chat: remember last model

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 };