fix(models): resolve configured defaults after automatic fallback (#6949)

* fix(models): resolve configured defaults after automatic fallback

* test: isolate photo routing from external MCP registry state

static/js/modelPicker.js

@@ -128,7 +128,7 @@ async function _ensureDefaultPendingChat() {
   if (!_deps || _defaultChatPickInFlight) return;
   if (_deps.getCurrentSessionId && _deps.getCurrentSessionId()) return;
   const pending = _deps.getPendingChat && _deps.getPendingChat();
-  if (pending && pending.modelId) return;
+  if (pending && pending.modelId && pending.source !== 'fallback') return;
   _defaultChatPickInFlight = true;
   const seq = ++_defaultPendingSeq;
   try {
@@ -954,15 +954,6 @@ export function updateModelPicker() {
     }
   }
   const latestPending = _deps.getPendingChat && _deps.getPendingChat();
-  if (
-    !currentSessionId &&
-    !_autoSelectingDefault &&
-    window.modelsModule &&
-    window.modelsModule.getCachedItems &&
-    (!modelId || (latestPending && latestPending.source === 'fallback'))
-  ) {
-    _ensureDefaultPendingChat();
-  }
 
   let displayName = modelId ? modelId.split('/').pop() : 'Select model';
   const routeItems = window.modelsModule?.getCachedItems?.() || [];
@@ -994,6 +985,16 @@ export function updateModelPicker() {
     label.textContent = displayName;
   }
   _updateReasoningEffortUI(modelId, s, latestPending, selectedEndpoint);
+  // A cached default can resolve synchronously and re-render the picker.
+  if (
+    !currentSessionId &&
+    !_autoSelectingDefault &&
+    window.modelsModule &&
+    window.modelsModule.getCachedItems &&
+    (!modelId || (latestPending && latestPending.source === 'fallback'))
+  ) {
+    _ensureDefaultPendingChat();
+  }
 }
 
 // ── Reasoning effort control for models supporting reasoning levels ──

tests/test_model_picker_default_fallback.py

@@ -0,0 +1,81 @@
+"""An automatic fallback must not prevent resolving the configured default."""
+import json
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+from tests.helpers.js_modules import js_function_source
+
+ROOT = Path(__file__).resolve().parents[1]
+PICKER = (ROOT / 'static/js/modelPicker.js').read_text()
+
+
+@pytest.mark.skipif(not shutil.which('node'), reason='node not installed')
+@pytest.mark.parametrize('case', ['fallback', 'manual', 'default', 'session', 'manual-during-fetch', 'no-default'])
+def test_configured_default_and_selection_ownership(case):
+    source = '\n'.join(js_function_source(name, PICKER) for name in [
+        '_ensureDefaultPendingChat', '_ensureModelCacheForFallback', '_firstAvailableModel',
+    ])
+    script = r'''
+const source = JSON.parse(process.argv[1]), mode = process.argv[2];
+let pending = {url:'http://models/v1/chat/completions',modelId:'first',endpointId:'shared',source:'fallback'};
+if (mode === 'manual' || mode === 'default') pending.source = mode;
+const initial = {...pending};
+const configured = {endpoint_url:pending.url,model:'preferred',endpoint_id:'shared'};
+let fetches = 0, updates = 0;
+const _deps = {getCurrentSessionId:()=> mode === 'session' ? 'existing' : null,
+ getPendingChat:()=>pending,setPendingChat:value=>{pending=value;}};
+const window = {modelsModule:{getCachedItems:()=>[{url:initial.url,models:['first','preferred'],endpoint_id:'shared'}]}};
+const localStorage = {setItem(){}};
+const API_BASE = 'http://app';
+let _defaultChatPickInFlight = false, _defaultPendingSeq = 0;
+function updateModelPicker(){updates++;}
+async function fetch(){fetches++; if(mode==='manual-during-fetch') pending={...initial,modelId:'chosen',source:'manual'};
+ return {ok:true,json:async()=>mode==='no-default'?{}:configured};}
+// All helpers share the same lexical dependencies as the production function.
+eval(source.replace('async function _ensureDefaultPendingChat','globalThis.ensureDefault = async function'));
+await globalThis.ensureDefault();
+console.log(JSON.stringify({pending,fetches,updates,inFlight:_defaultChatPickInFlight}));
+'''
+    # Script is a module so async fetch ordering is exercised without a browser shim.
+    result = subprocess.run(['node', '--input-type=module', '-e', script, json.dumps(source), case],
+                            cwd=ROOT, capture_output=True, text=True, check=True, timeout=15)
+    data = json.loads(result.stdout)
+    assert data['inFlight'] is False
+    if case == 'fallback':
+        assert data['pending']['modelId'] == 'preferred'
+        assert data['pending']['source'] == 'default'
+        assert data['fetches'] == 1
+    elif case == 'manual-during-fetch':
+        assert data['pending']['modelId'] == 'chosen'
+        assert data['pending']['source'] == 'manual'
+    else:
+        assert data['pending']['modelId'] == 'first'
+        assert data['pending']['source'] == (case if case in {'manual', 'default'} else 'fallback')
+        assert data['fetches'] == (1 if case == 'no-default' else 0)
+
+
+@pytest.mark.skipif(not shutil.which('node'), reason='node not installed')
+def test_cached_default_updates_visible_picker_after_fallback():
+    names = ['_ensureDefaultPendingChat', '_ensureModelCacheForFallback', '_firstAvailableModel', '_modelExists', 'updateModelPicker']
+    source = '\n'.join(js_function_source(name, PICKER).removeprefix('export ') for name in names)
+    script = r'''
+let pending={url:'http://models/v1/chat/completions',modelId:'first',endpointId:'shared',source:'fallback'};
+const _deps={getCurrentSessionId:()=>null,getSessions:()=>[],getPendingChat:()=>pending,setPendingChat:value=>{pending=value;}};
+const label={textContent:''};
+const document={getElementById:id=>id==='model-picker-label'?label:null};
+const window={__odysseusDefaultChat:{endpoint_url:pending.url,endpoint_id:'shared',model:'preferred'},
+ modelsModule:{getCachedItems:()=>[{url:pending.url,endpoint_id:'shared',models:['first','preferred']}]}};
+const localStorage={setItem(){}};
+let _defaultChatPickInFlight=false,_defaultPendingSeq=0,_autoSelectingDefault=false;
+function providerLogo(){return null;}function providerLabel(){return 'Fixture';}function _updateReasoningEffortUI(){}
+eval(JSON.parse(process.argv[1])+'\nupdateModelPicker();');
+console.log(JSON.stringify({pending,label:label.textContent}));
+'''
+    result = subprocess.run(['node', '--input-type=module', '-e', script, json.dumps(source)],
+                            cwd=ROOT, capture_output=True, text=True, check=True, timeout=15)
+    data = json.loads(result.stdout)
+    assert data['pending']['modelId'] == 'preferred'
+    assert 'preferred' in data['label']