diff --git a/apps/web/src/lib/components/marketplace/PublishDeckModal.svelte b/apps/web/src/lib/components/marketplace/PublishDeckModal.svelte
new file mode 100644
index 0000000..801c7e8
--- /dev/null
+++ b/apps/web/src/lib/components/marketplace/PublishDeckModal.svelte
@@ -0,0 +1,586 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import type { Card, Deck } from '@cards/domain';
+	import {
+		getMyAuthorProfile,
+		getMarketplaceDeck,
+		initMarketplaceDeck,
+		publishMarketplaceVersion,
+		type MarketplaceAuthor,
+	} from '$lib/api/marketplace.ts';
+	import { toasts } from '$lib/stores/toasts.svelte.ts';
+
+	interface Props {
+		deck: Deck;
+		cards: Card[];
+		onClose: () => void;
+		onPublished: (slug: string) => void;
+	}
+
+	let { deck, cards, onClose, onPublished }: Props = $props();
+
+	// Author + slug-check state
+	let author = $state<MarketplaceAuthor | null>(null);
+	let loadingAuthor = $state(true);
+	let slugExists = $state<boolean | null>(null); // null = unchecked
+	let existingVersion = $state<string | null>(null);
+	let checkingSlug = $state(false);
+
+	// Modal wird pro Klick frisch gemountet — Init-Capture aus Props ist gewollt.
+	// svelte-ignore state_referenced_locally
+	let slug = $state(slugify(deck.name));
+	// svelte-ignore state_referenced_locally
+	let title = $state(deck.name);
+	// svelte-ignore state_referenced_locally
+	let description = $state(deck.description ?? '');
+	let license = $state('CC BY 4.0');
+	let semver = $state('1.0.0');
+	let changelog = $state('');
+
+	let busy = $state(false);
+	let error = $state<string | null>(null);
+
+	const marketplaceCards = $derived(
+		cards.map((c) => ({ type: c.type, fields: c.fields as Record<string, string> }))
+	);
+
+	const suggestedSemver = $derived.by(() => {
+		if (!existingVersion) return '1.0.0';
+		const m = existingVersion.match(/^(\d+)\.(\d+)\.(\d+)$/);
+		if (!m) return '1.0.0';
+		return `${m[1]}.${Number(m[2]) + 1}.0`;
+	});
+
+	// Update semver suggestion when slug check completes
+	$effect(() => {
+		semver = suggestedSemver;
+	});
+
+	onMount(async () => {
+		try {
+			author = await getMyAuthorProfile();
+		} catch {
+			// no profile yet
+		}
+		loadingAuthor = false;
+		if (author) await checkSlug();
+	});
+
+	function slugify(name: string): string {
+		return name
+			.toLowerCase()
+			.replace(/ä/g, 'ae').replace(/ö/g, 'oe').replace(/ü/g, 'ue').replace(/ß/g, 'ss')
+			.replace(/[^a-z0-9]+/g, '-')
+			.replace(/^-+|-+$/g, '')
+			.slice(0, 60);
+	}
+
+	let slugCheckTimer: ReturnType<typeof setTimeout>;
+	function onSlugInput() {
+		slugExists = null;
+		existingVersion = null;
+		clearTimeout(slugCheckTimer);
+		slugCheckTimer = setTimeout(checkSlug, 500);
+	}
+
+	async function checkSlug() {
+		const s = slug.trim();
+		if (!s) return;
+		checkingSlug = true;
+		try {
+			const data = await getMarketplaceDeck(s);
+			slugExists = true;
+			existingVersion = data.latest_version?.semver ?? null;
+		} catch {
+			slugExists = false;
+			existingVersion = null;
+		}
+		checkingSlug = false;
+	}
+
+	async function onSubmit(e: SubmitEvent) {
+		e.preventDefault();
+		if (busy || !author) return;
+		busy = true;
+		error = null;
+
+		try {
+			if (!slugExists) {
+				await initMarketplaceDeck({
+					slug: slug.trim(),
+					title: title.trim(),
+					description: description.trim() || undefined,
+					license,
+				});
+			}
+
+			const result = await publishMarketplaceVersion(slug.trim(), {
+				semver: semver.trim(),
+				changelog: changelog.trim() || undefined,
+				cards: marketplaceCards,
+			});
+
+			toasts.success(
+				`${result.version.card_count} Karten als v${result.version.semver} veröffentlicht`
+			);
+			onPublished(slug.trim());
+		} catch (e) {
+			error = (e as Error).message;
+			busy = false;
+		}
+	}
+
+	const canSubmit = $derived(
+		!busy &&
+		!!author &&
+		slug.trim().length > 0 &&
+		title.trim().length > 0 &&
+		/^\d+\.\d+\.\d+$/.test(semver.trim()) &&
+		marketplaceCards.length > 0 &&
+		slugExists !== null
+	);
+
+	const LICENSES = [
+		'CC BY 4.0',
+		'CC BY-SA 4.0',
+		'CC BY-NC 4.0',
+		'CC0 1.0',
+		'Alle Rechte vorbehalten',
+	];
+</script>
+
+<div
+	class="overlay"
+	role="dialog"
+	aria-modal="true"
+	aria-label="Deck veröffentlichen"
+>
+	<div class="modal">
+		<!-- Header -->
+		<div class="modal-head">
+			<div>
+				<h2 class="modal-title">Zum Marketplace veröffentlichen</h2>
+				<p class="modal-subtitle">
+					{cards.length} Karte{cards.length !== 1 ? 'n' : ''} aus „{deck.name}"
+				</p>
+			</div>
+			<button type="button" class="close-btn" onclick={onClose} aria-label="Schließen">×</button>
+		</div>
+
+		{#if loadingAuthor}
+			<p class="loading-hint">Lade Author-Profil…</p>
+
+		{:else if !author}
+			<!-- No author profile -->
+			<div class="no-author">
+				<div class="no-author-icon">✍️</div>
+				<p class="no-author-text">Du brauchst zuerst ein Author-Profil um Decks zu veröffentlichen.</p>
+				<a href="/me/published" class="btn-primary" onclick={onClose}>
+					Author-Profil anlegen →
+				</a>
+			</div>
+
+		{:else}
+			<!-- Author confirmed -->
+			<div class="author-badge">
+				<span class="author-dot"></span>
+				<span>Author: <strong>{author.display_name}</strong> (@{author.slug})</span>
+			</div>
+
+			<form class="pub-form" onsubmit={onSubmit}>
+				<!-- Slug -->
+				<div class="field">
+					<label class="field-label" for="pub-slug">Marketplace-Slug</label>
+					<div class="slug-row">
+						<span class="slug-prefix">cardecky.mana.how/d/</span>
+						<input
+							id="pub-slug"
+							type="text"
+							bind:value={slug}
+							oninput={onSlugInput}
+							required
+							pattern="[a-z0-9](?:[a-z0-9-]*[a-z0-9])?"
+							maxlength="60"
+							class="input mono slug-input"
+						/>
+						{#if checkingSlug}
+							<span class="slug-status checking">…</span>
+						{:else if slugExists === true}
+							<span class="slug-status exists">↻ Update</span>
+						{:else if slugExists === false}
+							<span class="slug-status new">+ Neu</span>
+						{/if}
+					</div>
+					{#if slugExists === true && existingVersion}
+						<span class="field-hint">Deck existiert bereits (v{existingVersion}) — neue Version wird veröffentlicht.</span>
+					{:else if slugExists === false}
+						<span class="field-hint">Neues Marketplace-Deck wird angelegt.</span>
+					{/if}
+				</div>
+
+				{#if slugExists === false}
+					<!-- Only shown for new decks -->
+					<div class="field">
+						<label class="field-label" for="pub-title">Titel</label>
+						<input
+							id="pub-title"
+							type="text"
+							bind:value={title}
+							required
+							maxlength="200"
+							class="input"
+						/>
+					</div>
+
+					<div class="field">
+						<label class="field-label" for="pub-desc">Beschreibung (optional)</label>
+						<textarea
+							id="pub-desc"
+							bind:value={description}
+							rows="2"
+							maxlength="1000"
+							class="input"
+						></textarea>
+					</div>
+
+					<div class="field">
+						<label class="field-label" for="pub-license">Lizenz</label>
+						<select id="pub-license" bind:value={license} class="input">
+							{#each LICENSES as l}
+								<option value={l}>{l}</option>
+							{/each}
+						</select>
+					</div>
+				{/if}
+
+				<!-- Version info — always shown -->
+				<div class="version-row">
+					<div class="field">
+						<label class="field-label" for="pub-semver">Version</label>
+						<input
+							id="pub-semver"
+							type="text"
+							bind:value={semver}
+							required
+							pattern="\d+\.\d+\.\d+"
+							class="input mono"
+							style="width: 8rem"
+						/>
+					</div>
+					<div class="field" style="flex:1">
+						<label class="field-label" for="pub-changelog">Changelog (optional)</label>
+						<input
+							id="pub-changelog"
+							type="text"
+							bind:value={changelog}
+							maxlength="500"
+							placeholder="Was ist neu in dieser Version?"
+							class="input"
+						/>
+					</div>
+				</div>
+
+				<!-- Cards summary -->
+				<div class="cards-summary">
+					<span class="cards-count">{marketplaceCards.length}</span>
+					<span class="cards-label">
+						Karte{marketplaceCards.length !== 1 ? 'n' : ''} werden automatisch übernommen
+					</span>
+					<span class="cards-types">
+						{[...new Set(marketplaceCards.map((c) => c.type))].join(', ')}
+					</span>
+				</div>
+
+				{#if error}
+					<div class="error-box" role="alert">{error}</div>
+				{/if}
+
+				<div class="form-actions">
+					<button type="button" class="btn-ghost" onclick={onClose}>Abbrechen</button>
+					<button type="submit" disabled={!canSubmit} class="btn-primary">
+						{busy ? 'Veröffentliche…' : slugExists ? 'Neue Version veröffentlichen' : 'Veröffentlichen'}
+					</button>
+				</div>
+			</form>
+		{/if}
+	</div>
+</div>
+
+<style>
+	.overlay {
+		position: fixed;
+		inset: 0;
+		z-index: 50;
+		display: flex;
+		align-items: center;
+		justify-content: center;
+		background: hsl(var(--color-foreground) / 0.4);
+		backdrop-filter: blur(2px);
+		padding: 1rem;
+	}
+
+	.modal {
+		width: 100%;
+		max-width: 36rem;
+		max-height: 90vh;
+		overflow-y: auto;
+		background: hsl(var(--color-card));
+		border: 1px solid hsl(var(--color-border));
+		border-radius: 1rem;
+		padding: 1.5rem;
+		box-shadow: 0 24px 48px hsl(var(--color-foreground) / 0.2);
+		display: flex;
+		flex-direction: column;
+		gap: 1.125rem;
+	}
+
+	.modal-head {
+		display: flex;
+		align-items: flex-start;
+		justify-content: space-between;
+		gap: 1rem;
+	}
+
+	.modal-title {
+		font-size: 1.125rem;
+		font-weight: 600;
+		margin: 0;
+	}
+
+	.modal-subtitle {
+		font-size: 0.8125rem;
+		color: hsl(var(--color-muted-foreground));
+		margin: 0.125rem 0 0;
+	}
+
+	.close-btn {
+		background: none;
+		border: none;
+		font-size: 1.5rem;
+		line-height: 1;
+		color: hsl(var(--color-muted-foreground));
+		cursor: pointer;
+		padding: 0;
+		flex-shrink: 0;
+	}
+	.close-btn:hover { color: hsl(var(--color-foreground)); }
+
+	.loading-hint {
+		font-size: 0.875rem;
+		color: hsl(var(--color-muted-foreground));
+		margin: 0;
+	}
+
+	/* No-author state */
+	.no-author {
+		display: flex;
+		flex-direction: column;
+		align-items: center;
+		gap: 0.75rem;
+		padding: 1.5rem 0;
+		text-align: center;
+	}
+
+	.no-author-icon { font-size: 2rem; }
+
+	.no-author-text {
+		font-size: 0.9375rem;
+		color: hsl(var(--color-muted-foreground));
+		max-width: 22rem;
+		margin: 0;
+	}
+
+	/* Author badge */
+	.author-badge {
+		display: flex;
+		align-items: center;
+		gap: 0.5rem;
+		padding: 0.5rem 0.75rem;
+		border-radius: 0.5rem;
+		background: hsl(var(--color-success) / 0.08);
+		border: 1px solid hsl(var(--color-success) / 0.25);
+		font-size: 0.8125rem;
+		color: hsl(var(--color-foreground));
+	}
+
+	.author-dot {
+		width: 0.5rem;
+		height: 0.5rem;
+		border-radius: 50%;
+		background: hsl(var(--color-success));
+		flex-shrink: 0;
+	}
+
+	/* Form */
+	.pub-form {
+		display: flex;
+		flex-direction: column;
+		gap: 1rem;
+	}
+
+	.field {
+		display: flex;
+		flex-direction: column;
+		gap: 0.3rem;
+	}
+
+	.field-label {
+		font-size: 0.8125rem;
+		font-weight: 600;
+		color: hsl(var(--color-foreground));
+	}
+
+	.field-hint {
+		font-size: 0.75rem;
+		color: hsl(var(--color-muted-foreground));
+	}
+
+	.input {
+		border: 1px solid hsl(var(--color-border));
+		border-radius: 0.5rem;
+		background: hsl(var(--color-surface));
+		color: hsl(var(--color-foreground));
+		padding: 0.5rem 0.625rem;
+		font: inherit;
+		font-size: 0.875rem;
+		width: 100%;
+		transition: border-color 0.12s, box-shadow 0.12s;
+		resize: vertical;
+	}
+	.input:focus {
+		outline: none;
+		border-color: hsl(var(--color-primary) / 0.6);
+		box-shadow: 0 0 0 3px hsl(var(--color-primary) / 0.1);
+	}
+	.input.mono { font-family: ui-monospace, 'Cascadia Code', monospace; }
+
+	/* Slug row */
+	.slug-row {
+		display: flex;
+		align-items: center;
+		border: 1px solid hsl(var(--color-border));
+		border-radius: 0.5rem;
+		background: hsl(var(--color-surface));
+		overflow: hidden;
+		transition: border-color 0.12s, box-shadow 0.12s;
+	}
+	.slug-row:focus-within {
+		border-color: hsl(var(--color-primary) / 0.6);
+		box-shadow: 0 0 0 3px hsl(var(--color-primary) / 0.1);
+	}
+
+	.slug-prefix {
+		padding: 0.5rem 0.5rem 0.5rem 0.625rem;
+		font-size: 0.75rem;
+		color: hsl(var(--color-muted-foreground));
+		white-space: nowrap;
+		flex-shrink: 0;
+	}
+
+	.slug-input {
+		border: none;
+		border-radius: 0;
+		background: transparent;
+		padding-left: 0;
+		box-shadow: none;
+		flex: 1;
+		min-width: 0;
+	}
+	.slug-input:focus { box-shadow: none; }
+
+	.slug-status {
+		padding: 0 0.625rem;
+		font-size: 0.75rem;
+		font-weight: 600;
+		white-space: nowrap;
+		flex-shrink: 0;
+	}
+	.slug-status.checking { color: hsl(var(--color-muted-foreground)); }
+	.slug-status.exists { color: hsl(var(--color-primary)); }
+	.slug-status.new { color: hsl(var(--color-success)); }
+
+	/* Version row */
+	.version-row {
+		display: flex;
+		gap: 0.75rem;
+		align-items: flex-start;
+	}
+
+	/* Cards summary */
+	.cards-summary {
+		display: flex;
+		align-items: center;
+		gap: 0.5rem;
+		padding: 0.625rem 0.875rem;
+		border-radius: 0.5rem;
+		background: hsl(var(--color-primary) / 0.07);
+		border: 1px solid hsl(var(--color-primary) / 0.2);
+		font-size: 0.8125rem;
+	}
+
+	.cards-count {
+		font-size: 1rem;
+		font-weight: 700;
+		color: hsl(var(--color-primary));
+	}
+
+	.cards-label {
+		color: hsl(var(--color-foreground));
+	}
+
+	.cards-types {
+		margin-left: auto;
+		font-size: 0.75rem;
+		color: hsl(var(--color-muted-foreground));
+		font-family: ui-monospace, monospace;
+	}
+
+	/* Error */
+	.error-box {
+		padding: 0.625rem 0.875rem;
+		border-radius: 0.5rem;
+		background: hsl(var(--color-error) / 0.1);
+		border: 1px solid hsl(var(--color-error) / 0.4);
+		color: hsl(var(--color-error));
+		font-size: 0.875rem;
+	}
+
+	/* Actions */
+	.form-actions {
+		display: flex;
+		align-items: center;
+		justify-content: flex-end;
+		gap: 0.75rem;
+		padding-top: 0.25rem;
+	}
+
+	.btn-primary {
+		display: inline-flex;
+		align-items: center;
+		padding: 0.5rem 1.125rem;
+		border-radius: 0.5rem;
+		background: hsl(var(--color-primary));
+		color: hsl(var(--color-primary-foreground));
+		font: inherit;
+		font-size: 0.875rem;
+		font-weight: 500;
+		border: none;
+		cursor: pointer;
+		text-decoration: none;
+		transition: background-color 0.12s;
+	}
+	.btn-primary:hover:not(:disabled) { background: hsl(var(--color-primary) / 0.88); }
+	.btn-primary:disabled { opacity: 0.45; cursor: default; }
+
+	.btn-ghost {
+		background: none;
+		border: none;
+		padding: 0;
+		font: inherit;
+		font-size: 0.875rem;
+		color: hsl(var(--color-muted-foreground));
+		cursor: pointer;
+		text-decoration: none;
+	}
+	.btn-ghost:hover { color: hsl(var(--color-foreground)); }
+</style>
diff --git a/apps/web/src/routes/decks/[id]/+page.svelte b/apps/web/src/routes/decks/[id]/+page.svelte
index 9af2a36..22cc2db 100644
--- a/apps/web/src/routes/decks/[id]/+page.svelte
+++ b/apps/web/src/routes/decks/[id]/+page.svelte
@@ -12,6 +12,7 @@
 	import { t, tn } from '$lib/i18n/index.svelte.ts';
 	import CardSurface from '$lib/components/CardSurface.svelte';
 	import DeckCategoryIcon from '$lib/components/DeckCategoryIcon.svelte';
+	import PublishDeckModal from '$lib/components/marketplace/PublishDeckModal.svelte';
 	import { Image, CaretRight, DotsThree, PencilSimple, Trash } from '@mana/shared-icons';
 	import { marked } from 'marked';
 
@@ -26,6 +27,7 @@
 	let error = $state<string | null>(null);
 	let categoryOpen = $state(false);
 	let openMenuId = $state<string | null>(null);
+	let publishModalOpen = $state(false);
 
 	function toggleMenu(cardId: string, e: MouseEvent) {
 		e.preventDefault();
@@ -121,6 +123,14 @@
 			<a href="/cards/new?deck={deck.id}" class="btn-outline">
 				+ {t('deck_detail.new_card')}
 			</a>
+			<button
+				type="button"
+				class="btn-outline"
+				onclick={() => { publishModalOpen = true; }}
+				title="Deck zum Marketplace veröffentlichen"
+			>
+				↑ Veröffentlichen
+			</button>
 			{#if dueCount > 0}
 				<a href="/study/{deck.id}" class="btn-primary">
 					{t('deck_detail.study_button')} ({t('study.due_count', { n: dueCount })})
@@ -265,6 +275,15 @@
 			{/each}
 		</ul>
 	{/if}
+
+	{#if publishModalOpen && deck}
+		<PublishDeckModal
+			{deck}
+			{cards}
+			onClose={() => { publishModalOpen = false; }}
+			onPublished={(slug) => { publishModalOpen = false; goto(`/d/${slug}`); }}
+		/>
+	{/if}
 {/if}
 
 <style>