fix(gateway): honor --start-now/--start-on-login flags and support non-TTY headless installs

When running `hermes gateway install` on Linux/systemd, the command
unconditionally prompts with two `prompt_yes_no` questions, breaking
headless installs (SSH, CI, provisioning scripts) and ignoring the
existing --start-now / --start-on-login CLI flags that the Windows
branch already respects.

The fix mirrors the Windows path: read CLI flags first, prompt only
when flags are not provided AND stdin is a TTY, and fall back to True
defaults for non-TTY contexts. The argparse help strings are promoted
from SUPPRESS to visible so users can discover the flags.

Fixes #42065

hermes_cli/gateway.py

@@ -6268,8 +6268,24 @@ def _gateway_command_inner(args):
                     "  Or use tmux/screen for persistence: tmux new -s hermes 'hermes gateway run'"
                 )
                 print()
-            start_now = prompt_yes_no("Start the gateway now after installing the service?", True)
-            start_on_login = prompt_yes_no("Start the gateway automatically on login/boot with systemd?", True)
+            # Honor CLI flags (--start-now / --no-start-now, --start-on-login /
+            # --no-start-on-login).  When not provided, prompt interactively or
+            # fall back to True for non-TTY / headless contexts (SSH, CI, pipes).
+            _sn = getattr(args, "start_now", None)
+            if _sn is not None:
+                start_now = _sn
+            elif sys.stdin.isatty():
+                start_now = prompt_yes_no("Start the gateway now after installing the service?", True)
+            else:
+                start_now = True
+
+            _sol = getattr(args, "start_on_login", None)
+            if _sol is not None:
+                start_on_login = _sol
+            elif sys.stdin.isatty():
+                start_on_login = prompt_yes_no("Start the gateway automatically on login/boot with systemd?", True)
+            else:
+                start_on_login = True
             systemd_install(
                 force=force,
                 system=system,

hermes_cli/subcommands/gateway.py

@@ -169,26 +169,26 @@ def build_gateway_parser(
         dest="start_now",
         action="store_true",
         default=None,
-        help=argparse.SUPPRESS,
+        help="Start the gateway service immediately after installing",
     )
     gateway_install.add_argument(
         "--no-start-now",
         dest="start_now",
         action="store_false",
-        help=argparse.SUPPRESS,
+        help="Do not start the gateway service after installing",
     )
     gateway_install.add_argument(
         "--start-on-login",
         dest="start_on_login",
         action="store_true",
         default=None,
-        help=argparse.SUPPRESS,
+        help="Enable the service to start automatically on login/boot",
     )
     gateway_install.add_argument(
         "--no-start-on-login",
         dest="start_on_login",
         action="store_false",
-        help=argparse.SUPPRESS,
+        help="Do not enable the service to start on login/boot",
     )
     gateway_install.add_argument(
         "--elevated-handoff",

tests/hermes_cli/test_gateway.py

@@ -444,6 +444,7 @@ def test_gateway_install_in_container_with_operational_systemd_uses_systemd(monk
     monkeypatch.setattr(gateway, "is_wsl", lambda: False)
     monkeypatch.setattr(gateway, "is_macos", lambda: False)
     monkeypatch.setattr(gateway, "is_managed", lambda: False)
+    monkeypatch.setattr("sys.stdin.isatty", lambda: True)
 
     calls = []
     monkeypatch.setattr(gateway, "prompt_yes_no", lambda question, default=True: calls.append(("prompt", question, default)) or True)
@@ -796,6 +797,7 @@ def test_gateway_install_can_decline_start_now_and_startup(monkeypatch):
     monkeypatch.setattr(gateway, "is_wsl", lambda: False)
     monkeypatch.setattr(gateway, "is_macos", lambda: False)
     monkeypatch.setattr(gateway, "is_managed", lambda: False)
+    monkeypatch.setattr("sys.stdin.isatty", lambda: True)
 
     answers = iter([False, False])
     calls = []
@@ -817,6 +819,87 @@ def test_gateway_install_can_decline_start_now_and_startup(monkeypatch):
     ]
 
 
+def test_gateway_install_systemd_honors_start_now_flag(monkeypatch):
+    """--start-now / --no-start-now should bypass the interactive prompt."""
+    monkeypatch.setattr(gateway, "supports_systemd_services", lambda: True)
+    monkeypatch.setattr(gateway, "is_wsl", lambda: False)
+    monkeypatch.setattr(gateway, "is_macos", lambda: False)
+    monkeypatch.setattr(gateway, "is_managed", lambda: False)
+
+    calls = []
+    monkeypatch.setattr(gateway, "prompt_yes_no", lambda question, default=True: calls.append(("prompt", question)))
+    monkeypatch.setattr(
+        gateway,
+        "systemd_install",
+        lambda force=False, system=False, run_as_user=None, enable_on_startup=True: calls.append(("install", enable_on_startup)),
+    )
+    monkeypatch.setattr(gateway, "systemd_start", lambda system=False: calls.append(("start",)))
+
+    args = SimpleNamespace(
+        gateway_command="install", force=False, system=False,
+        run_as_user=None, start_now=True, start_on_login=False,
+    )
+    gateway.gateway_command(args)
+
+    assert ("prompt", "Start the gateway now after installing the service?") not in calls
+    assert ("start",) in calls
+    assert ("install", False) in calls
+
+
+def test_gateway_install_systemd_non_tty_uses_defaults(monkeypatch):
+    """Non-TTY stdin (headless/CI) should use True defaults without prompting."""
+    monkeypatch.setattr(gateway, "supports_systemd_services", lambda: True)
+    monkeypatch.setattr(gateway, "is_wsl", lambda: False)
+    monkeypatch.setattr(gateway, "is_macos", lambda: False)
+    monkeypatch.setattr(gateway, "is_managed", lambda: False)
+    monkeypatch.setattr("sys.stdin.isatty", lambda: False)
+
+    calls = []
+    monkeypatch.setattr(gateway, "prompt_yes_no", lambda question, default=True: calls.append(("prompt", question)))
+    monkeypatch.setattr(
+        gateway,
+        "systemd_install",
+        lambda force=False, system=False, run_as_user=None, enable_on_startup=True: calls.append(("install", enable_on_startup)),
+    )
+    monkeypatch.setattr(gateway, "systemd_start", lambda system=False: calls.append(("start",)))
+
+    args = SimpleNamespace(gateway_command="install", force=False, system=False, run_as_user=None)
+    gateway.gateway_command(args)
+
+    # No prompts — defaults used (start_now=True, start_on_login=True)
+    assert all(c[0] != "prompt" for c in calls)
+    assert ("install", True) in calls
+    assert ("start",) in calls
+
+
+def test_gateway_install_systemd_no_start_now_flag_non_tty(monkeypatch):
+    """--no-start-now in non-TTY should skip starting the service."""
+    monkeypatch.setattr(gateway, "supports_systemd_services", lambda: True)
+    monkeypatch.setattr(gateway, "is_wsl", lambda: False)
+    monkeypatch.setattr(gateway, "is_macos", lambda: False)
+    monkeypatch.setattr(gateway, "is_managed", lambda: False)
+    monkeypatch.setattr("sys.stdin.isatty", lambda: False)
+
+    calls = []
+    monkeypatch.setattr(gateway, "prompt_yes_no", lambda question, default=True: calls.append(("prompt", question)))
+    monkeypatch.setattr(
+        gateway,
+        "systemd_install",
+        lambda force=False, system=False, run_as_user=None, enable_on_startup=True: calls.append(("install", enable_on_startup)),
+    )
+    monkeypatch.setattr(gateway, "systemd_start", lambda system=False: calls.append(("start",)))
+
+    args = SimpleNamespace(
+        gateway_command="install", force=False, system=False,
+        run_as_user=None, start_now=False, start_on_login=True,
+    )
+    gateway.gateway_command(args)
+
+    assert all(c[0] != "prompt" for c in calls)
+    assert ("install", True) in calls
+    assert ("start",) not in calls
+
+
 def test_find_gateway_pids_falls_back_to_pid_file_when_process_scan_fails(monkeypatch):
     monkeypatch.setattr(gateway, "_get_service_pids", lambda: set())
     monkeypatch.setattr(gateway, "is_windows", lambda: False)