Cisco IOS collection: disable paging after prompt drain.

Send terminal length 0 ourselves and wait for a full prompt line, so the
echo line cannot end the read and long show output no longer stalls on
--More--.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

netx_api/ne_session_connect.py

@@ -309,18 +309,20 @@ def _cisco_ios_collection_driver_class(base_cls: type) -> type:
     class _CiscoIosCollectionSession(base_cls):  # type: ignore[misc,valid-type]
         def session_preparation(self) -> None:
             # Stock Netmiko width/paging on IOSv+CR races leftover prompts
-            # (``terexit`` / ``terminal lengexit``) or blocks forever waiting for
-            # setup echo once VTY pressure builds. The interactive WebCRT path
-            # skips these commands and still returns complete show output; MCP
-            # show/display bodies are short enough that --More-- is not required.
-            # Keep hostname discovery so send_show_command can use a full-line
-            # prompt expect without auto_find_prompt.
+            # (``terexit`` / ``terminal lengexit``). Drain first, then disable
+            # paging ourselves and wait for a full prompt line: the echo line
+            # ``R2#terminal length 0`` cannot match, so long show output never
+            # stalls on --More--.
             from .ne_netmiko import drain_read_channel
 
             initial_pattern = r"(?m:^[^\r\n#>]+[>#][ \t]*$)"
             self._test_channel_read(pattern=initial_pattern)
             self.set_base_prompt(pattern=initial_pattern)
             drain_read_channel(self, idle_reads=8, pause_sec=0.1)
+            self.write_channel("terminal length 0" + self.RETURN)
+            prompt_line = rf"(?m:^{re.escape(self.base_prompt)}[>#][ \t]*$)"
+            self.read_until_pattern(pattern=prompt_line, read_timeout=20)
+            drain_read_channel(self, idle_reads=8, pause_sec=0.1)
 
     _CiscoIosCollectionSession.__name__ = (
         f"CiscoIosCollection{getattr(base_cls, '__name__', 'Netmiko')}"

tests/test_ne_session_interactive.py

@@ -82,24 +82,29 @@ class CiscoCollectionPrepTests(unittest.TestCase):
         return sess
 
     @patch("netx_api.ne_netmiko.drain_read_channel")
-    def test_setup_only_establishes_hostname_prompt(self, drain: MagicMock):
+    def test_setup_drains_then_disables_paging_on_full_prompt_line(self, drain: MagicMock):
         sess = self.session()
         order: list[str] = []
         drain.side_effect = lambda *_a, **_k: order.append("drain")
         sess.set_base_prompt.side_effect = lambda **kw: order.append("prompt")
+        sess.write_channel.side_effect = lambda data: order.append(f"write:{data}")
+        sess.read_until_pattern.side_effect = lambda **kw: order.append("read")
         sess.session_preparation()
-        self.assertEqual(order, ["prompt", "drain"])
+        self.assertEqual(order, ["prompt", "drain", "write:terminal length 0\r", "read", "drain"])
         sess.set_base_prompt.assert_called_once()
         initial = sess._test_channel_read.call_args.kwargs["pattern"]
         self.assertIsNotNone(re.search(initial, "R2.lab#"))
         self.assertIsNone(re.search(initial, "R2.lab#terminal length 0"))
         channel = SimpleNamespace(read_timeout_override=None, _read_buffer="", read_channel=lambda: "R2.lab#")
         self.assertEqual(BaseConnection.read_until_pattern(channel, pattern=initial), "R2.lab#")
+        prompt_line = sess.read_until_pattern.call_args.kwargs["pattern"]
+        self.assertIsNone(re.search(prompt_line, "R2.lab#terminal length 0\r\n"))
+        self.assertIsNone(re.search(prompt_line, "R2Xlab#"))
+        self.assertIsNotNone(re.search(prompt_line, "R2.lab#terminal length 0\r\nR2.lab#"))
         sess.set_terminal_width.assert_not_called()
         sess.disable_paging.assert_not_called()
-        sess.write_channel.assert_not_called()
         sess.send_command_timing.assert_not_called()
-        drain.assert_called_once()
+        self.assertEqual(drain.call_count, 2)
         self.assertEqual(drain.call_args.kwargs.get("idle_reads"), 8)
 
     @patch("netx_api.ne_netmiko.drain_read_channel")
@@ -113,13 +118,13 @@ class CiscoCollectionPrepTests(unittest.TestCase):
         sess.send_command_timing.assert_not_called()
 
     @patch("netx_api.ne_netmiko.drain_read_channel")
-    def test_setup_never_sends_terminal_commands(self, drain: MagicMock):
+    def test_setup_sends_only_terminal_length_zero(self, drain: MagicMock):
         sess = self.session()
         sess.session_preparation()
-        sess.write_channel.assert_not_called()
+        sess.write_channel.assert_called_once_with("terminal length 0\r")
         sess.set_terminal_width.assert_not_called()
         sess.disable_paging.assert_not_called()
-        drain.assert_called_once_with(sess, idle_reads=8, pause_sec=0.1)
+        drain.assert_called_with(sess, idle_reads=8, pause_sec=0.1)
 
 
 class ZteCollectionPrepTests(unittest.TestCase):