diff --git a/api/config.py b/api/config.py
index 9c4a984..35973c4 100644
--- a/api/config.py
+++ b/api/config.py
@@ -640,9 +640,12 @@ def get_available_models() -> dict:
     # Ensure the user's configured default_model always appears in the dropdown.
     # It may be missing if the model isn't in any hardcoded list (e.g. openrouter/free,
     # a custom local model, or any model.default not in _FALLBACK_MODELS).
+    # Normalize before comparing: strip provider prefix so 'anthropic/claude-opus-4.6'
+    # matches 'claude-opus-4.6' already in the list and avoids a duplicate entry.
     if default_model:
-        all_ids = {m['id'] for g in groups for m in g.get('models', [])}
-        if default_model not in all_ids:
+        _norm = lambda mid: mid.split('/', 1)[-1] if '/' in mid else mid
+        all_ids_norm = {_norm(m['id']) for g in groups for m in g.get('models', [])}
+        if _norm(default_model) not in all_ids_norm:
             # Determine which group to inject into
             label = default_model.split('/')[-1] if '/' in default_model else default_model
             injected = False
diff --git a/static/ui.js b/static/ui.js
index d10f756..a6c73c5 100644
--- a/static/ui.js
+++ b/static/ui.js
@@ -424,11 +424,16 @@ function syncTopbar(){
   } else {
     const m=S.session.model||'';
     const applied=_applyModelToDropdown(m,$('modelSelect'));
-    // If the model isn't in the list at all, add it so the session value is preserved
+    // If the model isn't in the current provider list, add it as a visually marked
+    // "(unavailable)" entry so the session value is preserved without misleading the user.
+    // Selecting it will still attempt to send (same as before), but the label makes
+    // clear it's a stale model from a previous session.
     if(!applied && m){
       const opt=document.createElement('option');
       opt.value=m;
-      opt.textContent=getModelLabel(m);
+      opt.textContent=getModelLabel(m)+' (unavailable)';
+      opt.style.color='var(--muted, #888)';
+      opt.title='This model is no longer in your current provider list';
       $('modelSelect').appendChild(opt);
       $('modelSelect').value=m;
     }
diff --git a/tests/test_model_resolver.py b/tests/test_model_resolver.py
index 38efd9e..ecad825 100644
--- a/tests/test_model_resolver.py
+++ b/tests/test_model_resolver.py
@@ -163,6 +163,33 @@ def test_non_default_provider_models_use_hint_prefix():
             )
 
 
+def test_no_duplicate_when_default_model_is_prefixed():
+    """Issue #147 Bug 2: 'anthropic/claude-opus-4.6' as default_model must not
+    inject a duplicate alongside the existing bare 'claude-opus-4.6' entry in
+    the same provider group."""
+    import api.config as _cfg
+    old_cfg = dict(_cfg.cfg)
+    _cfg.cfg['model'] = {
+        'provider': 'anthropic',
+        'default': 'anthropic/claude-opus-4.6',
+    }
+    try:
+        result = _cfg.get_available_models()
+        norm = lambda mid: mid.split('/', 1)[-1] if '/' in mid else mid
+        # Check each group individually: no group should have two entries that
+        # normalize to the same bare model name
+        for g in result['groups']:
+            bare_ids = [norm(m['id']) for m in g['models']]
+            duplicates = [mid for mid in set(bare_ids) if bare_ids.count(mid) > 1]
+            assert not duplicates, (
+                f"Provider group '{g['provider']}' has duplicate models after normalization: "
+                f"{duplicates}\nFull group: {[m['id'] for m in g['models']]}"
+            )
+    finally:
+        _cfg.cfg.clear()
+        _cfg.cfg.update(old_cfg)
+
+
 def test_default_provider_models_not_prefixed():
     """The active provider's models remain bare (no @prefix added)."""
     import api.config as _cfg