fix: provider selection not persisting when switching via hermes model

Two related bugs prevented users from reliably switching providers:

1. OPENAI_BASE_URL poisoning OpenRouter resolution: When a user with a
   custom endpoint ran /model openrouter:model, _resolve_openrouter_runtime
   picked up OPENAI_BASE_URL instead of the OpenRouter URL, causing model
   validation to probe the wrong API and reject valid models.

   Fix: skip OPENAI_BASE_URL when requested_provider is explicitly
   'openrouter'.

2. Provider never saved to config: _save_model_choice() could save
   config.model as a plain string. All five _model_flow_* functions then
   checked isinstance(model, dict) before writing the provider — which
   silently failed on strings. With no provider in config, auto-detection
   would pick up stale credentials (e.g. Codex desktop app) instead of
   the user's explicit choice.

   Fix: _save_model_choice() now always saves as dict format. All flow
   functions also normalize string->dict as a safety net before writing
   provider.

Adds 4 regression tests. 2873 tests pass.

hermes_cli/auth.py

@@ -1671,11 +1671,11 @@ def _save_model_choice(model_id: str) -> None:
     from hermes_cli.config import save_config, load_config, save_env_value
 
     config = load_config()
-    # Handle both string and dict model formats
+    # Always use dict format so provider/base_url can be stored alongside
     if isinstance(config.get("model"), dict):
         config["model"]["default"] = model_id
     else:
-        config["model"] = model_id
+        config["model"] = {"default": model_id}
     save_config(config)
     save_env_value("LLM_MODEL", model_id)
 

hermes_cli/main.py

@@ -906,9 +906,11 @@ def _model_flow_openrouter(config, current_model=""):
         from hermes_cli.config import load_config, save_config
         cfg = load_config()
         model = cfg.get("model")
-        if isinstance(model, dict):
-            model["provider"] = "openrouter"
-            model["base_url"] = OPENROUTER_BASE_URL
+        if not isinstance(model, dict):
+            model = {"default": model} if model else {}
+            cfg["model"] = model
+        model["provider"] = "openrouter"
+        model["base_url"] = OPENROUTER_BASE_URL
         save_config(cfg)
         deactivate_provider()
         print(f"Default model set to: {selected} (via OpenRouter)")
@@ -1090,9 +1092,11 @@ def _model_flow_custom(config):
         # Update config and deactivate any OAuth provider
         cfg = load_config()
         model = cfg.get("model")
-        if isinstance(model, dict):
-            model["provider"] = "custom"
-            model["base_url"] = effective_url
+        if not isinstance(model, dict):
+            model = {"default": model} if model else {}
+            cfg["model"] = model
+        model["provider"] = "custom"
+        model["base_url"] = effective_url
         save_config(cfg)
         deactivate_provider()
 
@@ -1235,9 +1239,11 @@ def _model_flow_named_custom(config, provider_info):
 
         cfg = load_config()
         model = cfg.get("model")
-        if isinstance(model, dict):
-            model["provider"] = "custom"
-            model["base_url"] = base_url
+        if not isinstance(model, dict):
+            model = {"default": model} if model else {}
+            cfg["model"] = model
+        model["provider"] = "custom"
+        model["base_url"] = base_url
         save_config(cfg)
         deactivate_provider()
 
@@ -1307,9 +1313,11 @@ def _model_flow_named_custom(config, provider_info):
 
     cfg = load_config()
     model = cfg.get("model")
-    if isinstance(model, dict):
-        model["provider"] = "custom"
-        model["base_url"] = base_url
+    if not isinstance(model, dict):
+        model = {"default": model} if model else {}
+        cfg["model"] = model
+    model["provider"] = "custom"
+    model["base_url"] = base_url
     save_config(cfg)
     deactivate_provider()
 
@@ -1420,9 +1428,11 @@ def _model_flow_api_key_provider(config, provider_id, current_model=""):
         # Update config with provider and base URL
         cfg = load_config()
         model = cfg.get("model")
-        if isinstance(model, dict):
-            model["provider"] = provider_id
-            model["base_url"] = effective_base
+        if not isinstance(model, dict):
+            model = {"default": model} if model else {}
+            cfg["model"] = model
+        model["provider"] = provider_id
+        model["base_url"] = effective_base
         save_config(cfg)
         deactivate_provider()
 

hermes_cli/runtime_provider.py

@@ -66,9 +66,14 @@ def _resolve_openrouter_runtime(
             if not cfg_provider or cfg_provider == "auto":
                 use_config_base_url = True
 
+    # When the user explicitly requested the openrouter provider, skip
+    # OPENAI_BASE_URL — it typically points to a custom / non-OpenRouter
+    # endpoint and would prevent switching back to OpenRouter (#874).
+    skip_openai_base = requested_norm == "openrouter"
+
     base_url = (
         (explicit_base_url or "").strip()
-        or env_openai_base_url
+        or ("" if skip_openai_base else env_openai_base_url)
         or (cfg_base_url.strip() if use_config_base_url else "")
         or env_openrouter_base_url
         or OPENROUTER_BASE_URL