diff --git a/hermes_cli/web_server.py b/hermes_cli/web_server.py
index ca473b0a5..0ea5132f1 100644
--- a/hermes_cli/web_server.py
+++ b/hermes_cli/web_server.py
@@ -431,7 +431,14 @@ class EnvVarReveal(BaseModel):
 
 
 _GATEWAY_HEALTH_URL = os.getenv("GATEWAY_HEALTH_URL")
-_GATEWAY_HEALTH_TIMEOUT = float(os.getenv("GATEWAY_HEALTH_TIMEOUT", "3"))
+try:
+    _GATEWAY_HEALTH_TIMEOUT = float(os.getenv("GATEWAY_HEALTH_TIMEOUT", "3"))
+except (ValueError, TypeError):
+    _log.warning(
+        "Invalid GATEWAY_HEALTH_TIMEOUT value %r — using default 3.0s",
+        os.getenv("GATEWAY_HEALTH_TIMEOUT"),
+    )
+    _GATEWAY_HEALTH_TIMEOUT = 3.0
 
 
 def _probe_gateway_health() -> tuple[bool, dict | None]: