fix: extract custom_provider_slug() helper, harden gateway test

- Add custom_provider_slug() to hermes_cli/providers.py as the single
  source of truth for building 'custom:<name>' slugs.
- Use it in resolve_custom_provider() and list_authenticated_providers()
  instead of duplicated inline slug construction.
- Add _session_model_overrides and _voice_mode to gateway test runner
  for object.__new__() safety.

hermes_cli/model_switch.py

@@ -25,6 +25,7 @@ from dataclasses import dataclass
 from typing import List, NamedTuple, Optional
 
 from hermes_cli.providers import (
+    custom_provider_slug,
     determine_api_mode,
     get_label,
     is_aggregator,
@@ -887,7 +888,7 @@ def list_authenticated_providers(
             if not display_name or not api_url:
                 continue
 
-            slug = "custom:" + display_name.lower().replace(" ", "-")
+            slug = custom_provider_slug(display_name)
             if slug in seen_slugs:
                 continue
 

hermes_cli/providers.py

@@ -452,6 +452,16 @@ def resolve_user_provider(name: str, user_config: Dict[str, Any]) -> Optional[Pr
     )
 
 
+def custom_provider_slug(display_name: str) -> str:
+    """Build a canonical slug for a custom_providers entry.
+
+    Matches the convention used by runtime_provider and credential_pool
+    (``custom:<normalized-name>``).  Centralised here so all call-sites
+    produce identical slugs.
+    """
+    return "custom:" + display_name.strip().lower().replace(" ", "-")
+
+
 def resolve_custom_provider(
     name: str,
     custom_providers: Optional[List[Dict[str, Any]]],
@@ -461,7 +471,6 @@ def resolve_custom_provider(
         return None
 
     requested = (name or "").strip().lower()
-    canonical = normalize_provider(name)
     if not requested:
         return None
 
@@ -479,8 +488,8 @@ def resolve_custom_provider(
         if not display_name or not api_url:
             continue
 
-        slug = "custom:" + display_name.lower().replace(" ", "-")
-        if requested not in {display_name.lower(), slug, canonical}:
+        slug = custom_provider_slug(display_name)
+        if requested not in {display_name.lower(), slug}:
             continue
 
         return ProviderDef(

tests/gateway/test_model_command_custom_providers.py

@@ -12,6 +12,8 @@ from gateway.session import SessionSource
 def _make_runner():
     runner = object.__new__(GatewayRunner)
     runner.adapters = {}
+    runner._voice_mode = {}
+    runner._session_model_overrides = {}
     return runner