From fb36a01ffe609c16db8fbf8d03f395aa040c86ed Mon Sep 17 00:00:00 2001
From: Matteo Celani <26189482+matteocelani@users.noreply.github.com>
Date: Tue, 21 Apr 2026 21:08:06 +0200
Subject: [PATCH] app/ui: fix model picker showing stale model after switching
 chats (#15280)

* app/ui: fix model picker showing stale model after switching chats

Optimistic messages created during streaming were storing the full
Model object instead of the model name string. When switching back
to a chat with cached streaming data, the restore effect read an
object where it expected a string, causing the model picker to fail
matching and remain stuck on the previous chat's model.

* app/ui: fix two more instances of Model object passed as model name

Fix the same bug at lines 523 and 536 in the assistant_with_tools
event handler, where selectedModel (object) was used instead of
selectedModel.model (string).
---
 app/ui/app/src/hooks/useChats.ts | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/app/ui/app/src/hooks/useChats.ts b/app/ui/app/src/hooks/useChats.ts
index 2493e5bee..5aac35285 100644
--- a/app/ui/app/src/hooks/useChats.ts
+++ b/app/ui/app/src/hooks/useChats.ts
@@ -381,7 +381,7 @@ export const useSendMessage = (chatId: string) => {
                     role: "assistant",
                     content: "",
                     thinking: "",
-                    model: effectiveModel,
+                    model: effectiveModel.model,
                   }),
                 );
                 lastMessage = newMessages[newMessages.length - 1];
@@ -433,7 +433,7 @@ export const useSendMessage = (chatId: string) => {
                     role: "assistant",
                     content: "",
                     thinking: "",
-                    model: effectiveModel,
+                    model: effectiveModel.model,
                   }),
                 );
                 lastMessage = newMessages[newMessages.length - 1];
@@ -520,7 +520,7 @@ export const useSendMessage = (chatId: string) => {
                     thinkingTimeStart:
                       lastMessage.thinkingTimeStart || event.thinkingTimeStart,
                     thinkingTimeEnd: event.thinkingTimeEnd,
-                    model: selectedModel,
+                    model: selectedModel.model,
                   });
                   newMessages[newMessages.length - 1] = updatedMessage;
                 } else {
@@ -533,7 +533,7 @@ export const useSendMessage = (chatId: string) => {
                       tool_calls: event.toolCalls,
                       thinkingTimeStart: event.thinkingTimeStart,
                       thinkingTimeEnd: event.thinkingTimeEnd,
-                      model: selectedModel,
+                      model: selectedModel.model,
                     }),
                   );
                 }
@@ -699,7 +699,7 @@ export const useSendMessage = (chatId: string) => {
             queryClient.setQueryData(["chat", newId], {
               chat: new Chat({
                 id: newId,
-                model: effectiveModel,
+                model: effectiveModel.model,
                 messages: [
                   new Message({
                     role: "user",