Files
hermes-agent/tools/computer_use/cua_backend_session.py
T

554 lines
29 KiB
Python

"""cua-driver MCP session plumbing: the asyncio bridge thread and the lazily-started,
self-healing ``_CuaDriverSession`` (MCP transport with a ``cua-driver call`` CLI fallback).
Driver resolution / policy helpers are looked up lazily through
``tools.computer_use.cua_backend`` so tests that patch them there keep working.
"""
from __future__ import annotations
import asyncio
import base64
import concurrent.futures
import contextlib
import json
import logging
import os
import threading
from typing import Any, Dict, List, Optional, Tuple
from tools.computer_use.cua_backend_parse import _extract_tool_result, _mcp_field
logger = logging.getLogger("tools.computer_use.cua_backend")
class _AsyncBridge:
"""Runs one asyncio loop on a daemon thread; marshals coroutines from the caller."""
def __init__(self) -> None:
self._loop: Optional[asyncio.AbstractEventLoop] = None
self._thread: Optional[threading.Thread] = None
self._ready = threading.Event()
def start(self) -> None:
if self._thread and self._thread.is_alive():
return
self._ready.clear()
def _run() -> None:
self._loop = asyncio.new_event_loop()
asyncio.set_event_loop(self._loop)
self._ready.set()
try:
self._loop.run_forever()
finally:
with contextlib.suppress(Exception):
self._loop.close()
self._thread = threading.Thread(target=_run, daemon=True, name="cua-driver-loop")
self._thread.start()
if not self._ready.wait(timeout=5.0):
raise RuntimeError("cua-driver asyncio bridge failed to start")
def run(self, coro, timeout: Optional[float] = 30.0) -> Any:
from agent.async_utils import safe_schedule_threadsafe
if not self._loop or not self._thread or not self._thread.is_alive():
if asyncio.iscoroutine(coro):
coro.close()
raise RuntimeError("cua-driver bridge not started")
fut = safe_schedule_threadsafe(coro, self._loop)
if fut is None:
raise RuntimeError("cua-driver bridge not started")
return fut.result(timeout=timeout)
def stop(self) -> None:
if self._loop and self._loop.is_running():
self._loop.call_soon_threadsafe(self._loop.stop)
if self._thread:
self._thread.join(timeout=2.0)
self._thread = self._loop = None
# Fail-closed messages for calls whose effect on the remote screen is unknown. The action
# MAY have landed, so it is never replayed; the caller decides after taking fresh state.
_UNKNOWN_OUTCOME_MESSAGES = {
"transport_outcome_unknown": (
"cua-driver transport failed during {name}; the action outcome is unknown, so Hermes "
"did not replay it. Take fresh state before deciding whether to act again."),
"timeout_outcome_unknown": (
"cua-driver MCP call {name} timed out; the action outcome is unknown and may still have "
"taken effect on the remote screen. The session has been marked suspect and will be "
"recreated before the next computer-use call. Take fresh state before deciding "
"whether to act again."),
}
def _outcome_unknown(name: str, exc: Exception, code: str) -> Dict[str, Any]:
"""Fail-closed ``isError`` result for *code* (see ``_UNKNOWN_OUTCOME_MESSAGES``)."""
message = _UNKNOWN_OUTCOME_MESSAGES[code].format(name=name)
structured = {"ok": False, "code": code, "message": message, "operation": name,
"next_step": "fresh_state", "detail": str(exc)}
return {"data": message, "images": [], "image_mime_types": [],
"structuredContent": structured, "isError": True}
def _tool_field(obj: Any, *names: str) -> Any:
"""``_mcp_field`` plus the ``model_extra`` fallback some MCP SDKs (Pydantic v2) forward custom fields via."""
value = _mcp_field(obj, names[0], names[-1])
if value is None:
value = (getattr(obj, "model_extra", None) or {}).get(names[-1])
return value
_CLI_ATTEMPTS = 4 # CLI fallback transport retries (backoff 0.5s doubling)
def _cli_run_json(cmd: List[str], env: Dict[str, str], name: str, timeout: float) -> Any:
"""Run ``cua-driver call`` with backoff until it prints JSON; return the parsed value.
"daemon is not running" is PERMANENT for this invocation (the CLI needs the machine-wide
daemon socket, which Linux installs typically never start) -> fail fast, no ~3.5s backoff."""
import subprocess as _subprocess
import time as _time
from tools.computer_use import cua_backend as _cb
backoff = 0.5
last_err = ""
for attempt in range(_CLI_ATTEMPTS):
try:
proc = _subprocess.run(
cmd, capture_output=True, text=True, encoding="utf-8", errors="replace",
timeout=max(15.0, timeout), creationflags=_cb.windows_hide_flags(), env=env)
except Exception as e: # pragma: no cover - subprocess spawn failure
raise RuntimeError(f"cua-driver CLI fallback for {name} failed to spawn: {e}") from e
out, err = (proc.stdout or "").strip(), proc.stderr or ""
last_err = out[:200] or err[:200]
if "daemon is not running" in out or "daemon is not running" in err:
raise RuntimeError(
f"cua-driver CLI fallback for {name} unavailable: the "
"machine-wide cua-driver daemon is not running (the "
"CLI transport requires it; the MCP runtime does not).")
start = min((i for i in (out.find("{"), out.find("[")) if i != -1), default=-1)
with contextlib.suppress(json.JSONDecodeError):
if start != -1:
return json.loads(out[start:])
# No JSON (EAGAIN warning / empty) — retry with backoff.
if attempt < _CLI_ATTEMPTS - 1:
logger.warning("cua-driver CLI fallback for %s got no JSON (attempt %d/%d); "
"retrying in %.1fs", name, attempt + 1, _CLI_ATTEMPTS, backoff)
_time.sleep(backoff)
backoff *= 2
raise RuntimeError(f"cua-driver CLI fallback for {name} returned no JSON after "
f"{_CLI_ATTEMPTS} attempts: {last_err}")
def _cli_result(parsed: Any, shot_file: Optional[str]) -> Dict[str, Any]:
"""Remap a ``cua-driver call`` JSON body into the ``_extract_tool_result`` shape."""
if not isinstance(parsed, dict):
return {"data": None, "images": [], "structuredContent": None, "isError": False}
# In-band logical failures with exit 0 must still fail closed.
is_error = parsed.get("isError") is True or parsed.get("is_error") is True
shot = parsed.get("screenshot_png_b64")
# Otherwise the screenshot was routed to a file (ours or the daemon's choice).
fpath = parsed.get("screenshot_file_path") or shot_file
if not shot and fpath and os.path.exists(fpath):
try:
with open(fpath, "rb") as fh:
shot = base64.b64encode(fh.read()).decode("ascii")
except Exception as e:
logger.debug("cua-driver CLI fallback: failed reading %s: %s", fpath, e)
data: Any = parsed.get("tree_markdown")
if data is not None and parsed.get("element_count") is not None:
data = f"{parsed['element_count']} elements\n{data}"
return {"data": data, "images": [shot] if shot else [], "structuredContent": parsed, "isError": is_error}
class _CuaDriverSession:
"""Holds the mcp ClientSession. Spawned lazily; re-entered on drop.
Lifecycle ownership: one long-running coroutine (`_lifecycle_coro`) opens the
stdio_client + ClientSession contexts, populates capabilities, sets `_ready_event`,
waits on `_shutdown_event`, then closes the contexts — enter and exit in the SAME
task, as anyio's cancel-scope invariant requires (each `bridge.run(coro)` is a NEW
task). Tool calls run in short-lived tasks touching only the session object.
"""
# Handshake calls issued BY start()/stop() — exempt from call_tool's auto-restart
# guard, or start() would recurse.
_LIFECYCLE_CALLS = frozenset({"start_session", "end_session"})
# Idempotent reads, safe to replay after a broken transport. Mutations stay out:
# a lost response does not prove they failed.
_TRANSPORT_REPLAY_SAFE_TOOLS = frozenset({
"get_cursor_position", "get_displays", "get_screen_size",
"get_window_state", "list_apps", "list_windows",
})
# A timed-out MCP session is wedged for later calls, so it is recreated before the
# next non-lifecycle call_tool. Class-level default: tests that bypass __init__ see healthy.
_timeout_suspect = False
def __init__(self, bridge: _AsyncBridge, embedded_daemon: Optional[Any] = None) -> None:
self._bridge, self._embedded_daemon = bridge, embedded_daemon
self._session = None
self._lock = threading.Lock()
self._started = False
# Per-tool capability-token sets from `tools/list` (read via supports_capability).
self._capabilities: Dict[str, set] = {}
# Raw input schemas are the source of truth for action properties: 0.9-era drivers
# advertise delivery_mode in inputSchema without the ``input.delivery_mode`` token.
self._tool_schemas: Dict[str, Dict[str, Any]] = {}
self._capability_version: str = ""
self._ready_event = threading.Event()
self._shutdown_event: Optional[asyncio.Event] = None # created on bridge loop
self._lifecycle_future = None # concurrent.futures.Future
self._setup_error: Optional[BaseException] = None
# Declared via start_session; revives an ended-session rejection non-re-entrantly.
self._declared_session_id: Optional[str] = None
self._transport_generation, self._transport_reset_callback = 0, None
def _require_started(self) -> None:
if not self._started:
raise RuntimeError("cua-driver session not started")
def _reset_capability_state(self) -> None:
self._capabilities, self._tool_schemas, self._capability_version = {}, {}, ""
async def _lifecycle_coro(self) -> None:
"""Owns the stdio MCP contexts: open, signal ready, block on shutdown, clean up —
all in one task (see class docstring)."""
import time as _time
from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client
from tools.computer_use import cua_backend as _cb
from tools.environments.local import _sanitize_subprocess_env
self._shutdown_event = asyncio.Event() # built on the loop's own thread
_t0 = _time.monotonic()
# Phase marker: the ready-timeout error reports HOW FAR a wedged startup got.
self._startup_phase = "binary-check"
try:
driver_cmd = _cb.resolve_cua_driver_cmd()
if not driver_cmd:
raise RuntimeError(_cb.cua_driver_install_hint())
self._startup_phase = "manifest-discovery"
daemon = self._embedded_daemon
if daemon is not None:
(command, args), child_env = daemon.proxy_invocation(), daemon.child_env()
else:
(command, args), child_env = _cb._resolve_mcp_invocation(driver_cmd), _cb.cua_driver_child_env()
_t_manifest = _time.monotonic()
# Telemetry policy first (default: disabled), then strip Hermes secrets.
params = StdioServerParameters(command=command, args=args,
env=_sanitize_subprocess_env(child_env))
async with stdio_client(params) as (read, write):
self._startup_phase = "mcp-initialize"
async with ClientSession(read, write) as session:
await session.initialize()
_t_init = _time.monotonic()
# Capabilities BEFORE exposing the session: the first call sees them.
self._startup_phase = "capability-discovery"
await self._populate_capabilities(session)
self._session = session
self._startup_phase = "ready"
self._ready_event.set()
logger.info("cua-driver session ready in %.1fs (manifest=%.1fs, mcp_init=%.1fs)",
_time.monotonic() - _t0, _t_manifest - _t0, _t_init - _t_manifest)
await self._shutdown_event.wait()
except BaseException as e:
# Ordinary errors and anyio CancelledError alike: start() surfaces this.
self._setup_error = e
self._ready_event.set()
raise
finally:
self._session = None
# A session that dies for ANY reason must be re-enterable: the next call
# sees _started False and rebuilds. Atomic bool write — stop() may hold _lock.
self._started = False
async def _populate_capabilities(self, session: Any) -> None:
"""Cache per-tool capability sets, input schemas and capability_version from
tools/list. Soft prerequisite: on failure the map stays empty (capability False)."""
self._reset_capability_state()
try:
tools_list = await session.list_tools()
for tool in getattr(tools_list, "tools", []) or []:
tool_name = getattr(tool, "name", None)
if not isinstance(tool_name, str):
continue
caps = _tool_field(tool, "capabilities")
self._capabilities[tool_name] = (
{c for c in caps if isinstance(c, str)} if isinstance(caps, list) else set())
schema = _tool_field(tool, "input_schema", "inputSchema")
self._tool_schemas[tool_name] = dict(schema) if isinstance(schema, dict) else {}
# capability_version is a sibling of `tools` in tools/list (NOT in initialize).
cv = _tool_field(tools_list, "capability_version")
if isinstance(cv, str):
self._capability_version = cv
except Exception as e:
logger.debug("cua-driver tools/list capability discovery failed: %s", e)
def start(self) -> None:
with self._lock:
if self._started:
return
self._bridge.start()
self._start_lifecycle_locked()
self._started = True
def _start_lifecycle_locked(self) -> None:
"""Spawn the lifecycle owner and wait for ready. Caller holds self._lock."""
self._ready_event = threading.Event()
self._setup_error = self._shutdown_event = None
# The future tracks the WHOLE lifecycle; readiness is signalled via _ready_event.
loop = self._bridge._loop
if loop is None:
raise RuntimeError("cua-driver bridge not started")
self._lifecycle_future = asyncio.run_coroutine_threadsafe(self._lifecycle_coro(), loop)
if not self._ready_event.wait(timeout=30.0):
self._signal_shutdown_locked()
phase = getattr(self, "_startup_phase", "unknown")
from hermes_constants import display_hermes_home
raise RuntimeError(
f"cua-driver session never reached ready (timeout 30s; stuck in phase: {phase}). "
"Run `hermes computer-use doctor` and check "
f"{display_hermes_home()}/logs/agent.log for the phase timings.")
if self._setup_error is not None:
raise RuntimeError(f"cua-driver session setup failed: {self._setup_error}") from self._setup_error
self._transport_generation += 1
if self._transport_generation > 1:
self._notify_transport_reset()
def stop(self) -> None:
with self._lock:
if not self._started:
return
self._started = False
self._stop_lifecycle_locked()
def set_transport_reset_callback(self, callback: Any) -> None:
"""Register a synchronous cache invalidation hook for transport swaps."""
self._transport_reset_callback = callback
def _notify_transport_reset(self) -> None:
callback = getattr(self, "_transport_reset_callback", None)
try:
if callback is not None:
callback()
except Exception as exc:
logger.debug("cua-driver transport reset callback failed: %s", exc)
def _stop_lifecycle_locked(self) -> None:
self._signal_shutdown_locked()
fut, self._lifecycle_future = self._lifecycle_future, None
try:
if fut is not None:
fut.result(timeout=5.0)
except concurrent.futures.TimeoutError:
logger.warning("cua-driver session shutdown timed out (5s)")
except Exception as e:
logger.warning("cua-driver shutdown error: %s", e)
def _signal_shutdown_locked(self) -> None:
"""Set the asyncio shutdown event from the caller's thread."""
loop, event = self._bridge._loop, self._shutdown_event
if loop is not None and event is not None and loop.is_running():
with contextlib.suppress(RuntimeError): # loop closed — nothing to signal
loop.call_soon_threadsafe(event.set)
async def _call_tool_async(self, name: str, args: Dict[str, Any]) -> Dict[str, Any]:
return _extract_tool_result(await self._session.call_tool(name, args))
def _run_call(self, name: str, args: Dict[str, Any], timeout: float) -> Dict[str, Any]:
return self._bridge.run(self._call_tool_async(name, args), timeout=timeout)
# ── Capability detection ─────────────────────────────────────────
def supports_capability(self, capability: str, tool: Optional[str] = None) -> bool:
"""Driver advertises *capability* for *tool* (or ANY tool). False before start."""
caps = [self._capabilities.get(tool, set())] if tool is not None else self._capabilities.values()
return any(capability in c for c in caps)
def _has_tool(self, name: str) -> bool:
"""``tools/list`` advertised *name*. Routes capture() (PNG capture moved into
``get_window_state``). False before discovery — callers treat that as "unknown"."""
return name in self._capabilities
def supports_input_property(self, tool: str, property_name: str) -> bool:
"""Live tools/list schema accepts *property_name* (fails closed; no version guessing)."""
schema = getattr(self, "_tool_schemas", {}).get(tool, {})
properties = schema.get("properties") if isinstance(schema, dict) else None
return isinstance(properties, dict) and property_name in properties
@property
def capabilities_discovered(self) -> bool:
"""tools/list populated the map; when False ``_has_tool`` is untrustworthy."""
return bool(self._capabilities)
@property
def capability_version(self) -> str:
"""Driver-advertised capability vocabulary version ("" on old builds)."""
return self._capability_version
# ── Error classification ─────────────────────────────────────────
@staticmethod
def _logical_error_text(result: Dict[str, Any]) -> str:
"""Flatten a logical MCP error into text for narrow classification."""
chunks: List[str] = []
for value in (result.get("data"), result.get("structuredContent")):
if value is None:
continue
try:
chunks.append(value if isinstance(value, str) else json.dumps(value, sort_keys=True))
except (TypeError, ValueError):
chunks.append(str(value))
return "\n".join(chunks)
@classmethod
def _is_ended_session_result(cls, result: Any) -> bool:
"""Recognise cua-driver's explicit recoverable ended-session result."""
if not isinstance(result, dict) or result.get("isError") is not True:
return False
message = cls._logical_error_text(result).lower()
return ("session" in message and "start_session" in message
and ("has ended" in message or "session ended" in message))
@staticmethod
def _is_closed_session_error(exc: Exception) -> bool:
"""True for MCP/stdio failures that are recoverable by reconnecting."""
name, module = exc.__class__.__name__, getattr(exc.__class__, "__module__", "")
return (name in {"ClosedResourceError", "BrokenResourceError", "EndOfStream"}
or (module.startswith("anyio") and "Resource" in name)
or isinstance(exc, (BrokenPipeError, EOFError)))
@staticmethod
def _is_transient_daemon_error(exc: Exception) -> bool:
"""Daemon-proxy EAGAIN congestion: on macOS the ``cua-driver mcp`` bridge uses a
non-blocking unix socket and heavy ops (``get_window_state``) fail with ``os error
35`` when its buffer is full. A retry succeeds, so back off / fall back instead
of surfacing an empty 0x0 capture."""
msg = str(exc)
return any(needle in msg for needle in ("Resource temporarily unavailable", "os error 35",
"daemon transport error", "daemon proxy"))
# ── Recovery ─────────────────────────────────────────────────────
def _revive_declared_session_once(self, name: str, args: Dict[str, Any],
first_result: Dict[str, Any], timeout: float) -> Dict[str, Any]:
"""Revive the stable session, replay the rejected call once; a 2nd rejection surfaces as-is."""
session_id = self._declared_session_id
if not session_id or name in self._LIFECYCLE_CALLS:
return first_result
logger.warning("cua-driver session %s ended during %s; reviving and retrying once", session_id, name)
if not self._redeclare_session(timeout, "cua-driver session %s could not be revived: %s"):
return first_result
return self._run_call(name, args, timeout)
def _redeclare_session(self, timeout: float, failure_msg: str) -> bool:
"""start_session with the declared id; log *failure_msg* and return False on rejection."""
session_id = self._declared_session_id
result = self._run_call("start_session", {"session": session_id}, timeout)
if result.get("isError") is True:
logger.warning(failure_msg, session_id, self._logical_error_text(result))
return False
return True
def _restore_declared_session_after_transport_reset(self, timeout: float) -> None:
"""Re-attach the public label inside a replacement private lifecycle."""
if getattr(self, "_declared_session_id", None):
self._redeclare_session(timeout, "cua-driver public session label %s could not be restored: %s")
def _restart_session_locked(self) -> None:
"""Recreate the MCP session after the transport closed. Caller holds self._lock."""
try:
if self._started:
self._stop_lifecycle_locked()
except Exception as e:
logger.debug("cua-driver session cleanup before reconnect failed: %s", e)
self._started = False
self._reset_capability_state() # repopulated from scratch by the next start
self._start_lifecycle_locked()
self._started = True
def _recreate_session(self, timeout: float, *, clear_timeout_suspect: bool = False) -> None:
"""Restart the private lifecycle, then re-attach the declared public label."""
with self._lock:
self._restart_session_locked()
if clear_timeout_suspect:
self._timeout_suspect = False
self._restore_declared_session_after_transport_reset(timeout)
def _cli_command(self, name: str, args: Dict[str, Any]) -> Tuple[List[str], Dict[str, str], Optional[str]]:
"""Build ``(cmd, child_env, shot_file)`` for the CLI fallback. ``get_window_state`` routes
its screenshot to a temp file (``screenshot_out_file``) so the daemon returns a tiny JSON
body, not the multi-megabyte base64 blob that congests the socket; ``_cli_result`` reads it."""
import tempfile as _tempfile
from tools.computer_use import cua_backend as _cb
call_args = dict(args)
shot_file: Optional[str] = None
if name == "get_window_state" and "screenshot_out_file" not in call_args:
fd, shot_file = _tempfile.mkstemp(prefix="cua_shot_", suffix=".png")
os.close(fd)
call_args["screenshot_out_file"] = shot_file
driver_command = _cb.resolve_cua_driver_cmd()
if not driver_command:
raise RuntimeError(_cb.cua_driver_install_hint())
child_env, socket_args = _cb.cua_driver_child_env(), []
daemon = getattr(self, "_embedded_daemon", None)
if daemon is not None:
driver_command, child_env = daemon.proxy_invocation()[0], daemon.child_env()
socket_args = ["--socket", daemon.socket_path]
return [driver_command, "call", name, json.dumps(call_args), *socket_args], child_env, shot_file
def _call_tool_via_cli(self, name: str, args: Dict[str, Any], timeout: float) -> Dict[str, Any]:
"""Fallback transport: ``cua-driver call <tool> <json>`` subprocess. The MCP stdio bridge
can persistently fail heavy calls (``get_window_state``) with EAGAIN while the plain CLI,
on its own daemon socket, keeps working. Output is remapped to the ``_extract_tool_result`` shape."""
from tools.environments.local import _sanitize_subprocess_env
cmd, child_env, shot_file = self._cli_command(name, args)
try:
parsed = _cli_run_json(cmd, _sanitize_subprocess_env(child_env), name, timeout)
return _cli_result(parsed, shot_file)
finally:
if shot_file and os.path.exists(shot_file):
with contextlib.suppress(OSError):
os.remove(shot_file)
def call_tool(self, name: str, args: Dict[str, Any], timeout: float = 30.0) -> Dict[str, Any]:
# A prior MCP timeout marks the session suspect (possibly wedged): recreate it
# so one timeout never poisons the run. Healthy sessions are never restarted here.
if self._timeout_suspect and name not in self._LIFECYCLE_CALLS:
logger.warning("cua-driver session suspect after earlier MCP timeout; recreating before %s", name)
self._recreate_session(timeout, clear_timeout_suspect=True)
# A prior session may have died (MCP drop / driver crash) and reset _started.
if not self._started and name not in self._LIFECYCLE_CALLS:
logger.warning("cua-driver session not active on %s; (re)starting before call", name)
self.start()
self._restore_declared_session_after_transport_reset(timeout)
self._require_started()
try:
result = self._run_call(name, args, timeout)
except Exception as e:
if isinstance(e, concurrent.futures.TimeoutError):
# Fail closed: the action may have landed, so never replay it.
self._timeout_suspect = True
logger.warning("cua-driver MCP timed out on %s; marking session suspect "
"for recreation before the next call", name)
return _outcome_unknown(name, e, "timeout_outcome_unknown")
if self._is_transient_daemon_error(e):
if name not in self._TRANSPORT_REPLAY_SAFE_TOOLS:
self._notify_transport_reset()
return _outcome_unknown(name, e, "transport_outcome_unknown")
logger.warning("cua-driver MCP transport failed on %s (%s); "
"falling back to CLI transport", name, e)
return self._call_tool_via_cli(name, args, timeout)
if not self._is_closed_session_error(e):
raise
logger.warning("cua-driver MCP session closed during %s; reconnecting once", name)
self._recreate_session(timeout)
if name not in self._TRANSPORT_REPLAY_SAFE_TOOLS:
return _outcome_unknown(name, e, "transport_outcome_unknown")
result = self._run_call(name, args, timeout)
# Remember only a SUCCESSFULLY declared identity: no stale recovery state.
declared_id = args.get("session")
if (name == "start_session" and result.get("isError") is not True
and isinstance(declared_id, str) and declared_id):
self._declared_session_id = declared_id
if self._is_ended_session_result(result):
result = self._revive_declared_session_once(name, args, result, timeout)
if (name == "end_session" and result.get("isError") is not True
and args.get("session") == self._declared_session_id):
self._declared_session_id = None
return result