fix(cron): tolerate NUL-byte path tokens from the command string in lifecycle guard

cron/lifecycle_guard.py

@@ -258,7 +258,11 @@ def _read_referenced_script(path: Path) -> tuple[Optional[str], bool]:
     flags = os.O_RDONLY | getattr(os, "O_NONBLOCK", 0)
     try:
         descriptor = os.open(path, flags)
-    except OSError:
+    except (OSError, ValueError):
+        # ValueError: an embedded NUL byte in the path itself — the token
+        # came straight from the command string, not from file contents, so
+        # the #76762 binary-content skip never sees it. No such file can
+        # exist on POSIX; there is nothing to read.
         return None, False
     try:
         metadata = os.fstat(descriptor)

tests/hermes_cli/test_gateway_restart_loop.py

@@ -695,6 +695,25 @@ def test_absolute_path_binary_does_not_crash_guard(self):
         )
         assert result is False
 
+    def test_nul_byte_in_command_string_does_not_crash_guard(self):
+        """A NUL byte in the command string itself must not crash the guard.
+
+        #76762 covered NUL bytes read out of a referenced binary's contents,
+        but a path token containing a literal NUL can also arrive straight
+        from the command string (e.g. an agent emitting "\\x00" inside a
+        JSON-encoded command). os.open() raises ValueError — not OSError —
+        for such a path, which escaped _read_referenced_script's handler and
+        crashed the guard. A NUL-bearing path can never exist on POSIX, so
+        it reads as "nothing to scan".
+        """
+        from cron.lifecycle_guard import (
+            contains_gateway_lifecycle_command_or_referenced_script,
+        )
+        result = contains_gateway_lifecycle_command_or_referenced_script(
+            "bash /tmp/junk\x00fragment.sh"
+        )
+        assert result is False
+
     def test_shell_script_reference_walk_still_works(self, tmp_path):
         """The referenced-script walk still applies to real shell scripts:
         a .sh script that itself invokes a lifecycle command is caught."""