chat: remember last model

docs/api/rest.md

@@ -111,6 +111,7 @@ Behavior notes:
 - If `chatId` is present, server validates chat existence.
 - For `chatId` calls, server stores only *new* non-assistant messages from provided history to avoid duplicates.
 - Server persists final assistant output and call metadata (`LlmCall`) in DB.
+- Server updates chat-level model metadata on each call: `lastUsedProvider`/`lastUsedModel`; first successful/failed call also initializes `initiatedProvider`/`initiatedModel` if unset.
 
 ## Searches
 
@@ -151,7 +152,16 @@ Search run notes:
 
 `ChatSummary`
 ```json
-{ "id": "...", "title": null, "createdAt": "...", "updatedAt": "..." }
+{
+  "id": "...",
+  "title": null,
+  "createdAt": "...",
+  "updatedAt": "...",
+  "initiatedProvider": "openai|anthropic|xai|null",
+  "initiatedModel": "string|null",
+  "lastUsedProvider": "openai|anthropic|xai|null",
+  "lastUsedModel": "string|null"
+}
 ```
 
 `Message`
@@ -172,6 +182,10 @@ Search run notes:
   "title": null,
   "createdAt": "...",
   "updatedAt": "...",
+  "initiatedProvider": "openai|anthropic|xai|null",
+  "initiatedModel": "string|null",
+  "lastUsedProvider": "openai|anthropic|xai|null",
+  "lastUsedModel": "string|null",
   "messages": [Message]
 }
 ```

server/prisma/migrations/20260214113000_add_chat_model_memory/migration.sql

@@ -0,0 +1,5 @@
+-- AlterTable
+ALTER TABLE "Chat" ADD COLUMN "initiatedProvider" TEXT;
+ALTER TABLE "Chat" ADD COLUMN "initiatedModel" TEXT;
+ALTER TABLE "Chat" ADD COLUMN "lastUsedProvider" TEXT;
+ALTER TABLE "Chat" ADD COLUMN "lastUsedModel" TEXT;

server/prisma/schema.prisma

@@ -45,6 +45,11 @@ model Chat {
 
   title String?
 
+  initiatedProvider Provider?
+  initiatedModel    String?
+  lastUsedProvider  Provider?
+  lastUsedModel     String?
+
   user   User?   @relation(fields: [userId], references: [id])
   userId String?
 

server/src/llm/multiplexer.ts

@@ -10,11 +10,12 @@ function asProviderEnum(p: Provider) {
 
 export async function runMultiplex(req: MultiplexRequest): Promise<MultiplexResponse> {
   const t0 = performance.now();
+  const chatId = req.chatId ?? (await prisma.chat.create({ data: {}, select: { id: true } })).id;
 
   // Persist call record early so we can attach errors.
   const call = await prisma.llmCall.create({
     data: {
-      chatId: req.chatId ?? (await prisma.chat.create({ data: {} })).id,
+      chatId,
       provider: asProviderEnum(req.provider) as any,
       model: req.model,
       request: req as any,
@@ -22,6 +23,23 @@ export async function runMultiplex(req: MultiplexRequest): Promise<MultiplexResp
     select: { id: true, chatId: true },
   });
 
+  await prisma.$transaction([
+    prisma.chat.update({
+      where: { id: chatId },
+      data: {
+        lastUsedProvider: asProviderEnum(req.provider) as any,
+        lastUsedModel: req.model,
+      },
+    }),
+    prisma.chat.updateMany({
+      where: { id: chatId, initiatedProvider: null },
+      data: {
+        initiatedProvider: asProviderEnum(req.provider) as any,
+        initiatedModel: req.model,
+      },
+    }),
+  ]);
+
   try {
     let outText = "";
     let usage: MultiplexResponse["usage"] | undefined;

server/src/llm/streaming.ts

@@ -29,6 +29,23 @@ export async function* runMultiplexStream(req: MultiplexRequest): AsyncGenerator
     select: { id: true },
   });
 
+  await prisma.$transaction([
+    prisma.chat.update({
+      where: { id: chatId },
+      data: {
+        lastUsedProvider: req.provider as any,
+        lastUsedModel: req.model,
+      },
+    }),
+    prisma.chat.updateMany({
+      where: { id: chatId, initiatedProvider: null },
+      data: {
+        initiatedProvider: req.provider as any,
+        initiatedModel: req.model,
+      },
+    }),
+  ]);
+
   yield { type: "meta", chatId, callId: call.id, provider: req.provider, model: req.model };
 
   let text = "";

server/src/routes.ts

@@ -174,7 +174,16 @@ export async function registerRoutes(app: FastifyInstance) {
     const chats = await prisma.chat.findMany({
       orderBy: { updatedAt: "desc" },
       take: 100,
-      select: { id: true, title: true, createdAt: true, updatedAt: true },
+      select: {
+        id: true,
+        title: true,
+        createdAt: true,
+        updatedAt: true,
+        initiatedProvider: true,
+        initiatedModel: true,
+        lastUsedProvider: true,
+        lastUsedModel: true,
+      },
     });
     return { chats };
   });
@@ -183,7 +192,19 @@ export async function registerRoutes(app: FastifyInstance) {
     requireAdmin(req);
     const Body = z.object({ title: z.string().optional() });
     const body = Body.parse(req.body ?? {});
-    const chat = await prisma.chat.create({ data: { title: body.title } });
+    const chat = await prisma.chat.create({
+      data: { title: body.title },
+      select: {
+        id: true,
+        title: true,
+        createdAt: true,
+        updatedAt: true,
+        initiatedProvider: true,
+        initiatedModel: true,
+        lastUsedProvider: true,
+        lastUsedModel: true,
+      },
+    });
     return { chat };
   });
 
@@ -203,7 +224,16 @@ export async function registerRoutes(app: FastifyInstance) {
 
     const chat = await prisma.chat.findUnique({
       where: { id: chatId },
-      select: { id: true, title: true, createdAt: true, updatedAt: true },
+      select: {
+        id: true,
+        title: true,
+        createdAt: true,
+        updatedAt: true,
+        initiatedProvider: true,
+        initiatedModel: true,
+        lastUsedProvider: true,
+        lastUsedModel: true,
+      },
     });
     if (!chat) return app.httpErrors.notFound("chat not found");
     return { chat };
@@ -219,7 +249,16 @@ export async function registerRoutes(app: FastifyInstance) {
 
     const existing = await prisma.chat.findUnique({
       where: { id: body.chatId },
-      select: { id: true, title: true, createdAt: true, updatedAt: true },
+      select: {
+        id: true,
+        title: true,
+        createdAt: true,
+        updatedAt: true,
+        initiatedProvider: true,
+        initiatedModel: true,
+        lastUsedProvider: true,
+        lastUsedModel: true,
+      },
     });
     if (!existing) return app.httpErrors.notFound("chat not found");
     if (existing.title?.trim()) return { chat: existing };
@@ -231,7 +270,16 @@ export async function registerRoutes(app: FastifyInstance) {
     const chat = await prisma.chat.update({
       where: { id: body.chatId },
       data: { title },
-      select: { id: true, title: true, createdAt: true, updatedAt: true },
+      select: {
+        id: true,
+        title: true,
+        createdAt: true,
+        updatedAt: true,
+        initiatedProvider: true,
+        initiatedModel: true,
+        lastUsedProvider: true,
+        lastUsedModel: true,
+      },
     });
 
     return { chat };

web/src/App.tsx

@@ -37,6 +37,10 @@ type SidebarItem = SidebarSelection & {
   title: string;
   updatedAt: string;
   createdAt: string;
+  initiatedProvider: Provider | null;
+  initiatedModel: string | null;
+  lastUsedProvider: Provider | null;
+  lastUsedModel: string | null;
 };
 type ContextMenuState = {
   item: SidebarSelection;
@@ -89,11 +93,26 @@ function loadStoredModelPreferences() {
 }
 
 function pickProviderModel(options: string[], preferred: string | null, fallback: string | null = null) {
-  if (preferred && options.includes(preferred)) return preferred;
   if (fallback && options.includes(fallback)) return fallback;
+  if (preferred && options.includes(preferred)) return preferred;
   return options[0] ?? "";
 }
 
+function getProviderLabel(provider: Provider | null | undefined) {
+  if (provider === "openai") return "OpenAI";
+  if (provider === "anthropic") return "Anthropic";
+  if (provider === "xai") return "xAI";
+  return "";
+}
+
+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 ModelComboboxProps = {
   options: string[];
   value: string;
@@ -212,6 +231,10 @@ function buildSidebarItems(chats: ChatSummary[], searches: SearchSummary[]): Sid
       title: getChatTitle(chat),
       updatedAt: chat.updatedAt,
       createdAt: chat.createdAt,
+      initiatedProvider: chat.initiatedProvider,
+      initiatedModel: chat.initiatedModel,
+      lastUsedProvider: chat.lastUsedProvider,
+      lastUsedModel: chat.lastUsedModel,
     })),
     ...searches.map((search) => ({
       kind: "search" as const,
@@ -219,6 +242,10 @@ function buildSidebarItems(chats: ChatSummary[], searches: SearchSummary[]): Sid
       title: getSearchTitle(search),
       updatedAt: search.updatedAt,
       createdAt: search.createdAt,
+      initiatedProvider: null,
+      initiatedModel: null,
+      lastUsedProvider: null,
+      lastUsedModel: null,
     })),
   ];
 
@@ -473,6 +500,16 @@ export default function App() {
     return searches.find((search) => search.id === selectedItem.id) ?? null;
   }, [searches, selectedItem]);
 
+  useEffect(() => {
+    if (draftKind || selectedItem?.kind !== "chat") return;
+    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]);
+
   const selectedTitle = useMemo(() => {
     if (draftKind === "chat") return "New chat";
     if (draftKind === "search") return "New search";
@@ -611,6 +648,10 @@ export default function App() {
         title: chat.title,
         createdAt: chat.createdAt,
         updatedAt: chat.updatedAt,
+        initiatedProvider: chat.initiatedProvider,
+        initiatedModel: chat.initiatedModel,
+        lastUsedProvider: chat.lastUsedProvider,
+        lastUsedModel: chat.lastUsedModel,
         messages: [],
       });
       setSelectedSearch(null);
@@ -937,6 +978,9 @@ export default function App() {
             ) : null}
             {sidebarItems.map((item) => {
               const active = selectedItem?.kind === item.kind && selectedItem.id === item.id;
+              const initiatedLabel = item.kind === "chat" && item.initiatedModel
+                ? `${getProviderLabel(item.initiatedProvider)}${item.initiatedProvider ? " · " : ""}${item.initiatedModel}`
+                : null;
               return (
                 <button
                   key={`${item.kind}-${item.id}`}
@@ -956,7 +1000,12 @@ export default function App() {
                     {item.kind === "chat" ? <MessageSquare className="h-3.5 w-3.5" /> : <Search className="h-3.5 w-3.5" />}
                     <p className="truncate text-sm font-medium">{item.title}</p>
                   </div>
-                  <p className={cn("mt-1 text-xs", active ? "text-violet-100/90" : "text-violet-300/60")}>{formatDate(item.updatedAt)}</p>
+                  <div className="mt-1 flex items-center gap-2 text-xs">
+                    <p className={cn("shrink-0", active ? "text-violet-100/90" : "text-violet-300/60")}>{formatDate(item.updatedAt)}</p>
+                    {initiatedLabel ? (
+                      <p className={cn("ml-auto truncate text-right", active ? "text-violet-200/65" : "text-violet-300/45")}>{initiatedLabel}</p>
+                    ) : null}
+                  </div>
                 </button>
               );
             })}

web/src/lib/api.ts

@@ -3,6 +3,10 @@ export type ChatSummary = {
   title: string | null;
   createdAt: string;
   updatedAt: string;
+  initiatedProvider: Provider | null;
+  initiatedModel: string | null;
+  lastUsedProvider: Provider | null;
+  lastUsedModel: string | null;
 };
 
 export type SearchSummary = {
@@ -26,6 +30,10 @@ export type ChatDetail = {
   title: string | null;
   createdAt: string;
   updatedAt: string;
+  initiatedProvider: Provider | null;
+  initiatedModel: string | null;
+  lastUsedProvider: Provider | null;
+  lastUsedModel: string | null;
   messages: Message[];
 };