fix: keep psutil optional for system health

api/system_health.py

@@ -22,6 +22,13 @@ _PROC_MEMINFO = Path("/proc/meminfo")
 _CPU_SAMPLE_SECONDS = 0.05
 
 
+def _load_optional_psutil():
+    try:
+        return import_module("psutil")
+    except ImportError:
+        raise RuntimeError("psutil_unavailable") from None
+
+
 def _checked_at() -> str:
     return datetime.now(timezone.utc).isoformat()
 
@@ -74,13 +81,13 @@ def _cpu_percent() -> float:
     try:
         start = _read_proc_stat_cpu()
     except OSError:
-        psutil = import_module("psutil")
+        psutil = _load_optional_psutil()
         return _clamp_percent(psutil.cpu_percent(interval=_CPU_SAMPLE_SECONDS))
     time.sleep(_CPU_SAMPLE_SECONDS)
     try:
         end = _read_proc_stat_cpu()
     except OSError:
-        psutil = import_module("psutil")
+        psutil = _load_optional_psutil()
         return _clamp_percent(psutil.cpu_percent(interval=0.0))
     return _cpu_delta_percent(start, end)
 
@@ -106,7 +113,7 @@ def _memory_usage() -> dict[str, int | float]:
     try:
         meminfo = _read_meminfo_kib()
     except OSError:
-        vm = import_module("psutil").virtual_memory()
+        vm = _load_optional_psutil().virtual_memory()
         total = int(getattr(vm, "total", 0) or 0)
         if total <= 0:
             raise RuntimeError("memory_unavailable") from None

requirements.txt

@@ -1,13 +1,14 @@
 # Hermes Web UI -- minimal Python dependencies
 # The server uses PyYAML plus cryptography for optional local passkey/WebAuthn support.
-# psutil is used only for safe aggregate cross-platform CPU/RAM metrics when
-# Linux procfs is unavailable (for example on macOS).
 # All heavy ML/agent deps live in the Hermes agent venv.
 #
 # OPTIONAL: the Edge TTS speech engine (Settings -> Voice -> TTS Engine -> "Edge TTS")
 # needs `edge-tts`. It is intentionally NOT a hard dependency — the /api/tts
 # endpoint returns 503 with an install hint when it's absent. Install it only if
 # you want server-side Microsoft neural voices:  pip install edge-tts
+#
+# OPTIONAL: macOS/non-procfs CPU/RAM system-health metrics need `psutil`.
+# Linux uses procfs without this dependency; install only if you want aggregate
+# CPU/RAM metrics on platforms without /proc:  pip install psutil>=5.9
 pyyaml>=6.0
 cryptography>=42.0
-psutil>=5.9

tests/test_issue693_system_health_panel.py

@@ -131,6 +131,31 @@ def test_system_health_falls_back_to_psutil_when_procfs_is_unavailable(monkeypat
     }
 
 
+def test_system_health_missing_optional_psutil_is_safe_unavailable(monkeypatch):
+    from api import system_health
+
+    class _MissingProcPath:
+        def open(self, *args, **kwargs):
+            raise FileNotFoundError("/private/proc/path")
+
+    def missing_psutil(name):
+        if name == "psutil":
+            raise ModuleNotFoundError("No module named 'psutil'")
+        raise AssertionError(f"unexpected import: {name}")
+
+    monkeypatch.setattr(system_health, "_PROC_STAT", _MissingProcPath())
+    monkeypatch.setattr(system_health, "_PROC_MEMINFO", _MissingProcPath())
+    monkeypatch.setattr(system_health, "import_module", missing_psutil)
+
+    for collect in (system_health._cpu_percent, system_health._memory_usage):
+        try:
+            collect()
+        except RuntimeError as exc:
+            assert str(exc) == "psutil_unavailable"
+        else:  # pragma: no cover - defensive regression clarity
+            raise AssertionError("missing optional psutil should surface a safe unavailable error")
+
+
 def test_system_health_procfs_parse_errors_remain_visible(monkeypatch):
     from api import system_health