Teknium
646 lines
31 KiB
Python
646 lines
31 KiB
Python
"""Transport bring-up for MCPServerTask: stdio spawn (OSV preflight, watchdog wrap, child PID ledger), Streamable HTTP / SSE connect (preflight, identity header, client certs, OAuth), protocol negotiation and initial tool discovery. Split from tools/mcp_tool.py."""
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import logging
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import asyncio
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import os
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from contextlib import asynccontextmanager
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from typing import Dict, Optional, Set
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from tools.mcp_tool_config import _wrap_command_with_watchdog
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from tools.mcp_tool_errors import NonMcpEndpointError, _apply_identity_header, _handshake_rejected_as_modern, _make_redirect_header_stripper, _resolve_client_cert
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from tools.mcp_tool_lifecycle import _filter_mcp_children, _orphan_stdio_pid_servers, _orphan_stdio_pids, _stdio_pgids, _stdio_pids
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from tools.mcp_tool_common import _core
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logger = logging.getLogger("tools.mcp_tool")
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# JSON-RPC ``initialize`` body used by the content-type preflight POST.
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_PROBE_INITIALIZE_BODY = (
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'{"jsonrpc":"2.0","id":"_probe",'
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'"method":"initialize",'
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'"params":{"protocolVersion":"2025-03-26",'
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'"capabilities":{},'
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'"clientInfo":{"name":"hermes-probe",'
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'"version":"0.1"}}}'
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)
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def _content_type_base(resp) -> str:
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"""``content-type`` header of *resp* without parameters, lowercased."""
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return resp.headers.get("content-type", "").split(";")[0].strip().lower()
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def _is_2xx(resp) -> bool:
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return 200 <= resp.status_code < 300
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def _capture_pgids(pids: Set[int]) -> Dict[int, int]:
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"""pgid per live pid. Captured while the child is alive — getpgid fails once
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it exits, and the sweep needs it to reach reparented descendants."""
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pgids: Dict[int, int] = {}
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for pid in pids:
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try:
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pgids[pid] = os.getpgid(pid)
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except (AttributeError, ProcessLookupError, OSError):
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# AttributeError: Windows; ProcessLookupError: already exited.
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pass
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return pgids
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def _pgroup_alive(pgid: Optional[int]) -> bool:
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"""Signal 0 to the group succeeds iff any member is alive (POSIX only)."""
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_killpg = getattr(os, "killpg", None)
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if pgid is None or _killpg is None:
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return False
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try:
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_killpg(pgid, 0)
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return True
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except (ProcessLookupError, PermissionError, OSError):
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return False
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async def _osv_malware_preflight(server_name: str, command: str, args: list) -> None:
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"""OSV malware preflight: off-loop (blocking HTTPS) with a wall-clock bound so
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a stalled handshake can't freeze discovery; fail-open on timeout. Must run
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against the REAL command/args — the watchdog wrap rewrites argv to the
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supervisor, which would turn the check into a no-op."""
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from tools.osv_check import check_package_for_malware
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try:
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malware_error = await asyncio.wait_for(
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asyncio.to_thread(check_package_for_malware, command, args),
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timeout=_core._OSV_MALWARE_CHECK_TIMEOUT_S,
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)
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except asyncio.TimeoutError:
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logger.warning(
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"MCP server '%s': OSV malware preflight timed out after %.0fs "
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"(network slow/unreachable) — proceeding without the check.",
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server_name, _core._OSV_MALWARE_CHECK_TIMEOUT_S,
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)
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return
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if malware_error:
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raise ValueError(f"MCP server '{server_name}': {malware_error}")
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class MCPServerTransportMixin:
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"""Methods of :class:`tools.mcp_tool.MCPServerTask` (mixed in; relies on its attributes)."""
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__slots__ = ()
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def _advertises_tools(self) -> bool:
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"""Whether the server advertises the ``tools`` capability.
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Prompt-/resource-only servers omit it, and ``tools/list`` against them
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raises ``MCPError(-32601)``. True when no capability info was captured
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(legacy fallback: keep the old always-call-list_tools behavior).
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"""
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init_result = self.initialize_result
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caps = getattr(init_result, "capabilities", None) if init_result is not None else None
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if caps is None:
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return True
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return getattr(caps, "tools", None) is not None
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def _session_kwargs(self) -> dict:
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"""ClientSession kwargs: sampling, elicitation, notification + logging callbacks."""
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kwargs = self._sampling.session_kwargs() if self._sampling else {}
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if self._elicitation:
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kwargs.update(self._elicitation.session_kwargs())
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if _core._MCP_NOTIFICATION_TYPES and _core._MCP_MESSAGE_HANDLER_SUPPORTED:
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kwargs["message_handler"] = self._make_message_handler()
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if _core._MCP_LOGGING_CALLBACK_SUPPORTED:
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kwargs["logging_callback"] = self._make_logging_callback()
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return kwargs
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async def _negotiate_session(self, session, connect_timeout: float):
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"""Negotiate the protocol era (``initialize`` vs ``server/discover``) and return its result.
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Per-server ``protocol`` key: ``auto`` (default) tries the legacy handshake
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FIRST and falls back to ``server/discover`` only when the server signals
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modern-only (-32022 / initialize -32601) — the reverse of the SDK's
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discover-first mode, on purpose: zero extra round-trips for the handshake-era
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servers that dominate today. ``stateless`` probes discover first (one legacy
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retry on error); ``legacy`` is handshake only, no fallback. Both result
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types expose ``.capabilities``, so downstream gates work on either.
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A handshake TIMEOUT never triggers a fallback — it propagates.
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"""
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def initialize():
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return asyncio.wait_for(session.initialize(), timeout=connect_timeout)
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def discover():
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return asyncio.wait_for(session.discover(), timeout=connect_timeout)
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mode = str((self._config or {}).get("protocol", "auto")).lower().strip()
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if mode in ("stateless", "modern", "2026-07-28"):
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try:
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return await discover()
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except asyncio.TimeoutError:
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raise
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except Exception as exc:
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logger.info(
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"MCP server '%s': server/discover rejected (%s) despite "
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"protocol=%s — falling back to the legacy handshake",
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self.name, exc, mode,
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)
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return await initialize()
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if mode in ("legacy", "handshake"):
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return await initialize()
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if mode != "auto":
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logger.warning(
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"MCP server '%s': unknown protocol=%r — treating as 'auto' "
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"(valid: auto, stateless, legacy)", self.name, mode,
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)
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try:
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return await initialize()
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except asyncio.TimeoutError:
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raise
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except Exception as exc:
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# mcp 1.x has no server/discover client — nothing to fall back to.
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if not _handshake_rejected_as_modern(exc) or not hasattr(session, "discover"):
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raise
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logger.info(
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"MCP server '%s': legacy handshake rejected (%s) — "
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"retrying via server/discover (2026-07-28 stateless server)",
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self.name, exc,
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)
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return await discover()
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async def _serve_session(self, session, connect_timeout: float,
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label: str = "", mark_lifecycle: bool = False) -> str:
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"""Handshake, discover, publish readiness, then serve until a lifecycle event.
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Clears stale breaker state from a prior outage, but leaves the session
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UNPROVEN: a completed handshake is not proof of health (flapping
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transports handshake fine and drop moments later); only keepalive or
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tool-call success clears the reconnect budget.
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"""
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self.initialize_result = await self._negotiate_session(session, connect_timeout)
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self.session = session
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if mark_lifecycle:
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self._mark_lifecycle_started()
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await self._discover_tools()
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self._ready.set()
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self._ever_connected = True
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_core._reset_server_error(self.name)
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self._session_proven = False
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reason = await self._wait_for_lifecycle_event()
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if label and reason == "reconnect":
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logger.info("MCP server '%s': reconnect requested — tearing down %s session", self.name, label)
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return reason
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async def _serve_transport(self, transport_cm, label: str, connect_timeout: float) -> str:
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"""Open *transport_cm*, wrap its streams in a ClientSession and serve it.
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Streams are unpacked positionally: mcp 1.x yields ``(read, write,
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get_session_id)``, 2.x yields ``(read, write)``. A transport TaskGroup
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drop maps to ``"reconnect"`` instead of backoff/park.
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"""
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try:
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async with transport_cm as _streams:
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async with _core.ClientSession(
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_streams[0], _streams[1], **self._session_kwargs()
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) as session:
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return await self._serve_session(session, connect_timeout, label)
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except BaseExceptionGroup as _eg:
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return self._reconnect_or_reraise_group(_eg)
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# ------------------------------------------------------------------ stdio
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def _resolve_stdio_config(self, config: dict):
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"""``(command, args, safe_env)`` from config, with the command resolved against the safe env."""
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command = config.get("command")
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if not command:
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raise ValueError(f"MCP server '{self.name}' has no 'command' in config")
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args = config.get("args", [])
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safe_env = _core._build_safe_env(config.get("env"))
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command, safe_env = _core._resolve_stdio_command(command, safe_env)
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return command, args, safe_env
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def _track_spawned_children(self, new_pids: Set[int]) -> None:
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"""Ledger the freshly spawned stdio children (pids, pgids, machine spawn ledger)."""
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new_pgids = _capture_pgids(new_pids)
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with _core._lock:
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for _pid in new_pids:
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_stdio_pids[_pid] = self.name
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_stdio_pgids.update(new_pgids)
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# Machine spawn ledger so startup sweeps can reap orphans after an
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# unclean parent exit. Best-effort — never break startup.
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for _pid in new_pids:
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try:
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from hermes_cli.process_identity import register_child
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register_child(_pid, "mcp-helper")
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except Exception:
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logger.debug("spawn-ledger register_child failed for MCP helper pid %s", _pid, exc_info=True)
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def _release_spawned_children(self, new_pids: Set[int]) -> None:
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"""Drop the ledger entries; any child (or its pgroup) still alive means SDK
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teardown failed (common on cancel mid-way on Linux, where setsid() children
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escape the cgroup) — mark it orphaned for the next cleanup sweep."""
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from gateway.status import _pid_exists
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with _core._lock:
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for _pid in new_pids:
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_stdio_pids.pop(_pid, None)
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for pid in new_pids:
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# ``os.kill(pid, 0)`` is NOT a no-op on Windows; use the
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# cross-platform check. Child exited but descendants may remain
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# in its pgroup.
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if _pid_exists(pid) or _pgroup_alive(_stdio_pgids.get(pid)):
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_orphan_stdio_pids.add(pid)
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_orphan_stdio_pid_servers[pid] = self.name
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else:
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# Nothing to reap — drop the pgid so PID reuse can't
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# surface stale pgroup state later.
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_stdio_pgids.pop(pid, None)
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async def _run_stdio(self, config: dict):
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"""Run the server using stdio transport."""
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if config.get("identity_header") is not None:
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# No headers on stdio — warn so a copy-pasted HTTP block doesn't mislead.
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logger.warning(
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"MCP server '%s': identity_header is only supported on "
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"HTTP/SSE transports — ignored for stdio servers", self.name,
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)
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if not _core._ensure_mcp_sdk():
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raise ImportError(
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f"MCP server '{self.name}' requires the 'mcp' Python SDK, but "
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"it is not installed. Run `hermes setup` to install MCP support, then retry."
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)
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command, args, safe_env = self._resolve_stdio_config(config)
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await _osv_malware_preflight(self.name, command, args)
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# Parent-death watchdog: an ungraceful Hermes exit (kill -9, crash) can't
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# leave the child and its descendants running. Clean-exit reaping is
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# unchanged. POSIX-only (process groups); no-op elsewhere. AFTER the OSV
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# preflight so the check inspects the real package.
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command, args = _wrap_command_with_watchdog(command, args)
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server_params = _core.StdioServerParameters(
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command=command,
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args=args,
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env=safe_env if safe_env else None,
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cwd=config.get("cwd"),
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# Windows pipes can split non-UTF-8 bytes at chunk boundaries;
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# substitute U+FFFD instead of raising UnicodeDecodeError.
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encoding_error_handler="replace",
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)
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session_kwargs = self._session_kwargs()
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# Reap orphans from prior failed attempts before spawning, else each
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# reconnect retry piles up zombie pairs. Unscoped on purpose (also reaps
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# orphans of servers that never reconnect). Worker thread: the reaper
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# blocks up to 2s (SIGTERM → wait → SIGKILL) and would stall the loop.
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await asyncio.to_thread(_core._kill_orphaned_mcp_children)
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# Snapshot child PIDs before spawning so the new one can be identified.
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pids_before = _core._snapshot_child_pids()
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new_pids: set = set()
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# Route subprocess stderr to ~/.hermes/logs/mcp-stderr.log so server
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# banners don't land on the user's TTY and corrupt the TUI.
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_core._write_stderr_log_header(self.name)
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_errlog = _core._get_mcp_stderr_log()
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try:
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async with _core.stdio_client(server_params, errlog=_errlog) as (
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read_stream,
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write_stream,
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):
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# Capture the new PID for force-kill cleanup, filtering non-MCP
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# children (slash_worker, LSP servers) that race into the snapshot
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# window: they share the TUI parent's pgid, so leaking them into
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# _stdio_pgids makes the shutdown killpg() kill the TUI itself.
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new_pids = _filter_mcp_children(_core._snapshot_child_pids() - pids_before)
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if new_pids:
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self._track_spawned_children(new_pids)
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# Tracked on the connection so in-flight calls fail fast when
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# the subprocess dies.
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self._stdio_child_pids = set(new_pids)
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async with _core.ClientSession(
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read_stream, write_stream, **session_kwargs
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) as session:
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# Bound the handshake: ``connect_timeout`` only bounds the
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# caller's ``.result()`` wait, not this coroutine. A server that
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# never answers ``initialize`` would otherwise hang here forever,
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# the ``finally`` below would never run, and the child + pipes
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# would leak on every retry until EMFILE.
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connect_timeout = float(config.get("connect_timeout", _core._DEFAULT_CONNECT_TIMEOUT))
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return await self._serve_session(session, connect_timeout, mark_lifecycle=True)
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finally:
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# Runs on clean exit, exceptions AND cancellation.
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if new_pids:
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self._release_spawned_children(new_pids)
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# ------------------------------------------------------------------- HTTP
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async def _preflight_content_type(
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self,
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url: str,
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*,
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headers: Optional[dict] = None,
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ssl_verify: bool = True,
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client_cert=None,
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timeout: float = 5.0,
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) -> None:
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"""Probe *url* for an MCP-shaped response before the SDK connects.
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A URL pointing at a plain web page makes the SDK sit out the full
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``connect_timeout`` before an opaque ``CancelledError``; this raises
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:class:`NonMcpEndpointError` within ``timeout`` instead. Allow-list based:
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only a 2xx with a definite non-MCP content type is rejected, and only
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after a JSON-RPC ``initialize`` POST also fails to look like MCP (some
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servers serve a UI on GET but speak Streamable HTTP via POST). Missing
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content type, non-2xx, or transport errors pass silently — the real
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handshake stays the source of truth. Uses its own httpx client OUTSIDE
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the SDK's anyio task group so the error isn't wrapped in an ExceptionGroup.
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"""
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try:
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import httpx as _httpx
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except ImportError:
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return # No httpx → skip probe; SDK import would have failed first.
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client_kwargs: dict = {
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"verify": ssl_verify,
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"follow_redirects": True,
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"timeout": _httpx.Timeout(timeout),
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}
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if client_cert is not None:
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client_kwargs["cert"] = client_cert
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probe_headers = dict(headers) if headers else {}
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try:
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async with _httpx.AsyncClient(**client_kwargs) as client:
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# HEAD is cheapest; fall back to GET on 405/501.
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resp = await client.head(url, headers=probe_headers)
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if resp.status_code in (405, 501):
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resp = await client.get(url, headers=probe_headers)
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# Non-MCP content type on HEAD/GET: try a JSON-RPC POST before
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# rejecting, so POST-only servers aren't false positives.
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ct = _content_type_base(resp)
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if ct and ct not in self._MCP_CONTENT_TYPES and _is_2xx(resp):
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post_resp = await client.post(
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url,
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headers={
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**probe_headers,
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"Content-Type": "application/json",
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"Accept": "application/json, text/event-stream",
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},
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content=_PROBE_INITIALIZE_BODY,
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)
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if _is_2xx(post_resp) and _content_type_base(post_resp) in self._MCP_CONTENT_TYPES:
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resp = post_resp
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except _httpx.HTTPError:
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return # DNS/connect/timeout/transport error — let the SDK try.
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# Only judge 2xx: a 4xx/5xx may be an auth challenge or transient error
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# the real handshake handles correctly. No content type advertised →
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# don't second-guess the SDK.
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if not _is_2xx(resp):
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return
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ct_base = _content_type_base(resp)
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if not ct_base or ct_base in self._MCP_CONTENT_TYPES:
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return
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raise NonMcpEndpointError(
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f"MCP server '{self.name}' at {url} returned Content-Type '{ct_base}', not an MCP "
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f"response (expected one of: {', '.join(self._MCP_CONTENT_TYPES)}). The URL most likely "
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"points at a web page rather than an MCP endpoint — check it resolves to a Streamable "
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"HTTP / SSE endpoint (e.g. https://host/mcp, not https://host/)."
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)
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def _reconnect_or_reraise_group(self, eg: BaseExceptionGroup) -> str:
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"""Map an SDK transport TaskGroup failure to a clean ``"reconnect"``.
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HTTP/SSE stream pumps run in an anyio TaskGroup, so a transient stream
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drop escapes as a ``BaseExceptionGroup``. Unmapped, ``run()`` would back
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off and eventually park the server for 300s (deregistering its tools)
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over a sub-second glitch; ``"reconnect"`` rebuilds the session at once.
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Re-raise when it is not a transient drop: shutdown in progress
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(``_shutdown_event`` is set before the task is cancelled), the group
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carries KeyboardInterrupt/SystemExit or a real CancelledError (must
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propagate), or no live session was reached this attempt (``_ready``
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unset — connect failures must go through backoff, not hot-loop).
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"""
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if (
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self._shutdown_event.is_set()
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or eg.split((KeyboardInterrupt, SystemExit))[0] is not None
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or eg.split(asyncio.CancelledError)[0] is not None
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or not self._ready.is_set()
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):
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raise eg
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logger.debug(
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"MCP server '%s': transport TaskGroup exited after a live session "
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"(%r) — reconnecting immediately instead of backing off",
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self.name, eg,
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)
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return "reconnect"
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def _build_oauth_auth(self, url: str, config: dict):
|
|
"""OAuth 2.1 PKCE via the central MCPOAuthManager so one provider is reused
|
|
across reconnects and shared with config-time CLI paths. On setup failure
|
|
(e.g. non-interactive without cached tokens) re-raise so only this server
|
|
is reported failed."""
|
|
if self._auth_type != "oauth":
|
|
return None
|
|
try:
|
|
from tools.mcp_oauth_manager import get_manager
|
|
return get_manager().get_or_build_provider(self.name, url, config.get("oauth"))
|
|
except Exception as exc:
|
|
logger.warning("MCP OAuth setup failed for '%s': %s", self.name, exc)
|
|
raise
|
|
|
|
def _sse_transport(self, url: str, headers: dict, connect_timeout: float,
|
|
ssl_verify, client_cert, oauth_auth, strict_cfg_headers: bool):
|
|
"""``sse_client`` context manager for ``transport: sse`` entries."""
|
|
if strict_cfg_headers:
|
|
# Fail closed: SSE cannot enforce the redirect boundary.
|
|
raise ValueError(
|
|
f"MCP server '{self.name}': strict_redirect_headers is "
|
|
"not supported on the SSE transport."
|
|
)
|
|
if _core.sse_client is None:
|
|
raise ImportError(
|
|
f"MCP server '{self.name}' requires SSE transport but "
|
|
"mcp.client.sse.sse_client is not available. "
|
|
"Upgrade the mcp package to get SSE support."
|
|
)
|
|
# sse_read_timeout bounds the gap between SSE events. SSE servers
|
|
# commonly idle for minutes, so tool_timeout (60s) would drop the
|
|
# stream; 300s matches the Streamable HTTP read timeout.
|
|
sse_kwargs: dict = {
|
|
"url": url,
|
|
"headers": headers or None,
|
|
"timeout": float(connect_timeout),
|
|
"sse_read_timeout": 300.0,
|
|
}
|
|
if oauth_auth is not None:
|
|
# Forward OAuth to sse_client, else OAuth SSE servers 401 silently.
|
|
sse_kwargs["auth"] = oauth_auth
|
|
if client_cert is not None or ssl_verify is not True:
|
|
# sse_client has no verify/cert kwargs: wrap the SDK defaults
|
|
# (follow_redirects=True) in an httpx_client_factory, forwarding
|
|
# the SDK's (headers, auth, timeout) and layering TLS on top. The
|
|
# client MUST come from the SDK's own httpx module (httpx2 on
|
|
# mcp >= 2.0) — see sdk_httpx().
|
|
_httpx_mod = _core.sdk_httpx()
|
|
|
|
def _mcp_http_client_factory(headers=None, timeout=None, auth=None):
|
|
kwargs: dict = {
|
|
"follow_redirects": True,
|
|
"verify": ssl_verify,
|
|
"timeout": timeout if timeout is not None else _httpx_mod.Timeout(30.0, read=300.0),
|
|
}
|
|
if headers is not None:
|
|
kwargs["headers"] = headers
|
|
if auth is not None:
|
|
kwargs["auth"] = auth
|
|
if client_cert is not None:
|
|
kwargs["cert"] = client_cert
|
|
return _httpx_mod.AsyncClient(**kwargs)
|
|
|
|
sse_kwargs["httpx_client_factory"] = _mcp_http_client_factory
|
|
return _core.sse_client(**sse_kwargs)
|
|
|
|
def _streamable_http_transport(self, url: str, headers: dict, connect_timeout: float,
|
|
ssl_verify, client_cert, oauth_auth,
|
|
strict_cfg_headers: bool, configured_header_names: set):
|
|
"""Streamable HTTP context manager (mcp >= 1.24.0: caller-owned httpx client)."""
|
|
if not _core._MCP_NEW_HTTP:
|
|
return self._legacy_http_transport(url, headers, connect_timeout, ssl_verify,
|
|
oauth_auth, strict_cfg_headers)
|
|
# Build an explicit AsyncClient matching the SDK's create_mcp_http_client
|
|
# defaults. It MUST come from the SDK's httpx module (httpx2 on mcp >= 2.0)
|
|
# since the SDK sends its own Request objects through it — see sdk_httpx().
|
|
httpx = _core.sdk_httpx()
|
|
_strip_auth_on_cross_origin_redirect = _make_redirect_header_stripper(
|
|
httpx.URL(url),
|
|
strict=strict_cfg_headers,
|
|
configured_header_names=configured_header_names,
|
|
)
|
|
client_kwargs: dict = {
|
|
"follow_redirects": True,
|
|
"timeout": httpx.Timeout(float(connect_timeout), read=300.0),
|
|
"verify": ssl_verify,
|
|
"event_hooks": {"response": [_strip_auth_on_cross_origin_redirect]},
|
|
}
|
|
if headers:
|
|
client_kwargs["headers"] = headers
|
|
if oauth_auth is not None:
|
|
client_kwargs["auth"] = oauth_auth
|
|
if client_cert is not None:
|
|
client_kwargs["cert"] = client_cert
|
|
|
|
@asynccontextmanager
|
|
async def _owned_client_streams():
|
|
# Caller owns the client lifecycle — the SDK skips cleanup when
|
|
# http_client is provided.
|
|
async with httpx.AsyncClient(**client_kwargs) as http_client:
|
|
async with _core.streamable_http_client(url, http_client=http_client) as streams:
|
|
yield streams
|
|
|
|
return _owned_client_streams()
|
|
|
|
def _legacy_http_transport(self, url: str, headers: dict, connect_timeout: float,
|
|
ssl_verify, oauth_auth, strict_cfg_headers: bool):
|
|
"""Deprecated API (mcp < 1.24.0): the SDK owns the httpx client."""
|
|
if strict_cfg_headers:
|
|
# Fail closed: without an owned client we cannot hook redirects,
|
|
# so the cross-origin header boundary cannot be enforced.
|
|
raise ImportError(
|
|
f"MCP server '{self.name}' requires mcp >= 1.24.0 to "
|
|
"enforce the portable redirect-header boundary "
|
|
"(strict_redirect_headers). Upgrade the mcp package."
|
|
)
|
|
http_kwargs: dict = {"headers": headers, "timeout": float(connect_timeout), "verify": ssl_verify}
|
|
if oauth_auth is not None:
|
|
http_kwargs["auth"] = oauth_auth
|
|
return _core.streamablehttp_client(url, **http_kwargs)
|
|
|
|
async def _run_http(self, config: dict):
|
|
"""Run the server using HTTP/StreamableHTTP (or SSE) transport."""
|
|
_core._ensure_mcp_sdk()
|
|
if not _core._MCP_HTTP_AVAILABLE:
|
|
raise ImportError(
|
|
f"MCP server '{self.name}' requires HTTP transport but "
|
|
"mcp.client.streamable_http is not available. "
|
|
"Upgrade the mcp package to get HTTP support."
|
|
)
|
|
url = config["url"]
|
|
headers = dict(config.get("headers") or {})
|
|
# Portable Agent Plugins v1 (strict_redirect_headers): configured
|
|
# headers MUST NOT follow a redirect to a different origin. Capture the
|
|
# configured names BEFORE client-generated headers are merged in.
|
|
strict_cfg_headers = bool(config.get("strict_redirect_headers"))
|
|
configured_header_names = {key.lower() for key in headers}
|
|
# Optional per-user identity header; explicit headers of the same name win.
|
|
headers = _apply_identity_header(self.name, config, headers)
|
|
# Some servers require MCP-Protocol-Version on the initial request; seed
|
|
# it (case-insensitive user override wins). Seeded from the HANDSHAKE
|
|
# version, not the latest: the body sent by ``initialize()`` speaks the
|
|
# handshake era, and a 2026-07-28 header would route the request onto
|
|
# the server's per-request-envelope ladder, which rejects that body.
|
|
# The header must agree with what the body actually speaks.
|
|
if not any(key.lower() == "mcp-protocol-version" for key in headers):
|
|
headers["mcp-protocol-version"] = _core.LATEST_HANDSHAKE_VERSION
|
|
connect_timeout = config.get("connect_timeout", _core._DEFAULT_CONNECT_TIMEOUT)
|
|
ssl_verify = config.get("ssl_verify", True)
|
|
client_cert = _resolve_client_cert(self.name, config)
|
|
oauth_auth = self._build_oauth_auth(url, config)
|
|
|
|
if config.get("transport") == "sse":
|
|
transport = self._sse_transport(url, headers, connect_timeout, ssl_verify,
|
|
client_cert, oauth_auth, strict_cfg_headers)
|
|
label = "SSE"
|
|
else:
|
|
transport = self._streamable_http_transport(
|
|
url, headers, connect_timeout, ssl_verify, client_cert, oauth_auth,
|
|
strict_cfg_headers, configured_header_names,
|
|
)
|
|
label = "HTTP" if _core._MCP_NEW_HTTP else "legacy HTTP"
|
|
return await self._serve_transport(transport, label, float(connect_timeout))
|
|
|
|
# -------------------------------------------------------------- discovery
|
|
|
|
async def _discover_tools(self):
|
|
"""Discover tools from the connected session.
|
|
|
|
Capability-gated: prompt-/resource-only servers raise ``MCPError(-32601)``
|
|
on ``tools/list``, which would abort the connection — skip the call when
|
|
``tools`` isn't advertised.
|
|
"""
|
|
# Fresh transport: re-probe with cheap ``ping`` in case the server gained
|
|
# support across the reconnect.
|
|
self._ping_unsupported = False
|
|
if self.session is None:
|
|
return
|
|
if not self._advertises_tools():
|
|
logger.info(
|
|
"MCP server '%s': does not advertise 'tools' capability — "
|
|
"skipping tools/list (prompts/resources remain available)",
|
|
self.name,
|
|
)
|
|
self._tools = []
|
|
self._register_discovered_tools_if_needed()
|
|
return
|
|
async with self._rpc_lock:
|
|
self._list_cache_meta = {}
|
|
self._tools = await _core._paginate_full_list(
|
|
self.session.list_tools, "tools", self.name,
|
|
cache_meta_out=self._list_cache_meta,
|
|
)
|
|
self._register_discovered_tools_if_needed()
|
|
|
|
def _register_discovered_tools_if_needed(self) -> None:
|
|
"""Publish freshly discovered tools for a registry-owned server if none are registered.
|
|
|
|
Initial registration normally happens in ``_discover_and_register_server``
|
|
after ``start()``. On reconnect, outage handling may clear ``_ready`` and
|
|
deregister stale tools; ownership via ``_servers`` authorizes publishing
|
|
before readiness is restored so a revival never comes back with zero
|
|
tools. A server retained after a recoverable initial failure is likewise
|
|
owned before its first session, which authorizes its first publication.
|
|
"""
|
|
if self._registered_tool_names:
|
|
return
|
|
if not self._ready.is_set():
|
|
with _core._lock:
|
|
if _core._servers.get(self.name) is not self:
|
|
return
|
|
self._registered_tool_names = _core._register_server_tools(self.name, self, self._config)
|
|
# A retained initial-failure server that just published tools has
|
|
# recovered: drop its stale connect error from status surfaces.
|
|
with _core._lock:
|
|
if _core._servers.get(self.name) is self:
|
|
_core._server_connect_errors.pop(self.name, None)
|