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hermes-agent/tools/mcp_tool.py

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#!/usr/bin/env python3
"""
MCP (Model Context Protocol) client: connects to configured MCP servers over
stdio, Streamable HTTP or SSE, discovers their tools and registers them into
the hermes tool registry. The ``mcp`` package is optional; without it this
module is a no-op.
Config lives under ``mcp_servers`` in ~/.hermes/config.yaml::
mcp_servers:
filesystem:
command: "npx"
args: ["-y", "@modelcontextprotocol/server-filesystem", "/tmp"]
env: {}
timeout: 120 # per tool call (default 300)
connect_timeout: 60 # initial connect (default 60)
keepalive_interval: 10 # liveness ping; keep below the server's
# session TTL (default 180, floor 5)
idle_timeout_seconds: 3600 # optional stdio recycle (0 = off); may
max_lifetime_seconds: 86400 # also live under lifecycle: {...}
supports_parallel_tool_calls: true
remote_api:
url: "https://my-mcp-server.example.com/mcp"
headers: {Authorization: "Bearer sk-..."}
identity_header: {name: "X-User-Id", value_from: "static", value: "alice"}
skip_preflight: true # endpoint answers HEAD/GET with a non-MCP
# content type but serves MCP over POST
searxng:
url: "http://localhost:8000/sse"
transport: sse
sampling: {enabled: true, model: "gemini-3-flash", max_tokens_cap: 4096,
timeout: 30, max_rpm: 10, allowed_models: [], max_tool_rounds: 5}
Architecture: one background event loop (``_mcp_loop``) in a daemon thread;
each server is a long-lived Task on it (``MCPServerTask``) so the transport's
anyio cancel scopes are entered and exited in the same Task. Tool calls are
scheduled onto the loop via ``run_coroutine_threadsafe``. ``_servers`` and the
loop handles are shared with caller threads; every mutation holds ``_lock``.
Module map (all names re-exported here): ``mcp_tool_common`` (pure helpers),
``mcp_tool_schema`` (schema conversion / naming), ``mcp_tool_content`` (result
block rendering), ``mcp_tool_errors`` (failure classification, URL/cert/header
resolution), ``mcp_tool_config`` (config loading, stdio env), ``mcp_tool_sampling``
(sampling + elicitation handlers), ``mcp_tool_handlers`` (registry handlers and
per-call recovery), ``mcp_tool_registration`` (registry writes), ``mcp_tool_server_run``
/ ``mcp_tool_transport`` / ``mcp_tool_health`` (MCPServerTask mixins: run state
machine, transport bring-up, keepalive/liveness), ``mcp_tool_loop`` (discovery
lock, loop thread, cross-thread scheduling and reconnect signalling),
``mcp_tool_discovery`` (connect, lazy start, ``discover_mcp_tools`` and the status
API), ``mcp_tool_lifecycle`` (shutdown, orphan reaping), ``mcp_tool_agent``
(live-agent tool list refresh). This module keeps the SDK loader, the
``MCPServerTask`` shell and every piece of shared module state (siblings read
it back through ``tools.mcp_tool`` at call time, never by value).
"""
import asyncio
import contextvars
import importlib
import importlib.util
import inspect
import logging
import os # noqa: F401 — tests patch ``tools.mcp_tool.os.*``
import shutil # noqa: F401 — tests patch ``tools.mcp_tool.shutil.which``
import threading
import time
from typing import Any, Callable, Dict, List, Optional, Set
logger = logging.getLogger(__name__)
# Split modules. Every name is re-exported here so ``from tools.mcp_tool import X``
# and ``mock.patch("tools.mcp_tool.X")`` keep working; the siblings read origin
# state back through ``tools.mcp_tool`` at call time (never by value).
from tools.mcp_tool_common import ( # noqa: F401
_DEFAULT_TOOL_TIMEOUT, _env_ref_name, _exc_str, _get_lifecycle_seconds,
_jittered, _parse_boolish, _resolve_tool_timeout, _safe_numeric,
_sanitize_error, mcp_field,
)
from tools.mcp_tool_schema import ( # noqa: F401
MCP_TOOL_NAME_PREFIX, _build_utility_schemas, _convert_mcp_schema,
_normalize_mcp_input_schema, _scan_mcp_description, matches_name_filter,
mcp_prefixed_tool_name, sanitize_mcp_name_component,
)
from tools.mcp_tool_content import ( # noqa: F401
_MCP_HARD_RESULT_CAP_CHARS, _MCP_RESOURCE_MAX_B64_CHARS,
_MCP_RESOURCE_MAX_BYTES, _cache_mcp_audio_block, _cache_mcp_image_block,
_is_reserved_mcp_meta_key, _mcp_image_extension_for_mime_type,
_mcp_resource_filename, _render_mcp_resource_block, _truncate_mcp_text_result,
)
from tools.mcp_tool_errors import ( # noqa: F401
InvalidMcpUrlError, NonMcpEndpointError, _EXC_TRAVERSAL_MAX_NODES,
_JSONRPC_UNSUPPORTED_PROTOCOL_VERSION, _classify_mcp_failure,
_format_connect_error, _handshake_rejected_as_modern, _is_auth_error,
_is_method_not_found_error, _is_session_expired_error,
_make_redirect_header_stripper, _resolve_client_cert, _resolve_identity_header,
_unwrap_exception_group, _validate_remote_mcp_url,
)
from tools.mcp_tool_config import ( # noqa: F401
_ENV_VAR_PATTERN, _build_safe_env, _filter_suspicious_mcp_servers,
_get_mcp_stderr_log, _interpolate_env_vars, _load_mcp_config,
_resolve_stdio_command, _warn_hidden_whitespace, _whitespace_warned,
_workspace_folder, _wrap_command_with_watchdog, _write_stderr_log_header,
)
from tools.mcp_tool_sampling import ( # noqa: F401
ElicitationHandler, SamplingHandler, _format_elicitation_schema_summary,
)
from tools.mcp_tool_handlers import ( # noqa: F401
_handle_auth_error_and_retry, _handle_session_expired_and_retry, _make_check_fn,
_make_get_prompt_handler, _make_list_prompts_handler,
_make_list_resources_handler, _make_read_resource_handler, _make_tool_handler,
)
from tools.mcp_tool_registration import ( # noqa: F401
_annotation_read_only_hint, _existing_tool_names, _forget_mcp_tool_server,
_normalize_server_trust, _register_from_cache_sync, _register_server_tools,
_select_utility_schemas, _track_mcp_tool_server,
)
from tools.mcp_tool_lifecycle import ( # noqa: F401
_drain_and_stop_mcp_loop, _drain_mcp_loop_tasks, _filter_mcp_children,
_kill_orphaned_mcp_children, _orphan_stdio_pid_servers, _orphan_stdio_pids,
_snapshot_child_pids, _stdio_pgids, _stdio_pids, _stop_mcp_loop_if_idle,
shutdown_mcp_servers,
)
from tools.mcp_tool_agent import ( # noqa: F401
_reinject_post_build_tools, persist_agent_tool_names, refresh_agent_mcp_tools,
reprobe_tool_availability, restore_agent_tool_prefix,
)
from tools.mcp_tool_transport import MCPServerTransportMixin
from tools.mcp_tool_server_run import MCPServerRunMixin
from tools.mcp_tool_health import MCPServerHealthMixin
from tools.mcp_tool_loop import ( # noqa: F401 -- re-exported for callers and test patches
_running_loop,
_LockCookie, _acquire_lock_on_fh, _try_acquire_mcp_discovery_lock,
_mcp_loop_exception_handler, _wrap_with_home_override,
_wrap_with_dashboard_oauth_flow, _run_on_mcp_loop, _signal_reconnect,
reconnect_mcp_server, _wait_for_server_session_ready,
_signal_reconnect_and_wait, _ensure_mcp_loop, _stop_mcp_loop,
)
from tools.mcp_tool_discovery import ( # noqa: F401 -- re-exported for callers and test patches
_record_connect_failure, _clear_connect_failure, _connect_cooldown_active,
_connect_server, _request_lazy_reconnect, _resolve_server_lazy,
_ensure_lazy_server_connected, _get_connected_server_for_call,
_discover_and_register_server, register_mcp_servers, discover_mcp_tools,
is_mcp_tool_parallel_safe, get_mcp_status, probe_mcp_server_tools,
has_registered_mcp_tools, get_registered_mcp_server_names,
)
# Wall-clock bound on the (fail-open) OSV malware preflight run off the loop
# before a stdio spawn. Kept just ABOVE osv_check._TIMEOUT (10s) so the inner
# socket timeout normally fires first; this only bites when a stalled SSL
# handshake defeats it (which used to freeze the event loop at startup).
_OSV_MALWARE_CHECK_TIMEOUT_S = 12.0
# ---------------------------------------------------------------------------
# Optional MCP SDK: availability probe now, symbol import on first use
# ---------------------------------------------------------------------------
_MCP_AVAILABLE = False
_MCP_HTTP_AVAILABLE = False
_MCP_NEW_HTTP = False
_MCP_LEGACY_HTTP = False
_MCP_SAMPLING_TYPES = False
_MCP_NOTIFICATION_TYPES = False
_MCP_ELICITATION_TYPES = False
_MCP_MESSAGE_HANDLER_SUPPORTED = False
_MCP_LOGGING_CALLBACK_SUPPORTED = False
sse_client = None
# Fallback for SDKs that don't export LATEST_PROTOCOL_VERSION (Streamable HTTP
# arrived with 2025-03-26, so this stays valid for the HTTP path).
LATEST_PROTOCOL_VERSION = "2025-03-26"
# Newest revision `ClientSession.initialize()` actually speaks. From 2026-07-28
# the handshake is replaced by a per-request envelope, so this can be OLDER
# than LATEST_PROTOCOL_VERSION; the MCP-Protocol-Version header must be seeded
# from this one or it advertises a revision the body does not speak.
LATEST_HANDSHAKE_VERSION = LATEST_PROTOCOL_VERSION
# Importing `mcp` costs ~260ms, so it is deferred to first real use
# (_ensure_mcp_sdk). Availability is decided here with a metadata-only
# find_spec probe so every `if not _MCP_AVAILABLE` gate / test patch / skipif
# keeps its exact semantics.
try:
_MCP_AVAILABLE = importlib.util.find_spec("mcp") is not None
except Exception:
_MCP_AVAILABLE = False
if not _MCP_AVAILABLE:
logger.debug("mcp package not installed -- MCP tool support disabled")
ClientSession: Any = None
_MCP_SDK_IMPORT_ATTEMPTED = False
_MCP_SDK_IMPORT_LOCK = threading.Lock()
# SDK symbols bound by _ensure_mcp_sdk(). Module __getattr__ (PEP 562) imports
# the SDK on first external access, so mock.patch("tools.mcp_tool.stdio_client")
# sees a real original and the mock is never clobbered (_ensure is idempotent).
_MCP_SDK_LAZY_SYMBOLS = frozenset({
"StdioServerParameters", "stdio_client",
"streamablehttp_client", "streamable_http_client",
"CreateMessageResult", "CreateMessageResultWithTools", "ErrorData",
"SamplingCapability", "SamplingToolsCapability", "TextContent",
"ToolUseContent", "ElicitRequestParams", "ElicitResult",
"ServerNotification", "ToolListChangedNotification",
"PromptListChangedNotification", "ResourceListChangedNotification",
})
def __getattr__(name: str):
if name in _MCP_SDK_LAZY_SYMBOLS:
_ensure_mcp_sdk()
try:
return globals()[name]
except KeyError:
pass # SDK missing or symbol absent on this SDK build
raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
def _import_sdk_names(module: str, names: tuple, missing_msg: Optional[str] = None) -> bool:
"""Bind ``names`` from the SDK ``module`` into this module's globals.
False (plus an optional debug line) when this SDK build lacks the module or
any of the names; nothing is bound in that case.
"""
try:
mod = importlib.import_module(module)
values = {n: getattr(mod, n) for n in names}
except (ImportError, AttributeError):
if missing_msg:
logger.debug(missing_msg)
return False
globals().update(values)
return True
def _ensure_mcp_sdk() -> bool:
"""Import the optional ``mcp`` SDK on first use; return availability.
Idempotent and thread-safe. Honors a test-patched ``_MCP_AVAILABLE=False``
(no import) and pre-installed mock symbols (``ClientSession`` already set
means no re-import, so mocks are never clobbered). Optional type families
are gated separately so an older SDK only loses that feature, not MCP.
"""
global _MCP_SDK_IMPORT_ATTEMPTED, _MCP_AVAILABLE, _MCP_HTTP_AVAILABLE
global _MCP_SAMPLING_TYPES, _MCP_NOTIFICATION_TYPES, _MCP_ELICITATION_TYPES
global _MCP_MESSAGE_HANDLER_SUPPORTED, _MCP_LOGGING_CALLBACK_SUPPORTED
global _MCP_NEW_HTTP, _MCP_LEGACY_HTTP, LATEST_HANDSHAKE_VERSION, sse_client
global _JSONRPC_METHOD_NOT_FOUND
if not _MCP_AVAILABLE:
return False
if _MCP_SDK_IMPORT_ATTEMPTED or ClientSession is not None:
return _MCP_AVAILABLE
with _MCP_SDK_IMPORT_LOCK:
if _MCP_SDK_IMPORT_ATTEMPTED or ClientSession is not None:
return _MCP_AVAILABLE
if (
_import_sdk_names("mcp", ("ClientSession", "StdioServerParameters"))
and _import_sdk_names("mcp.client.stdio", ("stdio_client",))
):
_MCP_AVAILABLE = True
# mcp >= 1.24 ships streamable_http_client; 2.0 dropped the
# deprecated streamablehttp_client alias. Either one gives HTTP.
_MCP_NEW_HTTP = _import_sdk_names("mcp.client.streamable_http", ("streamable_http_client",))
_MCP_LEGACY_HTTP = _import_sdk_names("mcp.client.streamable_http", ("streamablehttp_client",))
_MCP_HTTP_AVAILABLE = _MCP_NEW_HTTP or _MCP_LEGACY_HTTP
_import_sdk_names(
"mcp.types", ("LATEST_PROTOCOL_VERSION",),
"mcp.types.LATEST_PROTOCOL_VERSION not available -- using fallback protocol version",
)
if not _import_sdk_names("mcp.client.session", ("LATEST_HANDSHAKE_VERSION",)):
# Pre-2.x SDKs: newest revision IS the handshake revision.
LATEST_HANDSHAKE_VERSION = LATEST_PROTOCOL_VERSION
if not _import_sdk_names(
"mcp.client.sse", ("sse_client",),
"mcp.client.sse.sse_client not available -- SSE transport disabled",
):
sse_client = None
_MCP_SAMPLING_TYPES = _import_sdk_names(
"mcp.types",
("CreateMessageResult", "CreateMessageResultWithTools", "ErrorData",
"SamplingCapability", "SamplingToolsCapability", "TextContent", "ToolUseContent"),
"MCP sampling types not available -- sampling disabled",
)
_MCP_ELICITATION_TYPES = _import_sdk_names(
"mcp.types", ("ElicitRequestParams", "ElicitResult"),
"MCP elicitation types not available -- elicitation disabled",
)
_MCP_NOTIFICATION_TYPES = _import_sdk_names(
"mcp.types",
("ServerNotification", "ToolListChangedNotification",
"PromptListChangedNotification", "ResourceListChangedNotification"),
"MCP notification types not available -- dynamic tool discovery disabled",
)
else:
logger.debug("mcp package not installed -- MCP tool support disabled")
if _MCP_AVAILABLE:
try:
_JSONRPC_METHOD_NOT_FOUND = importlib.import_module("mcp.types").METHOD_NOT_FOUND
except Exception: # pragma: no cover — SDK without the constant
pass
_MCP_MESSAGE_HANDLER_SUPPORTED = _client_session_accepts("message_handler")
if _MCP_AVAILABLE and not _MCP_MESSAGE_HANDLER_SUPPORTED:
logger.debug("MCP SDK does not support message_handler -- dynamic tool discovery disabled")
_MCP_LOGGING_CALLBACK_SUPPORTED = _client_session_accepts("logging_callback")
_MCP_SDK_IMPORT_ATTEMPTED = True
return _MCP_AVAILABLE
_SDK_HTTPX_MOD = None
def sdk_httpx():
"""Return the httpx module the *installed* MCP SDK is built against.
mcp 2.0 moved to ``httpx2`` (same API, separate distribution). Every
object crossing the SDK boundary — the ``AsyncClient`` passed to the
transport, OAuth ``Request`` objects, the exception classes — must come
from the module the SDK itself imports, or it fails at the transport
layer rather than at import. Resolved from the SDK's transport module, not
a version number. ``None`` only when neither module is importable.
"""
global _SDK_HTTPX_MOD
if _SDK_HTTPX_MOD is not None:
return _SDK_HTTPX_MOD
try:
from mcp.client import streamable_http as _transport
_SDK_HTTPX_MOD = getattr(_transport, "httpx2", None) or getattr(
_transport, "httpx", None
)
except ImportError:
_SDK_HTTPX_MOD = None
if _SDK_HTTPX_MOD is None:
# Transport module missing / renamed its import: newest present wins.
try:
import httpx2 as _fallback
except ImportError:
try:
import httpx as _fallback # type: ignore[no-redef]
except ImportError:
return None
_SDK_HTTPX_MOD = _fallback
return _SDK_HTTPX_MOD
def _client_session_accepts(kwarg: str) -> bool:
"""Whether this SDK's ``ClientSession.__init__`` takes ``kwarg``.
Older SDKs lack ``message_handler`` (no list_changed notifications) and
``logging_callback`` (server ``notifications/message`` silently dropped).
"""
if not _MCP_AVAILABLE:
return False
try:
return kwarg in inspect.signature(ClientSession).parameters
except (TypeError, ValueError):
return False
# MCP logging levels (RFC 5424 syslog severities) -> Python logging levels.
_MCP_LOG_LEVEL_MAP = {
"debug": logging.DEBUG,
"info": logging.INFO,
"notice": logging.INFO,
"warning": logging.WARNING,
"error": logging.ERROR,
"critical": logging.ERROR,
"alert": logging.ERROR,
"emergency": logging.ERROR,
}
# ---------------------------------------------------------------------------
# Reconnect / keepalive tuning
# ---------------------------------------------------------------------------
_DEFAULT_CONNECT_TIMEOUT = 60 # seconds for initial connection per server
_MAX_RECONNECT_RETRIES = 5
_MAX_INITIAL_CONNECT_RETRIES = 3 # retries for the very first connection attempt
_MAX_BACKOFF_SECONDS = 60
# Parked servers (budget exhausted, tools deregistered) self-probe on this
# cadence: with no tools registered nothing else can ever revive them.
_PARKED_RETRY_INTERVAL = 300 # seconds between parked self-probes
_RECYCLED_RECONNECT_TIMEOUT = 15.0
# Bounded wait for a respawned stdio child when a call finds it dead (gateway
# restarts kill every MCP child). Bounded so a broken server still parks via
# run()'s rapid-drop budget instead of hot-cycling respawns.
_STDIO_RESPAWN_WAIT_SEC = 15.0
# Servers may expire idle sessions on any TTL, so the client MUST ping faster
# than that TTL; servers with short TTLs (~15s) need a smaller configured
# ``keepalive_interval``. The floor stops a tiny interval from busy-looping.
_DEFAULT_KEEPALIVE_INTERVAL = 180 # seconds between liveness pings
_MIN_KEEPALIVE_INTERVAL = 5 # clamp floor for configured intervals
# One bounded cancellation cycle for pending loop tasks at final shutdown, so
# cancellation-resistant tasks cannot hang process exit.
_MCP_LOOP_DRAIN_TIMEOUT = 3.0
# JSON-RPC 2.0 "method not found" (e.g. a server without the optional ``ping``).
# _ensure_mcp_sdk() overrides it from mcp.types once the SDK is loaded.
_JSONRPC_METHOD_NOT_FOUND = -32601
# Cap on nextCursor pagination so a server returning a cursor forever cannot
# spin discovery; 50 pages at 50-100 items/page covers thousands of entries.
_MCP_LIST_MAX_PAGES = 50
async def _paginate_full_list(list_method, items_attr: str, server_name: str,
cache_meta_out: Optional[dict] = None):
"""Drain a paginated ``list_*`` call by following ``nextCursor``.
The SDK fetches one page per call, so without this every entry past page
1 would be invisible. ``cache_meta_out`` receives the first page's
SEP-2549 hints (``ttl_ms``, ``cache_scope``) when present. Callers must
hold the server's ``_rpc_lock`` so pages come from a consistent snapshot.
"""
items: list = []
cursor = None
for _ in range(_MCP_LIST_MAX_PAGES):
if not cursor:
result = await list_method()
else:
# mcp 2.0 takes params=PaginatedRequestParams, 1.x takes cursor=.
try:
_params_cls = getattr(_mcp_types(), "PaginatedRequestParams", None)
if _params_cls is not None:
result = await list_method(params=_params_cls(cursor=cursor))
else:
result = await list_method(cursor=cursor)
except TypeError:
result = await list_method(cursor=cursor)
if cache_meta_out is not None and not items:
_ttl = mcp_field(result, "ttl_ms", "ttlMs")
_scope = mcp_field(result, "cache_scope", "cacheScope")
if _ttl is not None:
cache_meta_out["ttl_ms"] = _ttl
if _scope is not None:
cache_meta_out["cache_scope"] = _scope
items.extend(getattr(result, items_attr, None) or [])
cursor = mcp_field(result, "next_cursor", "nextCursor")
# Cursor is an opaque string; anything else (incl. mocks) = last page.
if not isinstance(cursor, str) or not cursor:
break
else:
logger.warning(
"MCP server '%s': %s pagination exceeded %d pages; "
"truncating at %d items",
server_name, items_attr, _MCP_LIST_MAX_PAGES, len(items),
)
return items
def _mcp_types():
"""Late import of ``mcp.types`` (module keeps the SDK import lazy)."""
import mcp.types as _t
return _t
# ---------------------------------------------------------------------------
# Server task -- each MCP server lives in one long-lived asyncio Task
# ---------------------------------------------------------------------------
class MCPServerTask(MCPServerRunMixin, MCPServerTransportMixin, MCPServerHealthMixin):
"""One MCP server connection living in one long-lived asyncio Task.
Connect, discover, serve and disconnect all run in that Task so the
transport's anyio cancel scopes are entered and exited in the same Task.
Transport bring-up lives in ``MCPServerTransportMixin``; keepalive,
refresh and liveness in ``MCPServerHealthMixin``.
"""
__slots__ = (
"name", "session", "tool_timeout",
"_task", "_ready", "_shutdown_event", "_reconnect_event",
"_tools", "_error", "_config",
"_sampling", "_elicitation",
"_registered_tool_names", "_auth_type", "_refresh_lock",
"_rpc_lock", "_pending_refresh_tasks",
"_pending_call_context",
"_lifecycle_started_at", "_last_tool_call_at",
"_idle_timeout_seconds", "_max_lifetime_seconds", "_recycled_reason",
"initialize_result", "_ping_unsupported", "_list_cache_meta",
"_reconnect_retries", "_session_proven", "_was_parked",
"_inflight_tasks", "_reconnecting", "_suspect_reason",
"_teardown_race", "_permanent_grace_used", "_stdio_child_pids",
"_ever_connected",
)
def __init__(self, name: str):
self.name = name
self.session: Optional[Any] = None
self.tool_timeout: float = _DEFAULT_TOOL_TIMEOUT
self._task: Optional[asyncio.Task] = None
self._ready = asyncio.Event()
self._shutdown_event = asyncio.Event()
# When set, _run_http/_run_stdio exit their async-with cleanly and
# run() re-enters the transport (auth recovery, manual refresh, ...).
self._reconnect_event = asyncio.Event()
self._tools: list = []
self._error: Optional[Exception] = None
self._config: dict = {}
self._sampling: Optional[SamplingHandler] = None
self._elicitation: Optional[ElicitationHandler] = None
self._registered_tool_names: list[str] = []
self._reconnect_retries: int = 0
# Rapid-drop budget: a (re)established session is UNPROVEN until it
# survives a full keepalive interval or serves a successful call. Only
# a proven session clears the reconnect budget, so a transport that
# flaps right after the handshake still reaches the park.
self._session_proven: bool = False
# Set once tools were ever registered, never cleared (unlike _ready,
# which clears every reconnect cycle): separates a first-connect
# failure from a later reconnect failure in run()'s retry ladders.
self._ever_connected: bool = False
# True from park until the session proves healthy again; logs the
# parked->revived transition exactly once.
self._was_parked: bool = False
# In-flight RPC tasks, so a reconnect/shutdown teardown can fail them
# fast instead of orphaning them on a dying transport.
self._inflight_tasks: set = set()
# True while a deliberate teardown fails in-flight calls; lets
# _track_inflight_rpc turn the cancel into a retryable error.
self._reconnecting: bool = False
# Latched by races (teardown-vs-keepalive, auth-lock corruption);
# verified lazily by ensure_healthy() before the next call.
self._suspect_reason: Optional[str] = None
# A teardown that failed >=1 in-flight call makes the next reconnect a
# RACE RECOVERY: it must not charge the rapid-drop budget.
self._teardown_race: bool = False
# One-time grace: an auth/permanent-classified failure on a previously
# PROVEN session gets one suspect+reconnect cycle before the park
# ladder applies (single auth-lock corruption must not park).
self._permanent_grace_used: bool = False
# Children of the current stdio transport: lets in-flight calls fail
# FAST when the child dies instead of riding out the tool timeout.
self._stdio_child_pids: Set[int] = set()
self._auth_type: str = ""
self._refresh_lock = asyncio.Lock()
# A stdio session is one JSON-RPC stream: a list_tools issued by the
# notification handler while a tool call is in flight can wedge it.
# Serialize client-initiated RPCs per server (HTTP too, for ordering).
self._rpc_lock = asyncio.Lock()
self._pending_refresh_tasks: set[asyncio.Task] = set()
# contextvars snapshot of the agent task inside session.call_tool().
# The SDK dispatches elicitation/create on a separate task that does
# not inherit HERMES_SESSION_PLATFORM; replaying this context in the
# elicitation callback routes the approval prompt to the right surface.
self._pending_call_context: Optional[contextvars.Context] = None
now = time.monotonic()
self._lifecycle_started_at: float = now
self._last_tool_call_at: float = now
self._idle_timeout_seconds: Optional[float] = None
self._max_lifetime_seconds: Optional[float] = None
self._recycled_reason: Optional[str] = None
# InitializeResult from the handshake: the server's REAL advertised
# capabilities, used instead of assuming every ClientSession method
# maps to a supported server method.
self.initialize_result: Optional[Any] = None
# SEP-2549 cache hints from the last tools/list (ttl_ms, cache_scope).
self._list_cache_meta: dict = {}
# Latched when keepalive ``ping`` returns -32601 (optional utility not
# implemented); later keepalives use list_tools instead of
# reconnect-looping. Reset on every fresh transport connection.
self._ping_unsupported: bool = False
# Content types a real Streamable-HTTP endpoint may return on the initial
# POST/GET; anything else on a 2xx means the URL is not an MCP endpoint.
_MCP_CONTENT_TYPES = ("application/json", "text/event-stream")
# ---------------------------------------------------------------------------
# Module-level state (every mutation under ``_lock``)
# ---------------------------------------------------------------------------
_servers: Dict[str, MCPServerTask] = {}
# Profile registry scope owning each live connection (None outside multiplex):
# a multiplexed /reload-mcp tears down only its own profile's servers.
_server_scope_keys: Dict[str, Optional[str]] = {}
_server_connecting: set[str] = set()
_server_connect_errors: Dict[str, str] = {}
# Lazy startup: servers registered from the on-disk schema cache without
# connecting; popped once a real connection is established on first use.
_lazy_server_configs: Dict[str, dict] = {}
_lazy_server_fingerprints: Dict[str, str] = {}
_lazy_server_tool_names: Dict[str, List[str]] = {}
# Discovery installs a task-local claim around ``_connect_server`` so it can
# retain a recoverable parked task without standalone probe calls publishing
# failed servers into module-global ownership.
_connect_server_claim: contextvars.ContextVar[
Optional[Callable[[MCPServerTask], None]]
] = contextvars.ContextVar("mcp_connect_server_claim", default=None)
# Per-server connect cooldown. A server that fails to spawn never reaches
# ``_servers``, so without this every ``discover_mcp_tools()`` (one per worker
# session) would respawn it from scratch — a restart storm whose unreaped
# subprocesses destabilise the healthy co-located servers. Failed attempts
# stamp an exponential-backoff deadline that ``register_mcp_servers`` honours;
# a successful connection clears it.
_server_connect_retry_after: Dict[str, float] = {} # name -> monotonic deadline
_server_connect_failures: Dict[str, int] = {} # name -> consecutive failures
_CONNECT_RETRY_BASE_BACKOFF_SEC = 30.0
_CONNECT_RETRY_MAX_BACKOFF_SEC = 600.0
# Circuit breaker per server: closed (count < threshold) -> open (calls
# short-circuit with a "stop retrying" message until the cooldown elapses) ->
# half-open (next call is a probe; success closes, failure re-arms). Mutate
# only via _bump_server_error / _reset_server_error, which keep the count and
# the open timestamp in sync.
_server_error_counts: Dict[str, int] = {}
_server_breaker_opened_at: Dict[str, float] = {}
_CIRCUIT_BREAKER_THRESHOLD = 3
_CIRCUIT_BREAKER_COOLDOWN_SEC = 60.0
# Trust-tier gating (``mcp_servers.<name>.trust: full | untrusted``). On an
# untrusted server every write-capable call needs user approval before the
# RPC fires; a tool is write-capable unless its discovery-time
# ``annotations.readOnlyHint`` is exactly True (malformed fails closed).
# Security model: readOnlyHint is a server-supplied HINT and a hostile server
# can lie, but on an untrusted server a lie can only skip approval for calls
# the operator was already warned about — never widen access. Missing
# ``trust`` defaults to full (backward compatible); any unrecognized value
# normalizes to untrusted (a typo must never disable the gate). Classified
# at CALL time from DISCOVERY data: no schema mutation, prompt cache intact.
_server_trust_levels: Dict[str, str] = {}
_tool_read_only_hints: Dict[str, Dict[str, bool]] = {}
_TRUST_FULL = "full"
_TRUST_UNTRUSTED = "untrusted"
def _bump_server_error(server_name: str) -> None:
"""Count a failure; at the threshold (re)stamp the breaker-open time."""
n = _server_error_counts.get(server_name, 0) + 1
_server_error_counts[server_name] = n
if n >= _CIRCUIT_BREAKER_THRESHOLD:
_server_breaker_opened_at[server_name] = time.monotonic()
def _reset_server_error(server_name: str) -> None:
"""Close the breaker on any unambiguous success signal."""
_server_error_counts[server_name] = 0
_server_breaker_opened_at.pop(server_name, None)
# Raw server names opted into parallel tool calls. Raw identity matters:
# ``foo-bar`` and ``foo_bar`` both sanitize to ``foo_bar`` but must not share
# policy.
_parallel_safe_servers: set = set()
# registry tool name -> raw server name, captured at registration. The
# generated name is lossy (punctuation -> ``_``), so never re-parse it.
_mcp_tool_server_names: Dict[str, str] = {}
# Dedicated event loop running in a background daemon thread.
_mcp_loop: Optional[asyncio.AbstractEventLoop] = None
_mcp_thread: Optional[threading.Thread] = None
# Guards the loop handles, _servers, the status maps and the PID ledgers.
_lock = threading.Lock()
def _mcp_registry_scope() -> Optional[str]:
"""Registry scope for MCP registrations from the current context.
Under a profile multiplexer each profile's MCP tools live in its own
registry overlay; single-profile processes stay process-global (None).
"""
from agent.secret_scope import is_multiplex_active
if not is_multiplex_active():
return None
from tools.registry import registry
return registry.current_scope_key()
def _server_registry_scope(name: str) -> Optional[str]:
"""Scope owning server *name*'s tools: recorded at connect, else current.
Teardown runs on the MCP loop without the discovering profile's context,
so the scope captured at adoption into ``_servers`` is authoritative.
"""
if name in _server_scope_keys:
return _server_scope_keys[name]
return _mcp_registry_scope()
# ---------------------------------------------------------------------------
# Cross-process MCP discovery guard: advisory file lock so gateway + CLI + TUI
# don't all run discovery at once.
# ---------------------------------------------------------------------------
_LOCK_UNAVAILABLE: Any = object() # sentinel: locking broken/unavailable
_MCP_DISCOVERY_LOCK_PATH: Optional[str] = None # resolved lazily
# Bounded wait when another process holds the lock.
_MCP_DISCOVERY_LOCK_MAX_RETRIES: int = 240
_MCP_DISCOVERY_LOCK_RETRY_DELAY_S: float = 0.5
# ---------------------------------------------------------------------------
# Connecting, lazy start, discovery
# ---------------------------------------------------------------------------
# ---------------------------------------------------------------------------
# Public API
# ---------------------------------------------------------------------------
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