Preserve provider changes before sending

web/src/App.tsx

@@ -63,6 +63,10 @@ import {
   type WorkspaceItem,
 } from "@/lib/api";
 import { useSessionAuth } from "@/hooks/use-session-auth";
+import {
+  getChatModelSelection,
+  getChatModelSelectionSyncKey,
+} from "@/lib/chat-model-selection";
 import {
   resolveSidebarSelectionAfterRefresh,
   type SidebarSelection,
@@ -545,14 +549,6 @@ function normalizeEnabledTools(value: unknown, availableTools: ChatToolInfo[]) {
   );
 }
 
-function getChatModelSelection(chat: Pick<ChatSummary, "lastUsedProvider" | "lastUsedModel"> | Pick<ChatDetail, "lastUsedProvider" | "lastUsedModel"> | null) {
-  if (!chat?.lastUsedProvider || !chat.lastUsedModel?.trim()) return null;
-  return {
-    provider: chat.lastUsedProvider,
-    model: chat.lastUsedModel.trim(),
-  };
-}
-
 type ToolLogMetadata = {
   kind: "tool_call";
   toolCallId?: string;
@@ -1562,15 +1558,32 @@ export default function App() {
     return searches.find((search) => search.id === selectedItem.id) ?? null;
   }, [searches, selectedItem]);
 
-  useEffect(() => {
-    if (draftKind || selectedItem?.kind !== "chat") return;
+  const selectedChatModelSelection = useMemo(() => {
+    if (draftKind || selectedItem?.kind !== "chat") return null;
     const detailSelection = selectedChat?.id === selectedItem.id ? getChatModelSelection(selectedChat) : null;
     const summarySelection = getChatModelSelection(selectedChatSummary);
-    const nextSelection = detailSelection ?? summarySelection;
-    if (!nextSelection) return;
-    setProvider(nextSelection.provider);
-    setModel(nextSelection.model);
-  }, [draftKind, selectedChat, selectedChatSummary, selectedItem]);
+    return detailSelection ?? summarySelection;
+  }, [
+    draftKind,
+    selectedChat?.id,
+    selectedChat?.lastUsedModel,
+    selectedChat?.lastUsedProvider,
+    selectedChatSummary?.id,
+    selectedChatSummary?.lastUsedModel,
+    selectedChatSummary?.lastUsedProvider,
+    selectedItem?.id,
+    selectedItem?.kind,
+  ]);
+  const selectedChatModelSelectionSyncKey = getChatModelSelectionSyncKey(
+    selectedItem?.kind === "chat" ? selectedItem.id : null,
+    selectedChatModelSelection
+  );
+
+  useEffect(() => {
+    if (!selectedChatModelSelection) return;
+    setProvider(selectedChatModelSelection.provider);
+    setModel(selectedChatModelSelection.model);
+  }, [selectedChatModelSelectionSyncKey]);
 
   useEffect(() => {
     if (draftKind === "chat") return;

web/src/lib/chat-model-selection.ts

@@ -0,0 +1,24 @@
+import type { Provider } from "./api";
+
+type PersistedChatModel = {
+  lastUsedProvider: Provider | null;
+  lastUsedModel: string | null;
+};
+
+export type ChatModelSelection = {
+  provider: Provider;
+  model: string;
+};
+
+export function getChatModelSelection(chat: PersistedChatModel | null): ChatModelSelection | null {
+  if (!chat?.lastUsedProvider || !chat.lastUsedModel?.trim()) return null;
+  return {
+    provider: chat.lastUsedProvider,
+    model: chat.lastUsedModel.trim(),
+  };
+}
+
+export function getChatModelSelectionSyncKey(chatId: string | null, selection: ChatModelSelection | null) {
+  if (!chatId || !selection) return null;
+  return JSON.stringify([chatId, selection.provider, selection.model]);
+}

web/tests/chat-model-selection.test.mjs

@@ -0,0 +1,49 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import {
+  getChatModelSelection,
+  getChatModelSelectionSyncKey,
+} from "../src/lib/chat-model-selection.ts";
+
+test("chat model selections are normalized from persisted metadata", () => {
+  assert.deepEqual(
+    getChatModelSelection({
+      lastUsedProvider: "anthropic",
+      lastUsedModel: "  claude-sonnet-4-5  ",
+    }),
+    {
+      provider: "anthropic",
+      model: "claude-sonnet-4-5",
+    }
+  );
+});
+
+test("unrelated chat updates do not change the model synchronization key", () => {
+  const beforeSettingsSave = getChatModelSelection({
+    lastUsedProvider: "openai",
+    lastUsedModel: "gpt-4.1-mini",
+  });
+  const afterSettingsSave = getChatModelSelection({
+    lastUsedProvider: "openai",
+    lastUsedModel: "gpt-4.1-mini",
+  });
+
+  assert.equal(
+    getChatModelSelectionSyncKey("chat-1", beforeSettingsSave),
+    getChatModelSelectionSyncKey("chat-1", afterSettingsSave)
+  );
+});
+
+test("switching chats or persisted models changes the synchronization key", () => {
+  const original = { provider: "openai", model: "gpt-4.1-mini" };
+  const updated = { provider: "gemini", model: "gemini-3.5-flash" };
+
+  assert.notEqual(
+    getChatModelSelectionSyncKey("chat-1", original),
+    getChatModelSelectionSyncKey("chat-2", original)
+  );
+  assert.notEqual(
+    getChatModelSelectionSyncKey("chat-1", original),
+    getChatModelSelectionSyncKey("chat-1", updated)
+  );
+});

web/tsconfig.tsbuildinfo

@@ -1 +1 @@
-{"root":["./src/App.tsx","./src/main.tsx","./src/pwa.ts","./src/root-router.tsx","./src/vite-env.d.ts","./src/components/sybil-character.tsx","./src/components/auth/auth-screen.tsx","./src/components/chat/chat-attachment-list.tsx","./src/components/chat/chat-messages-panel.tsx","./src/components/markdown/markdown-content.tsx","./src/components/search/search-results-panel.tsx","./src/components/ui/button.tsx","./src/components/ui/input.tsx","./src/components/ui/scroll-area.tsx","./src/components/ui/separator.tsx","./src/components/ui/textarea.tsx","./src/hooks/use-session-auth.ts","./src/lib/api.ts","./src/lib/sidebar-selection.ts","./src/lib/utils.ts","./src/pages/search-route-page.tsx"],"version":"5.9.3"}
+{"root":["./src/App.tsx","./src/main.tsx","./src/pwa.ts","./src/root-router.tsx","./src/vite-env.d.ts","./src/components/sybil-character.tsx","./src/components/auth/auth-screen.tsx","./src/components/chat/chat-attachment-list.tsx","./src/components/chat/chat-messages-panel.tsx","./src/components/markdown/markdown-content.tsx","./src/components/search/search-results-panel.tsx","./src/components/ui/button.tsx","./src/components/ui/input.tsx","./src/components/ui/scroll-area.tsx","./src/components/ui/separator.tsx","./src/components/ui/textarea.tsx","./src/hooks/use-session-auth.ts","./src/lib/api.ts","./src/lib/chat-model-selection.ts","./src/lib/sidebar-selection.ts","./src/lib/utils.ts","./src/pages/search-route-page.tsx"],"version":"5.9.3"}