refactor: extract resolve_model_provider helper, fix cross-provider routing

Replace duplicated inline provider resolution in routes.py and streaming.py
with a shared resolve_model_provider() helper in config.py.

Improvements over original:
- If model ID has a prefix matching any known direct-API provider
  (not just the config provider), strip it and route correctly.
  This handles edge cases like localStorage restoring a model from
  a different provider group.
- Single source of truth for the resolution logic.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

api/config.py

@@ -312,6 +312,36 @@ _PROVIDER_MODELS = {
 }
 
 
+def resolve_model_provider(model_id: str):
+    """Resolve bare model name and provider for AIAgent.
+
+    Model IDs from the dropdown may include a provider prefix
+    (e.g. 'anthropic/claude-sonnet-4.6').  Direct-API providers expect
+    bare model names, while OpenRouter expects the full provider/model path.
+
+    Returns (model, provider) where provider may be None.
+    """
+    config_provider = None
+    model_cfg = cfg.get('model', {})
+    if isinstance(model_cfg, dict):
+        config_provider = model_cfg.get('provider')
+
+    model_id = (model_id or '').strip()
+    if not model_id:
+        return model_id, config_provider
+
+    if '/' in model_id:
+        prefix, bare = model_id.split('/', 1)
+        # If prefix matches config provider, strip it
+        if config_provider and prefix == config_provider:
+            return bare, config_provider
+        # If prefix is a known direct-API provider, use it
+        if prefix in _PROVIDER_MODELS:
+            return bare, prefix
+
+    return model_id, config_provider
+
+
 def get_available_models() -> dict:
     """
     Return available models grouped by provider.

api/routes.py

@@ -629,15 +629,9 @@ def _handle_chat_sync(handler, body):
     try:
         from run_agent import AIAgent
         with CHAT_LOCK:
-            from api.config import cfg as _hcfg
-            _model = s.model or ''
-            _prov = None
-            _mc = _hcfg.get('model', {})
-            if isinstance(_mc, dict):
-                _prov = _mc.get('provider')
-            if _prov and '/' in _model and _model.startswith(_prov + '/'):
-                _model = _model.split('/', 1)[1]
-            agent = AIAgent(model=_model, provider=_prov, platform='cli', quiet_mode=True,
+            from api.config import resolve_model_provider
+            _model, _provider = resolve_model_provider(s.model)
+            agent = AIAgent(model=_model, provider=_provider, platform='cli', quiet_mode=True,
                            enabled_toolsets=CLI_TOOLSETS, session_id=s.session_id)
             workspace_ctx = f"[Workspace: {s.workspace}]\n"
             workspace_system_msg = (

api/streaming.py

@@ -13,7 +13,7 @@ from pathlib import Path
 from api.config import (
     STREAMS, STREAMS_LOCK, CANCEL_FLAGS, CLI_TOOLSETS,
     _get_session_agent_lock, _set_thread_env, _clear_thread_env,
-    cfg as _hermes_cfg,
+    resolve_model_provider,
 )
 
 # Lazy import to avoid circular deps -- hermes-agent is on sys.path via api/config.py
@@ -100,18 +100,10 @@ def _run_agent_streaming(session_id, msg_text, model, workspace, stream_id, atta
 
             if AIAgent is None:
                 raise ImportError("AIAgent not available -- check that hermes-agent is on sys.path")
-            # Resolve provider from config so agent routes to the right API
-            _provider = None
-            model_cfg = _hermes_cfg.get('model', {})
-            if isinstance(model_cfg, dict):
-                _provider = model_cfg.get('provider')
-            # If model has provider/ prefix matching config provider, strip it
-            # so AIAgent doesn't misroute to OpenRouter
-            if _provider and '/' in model and model.startswith(_provider + '/'):
-                model = model.split('/', 1)[1]
+            resolved_model, resolved_provider = resolve_model_provider(model)
             agent = AIAgent(
-                model=model,
-                provider=_provider,
+                model=resolved_model,
+                provider=resolved_provider,
                 platform='cli',
                 quiet_mode=True,
                 enabled_toolsets=CLI_TOOLSETS,