diff --git a/nanobot/agent/tools/shell.py b/nanobot/agent/tools/shell.py
index f3d9bb61..28e2d0bf 100644
--- a/nanobot/agent/tools/shell.py
+++ b/nanobot/agent/tools/shell.py
@@ -598,17 +598,16 @@ class ExecTool(Tool):
         """Best-effort safety guard for potentially destructive commands."""
         cmd = command.strip()
         lower = cmd.lower()
-        match_text = re.sub(r"(^|[^\\])#.*$", r"\1", lower).strip()
 
         # allow_patterns take priority over deny_patterns so that users can
         # exempt specific commands (e.g. "rm -rf" inside a build directory)
         # from the hardcoded deny list via configuration.
         explicitly_allowed = bool(self.allow_patterns) and any(
-            re.fullmatch(p, match_text) for p in self.allow_patterns
+            re.fullmatch(p, lower) for p in self.allow_patterns
         )
         if not explicitly_allowed:
             for pattern in self.deny_patterns:
-                if re.search(pattern, match_text):
+                if re.search(pattern, lower):
                     return "Error: Command blocked by deny pattern filter"
 
             if self.allow_patterns:
diff --git a/tests/tools/test_exec_allow_patterns.py b/tests/tools/test_exec_allow_patterns.py
index 473f4ef6..cfd59f2b 100644
--- a/tests/tools/test_exec_allow_patterns.py
+++ b/tests/tools/test_exec_allow_patterns.py
@@ -66,11 +66,20 @@ def test_allow_patterns_do_not_allow_chained_command_bypass():
     assert "deny pattern filter" in result.lower()
 
 
-def test_allow_patterns_strip_shell_comments_before_matching():
-    """Comments are stripped before allow and deny pattern checks."""
-    tool = ExecTool(allow_patterns=[r"echo\s+hello"])
-    result = tool._guard_command("echo hello # comment with rm -rf /", "/tmp")
-    assert result is None
+def test_allow_patterns_do_not_allow_comment_tail_bypass():
+    """Comment tails must not make a non-allowlisted command match."""
+    tool = ExecTool(allow_patterns=[r"echo allowlisted"])
+    result = tool._guard_command("touch canary # echo allowlisted", "/tmp")
+    assert result is not None
+    assert "allowlist" in result.lower()
+
+
+def test_deny_patterns_search_original_command_with_quoted_hash():
+    """Deny checks must still inspect text after a quoted hash."""
+    tool = ExecTool(deny_patterns=[r"\brm\s+-rf\s+/"])
+    result = tool._guard_command('echo "#"; rm -rf /', "/tmp")
+    assert result is not None
+    assert "deny pattern filter" in result.lower()
 
 
 def test_allow_patterns_fullmatch_allows_exact_command():