mirror of
https://github.com/NousResearch/hermes-agent.git
synced 2026-04-25 00:51:20 +00:00
229 lines
7.9 KiB
Python
229 lines
7.9 KiB
Python
"""PTY bridge for `hermes dashboard` chat tab.
|
|
|
|
Wraps a child process behind a pseudo-terminal so its ANSI output can be
|
|
streamed to a browser-side terminal emulator (xterm.js) and typed
|
|
keystrokes can be fed back in. The only caller today is the
|
|
``/api/pty`` WebSocket endpoint in ``hermes_cli.web_server``.
|
|
|
|
Design constraints:
|
|
|
|
* **POSIX-only.** Hermes Agent supports Windows exclusively via WSL, which
|
|
exposes a native POSIX PTY via ``openpty(3)``. Native Windows Python
|
|
has no PTY; :class:`PtyUnavailableError` is raised with a user-readable
|
|
install/platform message so the dashboard can render a banner instead of
|
|
crashing.
|
|
* **Zero Node dependency on the server side.** We use :mod:`ptyprocess`,
|
|
which is a pure-Python wrapper around the OS calls. The browser talks
|
|
to the same ``hermes --tui`` binary it would launch from the CLI, so
|
|
every TUI feature (slash popover, model picker, tool rows, markdown,
|
|
skin engine, clarify/sudo/approval prompts) ships automatically.
|
|
* **Byte-safe I/O.** Reads and writes go through the PTY master fd
|
|
directly — we avoid :class:`ptyprocess.PtyProcessUnicode` because
|
|
streaming ANSI is inherently byte-oriented and UTF-8 boundaries may land
|
|
mid-read.
|
|
"""
|
|
|
|
from __future__ import annotations
|
|
|
|
import errno
|
|
import fcntl
|
|
import os
|
|
import select
|
|
import signal
|
|
import struct
|
|
import sys
|
|
import termios
|
|
import time
|
|
from typing import Optional, Sequence
|
|
|
|
try:
|
|
import ptyprocess # type: ignore
|
|
_PTY_AVAILABLE = not sys.platform.startswith("win")
|
|
except ImportError: # pragma: no cover - dev env without ptyprocess
|
|
ptyprocess = None # type: ignore
|
|
_PTY_AVAILABLE = False
|
|
|
|
|
|
__all__ = ["PtyBridge", "PtyUnavailableError"]
|
|
|
|
|
|
class PtyUnavailableError(RuntimeError):
|
|
"""Raised when a PTY cannot be created on this platform.
|
|
|
|
Today this means native Windows (no ConPTY bindings) or a dev
|
|
environment missing the ``ptyprocess`` dependency. The dashboard
|
|
surfaces the message to the user as a chat-tab banner.
|
|
"""
|
|
|
|
|
|
class PtyBridge:
|
|
"""Thin wrapper around ``ptyprocess.PtyProcess`` for byte streaming.
|
|
|
|
Not thread-safe. A single bridge is owned by the WebSocket handler
|
|
that spawned it; the reader runs in an executor thread while writes
|
|
happen on the event-loop thread. Both sides are OK because the
|
|
kernel PTY is the actual synchronization point — we never call
|
|
:mod:`ptyprocess` methods concurrently, we only call ``os.read`` and
|
|
``os.write`` on the master fd, which is safe.
|
|
"""
|
|
|
|
def __init__(self, proc: "ptyprocess.PtyProcess"): # type: ignore[name-defined]
|
|
self._proc = proc
|
|
self._fd: int = proc.fd
|
|
self._closed = False
|
|
|
|
# -- lifecycle --------------------------------------------------------
|
|
|
|
@classmethod
|
|
def is_available(cls) -> bool:
|
|
"""True if a PTY can be spawned on this platform."""
|
|
return bool(_PTY_AVAILABLE)
|
|
|
|
@classmethod
|
|
def spawn(
|
|
cls,
|
|
argv: Sequence[str],
|
|
*,
|
|
cwd: Optional[str] = None,
|
|
env: Optional[dict] = None,
|
|
cols: int = 80,
|
|
rows: int = 24,
|
|
) -> "PtyBridge":
|
|
"""Spawn ``argv`` behind a new PTY and return a bridge.
|
|
|
|
Raises :class:`PtyUnavailableError` if the platform can't host a
|
|
PTY. Raises :class:`FileNotFoundError` or :class:`OSError` for
|
|
ordinary exec failures (missing binary, bad cwd, etc.).
|
|
"""
|
|
if not _PTY_AVAILABLE:
|
|
if sys.platform.startswith("win"):
|
|
raise PtyUnavailableError(
|
|
"Pseudo-terminals are unavailable on this platform. "
|
|
"Hermes Agent supports Windows only via WSL."
|
|
)
|
|
if ptyprocess is None:
|
|
raise PtyUnavailableError(
|
|
"The `ptyprocess` package is missing. "
|
|
"Install with: pip install ptyprocess "
|
|
"(or pip install -e '.[pty]')."
|
|
)
|
|
raise PtyUnavailableError("Pseudo-terminals are unavailable.")
|
|
# Let caller-supplied env fully override inheritance; if they pass
|
|
# None we inherit the server's env (same semantics as subprocess).
|
|
spawn_env = os.environ.copy() if env is None else env
|
|
proc = ptyprocess.PtyProcess.spawn( # type: ignore[union-attr]
|
|
list(argv),
|
|
cwd=cwd,
|
|
env=spawn_env,
|
|
dimensions=(rows, cols),
|
|
)
|
|
return cls(proc)
|
|
|
|
@property
|
|
def pid(self) -> int:
|
|
return int(self._proc.pid)
|
|
|
|
def is_alive(self) -> bool:
|
|
if self._closed:
|
|
return False
|
|
try:
|
|
return bool(self._proc.isalive())
|
|
except Exception:
|
|
return False
|
|
|
|
# -- I/O --------------------------------------------------------------
|
|
|
|
def read(self, timeout: float = 0.2) -> Optional[bytes]:
|
|
"""Read up to 64 KiB of raw bytes from the PTY master.
|
|
|
|
Returns:
|
|
* bytes — zero or more bytes of child output
|
|
* empty bytes (``b""``) — no data available within ``timeout``
|
|
* None — child has exited and the master fd is at EOF
|
|
|
|
Never blocks longer than ``timeout`` seconds. Safe to call after
|
|
:meth:`close`; returns ``None`` in that case.
|
|
"""
|
|
if self._closed:
|
|
return None
|
|
try:
|
|
readable, _, _ = select.select([self._fd], [], [], timeout)
|
|
except (OSError, ValueError):
|
|
return None
|
|
if not readable:
|
|
return b""
|
|
try:
|
|
data = os.read(self._fd, 65536)
|
|
except OSError as exc:
|
|
# EIO on Linux = slave side closed. EBADF = already closed.
|
|
if exc.errno in (errno.EIO, errno.EBADF):
|
|
return None
|
|
raise
|
|
if not data:
|
|
return None
|
|
return data
|
|
|
|
def write(self, data: bytes) -> None:
|
|
"""Write raw bytes to the PTY master (i.e. the child's stdin)."""
|
|
if self._closed or not data:
|
|
return
|
|
# os.write can return a short write under load; loop until drained.
|
|
view = memoryview(data)
|
|
while view:
|
|
try:
|
|
n = os.write(self._fd, view)
|
|
except OSError as exc:
|
|
if exc.errno in (errno.EIO, errno.EBADF, errno.EPIPE):
|
|
return
|
|
raise
|
|
if n <= 0:
|
|
return
|
|
view = view[n:]
|
|
|
|
def resize(self, cols: int, rows: int) -> None:
|
|
"""Forward a terminal resize to the child via ``TIOCSWINSZ``."""
|
|
if self._closed:
|
|
return
|
|
# struct winsize: rows, cols, xpixel, ypixel (all unsigned short)
|
|
winsize = struct.pack("HHHH", max(1, rows), max(1, cols), 0, 0)
|
|
try:
|
|
fcntl.ioctl(self._fd, termios.TIOCSWINSZ, winsize)
|
|
except OSError:
|
|
pass
|
|
|
|
# -- teardown ---------------------------------------------------------
|
|
|
|
def close(self) -> None:
|
|
"""Terminate the child (SIGTERM → 0.5s grace → SIGKILL) and close fds.
|
|
|
|
Idempotent. Reaping the child is important so we don't leak
|
|
zombies across the lifetime of the dashboard process.
|
|
"""
|
|
if self._closed:
|
|
return
|
|
self._closed = True
|
|
|
|
# SIGHUP is the conventional "your terminal went away" signal.
|
|
# We escalate if the child ignores it.
|
|
for sig in (signal.SIGHUP, signal.SIGTERM, signal.SIGKILL):
|
|
if not self._proc.isalive():
|
|
break
|
|
try:
|
|
self._proc.kill(sig)
|
|
except Exception:
|
|
pass
|
|
deadline = time.monotonic() + 0.5
|
|
while self._proc.isalive() and time.monotonic() < deadline:
|
|
time.sleep(0.02)
|
|
|
|
try:
|
|
self._proc.close(force=True)
|
|
except Exception:
|
|
pass
|
|
|
|
# Context-manager sugar — handy in tests and ad-hoc scripts.
|
|
def __enter__(self) -> "PtyBridge":
|
|
return self
|
|
|
|
def __exit__(self, *_exc) -> None:
|
|
self.close()
|