model selector

src/app/admin/chat/_components/ModelSelector.tsx

@@ -0,0 +1,48 @@
+'use client'
+import { trpc } from '~/app/_trpc/Client'
+import {
+	Select,
+	SelectContent,
+	SelectItem,
+	SelectTrigger,
+	SelectValue,
+} from '~/components/ui/select'
+
+export default function ModelSelector({ initialValue }: { initialValue: string }) {
+	const utils = trpc.useUtils()
+	const { data: models, isLoading, error } = trpc.chat.listModels.useQuery()
+	const { data: model = initialValue } = trpc.chat.getModel.useQuery(undefined, {
+		initialData: initialValue,
+	})
+
+	const mutation = trpc.chat.updateModel.useMutation({
+		onSuccess: () => utils.chat.getModel.invalidate(),
+	})
+
+	// Ensure the currently-saved model is always selectable, even if the
+	// OpenAI list doesn't include it (e.g. a deprecated model).
+	const options = Array.from(new Set([model, ...(models ?? [])])).filter(Boolean)
+
+	return (
+		<div className="flex flex-col gap-2">
+			<Select value={model} onValueChange={(v) => mutation.mutate({ model: v })}>
+				<SelectTrigger className="w-72">
+					<SelectValue placeholder={isLoading ? 'Loading models…' : 'Select a model'} />
+				</SelectTrigger>
+				<SelectContent>
+					{options.map((id) => (
+						<SelectItem key={id} value={id}>
+							{id}
+						</SelectItem>
+					))}
+				</SelectContent>
+			</Select>
+			<div className="flex items-center gap-3 text-sm text-muted-foreground">
+				{mutation.isPending && <span>Saving…</span>}
+				{mutation.isSuccess && !mutation.isPending && <span>Saved</span>}
+				{error && <span className="text-destructive">Failed to load models: {error.message}</span>}
+				{mutation.error && <span className="text-destructive">{mutation.error.message}</span>}
+			</div>
+		</div>
+	)
+}

src/app/admin/chat/page.tsx

@@ -1,11 +1,23 @@
 import { servTrpc } from '~/app/_trpc/ServerClient'
 import SystemPromptForm from './_components/SystemPromptForm'
+import ModelSelector from './_components/ModelSelector'
 
 export default async function SystemPromptPage() {
 	const prompt = await servTrpc.chat.getSystemPrompt()
+	const model = await servTrpc.chat.getModel()
 
 	return (
-		<div className="w-full max-w-2xl p-6 flex flex-col gap-4">
+		<div className="w-full max-w-2xl p-6 flex flex-col gap-8">
+			<div className="flex flex-col gap-4">
+				<div>
+					<h1 className="text-lg font-semibold">AI Model</h1>
+					<p className="text-sm text-muted-foreground">
+						The OpenAI model used to respond to chat requests.
+					</p>
+				</div>
+				<ModelSelector initialValue={model} />
+			</div>
+			<div className="flex flex-col gap-4">
 				<div>
 					<h1 className="text-lg font-semibold">AI System Prompt</h1>
 					<p className="text-sm text-muted-foreground">
@@ -14,5 +26,6 @@ export default async function SystemPromptPage() {
 				</div>
 				<SystemPromptForm initialValue={prompt} />
 			</div>
+		</div>
 	)
 }

src/app/api/chat/route.ts

@@ -32,6 +32,7 @@ export async function POST(req: Request) {
 	if (!session) return new Response('Session not found', { status: 404 })
 
 	const systemPrompt = await servTrpc.chat.getSystemPrompt() || 'You are an AI recruiter assistant.'
+	const model = await servTrpc.chat.getModel()
 
 	// Save the latest user message
 	const lastMessage = messages[messages.length - 1]
@@ -46,7 +47,7 @@ export async function POST(req: Request) {
 	}
 
 	const result = streamText({
-		model: openai('gpt-5-mini'),
+		model: openai(model),
 		system: systemPrompt,
 		messages: await convertToModelMessages(messages),
 		tools: {

src/server/dbschema/schema.ts

@@ -175,6 +175,7 @@ export const chatMessageRelations = relations(chatMessage, ({ one }) => ({
 export const systemSettings = createTable(
 	"systemSetting",
 	(d) => ({
-		systemPropmt: d.text()
+		systemPropmt: d.text(),
+		model: d.text()
 	})
 )

src/server/routers/chat.ts

@@ -7,6 +7,26 @@ import { isAdmin } from '~/app/actions';
 import { z } from 'zod';
 import { eq } from 'drizzle-orm';
 import { clerkClient, auth } from '@clerk/nextjs/server'
+import { env } from '~/env'
+
+export const DEFAULT_MODEL = 'gpt-5-mini'
+
+// Models returned by the OpenAI API that aren't usable for chat completions.
+const NON_CHAT_MODEL = /embedding|image|audio|realtime|transcribe|tts|whisper|moderation|dall-e|search|codex|instruct/
+
+async function readSettings() {
+	return db.select().from(systemSettings).limit(1).then((r) => r[0])
+}
+
+async function writeSettings(values: { systemPropmt?: string | null; model?: string | null }) {
+	const current = await readSettings()
+	await db.delete(systemSettings)
+	await db.insert(systemSettings).values({
+		systemPropmt: values.systemPropmt ?? current?.systemPropmt ?? null,
+		model: values.model ?? current?.model ?? null,
+	})
+}
+
 export const chatRouter = router({
   getSession: publicProcedure.query(async () => {
     const { userId } = await auth();
@@ -66,13 +86,34 @@ export const chatRouter = router({
 
   }),
   getSystemPrompt: publicProcedure.query(async () => {
-    const row = await db.select().from(systemSettings).limit(1).then((r) => r[0])
+    const row = await readSettings()
     return row?.systemPropmt ?? ''
   }),
   updateSystemPrompt: publicProcedure.input(z.object({ prompt: z.string() })).mutation(async ({ input }) => {
     if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
-    await db.delete(systemSettings)
-    await db.insert(systemSettings).values({ systemPropmt: input.prompt })
+    await writeSettings({ systemPropmt: input.prompt })
+  }),
+  getModel: publicProcedure.query(async () => {
+    const row = await readSettings()
+    return row?.model ?? DEFAULT_MODEL
+  }),
+  listModels: publicProcedure.query(async () => {
+    if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
+    const res = await fetch('https://api.openai.com/v1/models', {
+      headers: { Authorization: `Bearer ${env.OPENAI_API_KEY}` },
+    })
+    if (!res.ok) {
+      throw new TRPCError({ code: 'INTERNAL_SERVER_ERROR', message: `failed to fetch models (${res.status})` })
+    }
+    const json = (await res.json()) as { data: { id: string }[] }
+    return json.data
+      .map((m) => m.id)
+      .filter((id) => (id.startsWith('gpt') || /^o\d/.test(id) || id.startsWith('chatgpt')) && !NON_CHAT_MODEL.test(id))
+      .sort()
+  }),
+  updateModel: publicProcedure.input(z.object({ model: z.string() })).mutation(async ({ input }) => {
+    if (!(await isAdmin())) throw new TRPCError({ code: 'FORBIDDEN' })
+    await writeSettings({ model: input.model })
   }),
 })