diff --git a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/ModelPickerGroupsBuilder.java b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/ModelPickerGroupsBuilder.java
index fb838528..705ec253 100644
--- a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/ModelPickerGroupsBuilder.java
+++ b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/ModelPickerGroupsBuilder.java
@@ -130,7 +130,7 @@ private static List<DropdownItem> buildModelDropdownItems(List<CopilotModel> mod
       String selectedLabel = StringUtils.isNotBlank(effortLevel) && StringUtils.isNotBlank(name)
           ? name + " - " + effortLevel : null;
 
-      items.add(new DropdownItem.Builder().id(rawName).label(name).selectedLabel(selectedLabel).suffix(suffix)
+      items.add(new DropdownItem.Builder().id(model.getModelKey()).label(name).selectedLabel(selectedLabel).suffix(suffix)
           .icon(resolveModelIcon(model)).hoverProvider(new ModelHoverContentProvider(model)).build());
     }
     return items;
diff --git a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/services/ModelService.java b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/services/ModelService.java
index c76cd6b1..0cb4708b 100644
--- a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/services/ModelService.java
+++ b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/chat/services/ModelService.java
@@ -146,8 +146,11 @@ private void initializeEventHandlers() {
         currentChatMode = ChatMode.Agent;
         updateModelsForChatMode(ChatMode.Agent);
 
-        // Then switch to the specified model (setActiveModel will be called after models are loaded)
-        setActiveModel(modelName);
+        // Resolve name to key, then activate
+        String modelKey = findModelKeyByName(modelName);
+        if (modelKey != null) {
+          setActiveModel(modelKey);
+        }
       }
     };
   }
@@ -328,25 +331,31 @@ private void onDidCopilotStatusChange(CopilotStatusResult copilotStatusResult) {
     }
   }
 
+  private String findModelKeyByName(String modelName) {
+    Map<String, CopilotModel> currentModels = modelObservable.getValue();
+    for (Map.Entry<String, CopilotModel> entry : currentModels.entrySet()) {
+      if (entry.getValue().getModelName().equals(modelName)) {
+        return entry.getKey();
+      }
+    }
+    return null;
+  }
+
   /**
-   * Set the active model by name.
+   * Set the active model by its composite key.
    *
-   * @param modelName the name of the model
+   * @param modelKey the composite key of the model
    */
-  public void setActiveModel(String modelName) {
+  public void setActiveModel(String modelKey) {
     Map<String, CopilotModel> currentModels = modelObservable.getValue();
 
-    // Find model by model name and get its composite key
     String compositeKey = null;
     final CopilotModel model;
     CopilotModel foundModel = null;
 
-    for (Map.Entry<String, CopilotModel> entry : currentModels.entrySet()) {
-      if (entry.getValue().getModelName().equals(modelName)) {
-        compositeKey = entry.getKey();
-        foundModel = entry.getValue();
-        break;
-      }
+    if (currentModels.containsKey(modelKey)) {
+      compositeKey = modelKey;
+      foundModel = currentModels.get(modelKey);
     }
     model = foundModel;
     if (model != null && compositeKey != null) {
@@ -396,7 +405,7 @@ public CopilotModel getFallbackModel() {
    */
   public void setFallBackModelAsActiveModel() {
     if (fallbackModel != null) {
-      setActiveModel(fallbackModel.getModelName());
+      setActiveModel(fallbackModel.getModelKey());
     }
   }
 
@@ -551,7 +560,7 @@ public void bindModelPicker(final DropdownButton picker) {
             if (activeModel == null || picker.isDisposed()) {
               return;
             }
-            picker.setSelectedItemId(activeModel.getModelName());
+            picker.setSelectedItemId(activeModel.getModelKey());
             String suffix = StringUtils.isNotBlank(activeModel.getDegradationReason())
                 ? " - " + activeModel.getDegradationReason() : "";
             picker.setToolTipText(NLS.bind(Messages.chat_actionBar_modelPicker_Tooltip, suffix));
diff --git a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/swt/ModelHoverContentProvider.java b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/swt/ModelHoverContentProvider.java
index a1698ffe..e0690211 100644
--- a/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/swt/ModelHoverContentProvider.java
+++ b/com.microsoft.copilot.eclipse.ui/src/com/microsoft/copilot/eclipse/ui/swt/ModelHoverContentProvider.java
@@ -278,7 +278,7 @@ public void mouseDown(MouseEvent e) {
         // to update its label/suffix so the dropdown control reflects the (model, effort) pair the user just
         // chose -- even when they clicked an effort on a non-active model.
         modelService.setSelectedReasoningEffort(model, effort);
-        modelService.setActiveModel(model.getModelName());
+        modelService.setActiveModel(model.getModelKey());
         // Close the entire dropdown (hover + main popup) via the host-provided callback so the user sees an
         // immediate dismiss. Next time the dropdown opens, refreshBoundModelPickers (invoked from
         // setSelectedReasoningEffort) has updated the model row's suffix to reflect the newly selected effort.