refactor(webui): infer fallback from active model

nanobot/bus/outbound_events.py

@@ -100,7 +100,6 @@ class TurnModelUpdatedEvent(OutboundEvent):
     model: str
     model_preset: str | None = None
     context_window_tokens: int | None = None
-    is_fallback: bool = False
 
 
 def outbound_message_for_event(

nanobot/channels/websocket/runtime.py

@@ -1685,7 +1685,6 @@ class WebSocketChannel(BaseChannel):
                     model_name=event.model,
                     model_preset=event.model_preset,
                     context_window_tokens=event.context_window_tokens,
-                    is_fallback=event.is_fallback,
                 )
             return
         if isinstance(event, UserInputEvent):
@@ -2103,7 +2102,6 @@ class WebSocketChannel(BaseChannel):
         model_name: Any,
         model_preset: Any = None,
         context_window_tokens: Any = None,
-        is_fallback: Any = False,
     ) -> None:
         """Notify one chat's subscribers which model is handling its current request."""
         conns = list(self._subs.get(chat_id, ()))
@@ -2117,7 +2115,6 @@ class WebSocketChannel(BaseChannel):
             "event": "turn_model_updated",
             "chat_id": chat_id,
             "model_name": model_name.strip(),
-            "is_fallback": is_fallback is True,
         }
         if isinstance(model_preset, str) and model_preset.strip():
             body["model_preset"] = model_preset.strip()

nanobot/channels/websocket/tests/test_websocket_channel.py

@@ -2061,7 +2061,6 @@ async def test_send_scopes_turn_model_updates_to_the_subscribed_chat() -> None:
                 model="deepseek/deepseek-chat",
                 model_preset="Deep Research",
                 context_window_tokens=128_000,
-                is_fallback=True,
             ),
         )
     )
@@ -2073,7 +2072,6 @@ async def test_send_scopes_turn_model_updates_to_the_subscribed_chat() -> None:
         "model_name": "deepseek/deepseek-chat",
         "model_preset": "Deep Research",
         "context_window_tokens": 128_000,
-        "is_fallback": True,
     }
     chat_two.send.assert_not_awaited()
 

nanobot/session/webui_turns.py

@@ -495,7 +495,6 @@ def build_webui_fallback_model_observer(bus: MessageBus) -> FallbackModelObserve
                         if context.runtime is not None
                         else None
                     ),
-                    is_fallback=True,
                 ),
                 metadata=context.metadata,
             )

tests/utils/test_webui_turn_helpers.py

@@ -179,7 +179,6 @@ async def test_fallback_model_is_scoped_to_its_websocket_chat() -> None:
     assert isinstance(outbound.event, TurnModelUpdatedEvent)
     assert outbound.event.model == "deepseek/deepseek-chat"
     assert outbound.event.model_preset == "Deep Research"
-    assert outbound.event.is_fallback is True
 
 
 @pytest.mark.asyncio
@@ -219,7 +218,6 @@ async def test_admitted_runtime_publishes_chat_scoped_model_and_preset(tmp_path)
     assert isinstance(outbound.event, TurnModelUpdatedEvent)
     assert outbound.event.model == "openai-codex/gpt-5.6"
     assert outbound.event.model_preset == "Codex"
-    assert outbound.event.is_fallback is False
 
 
 @pytest.mark.asyncio

webui/src/components/thread/ThreadShell.tsx

@@ -400,7 +400,7 @@ function toModelBadgeInfo(
   );
   return {
     label,
-    model: toModelBadgeLabel(model),
+    model: model?.trim() || null,
     provider,
     providerLabel: provider ? providerDisplayLabel(settings?.providers ?? [], provider) : null,
     needsSetup,
@@ -959,9 +959,12 @@ export function ThreadShell({
     setFallbackModelName(null);
     return client.onChat(chatId, (event) => {
       if (event.event !== "turn_model_updated") return;
-      setFallbackModelName(event.is_fallback ? event.model_name : null);
+      const activeModel = event.model_name.trim();
+      setFallbackModelName(
+        modelBadge.model && activeModel !== modelBadge.model ? activeModel : null,
+      );
     });
-  }, [chatId, client]);
+  }, [chatId, client, modelBadge.model]);
 
   useEffect(() => {
     if (!historyKey || !chatId || loading) return;
@@ -1451,7 +1454,7 @@ export function ThreadShell({
               : t("thread.composer.placeholderThread")
           }
           modelLabel={modelBadgeLabel}
-          modelDetail={modelBadge.model}
+          modelDetail={toModelBadgeLabel(modelBadge.model)}
           modelPreset={activeModelPreset}
           modelPresets={modelPresetOptions}
           onModelPresetChange={handleModelPresetChange}
@@ -1498,7 +1501,7 @@ export function ThreadShell({
               : t("thread.composer.placeholderHero")
           }
           modelLabel={modelBadgeLabel}
-          modelDetail={modelBadge.model}
+          modelDetail={toModelBadgeLabel(modelBadge.model)}
           modelPreset={activeModelPreset}
           modelPresets={modelPresetOptions}
           onModelPresetChange={handleModelPresetChange}

webui/src/lib/types.ts

@@ -1313,7 +1313,6 @@ export type InboundEvent =
       chat_id: string;
       model_name: string;
       model_preset?: string | null;
-      is_fallback?: boolean;
     }
   | ({
       event: "turn_end";

webui/src/tests/nanobot-client.test.ts

@@ -1724,7 +1724,6 @@ describe("NanobotClient", () => {
       chat_id: "chat-a",
       model_name: "deepseek/deepseek-chat",
       model_preset: "Deep Research",
-      is_fallback: true,
     });
 
     expect(chatHandler).toHaveBeenCalledWith({
@@ -1732,7 +1731,6 @@ describe("NanobotClient", () => {
       chat_id: "chat-a",
       model_name: "deepseek/deepseek-chat",
       model_preset: "Deep Research",
-      is_fallback: true,
     });
   });
 

webui/src/tests/thread-shell.test.tsx

@@ -720,7 +720,6 @@ describe("ThreadShell", () => {
         event: "turn_model_updated",
         chat_id: "fallback-model",
         model_name: "openai-codex/gpt-5.5",
-        is_fallback: false,
       });
     });
 
@@ -731,7 +730,6 @@ describe("ThreadShell", () => {
         event: "turn_model_updated",
         chat_id: "fallback-model",
         model_name: "deepseek/deepseek-chat",
-        is_fallback: true,
       });
     });