diff --git a/platform/hermes/start-hermes-managed.sh b/platform/hermes/start-hermes-managed.sh
index c976b71..dbb242d 100755
--- a/platform/hermes/start-hermes-managed.sh
+++ b/platform/hermes/start-hermes-managed.sh
@@ -6,6 +6,70 @@ if [ ! -r "$config" ]; then
   echo "HERMES_START_REFUSED: managed config is not readable" >&2
   exit 78
 fi
+
+# Hermes Desktop can persist a model selection back into config.yaml.  A bad
+# selection must never be able to detach the central gateway from Athena's
+# authenticated profile router.  Repair only the managed model block from the
+# container secret on every start; all user settings, sessions and MCP entries
+# remain untouched.
+python - "$config" <<'PY'
+import os
+import re
+import sys
+import tempfile
+
+path = sys.argv[1]
+router_key = os.environ.get("ROUTER_API_KEY", "").strip()
+if not router_key or router_key.startswith("${"):
+    raise SystemExit("HERMES_START_REFUSED: ROUTER_API_KEY is missing")
+
+with open(path, "r", encoding="utf-8") as handle:
+    lines = handle.readlines()
+
+try:
+    start = next(i for i, line in enumerate(lines) if re.match(r"^model:\s*(?:#.*)?$", line))
+except StopIteration:
+    raise SystemExit("HERMES_START_REFUSED: model block is missing")
+
+end = len(lines)
+for i in range(start + 1, len(lines)):
+    if re.match(r"^[A-Za-z_][A-Za-z0-9_-]*:\s*", lines[i]):
+        end = i
+        break
+
+managed = {
+    "default": "qwen-medium",
+    "provider": "custom",
+    "base_url": "http://router:8081/v1",
+    "api_key": router_key,
+}
+
+for field, value in managed.items():
+    rendered = f'  {field}: "{value}"\n'
+    match = next(
+        (i for i in range(start + 1, end) if re.match(rf"^\s+{re.escape(field)}:\s*", lines[i])),
+        None,
+    )
+    if match is None:
+        lines.insert(end, rendered)
+        end += 1
+    else:
+        lines[match] = rendered
+
+directory = os.path.dirname(path)
+fd, temporary = tempfile.mkstemp(prefix=".config.yaml.", dir=directory, text=True)
+try:
+    with os.fdopen(fd, "w", encoding="utf-8") as handle:
+        handle.writelines(lines)
+        handle.flush()
+        os.fsync(handle.fileno())
+    os.chmod(temporary, os.stat(path).st_mode & 0o777)
+    os.replace(temporary, path)
+finally:
+    if os.path.exists(temporary):
+        os.unlink(temporary)
+PY
+
 grep -Eq '^[[:space:]]+provider:[[:space:]]+["'\'']?custom["'\'']?[[:space:]]*$' "$config" || {
   echo "HERMES_START_REFUSED: provider is not custom" >&2
   exit 78
@@ -16,4 +80,3 @@ grep -Eq '^[[:space:]]+base_url:[[:space:]]+["'\'']?http://router:8081/v1["'\'']
 }
 
 exec hermes gateway run
-