feat: multiple named conversations for the cooking assistant

The general assistant had exactly one conversation per user forever
(recipeId null on chat_messages) — no way to start fresh or organize
by topic. Adds an ai_conversations table (title, timestamps) and a
nullable conversationId FK on chat_messages; the assistant panel gets
a conversations menu to create/switch/rename/delete, auto-titling a
new conversation from its first question.

Per-recipe chat is untouched — each recipe already has one natural
thread, so multi-conversation support only applies to the homepage
assistant. Pre-existing general messages (no conversationId) aren't
migrated into the new model and won't appear in the conversation list.

Requires migration 0042 to run against a live DB — not applied in
this sandbox (no Docker here); run `pnpm db:migrate`.

v0.43.0

apps/web/app/api/v1/ai/chat-history/route.ts

@@ -5,6 +5,7 @@ import { requireSessionOrApiKey } from "@/lib/api-auth";
 
 const Schema = z.object({
   recipeId: z.string().uuid().optional(),
+  conversationId: z.string().uuid().optional(),
   // "general" restricts to the homepage cooking assistant (recipeId null);
   // omit both recipeId and scope to search across everything.
   scope: z.enum(["general"]).optional(),
@@ -19,6 +20,7 @@ export async function GET(req: NextRequest) {
   const { searchParams } = new URL(req.url);
   const parsed = Schema.safeParse({
     recipeId: searchParams.get("recipeId") ?? undefined,
+    conversationId: searchParams.get("conversationId") ?? undefined,
     scope: searchParams.get("scope") ?? undefined,
     q: searchParams.get("q") ?? undefined,
     limit: searchParams.get("limit") ?? undefined,
@@ -26,10 +28,11 @@ export async function GET(req: NextRequest) {
   if (!parsed.success) {
     return NextResponse.json({ error: "Validation error" }, { status: 400 });
   }
-  const { recipeId, scope, q, limit } = parsed.data;
+  const { recipeId, conversationId, scope, q, limit } = parsed.data;
 
   const conditions = [eq(chatMessages.userId, session!.user.id)];
   if (recipeId) conditions.push(eq(chatMessages.recipeId, recipeId));
+  else if (conversationId) conditions.push(eq(chatMessages.conversationId, conversationId));
   else if (scope === "general") conditions.push(isNull(chatMessages.recipeId));
   if (q?.trim()) conditions.push(ilike(chatMessages.content, `%${q.trim()}%`));
 

apps/web/app/api/v1/ai/conversations/[id]/route.ts

@@ -0,0 +1,45 @@
+import { NextRequest, NextResponse } from "next/server";
+import { z } from "zod";
+import { db, aiConversations, eq, and } from "@epicure/db";
+import { requireSessionOrApiKey } from "@/lib/api-auth";
+
+type Params = { params: Promise<{ id: string }> };
+
+const RenameSchema = z.object({ title: z.string().max(100).nullable() });
+
+export async function PATCH(req: NextRequest, { params }: Params) {
+  const { session, response } = await requireSessionOrApiKey(req);
+  if (response) return response;
+  const { id } = await params;
+
+  const body = await req.json() as unknown;
+  const parsed = RenameSchema.safeParse(body);
+  if (!parsed.success) {
+    return NextResponse.json({ error: "Validation error" }, { status: 400 });
+  }
+
+  const [updated] = await db
+    .update(aiConversations)
+    .set({ title: parsed.data.title?.trim() || null, updatedAt: new Date() })
+    .where(and(eq(aiConversations.id, id), eq(aiConversations.userId, session!.user.id)))
+    .returning();
+
+  if (!updated) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+  return NextResponse.json({ id: updated.id, title: updated.title });
+}
+
+export async function DELETE(req: NextRequest, { params }: Params) {
+  const { session, response } = await requireSessionOrApiKey(req);
+  if (response) return response;
+  const { id } = await params;
+
+  const [deleted] = await db
+    .delete(aiConversations)
+    .where(and(eq(aiConversations.id, id), eq(aiConversations.userId, session!.user.id)))
+    .returning({ id: aiConversations.id });
+
+  if (!deleted) return NextResponse.json({ error: "Not found" }, { status: 404 });
+
+  return NextResponse.json({ ok: true });
+}

apps/web/app/api/v1/ai/conversations/route.ts

@@ -0,0 +1,33 @@
+import { NextRequest, NextResponse } from "next/server";
+import { db, aiConversations, eq, desc } from "@epicure/db";
+import { requireSessionOrApiKey } from "@/lib/api-auth";
+
+export async function GET(req: NextRequest) {
+  const { session, response } = await requireSessionOrApiKey(req);
+  if (response) return response;
+
+  const rows = await db.query.aiConversations.findMany({
+    where: eq(aiConversations.userId, session!.user.id),
+    orderBy: desc(aiConversations.updatedAt),
+  });
+
+  return NextResponse.json({
+    data: rows.map((r) => ({
+      id: r.id,
+      title: r.title,
+      createdAt: r.createdAt.toISOString(),
+      updatedAt: r.updatedAt.toISOString(),
+    })),
+  });
+}
+
+export async function POST(req: NextRequest) {
+  const { session, response } = await requireSessionOrApiKey(req);
+  if (response) return response;
+
+  const id = crypto.randomUUID();
+  const now = new Date();
+  await db.insert(aiConversations).values({ id, userId: session!.user.id, title: null, createdAt: now, updatedAt: now });
+
+  return NextResponse.json({ id, title: null, createdAt: now.toISOString(), updatedAt: now.toISOString() }, { status: 201 });
+}

apps/web/app/api/v1/ai/cooking-chat/route.ts

@@ -1,7 +1,7 @@
 import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { generateText } from "ai";
-import { db, chatMessages } from "@epicure/db";
+import { db, chatMessages, aiConversations, sql } from "@epicure/db";
 import { requireSessionOrApiKey } from "@/lib/api-auth";
 import { applyRateLimit } from "@/lib/rate-limit";
 import { withAiQuota, resolveAiConfigOrError } from "@/lib/ai/ai-error";
@@ -11,6 +11,7 @@ import { getUserPrivateBio, buildUserBioContext } from "@/lib/ai/user-bio";
 
 const Schema = z.object({
   question: z.string().min(1).max(500),
+  conversationId: z.string().uuid().optional(),
 });
 
 const LANG: Record<string, string> = { en: "English", fr: "French" };
@@ -48,10 +49,24 @@ export async function POST(req: NextRequest) {
   );
   if (!result.ok) return result.response;
 
+  const { conversationId } = parsed.data;
+
   void db.insert(chatMessages).values([
-    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, role: "user", content: parsed.data.question },
-    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, role: "assistant", content: result.data.text },
+    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, conversationId, role: "user", content: parsed.data.question },
+    { id: crypto.randomUUID(), userId: session!.user.id, recipeId: null, conversationId, role: "assistant", content: result.data.text },
   ]).catch((err) => console.error("[cooking-chat] failed to persist chat history", err));
 
+  if (conversationId) {
+    // Bumps updatedAt (for the conversation list's sort order) and, only if
+    // this is the conversation's first message, auto-titles it from the
+    // opening question — so users aren't left staring at "Untitled" entries;
+    // they can still rename it later.
+    void db.execute(sql`
+      UPDATE ${aiConversations}
+      SET updated_at = now(), title = COALESCE(title, ${parsed.data.question.slice(0, 60)})
+      WHERE ${aiConversations.id} = ${conversationId} AND ${aiConversations.userId} = ${session!.user.id}
+    `).catch((err) => console.error("[cooking-chat] failed to touch conversation", err));
+  }
+
   return NextResponse.json({ answer: result.data.text });
 }