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,
             )