fix(computer-use): preserve missing driver overrides

hermes_cli/tools_config.py

@@ -1039,6 +1039,20 @@ def install_cua_driver(
     driver_cmd = _cua_driver_cmd()
     binary = _resolved_cua_driver_cmd()
 
+    # An explicit override is authoritative even when it is currently broken.
+    # Do not install or replace the standard system driver: that cannot repair
+    # the configured path and would mutate an unrelated installation.
+    override = os.environ.get("HERMES_CUA_DRIVER_CMD", "").strip()
+    if override and not binary:
+        _print_warning(
+            "    HERMES_CUA_DRIVER_CMD does not resolve to an executable: "
+            f"{override}"
+        )
+        _print_info(
+            "    Fix or unset the override before running computer-use install."
+        )
+        return False
+
     # Not installed → fresh install path (only when caller asked for it).
     if not binary and not upgrade:
         if not _cua_install_target_writable():

tests/hermes_cli/test_install_cua_driver.py

@@ -388,6 +388,23 @@ class TestInstallCuaDriverUpgrade:
 
         runner.assert_not_called()
 
+    @pytest.mark.parametrize("upgrade", [False, True])
+    def test_missing_explicit_override_does_not_install_standard_driver(
+        self, monkeypatch, upgrade
+    ):
+        from hermes_cli import tools_config
+
+        monkeypatch.setenv("HERMES_CUA_DRIVER_CMD", "/missing/custom/cua-driver")
+        with patch.object(
+                 tools_config,
+                 "_resolved_cua_driver_cmd",
+                 return_value=None,
+             ), \
+             patch.object(tools_config, "_run_cua_driver_installer") as runner:
+            assert tools_config.install_cua_driver(upgrade=upgrade) is False
+
+        runner.assert_not_called()
+
     def test_non_upgrade_without_binary_runs_installer(self):
         from hermes_cli import tools_config