diff --git a/web/src/lib/components/TaskDetail.svelte b/web/src/lib/components/TaskDetail.svelte
new file mode 100644
index 0000000..d929ce6
--- /dev/null
+++ b/web/src/lib/components/TaskDetail.svelte
@@ -0,0 +1,765 @@
+<script>
+	/**
+	 * One task, opened.
+	 *
+	 * A drawer rather than a page: the list you came from stays visible behind it,
+	 * so ticking a sub-task off and closing lands you back where you were rather
+	 * than at the top of a re-fetched list.
+	 *
+	 * Text fields save on blur, not on every keystroke. A PATCH per character would
+	 * be forty requests for one sentence, and the last one to arrive is not
+	 * necessarily the last one sent.
+	 */
+	import { api, humanMessage } from '$lib/api.js';
+	import { app } from '$lib/stores.svelte.js';
+
+	let { task, onclose } = $props();
+
+	let content = $state('');
+	let description = $state('');
+	let priority = $state(4);
+	let dueDate = $state('');
+	let labels = $state('');
+
+	let subtasks = $state([]);
+	let comments = $state([]);
+	let attachments = $state([]);
+	let reminders = $state([]);
+
+	let newSubtask = $state('');
+	let newComment = $state('');
+	let newReminder = $state('');
+	let posting = $state(false);
+	let uploading = $state(false);
+
+	// Re-seeded whenever a different task is opened. Keyed on the id rather than on
+	// the object, so a websocket update to the same task does not throw away what
+	// somebody is typing.
+	let seededId = $state(null);
+
+	$effect(() => {
+		if (!task || seededId === task.id) return;
+		seededId = task.id;
+
+		content = task.content;
+		description = task.description ?? '';
+		priority = task.priority;
+		dueDate = task.due_date ?? '';
+		labels = (task.labels ?? []).join(', ');
+
+		subtasks = [];
+		comments = [];
+		attachments = [];
+		reminders = [];
+
+		const id = task.id;
+		api.listTasks({ parent_id: id, completed: 'include' })
+			.then((r) => id === seededId && (subtasks = r.tasks))
+			.catch(() => {});
+		api.listComments(id)
+			.then((r) => {
+				if (id !== seededId) return;
+				comments = r.comments;
+				attachments = r.attachments ?? [];
+			})
+			.catch(() => {});
+		api.listReminders(id)
+			.then((r) => id === seededId && (reminders = r.reminders))
+			.catch(() => {});
+	});
+
+	/** Sends a patch through the store, so the row behind the drawer updates too. */
+	async function save(patch) {
+		await app.update(task.id, patch);
+	}
+
+	function saveContent() {
+		const trimmed = content.trim();
+		if (!trimmed || trimmed === task.content) {
+			content = task.content;
+			return;
+		}
+		save({ content: trimmed });
+	}
+
+	function saveDescription() {
+		if (description === (task.description ?? '')) return;
+		save({ description });
+	}
+
+	function saveLabels() {
+		const list = labels
+			.split(',')
+			.map((l) => l.trim())
+			.filter(Boolean);
+		if (list.join() === (task.labels ?? []).join()) return;
+		save({ labels: list });
+	}
+
+	// --- sub-tasks ----------------------------------------------------------------
+
+	async function addSubtask(event) {
+		event.preventDefault();
+		const text = newSubtask.trim();
+		if (!text) return;
+		newSubtask = '';
+		try {
+			const created = await api.createTask({
+				content: text,
+				project_id: task.project_id,
+				parent_id: task.id
+			});
+			subtasks = [...subtasks, created];
+		} catch (e) {
+			app.toast(humanMessage(e));
+		}
+	}
+
+	async function toggleSubtask(subtask) {
+		const previous = subtasks;
+		subtasks = subtasks.map((s) =>
+			s.id === subtask.id ? { ...s, completed: !s.completed } : s
+		);
+		try {
+			const updated = subtask.completed
+				? await api.reopenTask(subtask.id)
+				: await api.completeTask(subtask.id);
+			subtasks = subtasks.map((s) => (s.id === updated.id ? updated : s));
+		} catch (e) {
+			subtasks = previous;
+			app.toast(humanMessage(e));
+		}
+	}
+
+	async function removeSubtask(subtask) {
+		const previous = subtasks;
+		subtasks = subtasks.filter((s) => s.id !== subtask.id);
+		try {
+			await api.deleteTask(subtask.id);
+		} catch (e) {
+			subtasks = previous;
+			app.toast(humanMessage(e));
+		}
+	}
+
+	// --- comments and files ---------------------------------------------------------
+
+	async function addComment(event) {
+		event.preventDefault();
+		const body = newComment.trim();
+		if (!body) return;
+		posting = true;
+		try {
+			const created = await api.createComment(task.id, body);
+			comments = [...comments, created];
+			newComment = '';
+		} catch (e) {
+			app.toast(e.fields?.body ?? humanMessage(e));
+		} finally {
+			posting = false;
+		}
+	}
+
+	async function removeComment(comment) {
+		if (!confirm('Slet kommentaren?')) return;
+		const previous = comments;
+		comments = comments.filter((c) => c.id !== comment.id);
+		try {
+			await api.deleteComment(comment.id);
+		} catch (e) {
+			comments = previous;
+			app.toast(humanMessage(e));
+		}
+	}
+
+	async function upload(event) {
+		const file = event.target.files?.[0];
+		if (!file) return;
+		event.target.value = '';
+
+		uploading = true;
+		try {
+			attachments = [...attachments, await api.uploadAttachment(task.id, file)];
+		} catch (e) {
+			app.toast(e.fields?.file ?? humanMessage(e));
+		} finally {
+			uploading = false;
+		}
+	}
+
+	async function removeAttachment(attachment) {
+		const previous = attachments;
+		attachments = attachments.filter((a) => a.id !== attachment.id);
+		try {
+			await api.deleteAttachment(attachment.id);
+		} catch (e) {
+			attachments = previous;
+			app.toast(humanMessage(e));
+		}
+	}
+
+	// --- reminders --------------------------------------------------------------------
+
+	async function addReminder(event) {
+		event.preventDefault();
+		if (!newReminder) return;
+		try {
+			// The input gives local wall-clock time; the API wants an instant.
+			const created = await api.createReminder(task.id, {
+				remind_at: new Date(newReminder).toISOString()
+			});
+			reminders = [...reminders, created];
+			newReminder = '';
+		} catch (e) {
+			app.toast(e.fields?.remind_at ?? humanMessage(e));
+		}
+	}
+
+	async function removeReminder(reminder) {
+		const previous = reminders;
+		reminders = reminders.filter((r) => r.id !== reminder.id);
+		try {
+			await api.deleteReminder(reminder.id);
+		} catch (e) {
+			reminders = previous;
+			app.toast(humanMessage(e));
+		}
+	}
+
+	function onkeydown(event) {
+		if (event.key === 'Escape') onclose?.();
+	}
+
+	const kb = (bytes) =>
+		bytes < 1024 * 1024
+			? `${Math.max(1, Math.round(bytes / 1024))} kB`
+			: `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
+
+	const stamp = (iso) =>
+		new Date(iso).toLocaleString('da-DK', {
+			day: 'numeric',
+			month: 'short',
+			hour: '2-digit',
+			minute: '2-digit'
+		});
+</script>
+
+<svelte:window {onkeydown} />
+
+<!-- svelte-ignore a11y_click_events_have_key_events, a11y_no_noninteractive_element_interactions -->
+<div class="scrim" onclick={onclose} role="presentation"></div>
+
+<aside class="drawer" aria-label="Opgave">
+	<header>
+		<button class="close" onclick={onclose} aria-label="Luk">
+			<svg viewBox="0 0 24 24" aria-hidden="true">
+				<path d="M6 6l12 12M18 6L6 18" />
+			</svg>
+		</button>
+	</header>
+
+	<div class="scroll">
+		<div class="field">
+			<!-- svelte-ignore a11y_autofocus -->
+			<input
+				class="title"
+				bind:value={content}
+				onblur={saveContent}
+				aria-label="Opgavens tekst"
+			/>
+		</div>
+
+		<div class="field">
+			<label for="description">Beskrivelse</label>
+			<textarea
+				id="description"
+				rows="4"
+				bind:value={description}
+				onblur={saveDescription}
+				placeholder="Detaljer, links, hvad der skal huskes"
+			></textarea>
+		</div>
+
+		<div class="grid">
+			<div class="field">
+				<label for="priority">Prioritet</label>
+				<select
+					id="priority"
+					bind:value={priority}
+					onchange={() => save({ priority: Number(priority) })}
+				>
+					<option value={1}>P1 — haster</option>
+					<option value={2}>P2</option>
+					<option value={3}>P3</option>
+					<option value={4}>Ingen</option>
+				</select>
+			</div>
+
+			<div class="field">
+				<label for="due">Forfalder</label>
+				<input
+					id="due"
+					type="date"
+					bind:value={dueDate}
+					onchange={() => save({ due_date: dueDate })}
+				/>
+			</div>
+		</div>
+
+		<div class="field">
+			<label for="labels">Etiketter</label>
+			<input
+				id="labels"
+				bind:value={labels}
+				onblur={saveLabels}
+				placeholder="adskilt af komma"
+			/>
+		</div>
+
+		{#if task.recurrence_text}
+			<p class="repeats">Gentages {task.recurrence_text}.</p>
+		{/if}
+
+		<section>
+			<h3>Undertasks</h3>
+
+			{#each subtasks as subtask (subtask.id)}
+				<div class="subtask" class:done={subtask.completed}>
+					<button
+						class="check"
+						class:checked={subtask.completed}
+						onclick={() => toggleSubtask(subtask)}
+						aria-label={subtask.completed ? 'Genåbn' : 'Markér som færdig'}
+					>
+						<svg viewBox="0 0 24 24" aria-hidden="true">
+							<path d="M6 12.5l4 4 8-8.5" />
+						</svg>
+					</button>
+					<span class="subtask-text">{subtask.content}</span>
+					<button class="remove" onclick={() => removeSubtask(subtask)} aria-label="Slet">
+						×
+					</button>
+				</div>
+			{/each}
+
+			<form onsubmit={addSubtask}>
+				<input bind:value={newSubtask} placeholder="Tilføj en undertask" aria-label="Ny undertask" />
+			</form>
+		</section>
+
+		<section>
+			<h3>Filer</h3>
+
+			{#each attachments as attachment (attachment.id)}
+				<div class="file">
+					<!-- Always a download, never rendered inline: an uploaded SVG shown
+					     in place would run its own script on this origin. -->
+					<a href={attachment.url} download={attachment.filename}>{attachment.filename}</a>
+					<span class="size">{kb(attachment.size)}</span>
+					<button class="remove" onclick={() => removeAttachment(attachment)} aria-label="Slet">
+						×
+					</button>
+				</div>
+			{/each}
+
+			<label class="upload">
+				<input type="file" onchange={upload} disabled={uploading} />
+				<span>{uploading ? 'Lægger op …' : 'Vedhæft en fil'}</span>
+			</label>
+		</section>
+
+		<section>
+			<h3>Påmindelser</h3>
+
+			{#each reminders as reminder (reminder.id)}
+				<div class="reminder">
+					<span>{reminder.remind_at ? stamp(reminder.remind_at) : `${reminder.offset_min} min.`}</span>
+					{#if reminder.sent}<span class="sent">sendt</span>{/if}
+					<button class="remove" onclick={() => removeReminder(reminder)} aria-label="Slet">
+						×
+					</button>
+				</div>
+			{/each}
+
+			<form onsubmit={addReminder}>
+				<input
+					type="datetime-local"
+					bind:value={newReminder}
+					aria-label="Ny påmindelse"
+				/>
+				<button class="add" type="submit">Tilføj</button>
+			</form>
+		</section>
+
+		<section>
+			<h3>Kommentarer</h3>
+
+			{#each comments as comment (comment.id)}
+				<article class="comment">
+					<span class="avatar" style="background: {comment.user_color}">
+						{comment.user_name?.[0]?.toUpperCase() ?? '?'}
+					</span>
+					<div class="said">
+						<span class="who">
+							{comment.user_name}
+							<span class="when">{stamp(comment.created_at)}</span>
+						</span>
+						<p>{comment.body}</p>
+						{#each comment.attachments ?? [] as attachment (attachment.id)}
+							<a class="inline-file" href={attachment.url} download={attachment.filename}>
+								{attachment.filename}
+							</a>
+						{/each}
+					</div>
+					{#if comment.user_id === app.user?.id}
+						<button class="remove" onclick={() => removeComment(comment)} aria-label="Slet">
+							×
+						</button>
+					{/if}
+				</article>
+			{/each}
+
+			<form onsubmit={addComment}>
+				<textarea
+					rows="2"
+					bind:value={newComment}
+					placeholder="Skriv en kommentar"
+					aria-label="Ny kommentar"
+				></textarea>
+				<button class="add" type="submit" disabled={posting}>Skriv</button>
+			</form>
+		</section>
+	</div>
+</aside>
+
+<style>
+	.scrim {
+		position: fixed;
+		inset: 0;
+		background: rgb(0 0 0 / 0.4);
+		z-index: 70;
+	}
+
+	.drawer {
+		position: fixed;
+		inset: 0 0 0 auto;
+		width: min(480px, 100vw);
+		z-index: 80;
+		display: flex;
+		flex-direction: column;
+		background: var(--ground);
+		border-left: 1px solid var(--line);
+		box-shadow: var(--shadow-lg);
+		animation: slide var(--medium) var(--ease-out);
+	}
+
+	@keyframes slide {
+		from {
+			transform: translateX(16px);
+			opacity: 0;
+		}
+	}
+
+	header {
+		display: flex;
+		justify-content: flex-end;
+		padding: var(--s3) var(--s4);
+		border-bottom: 1px solid var(--line);
+		flex: none;
+	}
+
+	.close {
+		width: 28px;
+		height: 28px;
+		display: grid;
+		place-items: center;
+		border-radius: var(--radius);
+		color: var(--ink-muted);
+	}
+
+	.close:hover {
+		color: var(--ink);
+		background: var(--surface);
+	}
+
+	.close svg {
+		width: 16px;
+		height: 16px;
+		fill: none;
+		stroke: currentColor;
+		stroke-width: 1.75;
+		stroke-linecap: round;
+	}
+
+	.scroll {
+		flex: 1;
+		overflow-y: auto;
+		overscroll-behavior: contain;
+		padding: var(--s4) var(--s4) var(--s8);
+		display: flex;
+		flex-direction: column;
+		gap: var(--s4);
+		padding-bottom: max(var(--s8), env(safe-area-inset-bottom));
+	}
+
+	.field {
+		display: flex;
+		flex-direction: column;
+		gap: var(--s2);
+	}
+
+	label {
+		font-size: var(--text-xs);
+		text-transform: uppercase;
+		letter-spacing: 0.06em;
+		color: var(--ink-faint);
+	}
+
+	input,
+	textarea,
+	select {
+		width: 100%;
+		padding: var(--s2) var(--s3);
+		background: var(--surface);
+		border: 1px solid var(--line);
+		border-radius: var(--radius);
+		font-size: var(--text-sm);
+		outline: none;
+		transition: border-color var(--fast) var(--ease);
+	}
+
+	input:focus,
+	textarea:focus,
+	select:focus {
+		border-color: var(--accent);
+	}
+
+	textarea {
+		resize: vertical;
+		font-family: inherit;
+		line-height: 1.5;
+	}
+
+	/* The title is the one field that should not look like a field until you are in
+	   it — it is a heading that happens to be editable. */
+	.title {
+		font-size: var(--text-lg);
+		font-weight: 560;
+		letter-spacing: -0.015em;
+		background: transparent;
+		border-color: transparent;
+		padding-left: 0;
+	}
+
+	.title:hover {
+		border-color: var(--line);
+		padding-left: var(--s3);
+	}
+
+	.title:focus {
+		background: var(--surface);
+		padding-left: var(--s3);
+	}
+
+	.grid {
+		display: grid;
+		grid-template-columns: 1fr 1fr;
+		gap: var(--s3);
+	}
+
+	.repeats {
+		margin: 0;
+		font-size: var(--text-sm);
+		color: var(--ink-muted);
+	}
+
+	section {
+		display: flex;
+		flex-direction: column;
+		gap: var(--s2);
+		padding-top: var(--s3);
+		border-top: 1px solid var(--line);
+	}
+
+	h3 {
+		font-size: var(--text-xs);
+		text-transform: uppercase;
+		letter-spacing: 0.06em;
+		color: var(--ink-faint);
+		font-weight: 560;
+	}
+
+	.subtask,
+	.file,
+	.reminder {
+		display: flex;
+		align-items: center;
+		gap: var(--s2);
+		font-size: var(--text-sm);
+	}
+
+	.subtask-text {
+		flex: 1;
+		min-width: 0;
+		overflow-wrap: anywhere;
+	}
+
+	.subtask.done .subtask-text {
+		color: var(--ink-faint);
+		text-decoration: line-through;
+	}
+
+	.check {
+		flex: none;
+		width: 16px;
+		height: 16px;
+		border: 1.5px solid var(--line-strong);
+		border-radius: var(--radius-full);
+		display: grid;
+		place-items: center;
+		transition:
+			background var(--fast) var(--ease),
+			border-color var(--fast) var(--ease);
+	}
+
+	.check:hover {
+		border-color: var(--accent);
+	}
+
+	.check.checked {
+		background: var(--accent);
+		border-color: var(--accent);
+	}
+
+	.check svg {
+		width: 11px;
+		height: 11px;
+		fill: none;
+		stroke: var(--accent-ink);
+		stroke-width: 3;
+		stroke-linecap: round;
+		stroke-linejoin: round;
+	}
+
+	.file a,
+	.inline-file {
+		color: var(--accent);
+		text-decoration: none;
+		overflow-wrap: anywhere;
+	}
+
+	.file a:hover,
+	.inline-file:hover {
+		text-decoration: underline;
+	}
+
+	.file a {
+		flex: 1;
+		min-width: 0;
+	}
+
+	.size,
+	.sent,
+	.when {
+		font-size: var(--text-xs);
+		color: var(--ink-faint);
+	}
+
+	.reminder span:first-child {
+		flex: 1;
+	}
+
+	.remove {
+		flex: none;
+		width: 20px;
+		height: 20px;
+		border-radius: var(--radius-sm);
+		color: var(--ink-faint);
+		line-height: 1;
+	}
+
+	.remove:hover {
+		color: var(--danger);
+		background: var(--danger-sunken);
+	}
+
+	.upload {
+		font-size: var(--text-sm);
+		color: var(--accent);
+		cursor: pointer;
+		text-transform: none;
+		letter-spacing: normal;
+	}
+
+	.upload input {
+		display: none;
+	}
+
+	form {
+		display: flex;
+		gap: var(--s2);
+		align-items: flex-start;
+		margin-top: var(--s1);
+	}
+
+	.add {
+		flex: none;
+		padding: var(--s2) var(--s3);
+		background: var(--accent);
+		color: var(--accent-ink);
+		border-radius: var(--radius);
+		font-size: var(--text-sm);
+	}
+
+	.add:disabled {
+		opacity: 0.5;
+	}
+
+	.comment {
+		display: flex;
+		gap: var(--s2);
+		align-items: flex-start;
+		padding: var(--s2) 0;
+	}
+
+	.avatar {
+		width: 22px;
+		height: 22px;
+		border-radius: var(--radius-full);
+		display: grid;
+		place-items: center;
+		font-size: var(--text-xs);
+		font-weight: 560;
+		color: #fff;
+		flex: none;
+	}
+
+	.said {
+		flex: 1;
+		min-width: 0;
+		display: flex;
+		flex-direction: column;
+		gap: 2px;
+	}
+
+	.who {
+		font-size: var(--text-xs);
+		color: var(--ink-muted);
+		display: flex;
+		gap: var(--s2);
+	}
+
+	.said p {
+		margin: 0;
+		font-size: var(--text-sm);
+		white-space: pre-wrap;
+		overflow-wrap: anywhere;
+	}
+
+	@media (max-width: 560px) {
+		.drawer {
+			width: 100vw;
+			border-left: 0;
+		}
+	}
+</style>
diff --git a/web/src/lib/components/TaskRow.svelte b/web/src/lib/components/TaskRow.svelte
index 7031fb3..4b71f3f 100644
--- a/web/src/lib/components/TaskRow.svelte
+++ b/web/src/lib/components/TaskRow.svelte
@@ -72,7 +72,9 @@
 		</svg>
 	</button>
 
-	<button class="body" onclick={() => onedit?.(task)}>
+	<!-- Opening the detail drawer is the default. `onedit` is for the callers that
+	     want the click to mean something else. -->
+	<button class="body" onclick={() => (onedit ? onedit(task) : app.openDetail(task.id))}>
 		<span class="content">{task.content}</span>
 
 		{#if task.description}
diff --git a/web/src/routes/+layout.svelte b/web/src/routes/+layout.svelte
index ee94f31..7ba6b35 100644
--- a/web/src/routes/+layout.svelte
+++ b/web/src/routes/+layout.svelte
@@ -6,6 +6,7 @@
 	import Sidebar from '$lib/components/Sidebar.svelte';
 	import CommandPalette from '$lib/components/CommandPalette.svelte';
 	import SignIn from '$lib/components/SignIn.svelte';
+	import TaskDetail from '$lib/components/TaskDetail.svelte';
 
 	let { children } = $props();
 
@@ -34,6 +35,9 @@
 			return;
 		}
 		if (typing || event.metaKey || event.ctrlKey || event.altKey) return;
+		// The navigation shortcuts are for the list. With a task open, "t" means the
+		// letter t — the drawer is a place you are, not a place you pass through.
+		if (app.detailId) return;
 
 		switch (event.key) {
 			case 'q':
@@ -111,6 +115,12 @@
 
 	<CommandPalette bind:open={paletteOpen} />
 
+	<!-- Mounted here rather than in each view, so a task opens the same way from
+	     Today, a project, a label or a saved filter. -->
+	{#if app.detailTask}
+		<TaskDetail task={app.detailTask} onclose={() => app.closeDetail()} />
+	{/if}
+
 	<!-- Toasts are for things that failed after the interface already said they
 	     had succeeded. Nothing else earns an interruption. -->
 	<div class="toasts" role="status" aria-live="polite">