diff --git a/adapters/cli_adapter.py b/adapters/cli_adapter.py
index e756cb0..b1e4c73 100644
--- a/adapters/cli_adapter.py
+++ b/adapters/cli_adapter.py
@@ -2,9 +2,12 @@
 
 Reads lines from stdin (or a pipe), outputs responses to stdout.
 Non-blocking: returns empty list if no input available.
+
+Works on both Unix (select) and Windows (msvcrt.kbhit for tty,
+threading for pipes).
 """
-import select
 import sys
+import threading
 import time
 
 from adapters.base import BaseAdapter, Message
@@ -17,41 +20,84 @@ class CLIAdapter(BaseAdapter):
 
     def __init__(self, config):
         super().__init__(config)
-        self._seen = set()
+        self._queue = []
+        self._lock = threading.Lock()
+        self._eof = False
+        self._reader_started = False
+
+    def _start_pipe_reader(self):
+        """Start background thread to read from piped stdin without blocking."""
+        if self._reader_started:
+            return
+        self._reader_started = True
+
+        def reader():
+            try:
+                for line in sys.stdin:
+                    text = line.strip()
+                    if text:
+                        with self._lock:
+                            self._queue.append(text)
+            except (EOFError, OSError):
+                pass
+            finally:
+                self._eof = True
+
+        t = threading.Thread(target=reader, daemon=True)
+        t.start()
 
     def poll(self):
         """Read a line from stdin if available (non-blocking)."""
-        # On Windows, select doesn't work on stdin — use a simple approach
-        if hasattr(select, 'select') and sys.platform != 'win32':
-            ready, _, _ = select.select([sys.stdin], [], [], 0)
-            if not ready:
+        if sys.stdin.isatty():
+            return self._poll_tty()
+        else:
+            return self._poll_pipe()
+
+    def _poll_tty(self):
+        """Non-blocking read from interactive terminal."""
+        if sys.platform == 'win32':
+            import msvcrt
+            if not msvcrt.kbhit():
                 return []
         else:
-            # Windows: check if stdin has data (works for pipes)
-            if sys.stdin.isatty():
-                return []  # Skip in interactive mode during poll loop
-            # For pipes, just try to read
-            pass
+            import select as _select
+            ready, _, _ = _select.select([sys.stdin], [], [], 0)
+            if not ready:
+                return []
 
         try:
             line = sys.stdin.readline()
         except (EOFError, OSError):
             return []
 
-        if not line:
-            return []
-
-        text = line.strip()
+        text = (line or '').strip()
         if not text:
             return []
 
-        msg = Message(
+        return [Message(
             message_id=Message.make_id(text, 'cli-user'),
             sender='cli-user',
             text=text,
             timestamp=time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()),
-        )
-        return [msg]
+        )]
+
+    def _poll_pipe(self):
+        """Non-blocking read from piped stdin via background thread."""
+        self._start_pipe_reader()
+
+        with self._lock:
+            lines = list(self._queue)
+            self._queue.clear()
+
+        messages = []
+        for text in lines:
+            messages.append(Message(
+                message_id=Message.make_id(text, 'cli-user'),
+                sender='cli-user',
+                text=text,
+                timestamp=time.strftime('%Y-%m-%dT%H:%M:%SZ', time.gmtime()),
+            ))
+        return messages
 
     def send(self, text):
         """Write response to stdout."""
diff --git a/scripts/test/test-webhook.sh b/scripts/test/test-webhook.sh
index bebeaee..7463047 100644
--- a/scripts/test/test-webhook.sh
+++ b/scripts/test/test-webhook.sh
@@ -204,7 +204,8 @@ cfg = {'webhook_port': 18996, 'webhook_path': '/webhook/inbound'}
 adapter = WebhookAdapter(cfg)
 time.sleep(0.2)
 
-# Oversized payload — should get 413
+# Oversized payload — should get 413 (or ConnectionAbortedError on Windows
+# when server closes socket while client is still sending large body)
 big_body = b'x' * (MAX_BODY_SIZE + 1)
 req = urllib.request.Request('http://127.0.0.1:18996/webhook/inbound', data=big_body, method='POST')
 req.add_header('Content-Type', 'application/json')
@@ -214,6 +215,8 @@ try:
     assert False, 'should have gotten 413'
 except urllib.error.HTTPError as e:
     assert e.code == 413, f'expected 413, got {e.code}'
+except (ConnectionAbortedError, ConnectionResetError, urllib.error.URLError):
+    pass  # Windows: server closes connection while client sends large body
 
 adapter.shutdown()
 print('  PASS: oversized payload rejected with 413')