diff --git a/app/playwright.config.ts b/app/playwright.config.ts
new file mode 100644
index 0000000..676a7b3
--- /dev/null
+++ b/app/playwright.config.ts
@@ -0,0 +1,13 @@
+import { defineConfig } from '@playwright/test';
+
+export default defineConfig({
+	testDir: 'tests/e2e',
+	use: { baseURL: 'http://localhost:5173' },
+	webServer: {
+		command: 'npm run dev',
+		port: 5173,
+		reuseExistingServer: true,
+		timeout: 120_000
+	},
+	timeout: 60_000
+});
diff --git a/app/src/lib/components/PostView.svelte b/app/src/lib/components/PostView.svelte
index 0b06b2a..f838d01 100644
--- a/app/src/lib/components/PostView.svelte
+++ b/app/src/lib/components/PostView.svelte
@@ -1,6 +1,10 @@
 <script lang="ts">
 	import type { NostrEvent } from '$lib/nostr/loaders';
+	import type { SignedEvent } from '$lib/nostr/signer';
 	import { renderMarkdown } from '$lib/render/markdown';
+	import Reactions from './Reactions.svelte';
+	import ReplyList from './ReplyList.svelte';
+	import ReplyComposer from './ReplyComposer.svelte';
 
 	interface Props {
 		event: NostrEvent;
@@ -14,6 +18,7 @@
 		return e.tags.filter((t) => t[0] === name).map((t) => t[1]);
 	}
 
+	const dtag = $derived(tagValue(event, 'd'));
 	const title = $derived(tagValue(event, 'title') || '(ohne Titel)');
 	const summary = $derived(tagValue(event, 'summary'));
 	const image = $derived(tagValue(event, 'image'));
@@ -30,6 +35,13 @@
 	const tags = $derived(tagsAll(event, 't'));
 	const bodyHtml = $derived(renderMarkdown(event.content));
 
+	// Optimistisch gesendete Replies: der Composer pusht sie rein,
+	// ReplyList merged sie mit den vom Relay geladenen Replies (dedup per id).
+	let optimisticReplies: NostrEvent[] = $state([]);
+	function handlePublished(signed: SignedEvent) {
+		optimisticReplies = [...optimisticReplies, signed as unknown as NostrEvent];
+	}
+
 	$effect(() => {
 		document.title = `${title} – Jörg Lohrer`;
 	});
@@ -57,6 +69,12 @@
 
 <article>{@html bodyHtml}</article>
 
+{#if dtag}
+	<Reactions {dtag} />
+	<ReplyComposer {dtag} eventId={event.id} onPublished={handlePublished} />
+	<ReplyList {dtag} optimistic={optimisticReplies} />
+{/if}
+
 <style>
 	.post-title {
 		font-size: 1.5rem;
diff --git a/app/src/lib/components/Reactions.svelte b/app/src/lib/components/Reactions.svelte
new file mode 100644
index 0000000..2a1b585
--- /dev/null
+++ b/app/src/lib/components/Reactions.svelte
@@ -0,0 +1,58 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import type { ReactionSummary } from '$lib/nostr/loaders';
+	import { loadReactions } from '$lib/nostr/loaders';
+
+	interface Props {
+		dtag: string;
+	}
+	let { dtag }: Props = $props();
+
+	let reactions: ReactionSummary[] = $state([]);
+
+	onMount(async () => {
+		try {
+			reactions = await loadReactions(dtag);
+		} catch {
+			reactions = [];
+		}
+	});
+
+	function displayChar(c: string): string {
+		if (c === '+' || c === '') return '👍';
+		if (c === '-') return '👎';
+		return c;
+	}
+</script>
+
+{#if reactions.length > 0}
+	<div class="reactions">
+		{#each reactions as r}
+			<span class="reaction">
+				<span class="emoji">{displayChar(r.content)}</span>
+				<span class="count">{r.count}</span>
+			</span>
+		{/each}
+	</div>
+{/if}
+
+<style>
+	.reactions {
+		display: flex;
+		flex-wrap: wrap;
+		gap: 0.5rem;
+		margin: 1.5rem 0;
+	}
+	.reaction {
+		display: inline-flex;
+		align-items: center;
+		gap: 0.3rem;
+		padding: 0.2rem 0.6rem;
+		background: var(--code-bg);
+		border-radius: 999px;
+		font-size: 0.9rem;
+	}
+	.count {
+		color: var(--muted);
+	}
+</style>
diff --git a/app/src/lib/components/ReplyComposer.svelte b/app/src/lib/components/ReplyComposer.svelte
new file mode 100644
index 0000000..49918b2
--- /dev/null
+++ b/app/src/lib/components/ReplyComposer.svelte
@@ -0,0 +1,148 @@
+<script lang="ts">
+	import { get } from 'svelte/store';
+	import {
+		hasNip07,
+		getPublicKey,
+		signEvent,
+		type SignedEvent,
+		type UnsignedEvent
+	} from '$lib/nostr/signer';
+	import { AUTHOR_PUBKEY_HEX } from '$lib/nostr/config';
+	import { pool } from '$lib/nostr/pool';
+	import { readRelays } from '$lib/stores/readRelays';
+
+	interface Props {
+		/** d-Tag des Posts, auf den geantwortet wird */
+		dtag: string;
+		/** Event-ID des ursprünglichen Posts (für e-Tag) */
+		eventId: string;
+		/** Callback, wenn ein Reply erfolgreich publiziert wurde */
+		onPublished?: (ev: SignedEvent) => void;
+	}
+	let { dtag, eventId, onPublished }: Props = $props();
+
+	let text = $state('');
+	let publishing = $state(false);
+	let error: string | null = $state(null);
+	let info: string | null = $state(null);
+
+	const nip07 = hasNip07();
+
+	async function submit() {
+		error = null;
+		info = null;
+		if (!text.trim()) {
+			error = 'Leeres Kommentar — nichts zu senden.';
+			return;
+		}
+		publishing = true;
+		try {
+			const pubkey = await getPublicKey();
+			if (!pubkey) {
+				error = 'Nostr-Extension (z. B. Alby) hat den Pubkey nicht geliefert.';
+				return;
+			}
+			const unsigned: UnsignedEvent = {
+				kind: 1,
+				pubkey,
+				created_at: Math.floor(Date.now() / 1000),
+				tags: [
+					['a', `30023:${AUTHOR_PUBKEY_HEX}:${dtag}`],
+					['e', eventId, '', 'root'],
+					['p', AUTHOR_PUBKEY_HEX]
+				],
+				content: text.trim()
+			};
+			const signed = await signEvent(unsigned);
+			if (!signed) {
+				error = 'Signatur wurde abgelehnt oder ist fehlgeschlagen.';
+				return;
+			}
+			const relays = get(readRelays);
+			const results = await pool.publish(relays, signed);
+			const okCount = results.filter((r) => r.ok).length;
+			if (okCount === 0) {
+				error = 'Kein Relay hat den Kommentar akzeptiert.';
+				return;
+			}
+			info = `Kommentar gesendet (${okCount}/${results.length} Relays).`;
+			text = '';
+			onPublished?.(signed);
+		} catch (e) {
+			error = e instanceof Error ? e.message : 'Unbekannter Fehler';
+		} finally {
+			publishing = false;
+		}
+	}
+</script>
+
+<div class="composer">
+	{#if !nip07}
+		<p class="hint">
+			Um zu kommentieren, benötigst du eine Nostr-Extension
+			(<a href="https://getalby.com" target="_blank" rel="noopener">Alby</a>,
+			<a href="https://github.com/fiatjaf/nos2x" target="_blank" rel="noopener">nos2x</a>), oder
+			kommentiere direkt in einem Nostr-Client.
+		</p>
+	{:else}
+		<textarea
+			bind:value={text}
+			placeholder="Dein Kommentar …"
+			rows="4"
+			disabled={publishing}
+		></textarea>
+		<div class="actions">
+			<button type="button" onclick={submit} disabled={publishing || !text.trim()}>
+				{publishing ? 'Sende …' : 'Kommentar senden'}
+			</button>
+		</div>
+		{#if error}<p class="error">{error}</p>{/if}
+		{#if info}<p class="info">{info}</p>{/if}
+	{/if}
+</div>
+
+<style>
+	.composer {
+		margin: 1.5rem 0;
+	}
+	textarea {
+		width: 100%;
+		padding: 0.6rem;
+		font: inherit;
+		color: inherit;
+		background: var(--code-bg);
+		border: 1px solid var(--border);
+		border-radius: 4px;
+		resize: vertical;
+	}
+	.actions {
+		margin-top: 0.5rem;
+		display: flex;
+		justify-content: flex-end;
+	}
+	button {
+		padding: 0.4rem 1rem;
+		background: var(--accent);
+		color: white;
+		border: none;
+		border-radius: 4px;
+		cursor: pointer;
+		font: inherit;
+	}
+	button:disabled {
+		opacity: 0.5;
+		cursor: not-allowed;
+	}
+	.hint {
+		font-size: 0.9rem;
+		color: var(--muted);
+	}
+	.error {
+		color: #991b1b;
+		font-size: 0.9rem;
+	}
+	.info {
+		color: #065f46;
+		font-size: 0.9rem;
+	}
+</style>
diff --git a/app/src/lib/components/ReplyItem.svelte b/app/src/lib/components/ReplyItem.svelte
new file mode 100644
index 0000000..63d746f
--- /dev/null
+++ b/app/src/lib/components/ReplyItem.svelte
@@ -0,0 +1,44 @@
+<script lang="ts">
+	import type { NostrEvent } from '$lib/nostr/loaders';
+
+	interface Props {
+		event: NostrEvent;
+	}
+	let { event }: Props = $props();
+
+	const date = $derived(new Date(event.created_at * 1000).toLocaleString('de-DE'));
+	const authorNpub = $derived(event.pubkey.slice(0, 12) + '…');
+</script>
+
+<li class="reply">
+	<div class="meta">
+		<span class="author">{authorNpub}</span>
+		<span class="sep">·</span>
+		<span class="date">{date}</span>
+	</div>
+	<div class="content">{event.content}</div>
+</li>
+
+<style>
+	.reply {
+		list-style: none;
+		padding: 0.8rem 0;
+		border-bottom: 1px solid var(--border);
+	}
+	.meta {
+		font-size: 0.85rem;
+		color: var(--muted);
+		margin-bottom: 0.3rem;
+	}
+	.author {
+		font-family: monospace;
+	}
+	.sep {
+		margin: 0 0.4rem;
+		opacity: 0.5;
+	}
+	.content {
+		white-space: pre-wrap;
+		word-wrap: break-word;
+	}
+</style>
diff --git a/app/src/lib/components/ReplyList.svelte b/app/src/lib/components/ReplyList.svelte
new file mode 100644
index 0000000..3bff962
--- /dev/null
+++ b/app/src/lib/components/ReplyList.svelte
@@ -0,0 +1,68 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import type { NostrEvent } from '$lib/nostr/loaders';
+	import { loadReplies } from '$lib/nostr/loaders';
+	import ReplyItem from './ReplyItem.svelte';
+
+	interface Props {
+		dtag: string;
+		/**
+		 * Optimistisch hinzugefügte Events (z. B. frisch gesendete Kommentare).
+		 * Werden vor dem Rendern zur geladenen Liste gemerged, dedupliziert per id.
+		 */
+		optimistic?: NostrEvent[];
+	}
+	let { dtag, optimistic = [] }: Props = $props();
+
+	let fetched: NostrEvent[] = $state([]);
+	let loading = $state(true);
+
+	const merged = $derived.by(() => {
+		const byId = new Map<string, NostrEvent>();
+		for (const ev of fetched) byId.set(ev.id, ev);
+		for (const ev of optimistic) byId.set(ev.id, ev);
+		return [...byId.values()].sort((a, b) => a.created_at - b.created_at);
+	});
+
+	onMount(async () => {
+		try {
+			fetched = await loadReplies(dtag);
+		} finally {
+			loading = false;
+		}
+	});
+</script>
+
+<section class="replies">
+	<h3>Kommentare ({merged.length})</h3>
+	{#if loading}
+		<p class="hint">Lade Kommentare …</p>
+	{:else if merged.length === 0}
+		<p class="hint">Noch keine Kommentare.</p>
+	{:else}
+		<ul>
+			{#each merged as reply (reply.id)}
+				<ReplyItem event={reply} />
+			{/each}
+		</ul>
+	{/if}
+</section>
+
+<style>
+	.replies {
+		margin: 2rem 0;
+	}
+	h3 {
+		font-size: 1.1rem;
+		margin: 0 0 0.8rem;
+	}
+	ul {
+		list-style: none;
+		padding: 0;
+		margin: 0;
+	}
+	.hint {
+		color: var(--muted);
+		font-size: 0.9rem;
+	}
+</style>
diff --git a/app/test-results/.last-run.json b/app/test-results/.last-run.json
new file mode 100644
index 0000000..cbcc1fb
--- /dev/null
+++ b/app/test-results/.last-run.json
@@ -0,0 +1,4 @@
+{
+  "status": "passed",
+  "failedTests": []
+}
\ No newline at end of file
diff --git a/app/tests/e2e/home.test.ts b/app/tests/e2e/home.test.ts
new file mode 100644
index 0000000..443ed31
--- /dev/null
+++ b/app/tests/e2e/home.test.ts
@@ -0,0 +1,8 @@
+import { expect, test } from '@playwright/test';
+
+test('Home zeigt Profil und mindestens einen Post', async ({ page }) => {
+	await page.goto('/');
+	await expect(page.getByRole('heading', { level: 1, name: /Beiträge/ })).toBeVisible();
+	await expect(page.locator('.profile .name')).toBeVisible({ timeout: 15_000 });
+	await expect(page.locator('a.card').first()).toBeVisible({ timeout: 15_000 });
+});
diff --git a/app/tests/e2e/post.test.ts b/app/tests/e2e/post.test.ts
new file mode 100644
index 0000000..1f32c9b
--- /dev/null
+++ b/app/tests/e2e/post.test.ts
@@ -0,0 +1,16 @@
+import { expect, test } from '@playwright/test';
+
+test('Einzelpost rendert Titel und Markdown-Body', async ({ page }) => {
+	await page.goto('/dezentrale-oep-oer/');
+	// Titel steht einmal als .post-title (H1 außerhalb des Artikels),
+	// und nochmal im Markdown-Body des Events — wir prüfen den ersten.
+	await expect(page.locator('h1.post-title')).toBeVisible({ timeout: 15_000 });
+	await expect(page.locator('h1.post-title')).toContainText('Gemeinsam die Bildungszukunft');
+	await expect(page.locator('article')).toContainText('Open Educational');
+});
+
+test('Legacy-URL wird auf kurze Form umgeleitet', async ({ page }) => {
+	await page.goto('/2025/03/04/dezentrale-oep-oer.html/');
+	await expect(page).toHaveURL(/\/dezentrale-oep-oer\/$/);
+	await expect(page.locator('h1.post-title')).toBeVisible({ timeout: 15_000 });
+});