fix(model-picker): prevent cross-profile provider dropdown contamination

Clean rebase of b3nw's #5727 (rebase-first).

Co-authored-by: b3nw <b3nw@users.noreply.github.com>

static/ui.js

@@ -2570,8 +2570,17 @@ function _modelStateForSelect(sel, modelId){
   if(!value) return {model:'',model_provider:null};
   const explicitProvider=_providerFromModelValue(value);
   if(explicitProvider) return {model:value,model_provider:explicitProvider};
-  const opt=sel&&sel.selectedOptions&&sel.selectedOptions[0];
-  const provider=String(_getOptionProviderId(opt)||'').trim();
+  let opt=null;
+  if(sel&&sel.options){
+    opt=Array.from(sel.options).find(o=>o.value===value);
+  }
+  if(!opt){
+    const currentOpt=sel&&sel.selectedOptions&&sel.selectedOptions[0];
+    if(currentOpt&&currentOpt.value===value){
+      opt=currentOpt;
+    }
+  }
+  const provider=String((opt&&_getOptionProviderId(opt))||'').trim();
   return {model:value,model_provider:(provider&&provider!=='default')?provider:null};
 }
 function _captureModelDropdownSelection(sel){

tests/test_chat_start_provider_fallback.py

@@ -215,6 +215,24 @@ def test_model_state_reads_live_custom_provider_from_option_metadata(driver_path
     assert state == {"model": "llama-3.3-custom", "model_provider": "custom:lab"}
 
 
+@node_test
+def test_model_state_does_not_use_unrelated_selected_option_provider(driver_path):
+    # If the requested model is not in the options and differs from the currently
+    # selected option, it should return model_provider = null instead of the selected option's provider.
+    state = _run_model_state_helper(driver_path, {
+        "model": "kilo/minimax/minimax-m3",
+        "initialValue": "qwen3.6:27b-mlx",
+        "options": [{
+            "provider": "ollama",
+            "optionProvider": "ollama",
+            "value": "qwen3.6:27b-mlx",
+        }],
+    })
+
+    assert state == {"model": "kilo/minimax/minimax-m3", "model_provider": None}
+
+
+
 def test_live_custom_models_are_tagged_with_provider_metadata():
     ui_src = UI_JS_PATH.read_text(encoding="utf-8")
     start = ui_src.index("function _addLiveModelsToSelect")