diff --git a/src/server/services/onboarding.service.ts b/src/server/services/onboarding.service.ts
new file mode 100644
index 0000000..5cac54d
--- /dev/null
+++ b/src/server/services/onboarding.service.ts
@@ -0,0 +1,122 @@
+import { eq, inArray } from "drizzle-orm";
+import { db as prodDb } from "../../db/index.ts";
+import { categories, globalItems, items, settings } from "../../db/schema.ts";
+
+type Db = typeof prodDb;
+
+interface OnboardingResult {
+	itemsCreated: number;
+	categoriesCreated: string[];
+}
+
+/**
+ * Complete onboarding by batch-creating user items from selected global catalog items.
+ * Auto-creates categories based on the global items' category field.
+ * Sets onboardingComplete setting to "true".
+ */
+export async function completeOnboarding(
+	db: Db = prodDb,
+	userId: number,
+	globalItemIds: number[],
+): Promise<OnboardingResult> {
+	if (globalItemIds.length === 0) {
+		// No items selected — just mark complete
+		await db
+			.insert(settings)
+			.values({ userId, key: "onboardingComplete", value: "true" })
+			.onConflictDoUpdate({
+				target: [settings.userId, settings.key],
+				set: { value: "true" },
+			});
+		return { itemsCreated: 0, categoriesCreated: [] };
+	}
+
+	// Fetch all selected global items
+	const selectedItems = await db
+		.select()
+		.from(globalItems)
+		.where(inArray(globalItems.id, globalItemIds));
+
+	if (selectedItems.length === 0) {
+		await db
+			.insert(settings)
+			.values({ userId, key: "onboardingComplete", value: "true" })
+			.onConflictDoUpdate({
+				target: [settings.userId, settings.key],
+				set: { value: "true" },
+			});
+		return { itemsCreated: 0, categoriesCreated: [] };
+	}
+
+	// Collect unique category names from global items
+	const categoryNames = [
+		...new Set(
+			selectedItems
+				.map((gi) => gi.category)
+				.filter((c): c is string => c !== null && c.trim() !== ""),
+		),
+	];
+
+	// Get existing user categories
+	const existingCats = await db
+		.select()
+		.from(categories)
+		.where(eq(categories.userId, userId));
+
+	const existingCatMap = new Map(
+		existingCats.map((c) => [c.name.toLowerCase(), c.id]),
+	);
+
+	// Create missing categories
+	const newCategoryNames: string[] = [];
+	for (const catName of categoryNames) {
+		if (!existingCatMap.has(catName.toLowerCase())) {
+			const [created] = await db
+				.insert(categories)
+				.values({ name: catName, userId })
+				.returning();
+			existingCatMap.set(catName.toLowerCase(), created.id);
+			newCategoryNames.push(catName);
+		}
+	}
+
+	// Get the "Uncategorized" category for items without a category
+	let uncategorizedId = existingCatMap.get("uncategorized");
+	if (!uncategorizedId) {
+		const [unc] = await db
+			.insert(categories)
+			.values({ name: "Uncategorized", userId })
+			.returning();
+		uncategorizedId = unc.id;
+	}
+
+	// Create user items linked to global items
+	let itemsCreated = 0;
+	for (const gi of selectedItems) {
+		const catId = gi.category
+			? (existingCatMap.get(gi.category.toLowerCase()) ?? uncategorizedId)
+			: uncategorizedId;
+
+		await db.insert(items).values({
+			name: gi.brand ? `${gi.brand} ${gi.model}` : gi.model,
+			categoryId: catId,
+			userId,
+			weightGrams: gi.weightGrams,
+			priceCents: gi.priceCents,
+			imageFilename: gi.imageFilename,
+			globalItemId: gi.id,
+		});
+		itemsCreated++;
+	}
+
+	// Mark onboarding complete
+	await db
+		.insert(settings)
+		.values({ userId, key: "onboardingComplete", value: "true" })
+		.onConflictDoUpdate({
+			target: [settings.userId, settings.key],
+			set: { value: "true" },
+		});
+
+	return { itemsCreated, categoriesCreated: newCategoryNames };
+}