k.lower() == "authorization" for k in server_auth_header)
                if isinstance(server_auth_header, dict)
                else server_auth_header is not None and mcp_server.auth_type != MCPAuth.api_key
            )
            if hook_has_authorization and (existing_has_authorization or server_auth_occupies_authorization):
                # Mirror the tools/list signer guard: an upstream credential (user OAuth,
                # static header, or configured authentication_token) already occupies the
                # Authorization slot, so the hook must not replace it.
                verbose_logger.warning(
                    "MCPServerManager: dropping hook-injected 'Authorization' header for "
                    "server '%s' because an upstream credential already occupies the "
                    "Authorization slot; the existing credential is kept.",
                    mcp_server.server_name or mcp_server.name,
                )
                extra_headers.update({k: v for k, v in hook_extra_headers.items() if k.lower() != "authorization"})
            else:
                extra_headers.update(hook_extra_headers)

        # Reset to None if no headers were actually added
        if extra_headers is not None and len(extra_headers) == 0:
            extra_headers = None

        stdio_env: Final = self._build_stdio_env(mcp_server, raw_headers)

        client: Final = await self._create_mcp_client(
            server=mcp_server,
            mcp_auth_header=server_auth_header,
            extra_headers=extra_headers,
            stdio_env=stdio_env,
            subject_token=subject_token,
            user_api_key_auth=user_api_key_auth,
        )

        call_tool_params: Final = MCPCallToolRequestParams(
            name=original_tool_name,
            arguments=arguments,
        )

        if _obo_retry_applies(mcp_server, subject_token):
            # OBO / ID-JAG: the exchanged token may have been revoked/rotated upstream since it was
            # cached, so an upstream 401 gets one invalidate + re-mint + retry. Gated to these modes;
            # all others keep the plain single call below.
            async def _obo_call_tool_limited():
                async with self._limit_outbound_concurrency(mcp_server):
                    return await self._obo_call_tool_with_retry(
                        client=client,
                        call_tool_params=call_tool_params,
                        host_progress_callback=host_progress_callback,
                        mcp_server=mcp_server,
                        server_auth_header=server_auth_header,
                        extra_headers=extra_headers,
                        stdio_env=stdio_env,
                        subject_token=subject_token,
                        user_api_key_auth=user_api_key_auth,
                    )

            tool_call_coro = _obo_call_tool_limited()
        else:
            # Scoped to the two client-forwarded token modes this stack introduced; legacy
            # oauth2 + delegate_auth_to_upstream (is_oauth_passthrough) is being removed, so it is not
            # added here even though the list path still relays for it.
            relays_upstream_auth: Final = mcp_server.is_client_forwarded_token
            server_label: Final = mcp_server.name or mcp_server.server_name or mcp_server.alias or ""

            async def _call_tool_via_client(client, params):
                async with self._limit_outbound_concurrency(mcp_server):
                    if not relays_upstream_auth:
                        return await client.call_tool(params, host_progress_callback=host_progress_callback)
                    # The client-forwarded modes carry the caller's own upstream token, so an upstream
                    # 401 (expired/invalid token) is the caller's to resolve: relay it as
                    # MCPUpstreamAuthError so single-server REST callers turn it into a 401 +
                    # WWW-Authenticate and re-run the upstream OAuth flow. Only 401 is a re-auth signal
                    # (mirrors the list path and MCPUpstreamAuthError's contract); a 403 is a genuine
                    # authorization failure that re-auth won't fix, so it takes the non-auth branch and
                    # stays a visible warning. raise_on_error only re-raises transport failures
                    # (tool-level isError results are still returned normally); a non-auth failure keeps
                    # the same isError degradation the default path produces.
                    try:
                        return await client.call_tool(
                            params, host_progress_callback=host_progress_callback, raise_on_error=True
                        )
                    except Exception as e:
                        auth_info: Final = _extract_upstream_auth_failure(e)
                        if auth_info is None or auth_info[0] != 401:
                            # A genuine (non-auth or 403-forbidden) upstream/transport failure.
                            # raise_on_error demoted the client-layer log to debug, so surface it here at
                            # warning level to keep the outage visible; the caller still gets the graceful
                            # isError result the default masking path would have produced. Log the
                            # exception type only, never str(e), which for an httpx error embeds the
                            # upstream URL (a credential can hide in it).
                            verbose_logger.warning(
                                "Pass-through MCP tool call failed against %s (non-auth, %s)",
                                server_label,
                                type(e).__name__,
                            )
                            return client.error_tool_result(e)
                        _, www_authenticate = auth_info
                        raise MCPUpstreamAuthError(
                            status_code=401,
                            www_authenticate=www_authenticate,
                            server_name=server_label,
                        ) from e

            tool_call_coro = _call_tool_via_client(client, call_tool_params)

        tasks.append(asyncio.create_task(tool_call_coro))

        _timeout: Final = mcp_server.timeout if mcp_server.timeout is not None else MCP_CLIENT_TIMEOUT
        try:
            mcp_responses: Final = await asyncio.wait_for(asyncio.gather(*tasks), timeout=_timeout)
        except asyncio.TimeoutError:
            raise HTTPException(
                status_code=504,
                detail={
                    "error": "timeout",
                    "message": f"MCP tool call timed out after {_timeout}s",
                },
            )
        except (
            BlockedPiiEntityError,
            GuardrailRaisedException,
            HTTPException,
        ) as e:
            verbose_logger.error("Guardrail blocked MCP tool call during result check: %s", e)
            raise e

        # If proxy_logging_obj is None, the tool call result is at index 0
        # If proxy_logging_obj is not None, the tool call result is at index 1 (after the during hook task)
        result_index: Final = 1 if proxy_logging_obj else 0
        result: Final = mcp_responses[result_index]
        self._remember_upstream_initialize_instructions(mcp_server, client)

        return cast(CallToolResult, result)

    def _resolve_mcp_server_for_tool_call(
        self,
        server_name: str,
        name: str,
    ) -> MCPServer:
        """Resolve MCP server for call_tool (prefixed name, registry, fallback)."""
        prefixed_tool_name: Final = add_server_prefix_to_name(name, server_name)
        mcp_server = self._get_mcp_server_from_tool_name(prefixed_tool_name)
        resolved_by_server_name_only = False
        normalized_server_name: Final = normalize_server_name(server_name)

        def _candidate_matches_server_name(candidate: MCPServer) -> bool:
            for identifier in (
                candidate.alias,
                candidate.server_name,
                candidate.name,
            ):
                if identifier and normalize_server_name(identifier) == (normalized_server_name):
                    return True
            return False

        if mcp_server is None:
            for candidate in self.get_registry().values():
                if _candidate_matches_server_name(candidate):
                    mcp_server = candidate
                    resolved_by_server_name_only = True
                    break
        if mcp_server is None:
            fallback: Final = self._get_mcp_server_from_tool_name(name)
            if fallback is not None and (not server_name or _candidate_matches_server_name(fallback)):
                mcp_server = fallback
        if mcp_server is None:
            raise ValueError(f"Tool {name} not found")

        if resolved_by_server_name_only and not self._server_exposes_tool(mcp_server, name):
            raise ValueError(f"Tool {name} not found")

        return mcp_server

    async def has_user_oauth_token(self, server: MCPServer, user_api_key_auth: UserAPIKeyAuth | None) -> bool:
        """Whether the v2 resolver can produce a per-user token for this server right now.

        This is the preemptive 401's existence check, routed through the same resolver that drives
        the egress so every authorization_code resolution (egress and the discovery challenge) runs
        through v2. Returns False for a server the resolver does not own (a None spec).
        """
        spec: Final = to_server_spec(server)
        if spec is None:
            return False
        return await self._cred_provider.has_user_token(to_subject(user_api_key_auth, None), spec)

    async def invalidate_user_oauth_token_cache(self, user_id: str, server_id: str) -> None:
        """Drop every cached token for ``(user_id, server_id)`` after the credential row changes
        (re-auth, revoke, config-change purge): the v2 chain's cache and the legacy per-user token
        cache, so the next resolve reads the new row instead of serving the replaced token until its
        cache TTL, whichever path resolves it. This is the single invalidation point for per-user
        OAuth tokens; callers must not evict individual caches directly. Best-effort: a cache-drop
        failure is logged, never raised, because the DB write already succeeded and the TTL remains
        the backstop.
        """
        try:
            await self._per_user_oauth_token_store.invalidate(user_id, server_id)
        except Exception as exc:  # noqa: BLE001 - cache drop is best-effort; TTL is the backstop
            verbose_logger.warning(
                "Failed to invalidate cached MCP OAuth token for user=%s server=%s: %s", user_id, server_id, exc
            )
        try:
            await self._per_user_token_cache.delete(user_id, server_id)
        except Exception as exc:  # noqa: BLE001 - cache drop is best-effort; TTL is the backstop
            verbose_logger.warning(
                "Failed to drop legacy cached MCP OAuth token for user=%s server=%s: %s", user_id, server_id, exc
            )

    async def _resolve_oauth2_headers_for_tool_call(
        self,
        mcp_server: MCPServer,
        oauth2_headers: dict[str, str] | None,
        user_api_key_auth: UserAPIKeyAuth | None,
    ) -> dict[str, str] | None:
        """Look up per-user OAuth headers when the client did not supply a token."""
        if not mcp_server.needs_user_oauth_token or oauth2_headers or user_api_key_auth is None:
            return oauth2_headers

        if to_server_spec(mcp_server) is not None:
            # Migrated to v2: the resolver owns this server's per-user token (inject or fail-closed
            # 401). Building it into extra_headers here would let the v2 graft defer to it and
            # shadow the resolver, double-resolving and hiding the per-server challenge.
            return oauth2_headers

        user_id: Final[str | None] = getattr(user_api_key_auth, "user_id", None)
        if not user_id:
            return oauth2_headers

        try:
            from litellm.proxy._experimental.mcp_server.server import (  # noqa: PLC0415
                _get_user_oauth_extra_headers_from_db,
            )

            stored_headers: Final = await _get_user_oauth_extra_headers_from_db(
                server=mcp_server,
                user_api_key_auth=user_api_key_auth,
            )
            if stored_headers:
                return stored_headers
        except Exception as _lookup_exc:
            verbose_logger.debug(
                "call_tool: per-user token lookup failed for user=%s server=%s: %s",
                user_id,
                mcp_server.server_id,
                _lookup_exc,
            )
        return oauth2_headers

    async def resolve_openapi_upstream_auth(
        self,
        *,
        mcp_server: MCPServer,
        oauth2_headers: dict[str, str] | None,
        raw_headers: dict[str, str] | None,
        mcp_auth_header: str | dict[str, str] | None,
        user_api_key_auth: UserAPIKeyAuth | None,
        forwarded_headers: dict[str, str] | None,
    ) -> tuple[dict[str, str] | None, dict[str, str] | None]:
        """Resolve the gateway-owned upstream credential for a spec_path (OpenAPI) tool call.

        OpenAPI tools egress through a plain httpx call assembled from ContextVars, never through
        ``_create_mcp_client``, so the v2 resolver graft there does not run for them and a resolved
        credential (authorization_code's stored per-user token, client_credentials' minted M2M
        token, token_exchange's exchanged token, passthrough's forwarded caller token) must be
        materialized into headers here. Returns ``(resolved_auth_headers, forwarded_headers)``:
        the resolved headers are authoritative over every other Authorization source (the same
        rule ``_resolve_v2_auth`` applies on the MCPClient path) and ``forwarded_headers`` comes
        back with any header the resolver claimed already dropped. Unmigrated (v1) servers resolve
        through the stored-token lookup instead, and a missing per-user credential raises the same
        discovery challenge the MCPClient path serves, rather than egressing unauthenticated.

        The resolved headers carry only credentials the gateway itself resolved (a stored per-user
        token, a minted or exchanged token). Caller-supplied ``oauth2_headers`` are never promoted
        into them: on the v2 arm they feed only subject-token extraction (the designed RFC 8693
        input), and on the v1 arm their presence disables the stored lookup entirely, so a
        caller's gateway credential can never displace a per-server BYOK header or leak upstream
        as the resolved credential.
        """
        spec: Final = to_server_spec(mcp_server)
        if spec is None:
            if oauth2_headers:
                return None, forwarded_headers
            stored_headers = await self._resolve_oauth2_headers_for_tool_call(mcp_server, None, user_api_key_auth)
            return stored_headers, forwarded_headers

        subject_token: str | None = None
        if isinstance(spec.config, (TokenExchangeConfig, IdJagConfig)):
            subject_token = self._extract_bearer_token(oauth2_headers, raw_headers)
        elif isinstance(spec.config, PassthroughConfig):
            inbound_token, forwarded_headers = _take_forwarded_authorization(forwarded_headers)
            per_server_token: Final = _passthrough_token_from_mcp_auth_header(mcp_auth_header)
            subject_token = per_server_token if per_server_token is not None else inbound_token

        resolved_auth, forwarded_headers = await self._resolve_v2_auth(
            server=mcp_server,
            spec=spec,
            provider=self._cred_provider,
            subject_token=subject_token,
            user_api_key_auth=user_api_key_auth,
            extra_headers=forwarded_headers,
        )
        return await _materialize_auth_headers(resolved_auth), forwarded_headers

    async def _gather_openapi_tool_tasks(
        self,
        tasks: Sequence[Awaitable[object]],
        proxy_logging_obj: ProxyLogging | None,
    ) -> CallToolResult:
        """Await OpenAPI tool tasks and return the tool call result."""
        try:
            mcp_responses: Final = await asyncio.gather(*tasks)
            result_index: Final = 1 if proxy_logging_obj else 0
            return cast(CallToolResult, mcp_responses[result_index])
        except (
            BlockedPiiEntityError,
            GuardrailRaisedException,
            HTTPException,
        ) as e:
            verbose_logger.error("Guardrail blocked MCP tool call during result check: %s", e)
            raise e

    async def call_tool(
        self,
        server_name: str,
        name: str,
        arguments: _ToolArguments,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        mcp_auth_header: str | None = None,
        mcp_server_auth_headers: dict[str, dict[str, str]] | None = None,
        proxy_logging_obj: ProxyLogging | None = None,
        oauth2_headers: dict[str, str] | None = None,
        raw_headers: dict[str, str] | None = None,
        host_progress_callback: Callable | None = None,
        litellm_logging_obj: "LiteLLMLoggingObj | None" = None,
    ) -> CallToolResult:
        """
        Call a tool with the given name and arguments

        Args:
            server_name: Server name
            name: Tool name
            arguments: Tool arguments
            user_api_key_auth: User authentication
            mcp_auth_header: MCP auth header (deprecated)
            mcp_server_auth_headers: Optional dict of server-specific auth headers {server_alias: auth_value}
            proxy_logging_obj: Optional ProxyLogging object for hook integration
            litellm_logging_obj: Optional request logger the guardrail hooks record
                their evaluations onto, so MCP guardrail activity reaches the
                Guardrails Monitor. See ``pre_call_tool_check``


        Returns:
            CallToolResult from the MCP server
        """
        start_time: Final = datetime.datetime.now()
        mcp_server: Final = self._resolve_mcp_server_for_tool_call(server_name, name)

        # Resolved before any hook runs so a missing BYOK credential (401) never
        # leaves during-hook side effects (audit logging, rate-limit bookkeeping)
        # recorded against a call that ultimately fails.
        mcp_auth_header = await _resolve_byok_mcp_auth_header(
            mcp_server,
            user_api_key_auth,
            mcp_auth_header,
        )

        #########################################################
        # Pre MCP Tool Call Hook
        # Allow validation and modification of tool calls before execution
        # Using standard pre_call_hook
        #########################################################
        hook_result: Final[dict[str, Any]] = await self.pre_call_tool_check(
            name=name,
            arguments=arguments,
            server_name=server_name,
            user_api_key_auth=user_api_key_auth,
            proxy_logging_obj=proxy_logging_obj,
            server=mcp_server,
            raw_headers=raw_headers,
            litellm_logging_obj=litellm_logging_obj,
        )
        if "arguments" in hook_result:
            arguments = hook_result["arguments"]

        # Prepare tasks for during hooks
        tasks: Final = []
        if proxy_logging_obj:
            during_hook_task: Final = self._create_during_hook_task(
                name=name,
                arguments=arguments,
                server_name_from_prefix=server_name,
                user_api_key_auth=user_api_key_auth,
                proxy_logging_obj=proxy_logging_obj,
                start_time=start_time,
                litellm_logging_obj=litellm_logging_obj,
            )
            tasks.append(during_hook_task)

        caller_oauth2_headers: Final = oauth2_headers
        oauth2_headers = await self._resolve_oauth2_headers_for_tool_call(mcp_server, oauth2_headers, user_api_key_auth)

        # For OpenAPI servers, call the tool handler directly instead of via MCP client
        if mcp_server.spec_path:
            verbose_logger.debug("Calling OpenAPI tool %s directly via HTTP handler", name)
            if hook_result.get("extra_headers"):
                verbose_logger.warning(
                    "pre_mcp_call hook returned extra_headers for OpenAPI-backed "
                    "MCP server '%s' — header injection is not supported for "
                    "OpenAPI servers; headers will be ignored. Use SSE/HTTP "
                    "transport to enable hook header injection.",
                    server_name,
                )

            auth_header_value, openapi_forwarded_headers, upstream_credential = _resolve_openapi_tool_auth(
                mcp_server=mcp_server,
                mcp_auth_header=mcp_auth_header,
                mcp_server_auth_headers=mcp_server_auth_headers,
                raw_headers=raw_headers,
                user_api_key_auth=user_api_key_auth,
            )
            resolved_auth_headers, forwarded_headers = await self.resolve_openapi_upstream_auth(
                mcp_server=mcp_server,
                oauth2_headers=caller_oauth2_headers,
                raw_headers=raw_headers,
                mcp_auth_header=upstream_credential,
                user_api_key_auth=user_api_key_auth,
                forwarded_headers=openapi_forwarded_headers,
            )

            async def _call_openapi_via_handler():
                from litellm.proxy._experimental.mcp_server.openapi_to_mcp_generator import (
                    _request_auth_header,
                    _request_extra_headers,
                    _request_resolved_auth_headers,
                )

                auth_token: Final = _request_auth_header.set(auth_header_value)
                extra_token: Final = _request_extra_headers.set(forwarded_headers)
                resolved_token: Final = _request_resolved_auth_headers.set(resolved_auth_headers)
                try:
                    async with self._limit_outbound_concurrency(mcp_server):
                        return await self._call_openapi_tool_handler(mcp_server, name, arguments)
                finally:
                    _request_auth_header.reset(auth_token)
                    _request_extra_headers.reset(extra_token)
                    _request_resolved_auth_headers.reset(resolved_token)

            tasks.append(asyncio.create_task(_call_openapi_via_handler()))
        else:
            return await self._call_regular_mcp_tool(
                mcp_server=mcp_server,
                original_tool_name=name,
                arguments=arguments,
                tasks=tasks,
                mcp_auth_header=mcp_auth_header,
                mcp_server_auth_headers=mcp_server_auth_headers,
                oauth2_headers=oauth2_headers,
                raw_headers=raw_headers,
                proxy_logging_obj=proxy_logging_obj,
                host_progress_callback=host_progress_callback,
                hook_extra_headers=hook_result.get("extra_headers"),
                user_api_key_auth=user_api_key_auth,
            )

        return await self._gather_openapi_tool_tasks(tasks, proxy_logging_obj)

    #########################################################
    # End of Methods that call the upstream MCP servers
    #########################################################

    def initialize_tool_name_to_mcp_server_name_mapping(self):
        """
        On startup, initialize the tool name to MCP server name mapping
        """
        try:
            if asyncio.get_running_loop():
                asyncio.create_task(self._initialize_tool_name_to_mcp_server_name_mapping())
        except RuntimeError as e:  # no running event loop
            verbose_logger.exception(
                "No running event loop - skipping tool name to MCP server name mapping initialization: %s", e
            )

    async def _initialize_tool_name_to_mcp_server_name_mapping(self):
        """
        Call list_tools for each server and update the tool name to MCP server name mapping
        Note: This now handles prefixed tool names
        """
        for server in self.get_registry().values():
            if self._oauth_discovery_slot(server.server_id) is not None:
                continue
            if server.needs_user_oauth_token:
                # Skip OAuth2 servers that rely on user-provided tokens
                continue
            try:
                tools = await self._get_tools_from_server(server)
            except MCPUpstreamAuthError as e:
                # Pass-through servers expect a user-supplied bearer token;
                # at startup we have none, so an upstream 401 is normal.
                # Swallow it so we keep mapping the remaining servers.
                verbose_logger.debug(
                    "Skipping tool name mapping for server %s due to upstream auth error: %s", server.name, e
                )
                continue
            except Exception as e:
                verbose_logger.warning(
                    "Failed to get tools from server %s during tool name mapping initialization: %s", server.name, e
                )
                continue
            for tool in tools:
                # The tool.name here is already prefixed from _get_tools_from_server
                # Extract original name for mapping
                original_name = strip_known_server_prefix(tool.name, server)
                self.tool_name_to_mcp_server_name_mapping[original_name] = server.name
                self.tool_name_to_mcp_server_name_mapping[tool.name] = server.name

    def _get_mcp_server_from_tool_name(self, tool_name: str) -> MCPServer | None:
        """
        Get the MCP Server from the tool name (handles both prefixed and non-prefixed names)

        Args:
            tool_name: Tool name (can be prefixed or non-prefixed)

        Returns:
            MCPServer if found, None otherwise
        """
        registry_servers: Final = list(self.get_registry().values())

        # Build prefix → server lookup covering every known form a tool name
        # may take (alias / server_name / server_id / short ID).  This is what
        # makes the short-prefix mode work without breaking historical names.
        prefix_to_server: Final[dict[str, MCPServer]] = {}
        for server in registry_servers:
            for known_prefix in iter_known_server_prefixes(server):
                normalised = normalize_server_name(known_prefix)
                prefix_to_server.setdefault(normalised, server)

        # First try with the original tool name
        if tool_name in self.tool_name_to_mcp_server_name_mapping:
            server_name: Final = self.tool_name_to_mcp_server_name_mapping[tool_name]
            normalised_lookup: Final = normalize_server_name(server_name)
            if normalised_lookup in prefix_to_server:
                return prefix_to_server[normalised_lookup]
            for server in registry_servers:
                if normalize_server_name(server.name) == normalised_lookup:
                    return server

        # If not found and tool name is prefixed, extract the prefix and
        # match against any known form.
        matched: Final = match_known_server_prefix(tool_name, prefix_to_server.keys())
        if matched is not None:
            matched_prefix, original_tool_name = matched
            matched_server: Final = prefix_to_server.get(matched_prefix)
            if matched_server is not None and self._server_exposes_tool(matched_server, original_tool_name):
                return matched_server

        return None

    async def reload_servers_from_database(self):
        """Re-synchronize the in-memory MCP server registry with the database."""
        from litellm.proxy.management_endpoints.mcp_management_endpoints import (
            get_prisma_client_or_throw,
        )

        verbose_logger.debug("Loading MCP servers from database into registry...")
        self._upstream_initialize_instructions_by_server_id.clear()
        self._upstream_initialize_instructions_probed_at.clear()

        # perform authz check to filter the mcp servers user has access to
        prisma_client: Final = get_prisma_client_or_throw("Database not connected. Connect a database to your proxy")
        # Load only "active", legacy "approved", and NULL (no approval workflow) rows.
        # Pending/rejected servers are excluded at the DB level so we never load them.
        from litellm.proxy._experimental.mcp_server.db import LiteLLM_MCPServerTable

        raw_rows: Final[Sequence[BaseModel]] = await MCPServerRepository(prisma_client).table.find_many(
            where={
                "OR": [
                    {"approval_status": None},
                    {"approval_status": {"in": ["active", "approved"]}},
                ]
            }
        )
        db_mcp_servers: Final = [LiteLLM_MCPServerTable.model_validate(r.model_dump()) for r in raw_rows]
        verbose_logger.info("Found %s MCP servers in database", len(db_mcp_servers))

        previous_registry: Final = self.registry
        new_registry: Final[dict[str, MCPServer]] = {}

        # Stage one: build every server.  Stage two assigns short prefixes
        # against the *full* set so dedup is deterministic regardless of
        # iteration order.
        for server in db_mcp_servers:
            try:
                existing_server = previous_registry.get(server.server_id)

                if (
                    existing_server is not None
                    and existing_server.updated_at is not None
                    and server.updated_at is not None
                    and existing_server.updated_at == server.updated_at
                    and (
                        self._oauth_discovery_slot(server.server_id) is not None
                        or not _oauth_endpoints_unresolved(existing_server)
                    )
                ):
                    # Re-use existing server instance to avoid re-running build_mcp_server_from_table()
                    # which can perform network discovery for OAuth2 servers.
                    new_registry[server.server_id] = existing_server
                    continue

                _warn_on_server_name_fields(
                    server_id=server.server_id,
                    alias=getattr(server, "alias", None),
                    server_name=getattr(server, "server_name", None),
                )
                verbose_logger.debug("Building server from DB: %s (%s)", server.server_id, server.server_name)
                # raw_rows come straight from the DB, so their global env var
                # values (like credentials) are still encrypted here, unlike the
                # already-decrypted records add_server/update_server are handed.
                # Decrypt them while building the registry entry.
                new_server = await self.build_mcp_server_from_table(server, env_vars_are_encrypted=True)
                # Carry the cached short_prefix from the previous registry entry
                # (if any) so the prefix is stable across reloads.
                if existing_server is not None and existing_server.short_prefix:
                    new_server.short_prefix = existing_server.short_prefix
                _carry_forward_resolved_oauth_endpoints(new_server=new_server, previous_server=existing_server)
                new_registry[server.server_id] = new_server
            except Exception as e:
                verbose_logger.exception(
                    "Skipping MCP server %s (%s) during DB reload: %s",
                    server.server_id,
                    getattr(server, "alias", None),
                    e,
                )

        # Assign short prefixes against the full candidate set without
        # publishing the staged registry to concurrent callers.
        registered_registry: Final[dict[str, MCPServer]] = {}
        registered_openapi_tools = False
        for server_id, new_server in new_registry.items():
            try:
                self._assign_unique_short_prefix(new_server, registry=new_registry)
                # Register OpenAPI tools *after* the final short prefix is assigned
                # so the tools are stored in the global registry under the same
                # prefix that lookups will use.
                await self._maybe_register_openapi_tools(new_server, initialize_mapping=False)
                registered_registry[server_id] = new_server
                if new_server.spec_path:
                    registered_openapi_tools = True
            except Exception as e:
                verbose_logger.exception(
                    "Skipping MCP server %s (%s) during DB reload: %s",
                    new_server.server_id,
                    getattr(new_server, "alias", None),
                    e,
                )

        dropped_registry_keys: Final = previous_registry.keys() - registered_registry.keys()
        for registry_key in dropped_registry_keys:
            self._invalidate_oauth_discovery_state(previous_registry[registry_key].server_id)

        self.registry = registered_registry
        # A discovery task may have published into ``previous_registry`` while
        # this replacement was being staged. Reconcile every published entry
        # synchronously after the swap so a lost publication cannot also leave
        # the replacement unresolved with no retry slot.
        registered_servers: Final = tuple(registered_registry.values())
        self._reconcile_oauth_discovery_slots_for_servers(registered_servers)
        self._prime_oauth_metadata_discovery_for_servers(registered_servers)
        if registered_openapi_tools:
            self.initialize_tool_name_to_mcp_server_name_mapping()

        verbose_logger.debug("MCP registry refreshed (%s servers in registry)", len(registered_registry))

        await self._hydrate_config_servers_dcr_clients()

    def get_mcp_servers_from_ids(self, server_ids: list[str]) -> list[MCPServer]:
        servers: Final = []
        registry: Final = self.get_registry()
        for server in registry.values():
            if server.server_id in server_ids:
                servers.append(server)
        return servers

    def _get_general_settings(self) -> dict[str, Any]:
        """Get general_settings, importing lazily to avoid circular imports."""
        try:
            from litellm.proxy.proxy_server import (
                general_settings as proxy_general_settings,
            )

            return proxy_general_settings
        except ImportError:
            # Fallback if proxy_server not available
            return {}

    def _is_server_accessible_from_ip(self, server: MCPServer, client_ip: str | None) -> bool:
        """
        Check if a server is accessible from the given client IP.

        - If client_ip is None, no IP filtering is applied (internal callers).
        - If the server has available_on_public_internet=True, it's always accessible.
        - Otherwise, only internal/private IPs can access it.
        """
        if client_ip is None:
            return True
        if server.available_on_public_internet:
            return True
        # Check backwards compat: litellm.public_mcp_servers
        public_ids: Final = set(litellm.public_mcp_servers or [])
        if server.server_id in public_ids:
            return True
        # Non-public server: only accessible from internal IPs
        general_settings: Final = self._get_general_settings()
        internal_networks = IPAddressUtils.parse_internal_networks(general_settings.get("mcp_internal_ip_ranges"))
        return IPAddressUtils.is_internal_ip(client_ip, internal_networks)

    def get_mcp_server_by_id(self, server_id: str) -> MCPServer | None:
        """
        Get the MCP Server from the server id
        """
        registry: Final = self.get_registry()
        for server in registry.values():
            if server.server_id == server_id:
                return server
        return None

    def get_public_mcp_servers(self) -> list[MCPServer]:
        """
        Return the MCP servers published to the AI Hub via /v1/mcp/make_public.

        Default (litellm.public_mcp_hub_strict_whitelist=True): mirrors
        /public/model_hub and /public/agent_hub — gates strictly on the
        litellm.public_mcp_servers whitelist. Returns an empty list when no
        servers have been published. The per-server available_on_public_internet
        flag is unrelated — it governs IP-based access in
        _is_server_accessible_from_ip, not hub visibility.

        Legacy (litellm.public_mcp_hub_strict_whitelist=False): preserves the
        pre-fix behavior where any server with available_on_public_internet=True
        is also included. Intended as a one-release migration window for
        deployments that relied on the OR-with-default semantics; will be
        removed in a future release.
        """
        if litellm.public_mcp_hub_strict_whitelist:
            if litellm.public_mcp_servers is None:
                return []
            public_ids = set(litellm.public_mcp_servers)
            return [server for server in self.get_registry().values() if server.server_id in public_ids]

        public_ids = set(litellm.public_mcp_servers or [])
        return [
            server
            for server in self.get_registry().values()
            if server.available_on_public_internet or server.server_id in public_ids
        ]

    def expand_permission_list(self, identifiers: list[str]) -> list[str]:
        """
        Expand a permission list of server_ids/names/aliases into concrete
        server_ids against the current region's config + DB registry union.

        Entries that match a server_id pass through unchanged. Entries that
        match an alias/server_name/name are replaced with every matching
        server_id (duplicate names grant access to all matches). Entries
        that resolve to nothing pass through as-is and a debug log is
        emitted so admins can diagnose stale/typo permission entries — the
        downstream access-check denies them when compared against the
        concrete request server_id.
        """
        if not identifiers:
            return []
        registry: Final = self.get_registry()
        expanded: Final[set[str]] = set()
        for identifier in identifiers:
            if identifier in registry:
                expanded.add(identifier)
                continue
            matches: list[str] = [
                server_id
                for server_id, server in registry.items()
                if server.alias == identifier or server.server_name == identifier or server.name == identifier
            ]
            if matches:
                expanded.update(matches)
            else:
                # %r quotes and escapes control chars so an admin-controlled
                # identifier with newlines cannot forge log lines.
                verbose_logger.debug(
                    "MCP permission entry %r does not resolve to any known "
                    "server (config + DB union). Passing through — the "
                    "downstream access check will deny it if it's stale.",
                    identifier,
                )
                expanded.add(identifier)
        return list(expanded)

    def expand_tool_permissions(
        self,
        tool_permissions: dict[str, list[str]] | None,
    ) -> dict[str, list[str]]:
        """
        Rewrite an ``mcp_tool_permissions`` dict keyed by id/name/alias so
        every key is a concrete server_id where possible. Tool lists from
        keys that point at the same server are unioned, matching the
        "duplicate names grant access to all matches" semantics of
        ``expand_permission_list``.

        Required so name-based keys don't silently drop their tool
        restrictions when the lookup uses the resolved server_id. Unresolved
        keys pass through via ``expand_permission_list`` so stale id-keyed
        restrictions still apply when the same string is used for lookup.
        """
        if not tool_permissions:
            return {}
        result: Final[dict[str, list[str]]] = {}
        for key, tools in tool_permissions.items():
            for server_id in self.expand_permission_list([key]):
                result.setdefault(server_id, []).extend(tools or [])
        return result

    def get_mcp_server_by_name(self, server_name: str, client_ip: str | None = None) -> MCPServer | None:
        """
        Get the MCP Server from the server name.

        Uses priority-based matching to avoid collisions:
        1. First pass: exact alias match (highest priority)
        2. Second pass: exact server_name match
        3. Third pass: exact name match (lowest priority)

        Args:
            server_name: The server name to look up.
            client_ip: Optional client IP for access control. When provided,
                       non-public servers are hidden from external IPs.
        """
        registry: Final = self.get_registry()
        # Pass 1: Match by alias (highest priority)
        for server in registry.values():
            if server.alias == server_name:
                if not self._is_server_accessible_from_ip(server, client_ip):
                    return None
                return server
        # Pass 2: Match by server_name
        for server in registry.values():
            if server.server_name == server_name:
                if not self._is_server_accessible_from_ip(server, client_ip):
                    return None
                return server
        # Pass 3: Match by name (lowest priority)
        for server in registry.values():
            if server.name == server_name:
                if not self._is_server_accessible_from_ip(server, client_ip):
                    return None
                return server
        return None

    def get_filtered_registry(self, client_ip: str | None = None) -> dict[str, MCPServer]:
        """
        Get registry filtered by client IP access control.

        Args:
            client_ip: Optional client IP. When provided, non-public servers
                       are hidden from external IPs. When None, returns all servers.
        """
        registry: Final = self.get_registry()
        if client_ip is None:
            return registry
        return {k: v for k, v in registry.items() if self._is_server_accessible_from_ip(v, client_ip)}

    def _generate_stable_server_id(
        self,
        server_name: str,
        url: str,
        transport: str,
        auth_type: str | None = None,
        alias: str | None = None,
    ) -> str:
        """
        Generate a stable server ID based on server parameters using a hash function.

        This is critical to ensure the server_id is stable across server restarts.
        Some users store MCPs on the config.yaml and permission management is based on server_ids.

        Eg a key might have mcp_servers = ["1234"], if the server_id changes across restarts, the key will no longer have access to the MCP.

        Args:
            server_name: Name of the server
            url: Server URL
            transport: Transport type (sse, http, etc.)
            auth_type: Authentication type (optional)
            alias: Server alias (optional)

        Returns:
            A deterministic server ID string
        """
        # Create a string from all the identifying parameters
        params_string: Final = f"{server_name}|{url}|{transport}|{auth_type or ''}|{alias or ''}"

        # Generate SHA-256 hash
        hash_object: Final = hashlib.sha256(params_string.encode("utf-8"))
        hash_hex: Final = hash_object.hexdigest()

        # Take first 32 characters and format as UUID-like string
        return hash_hex[:32]

    async def health_check_server(self, server_id: str, mcp_auth_header: str | None = None) -> LiteLLM_MCPServerTable:
        """
        Perform a health check on a specific MCP server.

        Args:
            server_id: The ID of the server to health check
            mcp_auth_header: Optional authentication header for the MCP server

        Returns:
            Dict containing health check results
        """
        from datetime import datetime

        server: Final = self.get_mcp_server_by_id(server_id)
        if not server:
            verbose_logger.warning("MCP Server %s not found", server_id)
            return LiteLLM_MCPServerTable(
                server_id=server_id,
                server_name=None,
                transport=MCPTransport.http,  # Default transport for not found servers
                status="unknown",
                health_check_error="Server not found",
                last_health_check=datetime.now(),
            )

        status: Literal["healthy", "unhealthy", "unknown"] = "unknown"
        health_check_error = None

        # Check if we should skip health check based on auth configuration
        should_skip_health_check = False

        # Skip if server requires per-user authentication (OAuth2 or passthrough auth)
        if (
            server.requires_per_user_auth
            or (
                server.auth_type
                and server.auth_type != MCPAuth.none
                and server.auth_type != MCPAuth.aws_sigv4
                and not server.authentication_token
            )
            or self._references_per_user_env_var(server)
        ):
            should_skip_health_check = True

        if not should_skip_health_check:
            try:
                resolved_static_headers: Final = await self._resolve_static_headers_with_env_vars(
                    server=server,
                    user_api_key_auth=None,
                    raise_on_missing=False,
                )
                extra_headers: Final = dict(resolved_static_headers) if resolved_static_headers else {}
                client: Final = await self._create_mcp_client(
                    server=server,
                    mcp_auth_header=None,
                    extra_headers=extra_headers,
                    stdio_env=None,
                )

                async def _noop(session):
                    return "ok"

                # Add timeout wrapper to prevent hanging
                await asyncio.wait_for(client.run_with_session(_noop), timeout=MCP_HEALTH_CHECK_TIMEOUT)
                self._remember_upstream_initialize_instructions(server, client)
                status = "healthy"
            except asyncio.TimeoutError:
                health_check_error = f"Health check timed out after {MCP_HEALTH_CHECK_TIMEOUT} seconds"
                status = "unhealthy"
            except asyncio.CancelledError:
                health_check_error = "Health check was cancelled"
                status = "unknown"
            except Exception as e:
                health_check_error = str(e)
                status = "unhealthy"

        return LiteLLM_MCPServerTable(
            server_id=server.server_id,
            server_name=server.server_name,
            alias=server.alias,
            description=(server.mcp_info.get("description") if server.mcp_info else None),
            url=server.url,
            transport=server.transport,
            auth_type=server.auth_type,
            created_at=server.created_at,
            updated_at=server.updated_at,
            teams=[],
            mcp_access_groups=server.access_groups or [],
            allowed_tools=server.allowed_tools or [],
            extra_headers=server.extra_headers or [],
            mcp_info=server.mcp_info,
            static_headers=server.static_headers,
            env_vars=self._env_vars_to_models(server.env_vars),
            status=status,
            last_health_check=datetime.now(),
            health_check_error=health_check_error,
            command=getattr(server, "command", None),
            args=getattr(server, "args", None) or [],
            env=getattr(server, "env", None) or {},
            issuer=server.issuer,
            authorization_url=server.configured_authorization_url or server.authorization_url,
            token_url=server.configured_token_url or server.token_url,
            registration_url=server.configured_registration_url or server.registration_url,
            oauth2_flow=server.oauth2_flow,
            dcr_bridge=server.dcr_bridge,
            token_exchange_endpoint=server.token_exchange_endpoint,
            audience=server.audience,
            subject_token_type=server.subject_token_type,
            token_exchange_profile=server.token_exchange_profile,
            allow_all_keys=server.allow_all_keys,
            instructions=server.instructions,
            timeout=server.timeout,
            max_concurrent_requests=server.max_concurrent_requests,
        )

    async def get_all_mcp_servers_with_health_and_teams(
        self,
        user_api_key_auth: UserAPIKeyAuth | None = None,
        server_ids: list[str] | None = None,
    ) -> list[LiteLLM_MCPServerTable]:
        """
        Get all MCP servers that the user has access to, with health status and team information.

        Args:
            user_api_key_auth: User authentication info for access control
            server_ids: Optional list of server IDs to filter. If provided, only these servers
                       will be checked (subject to access control). If None, all accessible servers are checked.

        Returns:
            List of MCP server objects with health and team data
        """

        # Get allowed server IDs
        allowed_server_ids: Final = await self.get_allowed_mcp_servers(user_api_key_auth)

        # Filter by requested server_ids if provided
        if server_ids:
            # Only check servers that are both requested AND accessible
            target_server_ids = [sid for sid in server_ids if sid in allowed_server_ids]
        else:
            # Check all accessible servers
            target_server_ids = allowed_server_ids

        return await self._run_health_checks(target_server_ids)

    async def get_all_allowed_mcp_servers(
        self,
        user_api_key_auth: UserAPIKeyAuth | None = None,
    ) -> list[LiteLLM_MCPServerTable]:
        """
        Get all MCP servers that the user has access to.

        Args:
            user_api_key_auth: User authentication info for access control

        Returns:
            List of MCP server objects without health status
        """
        # Get allowed server IDs
        allowed_server_ids: Final = await self.get_allowed_mcp_servers(user_api_key_auth)

        list_mcp_servers: Final[list[LiteLLM_MCPServerTable]] = []

        for server_id in allowed_server_ids:
            server = self.get_mcp_server_by_id(server_id)
            if not server:
                verbose_logger.warning("MCP Server %s not found in registry", server_id)
                continue

            mcp_server_table = self._build_mcp_server_table(server)
            list_mcp_servers.append(mcp_server_table)

        return list_mcp_servers

    @staticmethod
    def _env_vars_to_models(
        env_vars: _EnvVarList | None,
    ) -> list[MCPEnvVar] | None:
        if env_vars is None:
            return None
        return [MCPEnvVar.model_validate(env_var) for env_var in env_vars]

    def _build_mcp_server_table(self, server: MCPServer) -> LiteLLM_MCPServerTable:
        return LiteLLM_MCPServerTable(
            server_id=server.server_id,
            server_name=server.server_name,
            alias=server.alias,
            description=(server.mcp_info.get("description") if server.mcp_info else None),
            url=server.url,
            spec_path=server.spec_path,
            transport=server.transport,
            auth_type=server.auth_type,
            created_at=server.created_at,
            updated_at=server.updated_at,
            teams=[],
            mcp_access_groups=server.access_groups or [],
            allowed_tools=server.allowed_tools or [],
            tool_name_to_display_name=server.tool_name_to_display_name,
            tool_name_to_description=server.tool_name_to_description,
            extra_headers=server.extra_headers or [],
            mcp_info=server.mcp_info,
            static_headers=server.static_headers,
            env_vars=self._env_vars_to_models(server.env_vars),
            status=None,  # No health check performed
            last_health_check=None,  # No health check performed
            health_check_error=None,
            command=getattr(server, "command", None),
            args=getattr(server, "args", None) or [],
            env=getattr(server, "env", None) or {},
            issuer=server.issuer,
            authorization_url=server.configured_authorization_url or server.authorization_url,
            token_url=server.configured_token_url or server.token_url,
            registration_url=server.configured_registration_url or server.registration_url,
            oauth2_flow=server.oauth2_flow,
            token_exchange_endpoint=server.token_exchange_endpoint,
            audience=server.audience,
            subject_token_type=server.subject_token_type,
            token_exchange_profile=server.token_exchange_profile,
            allow_all_keys=server.allow_all_keys,
            available_on_public_internet=server.available_on_public_internet,
            delegate_auth_to_upstream=server.delegate_auth_to_upstream,
            oauth_passthrough=getattr(server, "oauth_passthrough", False),
            dcr_bridge=server.dcr_bridge,
            is_byok=server.is_byok,
            byok_description=server.byok_description,
            byok_api_key_help_url=server.byok_api_key_help_url,
            source_url=server.source_url,
            instructions=server.instructions,
            timeout=server.timeout,
            max_concurrent_requests=server.max_concurrent_requests,
        )

    async def get_all_mcp_servers_unfiltered(self) -> list[LiteLLM_MCPServerTable]:
        """Return all MCP servers from registry without applying access controls."""

        registry: Final = self.get_registry()
        if not registry:
            return []

        servers: Final[list[LiteLLM_MCPServerTable]] = []
        for server in registry.values():
            servers.append(self._build_mcp_server_table(server))
        return servers

    async def get_all_mcp_servers_with_health_unfiltered(
        self, server_ids: list[str] | None = None
    ) -> list[LiteLLM_MCPServerTable]:
        """Return health info for all servers in registry regardless of user access."""

        registry: Final = self.get_registry()
        if not registry:
            return []

        if server_ids:
            target_server_ids = [sid for sid in server_ids if sid in registry]
        else:
            target_server_ids = list(registry.keys())

        if not target_server_ids:
            return []

        return await self._run_health_checks(target_server_ids)

    async def _run_health_checks(self, target_server_ids: list[str]) -> list[LiteLLM_MCPServerTable]:
        if not target_server_ids:
            return []

        tasks: Final = [self.health_check_server(server_id) for server_id in target_server_ids]
        results: Final = await asyncio.gather(*tasks)
        return [server for server in results if server is not None]


global_mcp_server_manager: Final[MCPServerManager] = MCPServerManager()
