diff --git a/nanobot/agent/tools/shell.py b/nanobot/agent/tools/shell.py
index 565b38eb..4950925a 100644
--- a/nanobot/agent/tools/shell.py
+++ b/nanobot/agent/tools/shell.py
@@ -882,6 +882,7 @@ class ExecTool(Tool):
                 elif ch == "&" and not (
                     (i > 0 and command[i - 1] in "<>") or command.startswith("&>", i)
                 ):
+                    current.append(ch)
                     operator_len = 1
                 elif ch in {";", "|"}:
                     operator_len = 1
diff --git a/tests/tools/test_exec_allow_patterns.py b/tests/tools/test_exec_allow_patterns.py
index 12a35059..0a10d5ec 100644
--- a/tests/tools/test_exec_allow_patterns.py
+++ b/tests/tools/test_exec_allow_patterns.py
@@ -76,6 +76,15 @@ def test_guard_allow_patterns_block_single_ampersand_chained_segment():
     assert "allowlist" in result.lower()
 
 
+def test_guard_allow_patterns_preserve_trailing_background_operator():
+    tool = ExecTool(allow_patterns=[r"echo\s+allowlisted"])
+
+    result = tool._guard_command("echo allowlisted &", "/tmp")
+
+    assert result is not None
+    assert "allowlist" in result.lower()
+
+
 def test_guard_allow_patterns_keep_fd_redirection_ampersand():
     tool = ExecTool(allow_patterns=[r"echo\s+allowlisted\s+2>&1"])