fix(gateway): preserve systemd handoff recovery

hermes_cli/gateway.py

@@ -1245,13 +1245,15 @@ def _wait_for_systemd_service_restart(
     *,
     system: bool = False,
     previous_pid: int | None = None,
-    timeout: float = 60.0,
+    timeout: float | None = None,
 ) -> bool:
     """Wait for the gateway service to become active after a restart handoff."""
     import time
 
     svc = get_service_name()
     scope_label = _service_scope_label(system).capitalize()
+    if timeout is None:
+        timeout = _systemd_restart_wait_timeout(system=system)
     deadline = time.monotonic() + timeout
     printed_runtime_wait = False
 
@@ -1308,6 +1310,25 @@ def _wait_for_systemd_service_restart(
     return False
 
 
+def _systemd_restart_wait_timeout(system: bool = False) -> float:
+    """Cover systemd's relaunch delays before applying the runtime wait floor."""
+    from gateway.shutdown_forensics import _parse_systemd_duration_to_us
+
+    props = _read_systemd_unit_properties(
+        system=system,
+        properties=("RestartUSec", "TimeoutStartUSec"),
+    )
+    supervisor_budget = 0.0
+    for name in ("RestartUSec", "TimeoutStartUSec"):
+        raw = props.get(name, "")
+        duration_us = (
+            int(raw) if raw.isdigit() else _parse_systemd_duration_to_us(raw)
+        )
+        if duration_us is not None:
+            supervisor_budget += duration_us / 1_000_000
+    return 60.0 + supervisor_budget
+
+
 def _systemd_unit_is_start_limited(props: dict[str, str]) -> bool:
     result = props.get("Result", "").lower()
     sub_state = props.get("SubState", "").lower()
@@ -4124,13 +4145,32 @@ def systemd_restart(system: bool = False):
             # Exit 75 transfers restart ownership to systemd.  Observe that
             # single replacement instead of issuing another restart that can
             # stop the process systemd has already brought up.
-            _wait_for_systemd_service_restart(system=system, previous_pid=pid)
-            return
+            if _wait_for_systemd_service_restart(system=system, previous_pid=pid):
+                return
+            if _systemd_service_is_start_limited(system=system):
+                return
+
+            # A replacement may have started but not reached gateway runtime
+            # readiness before the wait expired.  Never stop that generation.
+            props = _read_systemd_unit_properties(system=system)
+            replacement_pid = _systemd_main_pid_from_props(props)
+            if (
+                props.get("ActiveState") in {"active", "activating", "reloading"}
+                or props.get("SubState") == "auto-restart"
+                or (replacement_pid is not None and replacement_pid != pid)
+            ):
+                return
+
+            print(
+                "⚠ Systemd did not relaunch the gateway after its graceful exit; "
+                "forcing a service restart..."
+            )
+        else:
+            print(
+                f"⚠ Graceful restart did not complete within {int(wait_budget)}s; "
+                "forcing a service restart..."
+            )
 
-        print(
-            f"⚠ Graceful restart did not complete within {int(wait_budget)}s; "
-            "forcing a service restart..."
-        )
         _run_systemctl(
             ["reset-failed", svc],
             system=system,