fix(webui): quiet non-WebSocket handshake noise on public port

The WebSocket channel also serves the WebUI over plain HTTP, so on a
public endpoint (e.g. a Render *.onrender.com service) the underlying
websockets library logs a full-traceback ERROR for every request that
isn't a valid GET handshake: HEAD probes ("unsupported HTTP method;
expected GET"), port scanners, uptime monitors, and TLS-to-plain-port
attempts. These are internet background noise, not server faults.

WebSocketHandshakeNoiseFilter already suppressed "opening handshake
failed" records caused by mid-handshake disconnects; widen it to also
suppress records whose exception chain contains websockets'
InvalidMessage, which covers both non-GET methods and malformed/empty
requests. Genuine server-side handshake errors still log.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nanobot/webui/websocket_logging.py

@@ -4,39 +4,59 @@ from __future__ import annotations
 
 import logging
 
-from websockets.exceptions import ConnectionClosed
+from websockets.exceptions import ConnectionClosed, InvalidMessage
 
 OPENING_HANDSHAKE_FAILED_MESSAGE = "opening handshake failed"
 
+# Exceptions that mean the browser hung up mid-handshake (e.g. a restart races an
+# open tab) rather than a server fault.
+_DISCONNECT_TYPES: tuple[type[BaseException], ...] = (
+    BrokenPipeError,
+    ConnectionAbortedError,
+    ConnectionResetError,
+    ConnectionClosed,
+    EOFError,
+)
 
-def _exception_chain_has_disconnect(exc: BaseException | None) -> bool:
+# InvalidMessage is raised when the peer never sends a valid WebSocket/HTTP-GET
+# opening handshake: HEAD probes ("unsupported HTTP method; expected GET"),
+# port scanners, uptime monitors, and TLS-to-plain-port attempts. On a public
+# endpoint (e.g. a Render *.onrender.com service) this is constant background
+# noise from the internet, not an operational error.
+_MALFORMED_HANDSHAKE_TYPES: tuple[type[BaseException], ...] = (InvalidMessage,)
+
+_SUPPRESSED_TYPES: tuple[type[BaseException], ...] = (
+    _DISCONNECT_TYPES + _MALFORMED_HANDSHAKE_TYPES
+)
+
+
+def _exception_chain_has(exc: BaseException | None, types: tuple[type[BaseException], ...]) -> bool:
     seen: set[int] = set()
     while exc is not None:
         ident = id(exc)
         if ident in seen:
             return False
         seen.add(ident)
-        if isinstance(exc, (
-            BrokenPipeError,
-            ConnectionAbortedError,
-            ConnectionResetError,
-            ConnectionClosed,
-            EOFError,
-        )):
+        if isinstance(exc, types):
             return True
         exc = exc.__cause__ or exc.__context__
     return False
 
 
 class WebSocketHandshakeNoiseFilter(logging.Filter):
-    """Suppress restart-time handshakes where the browser already disconnected."""
+    """Suppress opening-handshake failures that are peer noise, not server faults.
+
+    Covers browsers that disconnect during a restart and non-WebSocket requests
+    (HEAD probes, port scanners, monitors) that hit the public port. Genuine
+    server-side handshake errors are left to log.
+    """
 
     def filter(self, record: logging.LogRecord) -> bool:
         if record.getMessage() != OPENING_HANDSHAKE_FAILED_MESSAGE:
             return True
         exc_info = record.exc_info
         exc = exc_info[1] if isinstance(exc_info, tuple) and len(exc_info) >= 2 else None
-        return not _exception_chain_has_disconnect(exc)
+        return not _exception_chain_has(exc, _SUPPRESSED_TYPES)
 
 
 def websockets_server_logger() -> logging.Logger:

tests/utils/test_webui_websocket_logging.py

@@ -4,6 +4,8 @@ from __future__ import annotations
 
 import logging
 
+from websockets.exceptions import InvalidMessage
+
 from nanobot.webui.websocket_logging import (
     OPENING_HANDSHAKE_FAILED_MESSAGE,
     WebSocketHandshakeNoiseFilter,
@@ -34,6 +36,23 @@ def test_websocket_handshake_noise_filter_suppresses_disconnects() -> None:
     assert not filter_.filter(_log_record(OPENING_HANDSHAKE_FAILED_MESSAGE, empty_handshake))
 
 
+def test_websocket_handshake_noise_filter_suppresses_non_get_probes() -> None:
+    """HEAD probes reach the WS port as InvalidMessage wrapping a ValueError."""
+    filter_ = WebSocketHandshakeNoiseFilter()
+    head_probe = InvalidMessage("did not receive a valid HTTP request")
+    head_probe.__cause__ = ValueError("unsupported HTTP method; expected GET; got HEAD")
+
+    assert not filter_.filter(_log_record(OPENING_HANDSHAKE_FAILED_MESSAGE, head_probe))
+
+
+def test_websocket_handshake_noise_filter_suppresses_malformed_requests() -> None:
+    """Port scanners / TLS-to-plain-port probes raise a bare InvalidMessage."""
+    filter_ = WebSocketHandshakeNoiseFilter()
+    malformed = InvalidMessage("did not receive a valid HTTP request")
+
+    assert not filter_.filter(_log_record(OPENING_HANDSHAKE_FAILED_MESSAGE, malformed))
+
+
 def test_websocket_handshake_noise_filter_keeps_real_errors() -> None:
     filter_ = WebSocketHandshakeNoiseFilter()