feat: per-user assistant name and system prompt customization

Each user can rename the AI assistant and edit their own system prompt in Settings.

src/app/api/agent/chat/route.ts

@@ -1,7 +1,7 @@
 import { z } from "zod";
 import { apiError, apiJson } from "@/lib/api-handler";
 import { resolveApiAuth } from "@/lib/api-auth";
-import { getAssistantEnabled } from "@/lib/assistant-preference";
+import { getAssistantPreferences, resolveAssistantSystemPrompt } from "@/lib/assistant-preference";
 import { isLlmConfigured } from "@/lib/llm";
 import { encodeSseEvent } from "@/modules/agent/server/progress";
 import { runAgentChat } from "@/modules/agent/server/run";
@@ -25,11 +25,13 @@ export async function POST(request: Request) {
     return apiError("Unauthorized", 401);
   }
 
-  const assistantEnabled = await getAssistantEnabled(auth.userId);
-  if (!assistantEnabled) {
+  const assistant = await getAssistantPreferences(auth.userId);
+  if (!assistant.enabled) {
     return apiError("Assistant not enabled", 403);
   }
 
+  const systemPrompt = resolveAssistantSystemPrompt(assistant.systemPrompt);
+
   let body: unknown;
   try {
     body = await request.json();
@@ -54,6 +56,7 @@ export async function POST(request: Request) {
           const result = await runAgentChat({
             messages: parsed.data.messages,
             request,
+            systemPrompt,
             onProgress: send,
           });
 
@@ -87,6 +90,7 @@ export async function POST(request: Request) {
     const result = await runAgentChat({
       messages: parsed.data.messages,
       request,
+      systemPrompt,
     });
 
     return apiJson({

src/app/layout.tsx

@@ -18,6 +18,7 @@ import { InstallPrompt } from "@/components/install-prompt";
 import { AppShell } from "@/components/app-shell";
 import { AppToaster } from "@/components/app-toaster";
 import { AssistantBubble } from "@/modules/agent/components/assistant-bubble";
+import { DEFAULT_ASSISTANT_NAME } from "@/lib/assistant-config";
 import { isLlmConfigured } from "@/lib/llm";
 import { DEFAULT_THEME, navStyleToDataNav } from "@/modules/_core/themes";
 import type { Palette, ThemeMode, FontPair, Density, NavStyle } from "@/modules/_core/themes";
@@ -102,6 +103,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
   let userDashboards: DashboardMeta[] = [];
   let signedIn = false;
   let assistantEnabled = false;
+  let assistantName = DEFAULT_ASSISTANT_NAME;
 
   const session = await auth();
   if (session?.user?.id) {
@@ -114,6 +116,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
         themeDensity: users.themeDensity,
         themeNavStyle: users.themeNavStyle,
         assistantEnabled: users.assistantEnabled,
+        assistantName: users.assistantName,
       })
       .from(users)
       .where(eq(users.id, session.user.id))
@@ -125,6 +128,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
       density = row.themeDensity as Density;
       navStyle = row.themeNavStyle as NavStyle;
       assistantEnabled = row.assistantEnabled;
+      assistantName = row.assistantName?.trim() || DEFAULT_ASSISTANT_NAME;
     }
     userDashboards = await db
       .select({
@@ -178,7 +182,11 @@ export default async function RootLayout({ children }: { children: React.ReactNo
           <InstallPrompt />
           <PwaRegister />
           {signedIn && assistantEnabled && session?.user?.id ? (
-            <AssistantBubble configured={isLlmConfigured()} userId={session.user.id} />
+            <AssistantBubble
+              configured={isLlmConfigured()}
+              userId={session.user.id}
+              assistantName={assistantName}
+            />
           ) : null}
           <AppToaster position="bottom-right" />
         </QuickAddProvider>

src/app/settings/assistant-actions.ts

@@ -2,13 +2,58 @@
 
 import { eq } from "drizzle-orm";
 import { revalidatePath } from "next/cache";
+import { z } from "zod";
 import { db } from "@/lib/db";
+import {
+  DEFAULT_ASSISTANT_NAME,
+  MAX_ASSISTANT_NAME_LENGTH,
+  MAX_ASSISTANT_SYSTEM_PROMPT_LENGTH,
+} from "@/lib/assistant-config";
 import { users } from "@/modules/_core/schema";
 import { getCurrentSession } from "@/lib/session";
 
+const assistantNameSchema = z
+  .string()
+  .trim()
+  .min(1, "Name is required")
+  .max(MAX_ASSISTANT_NAME_LENGTH);
+
+const assistantSystemPromptSchema = z
+  .string()
+  .trim()
+  .min(1, "Prompt cannot be empty")
+  .max(MAX_ASSISTANT_SYSTEM_PROMPT_LENGTH);
+
+function revalidateAssistantSurfaces() {
+  revalidatePath("/settings");
+  revalidatePath("/", "layout");
+}
+
 export async function setAssistantEnabled(enabled: boolean): Promise<void> {
   const { user } = await getCurrentSession();
   await db.update(users).set({ assistantEnabled: enabled }).where(eq(users.id, user.id));
-  revalidatePath("/settings");
-  revalidatePath("/", "layout");
+  revalidateAssistantSurfaces();
+}
+
+export async function setAssistantName(name: string): Promise<void> {
+  const parsed = assistantNameSchema.parse(name);
+  const { user } = await getCurrentSession();
+  await db.update(users).set({ assistantName: parsed }).where(eq(users.id, user.id));
+  revalidateAssistantSurfaces();
+}
+
+export async function setAssistantSystemPrompt(prompt: string | null): Promise<void> {
+  const { user } = await getCurrentSession();
+  const normalized = prompt === null ? null : assistantSystemPromptSchema.parse(prompt);
+
+  await db.update(users).set({ assistantSystemPrompt: normalized }).where(eq(users.id, user.id));
+  revalidateAssistantSurfaces();
+}
+
+export async function resetAssistantName(): Promise<void> {
+  await setAssistantName(DEFAULT_ASSISTANT_NAME);
+}
+
+export async function resetAssistantSystemPrompt(): Promise<void> {
+  await setAssistantSystemPrompt(null);
 }

src/app/settings/page.tsx

@@ -13,7 +13,8 @@ import { AvatarFallbackWithName } from "@/components/avatar-fallback";
 import { revokeShareLinkAction } from "./actions";
 import { getHouseholdApiTokenStatus } from "@/modules/_core/api-token";
 import { ApiTokenSettings } from "@/components/api-token-settings";
-import { AssistantOptIn } from "@/components/assistant-opt-in";
+import { AssistantSettings } from "@/components/assistant-settings";
+import { AGENT_SYSTEM_PROMPT } from "@/modules/agent/tools";
 import { DefaultEventRemindersSetting } from "@/components/default-event-reminders-setting";
 import { listCalendars } from "@/modules/calendar/server/queries";
 import { listLists } from "@/modules/lists/server/queries";
@@ -322,6 +323,8 @@ function AppearanceSection({
     themeCalView: string;
     themeNavStyle: string;
     assistantEnabled: boolean;
+    assistantName: string;
+    assistantSystemPrompt: string | null;
   };
 }) {
   return (
@@ -355,7 +358,12 @@ function AppearanceSection({
           <MessageCircle className="size-4 text-[var(--ink-mute)]" />
         </CardHeader>
         <CardContent>
-          <AssistantOptIn enabled={user.assistantEnabled} />
+          <AssistantSettings
+            enabled={user.assistantEnabled}
+            name={user.assistantName}
+            systemPrompt={user.assistantSystemPrompt}
+            defaultSystemPrompt={AGENT_SYSTEM_PROMPT}
+          />
         </CardContent>
       </Card>
     </>