Files
hermes-agent/tools/computer_use/cua_backend.py
Jeff J Hunter 65625dfe87 fix(computer_use): attach element_token when the driver schema accepts it
cua-driver 0.21 refuses a bare element_index:

    click: bare element_index is not accepted; pass element_token,
    or snapshot_id together with element_index

_maybe_attach_element_token gated solely on the trycua/cua#1961 capability
vocabulary. 0.21 stopped publishing per-tool capability sets — every tool
reports an empty set — while still accepting element_token in its input
schema. The gate therefore fails closed on 0.21.x and we send the bare
index, so the driver rejects the call.

The effect is total: every element-targeted click is refused, leaving
agents with only blind pixel coordinates. Observed against cua-driver
0.21.0 on X11, where a capture returned 762 elements with 762 tokens
cached and every subsequent click still failed with snapshot_id_required.

Check the live input schema first — supports_input_property() already
exists for exactly this, and its docstring notes it "deliberately inspects
tools/list rather than ... requiring a capability token the driver never
shipped". The capability check is retained as a fallback so drivers that
did ship the vocabulary are unaffected.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-09-14 17:34:31 -07:00

419 lines
25 KiB
Python

"""Cua-driver backend (macOS, Windows, Linux): MCP over stdio to `cua-driver`. The async `mcp` SDK runs on a
background loop (``cua_backend_session``); the same tool surface works on all three platforms, and per-host gaps
(no DISPLAY, missing AT-SPI, TCC) surface via `hermes computer-use doctor` instead of failing silently. Install
with `hermes computer-use install`. The macOS path uses private SkyLight SPIs that can break on OS updates.
Siblings: ``cua_backend_driver`` (binary/contract/update), ``cua_backend_capture`` + ``cua_backend_input``
(mixins), ``cua_backend_parse``, ``cua_backend_session`` (bridge + session + CLI fallback), ``cua_backend_daemon``
(private daemon + macOS app identity). Siblings look this module's config/policy helpers up lazily."""
from __future__ import annotations
import contextlib
import importlib
import logging
import os
import subprocess
import sys
import threading
import uuid
from typing import Any, Dict, List, Optional
from hermes_cli._subprocess_compat import windows_hide_flags
from tools.computer_use.backend import ActionResult, ComputerUseBackend
from tools.computer_use.cua_backend_capture import _CaptureMixin
from tools.computer_use.cua_backend_daemon import _EmbeddedCuaDaemon
from tools.computer_use.cua_backend_driver import (
_CUA_DRIVER_CMD_ENV, cua_driver_binary_available, cua_driver_runtime_contract_status, cua_driver_update_nudge,
resolve_cua_driver_cmd)
from tools.computer_use.cua_backend_input import _InputMixin
from tools.computer_use.cua_backend_parse import _action_result_from
from tools.computer_use.cua_backend_session import _AsyncBridge, _CuaDriverSession
logger = logging.getLogger(__name__)
# cua-driver's anonymous PostHog telemetry gate ("0" disables; absent => ON upstream).
_CUA_TELEMETRY_ENV_VAR = "CUA_DRIVER_RS_TELEMETRY_ENABLED"
_CUA_NATIVE_WAYLAND_ENV_VAR = "CUA_DRIVER_RS_ENABLE_WAYLAND"
def _computer_use_cfg() -> Dict[str, Any]:
"""The ``computer_use`` config block, or ``{}`` when config is unreadable."""
with contextlib.suppress(Exception):
from hermes_cli.config import load_config
return (load_config() or {}).get("computer_use") or {}
return {}
def _cua_no_overlay() -> bool:
"""Pass ``--no-overlay``? ``computer_use.no_overlay`` overrides; else off on macOS (cursor-overlay redraw
loop can peg a core after a session), headless Linux / WSL2 / containers, and Linux X11 (the overlay is a
fullscreen always-on-top all-workspaces window with no compositor-owned lifecycle, so an unclean session
end can leave it wedged over every app); on for Windows and Linux Wayland (compositor owns the surface).
Explicit ``True`` / ``False`` overrides auto-detection. See #28152, #47032.
"""
val = _computer_use_cfg().get("no_overlay")
if val is not None or sys.platform != "linux":
return bool(val) if val is not None else sys.platform == "darwin"
wsl = False
with contextlib.suppress(Exception), open("/proc/version", encoding="utf-8") as f:
wsl = "microsoft" in f.read().lower()
return wsl or not os.environ.get("DISPLAY") or (
# Linux/X11: the cursor overlay is a fullscreen, always-on-top, all-workspaces X11 window
# (save-unders path). An unclean session end (agent interrupted mid-capture, stale target window)
# can leave it stuck above every app on every workspace, wedging desktop input until the app
# restarts — the same failure class as the HUD window on Mutter/X11 (#83473). There is no
# compositor-owned surface to tear down with the client connection, so default the overlay off on
# X11 too; set computer_use.no_overlay: false to keep the cursor. Wayland keeps it: the compositor
# owns the overlay surface lifecycle there.
os.environ.get("XDG_SESSION_TYPE") != "wayland" and not os.environ.get("WAYLAND_DISPLAY"))
def _cua_telemetry_disabled() -> bool:
"""True unless ``computer_use.cua_telemetry`` opts in (unreadable config fails SAFE toward disabling)."""
return not bool(_computer_use_cfg().get("cua_telemetry", False))
def _cua_configured_permission_mode() -> str:
"""``computer_use.permission_mode``: ``standard`` (default) or ``bounded``; unknown values fall closed to
``standard``. ``unrestricted`` is deliberately NOT a config value — it stays tied to the per-session YOLO
toggle so a stale config line can never silently bypass approvals."""
raw = str(_computer_use_cfg().get("permission_mode", "standard") or "").strip().lower()
return "bounded" if raw == "bounded" else "standard"
def _manifest_is_mode_independent(path: str) -> bool:
"""True when this manifest may accompany any permission mode: v1/v2 declare ``mode: bounded`` and abort
startup under an unrestricted runtime; v3 has no mode and is the ceiling the driver accepts alongside any
mode. Unreadable / unparseable -> False (forwarding one would turn a working session into a hard startup
failure; bounded forwards unconditionally anyway)."""
try:
import yaml
with open(path, "r", encoding="utf-8") as handle:
parsed = yaml.safe_load(handle)
except Exception:
logger.debug("could not read capability manifest %s", path, exc_info=True)
return False
version = parsed.get("version") if isinstance(parsed, dict) else None
return isinstance(version, int) and not isinstance(version, bool) and version >= 3
def _computer_use_max_image_dimension() -> Optional[int]:
"""``computer_use.max_image_dimension`` longest-edge cap (default 1456 = aux-vision downscale); ``0``/negative -> None."""
try:
dim = int(_computer_use_cfg().get("max_image_dimension", 1456))
except (TypeError, ValueError):
dim = 1456
return dim if dim > 0 else None
def cua_driver_child_env(base_env: Optional[Dict[str, str]] = None) -> Dict[str, str]:
"""Env for spawning cua-driver: ``base_env`` (default ``os.environ``) plus ``CUA_DRIVER_RS_TELEMETRY_ENABLED=0``
unless the user opted in, plus the native-Wayland bridge (``computer_use.native_wayland`` config opt-in, only when
the child has a Wayland display). Used by every spawn site (MCP, status, doctor, install) so CLI and gateway
runtimes share one policy."""
env = dict(os.environ if base_env is None else base_env)
if _cua_telemetry_disabled():
env[_CUA_TELEMETRY_ENV_VAR] = "0"
if sys.platform == "linux" and env.get("WAYLAND_DISPLAY") and bool(_computer_use_cfg().get("native_wayland", False)):
env[_CUA_NATIVE_WAYLAND_ENV_VAR] = "1"
return env
def sanitized_cua_driver_env() -> Dict[str, str]:
"""``cua_driver_child_env()`` with Hermes provider secrets stripped — cua-driver is a third-party binary and must
never inherit API keys. Falls back to the unsanitized telemetry env if the sanitizer can't import."""
env = cua_driver_child_env()
with contextlib.suppress(Exception):
# cua-driver is a third-party binary — never hand it provider API keys via inherited env (same
# policy as the manifest probe and MCP spawn; #53503/#55709/#58889 lineage).
from tools.environments.local import _sanitize_subprocess_env
return _sanitize_subprocess_env(env)
return env
def _run_quiet(argv: List[str], *, timeout: float, swallow: Any = (), **kw: Any) -> Any:
"""``subprocess.run`` for short probe verbs: text mode, stdin=DEVNULL unless overridden (older drivers fall into a
stdin-reading mode on unknown verbs; EOF makes them exit fast instead of blocking until the timeout), output
captured unless the caller redirects it. Exceptions in ``swallow`` return None; others raise."""
kw.setdefault("stdin", subprocess.DEVNULL)
kw.setdefault("encoding", "utf-8")
kw.setdefault("errors", "replace")
"stdout" in kw or kw.setdefault("capture_output", True)
try:
return subprocess.run(argv, text=True, timeout=timeout, stdin=kw.pop("stdin"), encoding=kw.pop("encoding"),
errors=kw.pop("errors"), **kw)
except swallow:
return None
def _run_driver(driver_cmd: str, *args: str, timeout: float, swallow: Any = ()) -> Any:
"""Run a short cua-driver verb with the sanitized env and hidden window."""
return _run_quiet([driver_cmd, *args], timeout=timeout, swallow=swallow, encoding="utf-8",
errors="replace", creationflags=windows_hide_flags(), env=sanitized_cua_driver_env())
def _linux_session_locked() -> Optional[bool]:
"""Is the graphical session locked? (Linux; best-effort.) A locked KDE/GNOME session freezes renderers and
half-disables the AX tree, so discovery legitimately returns nothing — which otherwise reads as a driver bug.
True/False when loginctl answers, None when unavailable (non-Linux, no systemd-logind, probe failure)."""
# Auto-detect: macOS overlay can peg a core indefinitely after a computer_use session (#47032). Prefer
# off until the driver teardown is solid; set computer_use.no_overlay: false to keep the cursor.
if sys.platform != "linux":
return None
try:
proc = _run_quiet(["loginctl", "list-sessions", "--no-legend"], timeout=2.0)
seats = [line.split()[0] for line in proc.stdout.splitlines() if len(line.split()) >= 2 and "seat" in line]
if proc.returncode != 0 or not seats:
return None
return not any("LockedHint=no" in _run_quiet(["loginctl", "show-session", s, "-p", "LockedHint"], timeout=2.0).stdout
for s in seats)
except Exception:
return None
def _empty_discovery_reason() -> str:
"""One-line diagnosis for 'window discovery found nothing'."""
if _linux_session_locked() is True:
return ("the desktop session is LOCKED (loginctl LockedHint=yes) — unlock the screen; "
"a locked compositor hides windows and freezes app renderers")
if sys.platform == "linux" and not os.environ.get("DISPLAY"):
return "no DISPLAY is set — X11/XWayland is not reachable from this process"
if sys.platform == "darwin": # headless Mac / asleep panel: ScreenCaptureKit has 0 shareable displays while TCC looks fine
return ("window discovery returned no windows; on macOS this usually means no shareable display (headless Mac or "
"panel asleep) — wake the display or attach a monitor/HDMI dummy, then run `hermes computer-use doctor`")
return "window discovery returned no windows; run `hermes computer-use doctor` (display reachability, AX capability)"
_update_checked = False
# One auto-repair attempt per process: when the runtime-contract gate fails for something a reinstall fixes
# (old version, missing manifest verbs) run the standard install path once instead of telling the user to.
# Guarded so a failing installer can't loop — the second start() goes straight to the error.
_contract_repair_attempted = False
def _maybe_repair_runtime_contract(contract: Dict[str, Any]) -> Dict[str, Any]:
"""Try one automatic driver repair; return the post-repair contract (or the original when no repair was
attempted / it failed). Never raises. An explicit ``HERMES_CUA_DRIVER_CMD`` override is authoritative even
when broken, and a missing binary means installation was never requested."""
global _contract_repair_attempted
if contract.get("ready") or _contract_repair_attempted or os.environ.get(_CUA_DRIVER_CMD_ENV, "").strip() or not contract.get("binary"):
return contract
_contract_repair_attempted = True
logger.info("computer_use: installed cua-driver is not usable (%s); attempting automatic repair",
contract.get("reason") or "runtime contract is incomplete")
try:
from hermes_cli.tools_config import install_cua_driver
repaired = install_cua_driver(upgrade=False, show_installer_progress=False)
except Exception as exc:
logger.warning("computer_use: automatic cua-driver repair failed: %s", exc)
return contract
with contextlib.suppress(Exception):
return cua_driver_runtime_contract_status() if repaired else contract
return contract
def _maybe_nudge_update() -> None:
"""Emit an update nudge at most once per process, off-thread so the (cached, ~20h) GitHub poll never blocks
the first computer_use action."""
global _update_checked
if _update_checked:
return
_update_checked = True
def _run() -> None:
with contextlib.suppress(Exception):
msg = cua_driver_update_nudge()
msg and logger.info("computer_use: %s", msg)
threading.Thread(target=_run, name="cua-driver-update-check", daemon=True).start()
class CuaDriverBackend(_CaptureMixin, _InputMixin, ComputerUseBackend):
"""Default computer-use backend. Cross-platform via cua-driver MCP."""
def __init__(self, permission_mode: str = "standard") -> None:
if permission_mode not in {"standard", "bounded", "unrestricted"}:
raise ValueError(f"unsupported cua-driver permission mode: {permission_mode}")
self.permission_mode = permission_mode
self._embedded_daemon: Optional[_EmbeddedCuaDaemon] = None
if permission_mode != "standard":
# Manifest: mandatory for bounded (the daemon validates it), optional for unrestricted where it still
# caps what an approval-bypassed run may touch.
raw = _computer_use_cfg().get("capability_manifest")
self._embedded_daemon = _EmbeddedCuaDaemon(
resolve_cua_driver_cmd() or "", permission_mode,
capability_manifest=raw.strip() if isinstance(raw, str) and raw.strip() else None)
self._bridge = _AsyncBridge()
self._session = _CuaDriverSession(self._bridge, self._embedded_daemon)
# Sticky target (set by capture()/focus_app(), used by actions): `_active_pid`, `_active_window_id`, `_last_app`,
# `_last_target` (exact identity for capture_after — Linux app names may be generic, e.g. several unrelated Qt
# windows all say Qt6Application), `_snapshot_tokens` (element_index -> element_token, attached to actions so
# cua-driver reports "stale" instead of silently re-resolving).
self._clear_active_target()
# Public session label (one per Hermes run) sent as `session` on every call: owns the cursor color and
# gives config/recording state a stable owner across transport restarts. Part of the 0.20 runtime contract.
self._session_id: str = f"hermes-{uuid.uuid4().hex[:12]}"
self._session.set_transport_reset_callback(self._handle_transport_reset)
def _handle_transport_reset(self) -> None:
"""Invalidate every capability minted by the replaced transport."""
self._clear_active_target()
def start(self) -> None:
contract = cua_driver_runtime_contract_status()
if not contract.get("ready"):
contract = _maybe_repair_runtime_contract(contract)
if not contract.get("ready"):
raise RuntimeError(f"cua-driver is not ready: {contract.get('reason') or 'runtime contract is incomplete'}. "
+ ("Update the binary selected by HERMES_CUA_DRIVER_CMD or remove that override."
if os.environ.get(_CUA_DRIVER_CMD_ENV, "").strip() else "Run `hermes computer-use install` to repair it."))
_maybe_nudge_update()
# `mcp` is an optional extra: lazy-install on first use (gated by `security.allow_lazy_installs`); failure
# raises FeatureUnavailable with the exact `uv pip install` hint.
from tools.lazy_deps import ensure as _lazy_ensure
_lazy_ensure("tool.computer_use", prompt=False)
importlib.invalidate_caches() # a just-installed package may not be importable yet
with contextlib.ExitStack() as rollback: # a failed start stops the private daemon, then re-raises
if self._embedded_daemon is not None:
rollback.callback(self._embedded_daemon.stop) and self._embedded_daemon.start()
self._session.start()
rollback.pop_all()
# Declare this run's identity. Non-fatal: cua-driver accepts anonymous calls (cursor won't render), so degrade.
self._best_effort("start_session failed (continuing anonymous)",
self._session.call_tool, "start_session", {"session": self._session_id})
# Post-handshake tuning guards on `_started`: before the handshake flips it, call_tool would re-enter
# session.start() (stubbed start() recurses).
if self._session._started:
max_dim = _computer_use_max_image_dimension()
if max_dim: # smaller screenshots cost less over the daemon socket and per turn
self._best_effort("set_config(max_image_dimension) failed",
self.set_config, max_image_dimension=max_dim)
if _cua_no_overlay(): # belt-and-suspenders when --no-overlay is unsupported or ignored
self._best_effort("set_agent_cursor_enabled failed",
self.set_agent_cursor_enabled, False, cursor_id=self._session_id)
def stop(self) -> None:
# Best-effort end_session so the driver cleans per-session state (cursor overlay, recording ownership,
# config overrides); the connection drop below releases daemon-side state regardless.
if self._session._started:
self._best_effort("end_session failed (continuing teardown)",
self._session.call_tool, "end_session", {"session": self._session_id})
with contextlib.ExitStack() as teardown: # every step runs even if one raised (LIFO: session, bridge, daemon)
self._embedded_daemon is None or teardown.callback(self._embedded_daemon.stop)
teardown.callback(self._bridge.stop)
teardown.callback(self._session.stop)
@staticmethod
def _best_effort(what: str, fn, *args: Any, **kwargs: Any) -> None:
"""Run a non-fatal driver call, logging (debug) instead of raising."""
try:
fn(*args, **kwargs)
except Exception as e:
logger.debug("cua-driver %s: %s", what, e)
def is_available(self) -> bool:
return sys.platform in ("darwin", "win32", "linux") and cua_driver_binary_available() # other Unix-likes untested E2E
def _clear_active_target(self) -> None:
"""Forget a capture/focus target so a failed lookup cannot misroute input."""
self._active_pid = self._active_window_id = self._last_app = self._last_target = None
# Surface 6 of NousResearch/hermes-agent#47072: per-snapshot `element_index -> element_token` map
# populated on capture(). Action tools (click/scroll/set_value/...) attach the matching token
# alongside `element_index` so cua-driver detects "stale" explicitly instead of silently
# re-resolving to a different element. Cleared whenever a fresh capture overwrites the snapshot
# context.
self._snapshot_tokens: Dict[int, str] = {}
def _set_active_target(self, target: Dict[str, Any]) -> None:
self._active_pid = target["pid"]
self._active_window_id = target["window_id"]
self._snapshot_tokens = {} # prior snapshot's tokens: disarm before any capture so an exception can't pair them
self._last_target = {"pid": self._active_pid, "window_id": self._active_window_id}
def launch_app(self, *, bundle_id: Optional[str] = None, name: Optional[str] = None,
urls: Optional[List[str]] = None, additional_arguments: Optional[List[str]] = None,
creates_new_application_instance: bool = False) -> Dict[str, Any]:
"""Idempotent launch returning ``{pid, bundle_id, name, windows[]}``. ``creates_new_application_instance=True``
forces a fresh instance so concurrent runs touching the same app get isolated windows."""
if not bundle_id and not name:
raise ValueError("launch_app requires either bundle_id or name")
args: Dict[str, Any] = {"session": self._session_id, **{k: v for k, v in (
("bundle_id", bundle_id), ("name", name), ("urls", urls and list(urls)),
("additional_arguments", additional_arguments and list(additional_arguments)),
("creates_new_application_instance", creates_new_application_instance or None)) if v}}
out = self._session.call_tool("launch_app", args)
return out["structuredContent"] or {"data": out["data"]}
def bring_to_front(self, *, pid: int, window_id: Optional[int] = None) -> ActionResult:
"""Activate a window so subsequent foreground-dispatched input lands on it."""
args: Dict[str, Any] = {"pid": int(pid), **({} if window_id is None else {"window_id": int(window_id)})}
# Strict live schema with no session property: a standalone native focus op, not a session-scoped input action.
return self._action("bring_to_front", args, inject_session=False)
def set_agent_cursor_enabled(self, enabled: bool, *, cursor_id: Optional[str] = None) -> ActionResult:
"""Toggle the agent cursor overlay's visibility for this run."""
return self._action("set_agent_cursor_enabled",
{"enabled": bool(enabled), **({"cursor_id": cursor_id} if cursor_id else {})})
def set_config(self, **config) -> ActionResult:
"""Set cua-driver config keys (e.g. ``max_image_dimension``); unknown keys pass through — cua-driver validates."""
return self._action("set_config", dict(config))
def call_tool(self, name: str, args: Optional[Dict[str, Any]] = None, *, timeout: float = 30.0) -> Dict[str, Any]:
"""Generic escape hatch: call any cua-driver MCP tool by name. ``session`` is injected via setdefault, so
this is the supported path for tools the wrapper does not type-wrap (preferred over ``self._session.call_tool``)."""
payload = dict(args) if args else {}
payload.setdefault("session", self._session_id)
return self._session.call_tool(name, payload, timeout=timeout)
def _action(self, name: str, args: Dict[str, Any], *, inject_session: bool = True) -> ActionResult:
# Attach the snapshot's `element_token` to an `element_index` call so a superseded snapshot yields an explicit
# 'stale' error. Two ways to establish support, the live input schema first: cua-driver 0.21+ stopped
# publishing per-tool `capabilities[]` while still accepting `element_token` in its schema, and it REFUSES a
# bare `element_index` (`snapshot_id_required`) — gating on the capability alone broke EVERY element click and
# left only pixel clicks working. The capability check stays so older drivers that shipped the vocabulary keep
# working; drivers advertising neither (`additionalProperties: false`) must never see the property.
idx = args.get("element_index")
token = self._snapshot_tokens.get(idx) if isinstance(idx, int) else None
if token and (self._session.supports_input_property(name, "element_token")
or self._session.supports_capability("accessibility.element_tokens", tool=name)):
args["element_token"] = token
if inject_session: # setdefault preserves any explicit session a caller already supplied
args.setdefault("session", self._session_id)
try:
out = self._session.call_tool(name, args)
except Exception as e:
logger.exception("cua-driver %s call failed", name)
return ActionResult(ok=False, action=name, message=f"cua-driver error: {e}")
data = out["data"]
structured = out.get("structuredContent") or {}
message = (str(data.get("message", "")) if isinstance(data, dict) else data if isinstance(data, str) else "") \
or (str(structured.get("message", "")) if isinstance(structured, dict) else "")
# Merge data + structuredContent into meta, structured winning on overlap (canonical verdict surface).
meta = {k: v for part in (data, structured) if isinstance(part, dict) for k, v in part.items()}
return _action_result_from(name, not out["isError"], message, meta, structured,
requested_delivery=args.get("delivery_mode"))
# ---- BEGIN PLUGIN-COMPAT (revert-scheduled; see COMPAT_MANIFEST.md) ----
# Names external plugins imported from this module before the Sep 2026 decomposition.
# Internal code MUST NOT use these (scripts/check_compat_pointers.py fails CI if it does).
# The whole block is removed by reverting the commit that added it.
from pathlib import PureWindowsPath # noqa: F401,E402
from typing import Tuple # noqa: F401,E402
import asyncio # noqa: F401,E402
import base64 # noqa: F401,E402
import concurrent.futures # noqa: F401,E402
from collections import deque # noqa: F401,E402
import functools # noqa: F401,E402
import json # noqa: F401,E402
import re # noqa: F401,E402
import shutil # noqa: F401,E402
import tempfile # noqa: F401,E402
import time # noqa: F401,E402
_PLUGIN_COMPAT_LAZY = {
'CaptureResult': ('tools.computer_use.backend', 'CaptureResult'),
'UIElement': ('tools.computer_use.backend', 'UIElement'),
'cua_driver_install_hint': ('tools.computer_use.cua_backend_driver', 'cua_driver_install_hint'),
'cua_driver_update_check': ('tools.computer_use.cua_backend_driver', 'cua_driver_update_check'),
}
def __getattr__(name): # PEP 562 — lazy so no import cycles
target = _PLUGIN_COMPAT_LAZY.get(name)
if target is None:
raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
import importlib
from hermes_cli.plugin_compat import warn_once
warn_once(__name__, name, *target)
return getattr(importlib.import_module(target[0]), target[1])
# ---- END PLUGIN-COMPAT ----