diff --git a/apps/web/src/lib/components/CreateCollectiveModal.svelte b/apps/web/src/lib/components/CreateCollectiveModal.svelte
index 26ebf68..6c4d9ae 100644
--- a/apps/web/src/lib/components/CreateCollectiveModal.svelte
+++ b/apps/web/src/lib/components/CreateCollectiveModal.svelte
@@ -2,6 +2,7 @@
 	import { goto } from '$app/navigation';
 	import { getSupabase } from '$lib/supabase';
 	import { currentCollective, userCollectives } from '$lib/stores/collective';
+	import Spinner from './Spinner.svelte';
 	import * as m from '$lib/paraglide/messages';
 
 	let { onClose }: { onClose: () => void } = $props();
@@ -102,11 +103,16 @@
 					type="submit"
 					data-testid="create-collective-modal-submit"
 					disabled={!name.trim() || creating}
-					class="rounded-lg bg-slate-900 px-4 py-1.5 text-sm font-semibold text-white
+					class="inline-flex items-center gap-2 rounded-lg bg-slate-900 px-4 py-1.5 text-sm font-semibold text-white
 						transition-opacity hover:opacity-90 disabled:opacity-50
 						dark:bg-slate-50 dark:text-slate-900"
 				>
-					{creating ? m.loading() : m.create_collective_modal_button()}
+					{#if creating}
+						<Spinner size="sm" />
+						<span>{m.loading()}</span>
+					{:else}
+						{m.create_collective_modal_button()}
+					{/if}
 				</button>
 			</div>
 		</form>
diff --git a/apps/web/src/routes/(app)/+layout.svelte b/apps/web/src/routes/(app)/+layout.svelte
index 1cfce8a..bfa220f 100644
--- a/apps/web/src/routes/(app)/+layout.svelte
+++ b/apps/web/src/routes/(app)/+layout.svelte
@@ -17,6 +17,7 @@
 	import BottomTabBar from '$lib/components/layout/BottomTabBar.svelte';
 	import MobileDrawer from '$lib/components/layout/MobileDrawer.svelte';
 	import UndoToast from '$lib/components/UndoToast.svelte';
+	import Spinner from '$lib/components/Spinner.svelte';
 	import * as m from '$lib/paraglide/messages';
 
 	let { children }: { children: Snippet } = $props();
@@ -149,8 +150,9 @@
 </script>
 
 {#if $authLoading}
-	<div class="flex h-screen items-center justify-center bg-background">
-		<span class="text-sm text-text-secondary">{m.loading()}</span>
+	<div class="flex h-screen flex-col items-center justify-center gap-3 bg-background text-text-secondary">
+		<Spinner size="lg" />
+		<span class="text-sm">{m.loading()}</span>
 	</div>
 {:else if $isAuthenticated}
 	<!-- Mobile: column stack (top bar → main → bottom tab bar).
diff --git a/apps/web/src/routes/(app)/collective/manage/+page.svelte b/apps/web/src/routes/(app)/collective/manage/+page.svelte
index 2bdf29d..31eeb69 100644
--- a/apps/web/src/routes/(app)/collective/manage/+page.svelte
+++ b/apps/web/src/routes/(app)/collective/manage/+page.svelte
@@ -5,6 +5,7 @@
 	import { currentUser } from '$lib/stores/auth';
 	import { currentCollective, collectiveMembers, userCollectives } from '$lib/stores/collective';
 	import Avatar from '$lib/components/Avatar.svelte';
+	import Spinner from '$lib/components/Spinner.svelte';
 	import type { FeatureFlags, SectionKey, ItemFrequency } from '@colectivo/types';
 	import { SECTION_KEYS } from '@colectivo/types';
 	import { setCollectiveFeature } from '$lib/stores/features';
@@ -551,7 +552,10 @@
 		</h2>
 
 		{#if loading}
-			<p class="text-sm text-text-secondary">{m.loading()}</p>
+			<p class="flex items-center gap-2 text-sm text-text-secondary">
+				<Spinner size="sm" />
+				<span>{m.loading()}</span>
+			</p>
 		{:else}
 			<ul>
 				{#each members as member}
@@ -766,10 +770,15 @@
 				data-testid="generate-invite"
 				onclick={generateInviteLink}
 				disabled={generating}
-				class="mb-3 w-full rounded-lg bg-slate-900 px-4 py-2 text-sm font-semibold text-white
+				class="mb-3 inline-flex w-full items-center justify-center gap-2 rounded-lg bg-slate-900 px-4 py-2 text-sm font-semibold text-white
 					hover:opacity-90 disabled:opacity-50 dark:bg-slate-50 dark:text-slate-900"
 			>
-				{generating ? m.loading() : m.manage_generate_link()}
+				{#if generating}
+					<Spinner size="sm" />
+					<span>{m.loading()}</span>
+				{:else}
+					{m.manage_generate_link()}
+				{/if}
 			</button>
 
 			{#if generatedLink}
@@ -1018,10 +1027,15 @@
 					data-testid="common-item-add-save"
 					disabled={!addName.trim() || addSaving}
 					onclick={() => void confirmAdd()}
-					class="rounded-md bg-slate-900 px-4 py-1.5 text-sm font-semibold text-white hover:opacity-90 disabled:opacity-50
+					class="inline-flex items-center gap-2 rounded-md bg-slate-900 px-4 py-1.5 text-sm font-semibold text-white hover:opacity-90 disabled:opacity-50
 						dark:bg-slate-50 dark:text-slate-900"
 				>
-					{addSaving ? m.loading() : m.common_items_add_save()}
+					{#if addSaving}
+						<Spinner size="sm" />
+						<span>{m.loading()}</span>
+					{:else}
+						{m.common_items_add_save()}
+					{/if}
 				</button>
 			</div>
 		</div>
diff --git a/apps/web/src/routes/(app)/notes/archive/+page.svelte b/apps/web/src/routes/(app)/notes/archive/+page.svelte
index 41df38f..8b60a18 100644
--- a/apps/web/src/routes/(app)/notes/archive/+page.svelte
+++ b/apps/web/src/routes/(app)/notes/archive/+page.svelte
@@ -4,6 +4,7 @@
 	import { loadArchivedNotes, unarchiveNote, trashNote } from '$lib/stores/notes';
 	import type { Note } from '@colectivo/types';
 	import { ArrowLeft, ArchiveRestore, Trash2 } from 'lucide-svelte';
+	import Spinner from '$lib/components/Spinner.svelte';
 	import * as m from '$lib/paraglide/messages';
 
 	let archived = $state<Note[]>([]);
@@ -44,7 +45,10 @@
 
 	<div class="flex-1 overflow-y-auto px-6 py-6">
 		{#if loading}
-			<p class="text-sm text-text-secondary">{m.loading()}</p>
+			<p class="flex items-center gap-2 text-sm text-text-secondary">
+				<Spinner size="sm" />
+				<span>{m.loading()}</span>
+			</p>
 		{:else if archived.length === 0}
 			<p class="text-sm text-text-secondary">{m.notes_archived_empty()}</p>
 		{:else}
diff --git a/apps/web/src/routes/(app)/search/+page.svelte b/apps/web/src/routes/(app)/search/+page.svelte
index 0e7fac7..fbd5f14 100644
--- a/apps/web/src/routes/(app)/search/+page.svelte
+++ b/apps/web/src/routes/(app)/search/+page.svelte
@@ -4,6 +4,7 @@
 	import { Search, FileText, CheckSquare, ShoppingCart } from 'lucide-svelte';
 	import * as m from '$lib/paraglide/messages';
 	import ScreenMasthead from '$lib/components/ScreenMasthead.svelte';
+	import Spinner from '$lib/components/Spinner.svelte';
 
 	let query = $state('');
 	let results = $state<SearchRow[]>([]);
@@ -119,7 +120,10 @@
 		{#if query.trim().length < 2}
 			<p class="text-sm text-text-secondary">{m.search_hint()}</p>
 		{:else if loading}
-			<p class="text-sm text-text-secondary">{m.loading()}</p>
+			<p class="flex items-center gap-2 text-sm text-text-secondary">
+				<Spinner size="sm" />
+				<span>{m.loading()}</span>
+			</p>
 		{:else if results.length === 0}
 			<p class="text-sm text-text-secondary">{m.search_empty()}</p>
 		{:else}
diff --git a/apps/web/tests/e2e/spinner.test.ts b/apps/web/tests/e2e/spinner.test.ts
new file mode 100644
index 0000000..7acc59b
--- /dev/null
+++ b/apps/web/tests/e2e/spinner.test.ts
@@ -0,0 +1,149 @@
+/**
+ * SP-series — Fase 16 (loading spinner visual feedback).
+ *
+ * The Spinner component itself is unit-tested in
+ * `src/lib/components/Spinner.test.ts` (SP-U-01..05). These E2E specs assert
+ * that the spinner actually shows up at the five integration sites listed in
+ * `plan/fase-16-spinner.md` when the backing async operation is in flight.
+ *
+ * Strategy: every spec uses `page.route(...)` to add ~500ms of artificial
+ * latency to the request that drives the spinner so the assertion window is
+ * deterministic — without the throttle the loopback round-trip resolves in
+ * <30ms and the spinner can flicker past Playwright's auto-wait cadence.
+ */
+import { test, expect } from '@playwright/test';
+import { USERS } from '../fixtures/users.js';
+import { loginAs } from '../fixtures/login.js';
+
+const THROTTLE_MS = 500;
+
+test.describe('Loading spinner', () => {
+	test('SP-E-01: /search shows the spinner while the search RPC is in flight', async ({
+		page
+	}) => {
+		await loginAs(page, USERS.borja);
+
+		// Throttle the search RPC so the loading window stays open long enough
+		// for the spinner assertion below.
+		await page.route('**/rest/v1/rpc/search_in_collective**', async (route) => {
+			await new Promise((r) => setTimeout(r, THROTTLE_MS));
+			await route.continue();
+		});
+
+		await page.goto('/search');
+		const input = page.getByPlaceholder(/search|buscar/i);
+		await expect(input).toBeVisible({ timeout: 15_000 });
+		await input.fill('Milk');
+
+		// Debounce is 300ms + 500ms throttle ≈ ~800ms window where the
+		// spinner is mounted in the `{#if loading}` branch of /search.
+		const spinner = page.getByTestId('spinner').first();
+		await expect(spinner).toBeVisible({ timeout: 5_000 });
+
+		// And it disappears once the RPC resolves.
+		await expect(spinner).toHaveCount(0, { timeout: 10_000 });
+	});
+
+	test('SP-E-02: Save button in "Add common item" modal shows the spinner while saving', async ({
+		page
+	}) => {
+		await loginAs(page, USERS.ana);
+
+		// Throttle the set_item_frequency_weight RPC so addSaving stays true
+		// long enough for the spinner to be visible.
+		await page.route(
+			'**/rest/v1/rpc/set_item_frequency_weight**',
+			async (route) => {
+				await new Promise((r) => setTimeout(r, THROTTLE_MS));
+				await route.continue();
+			}
+		);
+
+		await page.goto('/collective/manage');
+		await page.waitForLoadState('networkidle');
+
+		await page.getByTestId('common-item-add-button').click();
+		const nameInput = page.getByTestId('common-item-add-name');
+		await expect(nameInput).toBeVisible({ timeout: 5_000 });
+		await nameInput.fill(`sp-e-02-${Date.now()}`);
+
+		const saveButton = page.getByTestId('common-item-add-save');
+		await saveButton.click();
+
+		// Spinner is scoped inside the Save button so we look for any spinner
+		// that's also a descendant of the button — this avoids matching some
+		// unrelated spinner elsewhere on the page.
+		await expect(saveButton.getByTestId('spinner')).toBeVisible({ timeout: 5_000 });
+	});
+
+	test('SP-E-03: auth splash shows the spinner while Supabase resolves the session', async ({
+		browser
+	}) => {
+		// The splash in `(app)/+layout.svelte` is gated on `$authLoading`,
+		// which only flips false once Supabase's `onAuthStateChange` fires
+		// `INITIAL_SESSION`. With no stored session the emit is synchronous
+		// and the splash flashes past Playwright's auto-wait.
+		//
+		// Trick: seed localStorage with an *expired* sb-* auth token so
+		// GoTrue's `_recoverAndRefresh` is forced to hit
+		// `/auth/v1/token?grant_type=refresh_token`. Throttle that endpoint
+		// by 500ms and the splash stays mounted for the assertion window.
+		const context = await browser.newContext();
+		const page = await context.newPage();
+
+		await context.addInitScript(() => {
+			// Synthetic expired Supabase session. We can't sign it correctly,
+			// but GoTrue trusts the stored payload and skips straight to
+			// refresh as soon as it sees expires_at in the past.
+			const payload = {
+				access_token: 'sp-e-03-fake-access',
+				token_type: 'bearer',
+				expires_in: 3600,
+				expires_at: Math.floor(Date.now() / 1000) - 60,
+				refresh_token: 'sp-e-03-fake-refresh',
+				user: {
+					id: '00000000-0000-0000-0000-000000000000',
+					aud: 'authenticated',
+					role: 'authenticated',
+					email: 'spinner-splash@dev.local',
+					app_metadata: { provider: 'keycloak' },
+					user_metadata: {},
+					created_at: new Date().toISOString()
+				}
+			};
+			// Supabase derives the storage key from the URL hostname (first
+			// label only): `sb-${hostname.split('.')[0]}-auth-token`. Our dev
+			// PUBLIC_SUPABASE_URL is http://192.168.1.167:8001 → key
+			// `sb-192-auth-token`. We populate every plausible key so the
+			// test is resilient to a localhost override.
+			const KEYS = ['sb-192-auth-token', 'sb-localhost-auth-token'];
+			for (const k of KEYS) localStorage.setItem(k, JSON.stringify(payload));
+		});
+
+		// Stall the GoTrue token-refresh endpoint indefinitely. With the
+		// seeded expired session above, `_recoverAndRefresh` is forced to
+		// call POST /auth/v1/token?grant_type=refresh_token before emitting
+		// INITIAL_SESSION. While the call is in flight `authLoading` stays
+		// true and the splash is mounted, which is exactly the window the
+		// assertion needs. We never `route.continue()` — the test asserts
+		// the spinner is visible and then tears the context down.
+		let releaseToken: (() => void) | null = null;
+		const tokenStall = new Promise<void>((resolve) => {
+			releaseToken = resolve;
+		});
+		await page.route('**/auth/v1/token**', async (route) => {
+			await tokenStall;
+			await route.fulfill({ status: 503, body: '{}' });
+		});
+
+		try {
+			await page.goto('/lists', { waitUntil: 'commit' });
+			const spinner = page.getByTestId('spinner').first();
+			await expect(spinner).toBeVisible({ timeout: 10_000 });
+		} finally {
+			// Release the stalled refresh so the context can shut down cleanly.
+			if (releaseToken) releaseToken();
+			await context.close();
+		}
+	});
+});