diff --git a/web/src/lib/components/MessageBody.svelte b/web/src/lib/components/MessageBody.svelte
new file mode 100644
index 0000000..816c77d
--- /dev/null
+++ b/web/src/lib/components/MessageBody.svelte
@@ -0,0 +1,262 @@
+<script lang="ts">
+	let { body, truncate }: { body: string; truncate?: number } = $props();
+
+	/**
+	 * Lightweight markdown renderer with @mentions, #channels, and URL auto-linking.
+	 * No external dependencies. Input is sanitized (HTML stripped) before processing.
+	 */
+
+	// Strip all HTML tags from raw input to prevent XSS
+	function stripHtml(text: string): string {
+		return text.replace(/<[^>]*>/g, '');
+	}
+
+	// Escape HTML special characters in text content
+	function escapeHtml(text: string): string {
+		return text
+			.replace(/&/g, '&amp;')
+			.replace(/</g, '&lt;')
+			.replace(/>/g, '&gt;')
+			.replace(/"/g, '&quot;');
+	}
+
+	// Process inline markdown: bold, italic, code, URLs, @mentions, #channels
+	function processInline(text: string): string {
+		// Inline code first (so content inside is not further processed)
+		let result = '';
+		const codeRegex = /`([^`]+)`/g;
+		let lastIndex = 0;
+		let match;
+
+		while ((match = codeRegex.exec(text)) !== null) {
+			result += processInlineNonCode(text.slice(lastIndex, match.index));
+			result += `<code class="msg-inline-code">${escapeHtml(match[1])}</code>`;
+			lastIndex = codeRegex.lastIndex;
+		}
+		result += processInlineNonCode(text.slice(lastIndex));
+		return result;
+	}
+
+	// Process inline elements that are NOT inside code spans
+	function processInlineNonCode(text: string): string {
+		let s = escapeHtml(text);
+
+		// URLs - must come before bold/italic to avoid mangling URLs with underscores
+		s = s.replace(
+			/https?:\/\/[^\s&lt;&gt;&amp;]+/g,
+			(url) => {
+				// Decode escaped HTML entities back for the href
+				const href = url.replace(/&amp;/g, '&').replace(/&lt;/g, '<').replace(/&gt;/g, '>').replace(/&quot;/g, '"');
+				return `<a href="${href}" target="_blank" rel="noopener" class="msg-link">${url}</a>`;
+			}
+		);
+
+		// Bold: **text**
+		s = s.replace(/\*\*([^*]+)\*\*/g, '<strong>$1</strong>');
+
+		// Italic: *text* (but not inside **)
+		s = s.replace(/(?<!\*)\*([^*]+)\*(?!\*)/g, '<em>$1</em>');
+
+		// @mentions
+		s = s.replace(
+			/@([\w][\w.-]*)/g,
+			'<a href="/dm/$1" class="msg-mention">@$1</a>'
+		);
+
+		// #channels
+		s = s.replace(
+			/#([\w][\w.-]*)/g,
+			'<a href="/channels/$1" class="msg-channel">$&</a>'
+		);
+
+		return s;
+	}
+
+	// Parse a full message body into HTML
+	function renderMarkdown(raw: string): string {
+		const sanitized = stripHtml(raw);
+
+		// Handle truncation on the sanitized text
+		let text = sanitized;
+		if (truncate && text.length > truncate) {
+			text = text.slice(0, truncate) + '...';
+		}
+
+		// Fenced code blocks: ```...```
+		const blocks: string[] = [];
+		const codeBlockRegex = /```(?:\w*)\n?([\s\S]*?)```/g;
+		let processed = text.replace(codeBlockRegex, (_match, code) => {
+			const idx = blocks.length;
+			blocks.push(`<pre class="msg-code-block"><code>${escapeHtml(code.replace(/\n$/, ''))}</code></pre>`);
+			return `\x00BLOCK${idx}\x00`;
+		});
+
+		// Split into paragraphs by blank lines
+		const paragraphs = processed.split(/\n{2,}/);
+		const htmlParts: string[] = [];
+
+		for (const para of paragraphs) {
+			// Check for block placeholder
+			if (/^\x00BLOCK\d+\x00$/.test(para.trim())) {
+				const idx = parseInt(para.trim().replace(/\x00BLOCK(\d+)\x00/, '$1'));
+				htmlParts.push(blocks[idx]);
+				continue;
+			}
+
+			const lines = para.split('\n');
+
+			// Check if this paragraph is a list
+			const isUnordered = lines.every(l => /^\s*[-*]\s/.test(l) || l.trim() === '');
+			const isOrdered = lines.every(l => /^\s*\d+\.\s/.test(l) || l.trim() === '');
+
+			if (isUnordered && lines.some(l => l.trim() !== '')) {
+				const items = lines
+					.filter(l => /^\s*[-*]\s/.test(l))
+					.map(l => `<li>${processInline(l.replace(/^\s*[-*]\s+/, ''))}</li>`)
+					.join('');
+				htmlParts.push(`<ul class="msg-list">${items}</ul>`);
+			} else if (isOrdered && lines.some(l => l.trim() !== '')) {
+				const items = lines
+					.filter(l => /^\s*\d+\.\s/.test(l))
+					.map(l => `<li>${processInline(l.replace(/^\s*\d+\.\s+/, ''))}</li>`)
+					.join('');
+				htmlParts.push(`<ol class="msg-list msg-list-ordered">${items}</ol>`);
+			} else {
+				// Check for headers
+				const headerMatch = para.match(/^(#{1,6})\s+(.+)$/);
+				if (headerMatch) {
+					const level = headerMatch[1].length;
+					htmlParts.push(`<h${level} class="msg-heading msg-h${level}">${processInline(headerMatch[2])}</h${level}>`);
+				} else {
+					// Regular paragraph - preserve line breaks within
+					const inlineHtml = lines
+						.map(l => {
+							// Replace block placeholders inline
+							if (/\x00BLOCK\d+\x00/.test(l)) {
+								return l.replace(/\x00BLOCK(\d+)\x00/g, (_, idx) => blocks[parseInt(idx)]);
+							}
+							return processInline(l);
+						})
+						.join('<br>');
+					htmlParts.push(`<p>${inlineHtml}</p>`);
+				}
+			}
+		}
+
+		return htmlParts.join('');
+	}
+
+	let rendered = $derived(renderMarkdown(body));
+</script>
+
+<div class="msg-body">
+	{@html rendered}
+</div>
+
+<style>
+	.msg-body {
+		/* Inherit parent text styling */
+	}
+	.msg-body :global(p) {
+		margin: 0;
+	}
+	.msg-body :global(p + p) {
+		margin-top: 0.5em;
+	}
+	.msg-body :global(strong) {
+		font-weight: 700;
+	}
+	.msg-body :global(em) {
+		font-style: italic;
+	}
+	.msg-body :global(.msg-inline-code) {
+		font-family: 'JetBrains Mono', monospace;
+		font-size: 0.85em;
+		padding: 0.15em 0.35em;
+		border-radius: 4px;
+		background-color: var(--bg-tertiary);
+		color: var(--accent-red);
+	}
+	.msg-body :global(.msg-code-block) {
+		font-family: 'JetBrains Mono', monospace;
+		font-size: 0.8em;
+		padding: 0.75em 1em;
+		border-radius: 6px;
+		background-color: var(--bg-primary);
+		border: 1px solid var(--border);
+		overflow-x: auto;
+		margin: 0.5em 0;
+		white-space: pre;
+		line-height: 1.5;
+	}
+	.msg-body :global(.msg-code-block code) {
+		background: none;
+		padding: 0;
+		color: var(--text-primary);
+	}
+	.msg-body :global(.msg-link) {
+		color: var(--text-link);
+		text-decoration: none;
+	}
+	.msg-body :global(.msg-link:hover) {
+		text-decoration: underline;
+	}
+	.msg-body :global(.msg-mention) {
+		display: inline;
+		padding: 0.1em 0.4em;
+		border-radius: 4px;
+		background-color: rgba(124, 58, 237, 0.15);
+		color: var(--accent-purple);
+		font-weight: 600;
+		font-size: 0.92em;
+		text-decoration: none;
+	}
+	.msg-body :global(.msg-mention:hover) {
+		background-color: rgba(124, 58, 237, 0.25);
+		text-decoration: none;
+	}
+	.msg-body :global(.msg-channel) {
+		display: inline;
+		padding: 0.1em 0.4em;
+		border-radius: 4px;
+		background-color: rgba(54, 197, 240, 0.15);
+		color: var(--accent-blue);
+		font-weight: 600;
+		font-size: 0.92em;
+		text-decoration: none;
+	}
+	.msg-body :global(.msg-channel:hover) {
+		background-color: rgba(54, 197, 240, 0.25);
+		text-decoration: none;
+	}
+	.msg-body :global(.msg-list) {
+		margin: 0.25em 0;
+		padding-left: 1.5em;
+		list-style-type: disc;
+	}
+	.msg-body :global(.msg-list-ordered) {
+		list-style-type: decimal;
+	}
+	.msg-body :global(.msg-list li) {
+		margin: 0.1em 0;
+	}
+	.msg-body :global(.msg-heading) {
+		font-family: 'Instrument Sans', sans-serif;
+		font-weight: 700;
+		margin: 0.4em 0 0.2em;
+	}
+	.msg-body :global(.msg-h1) {
+		font-size: 1.3em;
+	}
+	.msg-body :global(.msg-h2) {
+		font-size: 1.15em;
+	}
+	.msg-body :global(.msg-h3) {
+		font-size: 1.05em;
+	}
+	.msg-body :global(.msg-h4),
+	.msg-body :global(.msg-h5),
+	.msg-body :global(.msg-h6) {
+		font-size: 1em;
+	}
+</style>
diff --git a/web/src/lib/components/MessageList.svelte b/web/src/lib/components/MessageList.svelte
index 1c8d995..eb9875a 100644
--- a/web/src/lib/components/MessageList.svelte
+++ b/web/src/lib/components/MessageList.svelte
@@ -1,5 +1,6 @@
 <script lang="ts">
 	import { openThread } from '$lib/stores/thread';
+	import MessageBody from '$lib/components/MessageBody.svelte';
 
 	type Message = {
 		id: number;
@@ -105,7 +106,7 @@
 								<span class="badge bg-accent-yellow/20 text-accent-yellow">P{msg.priority}</span>
 							{/if}
 						</div>
-						<p class="text-sm text-text-primary/90 leading-relaxed whitespace-pre-wrap">{msg.body.length > 300 ? msg.body.slice(0, 300) + '...' : msg.body}</p>
+						<div class="text-sm text-text-primary/90 leading-relaxed"><MessageBody body={msg.body} truncate={300} /></div>
 
 						<!-- Thread link -->
 						{#if showConversationLink && msg.conversation_id}
diff --git a/web/src/lib/components/ThreadPanel.svelte b/web/src/lib/components/ThreadPanel.svelte
index c852a2c..72351ee 100644
--- a/web/src/lib/components/ThreadPanel.svelte
+++ b/web/src/lib/components/ThreadPanel.svelte
@@ -1,6 +1,7 @@
 <script lang="ts">
 	import { activeThread, closeThread } from '$lib/stores/thread';
 	import { conversations as convsApi, messages as messagesApi } from '$lib/api/client';
+	import MessageBody from '$lib/components/MessageBody.svelte';
 
 	let conversation = $state<any>(null);
 	let threadMessages = $state<any[]>([]);
@@ -162,7 +163,7 @@
 										<span class="{statusClass(msg.status)} text-[10px]">{msg.status}</span>
 									{/if}
 								</div>
-								<p class="text-xs text-text-primary/90 whitespace-pre-wrap leading-relaxed">{msg.body}</p>
+								<div class="text-xs text-text-primary/90 leading-relaxed"><MessageBody body={msg.body} /></div>
 							</div>
 						</div>
 					</div>
diff --git a/web/src/routes/channels/[name]/+page.svelte b/web/src/routes/channels/[name]/+page.svelte
index 8468d55..bda7063 100644
--- a/web/src/routes/channels/[name]/+page.svelte
+++ b/web/src/routes/channels/[name]/+page.svelte
@@ -3,6 +3,7 @@
 	import { channels as channelsApi, messages as messagesApi, agents as agentsApi } from '$lib/api/client';
 	import { openThread, closeThread } from '$lib/stores/thread';
 	import { notifications } from '$lib/stores/notifications';
+	import MessageBody from '$lib/components/MessageBody.svelte';
 
 	let channel = $state<any>(null);
 	let members = $state<any[]>([]);
@@ -268,7 +269,7 @@
 												{/if}
 												<span class="text-xs text-text-secondary">{formatTime(msg.created_at)}</span>
 											</div>
-											<p class="text-sm text-text-primary/90 leading-relaxed whitespace-pre-wrap">{msg.body}</p>
+											<div class="text-sm text-text-primary/90 leading-relaxed"><MessageBody body={msg.body} /></div>
 											{#if msg.reply_count > 0}
 												<button
 													class="mt-1 flex items-center gap-1 text-xs text-accent-blue hover:underline"
diff --git a/web/src/routes/conversations/[id]/+page.svelte b/web/src/routes/conversations/[id]/+page.svelte
index cc8306e..13005d2 100644
--- a/web/src/routes/conversations/[id]/+page.svelte
+++ b/web/src/routes/conversations/[id]/+page.svelte
@@ -1,6 +1,7 @@
 <script lang="ts">
 	import { page } from '$app/stores';
 	import { conversations as convsApi, messages as messagesApi } from '$lib/api/client';
+	import MessageBody from '$lib/components/MessageBody.svelte';
 
 	let conversation = $state<any>(null);
 	let messagesList = $state<any[]>([]);
@@ -151,7 +152,7 @@
 							{/if}
 								<span class="text-xs text-text-secondary ml-auto">{formatTime(msg.created_at)}</span>
 							</div>
-							<div class="text-sm text-text-primary/90 whitespace-pre-wrap leading-relaxed">{msg.body}</div>
+							<div class="text-sm text-text-primary/90 leading-relaxed"><MessageBody body={msg.body} /></div>
 						</div>
 					</div>
 				</div>
diff --git a/web/src/routes/dm/[name]/+page.svelte b/web/src/routes/dm/[name]/+page.svelte
index 370f889..945fe63 100644
--- a/web/src/routes/dm/[name]/+page.svelte
+++ b/web/src/routes/dm/[name]/+page.svelte
@@ -3,6 +3,7 @@
 	import { agents as agentsApi, messages as messagesApi } from '$lib/api/client';
 	import { openThread, closeThread } from '$lib/stores/thread';
 	import { notifications } from '$lib/stores/notifications';
+	import MessageBody from '$lib/components/MessageBody.svelte';
 
 	let peerAgent = $derived($page.params.name);
 	let peer = $state<any>(null);
@@ -244,7 +245,7 @@
 											<span class="text-[9px] px-1.5 py-0.5 rounded {msg.status === 'pending' ? 'bg-accent-yellow/20 text-accent-yellow' : msg.status === 'processing' ? 'bg-accent-blue/20 text-accent-blue' : 'bg-bg-tertiary text-text-secondary'}">{msg.status}</span>
 										{/if}
 									</div>
-									<p class="text-sm text-text-primary/90 leading-relaxed whitespace-pre-wrap">{msg.body}</p>
+									<div class="text-sm text-text-primary/90 leading-relaxed"><MessageBody body={msg.body} /></div>
 									{#if msg.reply_count > 0}
 										<button
 											class="mt-1 flex items-center gap-1 text-xs text-accent-blue hover:underline"