fix: read ProxyCommand stdin with a blocking os.read instead of select()

src/colab_cli/commands/ssh.py

@@ -37,7 +37,6 @@
 import contextlib
 import os
 from pathlib import Path
-import select
 import shlex
 import signal
 import subprocess
@@ -360,9 +359,6 @@ def _bridge_proxy_mode(ws: websocket.WebSocket) -> int:
     def stdin_to_ws():
         try:
             while True:
-                ready, _, _ = select.select([stdin_fd], [], [], None)
-                if not ready:
-                    continue
                 data = os.read(stdin_fd, 8192)
                 if not data:
                     break

tests/test_ssh.py

@@ -25,6 +25,7 @@
 import shlex
 import subprocess
 import sys
+import threading
 from unittest.mock import MagicMock
 
 from colab_cli.cli import app
@@ -235,6 +236,49 @@ def test_bridge_proxy_mode_pumps_ws_to_stdout(mocker):
     ws.close.assert_called()
 
 
+def test_bridge_proxy_mode_pumps_stdin_to_ws(mocker):
+    """os.read() chunks leave as binary frames; EOF ends the pump and closes
+    the socket.
+
+    Regression test: the pump used select() on the stdin fd before reading.
+    Windows select() only accepts sockets, so there the OSError killed the
+    pump thread and the remote side saw no input at all; a plain blocking
+    read works on every platform.
+    """
+    reads = iter([b"ping ", b"hello", b""])
+    stdin_eof = threading.Event()
+
+    def fake_read(fd, size):
+        chunk = next(reads)
+        if not chunk:
+            stdin_eof.set()
+        return chunk
+
+    mocker.patch("sys.stdin")
+    sys.stdin.buffer.fileno.return_value = 0
+    mocker.patch.object(ssh_module.os, "read", side_effect=fake_read)
+    fake_stdout = MagicMock()
+    fake_stdout.buffer = io.BytesIO()
+    mocker.patch("sys.stdout", fake_stdout)
+
+    # Hold the ws->stdout loop until the pump has drained stdin, so the
+    # send_binary assertions below can't race the reader thread.
+    def recv_data(control_frame):
+        stdin_eof.wait(timeout=5)
+        return (websocket.ABNF.OPCODE_CLOSE, b"")
+
+    ws = MagicMock()
+    ws.recv_data.side_effect = recv_data
+
+    rc = ssh_module._bridge_proxy_mode(ws)
+    assert rc == 0
+    assert [call.args[0] for call in ws.send_binary.call_args_list] == [
+        b"ping ",
+        b"hello",
+    ]
+    ws.close.assert_called()
+
+
 # --- ProxyCommand shell quoting ---------------------------------------------